(374ax) Flaring Emission Source Characterization During An Ethylene Plant Start-up

Ethylene plant startups usually have to flare large quantities of off-spec gas products, which emit tremendous amounts of CO, CO2, NOx, VOC, HRVOC (defined in Texas air quality regulation as ethylene, propylene, isomers of butene, and 1,3-butadiene), and partially oxygenated hydrocarbons. The emission will cause highly localized and transient air pollution events and negative societal impacts. Thus, proactive flare minimization strategies through predictive process design and operation are becoming more important and attractive to the industry. However, fundamental and quantitative studies on start-up flaring emissions are still lacking.

Through the plant-wide dynamic simulation, this paper compares ethylene plant flare minimization performances under different start-up strategies. Deep insights of the emission source distribution and simulated dynamic emission profiles are provided with respect to the start-up operation procedures. Partially scientific answers for the following three questions are thus identified: i) what kinds of emission species are contained in the flaring sources; ii) how much of each emission source will be generated during one start-up; and iii) what is the dynamic emission profile of each emission source with respect to the start-up time? The study enriches the emission inventory with details for industry point sources, which have never been compiled previously. It also provides detailed technical support for both the industry and environmental agencies on evaluating and developing cost-effective flare minimization strategies in the future.