Experimental Investigation of Oxy-coal Combustion in a 15 kWth Pressurized Fluidized Bed Combustor

Pressurized oxy-coal combustion is considered as a promising carbon capture technology as a result of its potential of high efficiency and low cost in CO2 capture. However, experimental investigations of oxy-coal combustion under pressurized conditions are far less common than those under atmospheric pressure conditions, and hence, further research is needed to elucidate the effects of pressure on oxy-coal combustion in terms of combustion performance, emissions, etc. In this study, a series of oxy-coal combustion experiments were carried out under the pressures from 0.1 to 0.4 MPa on a 15 kW(th) fluidized bed combustion system. The effects of the combustion pressure and oxygen concentration in the oxidant on the temperature profile, unburnt carbon, combustion efficiency, fly ash composition, and NOx emission were investigated. The experimental results have shown that the CO2 concentration in the oxy-combustion flue gas under different combustion pressures have all exceeded 90%, which is beneficial to the carbon capture process. An increase in pressure is helpful to reduce the unburnt carbon in the fly ash and improve the combustion efficiency under all of the tested oxy-combustion atmospheres. The NOx emission decreases with combustion pressure within the investigated range of 0.1-0.4 MPa, while the reduction is more pronounced at lower pressures. Besides, the effect of combustion pressure on the chemical composition of the fly ash is found to be insignificant.