There is currently huge interest in carbon capture and sequestration as a means of reducing carbon dioxide emissions, and hence combating climate change. Unfortunately, current methods for achieving this are considered uneconomic because they require massive absorption plant, with the ensuing capital and operating costs, and because of the high cost of regenerating the chemical absorbents used. Moreover, many of the chemical absorbents used, such as MEA (monoethanolamine), are very corrosive and toxic and have their own significant environmental consequences. So, technologies that can dramatically reduce the costs of carbon capture whilst avoiding the use of harsh chemicals are urgently needed.This proposal will investigate a novel idea in absorption process technology that could initiate a major step forward in reducing CO2 emissions. The aim of the work proposed here is to investigate the feasibility of this novel absorption process in the context of carbon dioxide capture. A coordinated programme of theory and experiment will be used to tackle this problem. Molecular theory and simulation studies will be used to gain insight into the novel absorption process. This insight will be used to inform bench-top experiimental studies, which will aim to test a variety of systems and demonstrate feasibility, as well as provide data for an energy model.If the process is feasible it might allow absorption plant to be much smaller and use ore benign absorbent checmicals. If ultimately it is found to be efficient then it could make a significant contribution to reducing carbon dioxide emissions.
The aim of this work was to investigate the potential for a new kind of gas separation process, especially in the context of carbon capture. The key idea was to investigate the gas separation potential of a system consisting of a porous material support loaded with a solvent, and to understand the effect of varying the solvent partial pressure, i.e. the solvent is a vapour below its saturation pressure. The first outcome showed unexpected and previously unknown behaviour for 'physical' solvents, i.e. solvents that interact with carbon dioxide relatively weakly. Essentially, the equilibrium performance of the separation process could be better, in terms of capacity and selectivity, with the solvent than without, provided that the solvent partial pressure is suitably tuned to the pore size of the porous material. A later outcome showed that this effect can be enhanced by optimising the type of solvent used, and that acetonitrile is potentially a good solvent to use in experiments.
However, later work showed that this process would be very sensitive to the details of the pore network, and so materials with very well controlled pore sizes and shapes would be essential. Such materials would are likely to be too expensive for carbon capture applications.
Nevertheless, this work indicates that a successful and efficient process might be designed when 'chemical' solvents are used, i.e. solvents that react with carbon dioxide, typically amines. So this work provided the platform on which to build another project based on using chemical solvents, which is now funded by EPSRC.
 Equilibrium behaviour of a novel gas separation process, with application to carbon capture, Sweatman, M. B. 1-Jul-2010 In : Chemical Engineering Science. 65, 13, p. 3907.
 Improving the equilibrium performance of active carbons for separation processes by co-adsorption with low pressure solvent: application to carbon captureSweatman, M. B. Aug-2011 In : Adsorption. 17, 4, p. 723.
 FEASIBILITY OF A WETTING LAYER ABSORPTION CARBON CAPTURE PROCESS BASED ON CHEMICAL SOLVENTS, Sweatman, M., Fletcher, A. & Patwardhan, S.
1/10/12 → 30/09/15, £568,433, EPSRC (Engineering and Physical Sciences Research Council), Project: Funded.