JP3424100B2 - Method for purifying krypton and xenon - Google Patents

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, and after the concentrated krypton and xenon are purified,
High-purity products are collected separately.

Usually, these apparatuses repeat a rectification step, a catalytic reaction step, and an adsorption step, and krypton 9 by rectification.
After obtaining a concentrated solution of 0-95% and xenon 5-10%,
Finally, krypton and xenon are separated. That is, the step of concentrating the liquefied oxygen after the main condenser / evaporator of the double rectification column is concentrated, the methane purge step, the first catalyst step, the first step
Adsorption step, deoxidation step, second catalyst step, second adsorption step,
The final products, krypton and xenon, were obtained through the separation process.

[0004]

However, the amount of krypton and xenon contained in the atmosphere is 1.1, respectively.
Since it is an extremely small amount of 4 ppm and 0.086 ppm, it is not possible to continuously perform a purification step of concentrating it and finally removing other air components to 1 ppm or less, and an apparatus having a consistent purification step. Was difficult to make.

In view of the above, the present invention pays attention to the fact that the catalyst step and the adsorption step are repeatedly carried out in the conventional method, omitting the catalyst / adsorption step subsequent to the deoxygenation tower, and shortening all steps, and , A purification method capable of purifying contained impurities to 1 ppm or less, efficiently separating the above krypton and xenon with a minimum number of steps, and obtaining highly purified krypton and xenon. It is intended to be provided.

[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. An adsorption step of adsorbing and removing the produced water and carbon dioxide, and cooling the gas after the derivation of the adsorption step again and introducing it into the deoxygenation tower so that the gas-liquid ratio L / V of the concentrating section is 0.1 or more and the recovering section. Gas-liquid ratio L
/ V is 1.0 or more and rectification is performed to deoxidize and remove oxygen gas from the top of the column, and deoxygenation column bottom liquid is derived and introduced into a separation column, and xenon is introduced from the bottom of the separation column. And a separation step of deriving krypton from the top of the tower are sequentially performed.

Further, in the method of the present invention, in the catalytic reaction step of reacting the hydrocarbons introduced into the catalytic reaction column and oxygen with each other, a precious metal element such as platinum or palladium is used for the catalyst, and the reaction temperature is 200-650 ° C, preferably 35
The feature is that the reaction is performed at ⁰ to 400 ° C. and a space velocity of 500 to 6000 h ⁻¹ .

The reaction temperature is set by operating a temperature controller (TIC) in response to a signal from a temperature detector provided at the outlet of the heat exchanger in the front stage of the catalyst reaction tube or the outlet of the catalyst reaction tube, and the control valve is activated by the signal from this. The heat medium supply amount is controlled by opening and closing, and the temperature of the warmer provided at the inlet of the catalytic reaction tube is adjusted to set it to an appropriate temperature.

The space velocity is set by controlling the opening of the flow rate control valve based on the flow rate detected by the flow rate detector and the signal from the flow rate controller (FIC) that receives the signal.

If necessary, an analyzer for detecting and quantifying the content of hydrocarbons in the krypton- and xenon-containing gas is provided, and carbonization after or before the catalytic reaction step detected by the analyzer is carried out. The reaction conditions of the catalytic reaction tube are set based on the hydrogen content. At this time, the hydrocarbon concentration at the outlet of the catalytic reaction tube is 0.05 ppm or less.

The apparatus for carrying out the method of the present invention is an apparatus for purifying krypton and xenon from liquefied oxygen containing krypton and xenon derived from the main condenser of the air liquefaction separation device or the vicinity thereof. There, a concentration column for introducing the liquefied oxygen to concentrate krypton and xenon in the bottom liquid, and a catalyst reaction column for reacting the hydrocarbons and oxygen contained by introducing the bottom liquid of the concentration column after vaporization And an adsorber for introducing gas after the catalyst reaction tube is introduced to adsorb and remove water and carbon dioxide generated in the catalyst reaction tube,
The gas after being discharged from the adsorber is cooled again to remove and remove oxygen gas from the top of the column, and the krypton / xenon mixed liquid is separated at the bottom of the column. It is characterized by comprising a stage deoxygenation column and a separation column for introducing the bottom liquid of the deoxygenation column for rectification and separation, and for extracting xenon from the bottom of the column and krypton from the top of the column.

[0012]

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

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the embodiments shown in the drawings. First, 30 to 600 ppm of krypton and 5 to 50 pp of xenon 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.
m, and hydrocarbon (mainly methane) 20-150p
Liquefied oxygen enriched with pm is led out, and the main condenser evaporator 1a
It is introduced into the middle stage of the concentration tower 2 installed below.

A reboiler 4 using a nitrogen gas, an oxygen gas or an argon gas supplied from a pipe 3 as a heating source is provided at the bottom of the concentration tower 2, and liquefied oxygen supplied from a pipe 5 is provided at the top. A condenser 6 having a cold source such as the above is provided. In the concentration tower 2, the descending liquid from the top of the tower and the ascending gas come into gas-liquid contact to carry out rectification. That is, the reboiler 4 heats the bottom liquid to generate rising gas, and the reflux liquid cooled and generated by the condenser 6 descends to come into gas-liquid contact with the rising gas for rectification. .

As a result, the liquefied oxygen containing krypton and xenon introduced from the double rectification column 1 is obtained as a concentrated liquid obtained by concentrating krypton and xenon 10 to 100 times at the bottom of the concentration column 2. Oxygen gas is led to the pipe 7 from the top.

In the concentrated liquid at the bottom of the above-mentioned concentrating tower 2, in addition to krypton and xenon, hydrocarbons (methane) contained in liquefied oxygen as a raw material are also concentrated, which is dangerous when the methane concentration is increased. Therefore, a methane purge tower is provided as needed, and stripping is performed in this methane purge tower to purge methane.

The bottom liquid derived from the concentration tower 2 through the pipe 8 is
The liquid is introduced into the liquid storage tank 9, temporarily stored therein, and is discharged at a flow rate suitable for the reaction condition in the catalytic reaction step described later. That is, the concentrated liquid introduced into the liquid storage tank 9 and temporarily stored is discharged from the pipe 10 and operated by the flow rate measured by the flow rate detector 35 (see FIG. 2).
The flow rate is adjusted by a flow rate control valve 11 that opens and closes in response to a signal from 6 and is introduced into the warmer 12.

When the amount of the bottom liquid discharged from the concentrating column 2 is small, the subsequent liquid storage in the liquid storage tank 9 is stopped until the rectification separation is possible in the subsequent process. And store it,
When the amount of rectification separation becomes possible in the subsequent step, it is led from the pipe 10 to the warmer 12.

Therefore, if the amount of the bottom liquid constantly discharged from the concentration tower 2 is an appropriate amount, the liquid storage is not always necessary.

The concentrated liquid is filled with a liquid medium, vaporized and heated by the warmer 12 which heats the liquid medium with steam or a heater, and is introduced into the heat exchanger 14 through the pipe 13, and the catalyst reaction tube is introduced. The heat is exchanged with the gas after the catalytic reaction, which is discharged from 17 to the pipe 18 at a high temperature to raise the temperature, and further enters the heat exchanger 15 heated by the warmer 16 and is discharged at a predetermined catalytic reaction temperature,
It is introduced into the catalytic reaction cylinder 17.

In the catalytic reaction cylinder 17, a step of removing hydrocarbons is carried out. The catalytic reaction column 17 is filled with a predetermined amount of a noble metal catalyst such as platinum (Pt) or palladium (Pd), and hydrocarbons in the vaporized gas of the bottom liquid of the concentrating column (in some cases, methane purging column). Is reacted with oxygen to carbon dioxide and water. The predetermined amount of the catalyst is a sufficient amount so that the residual concentration after reacting the introduced hydrocarbons and oxygen with each other to form carbon dioxide and water is, for example, 0.05 ppm or less.

Further, in the hydrocarbon removing step, the reaction conditions in the catalytic reaction step are accurately set so that the reaction is sufficiently carried out and the contained hydrocarbon has the above-mentioned residual concentration.

The reaction conditions are set by setting the reaction temperature and space velocity. First, the reaction temperature is set to an appropriate temperature by adjusting the operation of the warmer 16 provided at the inlet of the catalytic reaction tube 17, and the hydrocarbon concentration at the outlet of the catalytic reaction tube 17 is
For example, it is set to 0.05 ppm or less. That is, the temperature controller (TIC) 3 is generated by a signal from the temperature detector 37 provided at the outlet of the heat exchanger 15 or the catalytic reaction cylinder 17.
8 operates, and the control valve 39 opens and closes by a signal from this to control the heat medium supply amount, thereby controlling the outlet temperature. The usual temperature range is 200 to 650 ° C, preferably 350 to 400 ° C.

The space velocity is set by adjusting the opening of the flow rate control valve 11. That is, the opening is controlled by the flow rate detected by the flow rate detector 35 and the signal from the flow rate controller 36 that receives the flow rate to control the opening of the flow rate adjustment valve 11. The space velocity in the catalytic reaction cylinder 17 by this adjustment is in the range of 500 to 6000 h ^-1 .

If necessary, an analyzer for detecting and quantifying the content of hydrocarbons in the gas containing krypton and xenon is provided, and the content of hydrocarbons at the point after the catalytic reaction step detected by the analyzer is included. The reaction conditions of the catalytic reaction cylinder 17 may be set based on the amount.

The gas discharged from the catalytic reaction cylinder 17 through the pipe 18 is cooled in the heat exchanger 14 and then introduced into one of the adsorbers 19 which are used for switching, so that carbon dioxide and water generated in the catalytic reaction step are generated. Adsorbed and removed. In addition, the adsorber 1
Since the operation of 9 is continuous, two groups are switched and used, and when one is in the adsorption step, the other is in the regeneration step. The regeneration process of the adsorber 19 includes a heating regeneration process performed by introducing heated nitrogen gas into the adsorber, a cooling process performed by introducing nitrogen gas at room temperature, and a cleaning process performed by introducing oxygen gas. Done by.

The gas led to the pipe 20 from the above hydrocarbon removing step is introduced into the heat exchanger 21 and flows countercurrently to the pipe 21.
It is cooled by heat exchange with oxygen, nitrogen, argon or air of low temperature gas or liquid from a, cooled or liquefied and introduced into the middle stage of the deoxygenation tower 22. It goes without saying that the liquefied gas introduced from the pipe 21a of the heat exchanger 21 may be the liquefied gas discharged from the reboiler 4 of the concentrating tower 2.

In the case of a stage column such as a sieve tray, the deoxygenation column 22 has a total number of actual stages of the concentration section and the recovery section of 10 or more,
Preferably, 20 to 40 rectification stages are provided. Even in a packed column filled with a packing material or the like, the same rectification effect can be obtained by setting the column length corresponding to the above number of stages. A reboiler 23 using oxygen gas or the like as a heating source is provided at the bottom of the tower, and a condenser 24 using the liquefied oxygen liquefied by the reboiler 23 as a cold source is provided at the top of the tower.

When the cold balance is insufficient due to the heat balance of the deoxygenation tower 22, the cold source of the condenser 24 is the reboiler 23.
In addition to the liquefied gas from the above, the liquefied gas from the reboiler 4 and the like of the concentration tower 2 is also supplied as a cold source.

The gas as the heating source of the boiler 23 of the deoxidizing tower 22 is the same as in the concentrating tower 2, and nitrogen, oxygen,
Argon, air or the like can be used after being pressurized to an appropriate pressure.

By the rectification in the deoxygenation tower 22, oxygen gas containing 1 to 5 ppm of krypton is separated at the top of the tower and is removed from the pipe 25 and removed, and 90 to 95% of krypton and xenon are at the bottom of the tower. A liquefied gas consisting of 5 to 10% of an extremely small amount of oxygen is separated. The amount of oxygen remaining in the bottom liquid depends on the number of stages of the deoxygenation column 22 and the gas-liquid ratio L / V, but by setting the number of stages to 5 or more in the recovery section, the amount of residual oxygen can be 1 ppm or less. . Therefore, in order to reduce the oxygen content in the krypton after separation in the separation tower 27 to be described later to about 1 ppm or less, the deoxidation tower 22 needs 6 or more stages in the recovery section, and the oxygen content in about 11 stages. 0.0
It becomes less than 01 ppm.

In this case, the gas / liquid ratio L / V of the concentrating section is 0.1.
That is all. It is preferably within the range of 0.1 to 1.1. The reason for this will be explained. As shown in FIG. 3, the deoxygenation tower 22 comprises a concentration section 22a above the feed stage 20a and a recovery section 22b below. The amount of oxygen remaining in the bottom liquid of the deoxygenation tower 22 is determined by the number of stages of the recovery section 22b and the gas-liquid ratio L / V.

Now, as shown in parentheses in FIG. 3, the amount of introduction and withdrawal of each part and the flow rates of gas (V) and liquid (L) in the tower are set, and the gas-liquid ratio L / V of the recovery part 22b is set. = 1.1, the gas-liquid ratio L / V of the concentrating section 22a becomes 0.1 (when the gas-liquid ratio L / V of the concentrating section 22a is 0.1 or less,
Fractional separation of krypton and oxygen is not established, and stripping occurs and the function of the deoxygenation tower is lost. ).

When the content of krypton and xenon in the feed gas is 1%, the number of theoretical plates in the recovery section 22b must be at least 8 in order to reduce the oxygen concentration in the bottom liquid to 1 ppm or less under the above conditions. is there.

Similarly, the content of krypton and xenon in the feed gas is 1%, the gas-liquid ratio L / V of the concentrating section 22a is 0.5, and the gas-liquid ratio of the collecting section 22b is L / V = 1. 0
When it is set to 1, the number of theoretical plates in the recovery section 22b must be at least 6 in order to set the oxygen concentration in the bottom liquid of the deoxidizing column to 1 ppm or less.

Therefore, the gas-liquid ratio L / V of the concentration section 22a is
Is 0.1 or more, the number of theoretical stages of the recovery unit 22b is 8, and the actual number of stages is 10.

The gas-liquid ratio is adjusted by adjusting the reboiler 23.
It is carried out by adjusting the amount of heating by and the amount of cold supply by the condenser 24.

The liquefied gas at the bottom of the column is introduced into the pipe 26 and then introduced into the middle stage of the separation column 27 for rectifying and separating krypton and xenon. The separating column 27 is provided with a reboiler 28 for evaporating the column bottom liquid into an ascending gas at the bottom thereof, and produces a reflux liquid with liquefied oxygen, liquefied nitrogen, liquefied argon, liquefied air, etc. at the top as a cold source. A condenser 29 is provided to allow it. As the heat source of the reboiler 28 of the separation tower 27, nitrogen gas, oxygen gas or argon gas may be adjusted to a predetermined temperature and pressure and introduced like the heat sources of the reboiler of the concentration tower 2 and the deoxygenation tower 22. As the cold source of the condenser 29, liquefied gas liquefied by the reboiler 28 may be used, or liquefied nitrogen or liquefied argon, liquefied air, etc. liquefied by the reboiler 4 of the concentrating tower 2 may be used.

The mixed liquefied gas consisting of krypton and xenon introduced into the middle stage of the separation column 27 is rectified in the column to separate krypton having a purity of 99.99% or more at the column top and 99.99% at the column bottom. 99% or more of xenon is separated in liquid form. Oxygen as an impurity is 1 ppm or less,
Hydrocarbons are also below 1 ppm.

The above krypton and xenon are led out from a pipe 31 and a pipe 32, respectively, sent to a filling process (not shown), and filled in a predetermined gas container.

In the present invention, high-purity krypton and xenon are separated from liquefied oxygen in the minimum necessary and shortest steps as shown in the above-mentioned embodiment. It is possible to obtain purified krypton and xenon.

[0042]

As described above, according to the present invention,
Efficiently purify krypton and xenon in liquefied oxygen derived from the air liquefaction separation device in a continuous and consistent process, and remove impurities such as oxygen, nitrogen, and hydrocarbons to less than 1 ppm to achieve a high purity of 99.99% or more. It is possible to purify, and it is possible to significantly reduce the production cost of these gases.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a control system.

FIG. 3 is an explanatory view showing a gas-liquid ratio in the separation column.

[Explanation of symbols]

1 ... Double rectification tower, 2 ... Concentration tower, 4 ... Concentration tower reboiler, 6
… Condensation tower condenser, 9… Liquid storage tank, 11… Flow control valve, 12
... heater, 14 ... heat exchanger, 15 ... heat exchanger, 16 ... warmer, 17 ... catalytic reaction column, 19 ... adsorber, 21 ... heat exchanger, 22 ... deoxidation tower, 23 ... deoxidation Tower reboiler, 24
... Deoxidizer tower condenser, 27 ... Separation tower, 28 ... Separation tower reboiler, 29 ... Separation tower condenser

Continuation of the front page (56) Reference JP-A-57-43186 (JP, A) JP-A-5-79756 (JP, A) JP-A-5-280863 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) F25J 3/04 104

Claims (3)

(57) [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. The adsorption step of adsorbing and removing water and carbon dioxide produced in the catalytic reaction step, and the gas after the adsorption step is cooled again and introduced into the deoxidizing tower to adjust the gas-liquid ratio of the concentrating section to 0.1 or more. Performing rectification, deoxygenation step of removing and removing oxygen gas from the top of the tower, derivation of bottom liquid of the deoxygenation tower and introduction into a separation tower, xenon from the bottom of the separation tower, and krypton from the top of the tower. And the separation process Krypton and purification methods xenon characterized by Ukoto. 2. In the catalytic reaction step of reacting the hydrocarbons contained in the catalytic reaction tower with oxygen, the precious metal element is used as the catalyst, the reaction temperature is 200 to 650 ° C., and the space velocity is 500 to 6000 h. ^The method for purifying krypton and xenon according to claim ¹ , wherein the reaction is carried out at ^-1 . 3. An apparatus for purifying krypton and xenon from liquefied oxygen containing krypton and xenon derived from an air liquefaction separation apparatus, wherein the liquefied oxygen is introduced to concentrate krypton and xenon in a bottom liquid. A catalyst reaction tube for reacting the contained hydrocarbons with oxygen after vaporizing the bottom liquid of the concentrating column; and water and dioxide produced in the catalyst reaction tube by introducing the gas after derivation of the catalyst reaction tube. An adsorber that adsorbs and removes carbon, and a gas that has been discharged from the adsorber is cooled and introduced again to carry out rectification, oxygen gas is discharged and removed from the top of the tower, and a krypton-xenon mixture is separated at the bottom of the tower. A deoxygenation column in which the number of theoretical plates in the recovery section is equal to or greater than 5 and a separation column in which the bottom liquid of the deoxygenation column is introduced to carry out rectification to separate xenon from the column bottom and krypton from the column top. Characterized by having A krypton and xenon refining device.