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

Abstract

A new scheme of oxyfuel combustion combined with partial removal of CO 2 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 O 2 concentration decreased, the gas recirculation ratio, SO 2 concentration, and global efficiency of in-furnace desulfurization increased. On the other hand, the gas recirculation ratio, SO 2 concentration, and global efficiency of in-furnace desulfurization increased as the CO 2 removal ratio increased. The practical residence time of SO 2 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 CO 2 from recycled gas, and MILD combustion, to the high desulfurization efficiency, were almost the same importance. At CO 2 removal ratio = 11% and initial O 2 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 CO 2 recovery.

Flame Characteristics of CH4/H2 on a Jet-in-Hot-Coflow Burner Diluted by N2, CO2, and H2O

“…11,16 Furthermore, SO X emission was indicated to be lower as compared to conventional oxy-fuel operation. 14 The contribution of gasification reactions of char was found enhanced due to lower local oxygen presence, and this could alter the whole combustion mechanism for solid fuels under oxy-MILD condition. 12,17 However, oxy-MILD combustion also has disadvantages in decreasing the burnout ratio, which is thought mainly due to the insufficient residence time of particles inside the furnace.…”

“…The idea of combining oxy-fuel combustion with MILD combustion was initially taken into practice in the field of steel reheating using commercial burners, such as REBOX, , and it was reported to be more cost-effective, environmentally friendly, and has greater potential of reducing scale formation than conventional reheating technologies. To extend the application of oxy-MILD combustion to solid fuels, plenty of studies have been conducted for both pulverized coal and saw-dust. − It was reported that oxy-MILD combustion obtains a greater potential on reducing NO X emissions from not only thermal-NO X route but also fuel-NO X route. , Furthermore, SO X emission was indicated to be lower as compared to conventional oxy-fuel operation . The contribution of gasification reactions of char was found enhanced due to lower local oxygen presence, and this could alter the whole combustion mechanism for solid fuels under oxy-MILD condition. , However, oxy-MILD combustion also has disadvantages in decreasing the burnout ratio, which is thought mainly due to the insufficient residence time of particles inside the furnace .…”

Numerical study of H 2 O addition effects on pulverized coal oxy-MILD combustion

“…The applications also indicate a higher thermal efficiency under oxy-MILD combustion than conventional oxy-fuel combustion or air-MILD combustion. As for coal oxy-MILD combustion, the corresponding studies are quite sparse, however, the latest literatures still can be found elsewhere [32][33][34][35][36].…”

“…Liu et al [34] found that the practical residence time of SO 2 under coal oxy-MILD combustion increased to about five to thirteen times as long as that of the conventional combustion. Moreover, they demonstrated that oxy-MILD combustion could realize extremely high desulfurization efficiency together with easy CO 2 recovery during coal combustion.…”