LNG

Liquefied Natural Gas (LNG)

When chilled to very cold temperatures, approximately - 162°C, natural gas changes into a liquid and becomes liquefied natural gas (LNG). The liquefaction process also removes the oxygen, carbon dioxide, sulphur compounds, and water. The process can also be designed to purify the LNG to almost 100% methane.

In its liquid form, gas can be stored much more economically. LNG can also be loaded on to tankers (large ships with several domed tanks) and moved across the ocean to deliver gas to other countries. Once in this form, it takes up only 1/600th of the space that it would in its gaseous state.

LNG weighs less than one half of water, actually about 45% as much. LNG is odourless, colourless, non-corrosive, and non-toxic. When vaporised it burns only in concentrations of 5% to 15% when mixed with air. Neither LNG, nor its vapour, can explode in an unconfined environment.

LNG storage tanks are always of double-wall construction with extremely efficient insulation between the walls. Large tanks are low aspect ratio (height to width) and cylindrical in design with a domed roof. Storage pressures in these tanks are very low, less than 5 puonds per square inch gauge ("psig"). Smaller quantities, 70,000 gallons and less, are stored in horizontal or vertical, vacuum-jacketed, pressure vessels.
These tanks may be at pressures anywhere from less than 5 psig to over 250 psig. LNG must be maintained cold (at least below -117°C) to remain a liquid.