Numerical Simulation Of NO_x Formation In A Combustion Chamber Of A Coke Oven By Computation Fluid Dynamics

In recent years,China’s coking industry has developed rapidly,but it has also brought about serious environmental pollution.The pollution caused by NOx in coke ovens is particularly significant.In this paper,the single pair heating flue of a 7m coke oven in a steel plant is taken as the research object,and numerical simulation of the combustion in the heating flue is carried out based on CFD technology.The NO concentration field of the heating flue with the recirculation windows is studied by a comparison method.The effects of the distance between the fuel nozzle and air nozzle,the volume fraction of oxygen in air,and the size and location of the recirculation windows in the heating flue on the NOx formation characteristics of the heating flue are discussed.The main conclusions are as follows:Ⅰ.In the heating flue with the recirculation windows,a part of the exhaust gas in the downward heating flue enters the upward heating flue through the recirculation windows.The exhaust gas dilutes the oxygen in flame.The burning flame is elongated,the burning temperature is lowered,and NO emission is decreased.The NO concentration at the outlet of the heating flue is reduced by 72%.Ⅱ.In the heating flue the increase in the distance between the fuel nozzle and the air nozzle reduces the contact area between the fuel and air and delays the time to reach the contact surface,resulting in lowered combustion temperatures and reduced NOx production.The distance between the fuel nozzle and the air nozzle is increased from 160mm to 280mm,and the NO concentration at the outlet of the heating flue decreases to 224 ppm,with a reduction of about 43%.Ⅲ.Oxygen volume fraction in air has a significant impact on the generation of NO in the heating flue.When the oxygen volume fraction in air is less than 12%,the NO concentration at the outlet of the heating flue is almost zero.When the oxygen volume fraction in air increases from 12 to 24%,the NO concentration at the outlet of heating flue is increased by 514 ppm,showing an exponential growth trend.IV.The heating flue with the recirculation windows can reduce the generation of NO and the size of the recirculation windows at the same time also has a significant effect on the generation of NO in the heating flue.When the size of the two recirculation windows in the heating flue is continuously increased,and the NO concentration at the outlet of the heating flue is significantly reduced.When the two recirculation windows in the heating flue is merged into one,the NO concentration at the outlet of the heating flue is decreased by 195ppm,corresponding to a decrease of about 48.6%.The numerical simulation of the heating flue in this paper can not only make the researchers observe the complex gas flow in the heating flue,but also obtain the distribution of the components and temperature of each gas in the whole flow field,which provides theoretical bases for the structural design of a new coke oven.