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Show An Investilation of Ultra-Low NOx Natural Gas Burners Abstract by V. Dupont, M. Pourkashanian and A. Williams Department of Fuel and Energy, Leeds University, Leeds, LS2 9JT, U. K. There is an increasing demand for ultra-low NOx burners for all types of heating applications. Gas-fired process heaters have been developed and used for many years for the direct drying of foodstuffs and these generally involve fuel-lean premixed flames burning in a stream of ducted air. These burners have many other app 1 i cat ions and the characteri st i cs of one such burner is studied here operating with fuel-air ratio ((,6) = 0.77 together with two other flames, one operating at (,6 = 0.885 and the other stoichiometric. Fl ames in these 1 ean burners produce NOx almost exc 1 us i ve 1 y by the prompt-NOx route and the correct prediction of NOx in these complex low temperature fl ames by CFD methods requi res the use of pred i ct i ve methods which are accurate at low temperatures. Details are given of one way of achieving this which gives results in accordance with experimental observations. 1. Introduction Many gas-fired process heaters used for drying food materials consist of arrays of stoichiometric or fuel-lean premixed flames burning in a stream of ducted air and being further diluted with air to give a gas stream with a temperature of 75°C. Such burners have to produce extremely low levels of NOx to prevent the formation of nitrosamines in the foodstuffs. Experiences obtained in the development of these burners are transferable to other spheres of low NOx burner technology. -The flame structure involved in these burners is complex and difficult to model because they combine a number of rapid combustion regions for the flames coupled with the mixing and dilution of the combustion products in the ducted air stream. In such flames the formation of NO occurs only partially via the thermal-NO rate but the dominant route x is by means of the formation of prompt-NO. |