THE EFFECTS OF FUEL AIR MIXING ON NOX REDUCTION AND HEAT-TRANSFER IN HIGH-TEMPERATURE GAS-FIRED GLASS-MELTING FURNACES/

This paper describes the results of a series of experiments executed a t the International Flame Research Foundation (IFRF) for a consortium of gas companies. The main objective of the experiments was to investi gate novel NOx-reduction methods and their impact on heat-transfer in glass-melting furnaces fired by natural gas. A section of a full-scale glass-melting furnace was scaled down and simulated at a semi-industr ial scale, with representative thermal boundary conditions. The experi ments concentrated on optimising the mixing process between the fuel j et and the combustion air. A wide variety of firing modes were employe d to investigate the effect of mixing on NOx and thermal efficiency. R esults suggested a number of practical NOx-reduction techniques applic able to high-temperature furnaces. Over the whole range of firing mode s investigated, NOx levels varied in the range of 200-2500 ppm (0% O-2 ) for identical excess-air levels and air-preheat temperatures. The fu el-efficiency levels varied between 49 and 55% of the fuel input, depe ndent on the firing mode. It has been demonstrated that by optimising the mixing of fuel and air, significant reduction of NOx is achievable while maintaining thermal efficiency and heat-transfer characteristic s within acceptable limits.