A thermal and thermodynamic code for the computation of Boil-Off Gas – Industrial applications of LNG carrier

Abstract

This paper describes the numerical method implemented in Gaztransport & Technigaz specific-purpose thermal and thermodynamic code for complex physical phenomena in Liquefied Natural Gas (LNG) carrier tanks. The code is zero-dimensional and is used for LNG industrial applications and research activities in several fields related to Boil-off Gas (generation, consumption, optimization, etc.).The set of equations considered consists of the LNG and NG mass and energy conservation equations completed with equation of state and equations for LNG aging modeling. An explicit time-marching scheme with multiple-order methods is used. Specific effort has been put into the fast computation of the thermodynamic and transport properties of LNG. The implemented physical approaches have been validated by operational data.Better management of Boil-off represents a significant operational challenge for players in the LNG chain. Industrial applications illustrate important aspects of physical modeling such as saturation properties, thermal layer and sloshing. These examples also demonstrate the capability of the code to tackle a large variety of LNG carrier operating conditions and tank geometries.