LNG BOG management systems

The StirLNG line of products is a range of SPC Cryogenerators that has specifically been modified for small (micro) scale Boil Off Gas Management by gas re-liquefaction or liquid subcooling. Each unit operates stand-alone, is driven by an electrical motor and has its own control unit. The StirLNG line offers BOG management in two different principles.

Gas re-liquefaction
Boil-off gas is taken from a storage tank, re-liquefied by the StirLNG and transferred back into the storage tank. This can be done by gravity or by using a separate transfer vessel.

Methane feed gas specifications needed:

• Main stream CH₄
• CxHy (C2 to C4) < 10%
• CxHy (C5+) < 1 ppm
• CO₂ depending LNG conditions
• H₂O < -70ºC dew point
• H₂S < 3,3 ppm
• Oil content < 0,01 mg/m3
• Particles < 0,1 micron
• N2/O₂ < 10%

Liquid subcooling
LNG is pumped from the bottom of an LNG storage tank to the StirLNG, subcooled to a temperature below the liquefaction temperature and sprayed back in the top of the storage tank thus re-liquefying the BOG.

The required cooling capacity for a storage tank can be achieved by installing StirLNG machines in parallel. The modular design of the StirLNG machine gives a project operational flexibility and the needed redundancy. With a short ramp up time (in 10 minutes from +20C to -162C) and no electricity consumption when not in operation the StirLNG units are a perfect match for any BOG management challenge, whether it concerns continuous or intermitted operations.

The output of the StirLNG units (depending on BOG composition and pressure) ranges from 10,5 kg to 700 kg per hour and everything in between.

StirLNG Maritime
Within the StirLNG product range special attention goes to the StirLNG-4 Maritime. This unit has been modified for maritime conditions:

To ensure the free directional positioning on a ship and the functionality of the units the lubrication system and LNG outlets of the StirLNG-4 Maritime are adapted for 22,5° dynamic roll and pitching, as well as stating tilting up to 15° in each direction during (un)loading.

The units are equipped with maritime vibrations dampeners and are painted with a corrosion preventive paint according to the required regulations BV, ABS or other for inland waterways or seagoing vessels.

Product specification:
StirLNG-1 Cryogenerator
StirLNG-4 Cryogenerator
StirLNG-4 Cryogenerator Maritime

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References