Low temperature neon purification system and method

Abstract

A feed gas comprising neon, nitrogen and helium is cooled to a first temperature in a heat exchange system to produce a two-phase mixture, which is introduced into a first phase separator and separated into a nitrogen-rich liquid and a first gaseous crude neon stream. The pressure of at least a portion of the nitrogen-rich liquid is reduced, and the at least a portion of the nitrogen-rich liquid is vaporized in the heat exchange system to produce a portion of refrigeration therein. The first gaseous crude neon stream is introduced into a first adsorber which removes impurities such as nitrogen. The gaseous crude neon stream is further cooled to a second temperature. A portion of the cooling load may be from the heat exchange system and another portion may be from a cryogenic cooler to produce a two-phase flow. The two-phase stream is separated in a second phase separator into a crude helium vapor stream and a crude neon liquid stream, the crude neon liquid stream being introduced into a distillation column to produce a discharge stream containing helium impurities and a pure liquid neon product. The pure liquid neon product is vaporized in the heat exchange system to produce refrigeration and produce a pure gaseous neon product.

Description

[0001] Priority requirements

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 510,927, filed June 29, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to the purification of neon, and more specifically, to a cryogenic system and method for purifying a feed comprising neon, nitrogen and helium. Background Technology

[0004] Neon is a rare gas in high demand and short supply. It is more than 50 times more expensive than helium. It has various applications, such as neon-helium lasers, a key component in krypton-argon lasers used in the manufacture of semiconductor chips, and cryogenic refrigeration. Small amounts of neon exist in the air. Most neon is produced through staged cryogenic distillation of air. A typical cryogenic air separation unit (ASU) may only produce a small stream rich in neon, which typically contains neon, nitrogen, and helium. Additional steps are required for further concentration and purification.

[0005] A 2010 paper, “Purification and Liquefaction of Neon Using a Helium Refrigeration Cycle” (S. Boeck, “Purification and Liquefaction of Neon Using a Helium Refrigeration Cycle”, AIP Conference Proceedings 1218, 272-277 (2010)), describes the purification and liquefaction of a mixture of neon, nitrogen, and helium. The mixed feed is cooled to a cryogenic temperature, where nitrogen and helium are separated by gas-liquid equilibrium. The product is liquid neon with a purity of 99.99%. The refrigeration of the method is partially supplied by the isentropic (work) expansion of gaseous helium (i.e., the so-called reverse-Brayton cycle). One limitation of such methods is the availability and reliability of the required machinery, especially on a small scale, such as helium expanders (turbine expanders or reciprocating expanders) and helium cycle compressors. For example, U.S. Patent Publication 2014 / 0202174 discloses an example of a Gifford-McMahon cryocooler that can be used in such methods.

[0006] Therefore, there is a need for improved apparatus, systems, and methods for producing pure neon. Summary of the Invention

[0007] Several aspects of the subject matter of this invention may be individually or collectively embodied in the methods, apparatus, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the collective description of these aspects is not intended to exclude the use of these aspects alone or in different combinations set forth in the appended claims to claim such aspects.

[0008] In one aspect, a method for purifying a mixture comprising neon, nitrogen, and helium is provided. The method includes: cooling a feed gas comprising neon, nitrogen, and helium to a first temperature in a heat exchange system to generate a two-phase mixture; introducing the two-phase mixture into a first phase separator to separate it into a nitrogen-rich liquid and a first gaseous crude neon stream; and reducing the pressure of at least a portion of the nitrogen-rich liquid, and vaporizing the at least a portion of the nitrogen-rich liquid in the heat exchange system to generate a portion of the cooling for the method. The method further includes: introducing the first gaseous crude neon stream into a first adsorber, the first adsorber removing impurities such as nitrogen; further cooling the gaseous crude neon stream to a second temperature such that at least a portion of the cooling load can come from the heat exchange system and another portion from a cryogenic cooler to generate a two-phase flow; and separating the two-phase flow into a crude helium vapor stream and a crude neon liquid stream in a second phase separator. The method further includes: optionally reducing the pressure of the crude neon liquid stream, and then introducing the crude neon liquid stream into a distillation column to produce an exhaust stream containing helium impurities and a pure liquid neon product; and optionally reducing the pressure of the pure liquid neon product, and then vaporizing the pure liquid neon product in the heat exchange system to produce refrigeration and produce a pure gaseous neon product.

[0009] In another aspect, a system for purifying neon is provided. The system includes: a feed line configured to receive a gas mixture comprising neon, nitrogen, and helium; and a first heat exchanger configured to cool and / or heat the system stream. The system further includes a first separator in fluid communication with the feed line, configured to separate the gas mixture into a crude neon vapor stream and a nitrogen-rich liquid stream. The system also includes a first adsorber in fluid communication with the first separator, receiving the crude neon vapor stream from the first separator. Additionally, the system includes a second separator in fluid communication with the first adsorber, configured to separate the stream from the first adsorber into a crude helium vapor stream and a crude neon liquid stream, and the system includes a distillation column in fluid communication with the second separator, receiving the crude neon liquid stream and configured to purify the crude neon liquid stream into a pure neon liquid product.

[0010] In another aspect, a method for purifying neon is provided. The method includes: cooling a gas mixture comprising neon, nitrogen, and helium to a first temperature in a heat exchange system; separating the mixture into a nitrogen-rich liquid stream and a crude neon vapor stream in a first separator; and purifying the crude neon vapor stream in a first adsorber. The method further includes: cooling the crude neon vapor to a second temperature; separating the crude neon stream into a crude helium vapor stream and a crude neon liquid stream in a second separator; and purifying the crude neon liquid stream into a purified neon product stream in a distillation column. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of an embodiment of the neon purification system disclosed herein. Detailed Implementation

[0012] A more detailed description of the systems and methods according to this disclosure is set forth below. It should be understood that the following description of specific systems and methods is intended to be exemplary and not to exhaustively cover all possible variations or applications. Therefore, the scope of this disclosure is not intended to be limiting and should be understood to cover various variations or embodiments that may be conceived by one of ordinary skill in the art.

[0013] It should be noted that the pipelines, conduits, pipes, channels and similar structures shown in the figure, as well as the corresponding flows, are sometimes referred to by the same component number.

[0014] The term “tower” as used below refers to a distillation, fractionation, or rectification tower, including contact towers or contact zones, in which countercurrent liquid and gas phases are brought into contact to cause separation of the fluid mixture, such as by bringing the gas and liquid phases into contact on a series of vertically spaced plates, trays, or packing located within the tower.

[0015] Furthermore, as used herein and as is known in the art, a heat exchanger is a device or region within a device in which indirect heat exchange occurs between two or more streams at different temperatures or between a stream and the environment. Additionally, all heat exchangers mentioned herein may be incorporated into one or more heat exchanger units, or may each be a separate heat exchanger unit. As used herein, the terms “communication,” “communicating,” etc., generally refer to fluid communication unless otherwise stated. And although two communicating fluids may exchange heat upon mixing, such exchange is not considered the same as heat exchange in a heat exchanger, although such exchange can occur in a heat exchanger.

[0016] To provide context for other features, reference numerals introduced in the specification and associated with the drawings may be repeated in one or more subsequent figures to share elements or components without further description in the specification.

[0017] In the claims, letters are used to identify the steps of the claim (e.g., a., b., and c.). These letters are used to help refer to the method steps, not to indicate the order in which the steps of the claim are performed, unless such order is specifically stated in the claim and only to the extent that such order is specifically stated in the claim.

[0018] Figure 1 An embodiment of a neon purification system, generally indicated by 10, is shown. According to the embodiment, the feed gas stream 100 can be cooled in a heat exchanger 105. In the embodiment, the feed gas stream is a gas that may include neon. For example, the feed gas stream may include neon, nitrogen, and helium. The heat exchanger 105 may be a brazed aluminum heat exchanger (BAHX). Other heat exchangers known in the art may be used without departing from the scope of this disclosure. After passing through the heat exchanger 105, the pressure of the resulting two-phase flow 110 may optionally be reduced in a valve 111 to produce a separated flow 112 in a separator 120. For example, the separator 120 may be a separation vessel. Within the separator 120, the two-phase flow 112 is separated into a gaseous crude neon flow 130 and a nitrogen-rich liquid flow 200. In the embodiment, the pressure of the nitrogen-rich liquid flow 200 may be reduced in a valve, such as a Joule-Thomson (“JT”) valve 205. After the pressure is reduced, the flow 210 may be vaporized in the heat exchanger 105 to provide a portion of the cooling for the system 10. For example, the nitrogen-rich stream can be heated to near ambient temperature. In this embodiment, the nitrogen-rich stream 210 can be supplemented by the input liquid nitrogen stream 122.

[0019] After separation in separator 120, the gaseous crude neon stream 130 can exit the separator and be introduced into adsorber 135. In an embodiment, adsorber 135 is a cryogenic adsorber configured to remove impurities (e.g., primarily nitrogen). In an embodiment, adsorber 135 can use a molecular sieve. Molecular adsorber 135 can be similar to the “80K” adsorber used in the helium and hydrogen industry. Other adsorbers known in the art can be used without departing from the scope of this disclosure. After adsorption, the purified stream 140, which may contain only neon and helium, can exit adsorber 135 and can then be further cooled in heat exchanger 143. In an embodiment, heat exchanger 143 can be similar to heat exchanger 105, for example, heat exchanger 143 can be BAHX. It will be apparent to those skilled in the art that heat exchangers 105 and 143 can be combined into a single heat exchanger with multiple nozzles and end caps.

[0020] After passing through heat exchanger 143, the resulting two-phase flow 145 can be introduced into phase separator 147. In an embodiment, additional cooling can be supplied by a cryogenic cooler 148 associated with separator 147. For example, the cold head (cooling element) of the cooling element (so-called cold head) 148 of the cryogenic cooler can be placed inside phase separator 147 to provide additional condensation of residual vapor. It will be apparent to those skilled in the art that multiple phase separators and / or cryogenic coolers can be present in series or in parallel. In an embodiment, cryogenic cooler 148 can be a Gifford-McMahon cryogenic cooler. It will be apparent to those skilled in the art that other devices and cooling sources (e.g., Sterling engine type) can be used instead of Gifford-McMahon cryogenic coolers.

[0021] A crude helium stream 300, which comprises primarily helium and includes some neon, is removed from phase separator 147. In an embodiment, the crude helium stream can be purified in adsorber 303 to remove neon. Such adsorbers can be similar to "20K" adsorbers used in the helium industry and can contain activated carbon. The resulting stream 305 is heated in heat exchangers 143 and 120 to produce a helium product stream 320. For example, the purified helium stream 305 can be first heated through heat exchanger 143. Then, the heated helium stream 310 can be reheated through heat exchanger 105. In an embodiment, the helium product stream 320 can be collected.

[0022] Liquid stream 150 may primarily consist of neon but may still contain some helium impurities. After separation, the pressure of liquid stream 150 can be reduced in a valve (e.g., “JT” valve 153) and then introduced to the top of distillation column 157. In an embodiment, the column may be a packed column with five theoretical stages. Column 157 may discharge the remaining helium through stream 400. After distillation, stream 400 may subsequently be warmed in heat exchangers 143 and 120 to produce exhaust stream 420. For example, stream 400 may first be warmed through heat exchanger 143. Then, the warmed stream 410 may be further warmed through heat exchanger 105.

[0023] The bottom product of column 157 is stream 160. In an embodiment, bottom product stream 160 comprises more than 99.99 mol% neon. Optionally, the pressure of the bottom product stream can be reduced in valve 161 to produce stream 162. Stream 162 is then vaporized and warmed in heat exchangers 143 and 105 to produce a pure neon product stream 166 at or above atmospheric pressure. For example, the purified neon stream 162 can be warmed first through heat exchanger 143. Then, the warmed neon stream 164 can be further warmed through heat exchanger 105. Neon product stream 166 can be further compressed, for example, for tube trailer loading. In an embodiment, neon product stream 166 can be collected.

[0024] Boiling (steam flow rate) in tower 157 is typically provided by an electric heating coil or heating element at the bottom. It can also be provided, for example, by direct or indirect heat exchange with a portion of stream 140.

[0025] Therefore, the cooling of the entire method comes in part from the vaporization of streams 210 and 162, a so-called open-loop reverse Rankine cycle or vapor compression cycle, with additional cooling from a supplemental liquid nitrogen stream 122 (if present) and a cryogenic cooler, which also helps ensure a positive temperature difference at the cold end of heat exchanger 143. Pressure energy comes from feed stream 100, which can be further compressed if necessary.

[0026] Phase separator 120 can be replaced by a distillation column similar to column 157. Conversely, distillation column 157 can be replaced by a phase separator, which may have a heat source, such as an electrical coil, to help remove helium.

[0027] In the embodiments, unless otherwise stated, the lines / flows are in fluid communication with each other and with other components such as separators, adsors, valves and towers.

[0028] Example

[0029] refer to Figure 1 A mixture (stream 100) containing 15 mol% helium, 30 mol% nitrogen, and 55% neon at 100 °F and 195 psia is cooled to -335.4 °F (70 K) at 5 lbmol / hr in heat exchanger 105. The mixture is separated into a nitrogen-rich stream 200 and a vapor stream 130, the nitrogen-rich stream containing 94 mol% nitrogen, the balance being neon and helium, and the vapor stream containing 75 mol% neon, 3.5 mol% nitrogen, and the balance being helium. Stream 200 is throttled to 17 psia in “JT” valve 205 and vaporized in heat exchanger 105. A small supplemental liquid nitrogen stream 122 of approximately 0.1 lbmol / hr can be introduced.

[0030] Stream 130 enters adsorber 135, where nitrogen is removed. The resulting stream 140 is a mixture containing 78 mol% neon and the balance helium. The mixture is cooled in heat exchanger 143 to produce a two-phase stream 145 at -406.0 °F. Stream 134 is introduced into phase separator 147, which has a cold head (optionally having an enlarged surface area) of cryogenic cooler 148 placed in the vapor space of separator 147. Cryogenic cooler 148 provides additional cooling down to -420.4 °F (21.8 K). A vapor stream 300 containing 98 mol% helium and 2 mol% neon is purified in adsorber 303 to produce a pure helium product, which is warmed in two heat exchangers 143 and 105.

[0031] A liquid stream 150 containing 99.95 mol% neon and the balance helium is throttled to 17 psia and introduced into the top of distillation column 157. The exhaust stream 400 from the top of the column contains 97.5% neon and the balance helium is warmed in two heat exchangers. A liquid stream 160 at -410.0 °F is 99.999 mol% neon. Optionally, the pressure of the liquid stream is reduced to 16.7 psia in valve 161 and vaporized and warmed in two heat exchangers 143 and 105 to produce a pure neon product stream 166 at 14.7 psia.

[0032] Several aspects of the subject matter of this invention may be individually or collectively embodied in the methods, apparatus, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the collective description of these aspects is not intended to exclude the use of these aspects alone or in different combinations set forth in the appended claims to claim such aspects.

[0033] While preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications and changes may be made therein without departing from the spirit of the invention as defined by the appended claims.

Claims

1. A method for purifying a mixture containing neon, nitrogen, and helium, the method comprising the following steps: (a) In a heat exchange system, a feed gas containing neon, nitrogen and helium is cooled to a first temperature to produce a two-phase mixture; (b) Optionally reduce the pressure and then introduce the two-phase mixture into a first-phase separator to separate it into a nitrogen-rich liquid and a first gaseous crude neon stream; (c) Reduce the pressure of at least a portion of the nitrogen-rich liquid and vaporize the at least a portion of the nitrogen-rich liquid in the heat exchange system to generate a portion of the cooling for the method; (d) The first gaseous crude neon stream is introduced into the first adsorber, which removes impurities such as nitrogen; (e) Further cooling the gaseous crude neon stream to a second temperature such that at least a portion of the cooling load comes from the heat exchange system to generate a two-phase flow; (f) The two-phase flow is separated into a crude helium vapor flow and a crude neon liquid flow in a second-phase separator; (g) Optionally reduce the pressure of the crude neon liquid stream and then introduce the crude neon liquid stream into a distillation column to produce an exhaust stream containing helium impurities and a pure neon product; (h) Optionally reduce the pressure of the pure liquid neon product and then vaporize the pure liquid neon product in the heat exchange system to generate cooling and produce pure gaseous neon product.

2. The method according to claim 1, wherein the cooling load in the additional portion of step (e) comes from another refrigeration unit.

3. The method according to claim 2, wherein the cryogenic cooler head is placed inside the second phase separator.

4. The method of claim 2, comprising a plurality of cryogenic coolers connected in series and in parallel.

5. The method according to claim 1, wherein the crude helium vapor stream of step (f) is purified in a second adsorber to remove neon.

6. The method of claim 1, wherein the nitrogen-rich liquid in step (c) is replenished by an additional input liquid nitrogen.

7. The method of claim 1, wherein the feed gas is compressed before cooling.

8. A system for purifying neon, the system comprising: A feed line configured to receive a gas mixture comprising neon, nitrogen, and helium; A first heat exchanger is configured to cool and / or heat the flow of the system; A first separator is in fluid communication with the feed line, and wherein the separator is configured to separate the mixed gas mixture into a coarse neon vapor stream and a nitrogen-rich liquid stream. A first adsorber is in fluid communication with a first separator, wherein the adsorber receives the crude neon vapor stream from the first separator; A second separator is in fluid communication with the first adsorber, wherein the second separator is configured to separate the stream from the first adsorber into a crude helium vapor stream and a crude neon liquid stream; as well as A distillation column, which is in fluid communication with the second separator, wherein the distillation column receives the crude neon liquid stream and is configured to purify the crude neon liquid stream into a pure neon liquid product.

9. The system of claim 8, wherein the nitrogen-rich liquid stream is used to cool the system.

10. The system according to any one of claims 8 and 9, further comprising an input stream of liquid nitrogen.

11. The system according to any one of claims 8 to 10, further comprising a second heat exchanger.

12. The system according to any one of claims 8 to 11, wherein the second separator is associated with a cryogenic cooler.

13. The system of claim 12, wherein the cryogenic cooler is placed inside the second separator.

14. The system according to any one of claims 12 and 13, wherein the cryocooler is a Gifford-McMahon cryocooler.

15. The system according to any one of claims 8 to 14, comprising a second adsorber in fluid communication with the second separator, wherein the second adsorber receives the crude helium vapor from the second separator.

16. A method for purifying neon, the method comprising the following steps: A gas mixture containing neon, nitrogen, and helium is cooled to a first temperature in a heat exchange system; The mixture is separated into a nitrogen-rich liquid stream and a crude neon vapor stream in a first separator; The crude neon vapor stream is purified in the first adsorber. The coarse neon stream is cooled to a second temperature; In the second separator, the crude neon stream is separated into a crude helium vapor stream and a crude neon liquid stream; and The crude neon liquid stream is purified into a purified neon product stream in a distillation column.

17. The method of claim 16, further comprising the steps of: reducing the pressure of the nitrogen-rich liquid stream and vaporizing the nitrogen-rich liquid stream in the heat exchange system to generate a portion of the cooling for the system.

18. The method according to any one of claims 16 and 17, further comprising the step of introducing an input stream of liquid nitrogen into the heat exchange system to generate a portion of cooling for the system.

19. The method according to any one of claims 16 to 18, wherein the first adsorber is configured to remove nitrogen.

20. The method of claims 16 to 19, further comprising the step of cooling the second two-phase flow with a cryogenic cooler associated with the second separator.

21. The method of claim 20, wherein the cryogenic cooler is located within the second separator.

22. The method according to any one of claims 20 and 21, wherein the cryogenic cooler is a Gifford-McMahon cryogenic cooler.

23. The method according to any one of claims 16 to 22, further comprising the step of purifying the crude helium vapor stream in a second adsorber.

24. The method of claim 23, further comprising the step of vaporizing the purified helium stream to produce a purified helium product.

25. The method according to any one of claims 16 to 24, further comprising the step of reducing the pressure of the crude neon liquid stream before it enters the distillation column.

26. The method according to any one of claims 16 to 25, wherein the distillation column separates the nitrogen liquid from the helium impurities.

27. The method of claim 26, further comprising the step of discharging the helium impurity.

28. The method according to any one of claims 16 to 27, further comprising the step of heating the helium impurity in the heat exchange system.

29. The method according to any one of claims 16 to 28, further comprising the step of reducing the pressure of the purified neon product stream.

30. The method according to any one of claims 16 to 29, further comprising the step of warming the purified neon product stream.

31. The method according to any one of claims 16 to 30, further comprising the step of collecting the purified neon product stream.

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