Final Report Summary - CAPSOL (Design Technologies for Multi-scale Innovation and Integration in Post-Combustion CO2 Capture: From Molecules to Unit Operations and Integrated Plants)
Executive Summary:
Executive Summary
Power generation world-wide mainly depends on the combustion of fossil fuels. Available capture technologies are predominantly based on the use of intermediate materials, namely solvents that enhance the separation efficiency by selectively dissolving CO2. Amine-based organic compounds are among the most common solvents employed in the widely utilized chemical absorption process. The globally observed preference towards solvent-based absorption is largely because the technology is well established, the conditions for both absorption and solvent regeneration (desorption) are mild and relatively easy to meet and the process can be easily retrofitted onto existing plants. A major downside of absorption/desorption is the increased energy required for solvent regeneration. This results in high capture costs, hence there is a lack of motivation by the industry to adopt this technology.
CAPSOL project employed a truly innovative and holistic approach for the improvement of the current state-of-the-art in solvent based CO2 capture technologies. The approach aimed at enhancing the sustainability features of the entire process, and reducing the overall annualized costs through higher separation efficiency and better integration solutions. In order to achieve the final goal, CAPSOL project developed novel methods and techniques at multiple levels associated with the CO2 capture system.
CAPSOL initially targeted the molecular level, where new thermodynamic models of transferable parameters enabled the utilization of group contribution methods within a computer aided molecular design framework. The outcome was the identification of solvents and solvent blends of increased affinity towards CO2, reduced regeneration energy needs and environmentally benign characteristics.
CAPSOL developments resulted in a complete suite of process models for the absorption and desorption units or variable resolution utilized in the optimal design of flowsheet configurations of reduced capital and operating costs as well as the design of highly performing packing materials with extremely low pressure drop and adequate separation efficiency.
Major industrial case studies in the area of power generation as well as materials production have been thoroughly analyzed and studied employing CAPSOL technology in solvent selection, process design optimization, equipment design manufacturing, and heat integration options. The outcome provided strong evidence that the CAPSOL technology is a viable and highly competitive alternative to the current state-of-the-art in CO2 capture.
Finally, a pilot plant scale CO2 capture system has been set in operation in order to perform sensible experiments that prove the feasibility and highlight the practicality of the CAPSOL solvent-equipment combination.
Overall, the CAPSOL technology offers definitely a superior solution than the benchmark monoethanolamine (MEA) capture plant for lignite and coal power plants, as well as quicklime production units and achieves a comparative performance for the gas fired power plants.
Project Context and Objectives:
CAPSOL Project Context and Main Objectives
The efficient capture of CO2 is reasonably regarded as one of the grand challenges for the 21st century [1], considering that a single coal-fired plant may emit up to 25 million tons of post-combustion CO2 per year [2]. Available capture technologies are predominantly based on the use of intermediate materials, namely solvents that enhance the separation efficiency by selectively dissolving CO2 [3]. Amine-based organic compounds are among the most common solvents employed in the widely utilized chemical absorption process. The globally observed preference towards solvent-based absorption is largely because the technology is well established, the conditions for both absorption and solvent regeneration are relatively easy to meet and the process can be easily retrofitted onto existing plants [4]. Major downsides involve the increased energy required for solvent regeneration, environmental aspects associated with the toxicity of the solvent and solvent derivatives, the presence of contaminants that affect the solvent performance and lead to solvent degradation and the corrosion of equipment caused by the solvent itself.
Clearly, such shortcomings require significant advances in solvent performance, supported by the additional introduction of considerable improvements in the overall process systems that emit and capture CO2. Despite previously intense research effort in this direction, solvent-based absorption processes are reported to introduce a cost penalty of over 40% to the operation of the plant [2]. Approximately 70% of these costs are due to the use of thermal separation processes for solvent regeneration [4]. Such estimates bring the capture cost in the range of $52-89 (€36-62)/ton (Note: The original prices reported in [5] are $45-65 (€ 31-45)/ton of CO2 for a coal-fired power plant with a capacity of 900-300 MW in 2004. The above prices correspond to 2011 rates in U.S. dollars accounting for inflation and transformed into € using recent exchange rates) of CO2 [5], which is well above the current trading price (at €16.5 on 24-03-2011).The planned carbon tax in the UK is £16 (€18) in 2013 and £30 (€34) in 2020 (based on 2009 prices) [6]. Therefore, there is a lack of economic incentive in the industry to capture CO2 at the current high cost. A new technology towards breakthrough innovation in solvent based post-combustion CO2 capture for enhanced energy efficiency, improved cost effectiveness and increased process sustainability and environmental benefits is developed. Advances in the identification of highly performing solvents and solvent blends in CO2 absorption, the design of innovative separation equipment internals, and the development of optimal process configurations enable cost reductions of at least 20-30% per ton of CO2 captured. Such achievement can have a tremendous impact in several industrial applications such as gas-fired, coal-fired, and lignite-fired power plants as well as and quick-lime production plants where solvent based post-combustion CO2 absorption can become a viable solution.
The CAPSOL project adopts a holistic approach towards the fulfillment of the outlined goals accomplished through research and development at multiple levels within an integrated framework.
At the molecular level, the use of computer aided molecular design tools supported by accurate and adequately validated thermodynamic models enables the exhaustive investigation of the performance of multiple solvents and solvent blends in post-combustion CO2 absorption processes. The solvent blends are systematically assessed and rank-ordered against their performance towards the satisfaction of relevant process, economic, operability and sustainability criteria. The optimal solvents and solvent blends are expected to exhibit significantly better characteristics than currently used solvents in terms of energy requirements and overall environmental impact.
At the unit operations level, the design of innovative process configurations and column internals that are specifically tailored for the employed solvents enhance the efficiency of the absorption based separation. Advanced modeling and optimization tools in conjunction with thorough experimental procedures ensure the achievement of high mass transfer rates and optimal flow patterns.
At the plant level, the comprehensive analysis of the interactions among an existing power plant and the added solvent based post-combustion CO2 capture unit enables the optimal allocation of resources for improved energy savings and the efficient integration of the new CO2 capture process components. Several industrial applications in power production and chemicals manufacture are scheduled for comprehensive study, analysis, and evaluation thus resolving all related technical and engineering issues.
Therefore CAPSOL aims to address these challenges by seeking:
• Solvents and solvent blends of increased affinity towards CO2, reduced regeneration energy needs and environmentally benign characteristics,
• Absorption/ desorption configurations and packing materials of reduced capital cost, supporting operating conditions that facilitate the solvent-CO2 reaction and subsequent CO2 release.
• Improvements in CO2 emitting plants to facilitate the optimal integration with the capture units.
The targeted developments can have a tremendous impact in several industrial applications such as gas-fired, coal-fired, and lignite-fired power plants as well as quick-lime production plants where solvent based post-combustion CO2 absorption/desorption can become a viable solution.
Scientific Objectives
The above targets are approached through the use of advanced computer-aided methods and tools supporting the fast, cost-efficient, automated and accurate identification of potentially useful capture solvents and process systems. Few resulting solvents and process operating conditions indicating high performance are then verified in focused pilot plant experiments. The utilization of such methods and tools requires:
• The development of property predictive methods in the form of advanced thermodynamic models able to capture and model the highly non-ideal solvent-CO2-water interactions
• The development and implementation of computer-aided molecular design (CAMD) methods to investigate a very large number of potential CO2 capture solvent candidates in terms of thermodynamic, kinetic and sustainability properties.
• The development of conceptual and rigorous process models able to efficiently capture different solvent process interactions both at the level of absorption/desorption flowsheets and column packing materials.
• The development and utilization of systematic process integration and optimization tools for the investigation of overall cost-saving opportunities in CO2 emitting plant complexes including waste heat recovery and efficient resources management.
Technological Objectives
The scientific objectives facilitates in the achievement of the following technological objectives:
1) Develop optimally designed novel solvents, blends and absorption/desorption flowsheets that:
• Result in much less energy requirements compared to a 30 wt % MEA process ,
• Combine superior sustainability (e.g. environmental, safety etc.) properties, translating to a significant improvement in the eco-indicator and in the SHE (Safety-Health-Environmental) hazard assessment indicator.
• Facilitate minimum sensitivity to process variations and disturbances (e.g. impurities),
• Enable efficient operation under different pressure/temperature conditions (e.g. high pressure desorption).
• Resolve issues such as contaminants, degradation, removal of decomposition products, compression of CO2, water balance etc. with high efficiency.
2) Develop optimally designed absorption/desorption equipment that:
• Enables large reductions in the capital and operating expenses compared to a 30 wt % MEA process,
• Incorporates significant improvements in column packings including new structural (e.g. size, geometry etc.) and operating (e.g. flow, pressure drop, mass transfer etc.). characteristics of optimum performance that enable a reduction in the required energy.
• Maintain conditions that efficiently eliminate flooding, channelling, entrainment and foaming.
3) Integrate solvent-process CO2 capture plants with optimally retrofitted CO2 emitting plants including a supercritical lignite fired steam power plant, a modern supercritical hard-coal fired power plant, a natural gas fired combined cycle plant and a quicklime plant aiming to:
• Reduce the overall pre- and post-combustion process costs.
• Accomplish the targeted reductions by implementing methods for optimum plant-wide design and operation (e.g. total-site integration etc.) aiming at the utilisation of the cheapest waste heat available on the sites (e.g. condensing turbine outlet for power plants and industrial plants, as well as excess low-pressure steam for some industrial plants).
4) Pilot plant testing of the CAPSOL technology under operating condition encountered in practical applications ensures process stability and consistency.
References
[1] D’Alessandro D.M. Smit B., Long R.J. (2010), Angew. Chem. Int. Ed., 49, 6058-6082.
[2] ScienceDaily (2007), http://www.sciencedaily.com/releases/2007/11/071114163448.htm
[3] Mac Dowell N., Florin N., Buchard A., Hallett J., Galindo A., Jackson G., Adjiman C.S. Williams C.K. Shah N., Fennell P. (2010), Ener. Env. Sci., DOI: 10.1039/c004106h 3, 1645-1669
[4] Aaron D., Tsouris C. (2005), 40 (1), 3321-348.
[5] Klemes J., Bulatov I., Cockerill T. (2007), Comp. Chem. Eng., 31 (5-6), 445-455.
[6] Airlie, C., Carr, M. (2011), EU Carbon Falls as U.K. Tax Pushes Costs Above Osborne’s ‘Floor’, available in: http://www.bloomberg.com/news/2011-03-24/u-k-s-new-carbon-tax-is-higher-than-assumed-citigroup-says.html
Project Results:
CAPSOL Main Scientific and Technological Results
Molecular level advances
CAPSOL technology has approached the solution to the efficient CO2 capture process through advancements at various levels. At the molecular level, CAPSOL developed innovative computer aided molecular design based procedures supported by accurate and adequately validated thermodynamic models in order to enable the exhaustive investigation of the performance of multiple solvents and solvent blends in post-combustion CO2 absorption processes. The developments in thermodynamic modeling via group contribution methods and in computer aided molecular design tools for CO2 capture processes are presented.
Thermodynamic Models
In solvent design where a large number of molecular candidates needs to be assessed, group contribution (GC) approaches are an ideal tool. The molecules are deconstructed into distinct functional groups that characterize their chemical composition. The underlying assumption of such an approach is that these groups give rise to the same thermodynamic contribution independently of the molecule in which they appear. Once the parameters for a group have been determined via regression to experimental data then this group can be used as a building block to form a molecule. With appropriate use of the group contribution method the properties of the system of interest can be obtained even in cases where the thermodynamic behavior might be unknown but the parameters of the groups composing the system’s molecules are known. In this sense, group contribution methods are essentially predictive, since there is only a dependency on experimental data at the early stage of obtaining the group parameters from a set of selected systems (Figure 1).
A significant breakthrough in thermodynamic property modeling was made by showing for the first time that it is possible to develop a group contribution approach to represent the challenging phase and chemical equilibrium of CO2 + water + alkanolamine mixtures at different temperatures and pressures. This was achieved by proposing the use of implicit reaction models (i.e. by representing the reaction products via association sites) within the framework of the Stochastic Associating Fluid Theory with square well potentials or SAFT-γ SW equation of state. The concept of second-order groups was introduced for the first time in a SAFT-type group contribution equation of state to tackle the multifunctional nature of capture solvents. A large number of basic groups were derived. These form the essential building blocks for solvent design.
The quality of the models obtained with the novel group contribution models has been strictly verified through the comparison of the model predictions with experimental data obtained from literature or produced during the CAPSOL project. This demonstrates for the first time that the concept of implicit-models, initially developed in the context of molecular models, which consider the reaction products as neutral aggregates, can successfully be transferred to the group contribution framework; it can thus provide the basis for a fully predictive approach to the design of novel solvents for carbon capture. Implicit models also assist enormously the simulation of complex CO2 separation units. They greatly facilitate the modeling of a complex reaction mechanism in the column without the need for individual material balances for all intermediate molecular or electrolyte species that appear.
A carefully designed experimental schedule has been executed within the CAPSOL project in order to generate additional experimental data for targeted solvents that showed good potential in increasing the separation efficiency in CO2 capture units. Equilibrium solubility of CO2 in aqueous solutions of amines and amine blends measurements have been performed in a small scale absorption column equipped with packing material. The experiments justified the major trends in the behavior of the amine solutions and especially those consisted of a mixture of amines.
Such promising results have been utilized to develop a predictive framework to model (i) strong electrolytes with SAFT-γ SW and (ii) weak electrolytes with SAFT-γ SW. The treatment of weak and non-spherical electrolytes required new theoretical developments, which were implemented in the SAFT-γ SW software to create SAFT-γE. Explicit models consider the reaction products as independent ionic species. A procedure for the derivation of explicit-product models which makes use of the predictive capabilities of the implicit-product models developed to date has been set in place. In particular, reliable speciation data are generated as a basis for the modeling of reaction equilibrium. In other words, the strategy is a two-step approach to solvent selection, in which implicit-product models are first used to identify promising solvent candidates, and the best options are then investigated using explicit-product models that provide a more detailed description of mixture behavior, and of the performance of the capture process. In this regard a new version of the theory has been presented, the SAFT-γE EoS. This new EoS also takes into account electrostatic interactions, and is therefore capable of explicitly describing the ionic species obtained as reaction products in aqueous mixtures of alkanolamines and carbon dioxide.
Solvent Selection Methodology
A Computer Aided Molecular Design (CAMD) framework is developed which is subsequently used to design and select novel solvents. Intense research efforts reported in recent years are predominantly based on lab and pilot-scale experiments to select solvents which may potentially improve the overall performance of absorption/desorption CO2 capture. However, this is very challenging due to a) the highly non-ideal solvent-CO2-water chemical interactions, b) the countless combinations of potential capture solvent and blend candidates, and c) the need for combined consideration of numerous thermodynamic, kinetic and sustainability properties as performance criteria prior to selecting solvents with optimum capture features. CAMD can help address these challenges and have been successful in supporting the synthesis of molecules with desired physical, chemical and environmental properties in non-CO2 separations. Despite extensive developments in CAMD methods, few recent works reported before CAPSOL their utilization in the design of CO2 capture solvents or mixtures for chemical and physical absorption using the Statistical Associating Fluid Theory with potentials of Variable Range (SAFT-VR) and for physical absorption using the Perturbed Chain Polar Statistical Associating Fluid Theory (PCP-SAFT). While these approaches enable an accurate and reliable determination of solvent-process vapour-liquid equilibria, the set of few solvents screened to date will be further expanded as research efforts extend the rigorous predictive capabilities of SAFT-based models towards additional molecular structures.
In CAPSOL, the use of an optimization-based CAMD method whose steps are shown in the schematic of Figure 2 is employed to select post-combustion CO2 capture solvents of optimum performance in molecular and mixture properties associated with thermodynamics, kinetics and sustainability. For the first time in published literature numerous properties were considered as performance criteria reflecting solvent characteristics based on thermodynamic (e.g. vapor pressure, CO2 solubility etc.), kinetic (solvent basicity, steric hindrance etc.) and sustainability (e.g. health and safety hazard, life cycle assessment etc.) behavior. The simultaneous consideration of properties selected to capture the molecular chemistry effects on the absorption/desorption process compensates for the utilization of simpler models and ensures the selection of fewer but more effective solvents. Different functionalities of the employed CAMD method were used both to design optimum, novel molecular structures and to screen a dataset of commercially available amine solvents suitable for CO2 capture. Several models were considered simultaneously for the prediction of the properties used as solvent performance criteria in order to account for uncertainty in the selection procedure. The obtained results (presented above) revealed interesting structure-property trade-offs and pointed to commercial molecules which have very recently been considered or have yet to be employed as capture solvents.
The aim of the work has been further extended to include the investigation of the performance of binary mixtures that appear to be promising as CO2 capture solvents. In this context a broad range of mixture compositions (i.e. structure of each component in the mixture) and concentration (i.e. amount of each component in the mixture) is considered. Note that this is the first time that such an approach has been attempted. The literature review regarding mixtures utilized as CO2 capture solvents indicates that few options were previously examined using ad-hoc selection approaches. Instead, this CAPSOL proposes a systematic selection approach involving several decision making stages. Initially, we determine a set of mixture properties as selection criteria and investigate the ability of several different models to provide valid property predictions compared to experimental data. The considered criteria reflect the impact of different mixture chemistries on important absorption/desorption process characteristics associated with efficient CO2 capture. They are implemented in several selection stages in order to refine a rich initial set of mixtures and to identify those that may be considered as capture candidates. A multi-criteria assessment methodology is combined with a systematic uncertainty quantification approach to unveil important performance trade-offs in view of the non-ideal solvent-CO2 interactions. To highlight the impact of uncertainty in the mixture selection procedure we compare a case where uncertainty is not considered during the selection with a case where uncertainty is considered. The two sets obtained in both cases indicate differences in both mixture components and performance characteristics. It is observed that the consideration of uncertainty in the selection procedure results in a more coherent set of CO2 capture candidates. Further analysis of the results indicates that several highly-performing mixtures identified in the two cases share one of the two components, while the impact of each component in the mixture performance is also investigated.
Overall a database of 459 molecular structures was generated from the implementation of CAMD. 126 amines were found in publicly available databases or previously considered as CO2 capture solvents in absorption/desorption systems, while 333 solvents are potential novel structures. All the molecules were evaluated and rank-ordered using a performance index which unifies all the properties considered as solvent selection and design criteria. The obtained results were broken down into 4 classes (categories) of molecules based on their performance ranking.
• The 1st class considers the top 10 structures of the 25 molecules previously employed as CO2 capture solvents (Reference class).
• The 2nd class considers the top 10 molecules resulting from rank-ordering the 459 available molecules, denoted as class of Designed molecules although it also includes the 126 amines found in databases.
• The 3rd class considers only the top 10 structures of the 126 solvents found in databases, denoted as class of commercially available molecules.
• The 4th class focuses only in the top 10 alkanolamines among the 126 molecules denoted as the Commercial Alkanolamines class.
The obtained results depicted in Figure 3 clearly indicate that the class of designed molecules performs better than all other classes (the lower the aggregate performance index the more preferable the solvent is), whereas commercially available molecules exist that have yet to be considered as CO2 capture solvents and perform better than available solvents. Monoethanolamine (MEA), which the most commonly used solvent in amine based CO2 capture processes exhibits a lower score than most of the other selected solvents. Figure 4 shows the comparative performance of some selected solvents in properties (molecular volume, Vm, vapor pressure, Pvp, surface tension, σ, liquid heat capacity, Cp, viscosity, n, CO2 solubility, RED, basicity, pKa) used to form the aggregate performance criterion.
In conclusion, CAPSOL advances in both group contribution thermodynamic modeling and CAMD enables the identification of a small set of molecules that exhibit high performance in terms of desired properties associated with the capture process. The list of molecules extends the current state-of-the-art at it includes molecules that have not yet been researched in CO2 capture studies. Therefore, the list of highly performing molecules includes some that have been identified by other researchers as potential good colvent candidates.
Unit operations level advances
At the unit operations level, CAPSOL developed innovative absorption process models of variable resolution and phenomena descriptive capability that were subsequently used in the identification of highly performing process flowsheets and column internals. Performance was assessed by considering a set of economic, sustainability and operational criteria. The presentation of the developments in process models, optimal design of process flowsheets and column internals is described in greater detail.
Process Model Development
Process models are essential elements for the identification by design of highly performing process flowsheets in post-combustion CO2 capture. Therefore, the development of a framework for the efficient modeling of reactive absorption and desorption processes for the separation of CO2 from flue gas with the help of aqueous amine or other type of solutions becomes of paramount importance. Such a framework is consisted of a complete suite of mathematical models that would enable the description of all underlying physical and chemical phenomena that occur in reactive absorption and desorption (stripping) columns and further ensure good accuracy of predictions over a large range of operating conditions. However, models of different resolution and degree of detail are required for the variety of tasks in which process models are used. Flowsheet configuration design require conceptual models that capture the main process trends whereas more detailed and rigorous models are more suitable for optimization of operating conditions, packing structure optimization, and control system design. Conceptual models may be quite simple and concise in structure but must be accurate within a reasonable limit. More rigorous models require the careful identification and estimation of multiple model parameters associated with the phenomena description but must also provide the necessary flexibility in order to enable the realization of complex column configurations. Concurrently, models should be computationally efficient so that they can allow the simultaneous optimization of large column trains and sequences in the course of complex flowsheets synthesis. Computational efficiency is mainly judged based on solution effort and convergence robustness properties.
Flowsheet synthesis and process design
A generalized framework is proposed for the optimal design of post-combustion CO2 capture processes based on a systemic and flexible equilibrium separation model that employs orthogonal collocation on finite elements (OCFE) techniques. Within this context, a column section of adaptive separation capability and functionality serves as the fundamental structural block for the identification of efficient separation schemes. Separation column sections in combination with heat transfer blocks as well as stream splitters and mixers enable the generation and evaluation of alternative flowsheet configurations within a non-linear optimization program (Figure 5). The main objectives for the flowsheet evaluation involve separation and thermal efficiency that eventually impact the economics of the overall process. The proposed design framework was used for the optimal design of alternative flowsheet configurations for the separation of CO2 from a flue gas stream using amine solutions identified by the CAMD procedure. The achieved performance was compared against the performance obtained by a 30% weight MEA capture plant.
The simultaneous assessment and evaluation of five alternative process flowsheet configurations and four different solvents for solvent based post combustion CO2 capture processes is carried out in this work. The various flowsheets are generated using a generalized process design framework with the concept of maximizing the driving forces in the separation units and thus the intensification of the process. Design optimization results for a CO2 capture plant treating a flue gas from a quicklime plant reveals that:
• Reductions in the range of 30-35% in the annual expenses can be achieved when 2-Amino-2-methyl-1-propanol (AMP) is used as the CO2 capture solvent.
• Absorber intercooling enhances the process behavior significantly and leads to a subsequent reduction of both capital and operating expenses.
• Reduced energy demand was achieved (1.79 GJ/ton CO2) using AMP and a combination of stripper stream redistribution and absorber intercooling. Previously reported values from the CESAR project include 2.9 GJ/ton CO2 using absorber intercooling.
• Using a combination of stream redistribution in the stripper and intercooling of the absorber, process cost reductions in the range of 15-35% can be attained, depending on the employed solvent.
Sustainability
Despite the development of several general sustainability indicator frameworks in literature, there is still a need to adjust these and/or develop new indicators on a case by case basis. The overall goal of CAPSOL has been to develop a framework of sustainability indicators suitable for assessing the different solvents and process schemes for post combustion CO2 capture, focusing on the holistic environmental benefit for normal process operation through a Life Cycle Assessment (LCA) approach and substance/process Environmental Health and Safety (EHS) hazard identification for evaluation of the harm potential in accidental scenarios. The framework comprises two phases of assessment at the level of basic design, substance and process level assessment. Both assessment phases are based on methods that are well established in literature. The framework has been modified and extended as more information became available at subsequent solvent/process design levels. For the purpose of testing the methodology and concepts proposed, a reference set of solvents was compiled and assessed on a substance level. The substance level assessment performed included the application of two EHS hazard analysis methods, the EHS method and Inherent Safety Index (ISI) method. LCA assessment included obtaining the Cumulative Energy Demand (CED) which is a resource oriented indicator, the Global Warming Potential (GWP) and the Eco-Indicator (EI) 99 which are both damage oriented indicators. Among the open issues to be investigated are the mechanism of dealing with data gaps and increasing the flexibility of different methods, estimating the LCA indicators through reaction chemistry and the estimation of the rates of solvent degradation and equipment corrosion.
The sustainability assessment shows that AMP is a superior solvent from both an EHS and LCA point of view compared to the other solvents in the test group. However AMP suffers from slower kinetics and therefore, it would be more comprehensive to conduct further assessment based on a rate based model, so that its disadvantages are more apparent. Two waste treatment scenarios have been compared to account for solvent loss through degradation and to reduce the impact of degradation products formed. The reclaimer scenario that involves the regeneration of the degraded amine was shown to give better performance from an LCA perspective (5-15% improvement in different LCA metrics), whereas the EHS assessment was mostly insensitive to the change as there are no significant differences within the process boundaries between both cases. It is important to consider degradation products, although the parent amine will still dominate the results of most EHS metrics, due to its higher mass in the system.
Control and operations
The optimization-based approach in the calculation of efficient CO2 capture process plants aims at the simultaneous determination of the flowsheet configuration and the equipment design parameters. However, the capture plant is required to operate under variable process conditions due to either production level shifts or the influence of unexpected process disturbances. In order to ensure the satisfaction of the operating and economic specifications for the CO2 capture plant a reliable and efficient control system should be designed that would be able to alleviate the effects of disturbances on the process objectives. The plantwide control structure must be then design and its performance investigated. To this end, a set of candidate flowsheet and control structure configurations must be analyzed under the presence of multiple and large in magnitude disturbances that are likely to affect process operation and process economics. It is generally accepted that the economic result of a process system may be significantly altered if the process systems failed to quickly recover from the influence of a disturbance.
Specifically, a capture system must compensate for variable flue gas volumetric flowrates, concentration and temperature, changes in the kinetics of the reactions, uncertainty in the thermodynamic property prediction, and malfunction of the various equipment that form the overall system. Such changes may occur with different intensity and frequency. The influence of variability in the operating environment will affect the amount of CO2 capture by the system, and the conditions in the unit operations that subsequently influence the energy requirements for the capture of CO2 and the economics of the plant (Figure 6). It has been exhibited within the CAPSOL project that a specific solvent capture system that recorded good economic performance at the nominal operating conditions may have its performance drastically deteriorating under the presence of commonly occurring disturbances. It is then suggested that the evaluation of process flowsheets incorporating commercial or novel solvents should consider the impact of the disturbances. Therefore, the design and implementation of a capable control system is of paramount importance for the efficient operation of a capture plant.
The approach that is employed involves the evaluation and screening of alternative process flowsheet and control structure configurations in a rigorous, effective and systematic way. It utilizes an effective decomposition of the process and control system design tasks, which in sequence allows the enhancement of the process controllability properties. The quality of the steady state behavior in response to the detrimental effects of multiple simultaneous process disturbances and model parameter variations is an essential prerequisite for good economic performance during operation. Disturbance rejection sensitivity for a candidate process flowsheet is investigated in conjunction with decisions encompassing plantwide control objectives for the process. The objectives reflect the hierarchy in achieving certain targets and exploiting available resources for control purposes. The controllability framework enables the evaluation of control strategies outlined by the weighting of the objectives and the input-output structure of the candidate controller. The method employs rigorous and detailed mathematical models that intend to capture nonlinear effects arising from the physical system and potentially intensified by the interactions of multiple and simultaneously acting disturbances. Disturbance directionality and magnitude are two key factors that are thoroughly investigated and explored. The calculation of a static controllability performance index representative of the static disturbance rejection characteristics becomes the basis for the assessment and ranking of the alternative flowsheets and control structures.
Dynamic characteristics of the candidate process design play the most dominant role in the achievable dynamic performance of the control system. The performance of the control system is inherently affected by the dynamics of the designed process. Process dynamic characteristics are influenced not only by process design decisions but also by model parameters variations. Sensitivity analysis determines the margins of the process design from undesired dynamic behavior (e.g. unstable, undesired oscillatory or sluggish response) at the presence of uncertainty. Nonlinear process models act as the basic tools for the identification of the process dynamic components during a disturbance scenario that involves multiple disturbances of finite magnitude.
The modification of the design decision variables using nonlinear sensitivity information becomes an additional instrument for the design engineer in order to improve the desired static and dynamic properties of the plant. Flowsheet design parameters are associated either with the structure of the flowsheet (e.g. selection of units, connectivity of units and so forth) or the equipment design specifications. The disturbance rejection exercises and their influence on the static and dynamic controllability indices reveal the relationship among performance indicators and design parameters. Proper modification of the design parameters utilizing nonlinear sensitivity analysis calculations can enhance the static and dynamic controllability properties of the design while maintaining the economic attractiveness of the final design. The complete design procedure is outlined in Figure 7.
Column internals design
The selection of suitable column internals is an important prerequisite for an optimum operation of gas-liquid separation processes. The removal of CO2 from gas mixtures realized by absorption into a liquid solvent is usually performed in columns filled with structured packings. Standard structured packings have a corrugation angle of 45 degrees or 60 degrees. Using different possible corrugation angles may result in better column performance. The corresponding analysis can be done with model-based simulations.
The aim of CAPSOL project was to develop an integrated modeling framework for the complementary application of three modeling approaches, namely, Computational Fluid Dynamics (CFD), Hydrodynamic Analogy (HA) and the Rate-based Approach (RBA). This framework should be used to facilitate design of innovative internals and equipment for solvent-based CO2 separations. The characteristics of the models in terms of model accuracy and flow complexity as well as the information flow from one model realization to the others is shown in Figure 8.
Computational fluid dynamics models aim at describing the flow characteristics in a representative packing element. It is assumed that the element is repeated in order to represent the entire structure. The model calculates the flow pattern and enables the prediction of the dry pressure drop in structured packing. The model has been validated using experimental data in equivalent units.
Hydrodynamic analogies models represent real complex two-phase flow in a packing as a combination of geometrically simpler flow patterns (Figure 9). In the physical model the packing is represented as a bundle of parallel inclined channels with identical cross section. The number of the channels as well as their diameter is determined from the packing surface area and corrugation geometry. The gas flow behaviour depends on the operating conditions and varies from laminar to fully developed turbulent flow. The liquid flows counter-currently to the gas flow in form of laminar films over the inner surface of the channels. Additionally, a uniform distribution of the both phases in radial direction is assumed, i.e. no maldistribution is taken into account in the model. The required parameter for the proper description of the gas-phase turbulence in the HA model was estimated using CFD analysis of single-phase gas flow through structured packing.
Rate-based models consider the entire separation column as a series of stages in which mass transfer, reaction kinetics and equilibrium, and fluid dynamics (Figure 10). Diffusion and mass transfer coefficients as well as hold-up and interfacial area are being estimated through the “virtual simulated experiments” using CFD and HA models. Rate-based models can then determine the required packing height for a given absorption rate.
The integrated modeling framework for simulation of innovative structured packings for the CO2 absorption has been utilized in MEA and other CAPSOL solvent solutions. The simulated procedure achieved the investigation of the influence of corrugation angle of structured packings on the separation efficiency and dry pressure drop.
Modeling of gas-liquid separation processes usually requires experimentally determined parameters such as mass transfer coefficients, which cannot be determined without expensive experimental work. A novel modeling approach based on hydrodynamic analogies (HA) has recently been developed and successfully tested for distillation units equipped with structured corrugated sheet packings. The HA approach is an alternative way to describe hydrodynamics and transport phenomena n processes, in which exact location of the phase boundaries is hardly possible. Contrary to the traditional models based on the film theory, separation columns can be described without using mass transfer coefficient correlations.
In CAPSOL, the HA approach was applied to carbon dioxide absorption into aqueous monoethanolamine. The composition profiles were determined in an absorption column filled with structured packings and subsequently checked against experimental data. The HA model has been For the gas phase, concentrations at the top and bottom were measured. For the liquid phase, full concentration profiles were determined.
Column packing manufacturing
Post-combustion capture plants, as considered in the CAPSOL project, apply absorption and desorption technology to separate CO2 from flue gas. The project focused on the absorption of CO2 into amine based solvents followed by stripping of CO2 in a desorber, which up to date is considered to be the most promising technology. Hence, columns for absorption and desorption are involved that apply these internals. It is well known that choosing the right technology for mass transfer internals is very important, as their specific characteristics in terms of pressure drop, hydraulic and separation performance are significant factors for operating and investment costs of CO2 capture plants.
The most promising structured packing characteristic to be optimized for CO2-absorption purposes was identified to be the specific pressure drop. A lower specific pressure drop will lead to reduced energy consumption of the flue gas blower. The predominant modification method to reduce the pressure drop is to increase the inclination angle of the oppositely oriented flow channels of corrugated sheets structured packings are made of. CFD simulations were performed and the diagram shown in Figure 11 could be derived. The diagram shows the dry pressure drop depending on the inclination angle for various F-factors (column loading factor).
As can be seen, at inclination angles above 70°, the pressure drop is only decreasing marginal. At this point it was decided to manufacture a packing with an inclination angle of 75° by Julius Montz GmbH (MONTZ) (Figure 12). This packing would show a very low pressure drop, while the film flow at the packing surface could still persist.
Fluid dynamic experiments at the University of Paderborn (UPB) confirmed the drastic reduction of the pressure drop for both dry and irrigated conditions. Figure 13 shows a comparison of the measured dry pressure drop for a packing with 45° and 75° inclination angle. Figure 14 shows the same comparison at irrigated conditions. At F-factors between 2 and 3 Pa0,5 the pressure drop can be reduced by 90 to 97%.
In addition, experiments were conducted to evaluate the absorption efficiency using this new packing. As expected, the absorption rate is slightly decreased for the new packing geometry with the steeper inclination angle. However, this reduction does not place a critical burden in the associated capital costs of the capture plant and is therefore considered a reasonable compromise.
Pilot plant testing
During the CAPSOL project a pilot plant for the absorption and desorption of CO2 was built at the University of Paderborn.
The pilot plant (Figures 15 to 20) is conceived as a multi-purpose plant. Experiments can be carried out in four operation modes: batch absorption, batch desorption, closed loop and fluid dynamics. In order to enable all four operation modes, the plant comprises two glass columns, one with an inner diameter (ID) of 100 mm and another with an ID of 300 mm. Both columns are about 5 m high, and each column includes a packed section of about 3 m height. The smaller column is to be predominantly used for absorption. Due to the small diameter and consequently considerable wall effects, this column is not suitable for fluid dynamic experiments. In contrast, the bigger column can be used both for desorption and for fluid dynamic experiments. To realize a closed loop mode, both columns are to be linked. The absorption (small) column can be operated at F-factors varying between 1 and 3.5 Pa0,5 and liquid loads between 10 and 60 m3m 2h 1. In desorption mode, the large column is operated with the same liquid loads as the absorption column. In fluid dynamic mode, it can be operated at F-factors varying between 1 and 4 Pa0,5 and liquid loads between 20 and 90 m3m 2h 1. A detailed flow sheet of the plant is given in Figure 20.
Before the plant was used to test the new CAPSOL packing and solvent it was validated by performing fluid dynamic and absorption experiments. To this end, Figure 21 shows measured values of the dry pressure drop depending on the F-factor. Measurements at UPB using both columns are compared to measurements by Julius Montz GmbH using a column with an inner diameter of 600 mm. It can be seen that UPB measurements at the bigger column (diameter of 300 mm) agree well with the values obtained by Montz.
Measurements of the pressure drop of irrigated packing were carried out at liquid loads of 10, 20 and 50 m³m 2h 1. For low liquid loads, our measurements showed good agreement with the values by Montz (see Figure 22). The slight deviation can be explained by the clearly smaller diameter of our column compared to the column at Montz. A higher deviation in Figure 16 at a liquid load of 50 m3m 2h 1 is most likely due to water accumulation in the pressure measuring system resulting in measurement errors.
Based on these tests, it can be concluded that the bigger column at UPB is applicable for studying fluid dynamics of different packings.
Additionally, absorption experiments with monoethanolamine were performed. Three experiments A1 to A3 (summarized in Table 1) were carried out with liquid loads of 17 m3m 2h 1 and F-factors of about 1.6 Pa0.5. The solvent was a 14 % wt aqueous MEA solution. The inlet CO2 mole fraction varied between 0.045 and 0.091.
Figure 23 shows the gas-phase CO2 concentration profiles and Figure 24 the temperature profiles along the column height.
As the profiles are showing reasonable trends, we can conclude, that the pilot plant can be used with confidence for thorough experimentation in the field of packing and solvent design.
Plant level advances
Several industrial plants in power generation have been considered for the integration of CO2 capture plant units. The four selected reference power plants are:
• Supercritical lignite fired steam power plant of a power output of 650 MWe gross.
• Supercritical bituminous coal fired power plant of a power output of 650 MWe gross.
• Natural gas fired combined cycle of 420 MWe.
• Quicklime production plant.
The 650 MW bituminous plant is based in the CESAR WP2 Deliverable D2.3.1 – “Baseline Powerplant Documents”
(http://www.co2cesar.eu/downloadables/Deliverables%20Public%20Summaries/CESAR-D2.3.1-APPROVED-Baseline%20Power%20Plants%20Documents%20PUBLIC%20SUMMARY-2010.03.26.pdf) .
The natural gas fired combined cycle of 420 MWe from the Scottish Power report whereas the 650 MW lignite fired steam power plant as well as the quick lime plant are new reference plants for the CAPSOL project.
The framework describes general technical and economic assumptions and a possible procedure for evaluation of different CO2 capture technologies both on quantitative evaluation parameters such as break-even electricity cost, specific CO2 emission avoidance cost etc. and on 18 different qualitative evaluation parameters. The assessment approach described here is aligned with the methodology being used in other FP7 projects through a joint working panel known as the European Benchmarking Task Force, whose activities are reported under CESAR WP2.4 (http://www.co2cesar.eu/downloadables/Deliverables%20Public/CESAR-D2.4.1-APPROVED-EBTF%20Common%20Framework%20Definition%20Document%202009.08.28.pdf).
Heat Integration
Lignite Fired Power Plant: The 650 MWe super-critical lignite-fired power plant with a CO2 capture process has been considered, where the capture unit has been in two variations: operating with MEA and CAPSOL capture system. When the CO2 capture unit with MEA is simply added to the plant using directly steam extracted from the turbine train for reboiler heating, the power generation reduction (power penalty) of the plant is 97.8 MWe. This is equivalent to 15 % comparing the non-optimized lignite power plant with carbon capture and the standalone lignite power plant. The cooling requirement in this case is 760.9 MW.
The proposed heat integration options reduce the steam extraction from the turbine for condensate return heating, and reduce the power penalty of the turbine island. The integrated process generates 577.1 MWe of power and requires 654.0 MWth of cooling utility. The power generation increases by 24.8 MWe, while the cooling demand of this integrated process is reduced by 106.9 MWth. The power generation penalty is 11.2 % comparing the heat integrated lignite power plant with carbon capture and standalone lignite power plant without carbon capture unit. As a result, the heat integration helps in reducing the power penalty from CO2 capture by 15-11.2 = 3.8 %.
The revenue from gross power generation is equivalent to an average of € 379.1 x 106 /y. However, the process integration options are able to save € 25.6 x 106 /y of utility cost. The CAPSOL capture system has also been evaluated, where the heat integration is able to save 5.39 MWe gross power. The cooling demand of the carbon capture plant with the CAPSOL technology increases by 404.7 MW, while the gross power penalty reduces to 10.40 %.
Coal Fired Power Plant: The nominal capacity of the plant is 650 MW electricity generation. The standalone power plant needs only a cooling utility for 624.7 MW and adding the MEA based CO2 capture increases that to 655.8 MW. Several heat integration options have been identified and implemented.
Adding the capture unit to the standalone coal power plant introduces power penalty of 91.9 MW (14.1 % of the nominal capacity). The Process Integration measures reduce the penalty to 10.4 % (3.7 % saving). For the CAPSOL capture system the process integration options are able to save € 9.7 x 106 /y of utility cost. The gross power output increases by 8.46 MWe, which is equivalent to reducing the power penalty to 9.05 % (14.1-9.05 = 5.05 % saving) of the nominal plant rating.
Gas Fired Power Plant: The nominal power generation of the plant is 423.5 MW. The total minimum cooling demand for the stand-alone power plant and the one with MEA CO2 capture unit is found to be 123.8 MW and 333.2 MW, respectively. Process modification options have been identified for reducing the energy requirement and the power penalty.
The power penalty due to the steam extraction for powering the CO2 capture is 30.5 MW (7.2 % of the nominal capacity), which is equivalent to an average of € 20 x 106 /y. The process integration options are able to save € 62.89 x 106 /y of utility cost.
The CAPSOL capture system is considered in the last part of the study. The gross power output increases by 5.60 MWe, as result of the integration which equivalent to 5.89 % of power penalty. The total cooling demands of the CAPSOL capture plant increased by 826.7 MWth.
Quicklime Plant: The quicklime plant is a simpler one. There is only one viable option for heat integration related to the utilization of the waste heat from the operation of Ca(OH)2 production from CaO. This can be utilized by generating steam with thermal load of 969 kW. A portion of this waste heat can be exploited within the CO2 capture process in order to preheat the rich stream exiting the absorption column and heading to the stripper.
Conclusions
CAPSOL technology enables the systematic design of solvent and solvent blends based on Computer Aided Molecular Design tools that employ accurate group contribution thermodynamic property prediction models and multi-criteria optimization techniques. The process performance of the identified new solvents and solvent blends against economic, sustainability and other environmental criteria is effectively utilized for the development of process flowsheet configuration of improved ability to reduce the energetic requirements of the CO2 capture process. A multi-scale modeling sequence is at the center of a rigorous procedure to unveil the complex flow pattern and transfer phenomena within the column internals and optimize the geometric characteristics of the packing structure. The CAPSOL capture plant consisted of the preferred solvent, the optimal flowsheet configuration, and the optimized structured packing has been integrated thermally with existing power plant in order to further reduce the overall energetic requirements.
Potential Impact:
CAPSOL Impact of Results
The CAPSOL impact can be characterized by major contributions at two distinct levels. The first level involves the development of novel methodologies in thermodynamic property model based on group contribution, computer aided molecular design for solvent mixtures, process flowsheet synthesis and design optimization utilizing flexible process models, and the multi-scale modeling for the optimization of the geometric features of structured packing. The second level of impact involves the development of new technological advances in solvent based post combustion CO2 capture through the implementation of pre-existing methods and CAPSOL developed methods.
A significant breakthrough in thermodynamic property modeling was made by showing for the first time that it is possible to develop a group contribution approach to represent the challenging phase and chemical equilibrium of CO2 + water + alkanolamine mixtures at different temperatures and pressures. This was achieved through the use of implicit reaction models (i.e. by representing the reaction products via association sites) within the framework of the Stochastic Associating Fluid Theory with square well potentials or SAFT-γ SW equation of state. The concept of second-order groups was introduced for the first time in a SAFT-type group contribution equation of state to tackle the multifunctional nature of capture solvents. A large number of interaction parameters for basic groups were derived. These form the essential building blocks for novel solvent design. Such developments not only assisted in the identification of novel solvents in CO2 capture but also set the ground for extending property prediction for a vast number of applications in process industry such as separations (e.g. extractive distillation) and catalytic reactions.
It is the first time that Computer Aided Molecular Design (CAMD) has been extended to include the investigation of the performance of binary mixtures that appear to be promising as CO2 capture solvents. In this context a broad range of mixture compositions (i.e. structure of each component in the mixture) and concentration (i.e. amount of each component in the mixture) is considered. Incorporating LCA (Life Cycle Analysis) and SHE (Safety-Health-Environmental) hazard assessment in the CAMD results has identified existing and newly proposed molecules with a potential reduction of the cradle-to-gate environmental impact up to 50% (e.g. in EcoIndicator units) and the hazard impact up to 20%. CAMD framework assisted by group contribution thermodynamic property prediction models and sustainability indices succeeded to identify multiple solvents and solvent blends with potentially superior performance than currently used solvent technologies.
A systematic process flowsheet synthesis and design optimization framework equipped with flexible and accurate process models achieved in obtaining process solutions that reduce in the range of 39% the annualized capture plant expenses and 56% the energy requirements. The investigation of sustainability in process solutions further reinforces the impact of the process design solution. This indicates a great boost in CO2 capture technology that can have a tremendous impact in industry and the environment. The reduction in the costs and energy implies that the attractiveness of solvent based CO2 capture increases with more industry adapting the technology for greater CO2 reductions.
Innovative column packing achieved a 97% reduction in pressure drop for the flue gas in the absorption column hence minimizing the energy requirements by the blowers. Considering the extremely large volumetric flow rate of the flue this is a significant factor in reducing the overall energy footprint. The new packing has generated a new type of product that has been subsequently used in the CAPSOL pilot plant successfully.
Heat integration in post combustion capture enables the efficient utilization by the capture plant of available thermal energy in the power plant. The main aim is the minimization of the overall penalty induced by CO2 capture. Extensive studies in the most commonly used type of power plants with fuels varying from natural gas, to lignite and coal have improved the CO2 capture penalty by 4 % - 10 %.
The main developments within CAPSOL project increase the viability of the post combustion CO2 capture process, which subsequently enhance the attractiveness of the technology. Solvent based CO2 capture remains one of the most suitable technologies for the mitigation of the hazardous effects of CO2. CAPSOL advances have added significantly to the benefits of the technology. It is therefore expected that more industrial players will seek CO2 capture technology that will increase investments and employment in manufacturing of columns and process equipment, engineering companies and process personnel.
Exploitation potential
CAPSOL created exploitation potential in several areas as outlined below.
Advanced solvents and blends.
A list of novel solvents with high potential has been identified as a result of CAPSOL project. Some of these solvents have never been studied before theoretically experimentally. Such outcome enriches knowledge in the field and sets the ground for opportunities in further exploring the potential use of these solvents or solvent blends in CO2 industrial applications. A plan to run experimental and simulation studies for these solvents will eventually validate their performance.
Property prediction models.
Process Systems Enterprise Ltd (PSE, www.psenterprise.com) has acquired the exclusive rights to the SAFT software developed at Imperial College London. As part of the collaboration agreement between PSE and Imperial College, the Imperial team is assisting PSE in developing applications for SAFT. PSE have recently developed a modelling tool for carbon capture and storage applications (gCCS, http://www.psenterprise.com/power/ccs/gccs.html) in which the SAFT equation of state provides key thermodynamic information for capture plants and carbon dioxide transmission. The gCCS tool was developed in collaboration with major players in the energy industry. The SAFT models within gCCS are currently based on a molecular representation of the components involved, as developed in previous work by the Imperial team. PSE are aware of the progress made in the CAPSOL project and CAPSOL partners and PSE will work together in the future to come to incorporate the group-based representation developed through the CAPSOL project. This will significantly improve the predictive capability of the approach and make the advances realized within CAPSOL accessible to all gCCS users, and more broadly all users of PSE products. The framework and theoretical advances achieved will also be used to extend the capabilities of the commercially-available version of SAFT, enabling for the first time the modeling of weak electrolytes within a group contribution equation of state.
Custom-made Computer-Aided Molecular Design Procedure and Software.
A new framework for the design of molecules of desired properties and optimal process performance has been the outcome of CAPSOL project. New improvements over previously developed software include the option for the design of specialized solvents and solvent blends for CO2 capture. The new advances in CAMD procedure will enable the extension of the application to other separation systems.
Multi-scale computer aided design of post-combustion CO2 plants.
A method has been available for multi-scale generation and multi-criteria assessment of process alternatives for solvent-based post-combustion CO2 capture that is computationally efficient and facilitates reliable screening in early phases of conceptual process design. The method should be able to generate and screen a large number of process alternatives with respect to diverse process features (i.e. solvent molecules, process layout and process operating conditions) and prioritize a reduced number of superior process alternatives to be tested in subsequent rigorous design stages. Notwithstanding the innovative features of this multi-scale approach, the method should also be easily compatible with existing design frameworks and software tools widely used by process system engineering companies. Therefore, the enhancement of existing screening tools in early phases of process design will be realized via the complementary, specialized features of the developed method.
Novel absorption/desorption flowsheet features
The development of innovative absorption/desorption flowsheets is a definite outcome of the research activities of CAPSOL project. Novel flowsheet configurations for various solvents that have not been tested thoroughly prior to CAPSOL project have been determined. Models of variable resolution assist in the quick but efficient screening among multiple flowsheet alternatives and options.
Novel or improved column equipment and process design
Partners involved in the development of improved column equipment (structured packings and non-separating internals, e.g. distributors) and process design will create relevant software tools that can be brought to a commercial level. To date, the available mass transfer contactor characteristics have so far basically been empirically derived from early performance tests of some standard applications not taking any specific and detailed characteristics of the application system itself into account. The methodology proposed in the CAPSOL project is different as it applies a model-based contactor optimization methodology including hydrodynamic analogy (HA) and computational fluid dynamics (CFD) models in order to propose a contactor designed for one specific application thereby taking all relevant and specific system parameters into consideration. The optimization work is focused on the main process parameters, primarily it tries to find the ideal compromise between separation performance and pressure loss characteristics.
Academic partners will use their software for educational, research, and training purposes, whereas industrial partners will utilize it for the design of innovative packings at reduced development time and cost.
Highlights: MONTZ has already designed a new commercial packing material product using the software tools.
Innovative power cycles and retrofitting options
New integrated flowsheet configurations incorporating CO2 capture plants in existing power plants will provide the exploitable item. Beneficiaries will mainly be the two industrial users in the consortium. In addition the academic partners will be able to promote the new knowledge to their industrial consortia.
Techno-economic studies
Detailed techno-economic studies on CO2 capture technology incorporation in lignite fired steam power plant, supercritical hard-coal fired power plant, natural gas fired combined cycle, quicklime production plant. A complete techno-economic study on solvent based CO2 capture technologies for a variety of power plants and other CO2 emitting plants provides the basis for exploitation of the acquired knowledge from the project.
Experimental and pilot plant data
Partners involved in the performing of pilot plant tests will set-up a database consisting of all measured data (e.g. temperature and concentration profiles; energy consumption values; degradation phenomena evaluation). A part of this data will be published in established scientific journals and presented on conferences thus providing a valuable input to industry and academia. The rest will be made available for industrial use. The University of Paderborn pilot plant will further be used for educational and training purposes.
SHE (Safety-Health-Environmental) hazard assessment method for CO2 capture
Various SHE hazard assessment methods have been developed for early stages of process design in the last two decades. In CAPSOL the most relevant features of these general methods for the solvent-based post-combustion CO2 capture have been screened and prioritized. The output is a list of applicable rules for SHE hazard assessment that can be either used as a stand-alone assessment method for preliminary screening in early design stages or integrated in risk assessment toolboxes for chemical and/or power plants. The promotion of the method and the potential for market exploitation will be first explored by the Safety & Environmental Technology group via its collaboration network with Swiss chemical and insurance companies and public offices for environment and energy.
Methods for estimation of supply chain relevant Life Cycle Assessment (LCA) impacts
LCA impacts often suffer from data gaps, especially with respect to supply chain information of chemicals required for a comprehensive cradle-to-gate impact analysis. For the solvent-based post-combustion CO2 capture, an important issue of data gaps refers to the supply chain of solvents considering also their degradation rate. Here, it is intended to provide a framework of complementary methods depending on available information and the required detail of design. The framework will mainly consist of QSAR correlations of LCA impacts to molecular structures, but will also account for decomposition of the supply chain, where more accurate information is available from existing data sources. The framework will focus on compatibility with existing LCA databases (e.g. Ecoinvent Center) and software tools (e.g. SimaPro®) to enhance the applicability of the framework by the process design and LCA community.
Optimization of structured packings
The CAPSOL exploitation potential lies in the methodology for optimising structured packings by adapting its geometric parameters according to the specific characteristics of the separation task. This is a fundamentally new approach compared to what the manufactures have been following within the last decades, and this approach may lead to significant process intensification for many applications. Even though the investigations have been carried out for one process example only (CO2 absorption with MEA), the methodology for the equipment optimization followed in the project is in principle transferable to diverse distillation and absorption applications. This offers vast opportunities to apply the methodology developed in the CAPSOL project for future optimization activity.
Flowsheet design for CO2 capture and heat integration for the quicklime process
Heat integration opportunities in quicklime production the energy released from the production line of another product. The production line of calcium hydroxide (slaked lime) is a net energy supplier. The heat released by this process can be efficiently utilized by a CO2 capture unit hence significantly reducing the energy penalty. This is a sort of symbiotic processes for the production of a useful product while the emissions from the initial process are being captured.
Educational and training activities
Several academic initiatives have been originated from CAPSOL project. Academic partners and those involved in scientist training will utilize the new results and technology for the enrichment of their educational programs and training modules. In particular, the experimental and pilot-plant set-up will be integrated in the education and training of students and researchers. The developed tools for the design optimization, the integration of the CO2 capture units within existing power plants will form the basis to further enhance the links of academic and research oriented organizations with industry
Dissemination of Results
The CAPSOL website (https://arquivo.pt/wayback/20180718123649/http://www.capsol-project.eu/) provides a comprehensive overview of the main achievements and results. The consortium will maintain the project website for at least five years after the completion of the project and update its contents with new publications and presentations arising from the project results. A specific section in the website will be devoted to the exploitation of the CAPSOL foreground knowledge by the project partners. CAPSOL project was part of the organizing team along with four other active FP7 projects (DemoCLoCk, iCap, Innocuous and IOLICAP) for the Carbon Capture and Storage technologies conference that took place in Antwerpen, Belgium, between May 28 - 29th, 2013.
The key instrument for the dissemination of the CAPSOL results was the preparation and publication of mainly scientific articles in peer reviewed journals and periodicals. The complete list of publication along with a designation regarding accessibility of the article in some form (publisher’s edition, post-refereed or pre-refereed) is given below:
1. Rodriguez J, N MacDowell, F Llovell, CS Adjiman, G Jackson, A Galindo, “Modelling the fluid phase behaviour of aqueous mixtures of multifunctional alkanolamines and carbon dioxide using transferable parameters with the SAFT-VR approach”, Molecular Physics: An International Journal at the Interface Between Chemistry and Physics, 110(11-12), 2012, 1325-1348. (access in public institutional repository)
2. Papadopoulos AI, M Stijepovicb, P Linke, P Seferlis, S Voutetakis, “Molecular Design of Working Fluid Mixtures for Organic Rankine Cycles”, Computer Aided Chemical Engineering, 32, 2012, 289-294. (access in public institutional repository)
3. Papadopoulos AI, Stijepovic M, Linke P, Seferlis P, Voutetakis S, “Multi-level Design and Selection of Optimum Working Fluids and ORC Systems for Power and Heat Cogeneration from Low Enthalpy Renewable Sources”, Computer Aided Chemical Engineering, 30, 2012, 66-70. (access in public institutional repository)
4. Yildirim O, AA Kiss, N Hueser, K Lessmann, EY Kenig, “Reactive absorption in chemical process industry: A review on current activities”, Chemical Engineering Journal, 213, 2012, 371-391. (access in public institutional repository)
5. Čuček L, PS Varbanov, JJ. Klemeš, Z Kravanja, “Potential of Total Site Process Integration for Balancing and Decreasing the Key Environmental Footprints”, Chemical Engineering Transactions, 29, 2013, 61-66. (access in publisher’s website)
6. Čuček L, PS Varbanov, JJ. Klemeš, Z Kravanja, “Reducing the Dimensionality of Criteria in Multi-Objective Optimisation of Biomass Energy Supply Chains”, Chemical Engineering Transactions, 29, 2013, 1261-1266. (access in publisher’s website)
7. Damartzis T, AI Papadopoulos, P Seferlis, “Generalized Framework for the Optimal Design of Solvent-Based Post-Combustion CO2 Capture Flowsheets”, Chemical Engineering Transactions, 35, 2013, 1177-1182. (access in publisher’s website)
8. Kakaras EK, AK Koumanakos, AF Doukelis, “Greek Lignite-Fired Power Plants with CO2 Capture for the Electricity Generation Sector”, Chemical Engineering Transactions, 35, 2013, 331-336. (access in publisher’s website)
9. Chremos A, E Forte, V Papaioannou, A Galindo, G Jackson, CS. Adjiman, “Modelling the Fluid Phase Behaviour of Multifunctional Alkanolamines and Carbon Dioxide Using the SAFT-γ Approach”, Chemical Engineering Transactions, 35, 2013, 427-432. (access in publisher’s website)
10. Pan M, Bulatov I, Smith R, “New MILP-based iterative approach for retrofitting heat exchanger networks with conventional network structure modifications”, Chemical Engineering Science, 104, 2013, 498-524. (access in public institutional repository)
11. Pan M, Bulatov I, Smith R, “Intensifying heat transfer for retrofitting heat exchanger networks with topology modifications”, Computer Aided Chemical Engineering, 32, 2013, 307-312. (access in public institutional repository)
12. Pan M, Bulatov I, Smith R, “Heat Transfer Intensified Techniques for Retrofitting Heat Exchanger Networks in Practical Implementation”, Chemical Engineering Transactions, 35, 2013, 1189-1194. (access in publisher’s website)
13. Papadopoulos AI, Stijepovic M, Linke P, Seferlis P, Voutetakis S, Toward Optimum Working Fluid Mixtures for Organic Rankine Cycles using Molecular Design and Sensitivity Analysis, Industrial and Engineering Chemistry Research, 52, 2013, 12116-12133. (access in public institutional repository)
14. Yazgi M, EY Kenig, “Hydrodynamic-analogy-based modelling of CO2 capture by aqueous monoethanolamine”, Chemical Engineering Transactions, 35, 2013, 349-354. (access in publisher’s website)
15. Damartzis T, Papadopoulos AI, Seferlis P, “Optimum Synthesis of Solvent-Based Post-Combustion CO2 Capture Flowsheets through a Generalized Modeling Framework”, Clean Technologies and Environmental Policy, 16(7), 2014, 1363-1380. (access in public institutional repository)
16. Papadopoulos AI, Badr S, Chremos A, Forte E, Zarogiannis T, Seferlis P, Papadokonstantakis S, Adjiman CS, Galindo A, Jackson G, “Efficient Screening and Selection of Post-combustion CO2 Capture Solvents”, Chemical Engineering Transactions, 39, 2014, 211-216. (access in publisher’s website)
17. Damartzis T, Kouneli A, Papadopoulos AI, Seferlis P, Dimitriadis G, Vlachopoulos G, “Optimal Design of Solvent Based Post Combustion CO2 Capture Processes in Quicklime Plants”, Chemical Engineering Transactions, 39, 2014, 1327-1332. (access in publisher’s website)
18. Liew PY, Klemeš JJ, Doukelis A, Zhang N, Seferlis P, “Identification of Process Integration Options for CO2 Capture in Greek Lignite-fired Power Plant”, Chemical Engineering Transactions, 39, 2014, 1447-1452. (access in publisher’s website)
19. Pan M., Agulonu A., Gharaie M., Perry S., Zhang N., Bulatov I., Smith R., “Optimal Design Technologies for Integration of Combined Cycle Gas Turbine Power Plant with CO2 Capture”, Chemical Engineering Transactions, 39, 2014, 1441-1446. (access in publisher’s website)
20. Hüser N., Kenig E.Y. “A New Absorption-desorption Pilot Plant for CO2 Capture”, Chemical Engineering Transactions, 39, 2014, 1417-1422. (access in publisher’s website)
21. Li B.H. Zhang N., Smith R., “Rate-based Modelling of CO2 Capture Process by Reactive Absorption with MEA”, Chemical Engineering Transactions, 39, 2014, 13-18. (access in publisher’s website)
22. Dufal S, Papaioannou V, Sadeqzadeh M, Pogiatzis T, Chremos A, Adjiman CS, Jackson G, Galindo A, “Prediction of Thermodynamic Properties and Phase Behavior of Fluids and Mixtures with the SAFT-γ Mie Group-Contribution Equation of State”, Journal of Chemical and Engineering Data, 59(10), 2014, 3272-3288. (access in public institutional repository from August 2015)
23. Pan M, Bulatov I, Smith R, “Efficient Retrofitting Approach for Improving Heat Recovery in Heat Exchanger Networks with Heat Transfer Intensification”, Industrial and Engineering Chemistry Research, 53(27), 2014, 11107-11120. (access in public institutional repository from June 2015)
24. Pan M, Bulatov I, Smith R, “Recent methods for retrofitting heat exchanger networks with heat transfer intensifications”, Chemical Engineering Transactions, 39, 2014, 1435-1440. (access in publisher’s website)
25. Yazgi M, A Olenberg, EY Kenig, “Complementary Modelling of CO2 Capture by Reactive Absorption”, Computer Aided Chemical Engineering, 33, 2014, 1243-1248. (access in public institutional repository)
26. Hüser N, Dubjella P, Hugen T, Rietfort T, Kenig EY, “Untersuchung und Bewertung einer strukturierten Packung mit 75°-Neigungswinkel für die CO2-Abscheidung”, Chemie-Ingenieur-Technik, 86, 2014, 1451-1452. (access in public institutional repository)
List of Websites:
https://arquivo.pt/wayback/20180718123649/http://www.capsol-project.eu/
Centre for Research and Technology – Hellas (CERTH), Greece
Chemical Process Engineering Research Institute (CPERI)
Laboratory of Process Systems Design and Implementation
Contact person: Dr. Panos Seferlis
Website: http://psdi.cperi.certh.gr/
University of Manchester, U. K.
School of Chemical Engineering and Analytical Science
Centre for Process Integration
Contact person: Dr. Nan Zhang
Website: http://www.ceas.manchester.ac.uk/research/centres/cpi/
University of Paderborn, Germany
Faculty of Mechanical Engineering,
Chair of Fluid Process Engineering
Contact person: Prof. Eugeny Y. Kenig
Website: http://www.uni-paderborn.de/fvt
Imperial College of Science,Technology and Medicine, U. K.
Centre for Process Systems Engineering
Contact person: Prof. Claire Adjiman
Website: http://www3.imperial.ac.uk/centreforprocesssystemsengineering
University of Pannonia, Hungary
Faculty of Information Technology
Research Institute of Chemical and Process Engineering
Centre for Process Integration and Intensification – CPI2
Contact person: Prof. Jiri Klemes
Website: http://cpi.uni-pannon.hu/
Eidgenössische Technische Hochschule Zürich, Switzerland
Safety & Environmental Technology Group (S&ETG)
Contact person: Dr. Stavros Papadokonstantakis
http://www.sust-chem.ethz.ch/
National Technical University of Athens , Greece
School of Mechanical Engineering
Laboratory of Steam Boilers and Thermal Plants
Contact person: Prof. Emmanuel Kakaras
Website: http://www.lsbtp.mech.ntua.gr/
Julius Montz GmbH, Germany
Contact person: Dr. Thomas Rietfort
Website: http://www.montz.de
Public Power Corporation S.A. Greece
Contact person: Mr. Charalambos Papapavlou
Website: http://www.dei.gr/
CaO Hellas Macedonian Lime S.A. Greece
Contact person: Mr. Georgios Dimitriadis
Website: http://www.caohellas.gr/
Process Design Center B.v. The Netherlands
Contact person: Mr. Evert van der Pol
Website: http://www.process-design-center.com/
Scottish Power Generation PLC, U. K.
Contact Person: Mr. Alan Dickson
Website: http://www.scottishpower.com/
Executive Summary
Power generation world-wide mainly depends on the combustion of fossil fuels. Available capture technologies are predominantly based on the use of intermediate materials, namely solvents that enhance the separation efficiency by selectively dissolving CO2. Amine-based organic compounds are among the most common solvents employed in the widely utilized chemical absorption process. The globally observed preference towards solvent-based absorption is largely because the technology is well established, the conditions for both absorption and solvent regeneration (desorption) are mild and relatively easy to meet and the process can be easily retrofitted onto existing plants. A major downside of absorption/desorption is the increased energy required for solvent regeneration. This results in high capture costs, hence there is a lack of motivation by the industry to adopt this technology.
CAPSOL project employed a truly innovative and holistic approach for the improvement of the current state-of-the-art in solvent based CO2 capture technologies. The approach aimed at enhancing the sustainability features of the entire process, and reducing the overall annualized costs through higher separation efficiency and better integration solutions. In order to achieve the final goal, CAPSOL project developed novel methods and techniques at multiple levels associated with the CO2 capture system.
CAPSOL initially targeted the molecular level, where new thermodynamic models of transferable parameters enabled the utilization of group contribution methods within a computer aided molecular design framework. The outcome was the identification of solvents and solvent blends of increased affinity towards CO2, reduced regeneration energy needs and environmentally benign characteristics.
CAPSOL developments resulted in a complete suite of process models for the absorption and desorption units or variable resolution utilized in the optimal design of flowsheet configurations of reduced capital and operating costs as well as the design of highly performing packing materials with extremely low pressure drop and adequate separation efficiency.
Major industrial case studies in the area of power generation as well as materials production have been thoroughly analyzed and studied employing CAPSOL technology in solvent selection, process design optimization, equipment design manufacturing, and heat integration options. The outcome provided strong evidence that the CAPSOL technology is a viable and highly competitive alternative to the current state-of-the-art in CO2 capture.
Finally, a pilot plant scale CO2 capture system has been set in operation in order to perform sensible experiments that prove the feasibility and highlight the practicality of the CAPSOL solvent-equipment combination.
Overall, the CAPSOL technology offers definitely a superior solution than the benchmark monoethanolamine (MEA) capture plant for lignite and coal power plants, as well as quicklime production units and achieves a comparative performance for the gas fired power plants.
Project Context and Objectives:
CAPSOL Project Context and Main Objectives
The efficient capture of CO2 is reasonably regarded as one of the grand challenges for the 21st century [1], considering that a single coal-fired plant may emit up to 25 million tons of post-combustion CO2 per year [2]. Available capture technologies are predominantly based on the use of intermediate materials, namely solvents that enhance the separation efficiency by selectively dissolving CO2 [3]. Amine-based organic compounds are among the most common solvents employed in the widely utilized chemical absorption process. The globally observed preference towards solvent-based absorption is largely because the technology is well established, the conditions for both absorption and solvent regeneration are relatively easy to meet and the process can be easily retrofitted onto existing plants [4]. Major downsides involve the increased energy required for solvent regeneration, environmental aspects associated with the toxicity of the solvent and solvent derivatives, the presence of contaminants that affect the solvent performance and lead to solvent degradation and the corrosion of equipment caused by the solvent itself.
Clearly, such shortcomings require significant advances in solvent performance, supported by the additional introduction of considerable improvements in the overall process systems that emit and capture CO2. Despite previously intense research effort in this direction, solvent-based absorption processes are reported to introduce a cost penalty of over 40% to the operation of the plant [2]. Approximately 70% of these costs are due to the use of thermal separation processes for solvent regeneration [4]. Such estimates bring the capture cost in the range of $52-89 (€36-62)/ton (Note: The original prices reported in [5] are $45-65 (€ 31-45)/ton of CO2 for a coal-fired power plant with a capacity of 900-300 MW in 2004. The above prices correspond to 2011 rates in U.S. dollars accounting for inflation and transformed into € using recent exchange rates) of CO2 [5], which is well above the current trading price (at €16.5 on 24-03-2011).The planned carbon tax in the UK is £16 (€18) in 2013 and £30 (€34) in 2020 (based on 2009 prices) [6]. Therefore, there is a lack of economic incentive in the industry to capture CO2 at the current high cost. A new technology towards breakthrough innovation in solvent based post-combustion CO2 capture for enhanced energy efficiency, improved cost effectiveness and increased process sustainability and environmental benefits is developed. Advances in the identification of highly performing solvents and solvent blends in CO2 absorption, the design of innovative separation equipment internals, and the development of optimal process configurations enable cost reductions of at least 20-30% per ton of CO2 captured. Such achievement can have a tremendous impact in several industrial applications such as gas-fired, coal-fired, and lignite-fired power plants as well as and quick-lime production plants where solvent based post-combustion CO2 absorption can become a viable solution.
The CAPSOL project adopts a holistic approach towards the fulfillment of the outlined goals accomplished through research and development at multiple levels within an integrated framework.
At the molecular level, the use of computer aided molecular design tools supported by accurate and adequately validated thermodynamic models enables the exhaustive investigation of the performance of multiple solvents and solvent blends in post-combustion CO2 absorption processes. The solvent blends are systematically assessed and rank-ordered against their performance towards the satisfaction of relevant process, economic, operability and sustainability criteria. The optimal solvents and solvent blends are expected to exhibit significantly better characteristics than currently used solvents in terms of energy requirements and overall environmental impact.
At the unit operations level, the design of innovative process configurations and column internals that are specifically tailored for the employed solvents enhance the efficiency of the absorption based separation. Advanced modeling and optimization tools in conjunction with thorough experimental procedures ensure the achievement of high mass transfer rates and optimal flow patterns.
At the plant level, the comprehensive analysis of the interactions among an existing power plant and the added solvent based post-combustion CO2 capture unit enables the optimal allocation of resources for improved energy savings and the efficient integration of the new CO2 capture process components. Several industrial applications in power production and chemicals manufacture are scheduled for comprehensive study, analysis, and evaluation thus resolving all related technical and engineering issues.
Therefore CAPSOL aims to address these challenges by seeking:
• Solvents and solvent blends of increased affinity towards CO2, reduced regeneration energy needs and environmentally benign characteristics,
• Absorption/ desorption configurations and packing materials of reduced capital cost, supporting operating conditions that facilitate the solvent-CO2 reaction and subsequent CO2 release.
• Improvements in CO2 emitting plants to facilitate the optimal integration with the capture units.
The targeted developments can have a tremendous impact in several industrial applications such as gas-fired, coal-fired, and lignite-fired power plants as well as quick-lime production plants where solvent based post-combustion CO2 absorption/desorption can become a viable solution.
Scientific Objectives
The above targets are approached through the use of advanced computer-aided methods and tools supporting the fast, cost-efficient, automated and accurate identification of potentially useful capture solvents and process systems. Few resulting solvents and process operating conditions indicating high performance are then verified in focused pilot plant experiments. The utilization of such methods and tools requires:
• The development of property predictive methods in the form of advanced thermodynamic models able to capture and model the highly non-ideal solvent-CO2-water interactions
• The development and implementation of computer-aided molecular design (CAMD) methods to investigate a very large number of potential CO2 capture solvent candidates in terms of thermodynamic, kinetic and sustainability properties.
• The development of conceptual and rigorous process models able to efficiently capture different solvent process interactions both at the level of absorption/desorption flowsheets and column packing materials.
• The development and utilization of systematic process integration and optimization tools for the investigation of overall cost-saving opportunities in CO2 emitting plant complexes including waste heat recovery and efficient resources management.
Technological Objectives
The scientific objectives facilitates in the achievement of the following technological objectives:
1) Develop optimally designed novel solvents, blends and absorption/desorption flowsheets that:
• Result in much less energy requirements compared to a 30 wt % MEA process ,
• Combine superior sustainability (e.g. environmental, safety etc.) properties, translating to a significant improvement in the eco-indicator and in the SHE (Safety-Health-Environmental) hazard assessment indicator.
• Facilitate minimum sensitivity to process variations and disturbances (e.g. impurities),
• Enable efficient operation under different pressure/temperature conditions (e.g. high pressure desorption).
• Resolve issues such as contaminants, degradation, removal of decomposition products, compression of CO2, water balance etc. with high efficiency.
2) Develop optimally designed absorption/desorption equipment that:
• Enables large reductions in the capital and operating expenses compared to a 30 wt % MEA process,
• Incorporates significant improvements in column packings including new structural (e.g. size, geometry etc.) and operating (e.g. flow, pressure drop, mass transfer etc.). characteristics of optimum performance that enable a reduction in the required energy.
• Maintain conditions that efficiently eliminate flooding, channelling, entrainment and foaming.
3) Integrate solvent-process CO2 capture plants with optimally retrofitted CO2 emitting plants including a supercritical lignite fired steam power plant, a modern supercritical hard-coal fired power plant, a natural gas fired combined cycle plant and a quicklime plant aiming to:
• Reduce the overall pre- and post-combustion process costs.
• Accomplish the targeted reductions by implementing methods for optimum plant-wide design and operation (e.g. total-site integration etc.) aiming at the utilisation of the cheapest waste heat available on the sites (e.g. condensing turbine outlet for power plants and industrial plants, as well as excess low-pressure steam for some industrial plants).
4) Pilot plant testing of the CAPSOL technology under operating condition encountered in practical applications ensures process stability and consistency.
References
[1] D’Alessandro D.M. Smit B., Long R.J. (2010), Angew. Chem. Int. Ed., 49, 6058-6082.
[2] ScienceDaily (2007), http://www.sciencedaily.com/releases/2007/11/071114163448.htm
[3] Mac Dowell N., Florin N., Buchard A., Hallett J., Galindo A., Jackson G., Adjiman C.S. Williams C.K. Shah N., Fennell P. (2010), Ener. Env. Sci., DOI: 10.1039/c004106h 3, 1645-1669
[4] Aaron D., Tsouris C. (2005), 40 (1), 3321-348.
[5] Klemes J., Bulatov I., Cockerill T. (2007), Comp. Chem. Eng., 31 (5-6), 445-455.
[6] Airlie, C., Carr, M. (2011), EU Carbon Falls as U.K. Tax Pushes Costs Above Osborne’s ‘Floor’, available in: http://www.bloomberg.com/news/2011-03-24/u-k-s-new-carbon-tax-is-higher-than-assumed-citigroup-says.html
Project Results:
CAPSOL Main Scientific and Technological Results
Molecular level advances
CAPSOL technology has approached the solution to the efficient CO2 capture process through advancements at various levels. At the molecular level, CAPSOL developed innovative computer aided molecular design based procedures supported by accurate and adequately validated thermodynamic models in order to enable the exhaustive investigation of the performance of multiple solvents and solvent blends in post-combustion CO2 absorption processes. The developments in thermodynamic modeling via group contribution methods and in computer aided molecular design tools for CO2 capture processes are presented.
Thermodynamic Models
In solvent design where a large number of molecular candidates needs to be assessed, group contribution (GC) approaches are an ideal tool. The molecules are deconstructed into distinct functional groups that characterize their chemical composition. The underlying assumption of such an approach is that these groups give rise to the same thermodynamic contribution independently of the molecule in which they appear. Once the parameters for a group have been determined via regression to experimental data then this group can be used as a building block to form a molecule. With appropriate use of the group contribution method the properties of the system of interest can be obtained even in cases where the thermodynamic behavior might be unknown but the parameters of the groups composing the system’s molecules are known. In this sense, group contribution methods are essentially predictive, since there is only a dependency on experimental data at the early stage of obtaining the group parameters from a set of selected systems (Figure 1).
A significant breakthrough in thermodynamic property modeling was made by showing for the first time that it is possible to develop a group contribution approach to represent the challenging phase and chemical equilibrium of CO2 + water + alkanolamine mixtures at different temperatures and pressures. This was achieved by proposing the use of implicit reaction models (i.e. by representing the reaction products via association sites) within the framework of the Stochastic Associating Fluid Theory with square well potentials or SAFT-γ SW equation of state. The concept of second-order groups was introduced for the first time in a SAFT-type group contribution equation of state to tackle the multifunctional nature of capture solvents. A large number of basic groups were derived. These form the essential building blocks for solvent design.
The quality of the models obtained with the novel group contribution models has been strictly verified through the comparison of the model predictions with experimental data obtained from literature or produced during the CAPSOL project. This demonstrates for the first time that the concept of implicit-models, initially developed in the context of molecular models, which consider the reaction products as neutral aggregates, can successfully be transferred to the group contribution framework; it can thus provide the basis for a fully predictive approach to the design of novel solvents for carbon capture. Implicit models also assist enormously the simulation of complex CO2 separation units. They greatly facilitate the modeling of a complex reaction mechanism in the column without the need for individual material balances for all intermediate molecular or electrolyte species that appear.
A carefully designed experimental schedule has been executed within the CAPSOL project in order to generate additional experimental data for targeted solvents that showed good potential in increasing the separation efficiency in CO2 capture units. Equilibrium solubility of CO2 in aqueous solutions of amines and amine blends measurements have been performed in a small scale absorption column equipped with packing material. The experiments justified the major trends in the behavior of the amine solutions and especially those consisted of a mixture of amines.
Such promising results have been utilized to develop a predictive framework to model (i) strong electrolytes with SAFT-γ SW and (ii) weak electrolytes with SAFT-γ SW. The treatment of weak and non-spherical electrolytes required new theoretical developments, which were implemented in the SAFT-γ SW software to create SAFT-γE. Explicit models consider the reaction products as independent ionic species. A procedure for the derivation of explicit-product models which makes use of the predictive capabilities of the implicit-product models developed to date has been set in place. In particular, reliable speciation data are generated as a basis for the modeling of reaction equilibrium. In other words, the strategy is a two-step approach to solvent selection, in which implicit-product models are first used to identify promising solvent candidates, and the best options are then investigated using explicit-product models that provide a more detailed description of mixture behavior, and of the performance of the capture process. In this regard a new version of the theory has been presented, the SAFT-γE EoS. This new EoS also takes into account electrostatic interactions, and is therefore capable of explicitly describing the ionic species obtained as reaction products in aqueous mixtures of alkanolamines and carbon dioxide.
Solvent Selection Methodology
A Computer Aided Molecular Design (CAMD) framework is developed which is subsequently used to design and select novel solvents. Intense research efforts reported in recent years are predominantly based on lab and pilot-scale experiments to select solvents which may potentially improve the overall performance of absorption/desorption CO2 capture. However, this is very challenging due to a) the highly non-ideal solvent-CO2-water chemical interactions, b) the countless combinations of potential capture solvent and blend candidates, and c) the need for combined consideration of numerous thermodynamic, kinetic and sustainability properties as performance criteria prior to selecting solvents with optimum capture features. CAMD can help address these challenges and have been successful in supporting the synthesis of molecules with desired physical, chemical and environmental properties in non-CO2 separations. Despite extensive developments in CAMD methods, few recent works reported before CAPSOL their utilization in the design of CO2 capture solvents or mixtures for chemical and physical absorption using the Statistical Associating Fluid Theory with potentials of Variable Range (SAFT-VR) and for physical absorption using the Perturbed Chain Polar Statistical Associating Fluid Theory (PCP-SAFT). While these approaches enable an accurate and reliable determination of solvent-process vapour-liquid equilibria, the set of few solvents screened to date will be further expanded as research efforts extend the rigorous predictive capabilities of SAFT-based models towards additional molecular structures.
In CAPSOL, the use of an optimization-based CAMD method whose steps are shown in the schematic of Figure 2 is employed to select post-combustion CO2 capture solvents of optimum performance in molecular and mixture properties associated with thermodynamics, kinetics and sustainability. For the first time in published literature numerous properties were considered as performance criteria reflecting solvent characteristics based on thermodynamic (e.g. vapor pressure, CO2 solubility etc.), kinetic (solvent basicity, steric hindrance etc.) and sustainability (e.g. health and safety hazard, life cycle assessment etc.) behavior. The simultaneous consideration of properties selected to capture the molecular chemistry effects on the absorption/desorption process compensates for the utilization of simpler models and ensures the selection of fewer but more effective solvents. Different functionalities of the employed CAMD method were used both to design optimum, novel molecular structures and to screen a dataset of commercially available amine solvents suitable for CO2 capture. Several models were considered simultaneously for the prediction of the properties used as solvent performance criteria in order to account for uncertainty in the selection procedure. The obtained results (presented above) revealed interesting structure-property trade-offs and pointed to commercial molecules which have very recently been considered or have yet to be employed as capture solvents.
The aim of the work has been further extended to include the investigation of the performance of binary mixtures that appear to be promising as CO2 capture solvents. In this context a broad range of mixture compositions (i.e. structure of each component in the mixture) and concentration (i.e. amount of each component in the mixture) is considered. Note that this is the first time that such an approach has been attempted. The literature review regarding mixtures utilized as CO2 capture solvents indicates that few options were previously examined using ad-hoc selection approaches. Instead, this CAPSOL proposes a systematic selection approach involving several decision making stages. Initially, we determine a set of mixture properties as selection criteria and investigate the ability of several different models to provide valid property predictions compared to experimental data. The considered criteria reflect the impact of different mixture chemistries on important absorption/desorption process characteristics associated with efficient CO2 capture. They are implemented in several selection stages in order to refine a rich initial set of mixtures and to identify those that may be considered as capture candidates. A multi-criteria assessment methodology is combined with a systematic uncertainty quantification approach to unveil important performance trade-offs in view of the non-ideal solvent-CO2 interactions. To highlight the impact of uncertainty in the mixture selection procedure we compare a case where uncertainty is not considered during the selection with a case where uncertainty is considered. The two sets obtained in both cases indicate differences in both mixture components and performance characteristics. It is observed that the consideration of uncertainty in the selection procedure results in a more coherent set of CO2 capture candidates. Further analysis of the results indicates that several highly-performing mixtures identified in the two cases share one of the two components, while the impact of each component in the mixture performance is also investigated.
Overall a database of 459 molecular structures was generated from the implementation of CAMD. 126 amines were found in publicly available databases or previously considered as CO2 capture solvents in absorption/desorption systems, while 333 solvents are potential novel structures. All the molecules were evaluated and rank-ordered using a performance index which unifies all the properties considered as solvent selection and design criteria. The obtained results were broken down into 4 classes (categories) of molecules based on their performance ranking.
• The 1st class considers the top 10 structures of the 25 molecules previously employed as CO2 capture solvents (Reference class).
• The 2nd class considers the top 10 molecules resulting from rank-ordering the 459 available molecules, denoted as class of Designed molecules although it also includes the 126 amines found in databases.
• The 3rd class considers only the top 10 structures of the 126 solvents found in databases, denoted as class of commercially available molecules.
• The 4th class focuses only in the top 10 alkanolamines among the 126 molecules denoted as the Commercial Alkanolamines class.
The obtained results depicted in Figure 3 clearly indicate that the class of designed molecules performs better than all other classes (the lower the aggregate performance index the more preferable the solvent is), whereas commercially available molecules exist that have yet to be considered as CO2 capture solvents and perform better than available solvents. Monoethanolamine (MEA), which the most commonly used solvent in amine based CO2 capture processes exhibits a lower score than most of the other selected solvents. Figure 4 shows the comparative performance of some selected solvents in properties (molecular volume, Vm, vapor pressure, Pvp, surface tension, σ, liquid heat capacity, Cp, viscosity, n, CO2 solubility, RED, basicity, pKa) used to form the aggregate performance criterion.
In conclusion, CAPSOL advances in both group contribution thermodynamic modeling and CAMD enables the identification of a small set of molecules that exhibit high performance in terms of desired properties associated with the capture process. The list of molecules extends the current state-of-the-art at it includes molecules that have not yet been researched in CO2 capture studies. Therefore, the list of highly performing molecules includes some that have been identified by other researchers as potential good colvent candidates.
Unit operations level advances
At the unit operations level, CAPSOL developed innovative absorption process models of variable resolution and phenomena descriptive capability that were subsequently used in the identification of highly performing process flowsheets and column internals. Performance was assessed by considering a set of economic, sustainability and operational criteria. The presentation of the developments in process models, optimal design of process flowsheets and column internals is described in greater detail.
Process Model Development
Process models are essential elements for the identification by design of highly performing process flowsheets in post-combustion CO2 capture. Therefore, the development of a framework for the efficient modeling of reactive absorption and desorption processes for the separation of CO2 from flue gas with the help of aqueous amine or other type of solutions becomes of paramount importance. Such a framework is consisted of a complete suite of mathematical models that would enable the description of all underlying physical and chemical phenomena that occur in reactive absorption and desorption (stripping) columns and further ensure good accuracy of predictions over a large range of operating conditions. However, models of different resolution and degree of detail are required for the variety of tasks in which process models are used. Flowsheet configuration design require conceptual models that capture the main process trends whereas more detailed and rigorous models are more suitable for optimization of operating conditions, packing structure optimization, and control system design. Conceptual models may be quite simple and concise in structure but must be accurate within a reasonable limit. More rigorous models require the careful identification and estimation of multiple model parameters associated with the phenomena description but must also provide the necessary flexibility in order to enable the realization of complex column configurations. Concurrently, models should be computationally efficient so that they can allow the simultaneous optimization of large column trains and sequences in the course of complex flowsheets synthesis. Computational efficiency is mainly judged based on solution effort and convergence robustness properties.
Flowsheet synthesis and process design
A generalized framework is proposed for the optimal design of post-combustion CO2 capture processes based on a systemic and flexible equilibrium separation model that employs orthogonal collocation on finite elements (OCFE) techniques. Within this context, a column section of adaptive separation capability and functionality serves as the fundamental structural block for the identification of efficient separation schemes. Separation column sections in combination with heat transfer blocks as well as stream splitters and mixers enable the generation and evaluation of alternative flowsheet configurations within a non-linear optimization program (Figure 5). The main objectives for the flowsheet evaluation involve separation and thermal efficiency that eventually impact the economics of the overall process. The proposed design framework was used for the optimal design of alternative flowsheet configurations for the separation of CO2 from a flue gas stream using amine solutions identified by the CAMD procedure. The achieved performance was compared against the performance obtained by a 30% weight MEA capture plant.
The simultaneous assessment and evaluation of five alternative process flowsheet configurations and four different solvents for solvent based post combustion CO2 capture processes is carried out in this work. The various flowsheets are generated using a generalized process design framework with the concept of maximizing the driving forces in the separation units and thus the intensification of the process. Design optimization results for a CO2 capture plant treating a flue gas from a quicklime plant reveals that:
• Reductions in the range of 30-35% in the annual expenses can be achieved when 2-Amino-2-methyl-1-propanol (AMP) is used as the CO2 capture solvent.
• Absorber intercooling enhances the process behavior significantly and leads to a subsequent reduction of both capital and operating expenses.
• Reduced energy demand was achieved (1.79 GJ/ton CO2) using AMP and a combination of stripper stream redistribution and absorber intercooling. Previously reported values from the CESAR project include 2.9 GJ/ton CO2 using absorber intercooling.
• Using a combination of stream redistribution in the stripper and intercooling of the absorber, process cost reductions in the range of 15-35% can be attained, depending on the employed solvent.
Sustainability
Despite the development of several general sustainability indicator frameworks in literature, there is still a need to adjust these and/or develop new indicators on a case by case basis. The overall goal of CAPSOL has been to develop a framework of sustainability indicators suitable for assessing the different solvents and process schemes for post combustion CO2 capture, focusing on the holistic environmental benefit for normal process operation through a Life Cycle Assessment (LCA) approach and substance/process Environmental Health and Safety (EHS) hazard identification for evaluation of the harm potential in accidental scenarios. The framework comprises two phases of assessment at the level of basic design, substance and process level assessment. Both assessment phases are based on methods that are well established in literature. The framework has been modified and extended as more information became available at subsequent solvent/process design levels. For the purpose of testing the methodology and concepts proposed, a reference set of solvents was compiled and assessed on a substance level. The substance level assessment performed included the application of two EHS hazard analysis methods, the EHS method and Inherent Safety Index (ISI) method. LCA assessment included obtaining the Cumulative Energy Demand (CED) which is a resource oriented indicator, the Global Warming Potential (GWP) and the Eco-Indicator (EI) 99 which are both damage oriented indicators. Among the open issues to be investigated are the mechanism of dealing with data gaps and increasing the flexibility of different methods, estimating the LCA indicators through reaction chemistry and the estimation of the rates of solvent degradation and equipment corrosion.
The sustainability assessment shows that AMP is a superior solvent from both an EHS and LCA point of view compared to the other solvents in the test group. However AMP suffers from slower kinetics and therefore, it would be more comprehensive to conduct further assessment based on a rate based model, so that its disadvantages are more apparent. Two waste treatment scenarios have been compared to account for solvent loss through degradation and to reduce the impact of degradation products formed. The reclaimer scenario that involves the regeneration of the degraded amine was shown to give better performance from an LCA perspective (5-15% improvement in different LCA metrics), whereas the EHS assessment was mostly insensitive to the change as there are no significant differences within the process boundaries between both cases. It is important to consider degradation products, although the parent amine will still dominate the results of most EHS metrics, due to its higher mass in the system.
Control and operations
The optimization-based approach in the calculation of efficient CO2 capture process plants aims at the simultaneous determination of the flowsheet configuration and the equipment design parameters. However, the capture plant is required to operate under variable process conditions due to either production level shifts or the influence of unexpected process disturbances. In order to ensure the satisfaction of the operating and economic specifications for the CO2 capture plant a reliable and efficient control system should be designed that would be able to alleviate the effects of disturbances on the process objectives. The plantwide control structure must be then design and its performance investigated. To this end, a set of candidate flowsheet and control structure configurations must be analyzed under the presence of multiple and large in magnitude disturbances that are likely to affect process operation and process economics. It is generally accepted that the economic result of a process system may be significantly altered if the process systems failed to quickly recover from the influence of a disturbance.
Specifically, a capture system must compensate for variable flue gas volumetric flowrates, concentration and temperature, changes in the kinetics of the reactions, uncertainty in the thermodynamic property prediction, and malfunction of the various equipment that form the overall system. Such changes may occur with different intensity and frequency. The influence of variability in the operating environment will affect the amount of CO2 capture by the system, and the conditions in the unit operations that subsequently influence the energy requirements for the capture of CO2 and the economics of the plant (Figure 6). It has been exhibited within the CAPSOL project that a specific solvent capture system that recorded good economic performance at the nominal operating conditions may have its performance drastically deteriorating under the presence of commonly occurring disturbances. It is then suggested that the evaluation of process flowsheets incorporating commercial or novel solvents should consider the impact of the disturbances. Therefore, the design and implementation of a capable control system is of paramount importance for the efficient operation of a capture plant.
The approach that is employed involves the evaluation and screening of alternative process flowsheet and control structure configurations in a rigorous, effective and systematic way. It utilizes an effective decomposition of the process and control system design tasks, which in sequence allows the enhancement of the process controllability properties. The quality of the steady state behavior in response to the detrimental effects of multiple simultaneous process disturbances and model parameter variations is an essential prerequisite for good economic performance during operation. Disturbance rejection sensitivity for a candidate process flowsheet is investigated in conjunction with decisions encompassing plantwide control objectives for the process. The objectives reflect the hierarchy in achieving certain targets and exploiting available resources for control purposes. The controllability framework enables the evaluation of control strategies outlined by the weighting of the objectives and the input-output structure of the candidate controller. The method employs rigorous and detailed mathematical models that intend to capture nonlinear effects arising from the physical system and potentially intensified by the interactions of multiple and simultaneously acting disturbances. Disturbance directionality and magnitude are two key factors that are thoroughly investigated and explored. The calculation of a static controllability performance index representative of the static disturbance rejection characteristics becomes the basis for the assessment and ranking of the alternative flowsheets and control structures.
Dynamic characteristics of the candidate process design play the most dominant role in the achievable dynamic performance of the control system. The performance of the control system is inherently affected by the dynamics of the designed process. Process dynamic characteristics are influenced not only by process design decisions but also by model parameters variations. Sensitivity analysis determines the margins of the process design from undesired dynamic behavior (e.g. unstable, undesired oscillatory or sluggish response) at the presence of uncertainty. Nonlinear process models act as the basic tools for the identification of the process dynamic components during a disturbance scenario that involves multiple disturbances of finite magnitude.
The modification of the design decision variables using nonlinear sensitivity information becomes an additional instrument for the design engineer in order to improve the desired static and dynamic properties of the plant. Flowsheet design parameters are associated either with the structure of the flowsheet (e.g. selection of units, connectivity of units and so forth) or the equipment design specifications. The disturbance rejection exercises and their influence on the static and dynamic controllability indices reveal the relationship among performance indicators and design parameters. Proper modification of the design parameters utilizing nonlinear sensitivity analysis calculations can enhance the static and dynamic controllability properties of the design while maintaining the economic attractiveness of the final design. The complete design procedure is outlined in Figure 7.
Column internals design
The selection of suitable column internals is an important prerequisite for an optimum operation of gas-liquid separation processes. The removal of CO2 from gas mixtures realized by absorption into a liquid solvent is usually performed in columns filled with structured packings. Standard structured packings have a corrugation angle of 45 degrees or 60 degrees. Using different possible corrugation angles may result in better column performance. The corresponding analysis can be done with model-based simulations.
The aim of CAPSOL project was to develop an integrated modeling framework for the complementary application of three modeling approaches, namely, Computational Fluid Dynamics (CFD), Hydrodynamic Analogy (HA) and the Rate-based Approach (RBA). This framework should be used to facilitate design of innovative internals and equipment for solvent-based CO2 separations. The characteristics of the models in terms of model accuracy and flow complexity as well as the information flow from one model realization to the others is shown in Figure 8.
Computational fluid dynamics models aim at describing the flow characteristics in a representative packing element. It is assumed that the element is repeated in order to represent the entire structure. The model calculates the flow pattern and enables the prediction of the dry pressure drop in structured packing. The model has been validated using experimental data in equivalent units.
Hydrodynamic analogies models represent real complex two-phase flow in a packing as a combination of geometrically simpler flow patterns (Figure 9). In the physical model the packing is represented as a bundle of parallel inclined channels with identical cross section. The number of the channels as well as their diameter is determined from the packing surface area and corrugation geometry. The gas flow behaviour depends on the operating conditions and varies from laminar to fully developed turbulent flow. The liquid flows counter-currently to the gas flow in form of laminar films over the inner surface of the channels. Additionally, a uniform distribution of the both phases in radial direction is assumed, i.e. no maldistribution is taken into account in the model. The required parameter for the proper description of the gas-phase turbulence in the HA model was estimated using CFD analysis of single-phase gas flow through structured packing.
Rate-based models consider the entire separation column as a series of stages in which mass transfer, reaction kinetics and equilibrium, and fluid dynamics (Figure 10). Diffusion and mass transfer coefficients as well as hold-up and interfacial area are being estimated through the “virtual simulated experiments” using CFD and HA models. Rate-based models can then determine the required packing height for a given absorption rate.
The integrated modeling framework for simulation of innovative structured packings for the CO2 absorption has been utilized in MEA and other CAPSOL solvent solutions. The simulated procedure achieved the investigation of the influence of corrugation angle of structured packings on the separation efficiency and dry pressure drop.
Modeling of gas-liquid separation processes usually requires experimentally determined parameters such as mass transfer coefficients, which cannot be determined without expensive experimental work. A novel modeling approach based on hydrodynamic analogies (HA) has recently been developed and successfully tested for distillation units equipped with structured corrugated sheet packings. The HA approach is an alternative way to describe hydrodynamics and transport phenomena n processes, in which exact location of the phase boundaries is hardly possible. Contrary to the traditional models based on the film theory, separation columns can be described without using mass transfer coefficient correlations.
In CAPSOL, the HA approach was applied to carbon dioxide absorption into aqueous monoethanolamine. The composition profiles were determined in an absorption column filled with structured packings and subsequently checked against experimental data. The HA model has been For the gas phase, concentrations at the top and bottom were measured. For the liquid phase, full concentration profiles were determined.
Column packing manufacturing
Post-combustion capture plants, as considered in the CAPSOL project, apply absorption and desorption technology to separate CO2 from flue gas. The project focused on the absorption of CO2 into amine based solvents followed by stripping of CO2 in a desorber, which up to date is considered to be the most promising technology. Hence, columns for absorption and desorption are involved that apply these internals. It is well known that choosing the right technology for mass transfer internals is very important, as their specific characteristics in terms of pressure drop, hydraulic and separation performance are significant factors for operating and investment costs of CO2 capture plants.
The most promising structured packing characteristic to be optimized for CO2-absorption purposes was identified to be the specific pressure drop. A lower specific pressure drop will lead to reduced energy consumption of the flue gas blower. The predominant modification method to reduce the pressure drop is to increase the inclination angle of the oppositely oriented flow channels of corrugated sheets structured packings are made of. CFD simulations were performed and the diagram shown in Figure 11 could be derived. The diagram shows the dry pressure drop depending on the inclination angle for various F-factors (column loading factor).
As can be seen, at inclination angles above 70°, the pressure drop is only decreasing marginal. At this point it was decided to manufacture a packing with an inclination angle of 75° by Julius Montz GmbH (MONTZ) (Figure 12). This packing would show a very low pressure drop, while the film flow at the packing surface could still persist.
Fluid dynamic experiments at the University of Paderborn (UPB) confirmed the drastic reduction of the pressure drop for both dry and irrigated conditions. Figure 13 shows a comparison of the measured dry pressure drop for a packing with 45° and 75° inclination angle. Figure 14 shows the same comparison at irrigated conditions. At F-factors between 2 and 3 Pa0,5 the pressure drop can be reduced by 90 to 97%.
In addition, experiments were conducted to evaluate the absorption efficiency using this new packing. As expected, the absorption rate is slightly decreased for the new packing geometry with the steeper inclination angle. However, this reduction does not place a critical burden in the associated capital costs of the capture plant and is therefore considered a reasonable compromise.
Pilot plant testing
During the CAPSOL project a pilot plant for the absorption and desorption of CO2 was built at the University of Paderborn.
The pilot plant (Figures 15 to 20) is conceived as a multi-purpose plant. Experiments can be carried out in four operation modes: batch absorption, batch desorption, closed loop and fluid dynamics. In order to enable all four operation modes, the plant comprises two glass columns, one with an inner diameter (ID) of 100 mm and another with an ID of 300 mm. Both columns are about 5 m high, and each column includes a packed section of about 3 m height. The smaller column is to be predominantly used for absorption. Due to the small diameter and consequently considerable wall effects, this column is not suitable for fluid dynamic experiments. In contrast, the bigger column can be used both for desorption and for fluid dynamic experiments. To realize a closed loop mode, both columns are to be linked. The absorption (small) column can be operated at F-factors varying between 1 and 3.5 Pa0,5 and liquid loads between 10 and 60 m3m 2h 1. In desorption mode, the large column is operated with the same liquid loads as the absorption column. In fluid dynamic mode, it can be operated at F-factors varying between 1 and 4 Pa0,5 and liquid loads between 20 and 90 m3m 2h 1. A detailed flow sheet of the plant is given in Figure 20.
Before the plant was used to test the new CAPSOL packing and solvent it was validated by performing fluid dynamic and absorption experiments. To this end, Figure 21 shows measured values of the dry pressure drop depending on the F-factor. Measurements at UPB using both columns are compared to measurements by Julius Montz GmbH using a column with an inner diameter of 600 mm. It can be seen that UPB measurements at the bigger column (diameter of 300 mm) agree well with the values obtained by Montz.
Measurements of the pressure drop of irrigated packing were carried out at liquid loads of 10, 20 and 50 m³m 2h 1. For low liquid loads, our measurements showed good agreement with the values by Montz (see Figure 22). The slight deviation can be explained by the clearly smaller diameter of our column compared to the column at Montz. A higher deviation in Figure 16 at a liquid load of 50 m3m 2h 1 is most likely due to water accumulation in the pressure measuring system resulting in measurement errors.
Based on these tests, it can be concluded that the bigger column at UPB is applicable for studying fluid dynamics of different packings.
Additionally, absorption experiments with monoethanolamine were performed. Three experiments A1 to A3 (summarized in Table 1) were carried out with liquid loads of 17 m3m 2h 1 and F-factors of about 1.6 Pa0.5. The solvent was a 14 % wt aqueous MEA solution. The inlet CO2 mole fraction varied between 0.045 and 0.091.
Figure 23 shows the gas-phase CO2 concentration profiles and Figure 24 the temperature profiles along the column height.
As the profiles are showing reasonable trends, we can conclude, that the pilot plant can be used with confidence for thorough experimentation in the field of packing and solvent design.
Plant level advances
Several industrial plants in power generation have been considered for the integration of CO2 capture plant units. The four selected reference power plants are:
• Supercritical lignite fired steam power plant of a power output of 650 MWe gross.
• Supercritical bituminous coal fired power plant of a power output of 650 MWe gross.
• Natural gas fired combined cycle of 420 MWe.
• Quicklime production plant.
The 650 MW bituminous plant is based in the CESAR WP2 Deliverable D2.3.1 – “Baseline Powerplant Documents”
(http://www.co2cesar.eu/downloadables/Deliverables%20Public%20Summaries/CESAR-D2.3.1-APPROVED-Baseline%20Power%20Plants%20Documents%20PUBLIC%20SUMMARY-2010.03.26.pdf) .
The natural gas fired combined cycle of 420 MWe from the Scottish Power report whereas the 650 MW lignite fired steam power plant as well as the quick lime plant are new reference plants for the CAPSOL project.
The framework describes general technical and economic assumptions and a possible procedure for evaluation of different CO2 capture technologies both on quantitative evaluation parameters such as break-even electricity cost, specific CO2 emission avoidance cost etc. and on 18 different qualitative evaluation parameters. The assessment approach described here is aligned with the methodology being used in other FP7 projects through a joint working panel known as the European Benchmarking Task Force, whose activities are reported under CESAR WP2.4 (http://www.co2cesar.eu/downloadables/Deliverables%20Public/CESAR-D2.4.1-APPROVED-EBTF%20Common%20Framework%20Definition%20Document%202009.08.28.pdf).
Heat Integration
Lignite Fired Power Plant: The 650 MWe super-critical lignite-fired power plant with a CO2 capture process has been considered, where the capture unit has been in two variations: operating with MEA and CAPSOL capture system. When the CO2 capture unit with MEA is simply added to the plant using directly steam extracted from the turbine train for reboiler heating, the power generation reduction (power penalty) of the plant is 97.8 MWe. This is equivalent to 15 % comparing the non-optimized lignite power plant with carbon capture and the standalone lignite power plant. The cooling requirement in this case is 760.9 MW.
The proposed heat integration options reduce the steam extraction from the turbine for condensate return heating, and reduce the power penalty of the turbine island. The integrated process generates 577.1 MWe of power and requires 654.0 MWth of cooling utility. The power generation increases by 24.8 MWe, while the cooling demand of this integrated process is reduced by 106.9 MWth. The power generation penalty is 11.2 % comparing the heat integrated lignite power plant with carbon capture and standalone lignite power plant without carbon capture unit. As a result, the heat integration helps in reducing the power penalty from CO2 capture by 15-11.2 = 3.8 %.
The revenue from gross power generation is equivalent to an average of € 379.1 x 106 /y. However, the process integration options are able to save € 25.6 x 106 /y of utility cost. The CAPSOL capture system has also been evaluated, where the heat integration is able to save 5.39 MWe gross power. The cooling demand of the carbon capture plant with the CAPSOL technology increases by 404.7 MW, while the gross power penalty reduces to 10.40 %.
Coal Fired Power Plant: The nominal capacity of the plant is 650 MW electricity generation. The standalone power plant needs only a cooling utility for 624.7 MW and adding the MEA based CO2 capture increases that to 655.8 MW. Several heat integration options have been identified and implemented.
Adding the capture unit to the standalone coal power plant introduces power penalty of 91.9 MW (14.1 % of the nominal capacity). The Process Integration measures reduce the penalty to 10.4 % (3.7 % saving). For the CAPSOL capture system the process integration options are able to save € 9.7 x 106 /y of utility cost. The gross power output increases by 8.46 MWe, which is equivalent to reducing the power penalty to 9.05 % (14.1-9.05 = 5.05 % saving) of the nominal plant rating.
Gas Fired Power Plant: The nominal power generation of the plant is 423.5 MW. The total minimum cooling demand for the stand-alone power plant and the one with MEA CO2 capture unit is found to be 123.8 MW and 333.2 MW, respectively. Process modification options have been identified for reducing the energy requirement and the power penalty.
The power penalty due to the steam extraction for powering the CO2 capture is 30.5 MW (7.2 % of the nominal capacity), which is equivalent to an average of € 20 x 106 /y. The process integration options are able to save € 62.89 x 106 /y of utility cost.
The CAPSOL capture system is considered in the last part of the study. The gross power output increases by 5.60 MWe, as result of the integration which equivalent to 5.89 % of power penalty. The total cooling demands of the CAPSOL capture plant increased by 826.7 MWth.
Quicklime Plant: The quicklime plant is a simpler one. There is only one viable option for heat integration related to the utilization of the waste heat from the operation of Ca(OH)2 production from CaO. This can be utilized by generating steam with thermal load of 969 kW. A portion of this waste heat can be exploited within the CO2 capture process in order to preheat the rich stream exiting the absorption column and heading to the stripper.
Conclusions
CAPSOL technology enables the systematic design of solvent and solvent blends based on Computer Aided Molecular Design tools that employ accurate group contribution thermodynamic property prediction models and multi-criteria optimization techniques. The process performance of the identified new solvents and solvent blends against economic, sustainability and other environmental criteria is effectively utilized for the development of process flowsheet configuration of improved ability to reduce the energetic requirements of the CO2 capture process. A multi-scale modeling sequence is at the center of a rigorous procedure to unveil the complex flow pattern and transfer phenomena within the column internals and optimize the geometric characteristics of the packing structure. The CAPSOL capture plant consisted of the preferred solvent, the optimal flowsheet configuration, and the optimized structured packing has been integrated thermally with existing power plant in order to further reduce the overall energetic requirements.
Potential Impact:
CAPSOL Impact of Results
The CAPSOL impact can be characterized by major contributions at two distinct levels. The first level involves the development of novel methodologies in thermodynamic property model based on group contribution, computer aided molecular design for solvent mixtures, process flowsheet synthesis and design optimization utilizing flexible process models, and the multi-scale modeling for the optimization of the geometric features of structured packing. The second level of impact involves the development of new technological advances in solvent based post combustion CO2 capture through the implementation of pre-existing methods and CAPSOL developed methods.
A significant breakthrough in thermodynamic property modeling was made by showing for the first time that it is possible to develop a group contribution approach to represent the challenging phase and chemical equilibrium of CO2 + water + alkanolamine mixtures at different temperatures and pressures. This was achieved through the use of implicit reaction models (i.e. by representing the reaction products via association sites) within the framework of the Stochastic Associating Fluid Theory with square well potentials or SAFT-γ SW equation of state. The concept of second-order groups was introduced for the first time in a SAFT-type group contribution equation of state to tackle the multifunctional nature of capture solvents. A large number of interaction parameters for basic groups were derived. These form the essential building blocks for novel solvent design. Such developments not only assisted in the identification of novel solvents in CO2 capture but also set the ground for extending property prediction for a vast number of applications in process industry such as separations (e.g. extractive distillation) and catalytic reactions.
It is the first time that Computer Aided Molecular Design (CAMD) has been extended to include the investigation of the performance of binary mixtures that appear to be promising as CO2 capture solvents. In this context a broad range of mixture compositions (i.e. structure of each component in the mixture) and concentration (i.e. amount of each component in the mixture) is considered. Incorporating LCA (Life Cycle Analysis) and SHE (Safety-Health-Environmental) hazard assessment in the CAMD results has identified existing and newly proposed molecules with a potential reduction of the cradle-to-gate environmental impact up to 50% (e.g. in EcoIndicator units) and the hazard impact up to 20%. CAMD framework assisted by group contribution thermodynamic property prediction models and sustainability indices succeeded to identify multiple solvents and solvent blends with potentially superior performance than currently used solvent technologies.
A systematic process flowsheet synthesis and design optimization framework equipped with flexible and accurate process models achieved in obtaining process solutions that reduce in the range of 39% the annualized capture plant expenses and 56% the energy requirements. The investigation of sustainability in process solutions further reinforces the impact of the process design solution. This indicates a great boost in CO2 capture technology that can have a tremendous impact in industry and the environment. The reduction in the costs and energy implies that the attractiveness of solvent based CO2 capture increases with more industry adapting the technology for greater CO2 reductions.
Innovative column packing achieved a 97% reduction in pressure drop for the flue gas in the absorption column hence minimizing the energy requirements by the blowers. Considering the extremely large volumetric flow rate of the flue this is a significant factor in reducing the overall energy footprint. The new packing has generated a new type of product that has been subsequently used in the CAPSOL pilot plant successfully.
Heat integration in post combustion capture enables the efficient utilization by the capture plant of available thermal energy in the power plant. The main aim is the minimization of the overall penalty induced by CO2 capture. Extensive studies in the most commonly used type of power plants with fuels varying from natural gas, to lignite and coal have improved the CO2 capture penalty by 4 % - 10 %.
The main developments within CAPSOL project increase the viability of the post combustion CO2 capture process, which subsequently enhance the attractiveness of the technology. Solvent based CO2 capture remains one of the most suitable technologies for the mitigation of the hazardous effects of CO2. CAPSOL advances have added significantly to the benefits of the technology. It is therefore expected that more industrial players will seek CO2 capture technology that will increase investments and employment in manufacturing of columns and process equipment, engineering companies and process personnel.
Exploitation potential
CAPSOL created exploitation potential in several areas as outlined below.
Advanced solvents and blends.
A list of novel solvents with high potential has been identified as a result of CAPSOL project. Some of these solvents have never been studied before theoretically experimentally. Such outcome enriches knowledge in the field and sets the ground for opportunities in further exploring the potential use of these solvents or solvent blends in CO2 industrial applications. A plan to run experimental and simulation studies for these solvents will eventually validate their performance.
Property prediction models.
Process Systems Enterprise Ltd (PSE, www.psenterprise.com) has acquired the exclusive rights to the SAFT software developed at Imperial College London. As part of the collaboration agreement between PSE and Imperial College, the Imperial team is assisting PSE in developing applications for SAFT. PSE have recently developed a modelling tool for carbon capture and storage applications (gCCS, http://www.psenterprise.com/power/ccs/gccs.html) in which the SAFT equation of state provides key thermodynamic information for capture plants and carbon dioxide transmission. The gCCS tool was developed in collaboration with major players in the energy industry. The SAFT models within gCCS are currently based on a molecular representation of the components involved, as developed in previous work by the Imperial team. PSE are aware of the progress made in the CAPSOL project and CAPSOL partners and PSE will work together in the future to come to incorporate the group-based representation developed through the CAPSOL project. This will significantly improve the predictive capability of the approach and make the advances realized within CAPSOL accessible to all gCCS users, and more broadly all users of PSE products. The framework and theoretical advances achieved will also be used to extend the capabilities of the commercially-available version of SAFT, enabling for the first time the modeling of weak electrolytes within a group contribution equation of state.
Custom-made Computer-Aided Molecular Design Procedure and Software.
A new framework for the design of molecules of desired properties and optimal process performance has been the outcome of CAPSOL project. New improvements over previously developed software include the option for the design of specialized solvents and solvent blends for CO2 capture. The new advances in CAMD procedure will enable the extension of the application to other separation systems.
Multi-scale computer aided design of post-combustion CO2 plants.
A method has been available for multi-scale generation and multi-criteria assessment of process alternatives for solvent-based post-combustion CO2 capture that is computationally efficient and facilitates reliable screening in early phases of conceptual process design. The method should be able to generate and screen a large number of process alternatives with respect to diverse process features (i.e. solvent molecules, process layout and process operating conditions) and prioritize a reduced number of superior process alternatives to be tested in subsequent rigorous design stages. Notwithstanding the innovative features of this multi-scale approach, the method should also be easily compatible with existing design frameworks and software tools widely used by process system engineering companies. Therefore, the enhancement of existing screening tools in early phases of process design will be realized via the complementary, specialized features of the developed method.
Novel absorption/desorption flowsheet features
The development of innovative absorption/desorption flowsheets is a definite outcome of the research activities of CAPSOL project. Novel flowsheet configurations for various solvents that have not been tested thoroughly prior to CAPSOL project have been determined. Models of variable resolution assist in the quick but efficient screening among multiple flowsheet alternatives and options.
Novel or improved column equipment and process design
Partners involved in the development of improved column equipment (structured packings and non-separating internals, e.g. distributors) and process design will create relevant software tools that can be brought to a commercial level. To date, the available mass transfer contactor characteristics have so far basically been empirically derived from early performance tests of some standard applications not taking any specific and detailed characteristics of the application system itself into account. The methodology proposed in the CAPSOL project is different as it applies a model-based contactor optimization methodology including hydrodynamic analogy (HA) and computational fluid dynamics (CFD) models in order to propose a contactor designed for one specific application thereby taking all relevant and specific system parameters into consideration. The optimization work is focused on the main process parameters, primarily it tries to find the ideal compromise between separation performance and pressure loss characteristics.
Academic partners will use their software for educational, research, and training purposes, whereas industrial partners will utilize it for the design of innovative packings at reduced development time and cost.
Highlights: MONTZ has already designed a new commercial packing material product using the software tools.
Innovative power cycles and retrofitting options
New integrated flowsheet configurations incorporating CO2 capture plants in existing power plants will provide the exploitable item. Beneficiaries will mainly be the two industrial users in the consortium. In addition the academic partners will be able to promote the new knowledge to their industrial consortia.
Techno-economic studies
Detailed techno-economic studies on CO2 capture technology incorporation in lignite fired steam power plant, supercritical hard-coal fired power plant, natural gas fired combined cycle, quicklime production plant. A complete techno-economic study on solvent based CO2 capture technologies for a variety of power plants and other CO2 emitting plants provides the basis for exploitation of the acquired knowledge from the project.
Experimental and pilot plant data
Partners involved in the performing of pilot plant tests will set-up a database consisting of all measured data (e.g. temperature and concentration profiles; energy consumption values; degradation phenomena evaluation). A part of this data will be published in established scientific journals and presented on conferences thus providing a valuable input to industry and academia. The rest will be made available for industrial use. The University of Paderborn pilot plant will further be used for educational and training purposes.
SHE (Safety-Health-Environmental) hazard assessment method for CO2 capture
Various SHE hazard assessment methods have been developed for early stages of process design in the last two decades. In CAPSOL the most relevant features of these general methods for the solvent-based post-combustion CO2 capture have been screened and prioritized. The output is a list of applicable rules for SHE hazard assessment that can be either used as a stand-alone assessment method for preliminary screening in early design stages or integrated in risk assessment toolboxes for chemical and/or power plants. The promotion of the method and the potential for market exploitation will be first explored by the Safety & Environmental Technology group via its collaboration network with Swiss chemical and insurance companies and public offices for environment and energy.
Methods for estimation of supply chain relevant Life Cycle Assessment (LCA) impacts
LCA impacts often suffer from data gaps, especially with respect to supply chain information of chemicals required for a comprehensive cradle-to-gate impact analysis. For the solvent-based post-combustion CO2 capture, an important issue of data gaps refers to the supply chain of solvents considering also their degradation rate. Here, it is intended to provide a framework of complementary methods depending on available information and the required detail of design. The framework will mainly consist of QSAR correlations of LCA impacts to molecular structures, but will also account for decomposition of the supply chain, where more accurate information is available from existing data sources. The framework will focus on compatibility with existing LCA databases (e.g. Ecoinvent Center) and software tools (e.g. SimaPro®) to enhance the applicability of the framework by the process design and LCA community.
Optimization of structured packings
The CAPSOL exploitation potential lies in the methodology for optimising structured packings by adapting its geometric parameters according to the specific characteristics of the separation task. This is a fundamentally new approach compared to what the manufactures have been following within the last decades, and this approach may lead to significant process intensification for many applications. Even though the investigations have been carried out for one process example only (CO2 absorption with MEA), the methodology for the equipment optimization followed in the project is in principle transferable to diverse distillation and absorption applications. This offers vast opportunities to apply the methodology developed in the CAPSOL project for future optimization activity.
Flowsheet design for CO2 capture and heat integration for the quicklime process
Heat integration opportunities in quicklime production the energy released from the production line of another product. The production line of calcium hydroxide (slaked lime) is a net energy supplier. The heat released by this process can be efficiently utilized by a CO2 capture unit hence significantly reducing the energy penalty. This is a sort of symbiotic processes for the production of a useful product while the emissions from the initial process are being captured.
Educational and training activities
Several academic initiatives have been originated from CAPSOL project. Academic partners and those involved in scientist training will utilize the new results and technology for the enrichment of their educational programs and training modules. In particular, the experimental and pilot-plant set-up will be integrated in the education and training of students and researchers. The developed tools for the design optimization, the integration of the CO2 capture units within existing power plants will form the basis to further enhance the links of academic and research oriented organizations with industry
Dissemination of Results
The CAPSOL website (https://arquivo.pt/wayback/20180718123649/http://www.capsol-project.eu/) provides a comprehensive overview of the main achievements and results. The consortium will maintain the project website for at least five years after the completion of the project and update its contents with new publications and presentations arising from the project results. A specific section in the website will be devoted to the exploitation of the CAPSOL foreground knowledge by the project partners. CAPSOL project was part of the organizing team along with four other active FP7 projects (DemoCLoCk, iCap, Innocuous and IOLICAP) for the Carbon Capture and Storage technologies conference that took place in Antwerpen, Belgium, between May 28 - 29th, 2013.
The key instrument for the dissemination of the CAPSOL results was the preparation and publication of mainly scientific articles in peer reviewed journals and periodicals. The complete list of publication along with a designation regarding accessibility of the article in some form (publisher’s edition, post-refereed or pre-refereed) is given below:
1. Rodriguez J, N MacDowell, F Llovell, CS Adjiman, G Jackson, A Galindo, “Modelling the fluid phase behaviour of aqueous mixtures of multifunctional alkanolamines and carbon dioxide using transferable parameters with the SAFT-VR approach”, Molecular Physics: An International Journal at the Interface Between Chemistry and Physics, 110(11-12), 2012, 1325-1348. (access in public institutional repository)
2. Papadopoulos AI, M Stijepovicb, P Linke, P Seferlis, S Voutetakis, “Molecular Design of Working Fluid Mixtures for Organic Rankine Cycles”, Computer Aided Chemical Engineering, 32, 2012, 289-294. (access in public institutional repository)
3. Papadopoulos AI, Stijepovic M, Linke P, Seferlis P, Voutetakis S, “Multi-level Design and Selection of Optimum Working Fluids and ORC Systems for Power and Heat Cogeneration from Low Enthalpy Renewable Sources”, Computer Aided Chemical Engineering, 30, 2012, 66-70. (access in public institutional repository)
4. Yildirim O, AA Kiss, N Hueser, K Lessmann, EY Kenig, “Reactive absorption in chemical process industry: A review on current activities”, Chemical Engineering Journal, 213, 2012, 371-391. (access in public institutional repository)
5. Čuček L, PS Varbanov, JJ. Klemeš, Z Kravanja, “Potential of Total Site Process Integration for Balancing and Decreasing the Key Environmental Footprints”, Chemical Engineering Transactions, 29, 2013, 61-66. (access in publisher’s website)
6. Čuček L, PS Varbanov, JJ. Klemeš, Z Kravanja, “Reducing the Dimensionality of Criteria in Multi-Objective Optimisation of Biomass Energy Supply Chains”, Chemical Engineering Transactions, 29, 2013, 1261-1266. (access in publisher’s website)
7. Damartzis T, AI Papadopoulos, P Seferlis, “Generalized Framework for the Optimal Design of Solvent-Based Post-Combustion CO2 Capture Flowsheets”, Chemical Engineering Transactions, 35, 2013, 1177-1182. (access in publisher’s website)
8. Kakaras EK, AK Koumanakos, AF Doukelis, “Greek Lignite-Fired Power Plants with CO2 Capture for the Electricity Generation Sector”, Chemical Engineering Transactions, 35, 2013, 331-336. (access in publisher’s website)
9. Chremos A, E Forte, V Papaioannou, A Galindo, G Jackson, CS. Adjiman, “Modelling the Fluid Phase Behaviour of Multifunctional Alkanolamines and Carbon Dioxide Using the SAFT-γ Approach”, Chemical Engineering Transactions, 35, 2013, 427-432. (access in publisher’s website)
10. Pan M, Bulatov I, Smith R, “New MILP-based iterative approach for retrofitting heat exchanger networks with conventional network structure modifications”, Chemical Engineering Science, 104, 2013, 498-524. (access in public institutional repository)
11. Pan M, Bulatov I, Smith R, “Intensifying heat transfer for retrofitting heat exchanger networks with topology modifications”, Computer Aided Chemical Engineering, 32, 2013, 307-312. (access in public institutional repository)
12. Pan M, Bulatov I, Smith R, “Heat Transfer Intensified Techniques for Retrofitting Heat Exchanger Networks in Practical Implementation”, Chemical Engineering Transactions, 35, 2013, 1189-1194. (access in publisher’s website)
13. Papadopoulos AI, Stijepovic M, Linke P, Seferlis P, Voutetakis S, Toward Optimum Working Fluid Mixtures for Organic Rankine Cycles using Molecular Design and Sensitivity Analysis, Industrial and Engineering Chemistry Research, 52, 2013, 12116-12133. (access in public institutional repository)
14. Yazgi M, EY Kenig, “Hydrodynamic-analogy-based modelling of CO2 capture by aqueous monoethanolamine”, Chemical Engineering Transactions, 35, 2013, 349-354. (access in publisher’s website)
15. Damartzis T, Papadopoulos AI, Seferlis P, “Optimum Synthesis of Solvent-Based Post-Combustion CO2 Capture Flowsheets through a Generalized Modeling Framework”, Clean Technologies and Environmental Policy, 16(7), 2014, 1363-1380. (access in public institutional repository)
16. Papadopoulos AI, Badr S, Chremos A, Forte E, Zarogiannis T, Seferlis P, Papadokonstantakis S, Adjiman CS, Galindo A, Jackson G, “Efficient Screening and Selection of Post-combustion CO2 Capture Solvents”, Chemical Engineering Transactions, 39, 2014, 211-216. (access in publisher’s website)
17. Damartzis T, Kouneli A, Papadopoulos AI, Seferlis P, Dimitriadis G, Vlachopoulos G, “Optimal Design of Solvent Based Post Combustion CO2 Capture Processes in Quicklime Plants”, Chemical Engineering Transactions, 39, 2014, 1327-1332. (access in publisher’s website)
18. Liew PY, Klemeš JJ, Doukelis A, Zhang N, Seferlis P, “Identification of Process Integration Options for CO2 Capture in Greek Lignite-fired Power Plant”, Chemical Engineering Transactions, 39, 2014, 1447-1452. (access in publisher’s website)
19. Pan M., Agulonu A., Gharaie M., Perry S., Zhang N., Bulatov I., Smith R., “Optimal Design Technologies for Integration of Combined Cycle Gas Turbine Power Plant with CO2 Capture”, Chemical Engineering Transactions, 39, 2014, 1441-1446. (access in publisher’s website)
20. Hüser N., Kenig E.Y. “A New Absorption-desorption Pilot Plant for CO2 Capture”, Chemical Engineering Transactions, 39, 2014, 1417-1422. (access in publisher’s website)
21. Li B.H. Zhang N., Smith R., “Rate-based Modelling of CO2 Capture Process by Reactive Absorption with MEA”, Chemical Engineering Transactions, 39, 2014, 13-18. (access in publisher’s website)
22. Dufal S, Papaioannou V, Sadeqzadeh M, Pogiatzis T, Chremos A, Adjiman CS, Jackson G, Galindo A, “Prediction of Thermodynamic Properties and Phase Behavior of Fluids and Mixtures with the SAFT-γ Mie Group-Contribution Equation of State”, Journal of Chemical and Engineering Data, 59(10), 2014, 3272-3288. (access in public institutional repository from August 2015)
23. Pan M, Bulatov I, Smith R, “Efficient Retrofitting Approach for Improving Heat Recovery in Heat Exchanger Networks with Heat Transfer Intensification”, Industrial and Engineering Chemistry Research, 53(27), 2014, 11107-11120. (access in public institutional repository from June 2015)
24. Pan M, Bulatov I, Smith R, “Recent methods for retrofitting heat exchanger networks with heat transfer intensifications”, Chemical Engineering Transactions, 39, 2014, 1435-1440. (access in publisher’s website)
25. Yazgi M, A Olenberg, EY Kenig, “Complementary Modelling of CO2 Capture by Reactive Absorption”, Computer Aided Chemical Engineering, 33, 2014, 1243-1248. (access in public institutional repository)
26. Hüser N, Dubjella P, Hugen T, Rietfort T, Kenig EY, “Untersuchung und Bewertung einer strukturierten Packung mit 75°-Neigungswinkel für die CO2-Abscheidung”, Chemie-Ingenieur-Technik, 86, 2014, 1451-1452. (access in public institutional repository)
List of Websites:
https://arquivo.pt/wayback/20180718123649/http://www.capsol-project.eu/
Centre for Research and Technology – Hellas (CERTH), Greece
Chemical Process Engineering Research Institute (CPERI)
Laboratory of Process Systems Design and Implementation
Contact person: Dr. Panos Seferlis
Website: http://psdi.cperi.certh.gr/
University of Manchester, U. K.
School of Chemical Engineering and Analytical Science
Centre for Process Integration
Contact person: Dr. Nan Zhang
Website: http://www.ceas.manchester.ac.uk/research/centres/cpi/
University of Paderborn, Germany
Faculty of Mechanical Engineering,
Chair of Fluid Process Engineering
Contact person: Prof. Eugeny Y. Kenig
Website: http://www.uni-paderborn.de/fvt
Imperial College of Science,Technology and Medicine, U. K.
Centre for Process Systems Engineering
Contact person: Prof. Claire Adjiman
Website: http://www3.imperial.ac.uk/centreforprocesssystemsengineering
University of Pannonia, Hungary
Faculty of Information Technology
Research Institute of Chemical and Process Engineering
Centre for Process Integration and Intensification – CPI2
Contact person: Prof. Jiri Klemes
Website: http://cpi.uni-pannon.hu/
Eidgenössische Technische Hochschule Zürich, Switzerland
Safety & Environmental Technology Group (S&ETG)
Contact person: Dr. Stavros Papadokonstantakis
http://www.sust-chem.ethz.ch/
National Technical University of Athens , Greece
School of Mechanical Engineering
Laboratory of Steam Boilers and Thermal Plants
Contact person: Prof. Emmanuel Kakaras
Website: http://www.lsbtp.mech.ntua.gr/
Julius Montz GmbH, Germany
Contact person: Dr. Thomas Rietfort
Website: http://www.montz.de
Public Power Corporation S.A. Greece
Contact person: Mr. Charalambos Papapavlou
Website: http://www.dei.gr/
CaO Hellas Macedonian Lime S.A. Greece
Contact person: Mr. Georgios Dimitriadis
Website: http://www.caohellas.gr/
Process Design Center B.v. The Netherlands
Contact person: Mr. Evert van der Pol
Website: http://www.process-design-center.com/
Scottish Power Generation PLC, U. K.
Contact Person: Mr. Alan Dickson
Website: http://www.scottishpower.com/
