Design And Emission Characteristics Of Low NO_x Burner For Single Well Furnace

The single well heating furnace is a kind of water jacket furnace with rated power of45 k W,most of which are combusted by diffusion;in addition,the oil well associated gas casing gas is used,55%-85%of which is CH₄.In addition,it contains C₂-C₆ alkanes and other components,which leads to more than 40%of wellhead heating furnaces’NO_x emission exceeding the standard,and the heating furnace efficiency is also low.In order to reduce the content of NO_x in flue gas and make it below 50 mg/m³ of national new regulation in 2019.Based on the analysis of the existing low NO_x combustion technology,according to the operation characteristics of the single well furnace,the low NO_x burner is developed and designed by using the numerical simulation method,and the field application test is carried out.The main contents and conclusions of this paper are as follows.1.The simulation results of full premixed combustion and diffusion combustion show that the excess air coefficient increases from 1.4 to 2.8,and the maximum flue gas temperature in the diffusion combustion chamber first increases and then decreases,but the overall change is small,only 1448 K-1559 K;The maximum flue gas temperature of full premixed combustion decreases from 1648 K-1037 K,and the change is obvious.There is a dividing point between them when the excess air coefficient is between 1.4 and 1.6.It is found that the NO_x emission reduction effect of full premixed combustion is better,and the thermal efficiency is about 9%-11%higher than that of diffusion combustion.It is an effective NO_x emission reduction technology suitable for wellhead heating furnace.2.The essence of flame cutting technology is distributed combustion technology.Based on this,four sets of burner hole layout schemes are designed,which are 0.8 mm、1.2mm、2.0 mm and 2.6 mm respectively.The results show that the NO_x emission increases with the increase of the diameter of the fire hole.However,when the diameter of the fire hole is 1.5,only when the diameter of the fire hole is 2.6 mm,the NO_x emission is significantly higher.Under the interaction of excess air coefficient（1.1-1.8）and fire hole diameter,when the fire hole diameter is 2.0 mm,the thermal efficiency reaches the highest.Therefore,the diameter of the fire hole is 2.0 mm.3.It is found that the better the premixed effect of gas and air is,the lower the NO_x emission is.Therefore,a good premixer is the premise to realize full premixed combustion.Therefore,the structure of the premixer is optimized and simulated,and the mixing unevenness s is analyzed as the evaluation index.The results show that the size of the mixing chamber has little effect on S,and the mixing effect is poor.Based on the structure of the premixer,the orthogonal experiment is established.Through variance analysis and range analysis,the optimal structural parameters are as follows:the number of fan blades is14,the diameter of gas inlet is 8.0 mm,the angle of fan blade is 45°and the excess air coefficient is 1.6.4.Five new low NO_x burners are used and five field test systems were built,Finally,the flue gas was collected from the chimney for detection,and the measured NO_x emission concentration was 21 mg/m³、7 mg/m³、19 mg/m³、13 mg m³、19 mg/m³,which was far less than the initial NO_x emission data of the heating furnace:348 mg/m³、119 mg/m³、131mg/m³、164 mg/m³、131 mg/m³.At the same time,the thermal efficiency of the heating furnace was generally increased by 7%-13%,and the operation was good.This shows that the low nitrogen burner can fully meet the requirements of the new national regulations and meet the installation standards.In the heating furnace,the main reason of NO_x exceeding the standard is that the combustion temperature is high.The original combustion device adopts diffusion combustion and centralized combustion to improve the temperature in the furnace.Full premixed combustion and flame cutting combustion can reduce the combustion temperature from different aspects.At the same time,improving the mixing degree of casing gas and gas can also effectively reduce the NO_x emission concentration and improve the thermal efficiency.Through the field experiment,it is found that the low NO_x burner developed in this paper can effectively improve the shortcomings of the original burner,expand the international research on the low NO_x burner of low power heating furnace,and has a certain promotion value in business.