Effect of fuel properties on biomass combustion: Part I. Experiments—fuel type, equivalence ratio and particle size

Moving bed combustion is commonly used for energy conversion of biomass. Conditions on the moving bed can be conveniently represented by a time dependent fixed bed. The present work experimentally investigates the combustion of four biomass materials having different fuel properties in a fixed bed under fuel-rich conditions. Temperature, gas composition and mass loss curves identified two distinct periods as the combustion progresses in the bed: the ignition propagation and char oxidation. The effects of bulk density, particle size and air flow rate on the combustion characteristics during the two periods are interpreted by using the ignition front speed, burning rate, percentage of mass loss, equivalence ratio and temperature gradient. Different channelling of air was observed for small miscanthus pellets and large wood particles due to the fast propagation of the ignition front around a channel. The elemental ash composition was also analysed, which explained the sintered agglomerates of miscanthus ashes in terms of alkali index.