Method for separating air by cryogenic distillation, wherein at least part of the air to be distilled is boosted in an air booster, compressed air is allowed to expand in at least one expansion turbine and, if the pressure drop between two points of the booster passes under a threshold and/or a flow of the booster passes under a minimum flow of the booster, part of the air boosted in the booster is allowed to expand without having been cooled between the booster and the expansion turbine and the boosted expanded air is sent upstream or downstream of the at least one turbine, without having been cooled in the heat exchanger, after having been boosted.

Method for separating air by cryogenic distillation, wherein air is compressed in a compressor and is subsequently sent to a heat exchanger, with the air cooled in the exchanger being sent to a check valve downstream of the heat exchanger and subsequently to a turbine, the valve being positioned so that air from a short-circuiting duct cannot return to the exchanger from the compressor.

A cryogenic air separation method and apparatus in which first and second liquid streams are produced. The first liquid stream has a higher oxygen content than air and can consist of a higher pressure distillation column bottoms and the second liquid stream, for instance, air, has a lower oxygen content than the first liquid stream and an argon content no less than the air. The second liquid stream is subcooled through indirect heat exchange with the first liquid stream and both of such streams are introduced into the lower pressure column. The second liquid stream is introduced into the lower pressure column above that point at which the crude liquid oxygen column bottoms or any portion thereof is introduced into the lower pressure column to increase a liquid to vapor ratio below the introduction of the second liquid stream and therefore, reduce the oxygen present within the column overhead.

An apparatus for separation of air by cryogenic distillation comprising: a system of columns; a first turbine; a warm compressor coupled to the first turbine; a second turbine; a cold compressor coupled to the second turbine; a heat exchanger; means for sending air cooled in the heat exchanger at an intermediate temperature of the heat exchanger to the cold compressor; means for sending expanded air from the second turbine to the system of columns; means for sending air compressed in the cold compressor to an intermediate point of the heat exchanger and then at least in part to the system of columns via a first valve; means for sending air compressed in the cold compressor to the inlet of the first turbine via a second valve without passing through the heat exchanger, wherein the means for sending air compressed in the cold compressor to the inlet of the first turbine via the second valve without passing through the heat exchanger is also connected to the inlet of the first turbine; means for sending a fraction of air cooled in the heat exchanger to an intermediate temperature of the latter to the first turbine; means for sending expanded air from the first turbine to the system of columns; and a bypass line provided with an expansion valve configured to send air from the cold compressor to the system of columns without passing through the heat exchanger.

An apparatus for separating air by cryogenic distillation comprises N air compressors (C1, C2, C3) connected so as to receive air at ambient pressure and designed to produce air at a first pressure above 12 bar absolute, N being at least 3, each of the compressors being driven by a single asynchronous motor (M1, M2, M3), the total power of the compressors being at least 10 MW.

A method for obtaining one or more air products, in which method an air fractionation plant is used which has a column system with a pressure column wherein air is fed to the column system and is fractionated in the column system, wherein at least 90% of the total amount of air supplied to the column system is compressed wherein nitrogen-rich gas is extracted from the pressure column, and wherein, at least in a first operating mode, further air is compressed to a pressure level above the base pressure level, is expanded, and is warmed without fractionation in the column system. It is provided that, at least in the first operating mode, a proportion of the nitrogen-rich gas extracted from the pressure column is fed to the further air upstream of the expansion.

A process for separating a gas mixture, a first item of equipment of the process is heated by a first flow of a first heat producer and supplies heat to a first fluid, the first flow of heat producer being heated upstream of the first item of equipment by a heat source, a second item of equipment of the process heats a second fluid while consuming heat, the heat originating from a second flow of the first heat producer heated by the heat source, which heats the second flow of the first heat producer up to an intermediate temperature lower than the second temperature, and by a heater downstream of the source, which heats the second flow of the first heat producer, which has been heated by the heat source, from the intermediate temperature up to a second temperature higher than the first temperature.