Study On Characteristics Of NO_x Formation In Coke Oven Coking Process

Nitrogen oxides of most existing coking enterprises seriously exceeded the standard,and nitrogen oxide emissions caused great harm to people’s lives has attracted great attention.With the country’s emphasis on environmental protection,reduce the coke oven nitrogen oxide has become an urgent task to be solved.In this paper,the research object is a couple of heating flues of JN60 coke oven,a thermal process model of the heating flue of coke oven burning with blast furnace gas and coke oven gas is established respectively.The combustion characteristics and NO generation characteristics of the heating flue were investigated by using CFD numerical simulation method.By analyzing the formation mechanism and potential influencing factors of nitrogen oxides in existing heating systems and production processes,this paper simulates and quantitatively analyzes according to different excess air coefficient,heat flux density of heat transfer surface and exhaust gas circulation rate respectively.The simulation results show that the excess air coefficient has different effects on the NO concentration of the heating flue outlet of coke oven burning with blast furnace gas and coke oven gas.When the gas is blast furnace gas,the NO concentration of the heating flue outlet is increased first and then decreased with the increase of the excess air coefficient and the influence degree is different under different heat flux.When the gas is coke oven gas,the NO concentration of the heating flue outlet has shown a downward trend in NO emissions with the increase of the excess air coefficient.The NO concentration of the heating flue outlet of coke oven burning with blast furnace gas was significantly reduced.Increasing the external circulation of the flue gas can effectively reduce the NO concentration in the flue gas from the flue.When the heating gas is blast furnace gas,the NO concentration can be reduced by about 60% when the outer circulation rate is about 12% in the absence of internal circulation hole.,which can reach the national emission standard(350mg/m3).Under the action of internal and external double cycle,the NO concentration in the heating flue was significantly reduced and the flame was obviously elongated with the increase of external circulation rate.When the heating gas is blast furnace gas,the NO concentration can reach the national emission standards(350mg/m3)with a decline of about 42.43% when the external circulation rate of about 5%.When the heating gas is coke oven gas,the NO concentration can reach the national emission standards(500mg/m3)with a decline of about 69.72%when the external circulation rate of about 11%.The results of this study on the influencing factors of NO generation characteristics in coke oven fires are instructive to reduce NO emission and combustion optimization parameters in the production process.