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n the Asia Pacific region, LNG is transferred by specialised LNG vessels with cryogenic tanks intended for long-distance transportation. A significant fraction of the cargo LNG volume evaporates during the voyage as boil-off gas (BOG), particularly during spray operation. It is challenging to use generated BOG for LNG vessel operation efficiently, and especially to minimise (optimise) the LNG heel stock during a ballast voyage. These LNG vessels can increase both fuel efficiency and delivery capacity by optimising spray schedules for storage tanks. The article’s authors developed a dynamic simulation system to estimate LNG heel stock in the LNG cargo tanks of a Moss LNG cargo containment system, thus determining the required minimum LNG heel stock for a ballast voyage. The simulation model, built in CHEMCAD NXT, considers the effect of several process factors such as LNG compositions, ambient temperature, pressure, sloshing factor (ship motion), spray operation schedule, and LNG vessel voyage plan. Based on the dynamic simulation, the optimum LNG heel stock can be determined for long-distance LNG transportation. The dynamic simulation model can be applied for: � LNG ballast handling (including spray schedule) during the voyage. �
Thermo-economical voyage simulation of marine energy systems of LNG vessels.
Kenichi Matsuoka, Azbil Corp., Japan, Daichi Watanabe, MTI Co., Ltd, Japan, and David Hill, Carla Lara, and Aaron Herrick, Chemstations, USA, detail the development of LNG cargo tank simulation technology for ballast voyage. 41
