Skip to main content
European Commission logo print header

Innovative CO2 capture

Final Report Summary - ICAP (Innovative CO2 capture)

Executive Summary:
CCS (Carbon Capture and Storage) is a cornerstone in the struggle for climate change abatement. The current financial situation makes it crucial to focus on energy efficiency penalty, and capital cost reduction. Post-combustion CO2 capture from fossil fuel must deal with low flue gas CO2 partial pressure, 3.5-15 kPa. This limits membrane fluxes, solvent capacity, solvent selection and increases energy requirements. Pre-combustion CO2 capture is marred with a large number of processing steps, low hydrogen pressure, and high hydrogen fraction in the fuel. Global deployment of CO2 capture technologies is restrained by the need for prior removal of SO2.
The iCap project addresses a selection of research that is considered to be the most important and promising with regard to improved energy efficiency and overall capture cost reduction. Our postulate is that by addressing a selected range of the most important bottlenecks, we can by each both reduce capital cost and improve energy efficiency, and achieve an accumulated impact gain of a 40-45% reduction in the loss in power plant cost efficiency. iCap targets capital cost reductions of 30-40% and a reduction in thermal and electrical energy use by 45% through process intensification by the combined SO2 and CO2 capture, by increased capacity phase change solvents, by elevated pressure desorption, by employing high flux membranes, and by new cycles and better integration with the power production process.
The iCap project achievements are outlined below :
• Selection, characterization and validation through pilot testing of an environmentally benign, energy efficient multiphase post combustion solvent system. Pilot operation was successfully completed covering a wide range of operating conditions. Thermodynamic and kinetic models for both absorber and desorber conditions were implemented into in-house simulators and validation against pilot data were performed. Regeneration heat requirement below 2.4 MJ/kg CO2 captured was achieved experimentally and down to 2 MJ/kg CO2 by simulation.
• Development and characterization of two processes based on formation of CO2-hydrates. These processes were shown not to be advantageous for post-combustion CO2 capture.
• Development of fundamental models and tools capable of predicting thermodynamics of multiphase solvent systems (e.g the two-liquid-phase system and systems forming hydrates).
• Developed and test integrated multi component capture systems for combined SO2 and CO2 removal enabling significant process intensification and a total heat requirement of 2.3 MJ/kg and a total cost of 15 €/tonne CO2 avoided. Two systems, one amine and one ammonia based system, were developed and their feasibility was demonstrated and validated up to pilot plant scale.
• Developed a PPO/PVA-HAPS1 based polymeric membrane with CO2 permeance 1.56 m3(STP)/(m2 h bar) and CO2/N2 selectivity 294, twice the set initial goal. Long term stability was demonstrated through gas permeation tests during 246 days.
• Developed and test high flux, high stability membrane for steam methane reforming applications based on SCZ material for hydrogen transport membranes (HTM). The material has high stability at high temperatures and high CO2 and steam pressures, and shows high hydrogen flux, close to that of the best known HTM materials reported in the literature.
• Assessed novel power cycles and performed detailed techno-economic evaluations of the developed capture technologies integrated in existing and new processes. Evaluations showed a potential for achieving energy penalties of 6.8 % points from a coal fired power plant without any heat integration. This is significant improvement over existing technology and close to the target of 4-5% points.


Project Context and Objectives:
The main objective of the iCap project is to develop new CO2 capture technologies that individually and combined will enable highly efficient and cost effective production of electrical power from fossil fuels with near zero emissions. The target is to reduce the CO2 capture energy penalty to 4-5% points, about half of the penalty today, and to reduce the associated CO2 avoidance cost to 15€/tonne CO2. Thereby the barriers for CCS deployment worldwide can be removed and the technology deployment accelerated. This will be achieved by focusing on post combustion technologies that can be used both for retrofit and for green field plants. The technologies to be developed are highly innovative. Phase change solvents are used to concentrate up the CO2 captured, whereby the desorption heat requirement can be dramatically lowered while simultaneously opening for the use of low-grade heat. In addition, the high CO2 concentrations enables high pressure desorption and thus a reduction in recompression costs. Combined SO2 and CO2 removal gives a high degree of process intensification with significant capital cost reduction. Combined with low regeneration heat requirement it opens for CO2 capture technology deployment in areas where SO2 control is not installed. High flux post combustion membranes offer a solvent free and low efficiency penalty alternative and are particularly attractive in combination with the new power cycles developed. Continuous industry lead evaluation and costing of the processes will ensure the most effective progress of the project. Finally participation of CSLF countries, China and Australia ensures exposure to and attention in these increasingly important geographical areas.
iCap is split into five work packages. The three main technology development work packages on phase change solvents (WP1), membranes (WP4) and combined SO2/CO2 processes (WP3) form the main body. All new thermodynamic modelling needed for these capture methods is performed in WP2. The techno-economic evaluations in WP5 relate the separation techniques to the power processes for integration, optimization, costing, and for validation of efficiency and energy savings to be achieved. There are strong interdependencies between the WPs, e.g. the power processes may pose individual and specific boundaries for integration of the separation processes which in turn may put limitations on the separation process development in order to achieve the full potential in improved energy efficiency and cost savings for the total integrated process.

Project Results:
WP1 Phase Change Solvents

The iCap project investigated two novel capture concepts into the post combustion technology portfolio:
a) phase change solvents forming two liquid phases.
b) precipitating systems where CO2 is removed by hydrate formation enhanced by thermodynamic promoters
The main purpose of operating with slurry systems or systems forming two liquid phases is to achieve a concentrating up of the CO2 containing phase. When precipitation occurs the resulting slurry can be thickened or filtered and a high CO2 concentration can be obtained. The same is the case when two liquids form; one of the phases will be rich in CO2 and the other lean in CO2. By limiting the further processing to liberate CO2 in a desorption stage to only a slurry or an extremely rich liquid phase, the desorption becomes more energy efficient.

Phase change solvents forming two liquid phases
The iCap project has developed a novel absorbent system that forms two liquid phases at high concentration and CO2 loading, with one phase containing CO2 at a very high concentration, this resulting in low circulation rate, a more energy efficient CO2 desorption, and a potential for obtaining the CO2 at elevated pressure
The DEEA/MAPA system was shown to have the desired properties with regard to forming two liquid phases with high concentrations of CO2 in the lower phase, good chemical stability and good potential for energy requirement reduction. This system was selected for further characterization. For the individual components a large set of new equilibrium data was produced and on this basis rigorous e-NRTL/e-UNIQUAC models were fitted. Further, a large number of equilibrium, kinetic and physical property were been gathered for the mixed system. Based on the properties of the two liquid phases, thermodynamic models for the mixed system were developed and used in the SINTEF/NTNU in-house software CO2SIM to simulate both absorber and regenerator.
Modifications to the existing NTNU/SINTEF rig for pilot testing were performed, making it ready for a multiphase solvent system. The rig is based on a full recycle of gas flow from the absorber to a wash section, and then back to the absorber. Also the CO2 stripped off from the regenerator is recycled back just before the circulation fan. Thus the rig is fully closed, making it particularly suited for liquid/liquid systems that may have issues regarding solvent volatility.
The aqueous DEEA/MAPA solution was tested during a 4 month pilot plant campaign where 19 steady state points were achieved. As a base case a short additional MEA campaign was run. From IC analyses on the upper phase, it is possible to conclude that practically all the MAPA is in the lower phase. This is true for all loadings in the most interesting range. Therefore, if the loading is defined as the number of moles of CO2 per mole of MAPA in the lower phase, displaying the specific reboiler duty as function of this loading can be more easily compared with the MEA campaign. The loading for MEA is calculated as the number of moles of CO2 divided by the number of moles of MEA.
Pilot test results shown that we were able to operate down below 2.4 MJ/kg CO2 captured which was significantly better than for the MEA campaign. Also the DEEA/MAPA campaign was not run optimally as much light phase followed the heavy phase to the regenerator, thereby increasing the sensible heat demand. As a general observation, the DEEA-MAPA system was easy to operate and stripped very easily.
Experimental data from a pilot campaign for the system were validated towards the simulation model implemented in CO2SIM. A total of 19 runs from the campaign were validated and simulated with CO2SIM. It was concluded that a model of the DEEA/MAPA system was successfully implemented in CO2SIM and can be used for further simulations of large scale plants.

Precipitated systems where CO2 is removed by hydrate formation
The aim of the iCap project was to create the fundamental theoretical background for and validate this process by thoroughly investigating the thermodynamic and mass transfer phenomena at laboratory scale and also carry out a first evaluation of the CO2 capture process by hydrates at industrial scale.
The experimental work within iCap has shown than with the studied systems it is possible to operate the hydrates formation at pressure below 5 bars and even at near atmospheric pressure.
Good N2/CO2 selectivity has been observed but with a CO2 content near 15 vol.%, which corresponds to flue gases from coal power stations, a 2 step process appears necessary.
Nevertheless, if we operate at low pressure, hydrate storage capacity is low and by consequence bulk reactor volume and flow rates are very high. To limit CAPEX and OPEX it would be necessary to operate above 40 bars and in this case the energy penalty for flue gases conditioning would be too high.
The main conclusion from the iCap project is that the hydrates processes are not adapted for CO2 capture in post-combustion. We recommend considering other applications for hydrates processes such as CO2 capture in pre-combustion. For the future studies on hydrates processes, it would be also very important to consider storage capacity as the main parameter for screening the different systems.
Environmental impacts of new phase change systems
A prerequisite of the new absorbent systems developed for phase change operation, is that they should be environmentally benign. In addition to normal evaluations based on health and safety norms, the systems selected for characterization have undergone testing for ecotoxisity and biodegradation in accordance with the ISO/DIS Guideline 10253/OECD Guideline 306 standard test procedures to ensure that they will be classified as environmentally safe.
Within this project the biodegradation and ecotoxicity in freshwater and marine environments were determined for 5 solvents. These included the tertiary alkanolamine diethylaminoethanol (DEEA), the secondary polyamine 3-amino-1-ethylaminopropan (MAPA), a mixture of DEEA and MAPA, the quaternary ammonium compound tetra butyl ammonium bromide (TBAB) and the amino acid beta-alanine in an alkaline solution. In addition, the ecotoxicity of aqueous ammonia was evaluated, but not tested. The main outcomes of this study were:
• All chemicals were biodegradable in freshwater or marine "ready biodegradability" tests, except TBAB
• All chemicals showed acute toxicities with EC50 > 10 mg/L in marine and freshwater phytoplankton and invertebrate tests, indicating moderate ecotoxicity
• Calculations of additive toxicity and comparison to measured results for the mixture of DEEA and MAPA showed better agreement between the two approaches for marine than for freshwater tests
• The ecotoxicity of aqueous ammonia was also regarded as moderate, since this chemical probably will appear as an ammonium salt at neutral pH.
• Using a system for environmental classification and ranking of the iCap chemicals showed that classification and ranking of these chemicals were comparable to the well-known CCS alkanolamine monoethanolamine (MEA).
• Determination of predicted no-effect concentrations (PNECs) for the iCap chemicals, based on acute ecotoxicity results from the most sensitive tests, showed comparable or higher PNECs to MEA, although the PNEC for TBAB was lower than for MEA.


WP2 Modelling of complex systems
WP2 developed thermodynamic models suitable for predicting, with limited information, the phase behaviour of two-liquid phase systems and precipitating systems containing CO2 and various polar solvents. This kind of modelling is essential for design and process modelling of capture based on this technology.
The first of four tasks in WP2 models CO2 capture using gas hydrates. Gas hydrates are solid ice-like structures formed from water and small molecules at moderate to high pressures. The advantage is that they form preferentially with CO2 rather than with nitrogen, and (since they are solids) they are easy to separate from the flue gas and remaining liquid. This tasks worked closely with WP1 where the goal was to bring down the hydrate formation pressure using so-called hydrate promoters.
The second task (W 2.2) models CO2 capture using a system which forms two liquid phases. Again, the advantage is that CO2 enters one of the phases preferentially, enabling easier separation. This task also worked closely with WP1 where appropriate solvents for forming the best liquid-liquid separation were being identified. Rigorous models were developed, using the NRTL and e-NRTL frameworks, to describe the vapor-liquid equilibrium of the binary systems: DEEA-H2O, MAPA-H2O, MAPA-DEEA; the ternary systems: MAPA-DEEA-H2O, DEEA-CO2-H2O, as well as the initial development of the model for the MAPA-CO2-H2O system. It is seen that the NRTL model framework is well suited for the modelling of all the binary systems as well as the ternary amine system without CO2. The e-NRTL framework further describes the DEEA-CO2-H2O system very well but is not yet finished for the MAPA-CO2-H2O system. The soft models developed describe the combined DEEA-MAPA-CO2-H2O well and was successfully implemented into CO2SIM. In addition, a PSO (particle swarm optimization) based algorithm used to fit the NRTL and e-NRTL parameters to the experimental data was developed.
The third task seeks to extend the models developed to elevated pressures, which may be attractive under various capture scenarios. The final task models the effect of SO2 on the capture process. This is an impurity often present in flue gas, and can affect the process in unexpected ways.
The main results of this are:
i) The development of a thermodynamic model for hydrate forming systems The model also successfully models the effects of promoters which lower the formation of the gas hydrates;
ii) The development of models of the liquid-liquid systems. The models can describe the phase separation and individual phase equilibria in the two-liquid systems formed by aqueous DEEA, MAPA and carbon dioxide;
iii) The production of new experimental data for both liquid-liquid and hydrate systems. This has been carried out to an extent which enables development of models of these processes;
iv) The development of a process concept and model for combined CO2-SO2 removal.


WP3 Combined SO2 and CO2 removal

The overall objective of WP3 is to develop, test and demonstrate a combined SO2 and CO2 capture process with step-wise regeneration leading to one sulphur containing stream and one CO2 stream. Central in this work package is the development of amine and ammonia based systems for the combined removal and to demonstrate and validate this up to pilot plant scale.
For the amine based solvent, testing was performed on the pilot plant of CSIRO at AGL Loy Yang power plant in Victoria, Australia. The testing was a joint effort of CSIRO and TNO in strong collaboration with the Monash University, Gippsland Campus.
For the Ammonia based process, Tsinghua University completed and tested their system on a small pilot plant. This pilot plant became operational at the beginning 2013. The small pilot plant was a modification of an existing amine based absorption-desorption facility.
Testing of the CASPER process.
CASPER (CO2-capture And Sulphur Precipitation for Enhanced Removal) is a novel process, developed within the iCap project, for simultaneous CO2 and SO2 removal from flue gas. The process concept is based on reactive absorption of the acid gases in a solvent, using a potassium-aminoacid based aqueous solution, and the precipitation of the sulphur as K2SO4.
The CASPER process was successfully tested in a pilot plant installation of CSIRO during February and March 2013. The campaign took place at Loy Yang Power Plant in Victoria, Australia (combined absorption and CO2 desorption part) and at Monash University, Gippsland Campus (solvent regeneration step).
The baseline performance of 3M potassium β-alanate was satisfactory in comparison to the experimental values obtained for MEA carbon capture processes in the same pilot plant installation. Also, as expected, the SO2 was absorbed very efficiently into the solvent. The absorbed SO2 is gradually converted via sulphite towards sulphate. The influence of different conditions on the sulphur dioxide/sulphite- sulphate conversion rate were investigated. It was confirmed that SO2 and higher concentration of oxygen (21%) together with presence of NOx can have a positive influence on this chemical process.
The solvent was regenerated by removing the sulphate via precipitation as potassium sulphate and subsequently reused in the second round of the pilot plant campaign. The actual solubility limits of potassium sulphate were determined and compared with laboratory experiments. Observations of the pilot plant campaign indicate a reasonable stability of the solvent.
The overall conclusion is that a proof of concept for the CASPER has been obtained. However, more solvent optimization is needed to reduce energy consumption of the overall process as compared to the state of the art solvent system MEA.Calculations made indicate that the CASPER process will give a performance improvement of about 5.5% compared to MEA.

The ammonia based process.
The main research results on the combined capture of SO2 and CO2 using ammonia solvent are summarized in this section.
Firstly, the kinetics and mass transfer of the combined process were studied in a wetted wall column experimental system at different SO2 and CO2 loadings, ammonia concentrations, absorption temperaturesand gas flow rates. It was observed that the CO2 and SO2 loadings have significant effect on both the absorption of CO2 and SO2. This has to be controlled in the absorber to obtain a high CO2 and SO2 recovery. The SO2 mass transfer does not decrease significantly when the CO2 concentration in the inlet flue gas increases. However, the SO2 concentration affects the CO2 mass transfer significantly. A high ammonia concentration is beneficial for the combined absorption of CO2 and SO2, and is more positive to the increase of the CO2 mass transfer coefficient. Both mass transfer of CO2 and SO2 increase when the absorption temperature increases. The selectivity absorption factor increases with increasing temperature. The CO2 mass transfer coefficient increases marginally with increasing gas flow rate.
Secondly, the performance of the combined CO2 and SO2 capture process using aqueous ammonia was studied in a lab-scale pilot plant at Department of Thermal Engineering, Tsinghua University, China. The pilot plant tests involved individual CO2 and SO2 capture tests using aqueous ammonia as the baseline and the combined CO2 and SO2 absorption and regeneration process tests. It was observed that the pilot plant tests were repeatable and the gas inlet SO2 had no obvious effect on the CO2 absorption efficiency. However, when the SO2 content accumulates in the aqueous ammonia solvent, the CO2 absorption efficiency tends to decrease. The pilot plant performance also shows that the ammonia loss is serious in both absorber and stripper gas outlet. This ammonia can react with CO2 and water in the flue gas and precipitate solids in the condenser and pipes if the temperature is low. This caused solid build-up that could block the stripper condenser and gas looping pipes, leading to a shutdown of the pilot plant. Blockages also occurred in the CO2 analyzer and gas flow rate meter tubing, leading to inaccurate readings and affecting long-term steady operation of the pilot plant.
Thirdly, a rate-based model for a combined CO2 and SO2 absorption and regeneration process using aqueous ammonia was developed and used to simulate results from the recent pilot plant tests, evaluate the pilot plant performance, and to predict the unreachable pilot plant results caused by the solid precipitation. The model was built based on the recent pilot plant setup and test parameters using the Aspen Plus, mainly including a rate-based absorber unit and an equilibrium based stripper unit, in which the thermodynamics, chemistry and kinetics of the NH3-CO2-SO2-H2O system were specified. The predicted results show that the CO2 absorption efficiency decrease with an increase in SO2 loading. Both the NH3 slip at absorber and stripper gas outlets were very high, CO2 regeneration energy decreases with SO2 loading accumulation in the looping solvent.


WP4 Highly efficient and long term stable membranes for CO2 capture
Activities in WP4 of iCap were focused on development of membrane technologies for CO2 capture, and they were divided into two types of membranes; Hybrid membranes for CO2 capture for post combustion and hydrogen transport membranes (HTM) for separation of H2 in Pre-combustion capture technologies.
The main objective was to develop high flux and stable membranes, suitable for the two operating conditions. Hybrid or Mixed Matrix (polymer based + nanoparticles) membranes for selective CO2 separation are operated at low temperature (flue gas temperature) and separate CO2 from flue gas mainly containing N2, O2, CO2 and H2O.
Hybrid or Mixed matrix membranes for CO2 Capture
Various polymers and nano-particles were examined in this project. One of these combinations was shown to have outstanding performance as a low temperature CO2 selective membrane. This membrane has a great potential for commercial development. Currently we have not published these results but are developing a patent based on the results.
Hydrogen Transport membranes (HTM
The main objective was to develop high flux and stable membranes, suitable for the pertinent operating conditions. Hydrogen transport membranes are considered for a catalytic membrane reformer (CMR) operating at high temperature and pressure. These membranes were prepared from ceramic H2 dense selective materials
The project has undertaken the ambitious tasks of developing high flux high stability membranes for steam methane reforming application. This objective entailed the achievement of various milestones, as follows:
• Formulations of materials with improved stability verified at high temperature and pressure
• Synthesis, pressing and sintering of symmetric membranes with density above 95 %
• Development of sealing procedures for mounting planar and tubular membranes in a testing module
• Manufacturing of thin film membranes coated on porous tubular supports with adjustable porosity
• Understanding of transport properties of the membrane materials

WP5 Technology evaluation, cost and efficiency estimations
WP5 was the system integrator, by using information from the other WPs of the project on separation technologies development and performance, to evaluate power plant performance. The models for the modified capture systems were extended to the entire power plant thereby enabling assessment of performance for pulverised coal-fired supercritical hard coal and combined cycle gas turbines. The relative operating costs of the new systems were compared with standard amine systems and the overall economics assessed for a number of specific test cases.
Using models developed within iCap the “Cost of Electricity” (CoE) and “CO2-avoidance costs” (AC) were evaluated for the reference capture process based on 30 wt.-% MEA as well as for the novel capture processes. Furthermore, the CoE without CO2-capture was calculated to form a quantitative basis for comparison.
The CASPER process and the liquid-liquid process show potential for reducing the CO2 avoidance costs. Neither the hydrates, the low temperature membrane process nor the combined SO2/CO2 capture using aqueous ammonia process were deemed economically feasible compared with capture processes based on wet chemical absorption. Technical difficulties, such as enormous auxiliary demands or the necessity for very large heat exchange surfaces prohibit the use of the latter concepts in practice for post-combustion CO2 capture from power plant flue gases.
As the absolute numerical results obviously depend on the degree of heat integration achieved and the boundary conditions chosen for the assumed economics, while, at the same time, the novel processes discussed here are themselves still in a stage of active research, the main target of this work was not to supply absolute numbers for the final cost of electricity generation but rather a realistic and reliable relative comparison among all capture processes tested. Towards this aim in all simulations the components and equipment modelled reflected current industrial reality and practice. For this, information and feedback from equipment manufacturers were obtained and incorporated in the analyses for both the power plant and the downstream capture islands. In this manner, as realistic results as possible could at the end be obtained.
The potential of the novel power cycles to mitigate the environmental impact from power generation was evaluated on the comparison basis of generating 1 MWh of electricity in a typical 750 MW coal fired power plant. The complete chain of processes involved was included in the evaluation, consisting of coal mining, coal transport, power plant with flue gas cleaning, solvent, capture process and solvent waste treatment.
Although CO2 capture involves additional environmental impact on all environmental issues considered in this study, with the exception of climate change, the impact is comparable with power generation without CO2 capture. Key for the environmental impact is the associated increase in the coal consumption, which requires mining and transport. Though the energy consumption is lowest for liquid-liquid capture, the inherent uncertainties in the boundary conditions and data used still prevent a conclusion on whether the liquid-liquid process is definitively better than the other technologies, in terms of environmental impact. The influence of the source of the coal fuel is significant. The differences among the mines plus the influences of transport distance are comparable to the difference between capture and no capture. This means that there is a large potential for improvement in the upstream processes. Note that the data for mining have an inherent uncertainty too.Whereas the production and emission of solvent, as well as the treatment of solvent waste, do not have a significant contribution to the overall environmental impact of power generation with carbon capture, the influence of the source and transportation distances of the coal are significant. This means that there is a large potential for improvement in the upstream processes.
As regards the emissions of nitrogen oxides, sulphur dioxide and ammonia, until good measurement data become available, no conclusions can be drawn about the environmental preference among MEA, liquid-liquid and CASPER based systems.

Potential Impact:
Commercial deployment of new technologies requires a number of market driven mechanisms, financial incentives (market push) and regulations (market pull), as well as technology breakthroughs (technology push). CCS is a well-established subject on the European political agenda and this ensures that market pull or/and push mechanisms are in place. However, deployment of CCS projects faces a number of technical, economic and environmental challenges with respect to costs, efficiency, and long-term underground storage. Therefore, industry supported R&D activities for technology breakthroughs that will address these challenges are of critical importance.
The technologies brought forward in iCap are partly of near term deployment nature. This is true for both the phase change solvent and the combined CO2 and SO2 capture process. The phase change solvent can operate in plants that distinguish themselves only marginally conceptually from today’s plants. Apart from the smaller size, much of the equipment will be the same, or of a type already existing. Thus, time from pilot plant testing at industrial scale to full scale deployment may not be very long.
For the combined SO2 and CO2 capture, this is a process that has the potential to shorten the deployment time significantly. Very few power plants in China, and even fewer in Australia, have SO2 removal installed. For an ordinary amine plant, this will be a prerequisite and will lead to an even larger hurdle for the deployment of CO2 capture technologies in these areas. The combined process removes this hurdle and paves the way for CO2 capture, that otherwise might be regarded as too costly.


List of Websites:
www.icapco2.org