Observation of simultaneously low CO, NOx and SO2 emission during oxy-coal combustion in a pressurized fluidized bed

Pressurized oxy-fuel combustion is a promising technology for CO2 capture with respect to its high combustion efficiency and the simultaneous reduction of gaseous pollutants. A 10 kWth bubbling fluidized bed reactor with continuous coal-feeding was designed, and effects of pressure, temperature and fuel types on pollutant emission were investigated in detail. Generally, the relatively low carbon content in the ash and CO concentration in the flue gas demonstrated that the combustion efficiency was improved by high pressure. The concentration of NO, N2O and SO2 showed decreasing trends with the increase of pressure. Moreover, the effect of pressure on the emission of NO and SO2 in the lower pressure (≤0.3 MPa) was more pronounced than that in the higher pressure. The concentrations of NO and SO2 correlated positively with temperature, while for N2O, it had a negative correlation. Compared with air combustion, NO and SO2 emission dropped sharply in 21%O2/79%CO2 atmosphere. However, N2O concentration during oxy-combustion was slightly higher than that in air combustion in the range of experimental pressure.