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Show DILUTE OXYGEN COMBUSTION A NEW APPROACH FOR LOW NOz COMBUSTION HISASHI KOBAYASHI ZHIYOU DU Praxair, Inc., Linde Division Tarrytown, New York 10591 ~ 1992 Praxair Technology, Inc. ABSTRACf An ultra low NOz combustion method based on the concept of reacting fuel with a very dilute oxygen stream has been developed recently and commercialized as Praxair Type L Burner. NOz emissions of 0.01 to 0.02 Ib/lO' Btu were achieved in a test furnace operated at 23000F with various furnace nitrogen concentrations ranging from 34 to 68%. INTRODUCTION Many low NOz burners have been developed over the last two decades to meet the increasingly tightening emissions standards. It has been well established that the most effective design strategy for reduction of thermal NOz is to reduce the peak flame temperature. External and in-furnace flue gas recirculation have been adopted in many burner designs for NOz reduction. At Praxair Inc. (formerly Union Carbide Industrial Gases Inc.) a low NOz oxy-fuel burner using in-furnace recirculation of flue gas was developed in the late 1970's (Ref 1,2) and successfully commercialized for high temperature industrial furnace applications under the trade name of Linde "A" Burner. The burner demonstrated that the peak flame temperature of oxy-fuel flames could be reduced even below that of conventional air-fuel burners. NOz emissions as low as 0.001 Ib as N02 per 1(f Btu (equivalent to 0.72 ppm for CH .. -air combustion at 2% excess O2 in flue gas on a dry basis) was achieved in a test furnace with minimum air leakage. The source of nitrogen in the furnace was primarily molecular nitrogen contained in natural gas. Since it is not practical to totally eliminate nitrogen in most industrial furnaces and NOz formation is highly dependent on the flame temperature, control of the flame temperature is especially important for oxy-fuel combustion. Extensive studies have been conducted on the emissions of NOz from various industrial burners under oxygen enriched combustion conditions and published elsewhere (Ref 3,4). 1 |