Cryogenic Neon Purification System and Method

Abstract

A feed gas including neon, nitrogen, and helium is cooled in a heat exchange system to a first temperature to produce a two-phase mixture that is introduced into a first phase separator and separated into a nitrogen-rich liquid and a first gaseous crude neon stream. The pressure is reduced in at least a portion of the nitrogen-rich liquid, which is vaporized in the heat exchange system to generate a portion of the refrigeration therein. The first gaseous crude neon stream is introduced into a first adsorber that removes impurities such as nitrogen. The gaseous crude neon stream is further cooled to a second temperature. A portion of the cooling duty may come from the heat exchange system and another portion may come from a cryocooler to produce a two-phase stream. The two-phase stream is separated in a second phase separator into a crude helium vapor stream and a crude neon liquid stream with the latter being introduced into a distillation column to produce a vent stream containing a helium impurity and a pure liquid neon product. The pure liquid neon product is vaporized in the heat exchange system to generate refrigeration and produce the pure gaseous neon product.

Claims

1. A method of purifying a mixture comprising neon, nitrogen, and helium comprising the steps of: (a) cooling the feed gas comprising neon, nitrogen, and helium in a heat exchange system to the first temperature to produce a two-phase mixture; (b) optionally reducing in pressure and then introducing the two-phase mixture into the first phase separator to be separated into a nitrogen-rich liquid and the first gaseous crude neon stream; (c) reducing in pressure at least a portion of the nitrogen-rich liquid and vaporing it in the heat exchange system to generate a portion of the refrigeration for the process; (d) introducing the first gaseous crude neon stream into the first adsorber that removes impurities such as nitrogen; (e) further cooling the gaseous crude neon stream to the second temperature in such a manner that at least a portion of the cooling duty comes from the heat exchange system to produce a two-phase stream; (f) separating the two-phase stream in a second phase separator into a crude helium vapor stream and a crude neon liquid stream; (g) optionally reducing in pressure the crude neon liquid stream and then introducing it into a distillation column to produce a vent stream containing a helium impurity and a pure liquid neon product; (h) optionally reducing in pressure of the pure liquid neon product and then vaporizing it in the heat exchange system to generate refrigeration and produce the pure gaseous neon product.

2. The method of claim 1 where an additional portion of the cooling duty in step (e) comes from another refrigeration device.

3. The method of claim 2 where the cryocooler cold head is placed inside of the second phase separator.

4. The method of claim 2 comprising multiple cryocoolers present in series and in parallel.

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

6. The method of claim 1 where the nitrogen-rich liquid in step (c) is supplemented by an additional liquid nitrogen import.

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

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

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

10. The system of claim 8, further comprising an imported liquid nitrogen stream.

11. The system of claim 8, further comprising a second heat exchanger.

12. The system of claim 8, wherein the second separator is associated with a cryocooler.

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

14. The system of claim 12, wherein the cryocooler is a Gifford-McMahon cryocooler.

15. The system of claim 8, 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 of purifying neon comprising the steps of: cooling a gas mixture comprising neon, nitrogen, and helium in a heat exchange system to a first temperature; separating the mixture in a first separator into a nitrogen-rich liquid stream and a crude neon vapor stream; purifying the crude neon vapor stream in a first adsorber; cooling the crude neon stream to a second temperature; separating the crude neon stream in a second separator into a crude helium vapor stream and a crude neon liquid stream; and purifying the crude neon liquid stream in a distillation column to a purified neon product stream.

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

18. The method of claim 16 further comprising the step of introducing an imported liquid nitrogen stream to the heat exchange system to generate a portion of the refrigeration for the system.

19. The method of claim 16, wherein the first adsorber is configured to remove nitrogen.

20. The method of claim 16 further comprising the step of cooling the second two-phase stream with a cryocooler associated with the second separator.

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

22. The method of claim 20, wherein the cryocooler is a Gifford-McMahon cryocooler.

23. The method of claim 16 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 create a purified helium product.

25. The method of claim 16 further comprising the step of decreasing the pressure of the crude neon liquid stream before entering the distillation column.

26. The method of claim 16, wherein the distillation column separates nitrogen liquid from helium impurities.

27. The method of claim 26, further comprising the step of venting the helium impurities.

28. The method of claim 16, further comprising the step of heating the helium impurities in the heat exchange system.

29. The method of claim 16 further comprising the step of reducing the pressure of the purified neon product stream.

30. The method of claim 16 further comprising the step of warming the purified neon product stream.

31. The method of claim 16 further comprising the step of collecting the purified neon product stream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic illustration of an embodiment of a neon purification system of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0011] A more detailed description of the system and method in accordance with the present disclosure is set forth below. It should be understood that the description below of specific systems and methods is intended to be exemplary, and not exhaustive of all possible variations or applications. Thus, the scope of the disclosure is not intended to be limiting and should be understood to encompass variations or embodiments that would occur to persons of ordinary skill.

[0012] It should be noted herein that the lines, conduits, piping, passages and similar structures and the corresponding streams are sometimes both referred to by the same element number set out in the figures.

[0013] The term column as used below means a distillation, fractionation or rectification column including a contacting column or zone wherein countercurrent liquid and vapor phases are contacted to cause separation of a fluid mixture such as by contacting the vapor and liquid phases on a series of vertically spaced plates or trays or packing material positioned within the column.

[0014] Also, as used herein, and as known in the art, a heat exchanger is that device or an area in the device wherein indirect heat exchange occurs between two or more streams at different temperatures, or between a stream and the environment. In addition, all heat exchangers referenced herein may be incorporated into one or more heat exchanger devices or may each be individual heat exchanger devices. As used herein, the terms communication, communicating, and the like generally refer to fluid communication unless otherwise specified. And although two fluids in communication may exchange heat upon mixing, such an exchange would not be considered to be the same as heat exchange in a heat exchanger, although such an exchange can take place in a heat exchanger.

[0015] Reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures for shared elements or components without additional description in the specification in order to provide context for other features.

[0016] In the claims, letters are used to identify claimed steps (e.g. a., b. and c.). These letters are used to aid in referring to the method steps and are not intended to indicate the order in which the claimed steps are performed, unless and only to the extent that such order is specifically recited in the claims.

[0017] FIG. 1 shows an embodiment of a neon purification system, indicated in general at 10. According to an embodiment, a feed gas stream 100 may be cooled in heat exchanger 105. In an embodiment the feed gas stream is a gas that may include neon. For instance, the feed gas stream may include neon, nitrogen, and helium. 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 the disclosure. After traveling through the heat exchanger 105, the resulting two-phase stream 110 may be optionally reduced in pressure in valve 111 to produce stream 112 which is separated in a separator 120. For example, separator 120 can be a separation vessel. Within separator 120, the two-phase stream 112 is separated into a gaseous crude neon stream 130 and a nitrogen-rich liquid stream 200. In an embodiment, nitrogen-rich liquid stream 200 may be reduced in pressure in a valve, for example, in a Joule-Thomson (JT) valve 205. After being reduced in pressure, stream 210 can be vaporized in heat exchanger 105 to provide a portion of refrigeration for the system 10. For instance, the nitrogen-rich stream is warmed to the approach to ambient temperature. In an embodiment, nitrogen-rich stream 210 may be supplemented by an imported liquid nitrogen stream 122.

[0018] After separation in separator 120, gaseous crude neon stream 130 may exit the separator and be introduced to an adsorber 135. In an embodiment, the adsorber 135 is cryogenic adsorber configured to remove impurities, for instance, mainly nitrogen. In an embodiment, the adsorber 135 may use molecular sieves. The molecular adsorber 135 may be similar to 80K adsorbers used in the helium and hydrogen industry. Other adsorbers known in the art may be used without departing from the scope of the disclosure. After adsorption, a purified stream 140, which may contain only neon and helium, may exit adsorber 135 and may then be further cooled in a heat exchanger 143. In an embodiment, heat exchanger 143 can be similar to heat exchanger 105, for instance heat exchanger 143 may be a BAHX. It should be apparent to one skilled in the art that the heat exchangers 105 and 143 can be combined into one heat exchanger, with multiple nozzles and headers.

[0019] After traveling through heat exchanger 143, resulting two-phase stream 145 may be introduced into the phase separator 147. In an embodiment, additional refrigeration may be supplied by a cryocooler 148 associated with separator 147. For example, the cold head (cooling element) of cryocooler's cooling element (so-called cold head) 148 may be placed inside of the phase separator 147 to provide additional condensation of the remaining vapor. It should be apparent to one skilled in the art that there may be multiple phase separators and/or cryocoolers in series or in parallel. In an embodiment, the cryocooler 148 can be a Gifford-McMahon cryocooler. It should be apparent to one skilled in the art that other devices and sources of refrigeration, for example, Sterling engine type, can be used in place of the Gifford-McMahon cryocooler.

[0020] Crude helium stream 300 including mostly helium and some neon is removed from the phase separator 147. In an embodiment, it may be purified in the adsorber 303 to remove neon. Such adsorbers may be similar to 20K adsorbers used in the helium industry and may contain activated carbon. The resulting stream 305 is warmed in heat exchangers 143 and 120 to produce helium product stream 320. For example, a purified helium stream 305 may be first warmed by heat exchanger 143. Warmed helium stream 310 may then be warmed again by heat exchanger 105. In an embodiment, helium product stream 320 may be collected.

[0021] The liquid stream 150 may include mostly neon, but still with some helium impurity. After separation, liquid stream 150 may be reduced in pressure in a valve, for instance, a JT valve 153 and may then be introduced to the top of the distillation column 157. In an embodiment, the column may be a packed type with five theoretical stages. The column 157 may reject the remainder of helium via stream 400. After distillation, stream 400 may be subsequently warmed in heat exchangers 143 and 120 to produce vent stream 420. For example, stream 400 may be first warmed by heat exchanger 143. Warmed stream 410 may then be warmed again by heat exchanger 105.

[0022] The column's 157 bottom product is stream 160. In an embodiment, the bottom product stream 160 includes greater than 99.99 mol % neon. It may be optionally reduced in pressure in valve 161 to produce stream 162. Stream 162 is subsequently vaporized and warmed in heat exchangers 143 and 105 to produce the pure neon product stream 166, at or above atmospheric pressure. For example, a purified neon stream 162 may be first warmed by heat exchanger 143. Warmed neon stream 164 may then be warmed again by heat exchanger 105. Neon product stream 166 can be further compressed, for example for tube trailer loading. In an embodiment, neon product stream 166 may be collected.

[0023] Boil-up (vapor traffic) for the column 157 is normally provided by an electrical heating coil or heating element on the bottom. It can also be provided by direct or indirect heat exchange, for example with a portion of stream 140.

[0024] Thus, the refrigeration for the entire process comes partially from vaporizing streams 210 and 162, the so-called open-loop reverse-Rankine cycle or vapor compression cycle, with additional refrigeration coming from supplemental liquid nitrogen stream 122 (if any), and the cryocooler that also helps assure a positive temperature difference at the cold end of the heat exchanger 143. The pressure energy comes from feed stream 100 which may be additionally compressed if needed.

[0025] Phase separator 120 can be replaced with a distillation column similar to column 157. Conversely, distillation column 157 could be replaced with a phase separator, possibly with a source of heat such as an electrical coil to help reject helium.

[0026] In an embodiment, the lines/streams are in fluid communication with one another, as well as with the other components, such as separators, adsorbers, valves, and columns unless otherwise stated.

EXAMPLE

[0027] Referring to FIG. 1, 5 lbmol/hr or a mixture containing 15 mol % of helium, 30 mol % of nitrogen, and 55% of neon at 100 F. and 195 psia (stream 100) is cooled in the heat exchanger 105 to 335.4 F. (70 K). The mixture is separated into nitrogen-rich stream 200 containing 94 mol % of nitrogen, balance neon, and helium, and vapor stream 130 containing 75 mol % neon, 3.5 mol % nitrogen, and balance helium. Stream 200 is throttled to 17 psia in a JT valve 205 and vaporized in the heat exchanger 105. A small supplemental liquid nitrogen stream 122, of the order of 0.1 lbmol/hr, may be imported.

[0028] Stream 130 enters adsorber 135 where nitrogen is removed. The resulting stream 140 is a mixture containing 78 mol % neon and balance helium. It is cooled in the heat exchanger 143 to produce a two-phase stream 145 at 406.0 F. Stream 134 is introduced to the phase separator 147 with the cold head of the cryocooler 148, optionally with an extended surface area, placed in the vapor space of the separator 147. The cryocooler 148 provides additional refrigeration down to 420.4 F. (21.8 K). Vapor stream 300 containing 98 mol % helium and 2 mol % neon is purified in the adsorber 303 to produce pure helium product that is warmed up in the two heat exchangers 143 and 105.

[0029] Liquid stream 150 containing 99.95 mol % neon and a balance of helium is throttled to 17 psia and introduced to the top of the distillation column 157. Vent stream 400 from the top of the column contains 97.5% neon and balance helium is warmed up in the two heat exchangers. Liquid stream 160 at 410.0 F. is 99.999 mol % neon. It is optionally reduced in pressure to 16.7 psia in valve 161 and vaporized and warmed in the two heat exchangers 143 and 105 to produce pure neon product stream 166 at 14.7 psia.

[0030] There are several aspects of the present subject matter which may be embodied separately or together in the methods, devices, and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto.

[0031] While the preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.