Process and apparatus for air separation by cryogenic distillation

An air separation process by cryogenic distillation comprising the steps of:

• i) drying an air flow (1), purifying the air flow of CO2, cooling the air flow in a heat exchanger, and separating the air flow in a column system to form at least a fluid enriched in oxygen relative to air and at least one fluid enriched in nitrogen relative to air, wherein the column system (2, 4, 50) comprises at least one distillation column operating at a cryogenic temperature;
• ii) heating the at least one fluid enriched in oxygen or nitrogen in the heat exchanger;
• and
• iii) supplying at least part of the cold necessary for the process by expansion in at least one turbine (92, 102) of a gas (5, 55) containing at least 95% mol oxygen at a pressure of at least 2 bars which comes from an external source, wherein the gas is first cooled to at least an intermediate temperature of the heat exchanger, then expanded in the at least one turbine, and then reheated in the heat exchanger.

An air separation apparatus using cryogenic distillation, the air separation apparatus comprising:

• a heat exchanger (2);
• a column system (2, 4) comprising at least one distillation column configured to operate at a cryogenic temperature;
• a first conduit configured to send an air flow (1) to be cooled in the heat exchanger (2);
• a second conduit (L1) configured to send the air flow from the heat exchanger to the column system for separation therein, wherein the column system is configured to separate the air flow into an oxygen enriched fluid and a nitrogen enriched in fluid;
• a third conduit (L31, L43) configured to send the oxygen enriched fluid or nitrogen enriched fluid to be warmed in the heat exchanger;
• at least one turbine (92, 102);
• a fourth conduit configured to send a gas (5) containing at least 95% oxygen at a pressure of at least 2 bars originally sourced from an external source to the heat exchanger for cooling to an intermediate temperature of the heat exchanger;
• a fifth conduit in fluid communication with an intermediate section of the heat exchanger and an inlet of the at least one turbine, wherein the fifth conduit is configured to send the gas at the intermediate temperature to the at least one turbine to be expanded;
• and
• a sixth conduit configured to send the gas from an outlet of the at least one turbine to a cold end of the heat exchanger for warming therein.