JPH092808A - Production of krypton - Google Patents

Abstract

PURPOSE: To produce krypton of high purity at high yield at a low cost in a safe manner by concentrating krypton in a liquefied oxygen taken out from a main condenser in an upper rectification tower of an air separation apparatus by an absorption process. CONSTITUTION: A liquefied oxygen containing krypton and xenon is taken out from a main condenser 1 in an upper rectification tower of an air separation apparatus. The liquefied oxygen is gasified followed by absorption and separation of the xenon with an absorption tower 2 packed with a xenon selective absorbent at -170 deg.C. A through gas is introduced into the absorption tower 3 packed with a krypton selective absorbent at -170 deg.C until the breakthrough of the krypton. Then, the tower is warmed up to 70 deg.C with good attention on the concentration of hydrocarbons to desorb the krypton and the recovered krypton is collected in a krypton concentrated gas tank 4. Hydrocarbons in the krypton concentrated gas are burned in a catalyst tower 5 and water and carbon dioxide gas are removed by a removing tower 6. Then, the krypton concentrated gas is introduced into an absorption tower 7 packed with a krypton selective absorbent and cooled down to -170 deg.C until the breakthrough. Then, the tower is warmed up to -100 deg.C, purged with a product gas, and further warmed up to 70 deg.C to recover the krypton.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention repeatedly produces a high-purity krypton by repeatedly concentrating krypton contained in liquefied oxygen in the main condenser of an upper rectification column of an air separation device mainly by an adsorption method. Regarding the method.

[0002]

2. Description of the Related Art Since krypton used as a filling gas for discharge tubes is contained in the air in a small amount of 1.14 ppm, liquefied oxygen in the main condenser of the upper rectification column of a large air separation apparatus is currently used. It is co-produced with xenon by distillation from the inside. In the method of recovering from liquefied oxygen by distillation, hydrocarbons, particularly methane, in liquefied oxygen are concentrated with the concentration of krypton, which causes a danger of explosion. As a countermeasure, various methods have been proposed in the past, for example, after suppressing the concentration of xenon and krypton to the extent that there is no risk of explosion of hydrocarbons, and burning and removing hydrocarbons with a catalyst, Krypton, by distillation
Method for concentrating xenon (FUJI TECHNOSYSTEM Technical Data (61-2-1), p430-431), oxygen contained in a mixture enriched with krypton and xenon is sufficiently contained in the stripping tower. A method of vaporizing after replacing with argon, then separating carbon dioxide and water generated by burning a hydrocarbon by a catalyst, then depressurizing the mixture in a separation column, and taking out krypton and xenon in a liquid form from the bottom thereof. (JP-B-47-22937), a method in which high-pressure nitrogen and oxygen are replaced under pressure, and then krypton and xenon are concentrated by distillation (JP-A-57-95583).
Etc. have been proposed.

On the other hand, as a method of co-producing krypton and xenon by an adsorption method, an adsorbent having pores with a pore diameter of 5 to 150 Å kept at the same temperature as that of air at a temperature of 90 to 110 ° K is used. Xenon, krypton, nitrogen, oxygen and hydrocarbons are adsorbed on the adsorbent, and then the adsorbent temperature is changed from 90 to 110 ° K to 25 within 1 to 8 hours.
0-280 ° K, then 250-28 in 2-4 hours
The gas is desorbed by gradually increasing it from 0 ° K to 500 to 650 ° K, which is 1 to 46% by volume of krypton, 0.1 to 4% by volume of xenon, and by volume. Method for separating a krypton-xenon mixture containing 94.5-46% nitrogen, up to 2% oxygen by volume and up to 2% hydrocarbon by volume from air (JP-A-51-
No. 117997) has been proposed.

As a method for producing krypton, a step of supplying liquefied oxygen containing a very small amount of krypton, xenon, methane and the like to a concentration column and concentrating it by rectification,
A step of introducing the concentrated liquid obtained in the step to a methane purging column to purge methane in the liquid by countercurrent contact with oxygen gas from the top of the tower and distilling the concentrated liquid to the bottom of the tower; From the step of adsorbing and removing the water and carbon dioxide gas produced by combustion in a catalytic combustion tube after the gasification, and the step of rectifying and separating krypton and xenon after deoxidizing and purifying the mixed gas obtained in the step. (Japanese Patent Laid-Open No. 57-43186) has been proposed.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The methods disclosed in Japanese Patent Application Laid-Open No. 937, Japanese Patent Application Laid-Open No. 57-95583, and Japanese Patent Application Laid-Open No. 51-117997 are for recovering a krypton-xenon mixture, and are capable of producing krypton inexpensively with high purity and high yield. It has a problem that it cannot be manufactured. In addition, JP-A-57-43
Although the method disclosed in Japanese Patent No. 186 discloses that rectification separation is carried out into krypton and xenon, it is not specified how much purity krypton can be obtained in what yield.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to safely and highly purify the krypton in liquefied oxygen discharged from the main condenser of the upper rectification column of the air separation device by using an adsorption method. The object of the present invention is to provide a method for producing krypton that can be produced at a low cost at a high rate.

[0007]

Means for Solving the Problems The present inventors have intensively studied and studied to achieve the above object. Liquefied oxygen containing krypton and xenon derived from the main condenser of the upper rectification column of the air separation device was first introduced into an adsorption column filled with an adsorbent that selectively adsorbs xenon to adsorb only xenon, and passed through. Oxygen gas containing krypton and hydrocarbons is introduced into a plurality of adsorption columns filled with an adsorbent that selectively adsorbs krypton, adsorbing and desorbing them to sequentially concentrate krypton, and at the same time, catalyzing hydrocarbons. It was clarified that high-purity krypton can be produced in high yield at low cost by burning and removing, and the present invention was reached.

That is, according to the first aspect of the present invention, a plurality of adsorbents which gasify the liquid oxygen containing krypton and xenon from the main condenser of the upper rectification column of the air separation device and which adsorbs xenon selectively are filled. After adsorbing xenon to separate xenon by adsorbing xenon and letting krypton pass through from the adsorption column, it is introduced into a plurality of adsorption columns filled with an adsorbent that selectively adsorbs krypton, and adsorbed / desorbed. The method for producing krypton is characterized in that high purity krypton is obtained by sequentially concentrating krypton and burning and removing hydrocarbons by a catalyst.

The second aspect of the invention of the present application is to gasify the liquefied oxygen containing krypton and xenon, which is discharged from the main condenser of the upper rectification column of the air separation unit, at a temperature higher than the liquefaction temperature of oxygen and at the same time as xenon. Was introduced into an adsorption column filled with an adsorbent that selectively adsorbs xenon and separated from xenon by allowing krypton to pass through the adsorption column and then filled with an adsorbent that selectively adsorbs krypton. It flows until the krypton breaks through the adsorption tower, desorbs while concentrating and recovering krypton by charging oxygen so that the hydrocarbons in the adsorbed gas do not reach the explosion limit, and the recovered gas is introduced into the catalyst tower to introduce hydrocarbons. The krypton-enriched gas, which has been burned to remove the compounds, is cooled to a temperature higher than its liquefaction temperature and adsorbed in an adsorption tower filled with an adsorbent that selectively adsorbs krypton. It flowed to superatmospheric be, then purged in the adsorption tower in the part of the product gas, a method for producing a krypton, characterized in that to obtain high-purity krypton.

Further, the invention of the third aspect of the present application is a krypton which is derived from the main condenser of the upper rectification column of the air separation device,
To gasify liquefied oxygen containing xenon, introduce it into an adsorption tower filled with an adsorbent that selectively adsorbs xenon at a temperature higher than the liquefaction temperature of oxygen, adsorb xenon, and let krypton pass through the adsorption tower. After being separated from xenon by, flow through an adsorption column filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through, desorbing while adsorbing oxygen so that hydrocarbons in the adsorbed gas do not reach the explosion limit. Then, the krypton is concentrated and recovered, and the recovered gas is introduced into the catalyst tower to burn and remove hydrocarbons by the catalyst, and the krypton concentrated gas is cooled to a temperature higher than its liquefaction temperature and selectively adsorbs krypton. Xenon is adsorbed by flowing it through an adsorption tower filled with agent until the krypton breaks through, concentrating and recovering krypton, and then applying a high vacuum to the inside of the tower. After removing it, the krypton-enriched gas is cooled to a temperature higher than its liquefaction temperature and allowed to flow through an adsorption column filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through. A method for producing krypton, which comprises purifying the inside of an adsorption tower to obtain high-purity krypton.

[0011]

In the first aspect of the present invention, a plurality of adsorbents which gasify krypton- and xenon-containing liquefied oxygen from the main condenser of the upper rectification column of the air separation device and are filled with an adsorbent which selectively adsorbs xenon are provided. After being introduced into an adsorption tower and separated from xenon by adsorbing xenon and letting krypton pass through from the adsorption tower, it is introduced into a plurality of adsorption towers filled with an adsorbent that selectively adsorbs krypton, and adsorption / desorption is performed. By sequentially concentrating krypton and burning and removing hydrocarbons by a catalyst, there is no danger of explosion of hydrocarbons even if oxygen is not replaced with argon or nitrogen, and high purity krypton with high yield is obtained. It can be manufactured at a low rate.

In the second aspect of the present invention, the krypton-containing oxygen gas separated from the xenon is flowed and adsorbed in an adsorption tower filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through. The krypton enriched gas obtained by desorbing and concentrating and recovering krypton while charging oxygen so that the hydrocarbons in the gas do not reach the explosion limit and introducing the recovered gas into the catalyst column to burn and remove hydrocarbons By cooling the mixture to a higher temperature and flowing it into an adsorption tower filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through, and then purging the inside of the adsorption tower with a part of the product gas, The remaining krypton and oxygen can be driven out of the system to achieve high purification of krypton with a smaller number of columns.

In the third aspect of the present invention, the krypton-containing oxygen gas separated from the xenon is flowed through an adsorption tower filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through, and the adsorbed gas is adsorbed in the adsorbed gas. Of the krypton concentrated gas, which is desorbed while charging oxygen so that the hydrocarbons do not enter the explosive limit, is concentrated and recovered, and the recovered gas is introduced into the catalyst tower to burn and remove hydrocarbons by the catalyst. Xenon that is cooled to a higher temperature and flows through an adsorption column filled with an adsorbent that selectively adsorbs krypton until krypton breaks through to concentrate and recover krypton, and then the inside of the column is evacuated to a high vacuum to adsorb xenon. And then the krypton-enriched gas is cooled to a temperature above its liquefaction temperature and adsorbed in an adsorption column filled with an adsorbent that selectively adsorbs krypton. After tons flowed until breakthrough, expelled by purging the inside of the adsorption tower in the part of the product gas, krypton remaining in the adsorption tower, the oxygen out of the system,
Higher purification of krypton can be achieved with a smaller number of towers.

In the present invention, the adsorbent which selectively adsorbs krypton is used because the oxygen gas containing krypton is caused to flow through the adsorption column and the oxygen gas containing krypton is supplied at the time when the krypton starts to flow out from the outlet of the column. By stopping and recovering the adsorbed krypton, it is possible to obtain krypton in a high yield and to prevent the risk of explosion due to methane concentration. In addition, the use of a plurality of adsorption towers in the present invention allows the krypton in the krypton-containing oxygen gas to be sequentially concentrated and the exhaust gas from the adsorption tower to be recycled, thereby minimizing the krypton discharged to the outside of the system. Because. As the adsorbent that selectively adsorbs krypton, silica gel, activated carbon, zeolite having a molecular sieving effect, or the like can be used.

According to the present invention, not only the krypton in the liquefied oxygen discharged from the air separation device but also the krypton separation in the low temperature distillation recovery facility of the exhaust gas of the spent nuclear fuel reprocessing plant containing radioactive krypton is the main component. It is the same that the adsorption target component is krypton simply by replacing the gas with oxygen and the oxy-nitrogen mixed gas, and similarly, highly pure krypton can be obtained at a high yield at a low cost.

[0016]

【Example】

Example 1 As shown in the process chart shown in FIG.
0 nm ³ / Hr was withdrawn gasifying liquefied oxygen 150 Nm ³ / Hr from the main condenser of the rectification column 1 of all the low-pressure air separation device, krypton contained in the oxygen gas 7
0ppm, xenon 31ppm, methane 38pp
m, other hydrocarbons were very small. -17 above gas
Xenon cooled to 0 ° C. was introduced into an adsorption tower 2 filled with silica gel that selectively adsorbs xenon, xenon was selectively adsorbed, and oxygen gas containing krypton was passed through.
The through gas from which xenon had been removed was passed through an adsorption tower 3 filled with activated carbon that selectively adsorbs krypton cooled to −170 ° C. until the krypton passed through the adsorption tower 3, and then -50
The desorption gas with a low krypton concentration was discharged from the outlet of the adsorption tower 3 by heating to 70 ° C and further heated to 70 ° C to 100T.
Krypton is recovered by reducing the pressure to orr. When the krypton-concentrated gas was recovered in the krypton-concentrated gas tank 4 while paying attention not to increase the hydrocarbon concentration during this period, the krypton concentration was 2% and the hydrocarbons concentration was 0.5%.

During the recovery of the krypton concentrated gas, in order to prevent the risk that the hydrocarbons adsorbed on the activated carbon will be desorbed and the concentration will rise to several% when the heating is rapidly performed,
It is necessary to perform a desorption operation in which oxygen gas dilution and vacuum recovery are repeated several times. If silica gel or zeolite is used as an adsorbent that selectively adsorbs krypton,
Although it is not necessary to dilute with an oxygen gas in the desorption operation, the adsorption tower 3 becomes large in size. Therefore, in this Example 1, activated carbon that selectively adsorbs krypton was used for the purpose of downsizing the adsorption tower 3. The krypton concentrated gas in the krypton concentrated gas tank 4 was introduced into the catalyst tower 5 to burn and remove hydrocarbons, and the produced water and carbon dioxide gas were removed in the removal tower 6. The krypton enriched gas from which hydrocarbons have been burned and removed is -17
After flowing through an adsorption tower 7 filled with activated carbon that selectively adsorbs krypton cooled to 0 ° C. until the krypton breaks through, it is heated to −100 ° C. and a low krypton concentration is discharged from the outlet of the adsorption tower 7. After being discharged, a part of the product krypton gas is adsorbed from the product gas tank 8 at -100 ° C.
After purging oxygen in the adsorption tower 7, it was heated to 70 ° C. and krypton was recovered. The purity of the recovered krypton was 99.9%.

The exhaust gas obtained when the adsorption tower 7 was purged with a part of the product krypton gas was recovered in the krypton concentrated gas tank 4, and the recovery rate of krypton was 95%.
Was able to improve. The temperature range for recovering the krypton-enriched gas from the adsorption tower 3 packed with activated carbon that selectively adsorbs krypton can be a temperature above the liquefaction temperature of oxygen, but the krypton concentration is about -150 to -180 ° C. high. The temperature range for recovering krypton from the adsorption tower 7 filled with activated carbon that selectively adsorbs krypton can be equal to or higher than the liquefaction temperature of oxygen, but the krypton concentration is high at about -150 to -180 ° C. . Further, the adsorption pressure of the adsorption towers ² , 3, 7 is sufficient to be atmospheric pressure to 3.0 kg / cm ² · G.

Example 2 As shown in the process diagram of FIG. 2, the rectification column 1 is the same as in Example 1.
70pp of gasified krypton extracted from the main condenser of
m, xenon 31 ppm, methane 38 ppm, and an oxygen gas containing a very small amount of other hydrocarbons are introduced into an adsorption tower 2 filled with silica gel that selectively adsorbs xenon cooled to -170 ° C. to selectively xenon the xenon. It was adsorbed and oxygen gas containing krypton was passed through. The through gas from which xenon had been removed was passed through an adsorption tower 3 filled with activated carbon that selectively adsorbs krypton cooled to -170 ° C until krypton passed through, and then heated to 70 ° C.
When the krypton concentrated gas was recovered in the krypton concentrated gas tank 4 while paying attention not to increase the hydrocarbon concentration by reducing the pressure to 00 Torr, the krypton concentration was 2% and the hydrocarbons concentration was 0.5%.

The krypton enriched gas in the krypton enriched gas tank 4 was introduced into the catalyst tower 5 to burn and remove hydrocarbons, and the produced water and carbon dioxide gas were removed in the removal tower 6. The krypton-enriched gas from which hydrocarbons have been burned and removed is -15
After flowing through an adsorption tower 7 filled with activated carbon that selectively adsorbs krypton cooled to 0 ° C. until krypton breaks through, it is heated to −100 ° C. and a low krypton concentration is discharged from the outlet of the adsorption tower 7. After discharging, -100 ℃ to 7
After heating to 0 ° C., krypton was collected in the tank 9 by a vacuum pump. The concentration of krypton recovered was 95%. Then, the adsorption tower 7 is evacuated to a high vacuum to release the adsorbed xenon to the atmosphere. This tank 9
The recovered gas was cooled to −20 ° C. and passed through an adsorption tower 10 filled with activated carbon that selectively adsorbs krypton until the krypton breaks through. Then, a part of the product krypton gas is adsorbed from the product gas tank 8. Flow to the adsorption tower 10
After purging the oxygen in it, it was heated to 90 ° C. to collect krypton, and deoxygenated by passing through deoxo 11.
It was collected in the product tank 8. The purity of the recovered krypton was 99.995%.

Exhaust gas obtained when the adsorption tower 10 is purged with a part of the product krypton gas is recovered in the krypton enriched gas tank 4 or tank 9, and the portion of the exhaust gas in the adsorption tower 7 having a high krypton concentration is krypton enriched. When recovered in the gas tank 4, the recovery rate of krypton is 95
It was possible to improve to%. The temperature range in the recovery from the adsorption towers 3 and 7 is the same as the temperature described in Example 1, and the temperature range in the krypton recovery from the adsorption tower 10 is −100 ° C. to room temperature and the krypton recovery rate is high. .

[0022]

As described above, according to the method of the present invention, since the krypton is concentrated mainly by the adsorption operation, a high-pressure facility is required as compared with the conventional krypton production method mainly by the rectification. In addition, it is not necessary to replace oxygen with argon or nitrogen, there is no danger of explosion due to the concentration of hydrocarbons, and high-purity krypton can be produced safely, at high yield, and at low cost.

[Brief description of drawings]

FIG. 1 is a process drawing in a first embodiment of the present invention.

FIG. 2 is a process drawing of a second embodiment of the present invention.

[Explanation of symbols]

 1 rectification tower 2, 3, 7, 10 adsorption tower 4 krypton concentrated gas tank 5 catalyst tower 6 removal tower 8 product gas tank 9 tank 11 deoxo

Claims (3)

[Claims] 1. A krypton contained in liquefied oxygen in a main condenser of an upper rectification column of an air separation unit is introduced into an adsorption column filled with an adsorbent which selectively adsorbs xenon to adsorb xenon. After separating krypton from xenon by letting it pass through the adsorption tower, it is introduced into a plurality of adsorption towers filled with an adsorbent that selectively adsorbs krypton,
A method for producing krypton, which comprises successively concentrating krypton by adsorption and desorption, and then introducing it into a catalyst column to burn and remove hydrocarbons by a catalyst to obtain high-purity krypton. 2. A krypton-containing liquefied oxygen discharged from a main condenser of an upper rectification column of an air separation device is gasified and filled with an adsorbent having a temperature higher than the liquefaction temperature of oxygen and selectively adsorbing xenon. Introduced into the adsorption tower, after the xenon is adsorbed and krypton is separated from the xenon by passing through the adsorption tower, the adsorption tower filled with the adsorbent for selectively adsorbing krypton is flowed until the krypton breaks through, The krypton enriched gas obtained by desorbing and desorbing krypton while charging oxygen so that the hydrocarbons in the adsorbed gas do not reach the explosive limit and introducing the recovered gas into the catalyst tower to burn and remove hydrocarbons, Cool it to a temperature higher than the liquefaction temperature and let it flow through an adsorption column filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through, then part of the product gas. A high-purity krypton is obtained by purging the inside of the adsorption tower with. 3. A krypton-containing liquefied oxygen discharged from a main condenser of an upper rectification column of an air separation device is gasified, and is filled with an adsorbent having a temperature higher than the liquefaction temperature of oxygen and selectively adsorbing xenon. Introduced into the adsorption tower, after the xenon is adsorbed and krypton is separated from the xenon by passing through the adsorption tower, the adsorption tower filled with the adsorbent for selectively adsorbing krypton is flowed until the krypton breaks through, The adsorbed gas is desorbed while being filled with oxygen so that the hydrocarbons do not reach the explosive limit, and krypton is concentrated and recovered, and the recovered gas is introduced into the catalyst tower to burn and remove hydrocarbons by the catalyst to remove the krypton concentrated gas. , It is cooled to a temperature higher than its liquefaction temperature, and is flowed through an adsorption column filled with an adsorbent that selectively adsorbs krypton until the krypton breaks through. Was concentrated and recovered, and the column was evacuated to a high vacuum to remove the adsorbed xenon, after which the krypton concentrated gas was cooled to a temperature higher than its liquefaction temperature and charged with an adsorbent that selectively adsorbs krypton. A method for producing krypton, characterized in that high-purity krypton is obtained by allowing the krypton to flow through the adsorption tower until it breaks through and then purging the inside of the adsorption tower with a part of the product gas.