2024 Hydrocracking Unit: Depressurization

2024 Hydrocracking Unit: Depressurization

Portfolio Categories: Case Studies, Turnaround Services, and Vapor Control.


A customer facility held a turnaround in which their Selective Hydrocracking Unit would be taken out of service for scheduled maintenance. The unit would be purged of residual hydrocarbons through a hot hydrogen stripping process, but due to emissions limitations at the facility flare, the hydrogen would need an alternative route to be vented. Additionally, the unit would require nitrogen purging in order to get the internal atmosphere to less than 2% LEL. The customer would require a turnkey system that could handle nearly 100% hydrogen vapors as well as 100% nitrogen vapor streams.



Envent would provide this customer with three of our EMECS thermal oxidizer units in order to combust vapors efficiently as an alternative route to the flare. Envent’s system was capable of combusting up to 10 MMSCFD of hydrogen gas as well as 5 MMSCFD of nitrogen. Hydrogen gas was de-pressured safely to the thermal oxidizers using auxiliary high-pressure regulators and combusted at a 99.9% destruction rate efficiency. Then, the customer was able to purge the residual hydrocarbon LEL from the system using “huff-and-puffs” to vent nitrogen to the thermal oxidizers. The process was continued until the customer was able to achieve an LEL-free gas sample from the unit, signally the end of the vapor control phase.



From start to finish, Envent completed the Hydrocracking Unit degas in less than 24 hrs of operation. Envent was able to remove one full day of planned down time from the customer schedule, resulting in significant cost savings and the ability to resume operations more quickly. Additionally, facility emissions for VOC, NOx and CO were severely limited while using the thermal oxidizer as its combustion efficiency of 99.9% was 20 times more efficient compared to the unit flare. Overall, Envent was able to work safely and efficiently while allowing this customer to save on budget and time.

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