Why is this research needed?
Post-combustion CO2 capture (PCC) plants using amines are the basis for a number of full-scale projects in the current wave of UK CCS deployment, and their capital costs and residual CO2 emissions are therefore key factors in determining the overall cost and feasibility for the UK net-zero target. The Committee on Climate Change, in their recommendations for the 6th Carbon Budget, identified attaining at least 95% capture as a critical requirement if CCS is to be widely deployed, with up to 99% obviously preferred, but currently expects 90% until after 2040.
Draft BAT guidelines from the Environment Agency for power PCC and for hydrogen production, developed with UKCCSRC support for a PCC BAT Review, recommend, however, that new PCC plants are designed for 95% capture immediately. This has been supported by the industry, but it has also been noted that there is limited existing experience for operation at such high capture levels. Test results from this project will provide additional support for this innovation by demonstrating the changes in PCC plant design and operation required to deliver cost-effective 95%+ capture. Successfully achieving 95%+ capture now would obviously make a big contribution to the new UK 6th Carbon Budget target of 78% reduction in emissions by 2035 and open up the feasibility of using CCS more widely because of lower penalties from residual emissions. The new test techniques using solvent storage that are being developed to facilitate the advanced operating condition in this project can also help pilot plants generally to be more effective.
The project will also address two important supporting issues for PCC deployment. Using the PCC-CARER runs and other tests at TERC a system will be installed and tested to monitor oxygen levels in the captured CO2 and assess possible controls. A key question is the extent to which dissolved oxygen is consumed by irreversible oxidative degradation of the MEA rather than being released in the stripper. Lab-scale systems for thermal reclaiming will also be developed, mainly using effort from project students. These will reclaim used solvent from this project, and others with longer testing times. Results over the limited period of this project are expected to be indicative assessments of reclaiming residue properties, but this equipment can underpin the continued development of a comprehensive, long-term programme of fundamental and applied research to inform and guide thermal reclaiming practice.
Solvent hygiene is essential for successful PCC operation, with consequences for failure including the formation of highly toxic nitrosamines, excessive degradation, foaming, corrosion, increased viscosity and general reduction in performance. Thermal reclaiming can remove virtually all unwanted substances from a solvent and, if operated continuously in conjunction with solvent stripping, has a minimal energy penalty. Thermal reclaiming is, however, both figuratively and literally something of a ‘black art’ due to the extreme complexity of the mix of materials being processed. Reproducing it at lab scale is the essential first stage in bringing fundamental science to bear on the problem.
What is this research investigating?
This research is looking at a number of measurements to feed into enhanced performance for post-combustion capture. Its objectives are:
- To obtain novel pilot-scale measurements on the TERC Amine Capture Plant for post-combustion amine plant operation with low lean loadings and liquid flows, conditions that are now required to obtain cost-effective operation at 95%+ CO2 capture levels will be automatically published on EPSRC’s website in the event that a grant is awarded.
- To combine pilot-scale measurements with modelling activities on a linked UKCCSRC project and, with input from the project industrial partners, use the results to assess and improve realistic design and operation approaches for full-scale amine post-combustion capture plants to achieve 95%+ CO2 capture levels.
- To develop and deploy at a system on the TERC Amine Capture Plant to measure the oxygen content of the product CO2, and use this to assess the effect of operating conditions on oxygen carryover.
- To design and develop lab-scale thermal reclaiming rigs that can be used to underpin future fundamental research on thermal reclaiming and, within the limited timeframe of this project, undertake the production of reclaiming residues from suitable MEA samples.
- To work with project sponsors, Bechtel and SSE Thermal, to shape the above research to match actual industrial needs and to ensure that the results are in a form that can make an immediate impact on full-scale CCS deployment.
- To undertake wider dissemination and knowledge transfer activities, linked to the UKCCSRC, with UK industry, regulators, policymakers, academics, media and other public outreach routes to deliver effective impact through appropriately-framed and interactive communications with all of these stakeholders.
- To work with the International Test Center Network and other international organisations such as the UNECE to maximise the global impact of evidence for CCS operation at 95%+ capture levels, in particular to support CCS initiatives and communication around COP26.
What does the research hope to achieve?
Reducing residual emissions from CCS operation by 50% or more (i.e. by increasing capture levels from current 90% to 95%) will make a significant contribution to achieving net-zero GHG emission targets, and thus benefit society as a whole.
UK government policy-makers and regulators will also benefit. This work will make a direct contribution to helping CCS deliver UK domestic GHG emission targets and the project will communicate directly with the BEIS CCUS team and the Environment Agency to communicate the results in the contexts of financial incentives for higher capture levels and plant permitting. It will also contribute to the UK’s COP26 initiative, including through collaboration with international organisation partners such as the International Test Center Network and the UNECE.
UK industry and its customers for electricity, hydrogen and other decarbonised manufactured products will benefit from well-evidenced research on how the required net-zero targets can be achieved effectively with the widely-applicable post-combustion capture amine technology.
Other researchers will be able to build on the pilot plant experimental results obtained, for example in improving process model performance. The solvent storage technique for pilot-scale testing that will be developed and demonstrated is also highly significant for research at this scale since it will allow pilot plants to investigate advanced operating conditions that would otherwise be unattainable. Oxygen-in-CO2 measurements are also likely to lead to further fundamental work on solvent oxidation phenomena as well as being immediately useful in their own right.
Industry and researchers will also benefit from the development of lab-scale thermal reclaiming equipment; this can provide immediate information to support practical deployment as well as support the necessary underpinning fundamental research on the topic.