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Show TECHNICAL AND ECONOMIC EVALUATION OF OXYGEN ENRICHED COMBUSTION SYSTEMS FOR INDUSTRIAL FURNACE APPLICATIONS H. Kobayashi, J. G. Boyle Union Carbide Corp. J. G. Keller EG&G, Inc. Tarrytown, New York, USA Idaho Falls, Idaho, USA ABSTRACT Parametric analytical studies were conducted to evaluate the economics and technical requirements of oxygen enriched combustion systems (OEC) and preheated oxygen enriched combustion systems (POEC) for industrial heating applications. The potential for fuel savings and productivity improvements with OECjPOEC systems was analyzed for a broad range of furnace conditions including those for steel reheating, glass melting, and aluminum remelting. The optimum combinations of oxygen enrichment and preheating were investigated considering process constraints and capital and operating costs of POEC systems. The most cost effective methods of supplying oxygen enriched air were evaluated comparing the economics of membrane, PSA and cryogenic systems. The overall process economics of OECjPOEC systems were compared with those of conventional heat recovery systems. RECENT ADVANCEMENTS in oxygen combustion technologies (Ref. 1,2) have made it possible to use up to 100% oxygen for process heating in industrial furnaces which are commonly fired with conventional air burners. The growing interests in oxygen enriched combustion stem not only from the successful development of oxygen or oxygen enriched combustion technologies for energy savings and productivity improvements (Ref. 3-5) but also from new advancements in air separation technologies. Since the economics of oxygen enriched combustion are strongly dependent on the costs of both oxygen and fuel, the availability of low cost oxygen is critical to the process economics. Applications of membranes to produce oxygen enriched air are under active development (Ref. 6) and considerable optimism exists for cost effective production of oxygen enriched air in the future. While the benefits of oxygen enriched combustion have been widely reported (Ref. 3-5, 7, 8), limited and sometimes conflicting infor- 153 J.B.Patton U.S. Dept. of Energy Idaho Falls, Idaho, USA R. C. Jain u.s. Dept. of Energy Washington, D.C., USA mation exists on the basic mechanisms of energy savings and productivity improvements by oxygen enrichment and the optimum levels of oxygen enrichment. In addition interest has been raised on the potential benefits of combining oxygen enrichment and preheating as a means to achieve extremely high energy efficiencies. This paper reports the results of parametric analytical studies to evaluate the extent of energy savings and productivity improvements with oxygen enriched combustion and discusses the key technical and economic factors influencing the use of oxygen or oxygen enriched air for industrial furnace applications. ENERGY SAVINGS WITH OXYGEN ENRICHMENT Oxygen enrichment eliminates a portion of nitrogen contained in combustion air and hence reduces the sensible heat loss directly. In Figure 1, fuel required to provide 1 MMBTU of available heat to a furnace is plotted as a function of flue gas temperature for ambient air, preheated air and three different levels of oxygen enrichment. As the flue gas temperature increases, the fuel requirement to provide a given amount of energy above that temperature level increases and the difference between air and oxygen as oxidants becomes greater. For example, as the temperature level increases from 2000 to 30000 F, the fuel requirement to obtain 1 MMBTU of available energy increases from 2 . 4 to 8.0 MMBTU for air, and from 1.34 to 1.55 for 100% oxygen. As a result, the fuel savings using oxygen increases substantially as the operating temperature of the furnace increases. The figure also shows that the fuel requirements with 25% and 35% oxygen enriched air are lower than those with preheated combustion air of o 0 500 F and 1000 F respectively at higher temper-atures. Thus, even relatively low levels of oxygen enrichment are effective in substantially improving the energy efficiency. The amount of energy savings with oxygen enrichment also depends on the concentration of |