STEAM PRODUCTION FROM A BIOMASS WITH HIGH CONCENTRATION OF ASH AND NITROGEN EMPLOYING FIXED-BED GASIFICATION FOLLOWED BY TWO-STAGED COMBUSTION

摘要

175kWth steam production from 3.6 ton/day spent mushroom substrate with high concentration of ash and nitrogen was demonstrated employing a drier, a pelletiser, a downdraft fixed-bed gasifier, a producer gas fired furnace and a heat recovery steam generator. Since load following operation at weekly start and stop cycle will be required in the practical use in mushroom industry, a 100 hours test was performed both at part load and at full load to examine the performance of this configuration. In order to avoid severe clinker trouble owing to ash sintering, the gasifier was operated at a low temperature. The producer gas properties varied less between part load and full load, and the producer gas was well combusted without any auxiliary fuel in the furnace. Two-staged combustion in the furnace was very effective to reduce NOx emission and its concentrations were far below the local regulation without any NOx removing equipment. Steam generation efficiencies from the feedstock to steam at 64% load and at 97% load were almost the same.