Producing and liquefying

An export terminal is mostly not a refrigerator. Before gas can be liquefied it has to be stripped of carbon dioxide, water, mercury, sulphur compounds and the heavier hydrocarbons, because every one of them freezes solid or attacks the metal at cryogenic temperature. The treatment section is frequently larger than the liquefaction section, and its size depends entirely on what came out of the ground.

The cold end is where the engineering concentrates. Several companies will license a refrigeration process, and the thermodynamics are in textbooks, but the ability to fabricate the object at the centre of a large train — a tower holding many kilometres of wound tubing, built to tolerances that survive decades of thermal cycling — sits with very few manufacturers.

This track follows gas from the wellhead to the loading jetty, and explains why plant capacity is quoted as a nameplate figure that real output routinely misses in both directions.