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Show Prediction of NO x emissions from the high temperature combustion of natural-gas ~ Dearden, L.M, Hedley, J.T., Pourkashanian, M, Williams, A. and *Yap, L. T. Department of Fuel and Energy, The University of Leeds, Leeds, LS2 9JT, UK. * BOC Group Technical Center, Murray Hill, NJ., 07974, USA. Abstract The predictions of the levels of NOx produced during high temperature combustion resulting from either air preheat or by the use of oxygen, can be undertaken with reasonable accuracy as long as certain precautions are taken. Particular attention is paid towards three areas. Firstly, the fact that NOx is particularly sensitive to temperature and its variation. The ways in which this is computed for oxygen/natural-gas flames and for a steel regenerative furnace are described including the use of equilibrium consideration. Secondly, the importance of NOx chemistry and the sensitivity of the pdf used to describe the thermal processes are outlined. Thirdly, the role ofN2 is discussed. In preheated air/fuel flames the N2 levels are high whilst in oxy/fuel combustion only trace sources are present, via the 02, fuel or leaks. The consequences of this are outlined. Two examples will be given in detail: a steel industry regenerative furnace and an oxy/natural gas ladle preheat furnace. Introduction High temperature combustion systems are used in a multitude of industrial processes, in particular melting, reheating and heat-treatment of metals. Although enhanced heat transfer processes prove advantageous, flue gas losses may result in an unsatisfactory overall thermal efficiency. By employing a waste heat recovery set-up, such as a regenerator to preheat the incoming combustion air, an improvement in the overall efficiency can be achieved. Although recent regenerative burner designs have indicated a significant increase in NOx formation within the combustion chamber due to elevated temperatures, staged combustion can be |