Efficient Desulfurization in a New Scheme of Oxyfuel Combined with Partial CO2 Removal from Recycled Gas and MILD Combustion

摘要

A new scheme of oxyfuel combustion combined with partial removal of CO2 from recycled gas and MILD combustion was proposed. Through experiments and theoretical analysis including the Monte Carlo method, the characteristics of in-furnace desulfurization in this new scheme was investigated. It was found that as the initial O2 concentration decreased, the gas recirculation ratio, SO2 concentration, and global efficiency of in-furnace desulfurization increased. On the other hand, the gas recirculation ratio, SO2 concentration, and global efficiency of in-furnace desulfurization increased as the CO2 removal ratio increased. The practical residence time of SO2 in oxyfuel-MILD coal combustion increased to about five to thirteen times as long as that of conventional pulverized coal combustion. The contributions of oxyfuel combustion, partial removal of CO2 from recycled gas, and MILD combustion, to the high desulfurization efficiency, were almost the same importance. At CO, removal ratio = 11% and initial O2 concentration = 16%, the gas recirculation ratio became as high as 99.12%, i.e., only 0.88% of the flue gas was exhausted to the atmosphere. The corresponding system desulfurization efficiency was as high as 95.8%. It was demonstrated that this new scheme can realize extremely high in-furnace desulfurization efficiency in addition to easy CO2 recovery.