As a fuel for ship propulsion, liquefied natural gas (LNG) is currently considered a proven and reasonable solution for meeting the IMO emission regulations, with gas engines for the LNG-fueled ship covering a broad range of power outputs. For an LNG-fueled ship, the LNG bunkering process is different from the HFO bunkering process, in the sense that the cryogenic liquid transfer generates a considerable amount of boil-off gas (BOG). This study investigated the effect of the temperature difference on boil-off gas (BOG) production during ship-to-ship (STS) LNG bunkering to the receiving tank of the LNG-fueled ship. A concept design was resumed for the cargo/fuel tanks in the LNG bunkering vessel and the receiving vessel, as well as for LNG handling systems. Subsequently, the storage tank capacities of the LNG were 4,500 m3 for the bunkering vessel and 700 m3 for the receiving vessel. Process dynamic simulations by Aspen HYSYS were performed under several bunkering scenarios, which demonstrated that the boil-off gas and resulting pressure buildup in the receiving vessel were mainly determined by the temperature difference between bunkering and the receiving tank, pressure of the receiving tank, and amount of remaining LNG.

Abstract
 1. Introduction
 2. Modeling of Bunkering System
  2.1 Bunkering Timeline
  2.2 Tank geometry
  2.3 Determination of LNG flow rate
  2.4 Bunkering Process
 3. Transient Simulation
 4. Results
  4.1 Transient BOG variation
  4.2 BOG return
  4.3 Variations of supply and receiver tank pressure
  4.4 Total LNG bunkering amount
 5. Conclusion
 References

• Yude Shao(Graduate School, Korea Maritime and Ocean University)
• Yoon-Hyeok Lee(Graduate School, Korea Maritime and Ocean University)
• You-Taek Kim(Division of Marine System Engineering, Korea Maritime and Ocean University)
• Ho-Keun Kang(Division of Marine System Engineering, Korea Maritime and Ocean University) Corresponding Author