Cooling and liquefying pure gases requires a large amount of energy.
Air separation units (ASUs) separate pure gases from air by cooling the air until it liquefies, then selectively distill the components at their various boiling temperatures.
All of the cold process equipment has to be kept within an insulated cold box enclosure that contains the cryogenic heat exchangers, distillation columns and associated valves and piping.
The cryogenic separation process requires very tight control integration between the heat exchangers and separation columns to obtain good efficiency. To achieve the ultra low distillation temperatures, an ASU requires a refrigeration cycle that operates by means of the Joule–Thomson effect. The cooling and separation of the high purity gases requires a large amount energy for the refrigeration cycle to work effectively.
