Experimental investigation on the coal combustion in a pressurized fluidized bed

Pressurized oxy-coal combustion is considered as one of the most promising carbon capture technologies in terms of high carbon capture efficiency and low cost. However, practical operational experience with pressurized coal combustion in a fluidized bed, especially with continuous coal feeding, is still very limited. In this study, a pressurized fluidized bed combustion system was developed and a series of coal combustion experiments were carried out with continuous coal feeding under the pressures from 0.1 to 0.4 MPa. The effects of the combustion pressure and stoichiometric air coefficient on the fluidized bed combustion performances of a Chinese lignite in terms of the temperature distribution profile, apparent solid holdup, combustion efficiency, conversion ratio of carbon in coal to CO2 and ash composition were investigated. The experimental results show that an increase in pressure is beneficial to the improvement of combustion efficiency, and the positive effect of increasing stoichiometric air coefficient on the conversion ratio of carbon in coal to CO2 is more obvious with a lower combustion pressure. The bottom ash and fly ash have similar chemical compositions under different pressures. Based on the experimental data, a correlation as the functions of pressure and stoichiometric air coefficient is proposed to predict the conversion ratio of carbon in coal to CO2