Circulating fluidized bed incineration treatment of sintering flue gas

Sintering flue gas is the waste gas produced in the sintering process of steel production, containing NOx, SO2, dioxins, volatile organic compounds, and other pollutants. The sintering flue gas can replace the air of the coal-burning circulating fluidized bed (CFB) boiler for incineration treatment, which can effectively reuse CO and residual oxygen in the waste gas, and remove SOx, NOx, and other pollutants in the sintering flue gas together with pollutants from coal combustion by the high-temperature atmosphere and desulfurization and denitrification facilities in the CFB boiler. It is expected to become an efficient integrated treatment technology for sintering flue gas. However, the research on removing dioxins and volatile organic compounds from sintering flue gas by coal-fired circulating fluidized bed boilers is still limited. The coal combustion process of sintering flue gas as an accelerant was studied through chemical reaction kinetics simulation. It is found that hydrogen radicals and other free radicals produced in the combustion process are the main mechanisms of dioxin removal, and the increase in combustion reaction temperature can significantly promote the removal of dioxins and volatile organic compounds. The decrease of residual oxygen in burned flue gas can also encourage the removal of dioxins. The operation of a coal-fired CFB boiler with sintering flue gas as the accelerant is simulated by calculating particle fluid dynamics. It is found that the fluidized state of the combustion process is good, and the low-concentration CO in the sintering flue gas is burned out with the cyclone separator outlet mass concentration of CO at around 100 mg/m3. The combustion temperature also satisfies the temperature requirement for removing pollutants. The feasibility of using sintering flue gas as the accelerant in the coal-fired CFB boiler is verified. The engineering verification of the CFB incineration method for sintering flue gas is conducted in a steel plant in Tangshan. The test on the flue gas at the outlet of the low-temperature economizer shows that the dioxin removal rate exceeds 99.5%, as low as 0.005 7 ng TEQ/m3 and the mass concentration of CO is as low as 108 mg/m3. The concentrations of NOx and SO2 in the flue gas are as low as 38 and 24 mg/m3, meeting the ultra-low emission requirements. The effectiveness of the integrated CFB sintering flue gas incineration treatment is proven.