Design And Combustion Characteristics Modelling Of Mild Burner For Reheating Furnace Mixed Gas

It is of great significance to develop new efficient furnace combustion technology forenergy conservation and emissions reduction in steel enterprise. MILD combustion is a newtype of combustion mode in international combustion field nearly in more than10years.Combining with the Oxy-fuel combustion technology, it can realize to improve temperatureuniformity, increase radiation heat transfer, reduce the oxidation burning loss, and reducepollutants emissions (CO2and NOX) and so on. In this paper, we chose a steel mill furnaceof mixed gas for the study, designed the air-MILD burner and the oxygen-enriched MILDburner through numerical simulation，detailedly studied the burner combustion organization,composition and temperature characteristics and NOXemissions, and comparatively analyzedthe thermal area of heating furnace and temperature uniformity.This paper discussed the combustion characteristics of conventional burner andair-MILD burner, the results showed that the MILD burner can better control thepre-chamber combustion so that the combustion occurs in the furnace as much as possible,the combustion reaction zone increases and extends rearward, the furnace temperatureuniformity becomes better, and the peak temperature reduces a lot. Studying the air-MILDburner arrangement parameters, we found that the primary air and second air ipsilateralarrangement can more easily stir the furnace flue gas and form dispersion flame than theprimary air and second air symmetric arrangement，which obtained a better thermal area andtemperature uniformity.Based on research results of air-MILD burner, this paper studied the combustioncharacteristics of oxygen-enriched conventional burner and oxygen-enriched MILD burner,comparatively analyzed the thermal area and temperature uniformity. Studies have shown thatMILD burner can avoid or reduce the high local temperature defect of Oxy-fuel combustion,and obtain a better thermal area and temperature uniformity. We also found that it was difficult for the conventional burners through changing the oxidant import parameters (suchas import diameter, incline angle, import velocity, etc) to reduce the peak temperature andtemperature uniformity in the oxygen-rich atmosphere. Compared to the emissions of NOXin conventional burners and MILD burner, we found that MILD burner can greatly reducethe emission of NOX, less than half of the conventional burner. Comparing the differentcondition of MILD combustion, it is founded that appropriately increase antioxidant nozzledistance can reduce furnace temperature peak and obtain good thermal area.