Abstract: In an apparatus for the separation of air by cryogenic distillation, all of the air is compressed to a medium pressure. Next, one part of the air is compressed to an intermediate pressure and a fraction of this air is compressed to a high pressure. The high-pressure air is divided into at least two fractions and expanded in two turboexpanders, the cooled stream from the warm turboexpander being at least partially recycled into the warm end of the exchanger at a higher pressure. A liquid coming from the air separation apparatus vaporizes in the exchanger.

Abstract: The air coming from a blowing turbine (13) and intended for the low-pressure column of a double column (2) is cooled by indirect heat exchange with a liquid (15, 20). This liquid is a purge stream from a condenser (5, 6) of the system.

Abstract: A process for liquefying a gas, wherein the gas is compressed, cooled, then expanded in a first turbine and at least partially liquefied, wherein a portion of the liquid produced is also cooled, and then expanded in a second turbine, wherein the second turbine operates with a higher inlet temperature than the first turbine and the first turbine operates at an outlet pressure different than that from the second turbine.

Abstract: In a process for liquid evaporation by heat exchange with a gas which condenses, the pressure of the liquid to be evaporated is reduced and it is enriched in a constituent which has little volatility after evaporation. According to an alternative form, the gas to be condensed can be enriched in the constituent which has little volatility.

Abstract: A process and system for producing an argon-enriched stream comprising a multiple column air separation system, a first crude argon column, and a second crude argon column is provided. The improved process involves removing a vapor stream from the upper portion of the first argon column; reducing the pressure of the vapor in a pressure reducing device; and then flowing the reduced pressure vapor to a second argon column which operates at a lower operating pressure relative to the first argon column.

Abstract: According to this process: the medium pressure column is operated under a pressure which is higher than six bars and is preferably at least equal to about 9 bars absolute; a first vaporization gas which is less volatile than the nitrogen from the top of the medium pressure column is condensed in the vat condenser of the low pressure column; and nitrogen from the top of the medium pressure column is condensed, it is thereafter sent under reflux to the top of the medium pressure column, at a level of the low pressure column located above said vat condenser application to apparatuses for air distillation with double column associated with a gas turbine.

Abstract: According to the process of the invention, after heating, nitrogen which exits from a pressure column is compressed under elevated pressure by means of a single nitrogen compressor, and the low pressure column is operated at a pressure of about P.sub.N /.rho..sub.N, where P.sub.N represents the elevated pressure of nitrogen and .rho..sub.N the compression ratio of the nitrogen compressor. Application to the simultaneous production on the one hand of high purity nitrogen at a pressure between 50 and 60 bars, and on the other hand, of oxygen at 65 bars, so as to supply a unit for the production of ammonia.

Abstract: The apparatus is of the type having a double column and a mixing column. The latter is fed at the bottom portion with auxiliary air that is compressed at a pressure different from that of the mean pressure column, and at the top by means of a liquid withdrawn from the bottom of the low pressure column and pumped at the same pressure as the auxiliary air. Impure oxygen is withdrawn at the top of the mixing column as production gas, and substantially pure oxygen is produced at the bottom of the low pressure column.