Ash related problems with high alkalii biomass and its mitigation - experimental evaluation
evaluación experimental
Keywords:
Biomass ash, Alkalii, Leaching, Fusion, FoulingAbstract
Biomass is regarded as a renewable source of energy and is playing a role in future fuel supply trend, with great acceleration. However, due to the chemical composition of the ash of certain types of biomass (particularly short rotation crops like grasses, canes and straws), boiler
related problems have occurred systematically in the past. These fuels are rich in alkaline metals (potassium, phosphorus, chlorine and sodium) which form complex eutectic salts that effectively lower the melting point of the ashes during combustion and cause fouling and slagging problems, especially in superheater tubes. This work reviews the latest investigations regarding the prediction of these problems through the evaluation of the ashes in the laboratory and discuss their mitigation by fuel leaching and blending. As a means to demonstrate the methodology, experimental data related to the evaluation of the Common Cane are presented, resulting from our own laboratory tests. These include fusion/sintering tests of ashes sampled from canes in the as-is and waterleached condition and the comparisons with other more traditional biomasses. The results show that the as-is state would be unacceptable to burn, but leaching with water and/or blending with
more stable ashes reduces the detrimental effects on boiler components to a tolerable level.
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