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CO2QUEST Report Summary

Project ID: 309102
Funded under: FP7-ENERGY
Country: United Kingdom

Final Report Summary - CO2QUEST (Techno-economic Assessment of CO2 Quality Effect on its Storage and Transport)

Executive Summary:
This report summarises the main scientific and technological achievements of the CO2QUEST project aimed at addressing the fundamentally important issues regarding the impact of the typical impurities in a gaseous or dense phase CO2 stream captured from fossil fuel power plants on its safe and economic transportation and storage.

To address this challenge, state-of-the art mathematical models supported by laboratory and industrial-scale experiments utilising unique EC funded test facilities were developed to perform a comprehensive techno-economic, risk-based assessment of the impact of CO2 stream impurities on its phase behaviour, chemical reactions and pipeline and storage site integrities.

The above involved the determination of the important CO2 mixtures that have the most profound impact on pipeline pressure drop, compressor power requirements, pipeline propensity to ductile and brittle facture propagation, corrosion of the pipeline and wellbore materials, geochemical interactions within the wellbore and storage site and the ensuing health and environmental hazards.

The above along with a cost/benefit analysis and whole system methodology developed provided the essential tools needed for defining CO2 stream impurities tolerance levels, mixing protocols and control measures for pipeline networks and storage infrastructure to facilitate the safe design and economic operation of CCS systems on a case by case basis.

Although the main deliverables associated with the project are the overall methodology coupled with underpinning science which allows developers to explore the impacts of different impurities, some key insights from the techno-economic analysis that are more generic were gained in the course of the research.

These include:
▪ Some impurities cause more concern for pipeline transport (e.g. H2O, Cl, toxic compounds) than storage (e.g. N2 which causes storage site depletion)
▪ Other impurities (especially O2) cause concerns for both (corrosion in pipelines and biofouling in storage)
▪ Post-combustion capture (e.g. with amines) does not have a strong cost sensitivity with purity because the process by its nature produces relatively pure CO2 which primarily requires dehydration. The same is true for pre-combustion capture using physical solvents. However, oxy-combustion can produce CO2 streams with very different purities (from 83 to 99.8%) and costs depending on the post-treatment and air separation systems. Hence this technology received particular focus, and it was noticed for example that an O2 purity of greater than 95% starts to incur considerable costs due to entropic effects.
▪ Two CO2 sources not meeting pipeline specifications can be advantageously blended such that the blended stream meets the required specification. Similarly, cost reductions can arise (e.g. around 14%) by combining higher and lower purity streams rather than ensuring the lower purity streams meeting specifications directly.

Project Context and Objectives:
CO2 Capture and Storage (CCS) refers to a collection of technologies which allow for the continued use of fossil fuels for energy generation and in heavy industries by capturing waste CO2 in the given process and transporting it to a suitable location for subsurface geological storage, thus abating atmospheric emissions of CO2. For large-scale applications of CCS, transportation of CO2 using pressurised pipelines is found to be the most practical and economic method. However, a CO2 stream captured from fossil fuel power plants or other CO2 intensive industries will contain a range of impurities each having its own impact on the different parts of the CCS chain.

Determining the ‘optimum composition’ for a captured CO2 stream which addresses the technological, cost, safety and environmental concerns of CCS is therefore fundamentally important in facilitating CCS as a viable technology for addressing the impact of global warming. In the CO2QUEST project experimental and theoretical modelling work was carried out aiming to address this challenge and to generate insights into the important trade-offs that should be considered when considering this question.

The project main objectives included:

1. Establish the typical range and concentration of CO2 stream impurities derived from the three main capture technologies (pre-combustion, post-combustion and oxyfuel) by reference to published literature and recent analysis of flue-gas samples.

2. Use experimentation and theoretical modelling to develop accurate, robust and efficient physical property models based on the SAFT Equation of State (EoS) for gas and dense phase CO2 mixtures containing typical impurities at operating temperatures and pressures encompassing the entire CCS chain.

3. Using the EoS developed in (2), model non-isothermal steady state flows in realistic pipeline network systems transporting CO2 containing typical impurities. Identify which impurities have the most adverse impact on pipeline pressure drop, capacity, fluid phase and compressor power requirements.

4. Using the EoS developed in (2), model the impact of impurities on the near-field structure of accidental releases and the impact this has on CO2 dispersion characteristics. Validate results against data gathered in CO2QUEST. Additionally, provide detailed pipe-wall and crack-flow interaction predictions for input into (5).

5. Develop and validate fluid/structure fracture models for ductile and brittle fracture propagation in CO2 pipelines. Apply these models to identifying which impurities and operating conditions have the greatest impact on a pipeline’s resistance to long running fractures. Consider a variety of candidate pipeline steels.

6. Using previously published experimental data and knowledge transfer through on-going national research programmes, identify CO2 mixtures that have the most pronounced impact on the corrosion behaviour of pipe and wellbore candidate steels and develop appropriate corrosion prevention measures.

7. Quantify the effect of impurities on the performance of CO2 geological storage, both in terms of fluid/rock interactions and leakage of trace elements, through a combination of modelling studies, laboratory experiments and large-scale field injection experiments using CO2 and CO2 mixtures.

8. Design a decision making risk assessment tool for determining additional safety and environmental hazards associated with the transportation and storage of pure and impure CO2.Use model predictions to recommend appropriate prevention and mitigation measures for the hazards identified.

9. Develop a model-based approach for assessing the impact of CO2 stream impurities on CCS system performance, use this approach to explore feasible operational envelopes, cost trade-offs and cost versus other impact (e.g. safety and environmental) category trade-offs

10. Undertake a cost-benefit analysis of the whole CCS system, based on the above findings, exploring appropriate levels of purity from a whole system perspective and recommend mixing protocols.

The main technical developments were carried out in five Work Packages:

WP1 – Fluid Properties and Phase Behaviour
WP2 – CO2 Transport
WP3 – CO2 Storage Reservoir Performance
WP4 – Techno-Economic Assessment
WP5 – Impacts and Risk Assessment

In WP1 typical CCS stream compositions were characterised based on data provided by the project’s industrial partners. These formulations were validated against experimental data generated as part of CO2QUEST. An EoS for CO2 containing the various impurities was also developed in WP1, providing the thermodynamic and physical property models needed for the various process models developed in WP2, WP3 and WP4.

In WP2, to account for the variation of CO2 stream purity across a multisource CO2 pipeline network a thermo-hydraulic model was developed and applied to evaluate the impact of impurities on the pressure distribution across the network and the associated compressor power requirements.

Also in WP2, a transient multi-phase flow pipeline decompression model was coupled with material damage models in order to provide a tool for assessing ductile and brittle fracture propagation. The validation of the fracture models was based on experimental fracture testing of relevant steels using existing field-scale industrial pipeline test facilities. The pipeline decompression model also provided the source condition for the near-field dispersion modelling, also conducted as part of WP2, which was supported by experimental studies of small and medium scale releases of impure CO2 performed in the project.

Another important element of WP2 was also aimed at establishing the impact of impurities upon materials corrosion for pipelines and wellbores.

The work undertaken in WP3 involved modelling of geo-mechanical and geo-chemical phenomena associated with the underground injection and storage of pure and impure CO2. This modelling work was also supported by a comprehensive set of laboratory scale experiments. WP3 was further supported by field-scale push-pull reservoir experimental work and also by a study of the behaviour of CO2 with typical impurities in a shallow aquifer injection experiment.

WP4 addressed the techno-economic assessment, leading to an integrated whole-system approach. This started by building a component based set of models for the key system elements, taking advantage of developments in other WPs as well as information in the academic and commercial literature. These models, when parameterized in line with industrial processes (e.g. a case study based on typical power plant CO2) sources in the UK can be used to explore cost-purity trade-offs and the opportunities arising from mixing streams with different compositions arising out of different capture technologies. The impacts upon health, safety and environmental risk management, mixing protocols and tolerances were addressed in WP5 by means of a collaborative approach of all the partners.

Project Results:
Please find the description of the main S & T results/foregrounds in the PDF file attached
Potential Impact:
The internationally agreed, legally-binding global climate deal reached at the Paris Climate Conference (COP21) in December 2015 is intended to limit the increase in global average temperatures to less than 1.5°C above pre-industrial levels by the end of the century. Achieving this goal requires a 50 – 80% reduction in CO2 emissions. Carbon Capture and Storage (CCS) is widely recognised as the single most effective technology to reduce CO2 emissions on a global scale to meet the above target. Indeed, CCS has the potential for near-zero emission power stations when burning fossil fuels. This would allow further exploitation of fossil fuel reserves, including coal, in Europe and the rest of the world without adding to greenhouse gas emissions. As such, CCS will be an important strategy for maintaining energy supplies and allowing increases in energy production in the developing world, whilst mitigating climate change.

In terms of the market size for CCS worldwide, there are currently in excess of 5,000 large-scale CO2 sources in the power industry alone, responsible for emitting approximately 10.5 billion tons of CO2 per annum. IEA studies have shown that if the world continues on its current path, global CO2 emissions from energy production and use are likely to increase to over 42 billion tons a year by 2030. In China, 70% of energy is produced from burning coal, which is much higher than the average level of coal usage within the international energy structure (at approximately 30-40%). Coal in China is mainly used in power plants and ore-refining furnaces and as a result, CO2 emissions have increased significantly. China is now the world’s largest emitter of CO2 and is under significant pressure to reduce its CO2 emissions. To this end, China has recently started a tendering process for CO2 capture and storage technology. It is therefore imperative for Europe and the rest of the world that any barriers to the uptake of CCS technology worldwide are resolved. This will be necessary not only to facilitate the export of CCS technology from Europe to the rest of the world, but also to safeguard energy production and other CO2 emitting industries within Europe so that employment prospects and quality of life are maintained and improved.

Economic considerations dictate that the captured CO2 from fossil fuel and industrial emitters transported by high pressure pipelines for subsequent geological storage cannot be completely purified. This poses a significant dilemma given that the types of stream impurities which may be tolerated in the pipeline can be detrimental to the storage site integrity. Also, the stream impurities significantly impact the physical, chemical and the risk profile of CO2.

In the CO2QUEST project, fundamental experimental and theoretical work has been undertaken to perform a techno-economic analysis to determine the optimum range and concentration of CO2 impurities in the CCS chain with safety and environmental implications being the over-arching factor. A unique feature of the project is its global rather than just European reach through partnerships with China, the world’s largest CO2 emitter, and Canada, representing one of the world’s most advanced nations it the context of its work on CCS.

The safety of CO2 pipelines is one of the serious potential barriers to the uptake of CCS. Indeed, pipelines are the most viable and economic means for transporting large quantities (and flow rates) of CO2 at high pressure from the capture plant to the point of injection. In many cases such pipelines will need to be routed close to, or through densely populated areas. Safe transportation of CO2 with impurities by pipeline, and its subsequent geological storage, requires an understanding of the consequences of catastrophic events.

All new technologies require public acceptance in order to be successfully introduced. It is highly important to address safety from the outset so as to prevent any disasters involving CO2 transport and storage networks. Major events of this kind would attract considerable media attention and the technology would become perceived as dangerous which could seriously affect the uptake of CCS on a global scale.

Developers of CCS projects need as much certainty as possible about the design requirements so that costs can be estimated accurately. This is important in gaining financial investment and approval for new projects. It is also extremely important to be able to calculate hazard ranges from CO2 pipelines to ensure that these are routed in a safe manner, which is acceptable to the planning authorities and other regulators.

Safety and environmental regulators and planning authorities need an understanding of catastrophic releases from pipelines in addition to the long term behaviour of CO2 during geological storage so that there are no unnecessary delays in the approvals process for new CCS projects.

The research performed in CO2QUEST project has made its impact at four levels:

(a) at a fundamental research level through the investigation of unknown issues that must be understood in order to allow the development of methods capable of reliably assessing the techno-economic impacts of common impurities in CO¬2 streams;

(b) at a level of decision support tools which embody the results of fundamental research, in the consequence and risk assessment models, a whole-system analysis methodology, best practice guidelines, materials selection protocols, tolerance levels, and mixing protocols for blending impure CO2 sources and the matching of sources, transport and sinks;

(c) at a demonstration level, where the decision support tools were applied to identify potential hazards and then predict and model the consequences. At this level the pathways for use of the methods and developed tools applicable to industry involved in the implementation of CCS are shown to provide practical recommendations for improving operational safety and safeguarding members of the public and operators from the consequences of CO2 leaks from transportation networks and geological formations. Also, the demonstration of a methodology to match operational envelopes of sources, transport infrastructure, and sinks to generate CO2 network superstructures was undertaken and it was shown that cost reductions of over 14% are possible using a system wide approach to impurity management compared to management at source. Using the project-generated guidelines for composition, transport and storage of impure CO2, the cost-benefit analysis model developed provides a useful tool for blending of flue-gas streams from different sources and optimising the operation of the CO2 transport and storage systems while considering both cost and other metrics (e.g. safety and environment); and

(d) at an applied research level, through the development of world-class experimental test facilities and unique computational tools being made available to enable the safe design and economic operation of new CCS systems.

In terms of fundamental research, the project generated new knowledge in a number of areas to allow the accurate assessment of the impact of impurities in CO2 streams.

With respect to transportation, in order to quantify the hazards posed by a release of impure CO2, experimental investigations have been performed and numerical models were developed. CFD models capable of predicting the multi-phase heterogeneous flow of CO2 with impurities within and upon leakage from pipelines have been developed by UCL and the University of Leeds to allow the accurate prediction of discharge rates and the fluid state during pipeline failure and depressurisation, and the investigation of methods for mitigation against such losses (WP2). Also, the data generated by INERIS and CANMET in WP1.3 has enabled the validation of thermo-physical models capable of predicting relevant phase equilibria, thermodynamic and transport properties of CO2 originating from various capture schemes (WP1.1) over the wide range of fluid conditions likely to be encountered in practice (WP1.2). These modelling tools enable characterising the requirements for CO2 purification to protect pipelines during transportation (WP2.3.1) and the environment following accidental release (WP5), and the costs associated with such purification (WP4).

Mathematical models capable of predicting the near-field structure of high pressure releases of supercritical and multi-phase impure CO2, including models for the formation of liquid droplets and solid particles, were developed in order to provide input into far-field dispersion models, and to allow assessments of the near-field impact of CO2 releases (WP2.2). Such dispersion models, enabled characterisation of the impact of CO2 impurities on the dispersion flow.

Running or propagating fractures are by far the most catastrophic type of pipeline failure. As such it is highly desirable to design pipelines with sufficiently high fracture toughness such that when a defect reaches a critical size and the pipeline fails, the result is a leak rather than a long running fracture. A pipeline can fail either in ductile or brittle fracture modes. In WP2.3 the risk of such types of failures were thoroughly investigated by OCAS and INERIS by conducting material characterisation and high pressure pipe breach release tests for candidate CO2 pipeline materials. The results were in turn employed in the dynamic pipeline crack propagation model developed by UCL and OCAS to enable pipeline designers to employ pipe steels with the appropriate mechanical properties to resist running fractures.

With respect to geological storage, impurities in CO2 may affect the well materials of construction, the trapping behaviour of the CO2, and also the target reservoir and cap-rock properties. These issues were addressed within CO2QUEST by the use of state-of-the-art modelling techniques (WP3.2) which incorporate methods for predicting the phase equilibria, thermodynamic, and transport properties of CO2 with various impurities (WP1.2).

Investigations regarding the impact of impurities on geological storage have to date been carried out with the help of computational models, and no field experiment aimed at validating the results of such calculations has been conducted. In CO2QUEST, INERIS performed a series of push-pull tests using CO2 with impurities, in order to simulate a vertical leakage from a shallow aquifer, emulating a scenario of CO2 leakage from deeper storage in a saline formation.

The understanding and predictive methods developed through the research components of the project, described above, were embodied within impact and risk assessment tools (WP5). Such tools have been developed in the project to meet the needs of the design and safety engineers undertaking the complex and integrated tasks required in the design of a CCS system. Under this work package, the additional risks posed to safety and to the environment for typical CO2 impurities were evaluated. Also, possible subsequent impacts and mitigation measures were investigated. The additional threats raised by each impurity, such as increased magnitude of a pressure wave upon pipe rupture, or increased pollution of water resources, were evaluated, alongside associated probabilities for events such as leakage and subterranean chemical alteration.

A major advancement in WP5 is a new tool for evaluating both the safety and impact aspects of short-term operations of CCS chains and the longer-term phase of CO2 storage. Such a tool will be invaluable in furthering CCS technology and its advancement to societal norm since it will provide public reassurance of the safety of CCS.

As a result of studies in WP5, the most significant CO2 impurities in terms of their physical, chemical and toxic/ecotoxic effects were identified. This body of information is invaluable to authorities in the preparation of regulations regarding impurities concerning new and developing technologies. Subsequently, additional risk-reducing measures may in turn be identified in the form of detection and sampling strategies, safety device specifications, and operational protocols for CO2 transport, storage and injection.

Lastly, and in order to promote uptake of the knowledge and technologies developed within the project, demonstration of their usefulness was carried out by their application to the techno-economic assessment performed in WP4. This involved a cost/benefit analysis (WP4.1) using an integrated whole-system approach (WP4.2) to optimise the CO2 capture, transport and storage requirements. The usefulness of the techno-economic model developed was demonstrated through its application to an existing design of a realistic UK CCS transportation system. The decision support tools were developed taking into consideration the effects of impurities on CO2 transport and storage, and to find ways of blending CO2 sources and matching sources, transport and sinks, where it was demonstrated that a network-wide approach to impurity management is much more cost effective than managing impurities at source only. Additionally, the costs–benefit analysis was performed to generate feasible operational envelopes for CCS systems involving CO2 streams of various purities. A multi-scale whole-system approach incorporating the expertise of each partner was used to iteratively obtain the configuration of the CCS system where the fluid composition optimized the whole chain performance. By these means, the usefulness of all the work performed to enable the safe and economic deployment of CCS technologies to power generation and other CO2 intensive industries has been demonstrated. A framework was also developed to compare cost-based measures with those based on other considerations (“indices”) such as corrosivity or toxicity which cannot directly be converted to cost equivalents.

List of Websites:
The project maintained a website for the efficient sharing of information between contributors and for the dissemination of materials publicly. New content was added to the website on an ongoing basis throughout the project. The website may be found at:

Contact details of the project co-ordinator:
Professor Haroun Mahgerefteh
Chemical Engineering Department
University College London
Tel: +44-2076793835
Fax: +44-2076793835

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