CFD modelling of oxy-coal combustion in an entrained flow reactor

Oxy-fuel combustion is seen as one of the major options for CO2 capture for both new and existing coal fired power stations. Coal is burned with a mixture of oxygen and recycled flue gas to obtain a rich CO2 stream ready for sequestration. Computational fluid dynamics (CFD) tests for coal combustion under different O2/CO2 (21-35% vol O2) atmospheres in an entrained flow reactor (EFR) were carried out using three coals of different volatile matter content. The temperature profiles, burning rates, burnout and concentration of major species, such as O2, CO2, CO, were predicted and compared with an air reference case. A decrease in gas temperature and burning rate was observed for 21% O2/79% CO2 environment in comparison to the air reference case due to the difference in gas properties between N2 and CO2. Experimental coal burnouts obtained in the EFR, were used to test the accuracy of the CFD model. The numerical results showed a decrease in coal burnout when N2 was replaced by CO2 for the same oxygen concentration (21%), but an improvement in the O2/CO2 atmosphere for an oxygen concentration higher than 30%. The numerical results for oxy-coal combustion were in good agreement with the experimental results.