A process comprises a first set of distillation columns and a second set of distillation columns, a low-pressure column of the first set being connected to a column operating at higher pressure of the second set by means of a gas arriving from the top of the column operating at a higher pressure and/or by means of a fluid arriving from the low-pressure column.

A moderate pressure, argon and nitrogen producing cryogenic air separation unit and air separation cycle having a higher pressure column, a lower pressure column and an argon column arrangement is disclosed. The moderate pressure, argon and nitrogen producing cryogenic air separation unit is configured to take a first portion of an oxygen enriched stream from the lower pressure column, which together with an external source of liquid nitrogen is used as the boiling side refrigerant to condense the argon in the argon condenser. Use of the external source of liquid nitrogen in the argon condenser allows a second portion of the oxygen enriched stream from the lower pressure column to be taken as a liquid oxygen product stream.

A moderate pressure nitrogen and argon producing cryogenic air separation unit is provided that includes a three distillation column system and turbine air stream bypass arrangement or circuit. The turbine air stream bypass arrangement or circuit is configured to improve argon and nitrogen recoveries in select operating modes by optionally diverting a portion of the turbine air stream to a nitrogen waste stream circuit drawn from the lower pressure column of the cryogenic air separation unit such that the diverted portion of the turbine air stream bypasses the distillation column system.

An air separation unit comprises: a first waste gas control valve which is provided in a first waste gas pipe; a first waste gas flow rate control unit which measures a gas flow rate in the first waste gas pipe and adjusts a degree of opening of the first waste gas control valve so that a measured value which has been measured reaches a preset first waste gas flow rate set value; a second waste gas control valve which is provided in a second waste gas pipe; a regeneration gas flow rate control unit which measures the gas flow rate in a regeneration gas pipe and outputs a first output value based on a measured value which has been measured and a preset regeneration gas flow rate set value; and a control unit which uses, as a target set value of the flow rate of a second waste gas, a value obtained by subtracting the first waste gas flow rate set value of the first flow rate measuring unit from the flow rate set value of the regeneration gas flow rate, compares the first output value with a second output value based on a value obtained by subtracting the measured value of the first flow rate control unit from the measured value of the regeneration gas flow rate control unit, controls the degree of opening of the second waste gas control valve on the basis of the lower of the values, and adjusts the second waste gas flow rate.

A moderate pressure air separation unit and air separation cycle is disclosed that provides for up to about 96% recovery of argon, an overall nitrogen recovery of 98 percent or greater and limited gaseous oxygen production. The air separation is configured to produce a first high purity oxygen enriched stream and a second lower purity oxygen enriched stream from the lower pressure column, one of which is used as the refrigerant to condense the argon in the argon condenser, with the resulting vaporized oxygen stream used to regenerate the temperature swing adsorption pre-purifier unit. All or a portion of the first high purity oxygen enriched stream is vaporized in the main heat exchanger to produce the gaseous oxygen products.

A moderate pressure air separation unit and air separation cycle is disclosed that provides for up to about 96% recovery of argon, an overall nitrogen recovery of 98 percent or greater and limited gaseous oxygen production. The air separation is configured to produce a first high purity oxygen enriched stream and a second lower purity oxygen enriched stream from the lower pressure column, one of which is used as the refrigerant to condense the argon in the argon condenser, with the resulting vaporized oxygen stream used to regenerate the temperature swing adsorption pre-purifier unit. All or a portion of the first high purity oxygen enriched stream is vaporized in the main heat exchanger to produce the gaseous oxygen products.

A moderate pressure air separation unit and air separation cycle is disclosed that provides for up to about 96% recovery of argon, an overall nitrogen recovery of 98% or greater and limited gaseous oxygen production. The air separation is configured to produce a first high purity oxygen enriched stream and a second lower purity oxygen enriched stream from the lower pressure column, one of which is used as the refrigerant to condense the argon in the argon condenser, with the resulting vaporized oxygen stream used to regenerate the temperature swing adsorption pre-purifier unit. All or a portion of the first high purity oxygen enriched stream is vaporized in the main heat exchanger to produce the gaseous oxygen products.

A moderate pressure air separation unit and air separation cycle is disclosed that provides for up to about 96% recovery of argon and an overall nitrogen recovery of 98% or greater. The air separation is configured to produce a high purity oxygen enriched stream which is used as the refrigerant to condense the argon in the argon condenser, with the resulting vaporized oxygen stream used to regenerate the temperature swing adsorption prepurifier unit. Argon recovery is facilitated with the use of an argon superstaged column.

The method and the device arc used for the cryogenic decomposition of air in a distillation column system for separating nitrogen and oxygen, said system having a first high-pressure column (23), a low-pressure column (25, 26), and three condenser-evaporators, namely a high-pressure column head condenser (27), a low-pressure column bottom evaporator (28), and an auxiliary condenser (29; 228).

The plant is used for producing oxygen by cryogenic air separation. The plant has a high-pressure column, a low-pressure column and a main condenser. An argon-elimination column is in fluid connection with an intermediate point of the low-pressure column and is connected to an argon-elimination column head condenser. An auxiliary column has a sump region, into which gas is introduced from the argon-elimination column head condenser. The head of the auxiliary column is connected to a return flow liquid line, in order to introduce a liquid stream from the high-pressure column or the head condenser. The liquid stream has an oxygen content which is at least equal to that of air. At least one part of the crude liquid oxygen from the sump of the high-pressure column is fed to the auxiliary column at a first intermediate point.