Abstract: A first stream of argon-enriched oxygen is separated in a first rectification column to form oxygen vapour further enriched in argon and a second stream of argon-enriched oxygen is introduced into a second rectification column operating at a lower pressure than the first rectification column. A vapour flow upwardly through the second rectification column is created by reboiling in a reboiler-condenser liquid separated therein. The further-enriched oxygen vapour is condensed in the reboiler-condenser by indirect heat exchange with said separated liquid. One stream of the condensed further-enriched oxygen vapour is employed as reflux in the first rectification column. A third argon-enriched oxygen stream is introduced in liquid state into an intermediate mass exchange region of the second rectification column. An argon product is separated in the second rectification column.

Abstract: Air is separated in a higher pressure rectification column into a bottom fraction of oxygen-enriched liquid air and a top fraction of nitrogen. The column has a first inlet for a first vaporous air stream at a first pressure communicating with an expansion turbine. A first condenser-reboiler for condensing a second vaporous air stream at a second pressure greater than the first pressure has an inlet communicating with a compressor. The condensate flows through an expansion valve into the higher pressure rectification column. A stream of oxygen-enriched liquid is withdrawn from the bottom of the column and is introduced into a lower pressure rectification column in which an impure oxygen fraction is separated. A second condenser-reboiler places the top of the higher pressure rectification column in heat exchange relationship with an intermediate region of the column. Reboil for the bottom of the column is provided by the first condenser-reboiler. An impure oxygen product is withdrawn from the column.

Abstract: A stream of precooled and purified air is introduced into a double rectification column comprising a higher pressure rectification column and a lower pressure rectification column and is separated therein into an oxygen-rich fraction and a nitrogen-rich fraction. A stream of argon-enriched oxygen vapor flows from an outlet of the lower pressure rectification column into a side column in which argon is separated therefrom. An oxygen-enriched liquid air stream is taken from an outlet at the bottom of the higher pressure rectification column. A vaporous oxygen-enriched air stream is introduced into the lower pressure rectification column through an inlet above the outlet. At least part of the oxygen-enriched liquid is separated in a further or intermediate pressure rectification column provided with a reboiler, thereby forming a vapor depleted of oxygen and a liquid air stream further enriched in oxygen.

Abstract: An air separation plant and process in which a first stream of compressed feed air is introduced in vapour state into a higher pressure rectification column and separated therein into nitrogen vapour and oxygen-enriched liquid air and a flow of the nitrogen vapour is condensed in condenser-reboiler. A flow of the oxygen-enriched liquid air is separated in a reboiled lower pressure rectification column into nitrogen-rich and oxygen-rich fractions. A first flow of the condensed nitrogen is employed as reflux in the higher pressure rectification column and a second flow of the condensed nitrogen is employed as reflux in the lower pressure rectification column. A flow of compressed feed air is expanded in expansion turbine with the performance of external work so as to create refrigeration for the process. Products of the separation include one or both of a gaseous nitrogen product taken from the higher pressure rectification column and a liquid nitrogen product.

Abstract: A stream of precooled and purified air is introduced into a double rectification column comprising a higher pressure rectification column and a lower pressure rectification column and is separated therein into an oxygen-rich fraction and a nitrogen-rich fraction. A stream of argon-enriched oxygen vapour flows from the lower pressure rectification column into a side column in which argon is separated therefrom. An oxygen-enriched liquid air stream is taken from the bottom of the higher pressure rectification column. A vaporous oxygen-enriched air stream is introduced into the lower pressure rectification column above the point at which argon-enriched oxygen vapour is removed. At least part of the oxygen-enriched liquid is partially reboiled in a reboiler and is separated in a further rectification column, thereby to form a vapour depleted of oxygen and a liquid air stream further enriched in oxygen.

Abstract: Air is compressed in a compressor, purified in a purification unit, cooled by passage through a main heat exchanger and separated in a double rectification column comprising a higher pressure rectification column and a lower pressure rectification column. A stream of argon-enriched oxygen vapour is withdrawn from the lower pressure rectification column through an outlet and an argon product is separated from it in an argon rectification column provided with an argon condenser. Argon is condensed in the condenser by indirect heat exchange with a second stream of air at a pressure between the operating pressures of the columns. The second air stream is partially condensed and passed into a phase separator. A stream of liquid phase is withdrawn from the phase separator, is passed through a throttling valve and the condenser, in sequence. Further cooling for the condenser is thus provided.

Abstract: Air is compressed in compressors, cooled in a main heat exchanger, and separated into oxygen and nitrogen products in a double rectification column comprising a higher pressure rectification column and a lower pressure rectification column. A liquid oxygen product is withdrawn from the lower pressure column via a conduit. A liquid nitrogen product is also formed. An argon-enriched oxygen vapour stream is withdrawn from the lower pressure column through an outlet and has argon separated from it in an argon column. In order to help meet the requirements of the higher pressure column for reflux, a nitrogen vapour stream is withdrawn from the top of the lower pressure column, is warmed by passage through the heat exchanger, is recompressed in a compressor, and is liquefied by passage back through the heat exchanger from its warm end to its cold end and passage through a valve. A high liquid make and a high argon recovery can both be achieved.

Abstract: An air separation method and apparatus in which a stream of air is compressed in a compressor and purified in a unit. One stream of the resulting air is cooled in a heat exchanger and is separated in an arrangement of rectification columns comprising a higher pressure rectification column, a lower pressure rectification column, and a further rectification column for separating argon from an argon-enriched oxygen stream withdrawn from the lower pressure rectification column and the stream of resulting air is introduced into the higher pressure rectification column through an inlet. A second cooled, compressed, purified air stream is expanded in an expansion turbine and is introduced into the lower pressure rectification column. A third cooled, compressed, purified air stream is expanded in a second expansion turbine and is introduced into the higher pressure rectification column.

Abstract: Nitrogen is separated from a first stream of compressed air in a higher pressure rectification column and from a second stream of compressed air in an intermediate pressure rectification column. Oxygen-enriched liquid is taken from the columns and separated in a lower pressure rectification column. An impure oxygen product is withdrawn in liquid state from the lower pressure column through an outlet. A part of the first air stream is condensed in a first condenser-reboiler, and a part of the second air stream is condensed in a third condenser-reboiler. Nitrogen separated in the higher pressure rectification column is condensed in a second condenser-reboiler, and nitrogen separated in the intermediate pressure rectification column is condensed in a fourth condenser-reboiler. The resulting nitrogen condensate is used as reflux in the columns. The condenser-reboilers provide reboil for the lower pressure rectification column.