Research On Process Of Catalytic Gasification Of Brown Coal And Biomass With Solid Heat Carrier

A new process of catalytic gasification of brown coal/biomass has been proposed. The gasifier is composed of two zones, a gasification zone and a combustion zone. A circulation loop of bed material is created between these two zones, but the product gas and flue gas remain separated. The circulating bed material acts as heat carrier together with some charcoal circulates from the gasification zone to the combustion zone. The exothermic reaction in the combustion zone provides the energy for the endothermic gasification with steam.In this experimental study, the steam gasification of Dayan brown coal and biomass with olivine as catalytic solid heat carrier was carried out in a bench scale test facility (1.0kg/h biomass). The effects of reactor temperature (650-800℃), steam/coal ratio(0-1.2), bed materials layer height(0.05-0.6m), coal/biomass particle size(0.178-3.35mm) and different catalysts(sand, olivine, limestone) on composition, gas yield, calorific value of the product gas, carbon conversion and chemicalefficiency in the catalytic coal/biomass gasification had been determined.The results showed that effect of temperature is remarkable. For Dayan brown coal, gas yield, hydroge content, carbon conversion and chemical efficiency increase with the increase of gasification temperature under the experimental conditions. The effects of the S/C (steam/coal), bed materials layer height and particle size are complex, the three parameters' optimal value are 0.4 ~ 0.6, 0.3m and 20-40mesh. It is found that the calcined olivine is more active than silicon sand for steam gasification. The olivine met the requirement of attrition resistance and no deactivation during the experiment is found.In addition, the steam gasification of pine sawdust with olivine as catalytic solid heat carrier for hydrogen rich gas was carried out. The preferable process parameters is that 800℃ of temperature, 0.8 of S/B(steam/biomass), 0.4m of the bed materials layer height and 20-40mesh of the biomass particle size. Under these conditions, the hydrogen yield is 83.0g/kg (daf.), the hydrogen composition of product gas is 54.35% (mol.%), and the tar concentration is 0.74g/Nm~3 (dry gas). The pine sawdust was better than apricot stones for the steam catalytic gasification for hydrogen.A thermogravimetric study was carried out by the coke-burning regenerationkinetics of catalyst. Some kinetics data of carbon combustion are presented and the activation energy of coke-burning is 100-140kJ/mol.