JPS62102075A - Manufacture of krypton-xenon concentrate and gassy oxygen product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a krypton-xenon concentrate, and more particularly, a method for producing a krypton-xenon concentrate with high efficiency and also producing a gaseous oxygen product substantially free of rare earth gases. Regarding improvement methods such as

Krypton and xenon are in increasing demand for many applications. Krypton is widely used in high-quality lighting equipment, including long-life lamps and automotive lamps. Xenon is used in medical applications, including special x-ray equipment.

Both of these gases are commonly used in many experimental and research applications.

The main source of krypton and xenon is the atmosphere.

Atmospheric air contains about 11 ppm of krypton and about 1
Contains 0.8 ppm of xenon. Generally, krypton and xenon are recovered from air in connection with an integrated air separation process that separates air into oxygen and nitrogen.

Due to the low vapor pressure of krypton and xenon, these gases concentrate in oxygen rather than nitrogen during air separation. Concentration of atmospheric krypton and xenon in oxygen increases their concentration by a factor of five, since oxygen makes up only about -1 of atmospheric air. It is desirable to further concentrate krypton and xenon so that they can be efficiently recovered in rare earth gas recovery equipment.

It is generally desired to produce gaseous oxygen from an air separation process. As mentioned above, krypton and xenon condense in oxygen. Therefore, in order to produce a gaseous oxygen product and further concentrate the krypton and xenon, the entire amount of gaseous oxygen must be sent through the enrichment process. A typical enrichment process includes
Stripping towers are involved. Since the entire gaseous oxygen product must be passed through the stripping column, the stripping column must be relatively large. Additionally, the oxygen passing through the stripping column undergoes a pressure drop, which adds costly compression if high pressure of the oxygen product is desired. This is expensive both in terms of invested capital and operating costs.

Therefore, it would be highly desirable to have a krypton-xenon enrichment process that produces gaseous oxygen but can use significantly smaller stripping columns than previously thought necessary in conventional processes.

It is therefore an object of the present invention to provide an improved process for producing krypton-xenon concentrates.

It is another object of the present invention to provide an improved process for producing krypton-xenon concentrates while also producing gaseous oxygen products that are substantially free of rare earth gases.

Yet another object of the invention is to
It is an object of the present invention to provide an improved method for producing krypton-xenon concentrate and gaseous oxygen products using a significantly smaller IJ tower.

SUMMARY OF THE INVENTION The foregoing objects and other objects which will be apparent to those skilled in the art upon reading this specification provide a method for the production of krypton-xenon concentrates and the recovery of gaseous products substantially free of rare earth gases. 1) feeding a feedstock liquid containing oxygen, krypton, and xenon to a reboil zone to form a reboil liquid; and 2) partially vaporizing the reboil liquid to form a vapor and liquid krypton-xenon concentrate. 3) recovering a krypton-xenon concentrate; 4) introducing into a stripping column a reflux liquid having a lower concentration of krypton-xenon than in said vapor; and 5) producing a reflux stream downstream in the stripping column. 6) stripping the krypton and xenon from the vapor into a reflux liquid to produce a lean vapor and a richer liquid; 7) producing a lean vapor and a richer liquid; 8) extracting lean vapor from the stripping column to form a portion of the reboiling liquid; and 9) recovering the extracted lean vapor as a gaseous product substantially free of rare earth gases. , a method comprising: .

The term "rare earth gas J" as used herein means krypton and xenon.

As used herein, the terms "lean,""lean,""rich," and "rich" refer to concentrations of rare earth gases, unless otherwise specified.

As used herein, the term "reboil zone" refers to a heat exchange zone in which incoming liquid is indirectly heated and thereby partially vaporized to produce gas and residual liquid.

This enriches the residual liquid in the less volatile components present in the incoming liquid.

As used herein, the term "indirect heat exchange" means - bringing two fluid streams into a heat exchange relationship without physically contacting or mixing with each other.

As used herein, the term "equilibrium stage" refers to a gas-liquid contacting stage in which the vapor and liquid exiting the gas-liquid contacting stage are in mass transfer equilibrium.

For separation columns that use trays or plates, ie separate contact stages, for the liquid and gas phases, the equilibrium stage corresponds to the theoretical tray or plate.

For separation columns that use banking or continuous contact of liquid and gas phases, the equilibration stage corresponds to that height of the column backing that is equal to one theoretical plate. The actual contact stage @ tray, plate or backing corresponds to the equilibrium stage depending on its mass transfer efficiency.

As used herein, the term "column" refers to a distillation or fractionation column, i.e., on a series of vertically disjoint trays or plates disposed within the column, or alternatively on backing members packed into the column. means a contacting column or zone in which separation of a fluid mixture is effected by contacting the liquid and gas phases countercurrently, such as by contacting the gas and liquid phases at a temperature. For details and a detailed explanation of the separation tower, please refer to the board collection by R.H. Berry and C.H. Chilton, “The Chemical Engineers
ngineer's Handbook), 5th edition"
(McGraw-Hill Book Cover, New York, USA), °Destillation (DIstIll)
atlon)”, B.D. Smith surname, No. 13
Page 3, The Continuous Proboscis Testillation Process
tion Process).

The term "double column" as used herein means a high pressure column having an upper end in heat exchange relationship with the lower end of the lower pressure column. For a detailed explanation of the double tower, see Mr. Luchmann's “The Separation of Gases”.
on of Gaaea” (Oxford).

University Press, 1949), Chapter ■, “
Architectural Air Separation° and Mr. Baron's “CryogenIc Systems”
” (McGraw-Hill Incorporated, 196
6), page 230, “Air Separation Thread°”.

DETAILED DESCRIPTION The method of the invention will now be described in detail with reference to the accompanying drawings.

Referring to FIG.
It is introduced into a high pressure column 19 operating at a pressure in the range of 5x150 psia (1). Other steps such as cooling and purification steps and heat exchange with the return stream are not illustrated in FIG. This is because such process steps are well known and conventional and do not form part of the present invention.

In the high pressure column 19, the feed air is a nitrogen-rich vapor 2
3 and an oxygen-enriched liquid 20.

Liquid 20 is expanded by valve 21 and feedstock 22
It is introduced into the low pressure column 17 as a liquid. This low pressure column 17 has 1
5-100 pafa preferably ii: 15-30 pa
It is operated at pressures within the range of fa.

Nitrogen-rich vapor 26 is sent via line 24 to condenser 18 where it is condensed by indirect heat exchange with reboil liquid from the bottom of low pressure column 17. The resulting condensed nitrogen-rich stream 60 is combined into stream 26 (which is expanded by valve 30 and sent as reflux to column 17 as stream 31) and stream 27 (which is sent as reflux to column 19). sent) and divided into

FIG. 1 also illustrates a low pressure feed air stream 13 to column 17. This air stream 13 may be obtained from the warm end of the air separation process, such as from a refrigeration deployment of the plant. Within column 17, each inlet stream is separated by cryogenic rectification to produce nitrogen stream 14 and an oxygen product.

Nitrogen stream 14 can be recovered in whole or in part, or can be vented to the atmosphere.

As previously noted, substantially all of the krypton and xenon in the feed air is concentrated in oxygen rather than in nitrogen. FIG. 1 shows that the krypton and xenon in the oxygen can be further concentrated in the liquid oxygen portion, thereby recovering most of the oxygen directly from column 17 as a gaseous phosphorus product that is relatively free of rare earth gases. A particularly preferable specific example that makes it possible will be exemplified below. this is,
Gaseous oxygen is removed from the column 17 at least one, preferably at least two equilibration stages or indeed above the trays, from the sump of the column 17 in which the bottom liquid is reboiled against condensable nitrogen in the condenser 18. This is accomplished by drawing off as stream 37.

In FIG. 1, tray 32 is the bottom tray and tray 32 is the bottom tray.
3 is the next higher tray and tray 54 is the third tray in the order.

As will be appreciated, oxygen product stream 37 is withdrawn between trays 33 and 34. In this manner, since krypton and xenon both have lower vapor pressures than oxygen, most of the krypton and xenon are carried into the liquid enzyme and into the reservoir, thus producing a stream relatively free of rare earth gases. 37 flows out.

As previously mentioned, the majority of the krypton and xenon in the feed is contained in the liquid in the column 17 sump.

This liquid is an ideal source of feedstock for the krypton-xenon enrichment process of the present invention.

Referring again to FIG. 1, liquid stream 36 containing oxygen, krypton and xenon is delivered to reboil zone 44 to form reboil liquid 61. Referring again to FIG. Reboiling zone 44 may be separate from stripping column 38 or within it. The concentration of krypton and xenon in the feed liquid, such as stream 36, may be any effective concentration, but generally the concentration of krypton in the liquid feed stream will be at least 10 ppm, preferably at least 20 ppm.
ppm, and the concentration of xenon is at least 1
ppm preferably at least 2 ppm.

In reboiling zone 44, liquid 61 is partially vaporized to produce vapor, which has a lower rare earth content than the remaining liquid. This vapor 41 is sent to the stripping column 38 and flows upstream through the column. The residual liquid, which has a relatively high chloride and xenon content, is withdrawn as a liquid concentrate product 16 containing rare earth gases. Typically, concentrate 16
The concentration of krypton in the concentrate is at least 200 ppm, preferably at least 400 ppm, and the concentration of
The xenon concentration in 6 is at least 1 s ppm, preferably at least 50 ppm.

FIG. 1 also illustrates a particularly preferred embodiment in which partial vaporization in the reboiler zone is carried out using high pressure nitrogen-rich steam from an associated double column air separation plant.

To explain FIG. 1, a portion 25 of the nitrogen-rich steam 23
is sent to reboiler condenser 43, where it is condensed by indirect heat exchange with partially vaporized reboiler liquid 61. The resulting condensed nitrogen stream 28 is sent to column 19 as a reflux liquid. Conveniently, stream 28 can be combined with liquid nitrogen from main condenser 18 to form a combined stream 29 that is sent to column 19 .

Stripping tower 3 days (l'i, 15-100 psl
a is preferably operated at a pressure in the range of 15 to 30 psla and serves to strip a significant portion, preferably substantially all, of the krypton and xenon in the vapor 41 into the downstream liquid. The incoming downstream stripping liquid must have a lower krypton-xenon concentration than the vapor 41, and preferably the krypton-xenon concentration in this reflux liquid as it enters the column is less than about 3 ppm. A convenient source for the reflux or stripping liquid is a double column air separation plant. FIG. 1 illustrates a particularly preferred embodiment in which fluid stream 35 is withdrawn above the point from which gaseous oxygen product stream 37 is withdrawn. In this manner, liquid stream 35 has a low krypton-xenon concentration.

Within column 58, vapor 41 is passed against downstream liquid 55 and the krypton and xenon from vapor 41 are stripped into the downstream liquid.

The resulting rich liquid 39 is sent to the reboil zone 44 to form a portion of the reboil liquid 61 . Figure 1 is shown in Figure 1)
A convenient arrangement is illustrated in which rich liquid 39 is combined with feed liquid 36 to form liquid 40 and this combined liquid is sent to reboil zone 44 to form reboil liquid 61.

Lean vapor resulting from the stripping operation is withdrawn from column 38 as stream 42 and recovered as a gaseous product substantially free of rare earth gas. Figure 1 shows
1 illustrates a convenient arrangement in which lean steam 42 is combined with gaseous oxygen product 67 from an air separation process and the resulting combined stream 15 is recovered as gaseous phosphorus product.

In a limited embodiment of the present invention, the feedstock to the krypton-xenon concentration process is sent directly to the reboil zone rather than the stripping column, and in a limited embodiment of the invention, where only the vapor from the reboil zone is passed to the stripping column. Producing krypton-xenon concentrates and gaseous rare earth-free oxygenated products using a much smaller stripping column than that required in conventional krypton-xenon concentration processes by carrying out a ripping process. I can do it. Typically, for this process configuration, the feed streams 35 and 36 to the stripping column are about 20% of the nitrogen product 15 from the plant. Therefore, the stripping tower is approximately 1/2
15 of the vapor stream 42, thereby requiring approximately 115 of the cross-sectional flow area of the conventional flow zone of a typical oxygen gas stripping column.

In a particularly preferred embodiment, illustrated in FIG. 1, the majority of the oxygen from the air separation plant completely bypasses the krypton-xenon enrichment process, thus significantly reducing the throughput and therefore size requirements of the stripping column. I understand that. Generally, the liquid stream to the reboiler zone contains about 5-40% and preferably about 20% of the oxygen from the air separation plant.

Another benefit is that most of the oxygen gas 37 is maintained at the pressure level of the low pressure column 17. ) The portion of the oxygen product 42 that must be treated in the IJ Tupping column is
) The IJ topping column can be operated at a slightly reduced pressure level to compensate for the column pressure drop and return to equilibrium pressure. Higher pressure levels can be easily obtained by reducing the height of the stripping column and using hydrostatic heights for the two feeds.

Yet another benefit of this process is that the liquid withdrawn from the low pressure column H serves to avoid hydrocarbon buildup in that column.

The embodiment of FIG. 1 shows that the feedstock to the krypton-xenon enrichment process originates from a double column air separation plant and that the feedstock is used to obtain an increase in krypton-xenon concentration beyond that normally achieved in oxygen. Particularly preferred in that it is taken from an air separation plant.

Table 2 shows the results of a computer simulation of the method of the present invention carried out according to the specific example shown in FIG. This data is provided for illustrative purposes only and is not intended to limit the invention. Abbreviation “c”
fh' is the ambient temperature (70F) and atmospheric pressure (14,7p
ft shhr as measured at sia). Purity is mole % unless ppm capacity is specified.
It is defined in units. The flow numbers correspond to those in FIG.

Table I Flow rate, cfh 800 185
32 temperature, 'K 95 95
95 pressure, 9tr ja 23 23
23 Purity Oxygen, % 99.5 99.6
99.3 krypton, ppm Q, 5 39
．． 1 2.5 xenon, ppm
2.5 - Others, % C
L5 CL4 CL799.5 99
．． 6 99.5 995 99.5-
27 - - 0
．． 2α5 α4 Q, 4
0.5 115 As exemplified by the data in Table 1, the process of the present invention efficiently produces krypton-xenon concentrate and gaseous nitrogen that is substantially free of rare earths while providing a convenient feed to the concentration process. Only a small flow rate of raw material is required. This significantly reduces both the capital investment and operating costs of the enrichment process.

Although the method of the invention has been described in detail with respect to particular embodiments, it is to be understood that other embodiments of the invention are within the scope of the claims.

Figure 1 is a schematic flow diagram of one preferred embodiment of the method of the present invention.

The reference numbers representing the main parts of the precepts are as follows:

17: Low pressure column 18: Condenser 19: High pressure tower 38: Stripping tower 43: Condenser 44: Reboiling zone

Claims (18)

[Claims] (1) A method for producing a krypton-xenon concentrate and recovering a gaseous product substantially free of rare earth gases, comprising: 1) feeding a feed liquid containing oxygen, krypton, and xenon to a reboil zone; 2) partially vaporizing the reboiling liquid to produce a vapor and liquid krypton-xenon concentrate; 3) recovering the krypton-xenon concentrate; and 4) adding the krypton-xenon concentrate to a stripping column. introducing a reflux liquid having a krypton-xenon concentration lower than that in the vapor; 5) directing said vapor against the downstream reflux liquid in a stripping column; and 6) extracting krypton and xenon from said vapor into the reflux liquid. stripping to produce a lean vapor and a richer liquid; 7) passing the richer liquid to a reboiling zone to form a portion of the reboiling liquid; 8) withdrawing the lean vapor from the stripping column; and 9) recovering the extracted lean steam as a gaseous product substantially free of rare earth gases. (2) the krypton concentration in the feedstock liquid is at least 10;
The method according to claim 1, wherein the amount is ppm. 3. The method of claim 1, wherein the richer liquid from the stripping column is combined with the feed liquid before being sent to the reboiling zone. 4. The method of claim 1, wherein the stripping column is operated at a pressure within the range of 15 to 100 psia. (5) The concentration of krypton in the krypton-xenon concentrate is at least 200 ppm.
The method described in section. 6. The method of claim 1, wherein the feed liquid is taken from a heat exchange zone of a dual air separation process. 7. The method of claim 6, wherein the reflux liquid for the stripping column is provided from the lower pressure column of the double column process and is taken from a point above the point from which the feed liquid is taken. 8. The process of claim 7, wherein reflux is taken from the lower pressure column in at least two equilibration stages above the heat exchange zone. 9. The method of claim 6, wherein a gaseous stream is withdrawn from the lower pressure column and recovered as an oxygen product. 10. The method of claim 9, wherein lean steam is combined with a gaseous stream and the combined stream is recovered. 11. The method of claim 9, wherein the gaseous stream is withdrawn from the lower pressure column at a point between the points taking up the feed liquid and the reflux liquid, respectively. (12) A method according to claim 6, wherein the partial vaporization of the reboiling liquid is carried out by indirect heat exchange with condensable nitrogen-rich vapor taken from the high pressure column. 13. The method of claim 12, wherein the resulting condensed nitrogen-rich stream is returned to the high pressure column as reflux liquid. (14) A method for producing a krypton-xenon concentrate and recovering a gaseous product substantially free of rare earth gases, the method comprising: 1) low-temperature rectified air comprising a high pressure column and a low pressure column in heat exchange relationship; supplying feed air to the separation plant; 2) withdrawing a first liquid containing oxygen, krypton, and xenon from the zones in heat exchange relationship; and supplying the withdrawn liquid to a reboiling zone to form a reboiling liquid; 3) partially vaporizing the reboiled liquid to produce a vapor and liquid krypton-xenon concentrate; 4) recovering the krypton-xenon concentrate; withdrawing a second liquid from the lower pressure column at a point, the second liquid having a lower concentration of krypton-xenon than in the vapor produced in the reboiling zone, and stripping the second liquid as a reflux liquid. 6) directing the vapor against the downstream reflux liquid in a stripping column; and 7) stripping the krypton and xenon from the vapor to the reflux liquid to produce a lean vapor and a richer liquid. 8) passing said richer liquid to a reboiling zone to form a portion of the reboiling liquid; 9) extracting lean vapor from the stripping column; 10) converting the extracted lean vapor substantially containing rare earth gases; 11) withdrawing a gaseous stream from the low pressure column at a point between the points where the first and second liquids were withdrawn; and 12) withdrawing the gaseous stream from the lower pressure column. recovery as an oxygen product. 15. The method of claim 14, wherein the extracted lean steam and the extracted gaseous stream are combined and recovered together. 16. The method of claim 14, wherein the second liquid is withdrawn from the lower pressure column in at least two equilibration stages above the zone in heat exchange relationship. (17) A method according to claim 14, wherein the partial vaporization of the reboiling liquid is carried out by indirect heat exchange with condensable nitrogen-rich vapor taken from a high pressure column. 18. The method of claim 17, wherein the resulting condensed nitrogen-rich stream is returned to the high pressure column as a reflux liquid.