An air separation unit comprises a first rectification column, having a top condenser and a second rectification column placed side by side, a heat exchanger, a first pump and a second pump connected in parallel, the first pump being capable of producing liquid at a first liquid pressure and the second pump being capable of producing liquid at a second liquid pressure, higher than the first pressure, each pump having an inlet connected to the second column, a first outlet of the first pump being connected to a first outlet conduit, a second outlet of the second pump being connected to a second outlet conduit, the first and second outlet conduits being connected to the condenser section

A method and main heat exchange system for use in a cryogenic air separation plant in which down-flow and thermosiphon heat exchangers are employed to partially vaporize an oxygen-rich liquid produced in a lower pressure column and to condense the nitrogen-rich vapor in a higher pressure column. A greater proportion of the oxygen-rich liquid can be partially vaporized in the down-flow heat exchangers than in the thermosiphon heat exchangers and the nitrogen-rich vapor condensed in the thermosiphon heat exchangers can have a higher oxygen content than the nitrogen-rich vapor condensed in the down-flow heat exchangers. This allows the higher pressure column to operate at a lower pressure than would otherwise be possible. A central conduit can extend from the higher pressure column into the lower pressure column to introduce the nitrogen-rich vapor into at least the down-flow heat exchangers for purposes of reducing pressure drop and column height.

The invention relates to a method for determining the content of an impurity in a cryogenic liquid, comprising the following steps: filling a vessel with an initial volume of cryogenic liquid, vaporizing all the cryogenic liquid in the vessel, and forming a solid or liquid phase of the impurity in the vessel, isolating the vessel against any exit of material, sending a determinable volume of gas into the vessel, capable of dissolving the liquid or solid phase of the impurity in the determinable volume of gas, isolating the vessel against any entry of material, sending the gas loaded with the impurity to a gas analyser, and determining the content of the impurity in the cryogenic liquid from a content of the impurity measured, by the gas analyser, in the gas loaded with the impurity.

The present invention relates to a determination system for determining the content of at least one impurity in a cryogenic liquid, comprising: a vessel capable of receiving an initial volume of the cryogenic liquid, vaporization means for vaporizing the initial volume of cryogenic liquid until a volume of residual cryogenic liquid is obtained in which the impurity is concentrated, the vaporization means being disposed in the lower part of the vessel and means for determining the proportion of the impurity in the residual cryogenic liquid, wherein that the vaporization means comprise a heating surface capable of vaporizing the cryogenic liquid, the vaporization means being configured to keep said heating surface wet using the volume of residual cryogenic liquid.

A liquefier device which may be a retrofit to an air separation plant or utilized as part of a new design. The flow needed for the liquefier comes from an air separation plant running in a maxim oxygen state, in a stable mode. The three gas flows are low pressure oxygen, low pressure nitrogen, and higher pressure nitrogen. All of the flows are found on the side of the main heat exchanger with a temperature of about 37 degrees Fahrenheit. All of the gases put into the liquefier come out as a subcooled liquid, for storage or return to the air separation plant. This new liquefier does not include a front end electrical compressor, and will take a self-produced liquid nitrogen, pump it up to a runnable 420 PSIG pressure, and with the use of turbines, condensers, flash pots, and multi pass heat exchangers. The liquefier will make liquid from a planned amount of any pure gas oxygen or nitrogen an air separation plant can produce.