The inorganic matter in biomass causes two- fold effect during combustion – foulingand slagging of boiler and emission of sub -micron particles. The inorganic matter indifferent biomasses varies from 1 to 10 percent on dry basis. A significant proportionof this inorganic matter evaporates during devolatilisation, during which 70-90% ofinorganic mass also devolatilises. Some inorganic matter in the char is also released ingas phase during combustion. The inorganic matter released in gas phase condenseshomogeneously to form sub-micron fume or heterogeneously on to already existingfine particles. The remaining inorganic matter may coalesce to form larger ashparticles.Chemical fractionation on biomass is a common technique used to classify theinorganic matter into water-soluble, ammonium acetate soluble and hydrochloric acidsoluble components. The chemical fractionation analysis for three most commonbiomass materials found in Australia - radiata pine, bagasse and eucalyptus, has beenused to estimate the character of char formed during co mbustion of these biomassmaterials. The char is generated from these biomass samples using a drop tubefurnace and collected in cyclone and on filter paper.A mechanistic model is presented here for estimating the ash character on the basis ofchemical fractionation of the biomass.
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