Simultaneous easy CO2 recovery and drastic reduction of SOx and NOx in O2/CO2 coal combustion with heat recirculation☆

Coal combustion with O2/CO2 is promising because of its easy CO2 recovery, extremely low NOx emission and high desulfurization efficiency. Based on our own fundamental experimental data combined with a sophisticated data analysis, its characteristics were investigated. It was revealed that the conversion ratio from fuel-N to exhausted NO in O2/CO2 pulverized coal combustion was only about one fourth of conventional pulverized coal combustion. To decrease exhausted NO further and realize simultaneous easy CO2 recovery and drastic reduction of SOx and NOx, a new scheme, i.e. O2/CO2 coal combustion with heat recirculation, was proposed. It was clarified that in O2/CO2 coal combustion, with about 40% of heat recirculation, the same coal combustion intensity as that of coal combustion in air could be realized even at an O2 concentration of as low as 15%. Thus exhausted NO could be decreased further into only one seventh of conventional coal combustion. Simultaneous easy CO2 recovery and drastic reduction of SOx and NOx could be realized with this new scheme.