(215f) Olefin Plant Flare Minimization Via Dynamic Simulation and Optimization

Flaring is a safety measure for ethylene plants to protect personnel, equipment, and their surrounding environment especially during plant abnormal operating conditions. However, flaring emissions during olefin plant startups, shutdowns, and upsets could cause tremendous material and energy losses to plants. Meanwhile, those flaring also releases large quantities of greenhouse gases (GHG), highly reactive volatile organic compounds (HRVOCs), and nitrous oxide (NOx) into the atmosphere, which could result in highly localized and transient ozone pollution events.  For instance, an ethylene plant with 1.2 billion pounds of ethylene production per year may flare five million pounds of ethylene during one typical startup, which generates 15.4 million pounds of CO₂, 7.5 K lbs of NO_X, 40 K lbs of CO, 100 K lbs of highly reactive VOCs. Therefore, flare minimization could bring significant benefits to environmental, societal, and olefin industry sustainability.

This paper will introduce systematic methodologies and new study achievements that have been developed at Lamar University for industrial flare minimization via plant-wide dynamic simulation and optimization. Since off-specification streams are inevitable during plant turnaround operations, to significantly reduce flaring emission, they must be either recycled to the upstream process for online reuse, or stored somewhere temporarily for future reprocessing, when the plant manufacturing returns to stable operation.  Thus, the off-spec products will be able to be reused instead of being flared.  This can be achieved through the identification of viable operation strategies through plant-wide dynamic simulation and optimization. The dynamic simulation/optimization provide an insight into process dynamic behaviors, which is crucial for a plant to minimize the flaring; meanwhile, maintain the operating safety. The effectiveness of the developed methodologies will be demonstrated by multiple case studies involving plant start-up, shutdown, and process upset from different ethylene processes.  Air-quality impacts associated with different turnaround operations are also studied.