A method and device to produce oxygen by the low-temperature separation of air at variable energy consumption. A distillation column system comprises a high-pressure column, a low-pressure column and a main condenser, a secondary condenser and a supplementary condenser. Gaseous nitrogen from the high-pressure column is liquefied in the main condenser in indirect heat exchange with an intermediate liquid from the low-pressure column. A first liquid oxygen stream from the bottom of the low-pressure column is evaporated in the secondary condenser in indirect heat exchange with feed air to obtain a gaseous oxygen product. The supplementary condenser serves as a bottom heating device for the low-pressure column and is heated by means of a first nitrogen stream from the distillation column system, which nitrogen stream was compressed previously in a cold compressor.

A plant for the production of liquefied methane having, arranged in series, a means for the generation of methane from hydrogen and carbon dioxide, a means for drying the gas mixture produced by the methane generation means, a purification means configured to remove carbon dioxide from the gas mixture dried in the drying means, a liquefier configured to liquefy the methane contained in the gas mixture purified in the purification means, and a liquefied gas storage facility configured to store the methane liquefied by the liquefier.

In a method for separating air by cryogenic distillation using a column system consisting of a higher pressure column operating at a first pressure and a lower pressure column operating at a second pressure, a first air flow constituting between 75% and 98% of the air sent to the column system compressed to a third pressure above the first pressure, is sent to the higher pressure column, a second air flow constituting between 5% and 25% of the air sent to the column system is compressed to a fourth pressure above the second pressure but lower than the third pressure, is sent to the lower pressure column, a third column separates an argon-enriched flow and the air sent to the lower pressure column constitutes between 10% and 25% of the total air sent to the column system.

A process comprises a first set of distillation columns and a second set of distillation columns, a low-pressure column of the first set being connected to a column operating at higher pressure of the second set by means of a gas arriving from the top of the column operating at a higher pressure and/or by means of a fluid arriving from the low-pressure column.

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).

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).

An air fractionation plant in which a cooling water circuit having a recooling apparatus is provided for cooling compressed air, where the recooling apparatus is configured for cooling cooling water using cooling air. The recooling apparatus is configured so as to cool the cooling water, at least at a wet bulb temperature of the cooling air of more than 289 K, to a temperature which is not more than 3 K above the wet bulb temperature. A corresponding operating method and a control facility are likewise provided.

An air separation plant is provided that includes a plurality of air compressors, a plurality of air purification units, and one or more cold boxes. In a first mode of operation, a first air compressor is configured to compress air to a higher pressure than a second air compressor. In a second mode of operation, the second air compressor is configured to compress air to a higher pressure than during the first mode of operation.