Challenge
During a scheduled refinery turnaround, a customer needed to safely degas their Selective Hydrocracking Unit to perform critical maintenance. The unit would undergo hot hydrogen stripping to purge residual hydrocarbons, but strict emission control limitations at the facility’s flare stack required an alternative vapor control system for handling high volumes of hydrogen and nitrogen gas.
To meet both safety and regulatory compliance, the customer required a turnkey mobile vapor control solution capable of managing near-100% hydrogen vapors and 100% nitrogen displacement vapors while reducing internal atmosphere concentrations to below 2% LEL.
Solution
Envent Corporation deployed three of its Envent Mobile Emission Control Systems (EMECS)—mobile thermal oxidizer units engineered for high-capacity vapor destruction. The system was designed to:
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Combust up to 10 MMSCFD of hydrogen gas and 5 MMSCFD of nitrogen vapor streams
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Handle depressurization of high-pressure hydrogen using auxiliary regulators
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Maintain >99.9% destruction efficiency (DRE), exceeding EPA BACT and MACT standards for refinery vapor control
To complete the purge, Envent supported a series of nitrogen purging and huff-and-puff cycles, venting the nitrogen-rich vapors to the EMECS units until hydrocarbon levels reached LEL-free status, ensuring the system was safe for maintenance access.
Benefit
Envent’s mobile degassing solution reduced the customer’s planned downtime by an entire day, completing the hydrocracking unit degassing in under 24 hours. The use of mobile thermal oxidizers over the facility flare reduced VOC, NOx, and CO emissions, with combustion efficiency proven to be over 20 times greater than the on-site flare system.
This project showcased Envent’s unmatched ability to deliver safe, cost-effective, and compliant vapor control services during complex refinery maintenance operations. With the largest fleet of mobile thermal oxidizers, hydrogen sulfide vapor control equipment, and deep regulatory expertise, Envent enabled the facility to maintain emissions compliance, protect nearby communities, and accelerate its return to production.
