Effect of combustion air preheating on NOx emissions from gas burners in high-temperature industrial applications

NOx emissions from different commercial gas burners for metal heat treatment applications were measured for a research project of the Gaswärme‐Institut. The burners, rated at up to 50 kW, were installed for the tests in a laboratory combustion chamber operated at temperatures of up to 1400°C. The air for combustion was preheated to maximum temperature of 600°C. Following the tests, the potentials of different NOx control techniques were investigated. Methods explored included staged combustion air injection, staged fuel injection and fuel gas injection into the flue for NOx reduction. The results showed that it is feasible to reduce the NOx content of flue gases by as much as 90%.