Flexible and cost-effective optimization of BOG (boil-off gas) recondensation process at LNG receiving terminals

Abstract

In view of high energy consumption and poor flexibility in boil-off gas (BOG) recondensation operation at liquefied natural gas (LNG) terminals, a flexible and cost-effective optimization including the control system and flow process has been proposed. The optimized control system maintains BOG recondenser pressure via the condensing LNG flow and recondenser liquid level via bypass LNG flow. A BOG recondensation process with pre-cooling operation utilizes high-pressure pump LNG to pre-cool compressed BOG before it is directed into recondenser. The engineering application in a case of 6.69tons/hour (t/h) BOG and LNG output fluctuating between 49t/h and 562t/h shows, after the flexible and cost-effective optimization, that process energy decreases 91.2kW, more 1.28t/h BOG is recovered when LNG output load reaches the valley, and the operation stability is well improved.