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Show COMBUSTION CHARACTERISTICS OF FUELS WITH PREHEATED OXYGEN ENRICHED AIR Pablo S. Guerrero, Wilfred J. Rebello, Moonis R. Ally PAR Enterprises, Inc. Fairfax, Virginia, USA ABSTRACT Enriching air with oxygen in furnace combustion systems can significantly increase the thermal efficiency of the system and contribute to a savings in fuel and an increase in productivity. If economic feasibility is proven for a given application, the only other potential barrier to the use of oxygen enrichment in industrial combustion processes could be the increase in NO formation due to the higher flame temperatures~ The objectives of this work were to determine the maximum flame temperatures resulting from the combustion of various solid, liquid and gaseous fuels with preheated oxygen enriched air, to determine the maximum (equilibrium) levels of pollutant (NO ) concentrations and to predict actual levels of NO that could be expected in typical industrial furnaces. The computer program considered thirteen dissociating species, preheat temperatures up to 20000F and oxygen enrichment levels varying from 21% to 50% oxygen. The results indicate that for natural gas above flame temperature of 5165°F, the equilibrium NO values tend to decrease with high levels of 3xygen and high preheat temperatures because other dissociating reactions predominate at these high temperatures. A methodology was developed, using kinetics, to predict the actual NO expected in a typical furnace. The predict~d values of NO were compared with measured values for an experimental furnace and found to be in general agreement. Though there are no New Source Performance Standards for industrial furnaces, the analysis indicates that for combustion of nanrral gas with preheated oxygen enriched air, the NO formed would be conSiderably more than the NS~S for an industrial steam generator of 0.2 lbs N0 2 /million BTU. 187 Ramesh Jain U.s. Department of Energy Washington D.C., USA THE TOTAL ENERGY consumption in the U.S. in 1977 was about 76 Quads. Of this amount, about 28 Quads were consumed by the industrial sector in the form of coal, petroleum, natural gas and electricity. This energy was used in the form of thermal energy for raising the temperature of materials and for generating steam, in the form of feedstocks for certain industrial processes. The manufacturing induptries alone (SIC-20-39) consumed 10.7 Quads of purchased fuels for raising steam, for process heat and for producing shaft and electrical power. There is a tremendous scope, therefore, for applying existing technology to the efficient management of this large amount of fuel so as to yield large fuel savings. Most industrial combustion processes are highly inefficient with process efficiencies ranging from 10-20% at process temperatures of about 2400°F to about 40 to 60% at process temperatures of about 500°F. Considerable fuel savings can be achieved by waste heat recovery using recuperators, regenerators, low temperature bottoming cycles, heat pumps, etc. Significant fuel savings can also be achieved by improving the efficiency of the combustion process where the internal energy in the fuel is converted to thermal energy. There is a need for improvements in burner design and furnace operation and controls. Enriching air with oxygen offers the possibility of significantly increasing the thermal efficiency of the heat system. The higher the flue gas temperatures the more pronounced is the effect of oxygen enrichment. As an example, with the stoichiometric combustion of natural gas with 21% 02 and 40% 02 air at a flue gas tenperanrre of 2000°F the % available b2.at increases fran 45% to 65% while at a flue gas tenperature of 3CXX)°F, the :increase is fran 20% to 50% . Energy savings using oxygen enriched air |
