NOx and SO2 emissions from municipal solid waste (MSW) combustion in CO2/O2 atmosphere

The NOx and SO2 emissions from MSW combustion in CO2/O2 atmosphere were studied using a lab-scale electrically heated tube furnace. The shape, peaks location, and peaks values of NOx concentration curves all changed with temperature. In comparison, regarding these three characteristics of SO2 concentration curves, only peaks values were affected by temperature. The shape and peaks location of NOx and SO2 concentration curves changed with atmosphere indistinctively, but their peaks values, maximal average emissions, and the corresponding temperature were affected by atmosphere. Replacement of N2 by CO2 reduced NOx emission when the temperature was higher than or equal to 800 °C, but reduced SO2 emission when the temperature was lower than 1000 °C. At 1000 °C, some improvement measures, such as adding appropriate sorbents, were required in 80CO2/20O2 to achieve removal characteristics of SO2 and NOx simultaneously. The maximal desulphurization efficiency of CaO in 80CO2/20O2 atmosphere (34.4% at 800 °C) or limestone in 80N2/20O2 atmosphere (23.4% at 900 °C) was lower than that of limestone in 80CO2/20O2 atmosphere (43.3% at 1000 °C), indicating that direct sulfation in 80CO2/20O2 atmosphere was favourable for high desulphurization degree and consequently enabled better sorbent utilization. Besides, to obtain higher desulphurization efficiency at high temperature, Ca/S ratio should be increased.