TWI474969B - Inert gas purification method - Google Patents

Description

Inert gas purification method

The present invention relates to an inert gas refining method for reusing an inert gas used in oxidation resistance or nitriding resistance.

The present application claims priority based on Japanese Patent Application No. 2011-188788, filed on Jan.

In a heating furnace for heating ceramics or metals, an inert gas such as nitrogen or argon is used for the purpose of oxidation resistance or nitriding resistance. Since the amount of the inert gas used at this time is extremely large, it is preferable to re-use the inert gas by purifying the gas after use.

Patent Document 1 discloses an argon gas purification method and an argon gas purification device for purifying argon gas as an inert gas. In this method, oxygen is added to an argon gas containing a reducing gas such as carbon monoxide or hydrogen to carry out a three-stage catalytic reaction, whereby oxidation of each reducing gas is performed.

Specifically, in Patent Document 1, it is disclosed that oxygen is added to argon gas containing carbon monoxide or hydrogen in the first catalytic column to oxidize carbon monoxide, and then oxygen is added to the second and third catalytic columns to oxidize And removing the reaction product formed in the catalytic towers in the adsorption column in the latter stage Carbon dioxide and moisture.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-180067

However, in the argon gas purification method described in Patent Document 1, since the entire amount of carbon monoxide and hydrogen is oxidized by oxygen in the catalyst column, it is necessary to prepare an extremely large amount of oxygen and a catalyst to increase the cost.

In other words, in the argon gas purification method described in Patent Document 1, there is a problem that the inert gas cannot be efficiently purified.

Accordingly, it is an object of the present invention to provide an inert gas purification method which can efficiently purify an inert gas.

In order to solve the above problems, the present invention provides the following methods.

The present invention relates to a method for purifying an inert gas, which is an inert gas purification method for purifying an inert gas containing hydrogen and carbon monoxide, which comprises the steps of: adding oxygen to the inert gas, and making hydrogen into water by using a catalyst. And a second step of removing the carbon monoxide, the water, and the carbon dioxide generated by the oxidation of the carbon monoxide in the first step by the adsorbent after the first step.

(1) That is, the first aspect of the present invention is an inert gas purification method for purifying an inert gas for purifying an inert gas containing hydrogen and carbon monoxide. The method comprising: a first step of adding oxygen to the inert gas and making hydrogen into water by a reaction using a catalyst; and removing the inert gas from the inert gas by an adsorbent after the first step The second step of the carbon monoxide and the water.

(2) The method of the present invention described above, preferably, in the first step, the temperature of the catalyst is in the range of 135 to 200 °C.

(3) The method of the present invention according to (1) or (2), wherein, in the first step, the concentration of the oxygen added to the inert gas is 1 vol% or less.

(4) The method of the present invention as described in the above (1) to (3), wherein the catalyst is preferably a catalyst having palladium supported on alumina.

(5) The method of the present invention according to (1) to (4) above, wherein the adsorbent is preferably composed of at least one of zeolite, alumina, and activated carbon.

(6) The method of the present invention according to (1) to (5) above, preferably, before the first step, the step of measuring the concentration of hydrogen contained in the inert gas containing hydrogen and carbon monoxide; The amount of oxygen added in the first step is an amount of 1/2 of the hydrogen concentration measured in the previous step.

(7) The method of the present invention according to the above (1) to (3), (5) to (6), preferably, the catalyst is a catalyst in which platinum is held in an alumina support.

(8) The method of the present invention according to (1) to (7) above, preferably, before the first step, the step of measuring the concentration of hydrogen contained in the inert gas containing hydrogen and carbon monoxide; The amount of oxygen added in the first step is in the previous step Measured to a concentration of 1/2 to 1 of the hydrogen concentration, and the concentration of oxygen added to the inert gas is 1 vol% or less; the catalyst is a catalyst for holding palladium in alumina and a catalyst for holding platinum in alumina. Any one of them; preferably, the temperature of the aforementioned catalyst is controlled in the range of 135 to 200 °C. The amount of oxygen added in the above first step is also preferably an amount of 1/2 of the hydrogen concentration measured in the above-mentioned substep.

(9) The method of the present invention according to (1) to (8) above, preferably, the first step is constituted by the following steps (a) to (b): (a): the hydrogen concentration exceeds 2 vol% In the inert gas containing hydrogen and carbon monoxide, 1 vol% or less of oxygen is added to the inert gas, and hydrogen is added to water by a reaction using a catalyst; and (b) is treated by the step (a) In the inert gas containing hydrogen and carbon monoxide having a hydrogen concentration of 2 vol% or less, oxygen is added in an amount of 1 vol% or less with respect to the inert gas, and hydrogen is brought into water by a reaction using a catalyst.

(10) The method of the present invention according to (1) to (9) above, preferably, in the second step, the carbon dioxide generated by the oxidation of the carbon monoxide in the first step is removed.

Further, according to the above method of the present invention, preferably, the inert gas is argon.

According to the present invention, there is provided a first step of adding oxygen to an inert gas and making hydrogen into water by a reaction using a catalyst; and in the first step After the second step, the second step of removing carbon monoxide, water, and carbon dioxide necessary from the inert gas by the adsorbent, thereby selectively making the hydroxide which is a poorly adsorbable component into an easily adsorbable component, and then The carbon monoxide and water which are easily adsorbed can be easily adsorbed and removed. Thereby, the purification of the inert gas can be performed more efficiently than the conventional inert gas purification method.

10, 30‧‧‧ inert gas refining device

11‧‧‧buffer tank

13‧‧‧ Catalyst Tower

14‧‧‧1st gas transfer pipeline

15‧‧‧Hydrogen concentration analyzer

16‧‧‧Oxygen supply pipeline

18‧‧‧ heat exchanger

21‧‧‧2nd gas transfer pipeline

23‧‧‧Adsorption and Separation Department

24‧‧‧ gas discharge line

Fig. 1 is a view showing a schematic configuration of an inert gas purifying apparatus according to an embodiment of the present invention.

Fig. 2 is a view showing a schematic configuration of an inert gas purifying apparatus according to a modification of the embodiment of the present invention.

Fig. 3 is a graph showing the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column when the temperature of the catalyst was changed in the range of 50 to 280 °C in the experiment 1-1 of the example.

Fig. 4 is a graph showing the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column when the temperature of the catalyst was changed in the range of 50 to 280 °C in the first experiment of the examples.

Fig. 5 is a graph showing the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column when the temperature of the catalyst was changed in the range of 30 to 280 °C in the second experiment of the example.

Fig. 6 is a graph showing the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column when the temperature of the catalyst was changed in the range of 30 to 400 °C in the third experiment of the example.

Figure 7 is shown in the fourth experiment of the examples, at 30 to 280 ° C A graph showing the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column when the temperature of the catalyst is changed within the range.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these examples. When there is no special mention, the quantity, position, material, etc. may be selected or added or omitted as necessary.

(embodiment)

Fig. 1 is a view showing a schematic configuration of an inert gas purifying apparatus according to an embodiment of the present invention.

Referring to Fig. 1, the inert gas purification apparatus 10 of the present embodiment includes a buffer tank 11, a catalyst tower 13, a first gas delivery line 14, a hydrogen concentration analyzer 15, an oxygen supply line 16, and a heat exchanger 18, 2 gas transfer line 21, adsorption separation unit 23, and gas discharge line 24.

The buffer tank 11 is a material gas for storing an inert gas containing carbon monoxide and hydrogen (more specifically, an exhaust gas from a heating furnace (not shown) such as molten ceramic or metal) (hereinafter referred to as "raw material gas A"). The slot. The buffer tank 11 is connected to the first gas transfer line 14. The material gas is not particularly limited as long as it is an inert gas containing carbon monoxide and hydrogen. For example, the material gas A is preferably substantially only a gas composed of carbon monoxide, hydrogen, and argon. It may also be a gas composed only of carbon monoxide, hydrogen, and at least one inert gas. Further, the material gas A is preferably also a gas containing no carbon dioxide.

The catalytic tower 13 is connected to the buffer tank 11 via the first gas delivery line 14. The catalytic tower 13 is disposed in the first gas delivery line 14 first. The portion after the primary heat exchanger 18. The catalytic tower 13 is connected to one end of the second gas delivery line 21.

In the catalytic column 13, the raw material gas A to which oxygen is added is transported by the first gas transfer line 14. In the catalyst column 13, the hydrogen contained in the source gas A is reacted (catalyzed) with the added oxygen to form water.

The material gas A after the catalytic reaction is first cooled to about room temperature (for example, 25 ° C), and then introduced into the adsorption separation unit 23.

The catalyst used in the catalyst column 13 can be used arbitrarily as long as it is a catalyst capable of oxidizing. Specifically, as the catalyst, for example, a support of at least one of platinum, palladium, rhodium, and iridium is supported by a support such as alumina, ruthenium dioxide, or aluminum ruthenate. It is particularly preferred to use alumina and palladium.

In addition, the catalyst for hydration can generally be oxidized by carbon monoxide. Therefore, it is preferable to control the temperature of the catalyst column 13 from the viewpoint of suppressing oxidation of carbon monoxide in order to efficiently perform oxidation of hydrogen. The temperature can be chosen as necessary. In order to prevent the oxidation of hydrogen from being suppressed from carbon monoxide to carbon dioxide, the conditions are different, but it is preferably set to 200 ° C or lower. When oxygen is added at a high concentration, for example, when 1.5 to 2.5 vol% of oxygen is added, since the temperature rise is likely to occur, the upper limit can be made 300 ° C or lower, but it is preferable to take measures against temperature. Further, from the viewpoint of promoting oxidation of hydrogen, the temperature is preferably 70 ° C or higher, and particularly preferably 135 ° C or higher. Therefore, it is particularly preferable to set it in the range of 135 to 200 °C. The temperature of the catalytic layer can be confirmed by a thermometer such as a thermocouple. The temperature control can be performed by a heater controlled by a temperature regulator or the like. The aforementioned temperature is particularly preferably in the range of 160 to 200 °C. The catalytic tower 13 can be a catalytic tower 13 loaded with a heater and a thermometer.

The hydrogen concentration analyzer 15 measures the concentration of hydrogen contained in the material gas A flowing through the portion between the buffer tank 11 and the oxygen supply line 16 in the first gas delivery line 14. The hydrogen concentration analyzer 15 can transmit the result of measuring the concentration of hydrogen contained in the material gas A to the oxygen supply line 16 by any means selected.

The oxygen supply line 16 is a branch line branched from a portion of the first gas transfer line 14 located between the analysis position of the hydrogen concentration analyzer 15 and the heat exchanger 18. The oxygen supply line 16 is a line for adding oxygen to the material gas A transported by the first gas transfer line 14.

The oxygen supply line 16 is made of oxygen, and is preferably added to the material gas A by oxygen in an amount of 1/2 of the hydrogen concentration contained in the material gas A measured by the hydrogen concentration analyzer 15. By this ratio, the reaction can be efficiently carried out. For example, when the hydrogen concentration in the material gas A is 2%, the amount of oxygen added can be set to 1%.

Further, the amount of oxygen added to the material gas A may be changed to be other than the above ratio as necessary. It may also be added in a slight excess with respect to hydrogen. For example, the amount of oxygen may be, for example, 0.5 to 1.2 times the volume of the hydrogen contained in the material gas A, preferably 0.5 to 1 times the volume, more preferably 0.5 to 0.55 times the volume.

The amount of oxygen added to the material gas A is preferably set to be higher than the material gas A from the viewpoint of suppressing the temperature rise of the catalyst column 13. 1 vol% or less. The lower limit of oxygen is not particularly set, but in order to carry out hydrogen oxidation, it is necessary to set it to be larger than 0 vol% in the present invention.

Fig. 2 is a view showing a schematic configuration of an inert gas purifying apparatus according to a modification of the embodiment of the present invention. In the second drawing, the same components as those of the inert gas refining device 10 shown in Fig. 1 are denoted by the same reference numerals.

In Fig. 2, the adsorption separation unit 23 is composed of two adsorption grooves. It is possible to use both adsorption tanks at the same time, or to use only one side at a time, to replace the used tanks, and to continuously perform adsorption separation. In the present invention, the number of the adsorption tanks is not particularly limited, and may be any one as long as it is one or more.

In the above, it has been described that the amount of oxygen added to the material gas A is preferably 1 vol% or less. However, when the hydrogen concentration in the material gas A exceeds 2 vol%, if the amount of oxygen added is 1 vol% or less with respect to the material gas A in order to suppress the temperature rise, hydrogen remains in the treatment of the material gas A. In the gas.

Therefore, when it is assumed that the hydrogen concentration in the material gas A is increased, two or more catalytic tanks can be used. For example, as shown in Fig. 2, a plurality of catalytic towers 13, a first gas delivery line 14, a hydrogen concentration analyzer 15, and an oxygen supply are provided in series between the buffer tank 11 and the adsorption separation unit 23. The inert gas purifying device 30 of the unit (two in the second drawing) constituted by the line 16, the heat exchanger 18, and the second gas transfer line 21 is added to the raw material gas A introduced into each of the catalytic columns 13. The amount of oxygen added is set to 1 vol% or less.

The heat exchanger 18 is disposed at the first stage of the front stage of the catalytic tower 13 The gas transfer line 14 and the second gas transfer line 21 located at the rear of the catalytic tower 13.

Thus, by providing the heat exchanger 18 in the first gas delivery line 14 located in the front stage of the catalytic tower 13 and the second gas delivery line 21 located in the subsequent stage of the catalytic tower 13, the thermal efficiency in the catalytic treatment step can be improved.

The adsorption separation unit 23 is connected to the other end of the branch of the second gas delivery line 21, and the other end is connected to the gas discharge line 24. The second gas delivery line 21 is a raw material gas A which is discharged from the catalytic tower 13 through the heat exchanger 18 and whose temperature is cooled to about room temperature (for example, 25 ° C) (a gas which is almost completely removed from the raw material gas A) It is sent to the adsorption separation unit 23.

In the adsorption separation unit 23, one of the oxidized carbon contained in the source gas A and the water generated in the catalyst column 13 are removed by the adsorbent. Thereby, the purified inert gas can be taken out from the outlet side of the adsorption separation unit 23 via the gas discharge line 24. The amount of carbon monoxide and hydrogen in the purified inert gas is significantly reduced as compared with the raw material gas A before the treatment.

The adsorbent used in the adsorptive separation unit 23 is not particularly limited, and an adsorbent capable of adsorbing carbon monoxide and water can be used.

In the catalytic column 13, carbon dioxide may be generated due to oxidation of a part of carbon monoxide. Therefore, the adsorbent used in the adsorptive separation unit 23 is preferably an adsorbent which adsorbs carbon monoxide and water and also adsorbs a small amount of carbon dioxide.

As such an adsorbent, for example, at least one of zeolite, alumina, and activated carbon can be used. Can be used with more than 2 materials The applicator is constructed as a laminated structure. It is most suitable to constitute one of the combinations of adsorbents as a laminated structure, for example, those in which alumina and zeolite are sequentially laminated.

The inert gas purification method according to the present embodiment includes: a first step of adding oxygen to an inert gas containing hydrogen and carbon monoxide, and causing hydrogen to become water by a catalytic reaction; and, after the first step, by an adsorbent The second step of removing carbon monoxide, water, and carbon dioxide from the inert gas from the inert gas. Thereby, water which is easily adsorbed by hydrogenation of the hardly adsorbable component can be selectively selected, and then carbon monoxide and water which are easily adsorbed components can be easily adsorbed and removed.

Thereby, the purification of the inert gas can be performed more efficiently than the conventional inert gas purification method.

The inert gas to be treated in the method of the present invention is not particularly limited, and may be selected from general inert gases such as argon, nitrogen, helium, neon, xenon, and the like. The amount of hydrogen and carbon monoxide contained in the inert gas purified by the method of the present invention may be arbitrarily set. The amount of hydrogen is preferably from 0.01% to 10%, particularly preferably from 0.1% to 10%, more preferably from 0.1% to 4%, particularly preferably from 0.1% to 1%. The amount of carbon monoxide is preferably from 1% to 50%, particularly preferably from 1% to 20%, more preferably from 1% to 10%, particularly preferably from 1% to 5%.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific embodiments. Various modifications and changes can be made without departing from the spirit and scope of the invention.

(Example)

The following is a description of the excellent effects under the preferred conditions (temperature conditions of the catalyst) of the first step of the process of the present invention. The following examples illustrate the invention A preferred example, but the invention is not limited thereto.

In the evaluation, the same inert gas refining device as that shown in Fig. 1 was used.

"The 1-1st experiment"

(Evaluation of catalyst reaction temperature (1))

First, argon gas containing carbon monoxide (5 vol%), hydrogen (0.1 vol%), and oxygen (0.1 vol%) was prepared at 7.0 L/min.

This mixed gas was introduced into a catalyst column 13 (see Fig. 1) filled with a catalyst (42 cc) (ND-101 manufactured by N.E. Chemcat Co., Ltd.) in which palladium was supported on alumina.

An experiment of changing the temperature of the catalyst in the range of 50 to 280 ° C was then carried out. Specifically, catalytic treatment was carried out for 60 minutes at each of the set temperatures and evaluated. At this time, the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column 13 were evaluated. Hereinafter, this experiment is referred to as "the 1-1st experiment."

The result is shown in Figure 3. Fig. 3 is a graph showing the results of measuring the concentrations of hydrogen and carbon monoxide contained in the material gas discharged from the catalyst column when the temperature of the catalyst was changed within the range of 50 to 280 °C. (The concentration of hydrogen and carbon monoxide used in this evaluation is not shown in Figure 1).

Referring to Fig. 3, it was confirmed that when the temperature of the catalyst exceeds 50 °C, the oxidation of hydrogen gradually starts. When the temperature of the catalyst is 135 to 200 °C, hydrogen is preferentially oxidized to have a hydrogen concentration of 0.01 vol%.

In addition, it can be known that when the temperature of the catalyst exceeds 200 ° C, the reverse of hydrogen The rate of reduction is reduced, and the oxidation of carbon monoxide is more preferential than the oxidation of hydrogen.

"The 1-2th experiment"

Further, an experiment in which the same conditions as the above experiment were carried out was carried out except that a platinum (NM-101 manufactured by N.E. Chemcat Co., Ltd.) was used as a catalyst on alumina. At the same time, as shown in Fig. 4, the result of preferential oxidation of hydrogen at 135 to 200 ° C was obtained.

That is, it was confirmed that the temperature of the catalyst can be set in the range of 135 to 200 °C.

"Second experiment"

(Evaluation of catalyst reaction temperature (2))

The same experiment was carried out except that the concentration of hydrogen contained in the inert gas and the amount of oxygen corresponding thereto were changed as compared with the first experiment of the first to 1-1.

First, argon gas containing carbon monoxide (5 vol%), hydrogen (1 vol%), and oxygen (1 vol%) was prepared at 7.0 L/min. This mixed gas was introduced into a catalyst column 13 (see Fig. 1) filled with a catalyst (42 cc) supporting palladium on alumina. Then, the temperature of the catalyst was changed in the range of 25 to 280 ° C, and the concentration of hydrogen contained in the material gas discharged from the catalyst column 13 at this time was evaluated. Hereinafter, this experiment is referred to as a "second experiment."

At this time, when the temperature of the catalyst exceeds 100 ° C, the reaction of hydrogen and oxygen starts, and the temperature rises rapidly to around 200 ° C due to the heat of reaction. At this time, that is, the concentration of hydrogen contained in the inert gas on the outlet side of the catalyst column when the temperature of the catalyst was 200 ° C was 0.0 vol%, and the concentration of carbon monoxide was 4.0 vol% (refer to Fig. 5).

It can be seen that under this condition, all of the hydrogen contained in the inert gas is oxidized, and a part of the carbon monoxide is also reacted.

"3rd experiment"

(Evaluation of catalyst reaction temperature (3))

The experiment was carried out under the same conditions as in the second experiment except that argon gas containing carbon monoxide (5 vol%), hydrogen (4 vol%), and oxygen (2 vol%) was used.

At this time, when the temperature of the catalyst exceeded 60 ° C, the temperature of the catalyst rapidly reached 300 ° C due to the heat of reaction, and then reached 400 ° C. Further, the concentration of hydrogen on the outlet side of the catalyst column 13 at a temperature of the catalyst of 300 ° C was 3.5 vol%, and the concentration of carbon monoxide was 1.5 vol% (refer to Fig. 6). This experiment is referred to as "the third experiment."

Compared with the second experiment, it was confirmed that more carbon monoxide reacted to become carbon dioxide, and the reaction of hydrogen was suppressed.

"The 4th Experiment"

(Evaluation of catalyst reaction temperature (4))

The experiment was carried out under the same conditions as in the second experiment except that argon gas containing carbon monoxide (5 vol%), hydrogen (1 vol%), and oxygen (0.5 vol%) was used. This experiment is referred to as "the fourth experiment." The result of preferential oxidation of hydrogen below 200 ° C can be obtained. The result is shown in Figure 7.

(Industry use possibility)

The present invention can provide an inert gas purification method capable of more efficiently purifying an inert gas than the conventional inert gas purification method. The invention is applicable to the inertness used to resist oxidation or nitridation An inert gas purification method in which a gas is reused.

10‧‧‧Inert gas refining device

11‧‧‧buffer tank

13‧‧‧ Catalyst Tower

14‧‧‧1st gas transfer pipeline

15‧‧‧Hydrogen concentration analyzer

16‧‧‧Oxygen supply pipeline

18‧‧‧ heat exchanger

21‧‧‧2nd gas transfer pipeline

23‧‧‧Adsorption and Separation Department

24‧‧‧ gas discharge line

Claims (11)

An inert gas purification method for purifying an inert gas containing an inert gas containing hydrogen and carbon monoxide, characterized by comprising: adding oxygen having a volume of 0.5 to 1.2 times the volume of hydrogen contained in the inert gas to the foregoing An inert gas containing hydrogen and carbon monoxide, and a first step of oxidizing hydrogen to carbon monoxide prior to the use of a catalyst having a temperature in the range of 135 to 200 ° C; and after the first step, by adsorption And a second step of removing the carbon monoxide and the water from the inert gas. The method for purifying an inert gas according to the first aspect of the invention, wherein, in the first step, the concentration of the oxygen added to the inert gas is 1 vol% or less. The method for purifying an inert gas according to claim 1, wherein the catalyst is a catalyst in which palladium is supported in alumina. The method for purifying an inert gas according to claim 1, wherein the adsorbent is composed of at least one of zeolite, alumina, and activated carbon. The method for purifying an inert gas according to claim 1, wherein before the first step, the step of measuring the concentration of hydrogen contained in the inert gas containing hydrogen and carbon monoxide; and adding in the first step The amount of oxygen is an amount of 1/2 of the hydrogen concentration measured in the aforementioned substep. An inert gas refining method as described in claim 1, wherein In the above, the catalyst is a catalyst in which platinum is held in an alumina support. The method for purifying an inert gas according to claim 1, wherein before the first step, the step of measuring the concentration of hydrogen contained in the inert gas containing hydrogen and carbon monoxide; and adding in the first step The amount of oxygen is 1/2 to 1 of the hydrogen concentration measured in the foregoing substep, and the concentration of oxygen added to the inert gas is 1 vol% or less; the catalyst is palladium held in alumina support The catalyst and any one of the catalysts holding platinum in the alumina support; the temperature of the aforementioned catalyst is controlled in the range of 135 to 200 °C. The inert gas purifying method according to claim 1, wherein in the second step, the carbon dioxide generated by the oxidation of the carbon monoxide in the first step is removed. The method for purifying an inert gas according to claim 1, wherein the inert gas is argon. An inert gas purification method for purifying an inert gas containing hydrogen and carbon monoxide comprises: adding oxygen to an inert gas containing hydrogen and carbon monoxide, and reacting by using a catalyst having a temperature in the range of 135 to 200 ° C, a first step of oxidizing hydrogen to carbon monoxide in preference to water; and a second step of removing said carbon monoxide and said water from said inert gas by said adsorbent after said first step The first step is composed of the following steps (a) and (b): (a): in an inert gas containing hydrogen and carbon monoxide having a hydrogen concentration of more than 2% by volume, 1 vol% or less is added to the inert gas. a step of causing hydrogen to become water by a reaction using a catalyst; and (b): in a hydrogen gas containing hydrogen and carbon monoxide having a hydrogen concentration of 2 vol% or less after being treated by the step (a), Oxygen is added so that the inert gas is 1 vol% or less, and hydrogen is brought into water by a reaction using a catalyst. The inert gas purifying method according to claim 10, wherein the amount of oxygen added in the first step is an amount of 1/2 of the hydrogen concentration measured in the second step.