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Chemical Looping Combustion paper in Applied Energy

last modified Mar 14, 2018 11:02 AM
Chemical Looping Combustion paper in Applied Energy

Vice Chancellor Prof Stephen Toope, Prof Lisa Hall, Prof John Dennis, Martin Chan, Matthias Schnellmann. Click on the image for a larger version.

Researchers have identified a way to reduce the capital and operating costs of chemical looping combustion, or CLC, a promising technology for capturing emissions of carbon dioxide from the combustion of fuels.  These findings have been reported in a recent article in the journal, Applied Energy: The effect of different particle residence time distributions on the chemical looping combustion process. The authors are Matthias Schnellmann and John Dennis from this department, with Felix Donat, Stuart Scott and Gareth Williams.

In CLC, the oxygen to burn the fuel comes from solid particles of an inorganic oxide (the 'oxygen carrier', e.g. copper oxide), instead of from oxygen in air.  Thus only carbon dioxide and water leave the 'fuel reactor'.  The water is condensed, leaving pure carbon dioxide.  The oxygen carrier is regenerated by oxidising it in air in the 'air reactor'.  CLC captures carbon dioxide inherently and therefore more efficiently than existing techniques, such as post-combustion capture using amine scrubbing.

By using a model that is general to any CLC process, the authors were able to identify that the extent to which the particles are mixed in the two reactors is important.  The extent of mixing is generally described by a function known as a residence time distribution, which gives the distribution of times that particles spend in a reactor.  By decreasing the extent of mixing, the authors found that both the inventory of oxygen carrier particles in the process, and the circulation rate of particles between the air and the fuel reactor could be substantially reduced.  In this way the capital cost could be reduced since smaller reactors would be sufficient and less oxygen carrier material would be required.  The operating costs would also be lower since less energy would be required to circulate the particles between the two reactors.