Process and liquefier for the production of liquid air

A liquefier system for producing liquid air comprising a purifying station, at least one compressor, at least one device for engine expansion of process gas, and a rectification column comprising separating stages installed in the rectification column, a head cooling unit and a bottoms heating unit, wherein the bottoms heating comprises an electric heater or heating tubes, and wherein the number of separating stages in the column corresponds to less than four theoretical plates, and wherein the purifying station comprises reversible molecular sieve adsorbers, with conduit for introducing process gas to be purified into at least one adsorber and for introducing into at least one other adsorber regeneration gas or purge gas, whereby residual gas from the liquefier can be used as a regeneration gas or purge gas.

In a process for the production of liquid air with an oxygen content of between 16 and 21 mol % in a low-temperature process, comprising purifying atmospheric air to remove H2O, carbon dioxide and contaminants entrained in the air;

• producing cold values by compression and engine expansion of at least one process stream, and obtaining the liquid air in a cold part of the process by low-temperature rectification, the improvement comprising conducting said low-temperature rectification in a rectification column having less than four theoretical plates, withdrawing a purified liquid air head product from the rectification column, withdrawing a liquid bottoms stream from the rectification column, vaporizing the liquid bottoms stream in indirect heat exchange with air to be cooled prior to being fed to the rectification column, and venting resultant warm residual gas into the atmosphere or passing said resultant warm residual gas at least partially to the purifying step, further comprising mixing atmospheric air with a gas stream withdrawn from the cold part of the process and then heated, and compressing the resulting warm mixed feed to a starting pressure for engine expansion and then purifying said compressed gas.