# US 6,295,840 B1 · Pressurized liquid cryogen process

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- Number: US 6,295,840 B1
- Document ID: US6295840B1
- Status: Granted
- Kind: B1
- Application number: 09/712,901
- Filed: 2000-11-15
- Granted: 2001-10-02
- Earliest claimed: 2000-11-15
- Assignees: Air Products and Chemicals, Inc.
- Inventors: Arthur Ramsden Smith
- Web page: https://patentgrep.com/patent/US6295840B1

## CPC

- F25J 3/0409: {of oxygen}
- F25J 3/04084: {of nitrogen}
- F25J 3/04296: {Claude expansion, i.e. expanded into the main or high pressure column}
- F25J 3/04303: {Lachmann expansion, i.e. expanded into oxygen producing or low pressure column}
- F25J 3/04375: {Details relating to the work expansion, e.g. process parameter etc.}
- F25J 3/04393: {using multiple or multistage gas work expansion}
- 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}
- F25J 3/04781: {Pressure changing devices, e.g. for compression, expansion, liquid pumping}
- F25J 3/04872: {Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.}
- F25J 3/04987: {for offshore use}
- F25J 2205/02: using simple phase separation in a vessel or drum
- F25J 2205/04: in the feed line, i.e. upstream of the fractionation step
- F25J 2235/04: using a pressure accumulator
- F25J 2245/40: the recycled stream being air
- F25J 2245/42: the recycled stream being nitrogen
- F25J 2290/62: Details of storing a fluid in a tank
- F25J: LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS {OR LIQUEFIED GASEOUS} MIXTURES BY PRESSURE AND COLD TREATMENT {OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE (cryogenic pumps F04B37/08; gas storage vessels, gas holders F17; filing vessels with, or discharging from vessels, compressed, liquefied or solidified gases F17C; refrigeration machines, plants, or systems F25B)}

## Abstract

A cryogenic air separation process wherein one or more pressurized product streams enriched in oxygen, nitrogen and argon are produced by cryogenic distillation. One or more of the product streams are pressurized above the operating pressure of the distillation column by introducing a pressurizing fluid into a vessel containing a lower pressure product liquid. In the design of the system the pressurizing fluid can be air or streams enriched in oxygen, nitrogen or argon. Product stream pressurization is accomplished without the use of mechanical pumping devices.

## Claims

### Claim 1

A method for the separation of air to provide at least one pressurized product enriched in a component of air, which method comprises:
(a) providing a pressurized, substantially contaminant-free air feed stream;
(b) cooling at least a portion of the contaminant-free air feed stream to provide a cooled air feed stream, and separating the cooled air feed stream in a cryogenic air separation system to provide an intermediate liquid product stream enriched in at least one of the components of air;
(c) introducing at least a portion of the intermediate liquid product stream into a vessel;
(d) pressurizing the vessel by introducing a pressurized fluid into the vessel;
(e) withdrawing from the vessel a pressurized liquid product enriched in one of the components of air; and
(f) repeating (c), (d), and (e) in a cyclic manner.

### Claim 2 (depends on 1)

The method of claim 1 wherein the pressurized fluid is a gas provided by compressing and cooling a portion of the contaminant-free air feed stream.

### Claim 3 (depends on 1)

The method of claim 1 wherein vapor displaced while introducing intermediate liquid product into the vessel is reduced in pressure to provide a reduced-pressure vapor, and the reduced-pressure vapor is returned to the cryogenic air separation system.

### Claim 4 (depends on 3)

The method of claim 3 wherein the reduced-pressure vapor is retained in a holding vessel before being returned to the cryogenic air separation system.

### Claim 5 (depends on 3)

The method of claim 3 wherein the vapor withdrawn from the vessel is reduced in pressure across a throttling valve.

### Claim 6 (depends on 3)

The method of claim 3 wherein the vapor withdrawn from the vessel is reduced in pressure by work expansion through a turboexpander.

### Claim 7 (depends on 1)

The method of claim 1 which further comprises vaporizing the pressurized liquid product to provide a portion of the cooling required in (b) and yield a pressurized gaseous product stream.

### Claim 8 (depends on 7)

The method of claim 7 wherein the pressurized gaseous product stream is enriched in oxygen.

### Claim 9 (depends on 1)

The method of claim 1 wherein a portion of the substantially contaminant-free air feed stream is compressed, cooled, work expanded, and introduced into the cryogenic air separation system.

### Claim 10 (depends on 1)

The method of claim 1 which further comprises
(g) introducing a portion of the pressurized liquid product into an additional vessel;
(h) pressurizing the additional vessel by introducing additional pressurized fluid into the vessel;
(i) withdrawing from the additional vessel a pressurized liquid product enriched in one of the components of air; and
(j) repeating (g), (h), and (i) in a cyclic manner.

### Claim 11 (depends on 10)

The method of claim 10 wherein (c), (d), and (e) are carried out concurrently with (i) during a first time period; (g), (h), and (i) are carried out concurrently with (e) during a second time period; and the first and second time periods are repeated in a cyclic manner.

### Claim 12 (depends on 10)

The method of claim 10 wherein vapor displaced while introducing intermediate liquid product into the additional vessel is reduced in pressure to provide an additional reduced-pressure vapor, and the additional reduced-pressure vapor is returned to the cryogenic air separation system.

### Claim 13 (depends on 12)

The method of claim 12 wherein the additional reduced-pressure vapor is retained in a holding vessel before being returned to the cryogenic air separation system.

### Claim 14 (depends on 12)

The method of claim 12 wherein the vapor withdrawn from the additional vessel is reduced in pressure across a throttling valve.

### Claim 15 (depends on 12)

The method of claim 12 wherein the vapor withdrawn from the additional vessel is reduced in pressure by work expansion through a turboexpander.

### Claim 16 (depends on 10)

The method of claim 10 which further comprises vaporizing the pressurized liquid product to provide a portion of the cooling required in (b) and yield a pressurized gaseous product stream.

### Claim 17 (depends on 16)

The method of claim 16 wherein the pressurized gaseous product stream is enriched in oxygen.

### Claim 18 (depends on 16)

The method of claim 16 wherein the pressurized gaseous product stream is enriched in nitrogen.

### Claim 19 (depends on 2)

The method of claim 2 wherein a portion of the pressurized fluid is reduced in pressure and introduced into the cryogenic air separation system.

### Claim 20 (depends on 2)

The method of claim 2 wherein a portion of the pressurized fluid is reduced in pressure and partially condensed to form a vapor and a liquid, the liquid is introduced into the cryogenic air separation system, and the vapor provides the pressurized gas in (d).