Process and installation for the production of gaseous oxygen under high pressure

A process for producing a gas at a high pressure of at least 30 bars, using an air distillation unit (1) comprising a low pressure column (11) and a medium pressure column (10) where fractions of the air are delivered to the columns at different pressures after cooling, comprises dividing the air to be distillated into three streams: (i) a first medium pressure stream cooled to its dew point and delivered in the medium pressure column; (ii) a high pressure stream above at least 60 bars, being cooled and liquified (in 17), and after expansion (in 18), delivered in the double column (1); and (iii) an intermediate pressure stream, at least part of that stream being at an intermediate cooling temperature, expanded to medium pressure in a turbine (6) before being directed to the medium pressure column (10). The intermediate pressure is chosen such that the air is near its dew point before entering the turbine. Also claimed is apparatus for producing purified and pressurised gas.