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Show extremely short furnaces. The result was an array of QLN burner designs that could be applied for a wide variety of packaged and field erected boilers. By the end of 1995 there were over 100 burners operating in the United States and some in Europe. QLN BURNER. PRINCIPLE OF OPERATION There are three main mechanisms of NOx formation that have been extenSively described in the literature: prompt NOx , thermal NOx and NOx Originated from nitrogen content species in the fuel (fuel bound nitrogen). Formation of prompt NOx can be greatly reduced if the fuel burns under fuel lean conditions. Formation of thermal NOx is an exponential function of peak flame temperature and can be reduced, if the combustion region contains high amount of combustion products with temperatures much lower than the adiabatic flame, or again under fuel lean conditions when excess of air serves as a diluent. Formation of NOx from nitrogen in the fuel is typically a concern only when firing oil, as gaseous fuels seldom contain non molecular nitrogen component~ Fuel rich environment is beneficial for the reduction of this source of NOx. QLN burners effectively reduce formation of NOx from all there sources. The basic burner design is shown on Fig.1 . The main burner parts are primary, secondary and core gas headers with gas spuds that provide distribution of gaseous fuel. The burner body with the attached air distribution plate shapes air flow into a star pattern. The primary gas is injected into the air flow inside the burner through the radial spuds, so most of the mixing of gas and air is taking place upstream of the distribution plate. The axial part of the burner is reserved for the oil gun. The core gas header is typically positioned around the oil gun guide pipe. The burner is equipped with a short straight throat. The secondary gas spuds protrude through the ports in the throat. When firing oil, these ports are used for bringing a portion of air into the combustion area. A simple mechanism allows for closing or opening of all the ports at once. The same ports are sometimes used as the injection points for the flue gas recirculation, if brought selectively to the burner. Figure 1. Basic QLN Burner 2 |
