(248b) Bog Management during Cargo Unloading at the LNG Regasification Terminal

Unloading of LNG cargo from carrier ship to the terminal tank involves passing through loading/discharge arms, jetty lines, rundown lines, and storage tank vertical risers. These lengths are typically made up from several hundred meters to few kilometers and cause inevitable heat leak to the LNG cargo that results in BOG generation. A trade-off exists between unloading flowrate and BOG generated, a higher unloading flowrate delivers the cargo in shorter period results in less demurrage cost. However, a higher unloading flowrate needed a high pumping cost moreover the unloading line temperature also becomes smaller results in a higher ambient heat leak that produces higher BOG. Thus, with the help of a dynamics simulation model of the LNG receiving terminal, a parcel size of 260,000 m³ is considered for unloading. The study investigated all the ambient factors for devising an optimal unloading strategy. It was mainly found that the storage tank pressure provides the foremost opportunity for optimizing the unloading process that helps best manage the produced BOG.