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• Integrated refinery and cracker plant, processing Naphtha, Ethane, Propane, LPG as feed, experiencing high Vinyl Acetylene in their Mixed C4 feed. Severity controlled, however, VA concentration is very high. We are interested in understanding the likely reasons for high Vinyl Acetylene formation? What are the parameter need to be checked to control Vinyl Acetylene concentration? What parameters should be monitored to maximize the throughput of the butadiene unit while limiting Vinyl Acetylene contamination?

  Oct-2024

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Answers

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• Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

  Unfortunately, this is a relatively common operating issue in naphtha steam cracking units. Normally, the C3/C4 streams from the steam cracker contain low concentrations of acetylene derivatives known as MAPD (including vinylacetylene) which needs to be removed in order to avoid catalyst poisoning of downstream processes or undesidered side reactions. As informed in the question, once the severity of the naphtha steam cracking process is under control, it's important to evaluate the quantity of vinylacetylene is produced in the process plant, according to the literature is considered normal a production of 0,5 to 2,0 wt % in the C4 stream which can impact the efficiency of the butadiene solvent extraction step. To minimize this issue, normally the operators install a selective hydrogenation step downstream of the steam cracking in order to convert the MAPD compounds into C2 fraction preserving the olefins. If the process do not has a selective hydrogenation step, it's necessary to carry out a technical and economic study to install this process once is very hard to control the MAPD formation manipulating process variables of the steam cracking, the best way is control the process severity which is under control considering the question information and presents the side effect of economic impact related to the olefins yield. A very good reference about this issue is the article published in the Q2 2024 issue of PTQ Magazine by Edgar Jordan, Charlotte Fritsch, and Joachim Haertlé, which you can VIEW HERE

   

  Oct-2024