Study on Energy Efficiency of 35MWth Oxygen-fuel Boiler with Recirculated Flue Gas

A oxygen-fuel boiler working at O2/CO2 atmosphere can enrich the carbon dioxide for exhaust flue gas with recycled flue gas and injected oxygen as combustion supporting gas instead of air, which makes the calculation methods of flue gas distribution, exhaust gas loss and boiler efficiency different. A flue gas distribution analysis model considering air leakage is built for the actual operation of a O2/CO2 combustion boiler with designed thermal load of 35MWth. Based on the flue gas distribution model, the method calculating the exhaust flue gas loss is proposed which can be used to in boiler efficiency test. And then the boiler efficiencies of that boiler working at O2/CO2 atmosphere and air atmosphere are test and calculated. The calculation results show that the method of calculating the exhaust flue gas heat loss can be used correctly to analyze the oxygen-fuel combustion boiler test. The exhaust gas heat loss of 35MWth boiler under oxygen-fuel combustion mode is less than that under air combustion mode. But the solid incomplete combustion loss under oxygen-fuel combustion mode is greater than that under air combustion mode.