JP3364724B2 - Method and apparatus for separating high purity argon - 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 separating high-purity argon and an apparatus therefor, and more specifically, a method for separating and collecting component gases such as oxygen, nitrogen and argon from air as a raw material by rectification separation. Regarding the device.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional method for collecting high-purity argon by a cryogenic air separation method. From the middle stage of the low pressure column (upper column) of the double rectification column 1, substantially 5 to 15% of argon and a small amount of nitrogen as a raw material gas are extracted into a conduit 2 and introduced into the lower part of the crude argon column 3 substantially. To be done.
A condenser 4 is provided in the upper part of the crude argon column 3, and the liquid air extracted from the lower part of the intermediate pressure column (lower column) of the double rectification column 1 and having a low pressure in the expansion valve 5 is It is introduced from the conduit 6 as a cold source. As a result, the crude argon column 3
The raw material gas having risen to liquefies into a reflux liquid in the condenser 4, and liquefaction rectification is performed with the raw material gas rising in the column, and 90% or more of argon and several percent of oxygen or less from the top of the column, Crude argon having a composition of several% or less of nitrogen is extracted into the conduit 7. On the other hand, from the bottom of the crude argon column 3, liquid oxygen is returned to the upper column through the pipe 8, and the gas obtained by vaporizing liquid air in the condenser 4 is introduced into the upper column through the pipe 9.

The crude argon discharged to the pipe 7 passes through the heat exchanger 10 and cools the return gas to a substantially atmospheric temperature.
It is sent from a pipe 11 to a compressor 13 via a gas holder 12 which also serves as a storage tank and a buffer. The crude argon gas compressed by the compressor 13 to a pressure necessary for the subsequent process is discharged into the pipe 14, and the oxygen content in the crude argon is removed by the oxygen / hydrogen reaction from the hydrogen supply facility 15 through the pipe 16. After sufficient hydrogen has been added, the hydrogen is introduced into the catalyst cylinder 17. The catalyst cylinder 17 is filled with a catalyst that promotes the oxygen-hydrogen reaction, and as a result, oxygen in the crude argon reacts quickly with the added hydrogen to produce water. The crude argon gas containing the produced water is sent to the water separator 19 through the pipe 18 after being cooled, and is further introduced into the switching dryer 21 through the pipe 20. In this drying step, the generated crude argon gas from which water has been removed is introduced into the heat exchanger 10 through the pipe 22, cooled, and introduced into the middle stage of the high purity argon column 24 through the pipe 23.

A reboiler 26 using a medium-pressure nitrogen supplied from the lower column of the double rectification column 1 through a pipe 25 as a heating source is provided in the lower part of the high-purity argon column 24, and is condensed in the upper part. A container 31 is provided. In this condenser 31,
After being condensed and liquefied by the reboiler 26, the liquid nitrogen expanded by the valve 27 and supplied from the pipe 28 and the liquid nitrogen supplied from the lower column of the double rectification column 1 through the pipe 29 and the valve 30 are supplied. ing. This high-purity argon tower 24 is the same as the tube 23
The crude argon introduced from is rectified, the mixed gas of nitrogen and hydrogen is separated at the top of the column, and the mixed gas is discharged from the pipe 32.
High-purity liquid argon is separated at the bottom of the column, and the high-purity liquid argon is collected through a pipe 33.

The pipe 34 is a discharge pipe for the nitrogen gas that is vaporized as a result of the cooling provided by the condenser 31, and joins with the pipe 35 for the nitrogen gas that is discharged from the top of the upper part of the double rectification column 1.

As is clear from the above description, the conventional high-purity argon sampling method uses dangerous hydrogen in the deoxidation step, and the drying step accompanying it complicates the equipment, piping, etc. Moreover, there are drawbacks such as complicated operation. Further, with the recent increase in size of the apparatus, it is clear that the above-mentioned drawbacks will increase more and more, and the solution thereof has been desired.

On the other hand, a method of purifying argon by removing oxygen in crude argon without using hydrogen is disclosed in Japanese Examined Patent Publication No.
It is disclosed in Japanese Patent No. 41235. FIG. 4 shows steps for carrying out the method described in the publication, in which 90% of the argon extracted from the crude argon column 3 into the tube 101 was used.
As described above, crude argon containing several% of each of oxygen and nitrogen is introduced into the deoxygenation tower 102 in order to remove contained oxygen.
This deoxygenation tower 102 is provided with a reboiler 103 at the bottom and a condenser 104 at the top in order to exert a rectification action, and the rectification section between them has a small boiling point difference and is difficult to rectify and separate. To rectify and separate argon and
The rectification action is formed as a multistage of several tens of stages, and the pressurizing means 105 for the pressure resistance generated thereby is arranged in front of the deoxygenation column 102.

The reboiler 103 is formed by supplying medium pressure nitrogen gas from the lower column of the double rectification column 1 through a pipe 107, and the condenser 104 at the top is provided with the reboiler 10.
The medium-pressure nitrogen liquefied in 3 is supplied through the pipe 109 after being expanded by the valve 108 and adjusted to an appropriate pressure in order to maintain the temperature so that argon does not solidify in the deoxygenation tower 102. Further, liquid nitrogen is supplied to the condenser 104 from the lower column of the double rectification column 1 through a pipe 111 after adjusting to a proper pressure by the valve 110 in the same manner as above. As a result, the oxygen content from the upper part of the deoxygenation tower 102 is several pp.
Purified argon having an argon content of several percent and a nitrogen content of about 95% is extracted into the tube 112 and sent to the high purity argon column 24.

The high-purity argon column 24 is the same as that shown in FIG. 3, and the medium pressure nitrogen extracted from the lower column of the double rectification column 1 is supplied to the bottom of the column by a pipe 25 to reboiler 26.
Liquid nitrogen condensed and liquefied by the reboiler 26 is supplied to the upper part through a pipe 28 and a valve 27, and the lower part of the double rectification column 1 is sent to the condenser 104 of the deoxygenation column 102. A part of the liquid nitrogen from the tower is pressure-adjusted by a valve 30 and sent through a branch pipe 29 to form a condenser 31.

As a result of rectification in the high-purity argon column 24, nitrogen gas containing a small amount of argon is discharged from the column top through a pipe 32, and high-purity liquid argon is collected from the bottom through a pipe 33. On the other hand, the nitrogen gas vaporized in the condenser 31 is discharged through the pipe 34, and the condenser 10 of the deoxygenation tower 102 is discharged.
The nitrogen gas pipe 3 discharged from the top of the upper part of the double rectification column 1 together with the nitrogen gas vaporized in 4 and discharged to the discharge pipe 114.
It merges with 5 and is collected.

[0011]

According to the method using the above deoxidizing tower, it is possible to collect argon having an oxygen content of about several ppm, but in recent years there has been a demand for high purity of various gases. Has an oxygen content of 1 pp even in argon gas
A value of m or less is desired, and in the case of argon for the semiconductor industry, the oxygen content is approaching the order of ppb. In addition, the yield of argon in the raw material air is required to be in the range of 80 to 90%, and the demand for high purification and high efficiency is becoming stronger.

It is a very common method to increase the number of rectification stages in order to reduce the oxygen content in high-purity argon without lowering the yield. You need to deal with the loss. Also, in order to increase the reflux ratio and obtain the same effect, it is necessary to increase the capacity of the reboiler and condenser of the deoxygenation tower, but the reboil source of the deoxygenation tower and the cooling source of the condenser are Normally, gas nitrogen and liquid nitrogen from the lower tower are used, so if the usage of these gas nitrogen and liquid nitrogen increases, the amount of reflux liquid supplied from the lower tower to the upper tower will decrease, The rectification separation effect is deteriorated, and the separation effect of the air separation device as a whole is deteriorated.

In the above conventional method, the crude argon column 3 for concentrating argon, the pressurizing means 105, the deoxygenating column 102 for separating oxygen, and the high-purity argon column (denitrifying column for separating nitrogen) 24 are arranged in this order. Since it is installed, in order to obtain an appropriate operating pressure in the final high-purity argon column, the pressure of the deoxygenating column in the previous stage should be adjusted to a pressure corresponding to it, that is, a pressure with a height to compensate for the pressure loss. Therefore, it is a disadvantageous condition for a deoxygenation tower for rectifying and separating oxygen and argon having a small boiling point difference.

Therefore, the present invention simplifies the structure of the apparatus for separating and collecting high-purity argon by liquefaction rectification using air as a raw material, and at the same time, makes it possible to improve the purity and yield.
In particular, it is an object of the present invention to provide a method for separating high-purity argon and an apparatus therefor capable of operating more efficiently than before in terms of the number of theoretical plates required for the deoxygenation tower and the reflux ratio.

[0015]

In order to achieve the above object, the method for separating high-purity argon of the present invention comprises compressing, purifying and cooling air, and liquefying and rectifying oxygen and nitrogen in a double rectification column. Along with collecting, in the method of separating high-purity argon by air liquefaction separation to collect high-purity argon, the argon-containing gas derived from the double rectification column is introduced into the crude argon column for rectification, and a small amount of nitrogen and Crude argon containing oxygen, and then the crude argon was introduced into a denitrification tower for rectification, and nitrogen was separated and led out from the top of the tower, and then the denitrogenated crude argon drawn from the bottom of the denitrification tower was introduced into the deoxygenation tower. It is characterized in that it is introduced and rectified, oxygen is separated from the bottom of the column, and high-purity argon is collected from the top of the column.

The apparatus for separating high-purity argon of the present invention comprises a double rectification column for liquefying and rectifying compressed, purified and cooled air into oxygen and nitrogen, and a middle part of the upper column of the double rectification column. A crude argon column for rectifying the derived argon-containing gas to obtain crude argon containing a small amount of nitrogen and oxygen, and rectifying the crude argon derived from the top of the crude argon column to separate and separate nitrogen from the top of the column. And a deoxygenation tower for rectifying the denitrification crude argon derived from the tower bottom of the denitrification tower to separate and derive oxygen from the tower bottom, and to collect high-purity argon from the top of the tower. It is characterized by having.

[0017]

[Operation] As described above, when separating high-purity argon by separating nitrogen and oxygen contained in the crude argon, a denitrification tower for separating nitrogen is provided upstream of the deoxygenation tower for separating oxygen. By configuring to separate nitrogen first, the operating pressure of the deoxygenation tower can be lowered,
Oxygen can be efficiently separated. Further, nitrogen has a large boiling point difference with argon and oxygen and can be sufficiently removed even if the pressure is somewhat high, so that it can be set to an arbitrary pressure according to the pressure of the deoxidizing column in the subsequent stage.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG. The same elements as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. The liquid crude argon extracted from the top of the crude argon column 3 into the pipe 51 at a pressure of about 1.1 ata is a pressure cylinder (liquid column pressurizer) as a pressurizing means.
At 52, the pressure is raised to 1.7 to 2.0 at a liquid head of its own, and then introduced into the middle stage of the denitrification tower 55 through a pipe 53 and a valve 54. At the bottom of the denitrification tower 55, there is provided a reboiler 57 to which the medium pressure nitrogen extracted from the lower tower of the double rectification tower 1 is supplied via a pipe 56, and at the top thereof is liquefied by the reboiler 57. A condenser 60 is provided in which liquefied nitrogen is introduced via a pipe 58 and a valve 59.

In the denitrification tower 55, the crude argon supplied from the pipe 53 is rectified, nitrogen is separated at the top of the tower to be led out from the pipe 61, and denitrogenated liquid crude argon is fed to the pipe 62 at the bottom of the tower. Derive.

The denitrogenated liquid crude argon is introduced from the pipe 62 through the valve 63 into the middle stage of the deoxygenation tower 64. At the top of this deoxygenation tower 64, a pipe 65 is installed from the lower tower of the double rectification tower 1.
A condenser 67 is provided which is supplied with the medium pressure liquid nitrogen extracted in the above and the liquefied nitrogen which is liquefied by the reboiler of the denitrification tower 55 and branched into a pipe 66, and the condenser 67 is provided at the bottom of the tower.
After being vaporized by the heat exchanger and heated by the heat exchanger 68, the circulating compressor 69 is used.
After pressurizing with, after cooler 70 and the heat exchanger 68
A reboiler 71 to which the nitrogen gas whose temperature has been lowered is supplied is provided. The liquefied nitrogen liquefied by the reboiler 71 is reduced in pressure by the valve 72 and merges with the medium pressure liquid nitrogen of the pipe 65. In addition, the nitrogen gas vaporized in the condenser 60 of the denitrification tower 55 and the condenser 67 of the deoxygenation tower 64 is stored in the pipe 7
3, double rectification column 1 via valve 74 or pipe 75, valve 76
It joins the pipe 35 for nitrogen gas discharged from the top of the upper column.

By the rectification in the deoxygenation tower 64, oxygen is separated at the bottom of the tower and is led out from the pipe 77, and the high-purity argon separated at the top of the tower is taken from the pipe 78. The oxygen led to this pipe 77 may be returned to the double rectification column 1.

As described above, the nitrogen in the crude argon is first separated and removed, and then the oxygen is separated, so that the operating pressure of the deoxygenation tower 64 is rectified and separated into argon and oxygen. The pressure can be adjusted to suit. That is, conventionally, the denitrification column (high-purity argon column) was placed next to the deoxygenation column, so the operating pressure of the deoxygenation column is limited by the operating pressure of the next denitrification column. However, in the present invention, since nitrogen is separated first, such a limitation is eliminated, and the operating pressure of the deoxidizing column 64 can be set to a low pressure, for example, about 1.1 ata.
Therefore, it is possible to rectify and separate argon and oxygen having a small boiling point difference under the optimum conditions, and not only to obtain high-purity argon having an oxygen content of 1 ppm or less, but also to advantage in terms of the required theoretical plate number and reflux ratio. Therefore, the device can be downsized and the power can be reduced.

Further, the deoxygenation tower 64 is a packed tower in which the rectification section is filled with a regular or irregular packing material, whereby the pressure loss during the rectification operation can be reduced. For example, the oxygen content is 1 ppm or less. In order to remove up to 150, the number of theoretical plates together with the crude argon column 3 is required to be 150 or more,
By using such a packed column with a small pressure loss, the operating pressure can be further lowered, and economical operation can be performed.

On the other hand, since the rectification in the denitrification tower 55 separates nitrogen, argon and oxygen, which have a large difference in boiling points, the nitrogen is easily removed even if the deoxygenation tower 64 is operated at a sufficiently high pressure. Can be separated into Further, as shown in the present embodiment, the positional relationship between the crude argon column 3 and the denitrification column 55 is taken into consideration, and the liquid column pressurizer 52 is used as the pressurizing means, so that the power for pressurization is increased. There are advantages that are not needed.

A cooling source for each condenser and reboiler,
The heating source is arbitrary, and liquid air drawn from the lower part of the lower tower can also be used as the cooling source, and a cold source such as liquid nitrogen may be introduced from outside the device. Also, as the heating source, it is possible to use air or an air-like composition gas derived from the lower part of the lower column, or a part of the raw material air before introduction into the lower column. The liquid or gas used for these cooling source and heating source can be appropriately selected according to the type, form, amount, etc. of the product set in this air liquefaction separation device. Yields of high-purity argon, oxygen, nitrogen, etc. can be obtained by using an optimal type of liquid or gas depending on the rectification operating conditions of the upper tower, or by introducing these from a device other than the device concerned. It is possible to perform efficient operation without damaging the. For example, when an air separation device for collecting liquid products is provided with a circulation system for generating cold, it is possible to incorporate a cooling source and a heating source in the system.

Regardless of which liquid or gas is used as the cooling source or the heating source, by adjusting the temperature and flow rate of the cooling source introduced into the condenser and the temperature and flow rate of the heating source introduced into the reboiler, the deoxidation tower The reflux ratio in 1 can be set to an optimum state, whereby the oxygen content in the argon sampled from the deoxygenation tower can be reduced to 1 ppm or less.

As described above, in this embodiment, the amount of oxygen in the high-purity argon sampled from the deoxygenation tower was 1 ppm.
However, if it is necessary to further reduce the amount of oxygen to the order of ppb, an adsorption column filled with an adsorbent for adsorbing oxygen may be provided in the subsequent stage of the deoxygenation tower, or a getter may be used. It is possible to further reduce the amount of oxygen by disposing a reaction tube filled with OH and treating the high-purity argon derived from the deoxygenation column with these adsorption tubes or reaction tubes. In this case, the amount of oxygen in the high-purity argon discharged from the deoxygenation tower may be several ppm instead of 1 ppm or less. This is because if the oxygen content is in this range, it is possible to sufficiently deoxidize with an adsorbent or a getter, not with a deoxidizing method by a catalytic reaction by continuously adding hydrogen.

For example, FIG. 2 shows the height obtained as described above.
System diagram showing an example of an apparatus for further purifying pure argon
In addition, the high-purity material derived from the deoxidation tower 64 to the pipe 78
Liquefied argon is introduced into the reaction tube 81,
Oxygen in the trace amount is removed, and
It is intended to be highly purified.

High purity led to the pipe 78 from the deoxygenation tower 64
Liquefied argon is supplied to the pressurizing cylinder 82 by its own liquid head.
It is pressurized to about 1.6 ata and introduced into the vaporizer 83,
84 heat exchange with a warm fluid such as nitrogen gas introduced from 84
Turn into. The high-purity argon gas vaporized by the vaporizer 83 is
Ultra-high-purity argon discharged from the reaction tube 81 in the heat exchanger 85
Heat exchange with the gas to raise the temperature, and then react with the heater 86
It is heated to the processing temperature of the cylinder 81, for example, 150 to 350 ° C.
After that, it is introduced into the reaction tube 81.

The reaction tube 81 includes a getter made of copper or nickel.
With high purity introduced into the reaction tube 81.
Trace oxygen in argon gas is, for example, about 1 to 10 ppm
Degree to 0.2 ppm, or ppb depending on conditions
The order is removed. Instead of the reaction tube 81,
Molecular Sieves MS4A, MS5A or Carbon
Adsorption cylinder filled with adsorbent such as recurring sieves
However, it is also possible to remove oxygen by adsorption.

Ultra high purity with oxygen components removed in the reaction tube 81
The argon gas is passed through the pipe 87 to the heat exchanger 85.
After heat exchange with the high-purity argon gas to lower the temperature, liquefaction
The liquid is introduced into the liquefier 88 that uses nitrogen or the like as a cold source.
Turned into ultra-high-purity liquefied argon and collected from tube 89.
Be done.

In this embodiment, the vaporizer 83 is used to
Liquefy argon with a liquefier 88 and a warm fluid that vaporizes argon
Nitrogen is used as the cold fluid. That is, vaporization
It is led to the vessel 83 from a circulating nitrogen system or the like via a pipe 84.
In addition, medium-pressure nitrogen gas has been introduced, and the liquid is vaporized in the vaporizer 83.
Liquefied nitrogen that is liquefied by vaporizing argon chloride
Is expanded from the lower column of the double rectification column after expansion with the valve 91.
Liquefied by merging with the liquefied nitrogen that was led to
Is introduced into the container 88. Liquefaction of argon with this vaporizer 88
The nitrogen gas vaporized by
And part of it is returned to the circulating nitrogen system via pipe 95,
Is the nitrogen gas discharged from the pipe 96 through the valve 97 to the upper tower.
To join.

It should be noted that the high-purity exhaust derived from the deoxidation tower 64 is
When the rugong is a gas, the vaporizer 83 and the liquefier 88 are used.
It is not necessary to provide a tube, and it is sufficient to pass the reaction tube 81 and the like.
It is sufficient to raise the pressure to a sufficient pressure and raise it to the required temperature.
Also, when using an adsorption cylinder, this temperature raising operation is also omitted.
It is possible to use a pump or blower for boosting operation.
Can be used.

[0034]

As described above, according to the method and apparatus for separating high-purity argon of the present invention, nitrogen is separated in the first stage and oxygen is separated in the second stage. The operating pressure of the oxygen tower can be set to a low pressure suitable for separating argon and oxygen in the rectification operation, and the amount of oxygen in argon can be efficiently separated and removed only by the rectification operation. The amount of oxygen in high-purity argon is 1
It can be kept below ppm. Further, since hydrogen gas is not used, not only the safety is improved, but also the equipment can be simplified, and the equipment cost and the operation cost can be reduced. In particular, since the pressure loss can be reduced by forming the deoxygenation column as a packed column, it becomes possible to separate and remove oxygen more efficiently.

[Brief description of drawings]

FIG. 1 is a system diagram of a high-purity argon separator according to an embodiment of the present invention.

FIG. 2 An example of an apparatus for further refining high-purity argon
FIG.

FIG. 3 shows an example of a conventional high-purity argon sampling device.
It is a system diagram.

FIG. 4 also shows a conventional high-purity argon sampling device.
It is a system diagram.

[Explanation of symbols]

1 ... Double rectification column, 3 ... Crude argon column, 4, 60, 67 ... Condenser, 52 ... Liquid column pressurizer, 55 ... Denitrification column, 57, 71
… Reboiler, 64… Deoxidizer, 81… Reactor

Claims (2)

(57) [Claims] 1. A method for separating high-purity argon by air liquefaction separation for compressing, purifying and cooling air, liquefying and rectifying in a double rectification column to collect oxygen and nitrogen, and collecting high-purity argon. Argon-containing gas derived from the double rectification column is introduced into a crude argon column for rectification to obtain crude argon containing a small amount of nitrogen and oxygen, and then the crude argon is introduced into a denitrification column for rectification. , After nitrogen is separated from the top of the tower, the denitrification crude argon derived from the bottom of the denitrification tower is introduced into the deoxygenation column for rectification, and oxygen is separated and extracted from the bottom of the tower, and high purity is obtained from the top of the tower. A method for separating high-purity argon, which comprises collecting argon. 2. A double rectification column for liquefying and rectifying compressed, purified and cooled air into oxygen and nitrogen, and rectifying an argon-containing gas derived from the middle part of the upper column of the double rectification column. A crude argon column to obtain crude argon containing small amounts of nitrogen and oxygen;
A denitrification tower for rectifying the crude argon derived from the top of the crude argon tower to separate and derive nitrogen from the tower top, and a tower for rectifying the denitrification crude argon derived from the bottom of the denitrification tower. An apparatus for separating high-purity argon, comprising: a deoxygenation tower for separating and discharging oxygen from the bottom and collecting high-purity argon from the tower top.