Bench-Scale Testing on 02/C02 Combustion for C02 Recovery

Evaluating the characteristics of burnout efficiency, NOx conversion and flame behavior on pulverized coal firing with 02/flue gas recycling combustion for CO2 recovery, a bench-scale testing was conducted using a 1.2MWt tunnel type test furnace. From the viewpoint of the plant safety on full scale 02 combustion with recycled flue gas, pulverized coal was transported by flue gas as a primary stream and 02 conc. in a secondary stream was also limited to be less than 35%. Consequently, these limitations caused poor flame stability and char burnout due to lowering flame temperature by flue gas recycling. Enhancing the char burnout performance, therefore, an attempt was made to supply a part of pure 02 as a tertiary stream to the burner throat through an 02 injection nozzle. When 02 conc. in the secondary stream kept constantly to above limited value, the increase of the tertiary stream apparently improved the flame stability and the char burnout efficiency, as was expected. NOx emissions was not affected significantly by the presence of the tertiary stream, and it was found that lower NOx conversion was obtainable on 02/C02 combustion.