Degassing of an LNG-powered Freight Vessel

Degassing of an LNG-powered Freight Vessel

Portfolio Categories: Degassing and Vapor Control.

Envent Corporation | Marine Vapor Degassing


A customer has tasked Envent to create a temporary system allowing for the degassing of an LNG-powered freight vessel while it docks in port to remove cargo. The solution would allow the customer to continue standard operations without delay, clear unwanted vapors from within the fuel tanks, and maintain compliance with Environmental Protection Agency regulations.


Envent supplied the customer with an EMECS 70, the industry leading mobile thermal oxidizer unit, as well as cryogenic-rated SS hose, a knockout drum, and a high-pressure regulator. The freighter has two 900 m3 LNG tanks each containing trace amounts of liquid LNG and pressurized vapors. The process stream was routed through the cryogenic-rated SS hose down to the knockout drum allowing for the vaporization of LNG to a gaseous state while simultaneously increasing its temperature from subzero to suitable levels. Fire water was run past the knockout drum in order to aid with the heat exchange. Vapors were then routed to the thermal oxidizer at a control pressure and incinerated to greater than 99.9% efficiency at a rate of 60,000 CFH. This process continued until both LNG vessels were completely depressured.


Envent’s depressure solution allowed for the customer to successfully continue operations without having to delay any standard procedures. In addition, the customer was able to start maintenance work on both LNG tanks immediately after this process was completed. Both of these achievements allowed the customer to save a valuable amount of time and money.


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