A win-win strategy for simultaneous air-quality benign and profitable emission reduction during chemical plant shutdown operations

Although the flaring system is designed for the safety operation in chemical plants, the intensive flaring will cause not only tremendous raw material loss, but also large amounts of VOCs and NOx, which could escalate regional ozone formation and elevation under the solar radiation. Thus, it will be a win-win situation to preform air-quality conscious flare minimization (FM) for chemical plants, so that both environmental and industrial sustainability could be promoted. In this study, a systematic multi-scale methodology has been established to identify and demonstrate the win-win strategy for simultaneous air-quality benign and profitable emission reduction during chemical plant shutdown (CPS) operations. The major contribution of this study is that process-level dynamic simulations via Aspen Plus Dynamics have been seamlessly integrated with the regional-level air-quality modeling via CAMx to simultaneously accomplish both flare source savings and ozone impact minimization during the CPS operation. Case studies have indicated that the base case of CPS without FM could have a serious effect on the air-quality (1.6 ppb 8-h ozone observed). However, the improved case of CPS based on FM would significantly reduce such an ozone impact (only 0.1 ppb 8-h ozone observed); meanwhile the flare source and CO2 emission reductions, as well as the plant economic savings are respectively 165.2 tons, 479.1 tons, and US$133,945.6.

尽管火炬系统是为化工厂的安全运行而设计的，但强烈的火炬燃烧不仅会造成巨大的原料损失，还会产生大量的挥发性有机化合物（VOCs）和氮氧化物（NOx），在太阳辐射下，这可能会加剧区域臭氧的形成和浓度升高。因此，对化工厂实施注重空气质量的火炬最小化（FM）将是一种双赢的局面，这样既能促进环境可持续性，也能促进工业可持续性。在这项研究中，建立了一种系统的多尺度方法，以确定并论证在化工厂停工（CPS）操作期间同时实现空气质量友好和有利可图的减排的双赢策略。这项研究的主要贡献在于，通过Aspen Plus Dynamics进行的过程级动态模拟已与通过CAMx进行的区域级空气质量建模无缝集成，以便在CPS操作期间同时实现火炬源节约和臭氧影响最小化。案例研究表明，没有实施火炬最小化的化工厂停工基础案例可能会对空气质量产生严重影响（观测到8小时臭氧浓度为1.6 ppb）。然而，基于火炬最小化的改进后的化工厂停工案例将显著降低这种臭氧影响（观测到8小时臭氧浓度仅为0.1 ppb）；同时，火炬源和二氧化碳减排量以及工厂经济节约分别为165.2吨、479.1吨和133,945.6美元。