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.

A system and method for flexible production of argon from a cryogenic air separation unit is provided. The cryogenic air separation unit is capable of operating in a no-argon or low-argon mode when argon demand is low or non-existent and then switching to operating in a high-argon mode when argon is needed. The recovery of the argon products from the air separation unit is adjusted by varying the percentages of dirty shelf nitrogen and clean shelf nitrogen in the reflux stream directed to the lower pressure column. The cryogenic air separation unit and associated method also provides an efficient argon production/rejection process that minimizes the power consumption when the cryogenic air separation unit is operating in a no-argon or low-argon mode yet maintains the capability to produce higher volumes of argon products at full design capacity to meet argon product demands.

The invention relates to a heat exchanger assembly having two exchangers, each comprising a stack of parallel plates defining a first connection surface and a second connection surface that are adjacent to each other. The heat exchanger assembly can also include an enclosure between the first connection surface and the second connection surface, primary compartments in the enclosure configured to channel primary fluid through the first connection surface and the second connection surface, and a secondary compartment in the enclosure for channeling secondary fluid.

A SPECTRA process for low-temperature fractionation of air is proposed, in which bottoms liquid from an additional second rectification column used to obtain oxygen is evaporated in a second condenser evaporator arrangement. In this second condenser evaporator arrangement, gas that has been evaporated beforehand in a first condenser evaporator arrangement, which is used for condensation of tops gas from a first rectification column, is partially condensed after recompression. The invention also relates to a corresponding plant.

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.

A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger. The provision of the nitrogen product comprises, in particular, subjecting feed air to low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, and using part of the tops gas as the nitrogen product. The provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and, in an unmixed state, to liquefaction in the air separation installation.

An object of the present invention is to provide a heat exchanger that can be used in an air separation unit including a low-pressure column, a high-pressure column, and a mixing column, and that can suppress increases in equipment costs. The present invention provides a heat exchanger used in an air separation unit (1100) including a low-pressure column (600), a high-pressure column (500), and a mixing column (400), wherein the heat exchanger is composed of plates and fins, and wherein a warm gas which is at least a part (at least one of W1, W2, W3) of a feed air and at least one warm liquid (at least one of W4 and W5) which is led out from the mixing column (400) are cooled by at least one cold gas (at least one of C2 and C3) which is led out from the low-pressure column (600) and a cold gas (C1) which is led out from the mixing column (400), and a cold liquid (C6) which is led out from the low-pressure column (600) through a pressure boosting pump (800) and supplied to the mixing column (400) is heated.