The Characteristics Research On Biochar Gasification Reaction With Steam

The gasification technology is one of the main ways of biomass energy utilization.It can improve the use efficiency of biomass energy. Biochar is the solid productremained with the volatile precipitation in the process of biomass pyrolysisgasification. The volatile content and oxygen content of biochar are greatly reduced，it is enrichment of the fixed carbon and has rich pore structure, so it is a kind ofhigh-quality gasification materials. This article selected rice husk and sawdust as theresearch object, and studied the characteristics of biochar gasification reaction withsteam.Make the char of rice hull and sawdust on the use of muffle furnace and study theinfluence of temperature and particle size distribution and residence time to the charyield. It shows that temperature is the main factor affecting the biochar yield. In600℃-900℃, the yield of the rice husk and sawdust char decreases significantly withthe increase of temperature, and under the same temperature conditions, the longer theresidence time, the less biochar yield. Under low temperature, the smaller size ofbiomass particles, the higher char yield. But when the temperature is higher than800℃, the difference of the char yield of biomass in different size is very small. Thedifference of the surface morphology of rice husk and sawdust char which are made indifferent condition are studied by the Scanning Electron Microscopy. Study theinfluence of temperature to the pore structure by the Accelerated Surface Area andPorosimetry System.Design a biochar steam gasification reaction test bed and study the steamgasification reaction properties of biochar on different conditions by experimentalresearch. The result shows that temperature is the main influence factors of biocharsteam gasification. In700℃-950℃, the rice husk and sawdust char have a conversionefficiency with the increase of temperature. When the temperature reached950℃andthe retention time remained12minutes, the conversion of rice husk and sawdust charrate are90.73%and89.9%respectively. When the temperature is higher than850℃,the reaction rate of rice husk and sawdust char increase obviously. And smaller particle size and lower making temperature is conducive to improve the activity ofbiochar gasification. The ingredients of rice husk and sawdust char steam gasificationgas are CO, CO₂, H₂and CH₄. Temperature and steam flow rate are the main factorsinfluencing the gas composition. High gasification temperature and water vapor flowis advantage for hydrogen generation, and the gas content of H₂is46.9%and55.3%respectively when the gasification temperature of rice husk char and sawdust char is950℃and the steam flow rate is2.64g/min.Chose the nuclear reaction model and homogeneous reaction model and use theexperimental data to fit with the reaction models. The result shows that when theconversion is in15-75%, the nuclear reaction model can describe the biochar steamgasification reaction behavior better than the homogeneous reaction model. Thereaction kinetics parameters of the two kinds of model are worked out.