焦化厂VOCs的臭氧生成潜势及二次有机气溶胶生成潜势分析

焦化厂因其工艺特殊,SO₂、NO_x、颗粒物及VOCs的排放问题较为突出。故对焦化厂厂界环境空气VOCs排放特征进行分析,并依据最大增量反应活性(MIR)法和等效丙烯浓度(PEC)法对VOCs的臭氧生成潜势(OFP)进行评估,依据气溶胶生成系数(FAC)法对VOCs二次有机气溶胶生成潜势(SOAFP)进行评估。结果表明:1)厂界上、下风向5个点位共分析出包括芳香烃、卤代烃、烯烃、硫化物、酮类在内的17种VOCs; 2)不同区域厂界检出的VOCs差异显著,总质量浓度为28.2~167.9μg/m3,其中芳香烃在各点位TVOCs中占比最大,达到51.01%~84.63%;3)脱硫提盐冷鼓区域边界OFP最大,理论值为335.51μg/m3,办公生活区边界OFP最小,理论值为47.06μg/m3,芳香烃对OFP贡献率为27.21%~62.37%,烯烃为39.17%~61.84%,卤代烃为2.08%~14.56%;通过PEC法估算OFP,结果变化趋势与MIR法结果相一致,等效丙烯浓度为3.11~31.89μg/m3;且1—5点位芳香烃的等效丙烯浓度贡献率分别为37.10%、51.46%、66.79%、58.80%和22.74%;4)1—5点位SOAFP分别为0.452,0.938,2.517,4.055,0.495μg/m3;芳香烃对SOAFP贡献最大。丙烯、甲苯、二甲苯、氯乙烯等质量浓度和反应活性均较大的物质,是需要优先控制的VOCs组分,可作为焦化厂环境空气VOCs的标志物。

ANALYSIS OF OZONE FORMATION POTENTIAL AND SECONDARY ORGANIC AEROSOL FORMATION POTENTIAL OF VOCs IN A COKING PLANT

Due to the special process of the coking plant, the emission problems of sulfur dioxide, nitrogen oxides, particulate matter and VOCs are more prominent. Therefore, the emission characteristics of VOCs in the ambient air at the boundary of the coking plant were analyzed, the ozone formation potential of VOCs was evaluated according to the maximum incremental reaction activity method(MIR) and propylene-equivalent concentration method(PEC), and the secondary organic aerosol formation potential of VOCs was evaluated, according to the fractional aerosol coefficients method(FAC). The results showed that: 1) a total of 17 VOCs including aromatic hydrocarbons, halogenated hydrocarbons, olefins, sulfides and ketones were analyzed at five points in the upwind and downwind direction of the factory boundary. 2) There were significant differences in VOCs detected at the plant boundary in different regions, and the total mass concentration was 28.2~167.9 μg/m3, in which aromatic hydrocarbons accounted for the largest proportion in TVOCs at each point, reaching 51.01%~84.63%. 3) The OFP at the boundary of the cold drum of desulfurization and salt extraction was the largest, with a theoretical value of 335.51 μg/m3, and the OFP at the boundary of office and living area was the smallest, with a theoretical value of 47.06 μg/m3. The contribution rate of aromatic hydrocarbons to OFP was 27.21%~62.37%, that of olefins was 39.17%~61.84%, and that of halogenated hydrocarbons was 2.08%~14.56%. The change trend of OFP estimated by PEC method was consistent with that of MIR method, and the propylene-equivalent concentration range was 3.11~31.89 μg/m3; the contribution rates of propylene-equivalent concentration of aromatic hydrocarbons at each point were 37.10%, 51.46%, 66.79%, 58.80% and 22.74%, respectively. 4) The formation potential of SOA at each point was 0.452, 0.938, 2.517, 4.055, 0.495 μg/m3, respectively; aromatic hydrocarbons contributed the most to the formation potential of SOA. Substances with high mass concentration and reaction activity, such as propylene, toluene, xylene and vinyl chloride, were the VOCs components that need priority control and could be used as markers of VOCs in the ambient air of coking plants.