A moderate pressure, argon and nitrogen producing cryogenic air separation unit and air separation cycle having a higher pressure column, a lower pressure column and an argon column arrangement is disclosed. The moderate pressure, argon and nitrogen producing cryogenic air separation unit is configured to take a first portion of an oxygen enriched stream from the lower pressure column, which together with an external source of liquid nitrogen is used as the boiling side refrigerant to condense the argon in the argon condenser. Use of the external source of liquid nitrogen in the argon condenser allows a second portion of the oxygen enriched stream from the lower pressure column to be taken as a liquid oxygen product stream.

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.

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.

In a method for regulating a device for separating air by cryogenic distillation, during the change from a low-flow mode to a high-flow mode, two flow rates of reflux sent to the low-pressure column of a double column are increased more rapidly than the flow rate of gaseous air sent to the medium-pressure column of the double column in order to ensure the stability of the oxygen content in the argon bulge of the low-pressure column during the mode change.

A method and device to variably obtain argon by means of low-temperature separation. Feed air is cooled in a main heat exchanger and then conducted into a distillation column system with a high-pressure column and a low-pressure column. Argon is obtained using a crud argon column and a purified argon column. A purified liquid argon product flow is generated from an argon-enriched flow from the low-pressure column. In a first operating mode, a first quantity of purified argon product is discharged, and in a second operating mode, a reduced quantity of purified argon product is discharged. In the second operating mode, a gaseous argon return flow is drawn from the crude argon column or the purified argon column and heated in a separate passage of the main heat exchanger.

A cryogenic air separation unit that provides flexibility in the production of liquid products is disclosed. The present cryogenic air separation unit and associated operating methods involves the use of a dual nozzle arrangement for the main heat exchanger that allows a turbine air stream draw from the main heat exchanger at different temperatures to provide refrigeration to the cryogenic air separation unit which, in turn, enables different production modes for the various liquid products.

A moderate pressure, argon and nitrogen producing cryogenic air separation unit and air separation cycle having a higher pressure column, a lower pressure column and an argon column arrangement is disclosed. The moderate pressure, argon and nitrogen producing cryogenic air separation unit is configured to take a first portion of an oxygen enriched stream from the lower pressure column, which together with an external source of liquid nitrogen is used as the boiling side refrigerant to condense the argon in the argon condenser. Use of the external source of liquid nitrogen in the argon condenser allows a second portion of the oxygen enriched stream from the lower pressure column to be taken as a liquid oxygen product stream.

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.

An air separation device can include: a first compressor and a second compressor for compressing feed air; a first refrigerator and a second refrigerator for cooling the feed air; a pre-purification unit for pre-purifying the feed air; a flow rate measuring unit for measuring the flow rate of the feed air; a main heat exchanger for subjecting the feed air to heat exchange; a purification portion into which the feed air led out from the main heat exchanger is fed, and which separates and purifies product nitrogen and/or product oxygen from the feed air; and a compressor control unit for controlling the feed quantity of the feed air in accordance with an increase or decrease in the production quantity of product nitrogen and/or product oxygen.