Combustion Efficiency and CO 2 Emission from O 2 /N 2,O 2 /CO 2,and O 2 /RFG Coal Combustion Processes

This study investigated the combustion efficiencies and emission characteristics of oxygen/recycled flue gas (O₂/RFG) coal combustion processes. The effects of different operating conditions such as the feed gas compositions and concentrations, and the ratios of RFG were also discussed. Experimental results showed that the average concentration of CO₂ produced in O₂/CO₂ combustion was higher than 92%, while the maximum concentration of CO₂ was near 34% in O₂/N₂ combustion. This high concentration of CO₂ in the flue gas of O₂/CO₂ combustion is beneficial for the control, separation, and recovery of CO₂ during the combustion of fossil fuel. Upon increasing the O₂ concentration in the feed gas of O₂/RFG coal combustion, the formation of CO was decreased and the combustion efficiency was increased. Introducing the RFG into the second combustion chamber had higher combustion efficiency than that into the first combustion chamber. The mass flow rates of CO₂, CO, and O₂ were all increased with the ratios of RFG except for a few cases. With suitable gas compositions O₂/CO₂ and sufficient O₂ concentration in the feed gas, high combustion efficiency and recovery efficiency of air pollutants could be achieved.