Effectiveness Of The Environmental Protection Measures For Methanol To Olefins Units And Its Compensatory Advice

Both of the ethylene and propylene are an important organic chemical material.The development level and the industry scale of the petrochemical industry are directly affected by these two kinds of material’s market supply and demand.The "13th five year plan" of the petrochemical industry points out that:Develop the industry of coal to olefin and propane dehydrogenation for propylene,increase the proportion of non-petroleum-based products in ethylene and propylene production.The development of coal to olefin industry is beneficial to improve the product layout of the traditional coal industry,and alleviate the current situation of petroleum shortage in China.The MTO unit,which is connecting the methanol synthesis unit and the olefine separation unit,is the most critical unit in the whole industry chain of coal to olefin.The MTO industry is developing rapidly in recently years.Meanwhile,relevant policies have been introduced to support the deep processing of coal demonstration project.However,the related content of environmental protection didn’t involve in these policies.Whether or not the engineering demonstration is also the environmental protection demonstration hasn’t been explicitly determined.Based on the on-site survey and the information collection of many domestic MTO units,the generation and discharge node of pollutant are conducted via deeply parsing the production process.Meanwhile,the common environmental protection measures of MTO unit,the source of pollution and the influence factors of pollutant emission from the whole process standpoint are all concluded.By taking a typical MTO unit as the research obj ect,the validity of its environmental protection measures is assessed,then compensatory advice is proposed according the defect of the environmental protection measures.The exhaust gas and the wastewater are both originated from the process of reaction and coke burning,while the solid waste is originated from the catalyst fines which is separated from the unit.The process of waste gas treatments is mainly included cyclone separation,incineration etc.Then the discharge port is mainly included the waste heat boiler and the commission heater.The processes of wastewater treatment are mainly including oil separation hydro cyclone separation,subsidence,striping etc.Then the outfall is mainly included the quench tower and the striping tower.The solid waste always sent to the qualified authority to collect and disposal.Based on the source term analysis of the typical MTO unit,the pollutants production is mainly affected by the content of moisture,heavier components and metal ions of the raw methanol,as well as the mechanical strength,selectivity and the activity of MTO catalysis.By taking the typical MTO unit as the research object,the validity of environmental protection measures is assessed,and the conclusions are as follows:Both the emission of exhaust gas and solid waste could reach the standard.While the treatment of wastewater is difficult to obtain an ideal result which is because the oil,wax and particulates in the waste water.After a series of technical modification measures specific to improve the wastewater quality,there are still some problems,for example,the water in wastewater tank is still with high oil and particulate matter,and the quality of purified water from striping tower varied large.According to the defects described above,compensatory advice is proposed on the"whole process" prospective which is from the aspect of source control,process control,end treatment and resource utilization.Furthermore,this research provides a scientific basis for the subsequent MTO units.