Emission Characteristics Of Volatile Organic Compounds From Typical Industrial Sources On Coal-related Processes

Volatile organic compounds（VOCs）had become the main cause of aggravating atmospheric combined pollution in China.Studies had shown that VOCs were key precursors of fine particles and ozone（O₃）.It is particularly important to explore a suitable treatment path of VOCs for our country.The chemical composition profiles,the basis for VOC emission control,were useful to analyses the chemical composition and relative contribution of emission sources.Although the source profiles of typical emission sources of VOCs in China has been initially established,some industrial source profiles were still missing（such as cement and ceramics industry etc.）.The research of source profiles of iron and steel smelting had not been refined into various process links.The stack gases of coal-related processes were sampled and measured from steel plant（coking,sintering,pelletizing and iron smelting）,cement plant（kiln head and kiln tail）and ceramics plant（spray drying and fired kiln）in this study.Concentrations,source profiles,emission factors,ozone formation potentials and control measures of each process were preliminarily discussed.In order to perfect the localized VOCs source profile database,identify the main pollution emission links,and provide data support for the targeted control of VOCs.The main results are as follows:（1）Pelletizing gave the highest VOCs concentrations（12985.67±4264.14μg/m³）,followed by sintering（6563.54±520.23μg/m³）,iron smelting（2509.63±579.79μg/m³）and coking（1047.18±73.61μg/m³）in steel plant.The concentration of TVOCs in kiln tail（6854.64±2158.62μg/m³）was 6.8 times higher than that of kiln head in cement plant.In spray drying and firing kiln of ceramic plant,the concentrations of TVOCs were 1242.30±993.25μg/m³ and2334.91±1050.01μg/m³,respectively.The concentration of TVOCs in each process was relatively high.So it is necessary to pay attention to its control.（2）Alkanes,alkenes,aromatics and chlorinated hydrocarbons accounted for21.95～27.12%of the coking in steel plants,among which dichloromethane（18.32%）,styrene（17.65%）and 1-butene（14.03%）were the highest monomers.Alkenes in sintering and pelletizing processes accounted for 47.42%and 77.98%respectively,and 1-butene was the most abundant compounds,accounting for38.94%and 72.94%in two processes.The aromatics（49.25%）in iron smelting accounted for the highest proportion,and styrene（43.21%）was the main specie.The proportion of VOCs in cement plant kiln head and kiln tail was quite different:The highest proportion in kiln head flue gas was Alkanes（61.24%）,of which C4-C5（49.91%）were the main species,while 1-butene（23.28%）,methyl bromide（14.62%）,acetylene（12.74%）,and benzene（12.45%）in kiln tail flue gas were the most abundant compounds.The composition of spray drying and firing kiln in ceramic plant was similar:the proportion of alkene was the highest（70.84%and 76.13%respectively）,and 1-butene was the main compound,accounting for 61.08%and 71.65%,respectively.（3）The emission factor of VOCs in sintering,pelletizing and iron smelting were 0.006,0.009 and 0.002 g/kg,respectively.The emission factor of VOCs in cement was 0.019 g/kg.The emission factor of VOCs in ceramic production wws 0.278 g/m².（5）There was a certain difference between the VOCs chemical profiles in each process（coefficient of divergence ranged from 0.318 to 0.675）.VOCs from the process links in this study show characteristic compositional patterons compared to those from emission sources like vehicle exhaust,solvent use,petrochemical,etc.A major distinction is the relatively high 1-butene levels.Hence,Source profiles,which obtain in this study with unique characteristics,could be used for sources apportionment in China,especially in the area around the steel,cement and ceramic plants.（6）Pelletizing gave the highest ozone formation potential（OFP）concentrations（104414.60μg/m³）,followed by sintering（37699.01μg/m³）iron smelting（7225.54μg/m³）and coking（3411.14μg/m³）in steel plant.The concentration of OFP in kiln tail（23860.97μg/m³）was higher than that of kiln head（2127.26μg/m³）in cement plant.In spray drying and firing kiln of ceramic plant,the concentrations of OFP were 9222.60μg/m³ and 18049.36μg/m³,respectively.Alkanes,Alkenes and aromatics contributed 36.03%,27.48%and34.56%to OFP in kiln tail,among which isopentane,1-butene and ethylene were the three most important monomers（accounting for 56.44%of total OFP）.Alkenes were the most sensitive components in the remaining 7 processes（accounting for 54.68%～96.37%）,and the most sensitive monomer was1-butene.（7）Multi-stage adsorption concentration+condensation recovery or adsorption concentration+regenerative catalytic oxidation/thermal oxidizer（RCO/RTO）combined technology could be selected for treatment based on the flue gas discharge rate and VOCs concentration of each process in this study.