A Study on the Sloshing Risk Reduction in Membrane-type LNG Tanks by Interchanging Liquid Cargo between Tanks

Floating Liquefied Natural Gas Production, Storage and Offloading Unit (FLNG) and Floating Storage and Regasification Unit (FSRU) have appeared in the offshore LNG chain recently. Large scale membrane tanks are expected to be used in some such facilities; however, special attention should be paid to half-loading in the membrane tanks because of the risk of sloshing. A distribution control method by which LNG is distributed and interchanged between the tanks to reduce the sloshing risk was proposed by Yokohama National University. In this operation, the sloshing risk is reduced by shortening the period spent in the half-load condition as much as possible. In this study, the operation was optimized using a genetic algorithm. Several cases involving different charging operations were examined, and the flexibility of this method was demonstrated. It was shown that a considerable decrease of the sloshing risk is achieved.