Chemical plant shutdown (CPS) operations will employ a flare system to combust waste, unwanted, and off-spec gases dumped from process units to protect the plant safety and the local community. However, the incomplete combustion of flare source under CPS operations including plant planned shutdown (PPS) and plant emergency shutdown (PES) will cause considerable air pollution events. Hitherto, quantitative studies on both primary (CO and NO) and secondary (ozone) pollutant impacts induced by CPS flaring are still lacking. In this paper, the dynamic effect of flare emissions from two types of CPS (PPS and PES) on ambient air-quality impacts will be systematically and quantitatively studied. The study integrates the dynamic process simulation via Aspen Plus Dynamics with the regional air-quality modelling via Comprehensive Air-quality Model with extensions (CAMx). Case studies indicated that the primary pollutants from flare emissions will be significantly diluted due to the atmospheric transportation, and the maximum concentrations of CO and NO can respectively reach 119.0 and 11.0 ppb under PPS, and 47.5 and 4.5 ppb under PES. Meanwhile, the increasing height of the flaring stack will decrease CO and NO concentrations but increase the ozone concentration under CPS. Furthermore, CPS in daytime periods will greatly promote ozone generations due to the enhanced photochemical reactions under solar radiation. The maximum 1-hr and 8-hr ozone increment can be 16.6 and 7.1 ppb under PPS while 10.7 and 3.3 ppb under PES, respectively. Besides, the decreasing of flare destruction and removal efficiency will increase ozone and CO under PES.

中文翻译：

---

关于计划或紧急关闭操作下化工厂火炬排放对空气质量影响的综合研究†

化工厂关闭（CPS）操作将采用火炬系统来燃烧从工艺装置中倾倒的废物、不需要的和不合格的气体，以保护工厂安全和当地社区。然而，工厂计划停工（PPS）和工厂紧急停工（PES）等CPS操作下火炬源的不完全燃烧将造成相当大的空气污染事件。迄今为止，仍然缺乏对 CPS 燃烧引起的一次污染物（CO 和 NO）和二次污染物（臭氧）影响的定量研究。本文将系统、定量地研究两种类型的CPS（PPS和PES）的火炬排放对环境空气质量影响的动态效应。该研究将通过 Aspen Plus Dynamics 进行的动态过程模拟与通过扩展综合空气质量模型 (CAMx) 进行的区域空气质量建模相结合。案例研究表明，火炬排放的主要污染物会因大气输送而被显着稀释，在PPS下CO和NO的最大浓度分别可达119.0和11.0 ppb，在PES下可达47.5和4.5 ppb。同时，火炬烟囱高度的增加会降低CPS下CO和NO浓度，但会增加臭氧浓度。此外，由于太阳辐射下光化学反应的增强，白天的CPS将极大地促进臭氧的产生。在 PPS 下，1 小时和 8 小时的最大臭氧增量分别为 16.6 和 7.1 ppb，在 PES 下分别为 10.7 和 3.3 ppb。此外，PES下火炬破坏和去除效率的降低会增加臭氧和CO。