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Show AFRC90 Paper 22 LOW NOx COMBUSTION WITH NATURAL GAS Glenn C. Neff, Sr., M. L. Joshi, Marvin E. Tester Combustion Tec, Inc. Orlando, Florida and Sherry K. Panahi Southern California Gas Company Los Angeles, California ABSTRACT An improved method of gas firing on a glass furnace and reduced NOx emissions is outlined. This method involves the use of a cracker for NOx reduction. The cracker method of gas firing takes about 25% of the furnace natural gas consumption through a separate cracker to produce soot particles. This is then re-blended with the balance of 75% of gas, producing a "soot-rich" gas mixture. The combustion of soot-rich gas produces flame with increased luminosity and lower adiabatic flame temperature characteristics which is expected to reduce NOx emissions by 35% or more. Past, current and future plans involving the cracker program are discussed. Past experiments on a pilot unit indicate a very low soot yield (- 2%) due to undesirable reforming reactions. Current and future cracker design includes a new modulative gas cracker concept that incorporates several new features which enhance thermal cracking with very little reforming . INTRODUCTION Public awareness over environmental issues such as acid rain, global warming, and depletion of the earth's .ozone layer has led to environmental regulations that restrict emissions from various combustion equipment. The thermal NOx is essentially formed by thermal oxidation of nitrogen in combustion air. It is shown that the thermal NOx depends upon the temperature distribution along the flame length and it increases with peak flame temperatures. Energy is transferred from glass tank flames mainly by radiation processes, whose magnitude is influenced by the degree of luminosity (or emissivity) of the flame. Luminous flames have traditionally been favored for glass melting, since they are usually accompanied by a uniform release of heat in the furnace chamber. The radiation emitted by a flame is proportional to the product EfTf4, where Ef is the emissivity of the flame, and Tf is its temperature. Thus, a highly luminous flame (higher emissivity) can allow a given furnace to operate at a lower peak flame temperature (Tf) and subsequently lowering thermal NOx ' -1- |