Study On Volatile Organic Compound Emission Characteristics And Whole Process Control Of Coal-to-oil Project

The primary pollutants at this stage in China are PM2.5 and O₃,and the main contributing source is the emission of volatile organic compounds(VOCs).Strengthening the governance of VOCs is an effective way to control PM2.5 and O3pollution.The sources of VOCs include natural sources and anthropogenic sources.The air quality is mainly affected by anthropogenic sources,and industrial sources account for 1/3?1/2 of anthropogenic sources.The key to control VOCs from anthropogenic sources is to control VOCs from industrial sources.The coal chemical industry is one of the key industries of VOCs emission,the treatment of VOCs started late,and there are no targeted source item investigation guidelines,emission coefficient,and standards.It is of great significance to carry out research on the VOCs emission characteristics and the entire process control of coal-to-oil projects.In this paper,the VOCs materials of the coal-to-oil project were identified,the VOCs source item investigation was carried out,the VOCs source item list was established,the organized and unorganized detection and data analysis were carried out,and the VOCs emission characteristics of the project were obvious.The results showed that organized sources emissions accounted for 37.37%of total emissions,and unorganized sources accounted for 62.63%.Among the organic sources,low-temperature methanol scrubbing exhaust gas VOCs emits the largest amount,accounting for 51.42%of the total organizational emissions,among the combustion flue gas exhaust outlets,the gasification hot blast stove emissions gas emissions were the largest,accounting for 84.33%of the total combustion flue gas emissions.Among the unorganized sources,the discharge of the wastewater during the process of gathering,transporting,storing,and treating was the largest,accounting for 75.61%of the total unorganized sources.The focus of controlling VOCs emission in the coal-to-oil project is to control the unorganized emission,and the first controlled organized emission outlet is the exhaust gas from low-temperature methanol washing and the exhaust gas from gasification hot blast stove.Among the static and dynamic sealing points,static sealing points were the most,accounting for 99.56%of the total number of sealing points.According to the classification of the medium,the heavy liquid sealing points were the most,accounting for 59.73%of the total sealing points.According to the type of components,flange sealing points account for 69.73%of the total number of sealing points,and valves account for 19.29%;static and dynamic sealing point leakage rate was 0.07%,the repair rate was 98.22%,and the total leakage rate after the repair was 0.0013%;flange leakage points accounted for the largest proportion,accounting for 62.72%of the total leakage points,followed by open pipelines and valves;light liquids were the most prone to leakage than heavy liquids;leakage points caused by loose bolts accounted for the total leakage 73.37%of the points,10.06%of them leaked due to valve packing leakage.Bolt looseness was the main cause of sealing point leakage.According to the calculation of oil production in 2019,1.68 kg of VOCs were emitted per unit of oil,0.41 kg of VOCs were emitted per unit of oil,0.0074 kg of VOCs were emitted per unit of oil sealing point,and 0.0059 kg of VOCs were emitted per unit of oil.Refer to the"Guidelines for the Investigation of VOCs Pollution Sources in the Petrochemical Industry",the Coefficient method was used to calculate the leakage of the static and dynamic sealing points of the equipment,which was 129.74 times the correlation equation method,with a large deviation;the average non-methane total hydrocarbon emission concentration of the high-pressure pulverized coal boiler was 1.89 mg/m³.The emission factor of VOCs was 0.015 g/kg coal(in terms of non-methane total hydrocarbon),which was 0.1 times the emission factor of 0.15 g/kg in the existing"Technical guidelines for the Compilation of Atmospheric Volatile Organic Matter Sources Emission Inventory",which was the emission used in environmental statistics in 2018.The coefficient was 0.6 times that of 0.025 g/kg coal.In environmental statistics,the existing coefficient was used to calculate the total VOCs emission of coal-to-oil boilers with a large deviation.