Experimental study of SO2 emissions and desulfurization of oxy-coal combustion in a 30 kWth pressurized fluidized bed combustor

Pressurized oxy-fuel combustion (POFC) has attracted wide attention due to its potentials of high efficiency and low cost in CO2 capture. Compared with numerical simulation and system analysis, there are few experimental studies about POFC. In order to investigate the SO2 emissions and desulfurization behaviors of limestone under continuous fuel-feeding POFC conditions, a series of oxy-coal combustion experiments were conducted with a 30 kW(th) pressurized fluidized bed combustor. The results showed that the SO2 emission was almost independent of combustion pressure and excess oxygen coefficient, while it was higher in air than in O-2/CO2 atmosphere because less sulfur was retained by the coal ash. Although the higher CO2 partial pressure caused by an increase in combustion pressure from 0.1 MPa to 0.4 MPa had negative effects on the calcination of limestone and inhibited the indirect desulfurization, the higher combustion pressure was beneficial to improve the direct desulfurization efficiency. An increase in combustion temperature from 850 degrees C to 950 degrees C significantly improved the desulfurization efficiency of limestone with both atmospheric and pressurized oxy-coal combustion. SEM images were obtained and used to show the surface morphology of limestone products under different combustion conditions, which was helpful to the understanding of the desulfurization behaviors of limestone.