Air-quality Conscious Coordination for Multiple Olefin Plant Startup and Shutdown Operations

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