Air-Quality Conscious Study for Multiple Olefin Plants' Turnaround Operations

Ground-level ozone is a pervasive air pollutant, which can be potentially elevated by flaring emissions during turnaround operations (e.g., shut-down or start-up) of chemical plants. Especially in chemical plant concentrated regions, the local ozone concentration can be aggravated by simultaneous start-up and shut-down operations. Thus, it is environmentally and cost-effective important for study on multiple plant turnaround operations under allowable manufacturing constraints to minimize the induced potential adverse air-quality impact. In this paper, a systematic methodology on air-quality conscious study for multi-plant turnaround operations has been developed. Through case studies, it demonstrates that multi-plant turnarounds without any coordination could result in the worst air quality impact (i.e., 11.4 ppb of maximum 8-hour ozone increment); however, the optimal scheduling plan with several-hour difference tuning on their turnaround starting time would significantly reduce such impact (only 1.4 ppb of maximum 8-hour ozone increment). The study couples process-level dynamic simulation for flare emissions with regional-level air-quality modeling together; and explores cost-effective and environmentally benign air-quality control strategies. It provides valuable quantitative supports for relevant stakeholders, including environmental agencies, regional plants, and local communities.