LNG (Liquefied Natural Gas)
LNG is Natural Gas which has been cooled to a temperature, around the boiling point of methane (-162ºC), at which it liquefies, thus reducing its volume by a factor of around 600. The exact boiling of any gas mixture and the reduction in volume will depend on its composition. The process of Liquefaction is carried out in a liquefaction plant. Mostly these are very large scale plants built for projects transporting gas by sea, but in many countries small LNG plants have been built to liquefy gas during the seasons of low demand to provide Peak Shaving when required. LNG Plants consist of one or more LNG Trains, each of which is an independent gas liquefaction unit. It is more cost effective to add a train to an existing LNG plant, than to build a new LNG plant, because infrastructure built for early trains, such as ship terminals and other utilities, may be capable of being used or expanded for new LNG trains. The term Train is sometimes extended loosely to embrace the relevant shipping, storage and other facilities required to bring the resultant LNG to market. Liquefied gas is transported and stored as a boiling liquid under slight positive pressure until required for use, when it is warmed and allowed to re-gasify. In the case of Peak Shaving, the gas will normally be regasified at the plant itself or possibly transported for short distances by road, but large scale transportation is by sea, in specially designed insulated LNG vessels and delivered to LNG terminals, which have the requisite facilities for storage and regasification - the process by which LNG is warmed, usually through a heat exchanger, in order to become once more gaseous before emission into the Gas Grid.