On emerging furnace design methodology that provides substantial energy savings and drastic reductions in CO2, CO and NOx emissions

Recent developments in heat recovery systems allow for preheating of combus tion air up to temperatures of 1300 degrees C and, thus, fuel savings up to 60% are achievable. In conventional burner/furnace designs, the higher the combustion air temperature the higher the NOx emissions. However, the most recent developments allow for low NOx combustion using high temperature co mbustion air. The objective of this paper is to establish conditions under which industrial furnaces should be operated in order to maximize the effic iency and minimize the pollutant emissions including carbon dioxide. To thi s end, semi-industrial scale experiments have been carried out using natura l gas and vitiated air at 1300 degrees C. A Nippon Furnace Kogyo burner tha t features a central air jet and two fuel gas injectors was used. Comprehen sive in-furnace measurements of velocities, temperature, gas composition (O -2, CO2, CO, H-2, NO, CH4) and radiation have been carried out. The furnace was operated under conditions resembling a well-stirred reactor; the tempe rature and chemistry fields were uniform all over the furnace. Almost the w hole furnace volume was filled with combustion products containing 2-3% oxy gen at temperatures in the range 1350-1450 degrees C, despite the high temp erature (1300 degrees C) of the vitiated air. The natural gas jets entraine d many of the combustion products before they mixed with combustion air. Th is mode of combustion resulted in high and uniform heat fluxes and low NOx and CO emissions. It was concluded that industrial furnaces of tomorrow are likely to be designed as well-stirred reactors equipped with high efficien cy heat regenerators. Conventional burners will be either replaced with ind ividual fuel and air injectors or substantially redesigned to facilitate un iformity of combustion conditions within the furnace.