Method And Apparatus For The Production Of Gas From Air In Highly Flexible Gaseous And Liquid Form By Cryogenic Distillation

A method of producing at least one air gas using cryogenic distillation in a system of columns comprising at least one medium-pressure column operating at a medium pressure and a low-pressure column operating at a low pressure, said at least one medium-pressure column and low-pressure column being thermally coupled to one another, comprising, in a first and a second operating mode:

• a) raising a compressed air stream to a high pressure, at least 5 bar above the pressure of the medium-pressure column, and purifying said air stream at this high pressure,
• b) varying said high pressure according to the demand for said at least one air gas;
• c) cooling a first part of the air stream in a heat exchange line to an intermediate temperature, and expanding said cooled first part in at least a first turbine;
• d) compressing at least a fraction of the air stream to a higher pressure in a supercharger, wherein said higher pressure is greater than or equal to the high pressure, cooling said higher pressure air stream n the heat exchange line down to a temperature less than or equal to −100° C., and returning the supercharged stream to the heat exchange line in which at least part becomes liquefied at the cold end and is then sent into the system of columns following expansion;
• e) vaporizing a pressurized liquid product from the system of columns in the heat exchange line;
• and
• in the first operating mode:
• f) admitting a gaseous fraction of the air stream into an auxiliary turbine, said fraction having been cooled in the main heat exchange line;
• g) expanding at least part of the air stream rate in the auxiliary turbine, warming said expanded stream in the heat exchange;
• and
• in the second operating mode:
• h) reducing the flow rate of the air stream processed in the auxiliary turbine, by comparison with the stream processed in the auxiliary turbine in the first mode;
• and
• i) decreasing the production of liquid by way of end product by comparison with the production of liquid by way of end product in the first mode.

A unit for cooling and heating streams intended for and coming from a system of air separation columns comprising a heat exchange line, a first turbine, an auxiliary turbine, a supercharger, the heat exchange line comprising:

• i) at least one passage for receiving a first purified air stream, the at least one passage for receiving a first purified air stream being connected to the supercharger,
• ii) at least one passage connected to the delivery of the supercharger, the at least one passage connected to the supercharger being connected to the first turbine,
• iii) at least two passages for receiving at least two fluids (35, 37) which become heated,
• iv) at least one passage to receive a second purified air flow rate, the at least one passage for receiving the second purified air stream being connected to the admission of the auxiliary turbine and the delivery of the auxiliary turbine being connected to at least one passage for air to be heated.