A system and method for producing two or more nitrogen product streams and a crude argon stream from a nitrogen and argon producing air separation unit is provided. The disclosed embodiments of the cryogenic-based nitrogen and argon producing air separation units and associated air separation cycles include the means for directing a first portion of a boil-off stream from an argon condenser of the air separation unit to a waste expansion refrigeration circuit and concurrently recycling a second portion of the boil-off stream from the argon condenser to the main air compression system of the air separation unit to be mixed or blended with the incoming feed air. Optionally, a third portion of the boil-off stream from the argon condenser may be further compressed in a cold compressor and returned to the lower pressure column.

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.

Process and apparatus for the separation of a compressed feed air stream to produce an oxygen product using a distillation column having a lower-pressure column and a higher-pressure column, a higher-pressure heat exchanger and a lower-pressure heat exchanger where the gaseous nitrogen expander receives a nitrogen-enriched fraction from a position intermediate the warmer end and the colder end of the higher-pressure heat exchanger.

An air separation unit and associated method for separating air by cryogenic distillation using a distillation column system including a higher pressure column, a lower pressure column, an intermediate pressure kettle column, and an argon column arrangement is provided. The disclosed air separation unit and method is particularly suited for production of high purity nitrogen for electronics applications and includes nitrogen recycle circuit necessary to attain the higher purity nitrogen products. In addition to the intermediate pressure kettle column, the present air separation unit and associated method employs a once-through argon condenser, preferably disposed within the lower pressure column as well as a once-through kettle column reboiler, a once-through kettle column condenser.

Process and apparatus for producing pressurized gaseous nitrogen by cryogenic separation of air. The distillation column system includes a high pressure column, a medium pressure column, a main condenser and top condenser both being condenser-evaporators. Compressed and purified feed air is cooled in a heat exchanger and introduced to the distillation system. A gaseous nitrogen stream from the high pressure column is condensed in the main condenser. Bottom liquid of the medium pressure column is evaporated and gaseous nitrogen from the medium pressure column is condensed in the top condenser. Liquid nitrogen from the medium pressure column is pressurized and introduced to the high pressure column. A second gaseous nitrogen stream from the high pressure column is recovered as pressurized gaseous nitrogen product. A portion of the compressed and purified feed air is work-expanded and then warmed in the main heat exchanger.

Gas processing plants and methods are contemplated in CO.sub.2 is effectively removed to very low levels from a feed gas to an NRU unit by adding a physical solvent unit that uses waste nitrogen produced by the NRU as stripping gas to produce an ultra-lean solvent, which is then used to treat the feed gas to the NRU unit. Most preferably, the physical solvent unit includes a flash unit and stripper column to produce the ultra-lean solvent.

An apparatus for producing product nitrogen gas and product argon, comprising: a first rectification column into which raw air is introduced; a second rectification column from which product nitrogen gas is drawn; a third rectification column from which product argon gas is drawn; and a first condenser configured to perform heat exchange between a gas accumulated in a column top portion of the first rectification column, and a liquid accumulated in a column bottom portion of the second rectification column, wherein an intermediate portion gas containing nitrogen is drawn from an intermediate portion of the second rectification column and merged with a condenser gas drawn from the first condenser. The merged gases are expanded and cooled by means of an expansion turbine whereby the cold thereof is utilized.

A method and apparatus for producing high-purity nitrogen and low-purity oxygen using three-column rectification are provided, in which: nitrogen and oxygen undergo rectification in different columns, with high-purity nitrogen and low-purity oxygen being separated out of air simultaneously, thereby overcoming the shortcomings of conventional low-purity oxygen production equipment, and also reducing equipment investment, lowering energy consumption, increasing product added value, and realizing a circular economy effect.

A system and method for cooling an oxygen stream by heat exchange with a warming supply nitrogen stream having of a heat exchanger having at least a Zone A and a Zone B, the system having indirect heat exchange between a gaseous oxygen stream, and a high-pressure liquid nitrogen stream split into at least a first portion which passes through a Zone A, and a second portion which passes through a Zone B during a first phase of operation. And a high-pressure liquid nitrogen stream passing through Zone A, thereby producing a high-pressure nitrogen vapor stream, which passes through an expansion turbine, thereby producing an expansion turbine outlet stream which then passes through Zone B, during a second phase of operation, thereby producing a liquid oxygen stream.