Evaluation of the Improvement of FGR Circulation Gas Deflection for the Stabilization of NOx Generation in Mixed Gas Boilers

The steel industry makes the most of it's incidental COG (Coke oven gas) and BFG (Blast furnace gas) as fuel and is striving to achieve it's greenhouse gas reduction goals in line with the era of national carbon neutrality. NOx generated during boiler combustion is reduced by using the FGR method that circulates the combustion gas. However, there is often a problem that the combustion air and the combustion gas are not well mixed. In this paper, we tried to achieve efficiency improvement and stable NOx reduction by studying the cause of the FGR efficiency reduction and improving the problems. When mixing FGR combustion gas, it was not evenly sprayed into the burner due to deflection. As a result, the temperature of some flames increased and thermal NOx increased. In order to improve the mixing of combustion gas and combustion air, the gas pressure deviation was increased by 100∼200 mmAq or more and converted to an injection type, and a porous plate was installed to disperse the combustion gas to improve mixing efficiency. The boiler flame formed a stable shape, and the NOx data also showed a reduction effect of 7 ppm and uniform data.