(110c) Recent Developments in the Prediction and Optimization of the Mixing of Different Qualities of Lng in a Storage Tank

Today's LNG industry is faced with an ever increasing diversification of LNG supply sources, caused by the progressive worldwide deregulation of gas markets, by a steady increase in the number of liquefaction plants fueled by an increasing gas demand and by the emergence of new shorter term type supply contracts. This has lead to a growth in worldwide LNG trade as well as a multiplication of the different LNG qualities which can be exchanged.

Therefore, import terminals are often faced with the need to handle different LNG qualities concurrently in the same storage tanks. This can impose constraints on the operation of a terminal, such as production of high boiloff rates during tank filling operations. This can also increase the risk of creating stratifications resulting from the incomplete mixing of cargo and heel LNGs.

It is within this context, and as a response to the above mentioned trends, that Gaz de France, in collaboration with other companies, has carried out research which help its operators to be better prepared in dealing with the emerging challenges they are faced with. In particular, efficient mixing of different LNG qualities in a same tank was investigated through comprehensive pilot scale experimental campaigns carried out on the Nantes LNG testing station. As a result of this work, a new dynamic tank filling model, predicting the formation or not of an LNG stratification and taking into account various commonly used industrial filling devices, was developed.

This paper will highlight the research which was carried out and will present the newest version of Gaz de France's LNG tank management software named LNG MASTER, including some of the operational validation data which was used to develop this version of the software.