A method for separating air by cryogenic distillation is provided, in which, at least one portion of the first oxygen-enriched liquid is sent from a first column to a first vaporizer-condenser where it is partially vaporized in the form of a film at a pressure higher than the second pressure forming a second oxygen-enriched liquid constituting at least 30% of the oxygen-enriched liquid sent to the first vaporizer-condenser and a third oxygen-enriched gas, an argon-enriched fluid is sent from a second column to a third column and the fluid is separated in the column forming an argon-rich flow at the top of the column and an oxygen-rich flow at the bottom of the column and the third oxygen-enriched gas is expanded in a turbine with production of work.

A method and apparatus for producing compressed nitrogen and liquid nitrogen. A separation system has a high-pressure column, a low-pressure column with a top condenser and a main condenser. Air is compressed in an air compressor, purified, cooled in a heat exchanger and introduced into the high-pressure column. A first part of the gaseous top nitrogen from the low-pressure column becomes compressed nitrogen product. A second part of the gaseous top nitrogen is condensed in the condensing space of the top condenser and vapor is drawn off as a residual gas stream. The vapor is expanded in a first expansion machine. A second compressed nitrogen stream from the top of the high-pressure column is expanded in a second expansion machine and then drawn off as compressed nitrogen product. A part of the nitrogen condensed in the top condenser is drawn off as liquid nitrogen product.

A method for obtaining an air product from an air separation plant having a distillation column system and a tank system. The tank system includes a first tank and a second tank. Cryogenic liquid is withdrawn from the distillation column system, stored in the tank system, and used as the air product. The cryogenic liquid is supplied to the first tank and withdrawn from the second tank during a first period, and is supplied to the second tank and withdrawn from the first tank during a second period. The tank system has a third tank to which cryogenic liquid withdrawn from the first tank and the second tank is transferred unheated. The air product is withdrawn from the third tank in liquid state, vaporized and discharged. Alternatively, the cryogenic liquid can be withdrawn from the third tank and stored in the liquid state in a fourth tank.

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.

Method for separating air by cryogenic distillation in an air separation device comprising a system of columns, a first turbine and a second turbine, wherein, in de-icing operation, a common duct bringing air from the two turbines to a column is closed by means of an isolation valve, a purge gas is sent to the turbines at a temperature above 0 C. in order to de-ice them, but purge gas is not sent to the system of columns.

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.

An expander and motor-compressor unit is disclosed. The unit includes a casing and an electric motor arranged in the casing. A compressor is arranged in the casing and drivingly coupled to the electric motor through a central shaft. Furthermore, a turbo-expander is arranged for rotation in the casing and is drivingly coupled to the electric motor and to the compressor through the central shaft.

Feed air is compressed to a first pressure in a main air compressor. A first sub-stream of the air compressed to the first pressure is cooled and fed at least in part to the distillation column system. A second sub-stream of the air compressed to the first pressure is cooled and at least partially liquefied in a low-pressure column bottom evaporator. The at least partially liquefied second sub-stream is introduced at least in part into the distillation column system. A liquid oxygen-enriched fraction is introduced into the evaporation chamber of a high-pressure top condenser. An argon-containing oxygen stream from an intermediate point in the low-pressure column is introduced into an argon column. The second sub-stream is introduced at least in part into an argon top condenser and partially evaporated therein. The second sub-stream is then introduced at least in part into the high-pressure column and/or into the low-pressure column.

The invention proposes a process and an air separation plant comprising a rectification column system comprising a high-pressure column, a low-pressure column, a main heat exchanger, and a main air compressor. The total air supplied to the rectification column system is compressed in the main air compressor to a first pressure level. The high-pressure column is operated at a second pressure level, at least 3 bar below the first pressure level. A gaseous, nitrogen-rich fluid is removed from the high-pressure column and warmed up in the gaseous state without prior liquefaction. A first partial quantity of the gaseous, nitrogen-rich fluid is warmed to a first temperature level of 150 to 100 C., supplied at this first temperature level to a booster and compressed further to a third pressure level. The first partial quantity is then warmed to a second temperature level and discharged from the air separation plant.