Effect of reactant types (steam, CO2 and steam + CO2) on the gasification performance of coal using entrained flow gasifier

This study investigates the gasification behaviour of bituminous coal using different reactants of CO2, steam and a mixture of CO2 and steam under entrained flow gasification conditions at temperatures of 1000 degrees C and 1200 degrees C with atmospheric pressure. The major gas constituents of the syngas were measured using online micro-GC with a model number Varian 490, whereas the minor pollutant gases were analysed using Kitagawa gas detection tubes. A maximum carbon conversion of 86% was achieved under steam gasification at a temperature of 1200 degrees C compared to 74% from CO2 gasification. The higher carbon conversion from steam gasification is due to the higher gasification reactivity than CO2 gasification. At 1000 degrees C, the lower heating value (LHV) from steam gasification was determined to be 60%, 70% and 80% higher than that of CO2 gasification using the reactant concentrations of 10, 20 and 40 vol.%, respectively. Using a stoichiometric 50/50 ratio of CO2 and steam, the yield of H-2, CO and CH4 were increased by 56%, 106% and 35% compared to that of pure CO2 gasification. At 1000 degrees C, the LHV under mixed reactant condition is close to the LHV from the pure steam gasification at 1200 degrees C. In steam gasification, increasing the temperature by 200 degrees C from 1000 degrees C decreases the LHV by 17 and 10% using 10 and 20 vol.% steam. The higher heating value from steam gasification is due to the H-2 and CH4-rich syngas compared to CO-rich syngas in CO2 gasification. The BET surface area of the solid char from steam gasification is about 17 and two times higher than that of CO2 gasification at 1000 degrees C and 1200 degrees C, respectively.