(390c) Dynamic Simulations and Optimization for Chemical Plant Turnaround Flare Minimization Via Multi-Plant Material Exchange

Flare emissions during chemical plant turnaround operations, such as start-ups and shutdowns, emit huge amounts of NOx, volatile organic compounds (VOCs), highly reactive VOCs, and thus results in tremendous industrial material and energy losses. Therefore, flare minimization (FM) is a double win effort benefiting not only regional environmental sustainability but also industrial profitability. By far, available studies are almost exclusively focused on FM strategies for a single chemical plant. There are few systematic studies focusing on FM problems among multiple chemical plants. Actually, material exchanges (ME) among multiple chemical plants could provide an augmented degree of freedom for industrial material and energy savings and emission reductions. For example, a “waste stream” generated during turnaround operation from plant A could be sent to another normal-working plant B to recover potential products or reuse as the feedstock. Meanwhile, the normal-working plant B could provide assisting product streams under certain conditions (i.e. high pressure or low temperature) materials to support plant A to quickly complete its turnaround. Certainly, such ME operations involves very complicated operations and must be well designed and scheduled.

In this paper, a systemic methodology with multi-plant dynamic simulations and scheduling techniques have been employed to accomplish optimal ME operations for turnaround FMs among multiple chemical plants. To demonstrate the developed methodology, a case study for FM among three olefin plants has been performed, where Plant A is at normal-working status, plant B prepares to start-up, Plant C prepares to shut-down. Plant B could import certain flow from plant A to reduce the number of furnaces fired-up before CGC startup, further reduce flaring and saving start-up time. For Plant C, off-spec materials are vaporized and exported to different locations of plant A. Thus, some of those materials could be recovered. While applying these ME operations, different operation sequences lead diverse impacts on plant A’s production and total flaring amount. Therefore, to identify the optimal operations for not only FMs, but also ensure plant safety and operability, a series of plant-wide dynamic simulations with different schedules have been conducted. This study provides new aspect and in-depth understanding on synergies multiple plants ME operations for FMs.