Research On The Impact Of Coking Industry On Air Quality In Wuhai City Based On CMAQ Model

As a high energy consumption and high pollution industry,the coking industry is one of the important air pollutant emission industries.A large amount of smoke and exhaust gas is discharged during the coking process,which significantly influences the ambient air quality and human health.China is an important coke producer in the world and accounts for 67%of the world’s coke production in 2018.Inner Mongolia’s coke production accounts for 7.7%of the country’s coke,and Wuhai’s coke production ranks first in the Nei Monggol Autonomous Region.As the main industry of Wuhai City,the coking industry has a huge impact on Wuhai’s economic development and people’s health.Quantifying the impact of Wuhai’s coking industry on the air quality of Wuhai City can provide a scientific basis for formulating control measures and air pollution prevention programs for coking industry.We take the coking industry of Wuhai City as the research object to study the impact of coking industry emissions on key pollutants and some of their important precursor pollutants in the air quality of Wuhai City.By analyzing the ambient air quality of Wuhai City from 2015 to 2018,the key pollutants in Wuhai City were determined.Based on the literature and field research,the emission factors of different processes of the coking industry were determined,and the emission factor method was mainly used to establish the coking industry emissions inventory of Wuhai City in 2018.The main production processes and key pollutants of pollutants discharged from the coking industry were determined.Taken the air quality situation of Wuhai City and the emission characteristics of the coking industry into consideration,the pollution period of key pollutants particulates and O₃ from June 4th to 9th,2018 are selected.The WRF model provides meteorological field data,and the SMOKE model provides pollution source data.The CMAQ model is employed to quantify the pollution contribution of NO₂,O₃,PM₁₀0 and PM_2.5.5 in the air quality of Wuhai City discharged by the coking industry,by setting the source strength of Wuhai City’s coking industry to zero.The main conclusions are as follows:（1）The ambient air quality in Wuhai City has improved from 2015 to 2018,and SO₂ and PM_2.5.5 have been decreasing year by year.Particulate matter(PM₁₀0 and PM_2.5)pollution has been a long-standing problem,and O₃ pollution has become increasingly serious.Therefore,the key pollutants in Wuhai City are particulate matter and O₃.（2）In terms of the emission factors of pollutants in different sections of the coking industry process,the emission coefficient of the coke oven chimney is the largest and is 0.075 and 0.533 kg/t coke for the emission links of SO₂ and NO_X,respectively.In the emission links of particulate matter(PM₁₀0 and PM_2.5),the coke quenching,coke oven body and coke oven chimney exhibit large emission coefficients.The emission coefficients of PM₁₀0 are 0.086,0.061 and 0.041 kg/t coke respectively,and the emission coefficients of PM_2.5.5 are 0.054,0.038 and 0.026 kg/t coke,respectively.In the emission link of CO,the coke quenching and coke oven chimneys have larger emission coefficients,which are 0.447 and 0.437 kg/t coke,respectively.In the emission link of VOCs,the emission coefficient of the coke oven chimney is the largest.（3）The coking industry routinely discharges VOCs,CO,NO_X,particulate matter and SO₂,among which VOCs,CO and NO_X are larger than other pollutants.In the air pollution emission inventory of coking industry,the VOCs are 39,819.51 tons/year,accounting for 57.94%of the city’s emissions.The CO emissions are 11,571.48tons/year,accounting for 6.44%of the emissions.The NO_X emissions are 7480.61tons/year,accounting for 9.37%of the city’s emissions.The emissions of PM₁₀0 and PM_2.5.5 are 3377.38 tons/year and 1964.67 tons/year,respectively,accounting for 1.80%and 3.09%of the city’s emissions.The SO₂ emissions are 989.56 tons/year,accounting for 1.29%of the city’s emissions.In the production links such as coal preparation,coking,and chemical product recovery,the pollutants discharged by the coking process account for the largest proportion of the total emissions of the coking industry,of which VOCs,CO,SO₂ and NO_X account for more than 90%.（4）By simulating the spatial distribution of pollutants NO₂,O₃,PM₁₀0 and PM_2.5discharged by the coking industry during the simulation period,it was found that the pollutant diffusion direction was consistent with the regional wind direction.The high concentration of NO₂ is mainly concentrated in the northern part of Haibowan District and the central part of Hainan District.The high concentrations of PM₁₀0 and PM_2.5.5 are mainly concentrated near the coking sources.The spatial distribution of O₃ is different from other pollutants.During the daytime（9:00-20:00）,the production of O₃ is inhibited by high concentrations of NO_X near the coking source,but the shorter the evaluation time scale,the smaller the nitrogen oxide suppression area.（5）Among the contribution of pollutants discharged by the coking industry in the simulation period to the impact of the three urban stations of Wuhai City during the simulation period,the period average,maximum daily average and maximum hourly contribution concentration of NO₂,PM₁₀0 and PM_2.5.5 are the largest in Hainan District,followed by the Wuda District and the smallest in the Haibowan District.In Haibowan District and Hainan District,pollutants discharged by the coking industry contributed larger to the daytime averaged concentration,maximum 8-hour averaged concentration and maximum hourly concentration of O₃ during the simulation period.Compared with PM₁₀0 and O₃,the pollutants discharged by the coking industry have a greater impact on the contribution of NO₂ and PM_2.5.5 in Wuhai City.The contribution of coking industry to the average concentration of NO₂ is 2.06%⁷.47%;the contribution to the maximum daily average concentration is 3.53%¹5.66%;the contribution to the maximum hourly concentration is 6.72%²3.35%.The contribution of the coking industry to the maximum 8-hour average concentration of O₃ is 0.59%¹.83%;the contribution to the maximum hourly concentration is 2.11%⁴.90%.The contribution to the average concentration of PM₁₀0 is 0.74%².32%;the contribution to the maximum daily average concentration is 1.07%⁸.01%;the contribution to maximum hourly concentration is 1.87%⁹.77%.The contribution of the coking industry to the average concentration of PM_2.5.5 is 1.13%³.18%;the contribution to maximum daily average concentration is 2.34%⁸.68%;the contribution to maximum hourly concentration is 3.52%¹5.56%.