Numerical Investigation On Dual Fuel Diffusion Burners

With the rapid economic development of our country,there were serious environmental problems.Compared with solid fuels such as coal,gas fuels produce less pollutants during the combustion process,they are used more and more widely.Coke oven gas and purge gas as by-products of industrial production,have high economic value and environmental protection significance to be made full use of.With the main goal of reducing NOx emissions,this paper uses numerical simulation to study the newly designed coke oven gas and purge gas dual fuel diffusion burner of a chemical plant in Henan.First,a natural gas and hydrogen dual fuel diffusion burner was studied with the method of numerical simulation.Because this burner has been put into production,we can compare the simulation result with actual process to evaluate the feasibility of research by the method of numerical simulation.Then we study the newly designed prototype of coke oven gas and purge gas dual fuel burner with the same numerical simulation method to get its combustion and NOx emission characteristics.Finally,adjusting structural and nonstructural parameters based on the prototype burner to get better combustor structure and operating condition with the main goal of reducing NOx emission.The results show that:(1)The use of non-injection holes on the top of the fuel nozzle can reduce the maximum temperature and high temperature area in the furnace compared with the original round fuel injection holes.(2)When the fuel nozzle oblique rotation angle is at a 0 degree angle with the tangent direction,it can reduce NOx emissions by 32.46% compared to the original 20 degree angle.(3)Lengthen half of the fuel nozzle,within the range of 50 mm ～ 200 mm,with the length increase,the nitrogen oxide emissions will decrease,the 200 mm extension tube has a 47.78% lower NOx emission than the 50 mm extension tube.Because the fuel and combustion air are better mixed,the nitrogen oxide emission of prototype is lower than the extension tube,the NOx emission of the nonextension tube is 69.08% lower than that of the 50 mm extension tube.(4)Affected by the position of the fuel and air inlets,if we use both coke oven gas and purge gas as fuels,we can get lower NOx emissions when the circulating flue gas enters the furnace from a separate inlet.If we only use coke oven gas as fuel,we can get lower NOx emissions when the circulating flue gas is mixed with air and enters the furnace from the air inlet.(5)Considering NOx emissions,fuel burnout and heat loss,it is more suitable to set excess air coefficient to 1.1,circulating flue gas ratio to 25%,and the ratio of central wind,primary air,and secondary air to 0.05: 0.35: 0.6.The simulation research results can guide the design and operation of the diffusion burner.