Fundamental Processes of Solid and Liquid Biofuels Combustion

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Fundamental Processes of Solid and Liquid Biofuels Combustion Wood and other biomass fuels, both solid and liquid, are attractive as “carbon-neutral” energy resources. Their efficient utilisation requires a thorough understanding of their processes of combustion, and this proposal addresses the development of computational tools for some aspects of biofuels combustion and their experimental verification. Common to all the projects is the need to deal with mixtures, both solid and liquid, of some complexity. Solid biomass fuels are most often burned or gasified in a packed bed: a non-fluidized bed of fairly large fuel particles on a grate. This is a complex process that as yet is not as well understood as many combustion processes. Practical fuels are usually mixtures with a wide range of different particle sizes and shapes, and often have several components with different combustion characteristics as well (e.g. wood wastes). The work proposed will develop methods for dealing with such mixtures in a numerical model of packed bed combustion, and will conduct experiments on a range of fuels to verify the model. Particles of fuels such as wood chips can also overlap in the bed, reducing the surface area available for combustion significantly. Methods will be developed to measure this effect through pressure loss tests on the bed. The effects of fibre orientation (grain) on combustion and pyrolysis will also be investigated. Most liquid biofuels, like conventional petroleum fuels, are mixtures with large numbers of components, and may be modelled effectively as continuous mixtures, representing them as one or more probability density functions rather than in terms of discrete species. This proposal will further develop continuous thermodynamics techniques for modelling the evaporation and combustion of liquid biofuels. The two areas of particular interest are methods are needed to describe chemical reaction kinetics of complex mixtures in order to model ignition and combustion, and the treatment of non-ideal phase equilibrium for polar compounds such as alcohols found in many biofuels.