(116c) Boil-off-Free LNG Transfer Between Floating and On-Shore LNG Storage Tanks

The transfer of LNG from one tank to another tank is conducted by pumping at a discharge pressure of around 5 barg. The LNG in the tank is contained at a temperature around the boiling point stabilized by a continuous LNG boil-off to maintain vapor liquid equilibrium. Pumping the LNG at the discharge pressure increases the enthalpy of the LNG at the pump exit and during the isenthalpic expansion process inside the loading arm the LNG becomes a boiling two-phase fluid due to partial vaporization. The LNG vapor inside the pipe of the loading arm reduces the cross section of the pipe for liquid flow and substantially increases the flow velocity and the friction due to two-phase fluid flow. As a result and following the Bernoulli Equation, for a given differential pressure the mass flow will be reduced substantially.The reduction of the mass flow reduces the LNG transfer rate and increases the overall transfer time for a given quantity of LNG transfer.  Also the vapor return line size will be reduced to a great extent. The paper presents a methodology and equipment to minimize or to eliminate this undesired LNG boil-off within the loading arm. It allows tight LNG flow inside inside loading arm which significantly shortens the LNG transfer time compared to current conventional methods.