(579c) Scheduling of Multiple Chemical Plant Start-Ups for Minimizing Regional Air Quality Impacts

Chemical industrial regions concentrate many chemical plants, whose emissions may case highly localized and transient air pollution events violating national ambient air quality standards (NAAQS).  Flaring emissions, especially the intensive start-up flaring, emits huge amounts of pollutants, which has potentially significant impacts on local air quality.  Give the situations that many chemical plants are spatially located in an industrial region and their startup flare emissions exhibit significant temporal variability.  Such variability may cause an unexpected coincidence of flare emissions casing local air quality problems.  Therefore, from the emission control point of view, the best practices for improving regional air quality should integrate both efforts on plant-wide emission minimization at every industrial point source, and regional-wide multi-plant emission variability control.

In this paper, a scheduling methodology for coordinating multiple chemical plant start-ups is developed to minimize regional air quality impacts.  This methodology includes two stages of work.  In the first stage, geometric locations of plants and air quality monitor stations are both taken into account.  Each plant proposes its startup time window, emission profile, and expected start-up time.  In the second stage, a scheduling model for regional chemical plants’ startup is developed.  The objective of the model is to reschedule multi-plant start-up sequence to achieve the minimum sum of delay time compared to the expected start-up time of each plant.  Certainly, the major constraints include the atmosphere dispersion model constraints and predicted air quality indexes from air quality monitor stations satisfying NAAQS.  The development provide quantitative decision support for multiple stake holders, including government environment agencies, chemical industry, and local communities.