JPH0312315A - Method for refining inert gas - Google Patents

Abstract

PURPOSE:To reduce the amt. of hydrogen in refined gas by absorbing a trace amt. of oxygen with a catalyst in the refining process of inert gas and at the same time regenerating the catalyst by using regenerated gas. CONSTITUTION:A catalyst tower is packed with copper or nickel catalyst, through which inert gas containing a trace amt. of oxygen is passed. In this process, the source inert gas is brought into contact with the catalyst at higher temp. than room temp., to remove the oxygen by absorption, and thus the inert gas is refined. At the same time, a part of the refined gas, or a part of the refined gas and a part of the source inert gas is used as the regenerated gas. This regenerated gas is mixed with hydrogen prior to the regeneration process and used to regenerate the catalyst at high temp. In the post process of regeneration the regenerated gas is used to purge hydrogen remaining in the catalyst.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for purifying an inert gas, and more specifically, a method for purifying an inert gas such as nitrogen by removing trace amounts of oxygen gas contained therein. Regarding.

[Conventional technology]

In general, a method for obtaining dry purified gas by removing trace amounts of oxygen contained in an inert gas such as nitrogen is to bring the inert gas into contact with a copper and/or nickel-based catalyst. A method in which an element and oxygen are reacted and absorbed and removed, or a method in which hydrogen is mixed with an inert gas and brought into contact with a palladium-based catalyst, the hydrogen and oxygen are reacted to form moisture, and this moisture is removed using a dryer. is used.

In the method of removing trace oxygen from inert gas using the steel and/or nickel-based catalyst described above, a two-column switching type catalyst tower filled with the above catalyst is usually used, and the raw material inert gas is transferred to one side. Hydrogen is introduced into the catalyst tower and brought into contact with the catalyst at room temperature or high temperature to remove trace amounts of oxygen, while hydrogen is introduced into the other catalyst tower and brought into contact with the catalyst at high temperature, and the oxygen absorbed by the catalyst is converted into moisture using hydrogen. The catalyst is regenerated by converting it.

[Problem to be solved by the invention]

In such conventional methods, using copper and/or nickel-based catalysts for room-temperature purification and high-temperature regeneration, a large amount of energy is required to raise and lower the temperature of the catalyst tower between purification and regeneration. There is a problem.

In addition, in the method of high-temperature refining and high-temperature regeneration using copper and/or nickel-based catalysts, the energy required for heating can be reduced by installing a heat exchanger and recovering heat. There is a problem in that some of the hydrogen is absorbed into the catalyst and remains, which is mixed into the purified gas.

On the other hand, in the method using palladium-based catalysts, more than the theoretical amount of hydrogen is mixed with the raw material inert gas, so there are problems with hydrogen remaining in the purified gas and the need for a dryer to remove the generated moisture. There is a problem that the device becomes complicated. Furthermore, when using a palladium-based catalyst, a copper and/or nickel-based catalyst is installed after the palladium-based catalyst in order to remove residual hydrogen from the purified gas, and oxygen is used to regenerate the catalyst. There is a method in which the hydrogen contained in the gas reacts with the oxygen absorbed by a copper and/or nickel-based catalyst to form moisture, and this is removed using a dryer, but this method has the problem of making the equipment more complicated. be.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inert gas purification method that can efficiently remove trace amounts of oxygen and residual hydrogen in an inert gas and easily obtain dry purified gas.

[Means to solve the problem]

In order to achieve the above 17 objects, the inert gas purification method of the present invention includes, as a first configuration, an inert gas containing a trace amount of oxygen in a catalyst column filled with a copper and/or nickel catalyst. In the inert gas purification method in which the trace amount of oxygen is absorbed by the catalyst and removed through the catalyst, purified gas is obtained in a purification step in which the raw material inert gas is brought into contact with the catalyst at a temperature higher than room temperature, and the catalyst column is In the regeneration process, a part of the purified gas or a part of the purified gas and a part of the raw material inert gas are used as regeneration gas, and in the first stage of the regeneration process, hydrogen is mixed into the regeneration gas and heated at high temperature. The catalyst is brought into contact with the catalyst to regenerate it, and in the latter stage of the regeneration step, the regeneration gas is used to purge hydrogen remaining in the catalyst column, moisture, and hydrogen absorbed in the catalyst.

Further, a second configuration of the present invention is, in the above-mentioned first configuration,
A part of the purified gas is used in the catalyst regeneration step and the purge step as the gas used in the catalyst tower regeneration step.

In the third configuration, in the first configuration, a part of the raw material inert gas is used in the catalyst regeneration step and the purge step before the catalyst regeneration step and the purification process is performed after the purge step as the gas used in the catalyst column regeneration step. It is characterized by the use of a portion of gas.

A fourth configuration is that in the first configuration, as a gas used in the regeneration process of the catalyst column, a part of the purified gas is supplied after the catalyst regeneration step and the purge step, and a part of the purified gas is inactivated before the purge step. It is characterized by the use of a portion of gas.

In a fifth configuration, in the first configuration, the amount of oxygen absorbed by the catalyst or the amount of oxygen absorbed by the catalyst is determined by measuring the flow rate of the raw material inert gas and the oxygen concentration in the raw material inert gas. The present invention is characterized in that the amount of oxygen in the regeneration gas in the catalyst regeneration step is calculated, and the amount of hydrogen mixed into the regeneration gas is controlled based on the amount of oxygen.

Further, in a sixth configuration, in the first configuration, the purge step during the regeneration step temporarily raises the temperature of the catalyst column by 30 to 100°C higher than the temperature during purification. It is characterized in that the temperature is then lowered to the purification temperature and purging is performed.

[For production]

As in the first configuration above, a part of the purified gas or a part of the purified gas and a part of the raw material inert gas are switched to regenerate the catalyst as regenerated gas, and this regenerated gas is used to regenerate the catalyst tower after regeneration. By purging residual hydrogen, moisture, and hydrogen absorbed into the catalyst, the amount of hydrogen mixed into the purified gas can be reduced.

In the second configuration, the entire regeneration process is performed using part of the purified gas, which simplifies the operation.

In the third configuration, since most of the regeneration process is performed using the raw material inert gas, the regeneration efficiency is high and the load on the catalyst is light.

Furthermore, in the fourth configuration, a part of the raw material inert gas containing a trace amount of oxygen is used as a purge gas before the purge step, so that the hydrogen released from the catalyst combines with oxygen, so that these hydrogens are returned to the catalyst. can be prevented from being absorbed. Furthermore, since a portion of the purified gas is used in the subsequent stage of the purge step, moisture can also be reliably purged.

Furthermore, as in the fifth configuration, by calculating the amount of oxygen absorbed by the catalyst and controlling the amount of hydrogen mixed into the regeneration gas, the catalyst can be regenerated reliably and the amount of residual hydrogen can be reduced. be able to.

In the sixth configuration, since the temperature of the catalyst tower is temporarily raised during the purge step, the release of hydrogen absorbed in the catalyst is promoted and hydrogen purge can be performed more reliably.

Therefore, it is possible to reduce the amount of hydrogen and moisture mixed into the purified gas that has been purified by contacting with the catalyst, and it is possible to obtain high-quality inert gas.

〔Example〕

Next, the present invention will be explained based on the illustrated system diagram.

The figure shows an example of a purification apparatus to which the method of the present invention is applied, and a case will be described in which purification is performed by introducing a raw material inert gas containing 100 ppm of oxygen at a flow rate of 2ONrr+'/h. In addition, the catalyst tower 3a to be used selectively
, 3b will be explained assuming that one catalyst tower 3a is in the purification process and the other catalyst tower 3b is in the regeneration process.

The raw material inert gas G passes through the raw material gas supply pipe 1 and is heated by the heater 2 to a refining temperature, for example, 200-300° C., and then passes through the valve 21a and is introduced into the catalyst column 3a to be used in a switched manner. Each catalyst column 3a, 3b is filled with a copper- and/or nickel-based catalyst, and trace amounts of oxygen in the raw material inert gas are absorbed by the catalyst metal and removed to 1 ppi or less. Purified gas F is supplied from purified gas supply pipe 4 through valve 22a.

The catalyst towers 3a and 3b are, for example, of a 12-hour switching type, and when the raw material inert gas G is flowing into one catalyst tower 3a for purification, the other catalyst tower 3b is used for the regeneration process. will be held. This catalyst tower regeneration process is performed in four steps: a pressure reduction step, a catalyst regeneration step, a purge step, and a pressurization step.

In the step of reducing the pressure of the catalyst tower 3b after the purification process, the valves 21b and 22b are closed, the valve 23b is opened, and the pressure inside the catalyst tower 3b is reduced to atmospheric pressure through the regeneration gas discharge pipe 5.

Next, in the catalyst regeneration step, the valves 24 and 25b are opened, and a portion of the purified gas F being led out from the catalyst cylinder 3a to the purified gas supply pipe 4, I Nrr? /h is taken out as regeneration gas R through the regeneration gas supply pipe 6a, and 0.01 hydrogen H is taken out from the hydrogen gas supply pipe 7 with the valve 26 opened.
6 Nrr? /h, further heated to a predetermined regeneration temperature with a heater 8, and introduced into the catalyst column 3b. Hydrogen H reacts with oxygen absorbed by the catalyst to produce moisture, and the regenerated gas together with the moisture and unreacted hydrogen II is discharged from the regenerated gas exhaust pipe 5 through the valve 23b. .

Further, a flow meter 9 and an oxygen meter 10 are installed in the raw material gas supply pipe 1, and a memory/calculator 11 is used to control the catalyst tower 3a.
, calculate the amount of oxygen flowing into 3b.

Adjust the regulator 1 so that the amount of hydrogen added is memorized and required for regeneration.
2 and a control valve 13 to adjust the amount of hydrogen. For example, if only the purified gas F is used as the purge gas, the flow rate of the raw material inert gas G introduced into the catalyst towers 3a and 3b in the purification process is 2O
Nrrl'/h, and assuming that the oxygen concentration is constant at 1001) pll, the amount of oxygen absorbed by the catalyst is: 20 Nrn'/h xlooppm X12t+-
〇. 024Nrri'. The amount of hydrogen required in the catalyst regeneration step to convert this oxygen to water is: 0.024 Nrrl'X2XK-o, 048Nry
l'XK (where K in the formula is a constant of 1 or more).

Furthermore, in order to add this amount of hydrogen in 3 hours of regeneration time, K
-1, 0, 048 Nrri'÷3h -0,016Nrr
? /h.

Therefore, as mentioned above, the hydrogen flow rate is 0.016 Nrr
By adjusting the opening degree of the control valve 13 so that the opening rate is 1'/h, it is possible to supply sufficient hydrogen to convert oxygen into water, thereby avoiding inconveniences due to the addition of excessive hydrogen and damage to the catalyst. Problems such as insufficient reproduction can be prevented. still,
Generally, the above constant should be set greater than 1 to ensure regeneration of the catalyst by incorporating slightly more hydrogen.

In the purge step after performing the above catalyst regeneration step over a period of 3 hours, the valve 26 is closed to stop the introduction of hydrogen H, and the water and hydrogen remaining in the catalyst column 3b are removed from the regeneration gas RINnf/ Purge with h.

At this time, the heating temperature of the heater 8 is set to 30 to 30°C higher than the refining temperature.
By heating the catalyst tower 3b to a high temperature by increasing the temperature by 100° C., hydrogen absorbed in the catalyst can be easily released.

After heating for a sufficient time to release the hydrogen absorbed by the catalyst, in this case 3 hours, the heating temperature of the heater 8 is returned to the same temperature as the catalyst column 3b during the original purification. , the purging is continued while lowering the temperature of the catalyst tower 3b.

In order to further improve the regeneration efficiency, the valve 27 is opened and a part of the raw material inert gas G is supplied as the regeneration gas R from the regeneration gas supply pipe 6b to the catalyst tower instead of the purified gas F at the pre-stage of this purge step. 3b. Thereby, the hydrogen released from the catalyst combines with the oxygen in the raw material inert gas G, so that it is possible to prevent these hydrogens from being absorbed into the catalyst again. After finishing the purification with the raw material inert gas G, the valve 27 is closed, the valve 24 is opened, and a portion of the purified gas F is supplied from the regeneration gas supply pipe 6a in the same manner as described above.
Nrr'r/h is introduced as regeneration gas R, and the catalyst tower 3
Purge b. Further, by using the raw material inert gas from the beginning of the regeneration process, that is, from the catalyst regeneration step to the stage before the purge step, the regeneration efficiency is improved and the operation is simplified.

After the purge step is completed, the valve 23b is closed and a pressurization step is performed, and the catalyst tower 3b is pressurized with regeneration gas R (purified gas F) until the pressure in the catalyst tower 3b reaches the pressure at the time of purification.

The above operations are performed on the catalyst towers 3a, 3b and each valve 21a to 27.
By switching and repeating the steps, dry inert gas containing 1 ppm or less of oxygen and 1 ppm or less of hydrogen can be continuously obtained. Also, during the regeneration process, the valves 23a, 25
a is in a closed state.

Note that the method of the present invention is not limited to the systems shown in the above examples,
It is possible to apply the present invention to a purification apparatus that is appropriately configured depending on the type of inert gas, throughput, etc.

〔Effect of the invention〕

As is clear from the above explanation, in the inert gas purification method of the present invention, a portion of the purified gas or a portion of the purified gas is removed after the contained trace oxygen is absorbed by a steel and/or nickel catalyst. A part of the raw material inert gas is switched to a part of the raw material inert gas to be used as regeneration gas, and this regeneration gas is used to regenerate the catalyst, and the hydrogen and moisture remaining in the catalyst column after catalyst regeneration are absorbed into the catalyst. purge the hydrogen that has been
The amount of hydrogen, etc. mixed into purified gas can be reduced.

In addition, by calculating the amount of oxygen absorbed by the catalyst and controlling the amount of hydrogen mixed into the regeneration gas, it is possible to supply enough hydrogen to regenerate the catalyst, ensuring catalyst regeneration. It is possible to reduce the amount of hydrogen remaining in the catalyst column.

Furthermore, by temporarily increasing the temperature of the catalyst tower during the purge step, the release of hydrogen absorbed in the catalyst can be promoted, and hydrogen can be purged more reliably.

In addition, by using a raw material inert gas containing trace amounts of oxygen as a purge gas before the purge step, the hydrogen released from the catalyst is combined with oxygen, preventing these hydrogen from being absorbed into the catalyst again. can. Furthermore, since a portion of the purified gas is used in the latter stage of the purge step, the generated moisture can also be reliably purged.

Therefore, according to the present invention, it is possible to reduce the amount of hydrogen and moisture mixed into the purified gas that is purified by contacting the raw material inert gas containing a trace amount of oxygen with a catalyst, and dry the hydrogen and oxygen to below the allowable concentrations. Purified gas can be obtained stably and continuously.

[Brief explanation of the drawing]

The figure is a system diagram of a purification apparatus to which the present invention is applied. 1... Raw material gas supply pipe 3a, 3b... Catalyst tower 4
... Purified gas supply pipe 5 ... Regeneration gas discharge pipe 6a
, 6b... Regeneration gas supply pipe 7... Hydrogen gas supply pipe 9... Flow meter 10... Oxygen meter 11.
...Memory/calculator 12...Adjuster 13...
Control valve G: Raw material inert gas F: Purified gas
R...Regeneration gas

Claims (1)

[Claims] 1. Purification of an inert gas by passing an inert gas containing a trace amount of oxygen through a catalyst column filled with a copper and/or nickel catalyst, and removing the trace oxygen by absorbing the trace oxygen into the catalyst. In the method, a purified gas is obtained in a purification step in which a raw material inert gas is brought into contact with a catalyst at a temperature higher than room temperature, and a regeneration step of the catalyst column includes a part of the purified gas or a part of the purified gas and the raw material. In the first stage of the regeneration process, hydrogen is mixed into the regeneration gas and brought into contact with the catalyst at high temperature to regenerate the catalyst, and in the second stage of the regeneration process, the regeneration gas is A method for purifying an inert gas, characterized in that hydrogen remaining in a catalyst column, moisture, and hydrogen absorbed in a catalyst are purged using a catalyst column. 2. The inert gas purification method according to claim 1, wherein a part of the purified gas is used in the catalyst regeneration step and the purge step as the gas used in the catalyst column regeneration step. Gas purification method. 3. In the inert gas purification method according to claim 1, as the gas used in the regeneration step of the catalyst column, a part of the raw material inert gas is used before the catalyst regeneration step and the purge step, and a part of the raw material inert gas is used after the purge step. A method for purifying an inert gas, characterized in that a part of the purified gas is used. 4. In the inert gas purification method according to claim 1, as the gas used in the regeneration step of the catalyst column, a part of the purified gas is added after the catalyst regeneration step and the purge step, and a part of the purified gas is added to the raw material before the purge step. A method for purifying an inert gas, characterized by using a part of the inert gas. 5. In the inert gas purification method according to claim 1, the flow rate of the raw material inert gas and the oxygen concentration in the raw material inert gas are measured to determine the amount of oxygen absorbed by the catalyst or the amount of oxygen absorbed by the catalyst. A method for purifying an inert gas, comprising calculating the amount of oxygen and the amount of oxygen in the regeneration gas in the catalyst regeneration step, and controlling the amount of hydrogen mixed into the regeneration gas based on the amount of oxygen. 6. In the inert gas purification method according to claim 1, the purging step during the regeneration step is performed by temporarily raising the temperature of the catalyst column by 30 to 100°C higher than the temperature during purification. A method for purifying an inert gas, the method comprising: then lowering the temperature to the purification temperature and purging.