Abstract

Coal is used for around 39% of global production of electricity. Despite being one of the most polluting fossil fuels, in terms of mass of CO2 emitted per unit of power generated, the use of coal is projected to increase from present day levels by ~ 80% by 2030. It is, therefore, imperative to find ways of using it for power generation whilst avoiding the release of CO2 into the atmosphere. The currently-available technology for CO2 separation is by scrubbing the flue gases with, e.g. monoethylamine (MEA): however, this technique comes with a large energy penalty because of the large heat requirement for regeneration of the solvent, reducing the efficiency of the power plant by up to one-third.

Chemical-looping combustion (CLC) has the inherent property of separating CO2 from flue gases without the energy penalty associated with amine scrubbing. Instead of air, it uses an oxygen-carrier, usually in the form of a metal oxide, to provide oxygen for combustion. This presentation will deal with the application of chemical looping to the combustion of solid fossil fuels and will highlight research being undertaken on this topic. Further work on a modification of chemical looping will be described, involving the oxides of iron in packed bed reactors, to produce hydrogen of high purity from low-grade synthesis gas. This offers substantial benefits in terms of the distributed production of hydrogen, avoiding costly transport of the gas by a dedicated grid.

John Dennis was a Lecturer in the Department of Chemical Engineering from 1984 to 1989 having previously been an undergraduate and PhD student there. During this period he published on the control of sulphur emissions from fluidised bed combustors and on the problems of gas combustion in fluidised beds. He left Cambridge to become an engineering consultant in 1989 specialising in the solution of difficult process or economic problems, with areas of technical interest including heat and mass transfer in reactors, combustion, and fluidised bed reactions. He has had close involvement with collaborative research involving academia and industry. He returned to the University and was a University Lecturer from 1st October, 2002, Senior Lecturer from 1st October, 2004 and Reader in Chemical Reaction Engineering from 1st October, 2008. Recent areas of research include the fluidised bed gasification of biomass, fundamental studies of fluidised bed hydrodynamics using MRI , discrete element modelling of fluidised beds, clean coal technology using chemical looping and other techniques, and, as a separate area, the use of microalgae for biofuels.