Characteristics Of Volatile Organic Compounds Emission From Freight Container Manufacturing

Volatile organic compounds(VOCs)play a significant role in the formation of atmospheric aerosols and tropospheric ozone pollution,which can also cause great harm to human health.China is the largest freight container manufacturing base in the world.In the process of freight container manufacturing,we use a large number of paintings which emit a great quantity of VOCs.VOCs emission characteristics of freight container manufacturing industry has been studied in this work.The main processes of VOCs emission in freight container manufacturing is steel pretreatment and freight container surface coating.The average concentration of VOCs in workshop is 93.34mg/m~3 while in stack is 105.36 mg/m~3.The highest concentration among workshops and stacks is steel pretreatment workshop and stack.The largest proportion of VOCs species in workshops are alcohol ethers,accounting for more than 50%,followed by aromatic hydrocarbons,alkanes,esters and aldehyde ketones.The top 3 species are1-methoxy-2-propanol,dimethoxymethane and toluene.The most important part of VOCs emission from stacks are aromatic hydrocarbons,nearly 50%,followed by alcohol ethers,aldehyde ketones,alkanes and esters.The top 3 species are toluene,1-methoxy-2-propanol and dimethoxymethane.The VOCs emission factor of freight container manufacturing is 4.18 and4.62kgVOCs/TEU by using monitoring method and material balance method to calculate respectively.The annual VOCs emission of freight container manufacturing industry in 2018is 18003.24 tons.Steel pretreatment emission the largest amount with over 5,000tons.Speciated inventory showed that the largest emission category of VOCs was aromatic hydrocarbons and alcohol ethers,which contributed 46.48%and 40.18%respectively.The top10 species are toluene,1-methoxy-2-propanol,p-xylene,dimethoxymethane,ethylbenzene,o-xylene,isopropyl alcohol,ethanol,2-propoxy ethanol,dodecane and 1-butoxy-2-propanol,contributed 77.12%of the emissions.Compared with the speciated inventory,the contribution of aromatic hydrocarbons increased to 71.90%in the OFP inventory.The top 10 species toluene,p-xylene,1-methoxy-2-propanol,o-xylene,ethylbenzene,m-xylene,2-propoxyethanol,dimethoxymethane,1,2,4-trimethylbenzene and 1-ethyl-3-methyl-benzene,which contributed 85.29%of OFP.Using information entropy method to screen priority species,the result showed that there were 10 species in the first class,which were toluene,p-xylene,2-butanone,etc.The second class included 19 VOCs species while the other belonged to the third class.In the formulation of VOCs emission standards for freight container manufacturing,the control objects were recommended for benzene,toluene,xylenes,benzene homologues,aldehyde ketones,esters and VOCs.The limits should be determined after comparing the field monitoring data with the existing related standards data in detail.Management measures should be formulated along with the standard in the following aspects.Firstly,encourage the use of water-based paints.Secondly,strengthen process control.Thirdly,terminal treatment is recommended to use water spray combined with other technologies such as activated carbon adsorption,catalytic combustion,UV,etc.