Achievement of high CO₂ concentration in the flue gas at slightly positive pressure during oxy-coal combustion in a 300 kW_th furnace

Abstract This study explores the combustion characteristics of a 300 kW_th air-firing furnace adapted for oxy-firing combustion. The influences of operating pressure and oxygen/recycled flue gas (RFG) blend ratio on the combustion characteristics of oxy-coal firing were examined, especially on the exhausted CO₂ concentration. High purity CO₂ (94.1%) at the exit of the system was achieved for oxy-coal combustion at the optimized operation conditions (i.e., an RFG flow rate of 227 Nm³/h, feeding rates of oxygen and coal of 42.5 Nm³/h and 21 kg/h, respectively, and a slightly positive pressure of +100 Pa). The achievement of 94.1% CO₂ emission has great potential for reducing CO₂ emissions by carbon capture and storage and thus mitigating global climate change. Moreover, compared with air-firing operation, an NO emission reduction of around 66% was obtained in the oxy-firing operation.