METHOD AND DEVICE FOR THE LOW-TEMPERATURE SEPARATION OF AIR AT VARIABLE ENERGY CONSUMPTION

• US 20170131028A1
• Filed: 06/25/2015
• Published: 05/11/2017
• Est. Priority Date: 07/05/2014
• Status: Active Grant

• Current Assignee: Linde AG (Linde Plc)
• Original Assignee: Linde AG (Linde Plc)
• Inventors: GOLOUBEV, Dimitri
• Granted Patent: US 10,458,702 B2
• Time in Patent Office: Days
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2240/42 the fluid being air
• CPC Class Codes: F25J 2245/50 the recycled stream being oxygen
• CPC Class Codes: F25J 3/04018 of main feed air
• CPC Class Codes: F25J 3/04024 of purified feed air, so-called boosted air
• CPC Class Codes: F25J 3/0403 of nitrogen
• CPC Class Codes: F25J 3/04054 of air
• CPC Class Codes: F25J 3/04084 of nitrogen
• CPC Class Codes: F25J 3/0409 of oxygen
• CPC Class Codes: F25J 3/04175 at a pressure of substantially more than the highest pressure column
• CPC Class Codes: F25J 3/042 having an intermediate feed connection
• CPC Class Codes: F25J 3/0429 of feed air, e.g. used as waste or product air or expanded into an auxiliary column
• CPC Class Codes: F25J 3/04296 Claude expansion, i.e. expanded into the main or high pressure column
• CPC Class Codes: F25J 3/04345 and comprising a gas work expansion loop
• CPC Class Codes: F25J 3/04393 using multiple or multistage gas work expansion
• CPC Class Codes: F25J 3/04412 in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
• CPC Class Codes: F25J 3/04678 cooled by oxygen enriched liquid from high pressure column bottoms
• CPC Class Codes: F25J 3/04721 Producing pure argon, e.g. recovered from a crude argon column
• CPC Class Codes: F25J 3/04812 Different modes, i.e. "runs" of operation F25J3/04472 takes precedence

Abstract

A method and device used to variably obtain a compressed-gas product by means low-temperature separation of air in a distillation column system. In a first operating mode, a first amount of first compressed-gas product is obtained, and, in a second operating mode, a second, smaller amount is obtained. In the first operating mode, a first amount of air is compressed in the main air compressor, and in the second operating mode, a second, larger amount is compressed in the main air compressor.

Claims

1. Method for variably obtaining a pressurized-gas product by means of the low-temperature separation of air in a distillation column system, which has a high-pressure column and a low-pressure column, in which

the entire feed air is compressed in a main air compressor to a first pressure, which is at least 4 bar higher than the operating pressure of the high-pressure column,

a first partial stream of the feed air compressed in the main air compressor is cooled down to an intermediate temperature in a main heat exchanger and expanded in a first air turbine in such a way that work is performed,

at least a first part of the work-performing expanded first partial stream is introduced into the distillation column system,

a second partial stream of the feed air compressed in the main air compressor is recompressed to a second pressure, which is higher than the first pressure, in a first booster air compressor, which is operated in the warm state and is driven by the first turbine, cooled down in the main heat exchanger and subsequently expanded and introduced into the distillation column system,

a first product stream is removed in a liquid form from the distillation column system and subjected to a pressure increase to a first product pressure,

the first product stream is evaporated or pseudo-evaporated under the first product pressure and warmed up in the main heat exchanger,

the warmed-up first product stream is obtained as the first pressurized-gas product,

a first process stream, which contains at least 78 mol % of nitrogen, is compressed in a multi-stage compressor from an inlet pressure to a final pressure,

the multi-stage compressor being formed by the main air compressor and

the first process stream being formed by the entire feed air,

at least for a time a second process stream, which contains at least 78 mol % of nitrogen, is mixed with the first process stream downstream of the first stage of the multi-stage compressor, the second process stream being formed by part of the work-performing expanded first partial stream of the feed air,

in a first operating mode, a first amount of first pressurized-gas product is obtained,

in a second operating mode, a second amount of first pressurized-gas product, which is smaller than the first amount, is obtained,

in the first operating mode, a first amount of the second process stream, which may even be zero, is compressed in the multi-stage compressor and

in the second operating mode, a second amount of the second process stream, which is greater than the first amount of the second process stream, is compressed in the multi-stage compressor.

2. The method as claimed in claim 1, characterized in that

a third process stream is compressed in a nitrogen product compressor from an inlet pressure to a final pressure and

at least for a time a fourth process stream is mixed with the third process stream downstream of the first stage of the nitrogen product compressor,

the third process stream being formed by a first gaseous nitrogen stream from the low-pressure column and

the fourth process stream being formed by a first gaseous nitrogen stream from the high-pressure column.

3. The method as claimed in claim 1, characterized in that the second process stream is mixed with the first process stream or the fourth process stream is mixed with the second process stream at an intermediate stage of the multi-stage compressor.

5. The method as claimed in claim 1, characterized in that

a third partial stream of the feed air compressed in the main air compressor is cooled down to an intermediate temperature in the main heat exchanger and expanded in a second air turbine in such a way that work is performed and

at least a first part of the work-performing expanded third partial stream is introduced into the distillation column system,

the turbine inlet pressure of the second air turbine being in particular equal to the first pressure.

6. The method as claimed in claim 5, characterized in that

the second partial stream of the feed air compressed in the main air compressor is cooled down to an intermediate temperature downstream of the first booster air compressor in the main heat exchanger, recompressed to a third pressure, which is higher than the first pressure, in a second booster air compressor, which is operated as a cold compressor and is driven by the second turbine, cooled down in the main heat exchanger and subsequently expanded and introduced into the distillation column system.

7. The method as claimed in claim 5, characterized in that a fourth partial stream of the air compressed in the main air compressor is cooled down under the first pressure in the main heat exchanger and subsequently expanded and introduced into the distillation column system.

8. The method as claimed in claim 7, characterized in that

the third partial stream is expanded in the second air turbine to a pressure that is at least one bar higher than the operating pressure of the high-pressure column, and

the work-performing expanded third partial stream is cooled down further in the main heat exchanger and subsequently expanded and introduced into the distillation column system.

9. The method as claimed in claim 1, characterized in that

in the first operating mode, a first amount of feed air is compressed in the main air compressor and

in the second operating mode, a second amount of eed air is compressed in the main air compressor,

the ratio of the second amount of feed air to the first amount of feed air being greater, in particular greater by more than 3%, than the ratio between the second amount of first pressurized-gas product and the first amount of first pressurized-gas product.

4. The method as claimed in claim l, characterized in that, in the second operating mode, an oxygen gas stream is removed from the lower region of the low-pressure column and mixed with a nitrogen-enriched stream from the upper region of the low-pressure column and the mixture is warmed up in the main heat exchanger,

10. A device for variably obtaining a pressurized-gas product by means of the low-temperature separation of air with

a distillation column system, which has a high-pressure column and a low-pressure column,

a main air compressor for compressing the entire feed air to a first pressure, which is at least 4 bar higher than the operating pressure of the high-pressure column,

means for cooling down a first partial stream of the feed air compressed in the main air compressor to an intermediate temperature in a main heat exchanger,

a first air turbine for expanding the cooled-down first partial stream in such a way that work is performed,

means for introducing the work-performing expanded first partial stream into the distillation column system,

a first booster air compressor for recompressing a second partial stream of the feed air compressed in the main air compressor to a second pressure, which is higher than the first pressure, the booster air compressor being operable in the warm state and driven by the first turbine, is recompressed,

means for cooling down the recompressed second partial stream in the main heat exchanger cooled down,

means for expanding the cooled-down second partial stream and introducing it into the distillation column system,

means for removing a first product stream in a liquid form from the distillation column system removed and for increasing the pressure of the liquid first product stream to a first product pressure,

means for evaporating or pseudo-evaporating and warming up the first product stream under the first product pressure in the main heat exchanger,

means for obtaining the warmed-up first product stream as the first pressurized-gas product,

a multi-stage compressor for compressing a first process stream, which contains at least 78 mol % of nitrogen, from an inlet pressure to a final pressure,

the multi-stage compressor being formed by the main air compressor and

the first process stream being formed by the entire feed air and,

means for mixing a second process stream, which contains at least 78 mol % of nitrogen, with the first process stream downstream of the first stage of the multi-stage compressor, the second process stream (180) being formed by part of the first partial stream of the feed air expanded in such a way that work is performed,

means for switching over between a first operating mode and a second operating mode,

in the first operating mode, a first amount of first pressurized-gas product being obtained,

in a second operating mode, a second amount of first pressurized-gas product, which is smaller than the first amount, being obtained and

the means for switching over between the first operating mode and the second operating mode being formed such that

in the first operating mode, a first amount of the second process stream, which may even be zero, is compressed in the multi-stage compressor from an inlet pressure to a final pressure and

in the second operating mode, a second amount of the second process stream, which is greater than the first amount of the second process stream, is compressed in the multi-stage compressor.