Scalable step-change carbon materials achieving high CO2 adsorption capacity and selectivity at practical flue gas temperatures for potential breakthrough cost reductions
Why is this research needed?
The development of affordable CO2 capture technologies has never been so urgent due to the pressing need to implement carbon capture, utilisation and storage (CCUS) as a critical part of the drastic and far-reaching measures needed to tackle climate change, as highlighted by the IPCC special report 2018. The UK’s Climate Change Committee (CCC) and UK CCUS Cost Challenge Task Force report recommends that to climate change 2050 target, the UK’s first CCUS cluster needs to be operational by 2026, storing approximately 10 MtCO2 each year by 2030 and at least 20 MtCO2 each year by 2035, subject to cost coming down sufficiently”. The UK’s task force report emphasises that the “key is combination of capture materials with lower regeneration energy requirements combined with improved (intensified) process devices which lower capex and opex” and “new processes designed to vastly reduce or eliminate the energy penalty of regenerating CO2 from a captured state”. However, despite the substantial progress achieved so far, the energy cost of currently best available capture remains still high at 2.4~2.5 GJ for both advanced solvents and solid polyamine sorbents.
Therefore, new capture technologies need to be developed as a matter of urgency for breakthrough cost reductions. As highlighted by the Mission Innovation Carbon Capture Innovation Challenge, adsorption-based capture systems offers enormous potential for revolutionary advances in cost reduction, with physical adsorbents showing the most promise. Among numerous capture materials that have been investigated (e.g. supported/grafted polyamines, MOFs and ZIFs and many others that can be named), carbon-based adsorbent materials appear to be the most promising class of capture materials, thanks to their unparalleled extraordinary properties, such as superfast adsorption kinetics, moderate heat of adsorption, high selectivity and extraordinary chemical stability against thermal, oxidative and hydrolytic degradation. However, none of the best-performing carbon and other physical adsorbents ever reported are currently able to achieve appreciable levels of CO2 capacity at sensible or realistic flue gas temperatures (40 – 50 oC or higher), which are generally well below 1.0 mmol- CO2/g or 4.4 wt% in spite of their high capacities at 0 or 25 oC. This essentially means that costly flue gas refrigeration down to very low temperatures will be required for applications of physical adsorbents in post-combustion carbon capture. Therefore, how to boost the adsorption performance of physical adsorbents for post-combustion carbon capture has been a major challenge over recent years.
What is this research investigating?
Based on our extremely encouraging initial results, the proposed research aims to develop and test at sensible scales a new class of carbon materials able to achieve high capture capacities with high selectivity at realistic flue gas temperatures and low CO2 partial pressures, which might lead to potential breakthrough cost reductions in carbon capture. Using a novel integrated compaction-combined carbonisation-activation methodology, the research will firstly involve the preparation of a range of carbon adsorbent materials from a special type of polymeric materials as the feedstock, which is also widely available as recycled waste in large quantities. The materials will then be characterised and tested for CO2 capture at various scales in realistic flue gas conditions, and the energy penalty of a adsorption-based capture system using the carbon material as the sorbent will be evaluated.
What does the research expect to find?
Based on our initial results obtained, it is expected that given the desirable moderate heat of adsorption and high CO2 capacity and selectivity at relatively high flue gas temperatures, the carbon-based capture materials with temperature swing adsorption can potentially reduce the energy penalty of CO2 capture by 40-50%, relative to both advanced solvents and polyamine adsorbents.