# US 5,345,773 A · Method and apparatus for the production of ultra-high purity nitrogen

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- Number: US 5,345,773 A
- Document ID: US5345773A
- Status: Granted
- Kind: A
- Application number: 08/026,480
- Filed: 1993-03-04
- Granted: 1994-09-13
- Earliest claimed: 1993-03-04
- Assignees: Teisan Kabushiki Kaisha
- Inventors: Takashi Nagamura; Takao Yamamoto
- Web page: https://patentgrep.com/patent/US5345773A

## CPC

- F25J 3/04084: {of nitrogen}
- C01B 21/04: Purification or separation of nitrogen (by liquefying F25J)
- F25J 3/04103: {using solely hydrostatic liquid head}
- F25J 3/04163: {Hot end purification of the feed air (arrangements of cold regenerators F25J5/00)}
- F25J 3/04169: {by adsorption of the impurities (adsorption in general B01D53/02)}
- F25J 3/04193: {Division of the main heat exchange line in consecutive sections having different functions}
- F25J 3/04212: {and simultaneously condensing vapor from a column serving as reflux within the or another column}
- F25J 3/04224: {Cores associated with a liquefaction or refrigeration cycle}
- F25J 3/0423: {Subcooling of liquid process streams}
- F25J 3/04284: {using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams (F25J3/04333 takes precedence)}
- F25J 3/04309: {of nitrogen}
- F25J 3/04357: {and comprising a gas work expansion loop}
- F25J 3/044: {using a single pressure main column system only (F25J3/0446, F25J3/04624, F25J3/04636 take precedence)}
- 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 3/04854: {Safety aspects of operation}
- F25J 2200/74: Refluxing the column with at least a part of the partially condensed overhead gas
- F25J 2200/94: Details relating to the withdrawal point
- F25J 2205/02: using simple phase separation in a vessel or drum
- F25J 2205/60: using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
- F25J 2205/82: using a reactor with combustion or catalytic reaction
- F25J 2215/42: Nitrogen or special cases, e.g. multiple or low purity N2
- F25J 2215/44: Ultra high purity nitrogen, i.e. generally less than 1 ppb impurities
- F25J 2220/42: Separating low boiling, i.e. more volatile components from nitrogen, e.g. He, H2, Ne
- F25J 2220/44: Separating high boiling, i.e. less volatile components from nitrogen, e.g. CO, Ar, O2, hydrocarbons
- F25J 2245/42: the recycled stream being nitrogen
- F25J 2250/10: Boiler-condenser with superposed stages
- F25J 2250/20: Boiler-condenser with multiple exchanger cores in parallel or with multiple re-boiling or condensing streams
- F25J 2250/42: One fluid being nitrogen
- F25J 2270/02: Internal refrigeration with liquid vaporising loop
- F25J 2280/02: Control in general, load changes, different modes ("runs"), measurements
- Y02P 20/151: Reduction of greenhouse gas [GHG] emissions, e.g. CO2
- Y10S 62/939: Partial feed stream expansion, air
- 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)}
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A method and apparatus for separating air by low temperature liquefaction and fractionation wherein feed air is compressed and cooled and supplied to the high pressure stage of a two-stage fractionation column from the bottom of the high pressure stage of which liquid is expanded and introduced at an intermediate level of the low pressure stage and a gaseous nitrogen product is removed from the top of the high pressure stage of the column, and wherein an oxygen product is removed from the bottom of the low pressure stage and a gaseous nitrogen product is removed from the top of the low pressure stage. Both stages contain solid material providing solid surfaces on which mass transfer takes place to effect fractionation over a substantial vertical distance. The improvement comprises removing a liquid from the high pressure stage intermediate the height of the solid material therein. The removed liquid is subcooled and expanded to produce a gas and a liquid, and the last-named liquid is withdrawn as ultra-high purity nitrogen.

## Claims

### Claim 1

In a method for separating air by low temperature liquefaction and fractionation wherein feed air is compressed and cooled and supplied to a high pressure stage of a two-stage fractionation column from the bottom of the high pressure stage of which liquid is expanded and introduced at an intermediate level of a low pressure stage of the column and a gaseous nitrogen product is removed from the top of the high pressure stage, and wherein an oxygen product is removed from the bottom of the low pressure stage and a gaseous nitrogen product is removed from the top of the low pressure stage, both of said stages containing solid material providing solid surfaces on which mass transfer takes place to effect fractionation over a substantial vertical height in each said stage; the improvement comprising removing a liquid from said high pressure stage intermediate said height of said solid material in said high pressure stage, subcooling said removed liquid, expanding said subcooled liquid to produce a gas and a liquid, and withdrawing said liquid as ultra-high purity nitrogen.

### Claim 2 (depends on 1)

A method as claimed in claim 1, and removing liquid from the top of said high pressure stage, vaporizing said liquid to a vapor, compressing said vapor, expanding a portion of said compressed vapor to provide refrigeration, imparting said refrigeration to the remainder of said compressed vapor, expanding said remainder of said compressed vapor and supplying the same to the top of said high pressure stage at least partly in liquid phase.

### Claim 3 (depends on 1)

A method as claimed in claim 1, and removing a liquid from said high pressure stage intermediate said height but below the point of removal of the liquid which becomes said ultra-high purity nitrogen, and expanding the latter removed liquid and introducing the same into an upper portion of said low pressure stage at least partly in liquid phase.

### Claim 4 (depends on 1)

A method as claimed in claim 1, and supplying a portion of said ultra-high purity liquid nitrogen to the top of said low pressure stage as reflux.

### Claim 5 (depends on 1)

A method as claimed in claim 1, and withdrawing gaseous nitrogen from the top of the high pressure stage, cooling and at least partially condensing the last-named nitrogen by heat exchange with said liquid ultra-high purity nitrogen, and introducing said at least partially condensed nitrogen into an tipper portion of said high pressure stage.

### Claim 6 (depends on 1)

A method as claimed in claim 1, and withdrawing gaseous nitrogen from the top of said high pressure stage, warming the thus-withdrawn nitrogen in heat exchange with feed air, expanding the thus-warmed nitrogen to the pressure of the low pressure stage, and introducing the thus-expanded nitrogen into the low pressure stage intermediate said height thereof.

### Claim 7 (depends on 1)

A method as claimed in claim 1, and removing hydrogen and carbon monoxide from the feed air after compression of the same.

### Claim 8

Apparatus for separating air by low temperature liquefaction and fractionation wherein feed air is compressed and cooled and supplied to a high pressure stage of a two-stage fractionation column from the bottom of the high pressure stage of which liquid is expanded and introduced at an intermediate level of a low pressure stage of the column and a gaseous nitrogen product is removed from the top of the high pressure stage, and wherein an oxygen product is removed from the bottom of the low pressure stage and a gaseous nitrogen product is removed from the top of the low pressure stage, both of said stages containing solid material providing solid surfaces on which mass transfer takes place to effect fractionation over a substantial vertical height; the improvement comprising means for removing a liquid from said high pressure stage intermediate said height of said solid material in said high pressure stage, means for subcooling said removed liquid, means for expanding said subcooled liquid to produce a gas and a liquid, and means for withdrawing said liquid as ultra-high purity nitrogen.

### Claim 9 (depends on 8)

Apparatus as claimed in claim 8, and means for removing liquid from the top of said high pressure stage, means for vaporizing said liquid to a vapor, means for compressing said vapor, means for expanding a portion of said compressed vapor to provide refrigeration, means for imparting said refrigeration to the remainder of said compressed vapor, and means for expanding said remainder of said compressed vapor and for supplying the same to the top of said high pressure stage at least partly in liquid phase.

### Claim 10 (depends on 8)

Apparatus as claimed in claim 8, and means for removing a liquid from said high pressure stage intermediate said height but below the point of removal of the liquid which becomes said ultra-high purity nitrogen, and means for expanding the latter removed liquid and introducing the same into an upper portion of said low pressure stage at least partly in liquid phase.

### Claim 11 (depends on 8)

Apparatus as claimed in claim 8, and means for supplying a portion of said ultra-high purity liquid nitrogen to the top of said low pressure stage as reflux.

### Claim 12 (depends on 8)

Apparatus as claimed in claim 8, and means for withdrawing gaseous nitrogen from the top of the high pressure stage, means for cooling and at least partially condensing the last-named nitrogen by heat exchange with said liquid ultra-high purity nitrogen, and means for introducing said at least partially condensed nitrogen into an upper portion of said high pressure stage.

### Claim 13 (depends on 8)

Apparatus as claimed in claim 8, and means for withdrawing gaseous nitrogen from the top of said high pressure stage, means for warming the thus-withdrawn nitrogen in heat exchange with feed air, means for expanding the thus-warmed nitrogen to the pressure of the low pressure stage, and means for introducing the thus-expanded nitrogen into the low pressure stage intermediate said height thereof.