Study On Influence Of Exhaust Gas Circulation On NO_x Formation In Coke Oven

With the rapid development of China’s economy,environmental issues have also been increasingly valued by people.In recent years,the problems of dust pollution and SO2 pollution have been properly dealt with in coking enterprises.However,the measures treatment of nitrogen oxide have not been perfected,and a host of enterprises are still exceeding the standard of NOx emissionsFlue gas circulation technology(FGCT)is one of the important measures to control the NOx emissions of coke oven.The existing coke ovens adopt the method of opening the inner circulation hole to realize the circulation of flue gas inside the vertical flue,so as to achieve the goal of reducing the generation of NOx.As the continuous improvement of national environmental standards,coking enterprises only rely on the internal circulation technology of flue gas,which has been unable to meet the low NOx emission standards.In this paper,the method of increasing the external circulation of flue gas to reduce NOx emissions was put forward,and the effects of the external circulation of flue gas on the combustion characteristics and NOx generation characteristics of the heating flue was studied.Firstly,the combustion model of coke oven gas was established based on the JN60 type coke oven single opposed heating flue,the effect of external circulation of flue gas on Combustion Characteristics and NOx generation characteristics of flue gas was studied by CFD numerical simulation method.Under different air consumption coefficients,the effect of the external circulation of flue gas on the combustion characteristics and NOx generation characteristics of the heating flue was analyzed.The results showed that with the increase of the external circulation rate,the maximum temperature in the vertical flue decreased obviously,and the NO concentration at the outlet of the vertical flue decreased significantly,however,the average temperature,the temperature of the turning point,the temperature of the circulating hole,and the outlet temperature of the flue gas did not change much.When the air consumption coefficient was 1.05,the circulation rate was 0%,no external circulation,the NO outlet concentration was 1307 mg/m3;when the circulation rate was 8%,the NO outlet concentration was 530 mg/m3;when the circulation rate was 10%,the NO outlet concentration was 423 mg/m3(Meet the national standard).When the circulation rate was 20%,the NO outlet concentration was 151 mg/m3,which was 88.5% lower than that of without the external circulation.In order to further study the effect of flue gas circulation on NOx in the coke oven,experimental platform for flue gas external circulation system of simulated coke oven was designed and built,and the related experiment was carried out in this experimental platform.The results showed that increasing the external circulation of flue gas can effectively reduce the NOx production.The experimental results are in agreement with the results of CFD simulation.The research results of this project have practical significance and reference value for solving NOx pollution problems and combustion optimization in the production process.