石油炼化无组织VOCs的排放特征及臭氧生成潜力分析

摘要

选取我国光化学活跃的珠江三角洲地区(PRD)典型石油炼化工艺的炼油装置、化工装置和污水处理装置,采用离线和在线的多种先进仪器监测其VOCs的无组织排放特征,并采用间、对-二甲苯/苯(X/B)、甲苯/苯(T/B)、乙苯/苯(E/B)比值分析其VOCs的老化特征,采用最大增量反应活性法(MIR)、等效丙烯浓度法和OH自由基反应速率法(LOH)3种方法综合评价其VOCs的化学反应活性及臭氧生成潜势(OFP).研究发现,炼油装置区和化工装置区总挥发性有机物(TVOC)浓度早晚高,中午低;污水处理区呈双峰趋势.3个装置区无组织排放的VOCs中烷烃浓度均占比最高,同一装置区内的不同装置VOCs排放特征不同.石化企业X/B、T/B和E/B值较城区和郊区的高,化工装置区的压缩碱洗装置区(CAW)T/B值最大.石化企业VOCs的活性较城区和郊区的强,其平均OH消耗速率常数为15.22×10-12cm3/(mol?s),最大增量反应活性为4.21mol(O3)/mol(VOC).化工装置区对石化企业OFP总量的贡献最高,为84.83%;其次是污水处理区,12.95%;炼油装置区最低,为2.22%.化工装置区的CAW对石化企业OFP贡献率最高,为34.26%;污水处理区的浮选池(FT)贡献率最低,为0.36%.%Refinery installations, chemical installations and wastewater treatment installations of typical petrochemical facilities were selected in Pearl River Delta where the photochemistry was active. Multiple on-line and off-line monitoring instruments were used to analyze the fugitive emission characteristics of VOCs. The ratios of m, p-xylene/benzene (X/B), toluene/benzene (T/B) and ethyl benzene/benzene (E/B) were applied to analyze the aging characteristics of VOCs. The atmospheric chemical reactivity of VOCs and their Ozone Formation Potential (OFP) were evaluated by using Maximum Increment Reactivity (MIR), propy-equiv concentration and OH radical reactivity methods. The concentrations of TVOCs in refinery unit and chemical unit were both higher in the morning and night, lower at noon. However, for the wastewater treatment unit, it's bimodal. Alkanes were the most abundant species in all the three units, and VOCs emitted from different units were totally different. The ratio of X/B, T/B and E/B in petroleum refinery were higher than that in cities and suburbs, while T/B of Compression Alkali Washing area (CAW) in the chemical units was the highest. The photochemical reactivity of VOCs in the petroleum refinery was higher than that in cities and suburbs. Moreover, the average OH consumption rate of VOCs emitted from the petroleum refinery was 15.22×10-12cm3/ (mol·s), and the largest incremental reactivity was 4.21mol (O3)/mol (VOC). The OFP estimated from the VOCs in the chemical units accounted for the highest ratio, which is up to 84.83%. While the VOCs emitted from the wastewater treatment unit was the second, with the ratio of 12.95%. And, the contribution of refinery installation area was the lowest, with the ratio of 2.22%. The contribution of CAW in chemical installation unit to the OFP of the petroleum refinery was the highest with the ratio of 34.26%. The contribution of Flotation Tank (FT) in wastewater treatment unit was the lowest with the ratio of 0.36%.