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 gasses 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.

A method for the cryogenic fractionation of air, in which a liquid volume present in a vaporization chamber in a distillation column system of an air fractionation plant is fed by means of a cryogenic liquid and in which a proportion of the liquid volume is continuously transferred into the gas phase by vaporization, wherein, in addition to oxygen, the cryogenic liquid contains components, including xenon, which are higher-boiling than oxygen. The content of xenon in the cryogenic liquid is determined and used as a measure of any enrichment of the components which are higher-boiling than oxygen in the cryogenic liquid. A corresponding air fractionation plant is also described.

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.

A method and apparatus to obtain a compressed nitrogen product by low-temperature fractionation of air in a distillation column system. The system has a high-pressure column, a low-pressure column, a main condenser, and a low-pressure column top condenser. Bottoms liquid from the low-pressure column is evaporated in the top condenser and the gas formed is decompressed to perform work that drives a cold compressor. A gaseous first compressed nitrogen product stream from the high-pressure column is warmed in the main heat exchanger. A further gaseous nitrogen stream from the low-pressure column is compressed in the cold compressor and warmed as a second compressed nitrogen product stream in the main heat exchanger. The cold compressor overcomes a pressure differential which is at least equal to two thirds of the pressure differential between the top of the high-pressure column and the top of the low-pressure column.

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 improved process for liquid nitrogen production by cryogenic air separation using a distillation column system to enhance the product recovery.

A method for separating air is provided, in which a flow of oxygen-rich liquid is sent to a top of a pure oxygen column, having a pure oxygen reboiler, in which said flow is purified in order to form a vessel liquid containing at least 98 mol % of oxygen and the vessel liquid is drawn off as a product. A supercharged airflow at a second pressure is sent to the pure oxygen reboiler and to a liquid oxygen vaporizer; a nitrogen-rich gas is drawn from the top of the medium-pressure column and sent to an intermediate reboiler of the low-pressure column and the condensed gas is sent to the top of the medium-pressure column; and a nitrogen-rich gas or air is sent to a vessel reboiler of the low-pressure column and the liquid that condenses therein is sent to the medium-pressure column.

A request to initiate startup of an air separation plant may be received, and, in response to receiving the request, startup information that identifies a sequence of steps to be automatically executed to start up the air separation plant is retrieved. Each step may be associated with a component of the air separation plant, and may be associated with an action and a set of permissives corresponding to the action. The set of permissives for each action may specify one or more parameters for controlling the execution of the corresponding action. After retrieving the startup information, the system may automatically initiate execution of the sequence of steps, and may monitor the execution of each of the steps. The system may determine, based on the monitoring, whether to modify a parameter specified by one of the permissives corresponding to an executed action.

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.

A nitrogen liquefier configured to be integrated with an argon and nitrogen producing cryogenic air separation unit and method of nitrogen liquefaction are provided. The integrated nitrogen liquefier and associated methods may be operated in at least three distinct modes including: (i) a nil liquid nitrogen mode; (ii) a low liquid nitrogen mode; and (iii) a high liquid nitrogen mode. The present systems and methods are further characterized in an oxygen enriched stream from the lower pressure column of the air separation unit is an oxygen enriched condensing medium used in the argon condenser.