Ash behaviour of lignocellulosic biomass in bubbling fluidised bed combustion

The purpose of this work is to characterise biomass ash behaviour in a bubbling fluidised bed (BFB) combustion pilot plant (1 MWth) with silica as the bed material and using a woody biomass, poplar, and a herbaceous biomass, Brassica carinata. Ash characterisation and mass balances of the inorganic elements with relevance for bed agglomeration, fouling and emissions were performed in the BFB combustion pilot plant.The agglomerates formed in the silica bed material have not been found to be associated with chemical reaction sintering related to gas–solid reaction such as the formation of CaSO4 and CaCO3. Therefore this chemical reaction mechanism is neglected when it is compared to the bed agglomeration based on the partial melting of the alkaline compounds contained in the biomass ash. Similarities of crystalline phases and elemental content between ash deposited on the tubes and biomass ash obtained in laboratory at 550 °C enable to the laboratory tests of ash melting behaviour to predict the sintering in the ash deposited on the heat exchangers of the thermal plants.