GB1468364A - Burner assembly and method for controlling its operation to provide reduced emission of air pollutant - Google Patents

Abstract

1468364 Forced-draft burners TRW Inc 12 May 1974 [26 July 1973] 52350/73 Heading F4T A forced draft burner comprises means for supplying an oxidizer under pressure, an oxidizer supply tube 27 connected to said supply means and communicating with a combustion zone 16, e.g. defined by the wall 11 of a boiler, a fuel distribution tube 28 connected to means for supplying fuel under pressure and having an end part 30 projecting into the zone 16 and a plurality of radially oriented fuel outlet orifices 32 equispaced around the periphery of said part 30, and a deflector disc 31 projecting from said part 30 into the path of the oxidizer discharged from the annular passage 33 between tubes 27, 28, the total orifice area being determined in accordance with an equation as defined in claim 1. The Specification discloses relationships whereby, for a given heat output, the diameter of disc 31, the size and number of orifices 32, the fuel/oxidizer momentum ratio and the depth of penetration of the fuel jets from orifices 32 into the annular oxidizer stream may be selected to minimize the production of nitrogen oxides. With the selected parameters, a generally conical flame pattern 45, which is hollow and thin, results giving rise to heat transfer by convection and radiation to the walls 11 to control the temperature profile in order to minimize NO x production by inducing rapid heat dissipation after combustion. NO x production is also minimized by controlling the reactants' residence time in the combustion zone and by achieving good oxidizer/fuel mixing. The mixing is enhanced by oxidizing gas 42 deflected by disc 31. The temperature may also be controlled by the introduction of cooling gas to the interior of the flame 45 via tube 44 and deflector 46. The oxidizer may be air and the fuel may be gas, e.g. natural gas, or liquid fuel, e.g. oil. Liquid fuel is introduced tangentially into tube 28 at 36 and passes through a mixing element 38 having helical surfaces 39 wherein the fuel mixes with atomizing gas, e.g. air, steam, nitrogen or recirculated combustion products, introduced at 37, the atomizing gas subjecting the liquid to high shear forces at orifices 32. In a modification, the outlet end of tube 27 expands downstreamwards and the end part 30 of tube 28 also expands downstreamwards, the tube 28 and disc 31 being axially movable to adjust the cross-sectional of the annular oxidizer outlet, Fig. 13 (not shown).