Patent Application
20250003677
The present disclosure relates generally to purifying neon and, more particularly, to a cryogenic system for and method of purifying a feed including neon, nitrogen, and helium.
Neon is a rare gas in short supply. It is over 50 times more expensive than helium. It has several applications such as neon-helium lasers, as a critical component in krypton-argon lasers used to make semiconductor chips, and in cryogenic refrigeration. Neon is present in the air in small quantities. Most of the neon is produced by fractional cryogenic distillation of air. A conventional cryogenic air separation unit (ASU) may only produce a small stream enriched in neon, typically comprising neon, nitrogen, and helium. Additional steps are required to further concentrate and purify it.
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 cryogenic temperatures with nitrogen and helium separated by vapor-liquid equilibrium. The product is liquid neon 99.99% pure. The refrigeration for the process is partially supplied by isentropic (work) expansion of gaseous helium, the so-called reverse-Brayton cycle. One of the limitations of such a process is the availability and reliability of the machinery required such as helium expanders (turboexpanders or reciprocating expansion engines) and the helium recycle compressor, especially on a small scale. For example, U.S. Patent Publication 2014/0202174, discloses an example of a Gifford-McMahon cryocooler that may be used in such a process.
Therefore, there is a need for improved devices, systems, and methods to produce pure neon.
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.
In one aspect, a method of purifying a mixture including neon, nitrogen, and helium is provided. The method includes cooling the feed gas including neon, nitrogen, and helium in a heat exchange system to a first temperature to produce a two-phase mixture, introducing the two-phase mixture into a first phase separator to be separated into a nitrogen-rich liquid and a first gaseous crude neon stream, and reducing in pressure at least a portion of the nitrogen-rich liquid and vaporizing it in the heat exchange system to generate a portion of the refrigeration for the method. The method further includes introducing the first gaseous crude neon stream into a first adsorber that removes impurities such as nitrogen, further cooling the gaseous crude neon stream to a second temperature in such a manner that at least a portion of the cooling duty may come from the heat exchange system and another portion from a cryocooler to produce a two-phase stream, and separating the two-phase stream in a second phase separator into a crude helium vapor stream and a crude neon liquid stream. The method also includes 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 and 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.
In another aspect, a system for purifying neon is provided. The system includes a feed stream line configured to receive a gas mixture, wherein the gas mixture includes neon, nitrogen, and helium and a first heat exchanger configured to cool and/or heat the streams of the system. The system also includes a first separator in fluid communication with the feed stream line and wherein the separator is configured to separate the gas mixture to 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, wherein the adsorber receives the crude neon vapor stream from the first separator. Additionally, the system includes 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 the system includes 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.
In another aspect, a method of purifying neon is provided. The method includes cooling as gas mixture including 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, and purifying the crude neon vapor stream in a first adsorber. The method also includes cooling the crude neon steam 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Referring to
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.
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.
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.
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.
This application claims the benefit of U.S. Provisional Application No. 63/510,927, filed Jun. 29, 2023, the contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63510927 | Jun 2023 | US |
