LIQUEFIED NATURAL GAS STORAGE OF VARIABLE COMPOSITION

Thanks to the increasing diversification of LNG supply sources, being a result of the growing number of LNG liquefaction installations over the World, increase of short-term trade contracts and general trend to globally liberalize gas markets, reception terminals have to cope with the broad range of qualitatively diversified LNG deliveries from various sources. Different LNG deliveries potentially have different density caused by different gas composition. Although the LNG composition depends on LNG source, it mainly consists of methane, ethane, propane, butane and trace nitrogen. When a new supply of LNG is transported to the tank, the LNG composition and temperature in the tank can be different from LNG as delivered. This may lead to the liquid stratification in the tank, and consequently the rollover. As a result, LNG rapidly evaporates and the pressure in the tank increases. More and more restrictive safety regulations require fuller understanding of the formation and evolution of layers. The paper is focused on the analysis of liquid stratification in the tank which may take place when storing LNG, and which process leads to the rapid evaporation of considerable quantities of LNG. The aim was to attempt modeling of the process of liquid stratification in an LNG tank. The paper is closed with the results of modelling.