JPH07139876A - Method for purifying krypton and xenon - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide a method for purifying krypton and xenon to high purity continuously and efficiently with a simple apparatus configuration. [Constitution] A concentration step of introducing liquefied oxygen containing krypton and xenon into a concentration column 3 to concentrate krypton and xenon, and copper / chromium for removing hydrocarbons by reacting oxygen with oxygen after vaporizing the bottom liquid of the concentration column Complex reaction catalyst reaction tube 1
5 and adsorber 1 for removing carbon dioxide and water of reaction products
8, a catalyst refining process for diluting hydrocarbons in the bottom liquid of the concentration tower by branching the gas after advancing the adsorber and introducing one to the bottom of the concentration tower. A step of controlling the introduction amount of krypton- and xenon-containing gas after the catalytic reaction step to be introduced, a step of liquefying the other again and introducing it into the deoxygenation tower 23 to rectify and remove oxygen, a deoxygenation tower bottom liquid is a separation tower A method for purifying xenon and krypton, which comprises the step of rectifying at 28 to separate xenon and krypton.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying krypton and xenon, and more particularly to a method for purifying krypton and xenon concentrated in liquefied oxygen in the upper part and lower part of the double rectification column of an air liquefaction separation apparatus. .

[0002]

2. Description of the Related Art Conventionally, krypton and xenon, which are concentrated in liquefied oxygen of an air liquefaction separation apparatus, are further concentrated, the concentrated liquid or gas is further purified, and then krypton and xenon are separated from each other. ing.

Usually, these apparatuses repeat a rectification step, a catalyst step and an adsorption step, and the krypton 90-
After obtaining a concentrated solution of 95% and xenon 5-10%, krypton and xenon are further separated.
Therefore, liquefied oxygen after being discharged from the main condenser / evaporator of the double rectification column was subjected to about 10 purification steps to obtain krypton and xenon as final products.

[0004]

However, the amount of krypton and xenon contained in the atmosphere is 1.1, respectively.
It is an extremely small amount of 4 ppm and 0.086 ppm, and at the same time it is concentrated, hydrocarbons in the atmosphere (mainly methane,
In the following, since the same is also concentrated, a large number of steps are required as described above, and continuous purification cannot be performed, making it difficult to manufacture a device having a consistent purification step.

Therefore, the present invention aims to provide a purification method in which the number of steps is reduced, krypton and xenon can be continuously and efficiently separated, and highly purified krypton and xenon can be obtained. Has an aim.

[0006]

In order to achieve the above object, the method for purifying krypton and xenon of the present invention comprises:
In a method for purifying krypton and xenon from liquefied oxygen containing krypton and xenon derived from an air liquefaction separation device, a step of introducing the liquefied oxygen into a concentration column to concentrate krypton and xenon in a bottom liquid, and the concentration In the catalytic reaction step of vaporizing the tower bottom liquid and introducing it into the catalytic reaction tube to react the contained hydrocarbons with oxygen, and introducing the gas after the catalytic reaction tube is introduced into the adsorber into the catalytic reaction step. The adsorption step of adsorbing and removing the produced water and carbon dioxide, and the gas after the desorption of the adsorption step are cooled again and then divided into 2 minutes, and one of them is reintroduced into the lower part of the concentrating tower to introduce hydrocarbons in the bottom liquid of the concentrating tower. Of the amount of hydrocarbons contained in the bottom liquid of the concentration column or the carbonization of containing them hydrogen And krypton before being introduced into the catalytic reaction step of reacting oxygen with oxygen, a step of detecting the content of hydrocarbons in the xenon-containing gas, and performing according to the content of the detected hydrocarbons, The other branched one is introduced into a deoxygenation tower for rectification separation, oxygen gas containing a small amount of krypton is discharged from the top of the deoxygenation tower, and a mixture liquid of krypton and xenon is distilled out to the bottom of the tower. The method is characterized in that an oxygen step and a deoxidizing tower bottom liquid are introduced and introduced into a separation tower, and krypton is discharged from the top of the separation tower and xenon is discharged from the tower bottom, respectively.

Further, in the present invention, in the catalytic reaction step of reacting the hydrocarbons contained in the catalytic reaction tube with oxygen, a copper-chromium composite catalyst is used as a catalyst, The reaction temperature of the catalytic reaction step for reacting the introduced hydrocarbons and oxygen with each other is 300 to 700 ° C., the space velocity is 1000 to 6000 h ⁻¹ , and the reaction is carried out at a top of the deoxygenation column containing krypton. Reintroducing part or all of the oxygen gas into the middle part or the lower part of the concentration column, and again introducing part or all of the oxygen-containing krypton gas discharged from the top of the separation column into the lower part of the concentration column. I am trying.

Further, as an apparatus configuration for carrying out the above-mentioned method of the present invention, in the apparatus for purifying krypton and xenon from liquefied oxygen containing krypton and xenon which is derived from an air liquefaction separation apparatus, the liquefied oxygen is introduced. Concentration column for concentrating krypton and xenon in the column bottom liquid, a catalyst reaction column for reacting the hydrocarbons contained therein with oxygen after vaporizing the concentration column column bottom liquid, and water produced in the catalyst reaction column. An adsorber for adsorbing and removing carbon dioxide, a path for dividing the gas discharged from the adsorber into two and reintroducing one into the concentrating tower, a content of hydrocarbons in the bottom liquid of the concentrating tower, or Detecting means for detecting the content of hydrocarbons in the krypton- and xenon-containing gas before being introduced into the catalytic reaction step of reacting the contained hydrocarbons with oxygen, and the content of the detected hydrocarbons. A control means for controlling the introduction amount of the krypton / xenon-containing gas after the catalytic reaction step, which is re-introduced into the lower part of the concentrating column according to the amount, and the other of the two divided parts are introduced to carry out rectification separation, A deoxygenation column that derives oxygen gas containing a small amount of krypton from the column and distills a mixed solution of krypton and xenon at the bottom of the column, and the deoxygenation column bottom liquid is introduced for rectification separation, Those equipped with krypton and a separation column for extracting xenon from the bottom of the column are suitable.

[0009]

[Operation] According to the above configuration, the krypton and xenon in the liquefied oxygen derived from the air liquefaction separation device can be efficiently purified to a high purity in a continuous and consistent process by reducing the number of processes.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail based on an embodiment shown in the drawings. First, from the main condenser evaporator 1a portion of the upper column lower part of the double rectification column 1 of the air liquefaction separation device,
Liquefied oxygen in which 400 ppm of krypton, 20 ppm of xenon and 100 ppm of hydrocarbons (mainly methane) are concentrated is extracted and introduced into the middle or upper part of the concentration column 3 by the liquid acid pump 2. In this case, if the concentration tower 3 is installed below the main condenser evaporator 1a, it can be introduced into the top of the concentration tower 2 without the pump due to the liquid column pressure of liquefied oxygen.

At the bottom of the concentrating column 3, there is provided a reboiler 5 which uses oxygen gas, nitrogen gas, argon gas or air supplied from a pipe 5a as a heating source, and heats the column bottom liquid to raise the rising gas. To generate. The ascending gas rises in the tower, is condensed in the condensing tower condenser 6 provided at the top of the concentrating tower 3, becomes a reflux liquid, flows down, and comes into contact with the ascending gas for rectification. A part of the liquefied gas generated as a heating source in the reboiler 5 was used as a cold source in the condensing tower condenser 6 after controlling the pressure with the control valve 5c, and the remaining liquefied gas was condensed in the deoxidation tower as described later. It is used as a cold source of the vessel 25, and the surplus is introduced and stored in a refrigerant liquefied gas storage tank 36 described later.

The amount of heating in the reboiler 5, that is, the amount of rising gas, is adjusted by detecting the liquid level of the bottom liquid of the concentrating tower 3 with a liquid level controller (LIC) L1 and adjusting the valve 5b. By doing.

Liquefied oxygen containing krypton and xenon introduced from the double rectification column 1 by the rectification in the concentration column 3 is a concentrated liquid in which krypton and xenon are concentrated 20 to 50 times at the bottom of the column. And oxygen gas is led to the pipe 7 from the top of the column. At the bottom of the concentrating tower 3, krypton is about 9000 ppm and xenon is about 1000 p.
While being concentrated to pm, hydrocarbons contained in the raw material liquefied oxygen are concentrated to 1000 ppm or more.

Since it is dangerous if the concentration of hydrocarbons increases, the krypton- and xenon-containing gas after being discharged from the catalytic reaction tube 15 is branched and introduced into the concentration column 3 again as described later. As a result, the hydrocarbons become a concentrated liquid concentrated at a concentration of 10 times or less.

The concentrated liquid at the bottom of the concentrating tower 3 is introduced into a pipe 4 and is installed at a position where the liquid head of the concentrated liquid can spontaneously flow into it, a heat exchanger 8, a heater 14, a catalyst cylinder 15, It is introduced into the deoxidizing tower 23 and / or the concentrating tower 3 via the cooler 17 and the adsorber 18. The concentration column 3 is installed at a position where the liquid column pressure sufficient to perform this step is obtained.

Next, the bottom liquid discharged from the bottom of the concentration tower 3 to the pipe 4 is heat-exchanged with the gas after catalyst purification in the concentration tower heat exchanger 8 to be vaporized, and then to the catalyst purification step by the liquid column pressure. Send air. When the position of the concentration tower 3 is not set so that the gas can be supplied by the liquid column pressure, the pressure is increased by the line pump 9 and the air is supplied to the catalyst refining step.

In any case, the hydrocarbon analyzer 11a
The control valve 10 is opened and closed according to the concentration of hydrocarbons in the bottom liquid of the concentrating tower 3 detected and measured by, and the space velocity in the catalytic reaction cylinder 15 is adjusted by adjusting the amount of gas introduced into the catalytic reaction cylinder 15. Control within the optimum speed range.

The top and bottom of the bottom liquid of the concentrating tower resulting from this are adjusted by controlling the heating amount of the reboiler 5 with a valve 5b which is opened and closed by a signal from a liquid level indicator controller (LIC) L1.

Thus, the content of hydrocarbons in the krypton- and xenon-containing gas before being introduced into the catalytic reaction step in which the hydrocarbons contained in the catalytic reaction cylinder 15 and oxygen react with each other is detected. The reaction conditions (space velocity) of the catalytic reaction step depending on the detected content of hydrocarbons are set manually or so that the concentration of hydrocarbons at the outlet of the catalytic reaction tube is 0.05 ppm or less. Adjust automatically.

The automatic control valve 10 of this embodiment is an air supply amount control valve when air is supplied by utilizing the liquid column pressure.
When the pump 9 is used, it is a valve for adjusting the amount of gas circulating in the pump 9. The concentrated liquid whose amount of air is adjusted then enters the catalyst tube heat exchanger 13 through the conduit 12 and the catalyst reaction tube 15
Of the catalyst reaction tube 15 from the temperature controller 16 with the heater 14 to heat up to the temperature of the catalytic reaction.
The signal based on the detected temperature in the catalyst reaction tube 15 is used to optimize the reaction temperature, that is, the catalyst reaction tube 1
The temperature is adjusted so that the residual amount of hydrocarbons at the 5th outlet is 0.05 ppm or less. In the catalytic reaction tower 15, the hydrocarbons contained in the concentrated gas are reacted with oxygen to produce carbon dioxide and water.

The catalytic reaction tube 15 contains copper / chromium (CuC).
r) The composite catalyst is filled in a predetermined amount. The catalyst is platinum (P
It may be a noble metal catalyst such as t) or palladium (Pd). These metal catalysts may be used alone or in combination and stacked and filled. Regarding the reaction conditions in the catalytic reaction tube 15, a temperature of 300 to 700 ° C. and a lower reaction temperature are better in view of the life of the catalyst, but 350 ° C. or higher is preferable from the viewpoint of complete removal. And the space velocity is about 1000 ~
Within the range of 5000 h ^-1 , about 1000 ppm of hydrocarbons mainly containing the above residual methane can be removed to 0.05 ppm or less.

With the above copper / chromium catalyst, the temperature is 650 ° C.
Hydrocarbons were below the detection limit (0.05 ppm) at a space velocity of 3600 h ^-1 .

The catalytic reaction tube 15, that is, the gas that has been discharged from the process of removing hydrocarbons, exchanges heat with the concentrated gas that flows into the heat exchanger 13 and flows down, and is cooled by cooling water in the cooler 17. Adsorber 18 that is used after switching after cooling
The carbon dioxide and water produced by the catalytic reaction are adsorbed and removed. In addition, one of the adsorbers 18 is in the adsorption process and the other is in the regeneration process. The regeneration step is performed by a heating regeneration step performed by introducing heated nitrogen gas into the adsorber and a cleaning step performed by introducing oxygen gas.

The concentrated gas derived from the step of removing hydrocarbons is liquefied again by exchanging heat with the bottom liquid of the concentrating tower flowing countercurrently in the heat exchanger 8, and one minute is divided into the above hydrocarbons. The concentration of hydrocarbons in the bottom liquid detected by the analyzer 11a or the hydrocarbons in the krypton- and xenon-containing gas before being introduced into the catalytic reaction step of reacting the contained hydrocarbons with oxygen The content of the bottom liquid of the concentration column 3 is again introduced into the lower part of the concentration column 3 while its flow rate is adjusted by the operation of the control valve 21a which opens and closes according to the detected content of the hydrocarbons. Dilute. In addition, since there is no sudden change in the concentration of hydrocarbons in the bottom liquid of the concentration tower 3,
The above-mentioned flow rate adjustment, that is, the adjustment valve 21a may be manually operated.

The other branched one exchanges heat with the gas vaporized in the deoxidizing tower condenser 25 in the heat exchanger 22 from the conduit 20 through the shutoff valve 21b to further lower the temperature, and then the deoxidizing tower 23.
Introduced in the middle stage. When the conduit 20 is provided with a shutoff valve 21b, the concentration of residual hydrocarbons in the concentrated gas discharged from the catalytic reaction tube 15 is detected by the hydrocarbon analyzer 11b, and when it exceeds 0.05 ppm. Or, when the water content exceeds a dew point of −70 ° C., this operates and the deoxidation tower 23
Cut off the introduction.

The deoxygenation tower 23 is equipped with a rectification stage of about 20 to 40 actual stages such as a sieve tray or a bubble cap.
The reboiler 24 is at the bottom of the tower and the reboiler 2 is at the top of the tower.
A condenser 25 is provided which uses the liquefied oxygen liquefied in 4 and the liquefied gas liquefied in the concentration tower reboiler 5 as a cold source.

As the gas used as the heating source of the deoxygenation tower reboiler 24, oxygen, nitrogen, argon, air or the like is pressurized to an appropriate pressure and used as in the concentrating tower 3. By heating and cooling the reboiler 24 and the condenser 25 to adjust the reflux ratio to a range of about 0.1 to 1.2, the oxygen concentration in the bottom liquid can be 0.5 ppm or less.

Further, the liquid level at the bottom of the deoxygenation tower 23 changes due to fluctuations in the supply amounts of the krypton and xenon enriched gas from the conduit 20, which is a liquid level detector (LIC).
The liquid level of the column bottom liquid is detected by L2, and the amount of heating of the reboiler 24 by the heating gas from the pipe 26 is adjusted by the control valve 26a receiving this signal, so that the liquid level of the column bottom liquid falls within the optimum range. Control. The gas liquefied by this heating is adjusted to the optimum pressure by the valve 26b, and then the deoxidizing tower condenser 2
Introduced in 5.

By the rectification in the deoxygenation tower 23, liquefied gas consisting of 90 to 95% of krypton, 5 to 10% of xenon and 0.5 ppm or less of oxygen is separated at the bottom of the deoxygenation tower 23.

Further, 10 to 50 krypton is provided at the top of the tower.
Oxygen gas containing ppm is separated and led out from the pipe 33a and circulated through the conduit 33 to the middle stage or the lower stage of the concentration tower 3. The oxygen-based gas in the conduit 33 may be introduced into the low pressure column of the double rectification column 1.

The deoxygenating column bottoms liquid thus enriched with krypton and xenon is introduced from the conduit 24a into the middle stage or middle lower stage of the separation column 28 for rectifying and separating krypton and xenon.

Further, the fluctuation of the supply amount of the krypton / xenon concentrate supplied from the conduit 27 is adjusted by storing the mixed solution in the mixed solution storage tank 35 depending on the operating states of the concentration tower 3 and the deoxygenation tower 23. Then, the concentrate is separated into a separation tower 2
Supply to 8. This adjustment is performed using the valves 27a, 27b and 27c. When the oxygen concentration in the column bottom liquid is detected by the oxygen concentration analyzer 24b and the measured value exceeds a predetermined value, the shutoff valve 24c shuts off the supply of the column bottom liquid to the separation column 28. The shutoff valve 24c is operated in conjunction with the actuation of the shutoff valve 21b.

The separating column 28 is provided with a reboiler 29 at the bottom thereof for evaporating the column bottom liquid into an ascending gas, and at the top thereof liquefied oxygen, liquefied nitrogen, liquefied argon,
Condenser 3 for generating reflux liquid using liquefied air as a cold source
0 is provided. In addition, the reboiler 29,
Like the concentration tower 3 and the deoxygenation tower 23, at a predetermined temperature and pressure,
For example, nitrogen gas may be introduced as a heating source.

The mixed liquefied gas consisting of krypton and xenon introduced into the middle stage of the separation column 28 separates krypton having a purity of 99.99% or more at the top of the column by rectification in the column and has a purity of 99.99 at the bottom of the column. % Or more of xenon is separated in liquid form. Oxygen as an impurity is 1 ppm or less, and hydrocarbons are also 1 ppm or less.

The separated krypton is led out from a pipe 31 provided under the condenser 30 or at the upper part of the column, and xenon is led out from a pipe 32 provided at the bottom of the column, and sent to a filling process (not shown) to a predetermined state. Fill the gas container. The krypton withdrawal pipe 31 provided in the upper part of the column may be withdrawn from the rectification stage one to several stages below the column top.

From the tower top of the separation tower 28, oxygen 1
A small amount of krypton gas containing 10 ppm is extracted and circulated through the conduit 33 to the middle or lower part of the deoxygenation tower 3 for complete recovery of krypton.

Further, for example, liquefied oxygen liquefied in the reboiler 5 of the concentration tower 3 is deoxidized tower 23 and separation tower 28.
It is used as a cold source for the condensers 25 and 30 of the above, but a refrigerant liquefied gas storage tank 36 is provided so that the usage amount can be adjusted.

In the present invention, krypton and xenon are separated from liquefied oxygen in the minimum necessary steps as shown in the above-mentioned examples, so that a high purity can be obtained without complicated operations in a continuous process with a small number of steps. It is possible to obtain purified krypton and xenon. Further, it is possible to prevent the danger due to the concentration of hydrocarbons in the concentration step and safely perform continuous operation.

[0039]

Industrial Applicability As described above, the method for purifying krypton and xenon of the present invention reduces the number of steps for krypton and xenon in liquefied oxygen derived from an air liquefaction separation device, and makes them safe in a continuous and consistent process. Efficiently, 99.9
It can be purified to a high purity of 9% or more, and the production cost of these gases can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a refining device for carrying out the method of the present invention.

[Explanation of symbols]

1 ... Double rectification tower, 3 ... Concentration tower, 5 ... Concentration tower reboiler, 6
Concentration tower condenser tower, 8 ... Concentration tower heat exchanger, 9 ... Line pumps, 11a, 11b ... Hydrocarbons analyzer, 13 ... Catalyst tower heat exchanger, 14 ... Heater, 15 ... Catalytic reaction tube, 18 …
Adsorber, 22 ... Heat exchanger, 23 ... Deoxidizing tower, 24 ... Deoxidizing tower reboiler, 24b ... Oxygen concentration analyzer, 25 ... Deoxidizing tower condenser, 26 ... Mixed liquefied gas container, 27 ... Liquefied gas for refrigerant Container, 28 ... Separation tower, 29 ... Deoxygenation tower reboiler, 30 ... Deoxygenation tower condenser

Claims (4)

[Claims] 1. A method for purifying krypton and xenon from liquefied oxygen containing krypton and xenon, which is discharged from an air liquefaction separation apparatus, wherein the liquefied oxygen is introduced into a concentration column to concentrate krypton and xenon in a bottom liquid. A step, a catalytic reaction step of vaporizing the bottom liquid of the concentrating column and introducing it into the catalytic reaction tube to react the contained hydrocarbons with oxygen, and introducing the gas after the catalytic reaction tube is introduced into the adsorber. After the adsorption step of adsorbing and removing water and carbon dioxide generated in the catalytic reaction step, and after cooling the gas after the derivation of the adsorption step again 2
Separation and reintroducing one of them into the lower part of the concentrating tower and controlling the amount of the krypton- and xenon-containing gas introduced after the catalytic reaction step of reintroducing into the lower part of the concentrating tower are performed by carbonizing the bottom liquid of the concentrating tower. The content of hydrogens or the content of hydrocarbons in the gas containing krypton and xenon before being introduced into the catalytic reaction step of reacting the contained hydrocarbons with oxygen is detected, and the detected hydrocarbons The step of performing according to the content of, the other branched is introduced into the deoxygenation column for rectification separation, oxygen gas containing a small amount of krypton is derived from the top of the column, and krypton and xenon A deoxidation step of distilling the mixed liquid and a deoxidation tower bottom liquid are introduced and introduced into a separation tower, and krypton is taken out from the top of the separation tower and xenon is taken out from the tower bottom, respectively. Krypton characterized by Purification method of fine-xenon. 2. The catalytic reaction step of reacting the hydrocarbons introduced into the catalytic reaction tube and contained therein with oxygen uses a copper-chromium composite catalyst as the catalyst. Method for purifying krypton and xenon. 3. The method for purifying krypton and xenon according to claim 1, wherein a part or all of the krypton-containing oxygen gas discharged from the top of the deoxygenation column is reintroduced into the concentration column. 4. The method for purifying krypton and xenon according to claim 1, wherein a part or all of the oxygen-containing krypton gas discharged from the top of the separation column is reintroduced into the concentration column.