A method for cryogenic separation of air uses an air separation plant, wherein, in a mass transfer column, a liquid first fluid and a gaseous second fluid are subjected to mass transfer with one another. A gaseous third fluid is removed from the column and is at least partly discharged from the air separation plant. A liquid fourth fluid is removed from the column and is at least partly fed into a low-pressure column. The first fluid is formed using at least a part of an oxygen-rich liquid removed from the low-pressure column. The second fluid is formed using an oxygen-enriched liquid removed from a high-pressure column. The oxygen-enriched liquid removed from the high-pressure column and bottom liquid of the mass transfer column are mixed and partly evaporated in a condenser-evaporator. A liquid fifth fluid is removed from the mass transfer column between a feed point for the first fluid and a feed point for the oxygen-enriched liquid, and is at least partly fed into the low-pressure column. The fifth fluid or a fraction thereof is fed into the low-pressure column below the fourth fluid or a fraction thereof.

A method for controlling a coupled heat exchanger system having a first heat exchanger block and a second heat exchanger block. A first fluid stream is divided into a first partial current and a second partial current both flowing through the heat exchanger system. A second fluid stream flows through the first heat exchanger block counter to the first partial current. A third fluid stream flows through the second heat exchanger block counter to the second partial current. An intermediate temperature is measured on one of the heat exchanger blocks. The amount of the first partial current and the second partial current is controlled based on the current value of the intermediate temperature. This control reduces the strain on the heat exchangers by changing loads while keeping fluctuations of the intermediate temperature low.

A method and plant for the cryogenic separation of air, the plant having an air compressor, a heat exchanger and a distillation column system having a low-pressure column at a first pressure and a high-pressure column at a second pressure. Feed air is compressed in the air compressor to a third pressure at least 2 bar above the second pressure A first fraction of compressed feed air is cooled in the heat exchanger and expanded in a first expansion turbine. A second fraction is cooled in the heat exchanger and expanded in a second expansion turbine A third fraction is compressed to a fourth pressure, cooled in the heat exchanger and then expanded. The third fraction is compressed to the fourth pressure in sequence in a recompressor, a hot first turbine booster and a second turbine booster. A dense fluid expander is used to expand the third fraction.

A compressed air stream is cooled in an exchanger to form a compressed cooled air stream. The stream is then cryogenically compressed in a first compressor to form a first pressurized gas stream. The first pressurized gas stream is further cooled in the exchanger, cryogenically compressed in a second compressor, and then it is cooled and partially liquefied. The cooled and partially liquefied product is then fed to a system of distillation columns. A liquid product is removed from the system of distillation columns. This product is then pressurized, vaporized and warmed in the exchanger to yield pressurized gaseous product.

A method for obtaining one or more air products by means of an air separation unit comprising a first booster, a second booster, a first decompression machine, and a rectification column system which has a high-pressure column operated at a first pressure level and a low-pressure column operated at a second pressure level below the first pressure level. All of the air supplied to the rectification column system is first compressed to a third pressure level, which lies at least 3 bar above the first pressure level, as a feed air quantity. A first fraction of the feed air quantity is supplied to a first booster at the third pressure level and at a temperature level of −140 to −70 ° C. and is compressed to a fourth pressure level using the first booster.

A portion of feed air is expanded and cooled in front of a main heat exchanger, and is used as cold for precooling the remaining unexpanded feed air inside the main heat exchanger. A portion of the feed air precooled inside the main heat exchanger is removed to outside the main heat exchanger, expanded and cooled, and used as cold to cool the remaining unexpanded precooled feed air inside the main heat exchanger.

A method and the apparatus for obtaining a compressed gas product by means of cryogenic separation of air in a distillation column system which has a high-pressure column and a low-pressure column. All of the feed air is compressed in a main air compressor to a first pressure which is at least 4 bar higher than the operating pressure of the high-pressure column. A first partial flow of the feed air compressed in the main air compressor is cooled to an intermediate temperature in a main heat exchanger and is expanded so as to perform work in a first air turbine. At least a first part of the first partial flow expanded so as to perform work is introduced into the distillation column system.

A process for cryogenic separation of air using an air separation plant configured as a high air pressure air separation plant is provided, wherein of the air initially compressed several partial air streams are formed which are at least in part further compressed, cooled in a main heat exchanger and expanded before being introduced into the column system. The partial air streams include a first partial air stream and a second partial air stream whose air is compressed in parallel in a first warm booster and a second warm booster and thereafter expanded in a first expander and a second expander mechanically coupled to the first booster and to the second booster, respectively. A corresponding air separation plant is also part of the present invention.

A method and plant for the cryogenic separation of air, the plant having an air compressor, a heat exchanger and a distillation column system having a low-pressure column at a first pressure and a high-pressure column at a second pressure. Feed air is compressed in the air compressor to a third pressure at least 2 bar above the second pressure A first fraction of compressed feed air is cooled in the heat exchanger and expanded in a first expansion turbine. A second fraction is cooled in the heat exchanger and expanded in a second expansion turbine A third fraction is compressed to a fourth pressure, cooled in the heat exchanger and then expanded. The third fraction is compressed to the fourth pressure in sequence in a recompressor, a hot first turbine booster and a second turbine booster. A dense fluid expander is used to expand the third fraction.

In a method for separating air by cryogenic distillation in a system of columns comprising a first column operating at a first pressure and a second column operating at a second pressure which is lower than the first column, the temperature T1 at which an airflow leaves, after cooling, the heat exchanger by rising towards the cold end of said heat exchanger and enters the first column is at least 1? C., preferably at least 2? C., higher than the dew point of the airflow.