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 unit and associated method for separating air by cryogenic distillation using a distillation column system including a higher pressure column, a lower pressure column, an intermediate pressure kettle column, and an argon column arrangement is provided. The disclosed air separation unit and method is particularly suited for production of high purity nitrogen for electronics applications and includes nitrogen recycle circuit necessary to attain the higher purity nitrogen products. In addition to the intermediate pressure kettle column, the present air separation unit and associated method employs a once-through argon condenser, preferably disposed within the lower pressure column as well as a once-through kettle column reboiler, a once-through kettle column condenser.

The method and the device arc used for the cryogenic decomposition of air in a distillation column system for separating nitrogen and oxygen, said system having a first high-pressure column (23), a low-pressure column (25, 26), and three condenser-evaporators, namely a high-pressure column head condenser (27), a low-pressure column bottom evaporator (28), and an auxiliary condenser (29; 228).

Process and apparatus for producing pressurized gaseous nitrogen by cryogenic separation of air. The distillation column system includes a high pressure column, a medium pressure column, a main condenser and top condenser both being condenser-evaporators. Compressed and purified feed air is cooled in a heat exchanger and introduced to the distillation system. A gaseous nitrogen stream from the high pressure column is condensed in the main condenser. Bottom liquid of the medium pressure column is evaporated and gaseous nitrogen from the medium pressure column is condensed in the top condenser. Liquid nitrogen from the medium pressure column is pressurized and introduced to the high pressure column. A second gaseous nitrogen stream from the high pressure column is recovered as pressurized gaseous nitrogen product. A portion of the compressed and purified feed air is work-expanded and then warmed in the main heat exchanger.

The distillation column system has a high-pressure column, a low-pressure column, a main condenser and a low-pressure-column top condenser. Feed air is cooled in a main heat exchanger and introduced into the high-pressure column. An oxygen-enriched liquid stream is withdrawn from the high-pressure column and introduced into the low-pressure column. A gaseous nitrogen stream is withdrawn from the high-pressure column, warmed in the main heat exchanger and withdrawn as gaseous pressurized nitrogen product. The high-pressure column has a barrier-plate section arranged immediately above the point at which the feed air is introduced. The oxygen-enriched liquid stream is withdrawn from the high-pressure column above the barrier-plate section. A purge stream is withdrawn below the barrier-plate section. The gaseous nitrogen stream, before being warmed in the main heat exchanger, is warmed in a counter-current subcooler in indirect heat exchange with the oxygen-enriched liquid stream from the high-pressure column.

A method for controlling production of high pressure gaseous oxygen in a cryogenic air separation unit that uses a high pressure gaseous oxygen bypass together with adjustments to the split of the incoming compressed and purified air between the boiler air circuit and the turbine air circuit such that the volumetric ratio of the boiler air stream to the turbine air stream is reduced to between about 0.15:1 and 0.35:1.

The invention relates to a method for separating air by cryogenic distillation in a set of columns including a first column operating at a first pressure, a second column operating at a second pressure which is lower than the first pressure, and a third column operating at a third pressure, which is lower than the second pressure, wherein the third column includes first and second evaporator-condensers, and nitrogen from a cold compressor is sent to one of the evaporator-condensers.

The invention relates to a method and device for generating two purified partial air streams under different pressures. A total air stream (1) is compressed to a first total air pressure. The compressed total air stream (5) is cooled with cooling water under the first total air pressure by way of heat exchange (4, 6). The heat exchange with cooling water for cooling the total air stream (5) is carried out as a direct heat exchange in a first direct contact cooler (6), at least in part. The cooled total air stream (9) is divided into a first partial air stream (10) and a second partial air stream (11). The first partial air stream (10) is purified in a first purification device (18) under the first total air pressure, generating the first purified partial air stream (19). The second partial air stream (11) is re-compressed to a higher pressure (12), which is higher than the first total air pressure. The re-compressed second partial air stream (14) is cooled with cooling water in a second direct contact cooler (15) by way of direct heat exchange (13, 15). The cooled second partial air stream (17) is purified under the higher pressure in a second purification device (30), thus generating the second purified partial air stream (31).

Feed air is compressed to a first pressure in a main air compressor. A first sub-stream of the air compressed to the first pressure is cooled and fed at least in part to the distillation column system. A second sub-stream of the air compressed to the first pressure is cooled and at least partially liquefied in a low-pressure column bottom evaporator. The at least partially liquefied second sub-stream is introduced at least in part into the distillation column system. A liquid oxygen-enriched fraction is introduced into the evaporation chamber of a high-pressure top condenser. An argon-containing oxygen stream from an intermediate point in the low-pressure column is introduced into an argon column. The second sub-stream is introduced at least in part into an argon top condenser and partially evaporated therein. The second sub-stream is then introduced at least in part into the high-pressure column and/or into the low-pressure column.

An air separation unit and associated method for separating air by cryogenic distillation using a distillation column system including a higher pressure column, a lower pressure column, an intermediate pressure kettle column, and an argon column arrangement is provided. The disclosed air separation unit and method is particularly suited for production of an argon product as well as several nitrogen products wherein a portion of the nitrogen overhead intermediate pressure kettle column is taken as an intermediate or elevated pressure nitrogen product. The present air separation unit and associated method employs a once-through kettle column reboiler, a once-through kettle column condenser while the argon condenser condenses an argon-rich vapor stream against a pumped oxygen stream from the bottom of the lower pressure column.