基于包扎法的石化乙烯装置挥发性有机物排放特征

装置泄露是石油炼化生产过程中重要的挥发性有机物(VOCs)无组织排放源.基于动态吹扫包扎法采样和预浓缩­­-GC/MS分析方法,对我国南方某石化企业乙烯生产过程中裂解装置的压缩、分离系统及芳烃抽提装置的泄漏组件进行了VOCs排放特征研究.结果表明:烷烃(49.7%~82.4%)含量最高,其次是烯烃(3.2%~35.7%)和芳香烃(5.5%~14.4%); 2-甲基戊烷、甲基环己烷、3-甲基己烷及2,3-二甲基丁烷在整个乙烯生产中都有重要比重.乙烯和反-2-丁烯是裂解装置的重要标志,而苯和甲苯是芳烃抽提装置的重要标志;臭氧生成潜势主要来自于烯烃,尤其是乙烯的贡献率最大,占总烯烃贡献的47.0%~73.0%.参考美国环保局推荐的Method-21,计算了轻液介质阀门的排放速率,获得其泄露排放速率与泄露浓度之间的定量关系为y=3×10^-7x^0.993(R²=0.788).

Emission characteristics of volatile organic compounds emitted from an ethylene process unit in petrochemical industry based on blow-through method

Equipment leakage is an important fugitive source of volatile organic compounds (VOCs) in petroleum refined industry. A novel blow-through sampling technique together with a preconcentrator-GC/MS equipment were employed to investigated emission of VOCs from equipment leakage of cracking apparatus (including compressed system, separation system) and aromatic extraction apparatus in an ethylene process unit in south China. The VOCs emitted from the process were mainly composed of alkanes (49.7%~82.4%), alkenes (3.2%~35.7%) and aromatics (5.5%~14.4%). 2-methylpentane, methylcyclopentane, 3-methylhexane and 2,3-dimethylbutane were abundant in the process. Ethylene and trans-2-Butene were discovered to be special species for cracking apparatus, while benzene and methylbenzene were the important ones for aromatic extraction apparatus. Further analysis indicated that alkenes contributed the most to ozone formation potential (OFP), among which ethylene accounted for 47.0%~73.0% to the OFP. According to US EPA Method-21, the leak rate of the light liquid valves was estimated, and the unit-specific correlation between leak rate and concentration was established as y=3×10^-7x^0.993(R²=0.788).