Combustion Characteristics of Coal and Biomass Blends with Adding Absorbing Sulfur Agent

Abstract

The combustion characteristics of coal and biomass blends with adding adsorbing sulfur agent was investigated using thermogravimetric analyzer. The results indicated that the combustion process of the blends were similar to that of pure coal and biomass, which there were two apparent weight-loss peaks--one for volatile burning and another for char burning. The combustion stages could be divided into the dewatering period, volatilization and burning, char burning and burnout. Nevertheless, the combustion characteristics of blends varied with the biomass blending ratio and Ca/S ratio. Due to the increase of biomass blending ratio, the volatile matter content of blends increased, which leaded to the increase of peak value for volatile burning stage. In this stage, due to the lower reaction temperature, less SO2was produced and the reaction to CaO was slower. With the progress proceeding, char began to be burned and large heat was released and the adsorbing sulfur reactions were becoming stronger. Although the mass of blends reduced fastly, the mass of CaSO3and CaSO4increased compared to CaO, Which leaded to a wider temperature range of weight-loss for the char burning period. At the same linear temperature gradient, an increase of Ca/S decreased the temperature of volatilization and char burning, and the residue was increased due to more CaO additive. Therefore, the appropriate ratio of Ca/S was necessary to improve the combustion and adsorbing sulfur efficiency. In this study, a basic kinetics analysis for coal and biomass blends is provided. The kinetics parameters reveal that the combustion process of coal and biomass blends with adding absorbing sulfur agent can be described by a first order reaction equation.