JP2013155091A - Method and apparatus for purifying argon gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an impurity content of argon gas in a pretreatment stage of an adsorption treatment; to reduce energy necessary for purification; and to purify the argon gas so as to be highly pure.SOLUTION: When purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil and nitrogen, a part of hydrocarbons and oil are adsorbed by active carbon. Then, when the amount of oxygen in the argon gas is smaller than a set amount of oxygen necessary for reactions with all of hydrogen, carbon monoxide and hydrocarbons, oxygen is added so as to exceed the set amount, and the reactions are generated by using a rhodium catalyst. Thereafter, carbon monoxide is added to the argon gas so as to exceed a set amount necessary for a reaction with all oxygen remaining in the reaction, and the reaction is generated by using ruthenium, rhodium or a mixed catalyst thereof. Subsequently, carbon monoxide, carbon dioxide, water and nitrogen in the argon gas are adsorbed onto an adsorbent by a pressure swing adsorption method.

Description

  The present invention relates to a method and apparatus for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil and nitrogen as impurities.

  For example, in equipment such as silicon single crystal pulling furnace, ceramic sintering furnace, vacuum degassing equipment for steel making, silicon plasma melting equipment for solar cells, polycrystalline silicon casting furnace, argon gas is used as atmosphere gas in the furnace Has been. The purity of argon gas collected for reuse from such facilities is reduced due to the incorporation of hydrogen, carbon monoxide, air, and the like. Therefore, in order to increase the purity of the recovered argon gas, the admixed impurities are adsorbed on the adsorbent. Furthermore, in order to efficiently adsorb such impurities, it has been proposed to react oxygen in the impurities and combustible components to denature them into carbon dioxide and water as a pretreatment of the adsorption treatment (Patent Document 1). 2).

  In the method disclosed in Patent Document 1, first, the amount of oxygen in the argon gas is adjusted to be slightly less than the stoichiometric amount necessary for complete combustion of combustible components such as hydrogen and carbon monoxide. doing. Next, using palladium or gold, which gives priority to the reaction between hydrogen and oxygen over the reaction between carbon monoxide and oxygen, oxygen in argon gas is reacted with carbon monoxide, hydrogen, etc. Carbon dioxide and water are produced in the state where only the residue remains. Next, carbon dioxide and water contained in argon gas are adsorbed on the adsorbent at room temperature, and then carbon monoxide and nitrogen contained in argon gas are made into the adsorbent at a temperature of −10 ° C. to −50 ° C. Adsorbed.

  In the method disclosed in Patent Document 2, the amount of oxygen in the argon gas is set to an amount sufficient to completely combust combustible components such as hydrogen and carbon monoxide, and then argon is used using a palladium-based catalyst. By reacting oxygen in the gas with carbon monoxide, hydrogen, or the like, carbon dioxide and water are generated with oxygen remaining. Next, carbon dioxide and water contained in the argon gas are adsorbed on the adsorbent at room temperature, and then oxygen and nitrogen contained in the argon gas are adsorbed on the adsorbent at a temperature of about −170 ° C.

  In the method disclosed in Patent Document 3, when the oil content is contained in the argon gas discharged from the single crystal production furnace or the like, the oil content is removed using an oil removal cylinder or an oil removal filter containing activated carbon or the like. ing. Next, oxygen in the argon gas introduced into the catalyst cylinder is reacted with added hydrogen to be converted into water. Next, water and carbon dioxide in the argon gas introduced into the adsorption cylinder are adsorbed and removed, and then purified by a rectification operation.

  In the method disclosed in Patent Document 4, in order to purify an argon gas containing carbon monoxide, hydrogen, oxygen, and nitrogen as impurities, carbon monoxide and hydrogen in the argon gas are reacted with oxygen to obtain carbon monoxide. Carbon dioxide and water are produced in a state where the water remains. Next, carbon dioxide, water, nitrogen and carbon monoxide in argon gas are adsorbed on the adsorbent at 10 to 50 ° C., and the adsorbent is regenerated at 150 to 400 ° C. Moreover, in order to adsorb | suck nitrogen in argon gas, the copper ion exchange ZSM-5 type zeolite (copper ion exchange rate 121%) is used as an adsorbent.

Japanese Patent No. 3496079 Japanese Patent No. 3737900 JP 2000-88455 A JP 2006-111506 A

  In the method described in Patent Document 1, carbon dioxide and water are generated in a state where carbon monoxide remains in the argon gas in the first stage reaction of the pretreatment. However, when there are many hydrocarbons contained in argon gas, since it is necessary to raise reaction temperature, carbon monoxide also reacts with oxygen and it is difficult to leave carbon monoxide. For this reason, hydrogen cannot be adsorbed and removed by the subsequent adsorption treatment at room temperature, so that hydrogen remains in the argon gas and the argon gas cannot be purified to a high purity.

  In the method described in Patent Document 2, oxygen is retained by setting the amount of oxygen contained as an impurity in the argon gas as an impurity in the pretreatment stage to a sufficient amount to completely burn hydrogen, carbon monoxide, and the like. It produces carbon dioxide and water. However, after that, in order to adsorb the remaining oxygen, it is necessary to lower the temperature at the time of adsorption to about -170 ° C. That is, since oxygen remains in the pretreatment stage of the adsorption treatment, there is a problem that the cooling energy during the adsorption treatment increases and the purification load increases.

  In the method described in Patent Document 3, oil contained in argon gas is removed by adsorbing it on activated carbon. However, when recovering the argon gas, for example, when using a device such as an oil rotary vacuum pump that uses oil to maintain airtightness, a hydrocarbon component in which the oil is thermally decomposed is generated. Such a hydrocarbon component passes through the mist separator even if there is a mist separator for oil removal. Then, the hydrocarbon derived from the oil contained in the argon gas has several hundreds of methane in terms of tens of ppm or more and hydrocarbons having 2 to 6 carbon atoms (C2 to C6) in terms of hydrocarbons having 1 carbon atom (C1). It becomes very high at ppm or more. Methane is not adsorbed on the activated carbon, and hydrocarbons having 2 to 6 carbon atoms pass through the catalyst cylinder almost without being adsorbed on the activated carbon, resulting in an increase in subsequent rectification load.

  Patent Document 4 does not disclose any removal of oil contained in argon gas and hydrocarbons by-produced by decomposition of the oil.

  An object of the present invention is to provide an argon gas refining method and a refining apparatus that can solve the above-described problems of the prior art.

The method of the present invention is a method for purifying an argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbon, oil and nitrogen as impurities, wherein a part of the hydrocarbon and the oil in the argon gas are converted into activated carbon. Adsorb and then determine whether the amount of oxygen in the argon gas exceeds a set amount necessary to react with all of hydrogen, carbon monoxide, and hydrocarbons in the argon gas; When the amount of oxygen in the gas is less than or equal to the set amount, oxygen is added so as to exceed the set amount, and then carbon monoxide, hydrogen, and hydrocarbon and oxygen in the argon gas are converted into the first reaction catalyst. The reaction with rhodium produces carbon dioxide and water with oxygen remaining, and the amount of carbon monoxide in the argon gas is Carbon monoxide is added so as to exceed the set amount necessary to react with all of the remaining oxygen, and then oxygen and carbon monoxide in the argon gas are used as ruthenium as a second reaction catalyst, Reaction with rhodium or a mixture thereof produces carbon dioxide with carbon monoxide remaining, and then at least carbon monoxide, carbon dioxide, water, and nitrogen in the argon gas. It is made to adsorb | suck to an adsorbent by the pressure swing adsorption method.
According to the present invention, the oil contained in the argon gas is adsorbed by the activated carbon, and some of the hydrocarbons derived from the oil are also adsorbed by the activated carbon. Particularly, hydrocarbons other than those having 1 to 6 carbon atoms are adsorbed by the activated carbon. Adsorbed effectively. Thereby, the amount of water and carbon dioxide produced | generated by reaction of hydrocarbon and oxygen in a post process can be reduced by reducing the amount of hydrocarbons in argon gas, and a subsequent adsorption load can be reduced.
In addition, hydrogen, carbon monoxide, and hydrocarbon in argon gas are reacted with oxygen using rhodium as the first reaction catalyst, so that carbon dioxide and water are generated in a state where excess oxygen remains. Is done. Since rhodium used as the first reaction catalyst has high heat resistance and high reactivity, when the argon gas contains a large amount of lower hydrocarbons such as methane, the reaction temperature is raised and the reaction is sufficiently advanced. The hydrocarbons in can be effectively reduced.
The residual oxygen and the newly added carbon monoxide are reacted using ruthenium, rhodium, or a mixture thereof as a second reaction catalyst, so that carbon dioxide is generated in a state where carbon monoxide remains. Is done. Thereby, oxygen in the argon gas is removed. By using ruthenium, rhodium, or a mixture thereof as the second reaction catalyst, the reaction between water and carbon monoxide can be suppressed to suppress hydrogen generation. Accordingly, hydrogen that cannot be removed by the adsorption treatment can be prevented from remaining in the argon gas at the pretreatment stage of the adsorption treatment by the pressure swing adsorption method, so that the argon gas can be purified with high purity. Furthermore, since oxygen can be removed from the argon gas at the pretreatment stage of the adsorption treatment by the pressure swing adsorption method, the purification load can be reduced and impurities can be effectively removed.

The apparatus of the present invention is an apparatus for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil and nitrogen as impurities, the activated carbon adsorption tower into which the argon gas is introduced, and the activated carbon adsorption A first reactor into which argon gas flowing out from the tower is introduced, an oxygen supply device capable of adding oxygen to the argon gas introduced into the first reactor, and argon gas flowing out from the first reactor are introduced Second reactor, carbon monoxide supplier capable of adding carbon monoxide to the argon gas introduced into the second reactor, and adsorption device into which the argon gas flowing out from the second reactor is introduced The activated carbon adsorption tower contains activated carbon that adsorbs a part of hydrocarbons and oil in the argon gas, and the first reactor contains carbon monoxide in the argon gas. As a first reaction catalyst for reacting hydrogen, hydrocarbons, and oxygen, rhodium is contained, and as the second reaction catalyst for reacting oxygen and carbon monoxide in the argon gas in the second reactor. , Ruthenium, rhodium, or a mixture thereof, wherein the adsorption device has a PSA unit that adsorbs at least carbon monoxide, carbon dioxide, water, and nitrogen in the argon gas by a pressure swing adsorption method. To do.
According to the apparatus of the present invention, the method of the present invention can be carried out.

In the method of the present invention, between the reaction using the first reaction catalyst and the reaction using the second reaction catalyst, the moisture content in the argon gas is reduced by a dehydration process using a dehydrator. It is preferable to do so.
Thereby, in addition to being able to suppress hydrogen generation by using ruthenium, rhodium, or a mixture thereof as the second reaction catalyst, hydrogen generation can be prevented more reliably. That is, by reducing the moisture content in the argon gas using a dehydrator before the reaction using the second reaction catalyst, the absolute value of the moisture content is lowered, and thus the absolute value of the moisture content changes. Since the change in the effective reaction temperature is suppressed, the reaction temperature can be controlled more reliably. Furthermore, by reducing the amount of moisture in the argon gas, the reaction of carbon monoxide and water, which is a load on the catalyst, is suppressed, and the load on the catalyst is reduced, so that the catalyst can act stably. Therefore, even if the concentration of oxygen, carbon monoxide, and water in the argon gas fluctuates due to load fluctuations, it is possible to reliably respond to suppress the reaction of carbon monoxide and water, and reliably prevent hydrogen generation can do. As the dehydrator, for example, one having two towers filled with activated alumina as a dehydrating agent is used, and the activated alumina in the other tower is regenerated while the dehydration treatment is performed with the activated alumina in one tower.
In this case, in the apparatus of the present invention, a dehydrator for reducing the moisture content in the argon gas flowing out from the first reactor is provided between the first reactor and the second reactor. preferable. As the dehydrator, a refrigerator or a column filled with a dehumidifying agent can be used.

In the present invention, it is preferable to use activated alumina and X-type zeolite as the adsorbent used for the pressure swing adsorption method.
By using activated alumina as the adsorbent, moisture and carbon dioxide can be adsorbed and desorbed, so that the adsorption effect of carbon monoxide, nitrogen and hydrocarbons by the X-type zeolite can be enhanced. That is, carbon dioxide is relatively difficult to desorb from the X-type zeolite and reduces the adsorption effect of the X-type zeolite. If the X-type zeolite charged in the PSA unit is increased in order to enhance the adsorption effect, there is a problem that the capacity of the pressurizing compressor and the like has to be increased, resulting in an increase in the size of the PSA unit and a decrease in efficiency. On the other hand, the adsorption effect of X-type zeolite can be enhanced by adsorbing carbon dioxide with activated alumina. Thereby, even if hydrocarbons remain in the argon gas in the stage before the adsorption process by the adsorption device, the hydrocarbons can be effectively adsorbed to the adsorbent by the pressure swing adsorption method without increasing the size of the PSA unit.
Moreover, since the adsorption effect of carbon monoxide and nitrogen by the pressure swing adsorption method can be enhanced, nitrogen in the argon gas is adsorbed by the thermal swing adsorption method at −10 ° C. to −50 ° C. after the adsorption by the pressure swing adsorption method. Argon gas can be purified with low energy and high purity without being adsorbed by the agent.
In this case, when the weight ratio of activated alumina to X-type zeolite is reduced, the adsorption breakthrough time of nitrogen and hydrocarbon is shortened, and when it is increased, the adsorption breakthrough time is lengthened. Preferably, the activated alumina and the X-type zeolite are arranged in layers, and the weight ratio of the activated alumina and the X-type zeolite is 5/95 to 30/70. Thereby, the hydrocarbon in the argon gas can be effectively adsorbed to the adsorbent by the pressure swing adsorption method. The activated alumina is preferably used for dehumidification and has a specific surface area of 270 m ² / g or more. As the X-type zeolite, for example, Li-X type and Ca-X type can be used, and the Li-X type is particularly preferable.

In the method of the present invention, after the adsorption by the pressure swing adsorption method, nitrogen in the argon gas is preferably adsorbed on the adsorbent by a thermal swing adsorption method at −10 ° C. to −50 ° C.
The nitrogen concentration in the argon gas can be reduced only by adsorption using the pressure swing adsorption method, but by using the adsorption by the thermal swing adsorption method, the load on the PSA unit for performing the pressure swing adsorption method can be reduced and purified. Responding to the fluctuation of the impurity concentration in the previous argon gas, impurities can be removed reliably. Thereby, the purity of the argon gas after purification can be further increased. In addition, oxygen can be removed from the argon gas at the pretreatment stage of the adsorption treatment by the thermal swing adsorption method, and carbon monoxide can be removed by the pressure swing adsorption method, thereby reducing the cooling energy during the adsorption treatment by the thermal swing adsorption method. it can. In addition, hydrocarbons can be removed from the argon gas in the pretreatment stage of the thermal swing adsorption method, so it is necessary to desorb other than nitrogen during regeneration of the adsorbent used for the thermal swing adsorption method. There is no, and regenerative energy can be reduced.
In this case, it is preferable that the adsorption device in the apparatus of the present invention has a TSA unit that adsorbs nitrogen in the argon gas flowing out from the PSA unit by a thermal swing adsorption method at −10 ° C. to −50 ° C.

  According to the present invention, by reducing the impurity content of argon gas at the pretreatment stage of the adsorption treatment, the load of the adsorption treatment is reduced, the energy required for purification is reduced, and the recovered argon gas is purified to a high purity. Furthermore, it is possible to provide a practical method and apparatus that can effectively cope with the case where the argon gas contains hydrocarbon and oil.

Arrangement explanatory drawing of the purification apparatus of argon gas concerning the embodiment of the present invention Structure explanatory drawing of the PSA unit in the purification apparatus of argon gas concerning the embodiment of the present invention Structure explanatory drawing of the TSA unit in the refiner | purifier of the argon gas which concerns on embodiment of this invention

  1 purifies spent argon gas supplied from an argon gas supply source 1 such as a single crystal silicon or polycrystalline silicon casting furnace so that it can be recovered and reused. . The purifier α includes a filter 2, an activated carbon adsorption tower 3, a heater 4, a reaction device 5 having a first reactor 5 a and a second reactor 5 b, a dehydration device 6 having switching valves 6 a to 6 c, an adsorption device 7, an oxygen A supply device 8, a carbon monoxide supply device 9, a cooler C, and a product tank T are provided.

  The trace amount of impurities contained in the argon gas before purification is at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil and nitrogen, but may contain other impurities such as carbon dioxide and water. . The concentration of impurities in the argon gas before purification is not particularly limited, and is, for example, about 5 mol ppm to 80000 mol ppm.

  Argon gas supplied from the supply source 1 is collected by, for example, an oil rotary vacuum pump (not shown), and after being removed by a filter 2 (for example, AF1000P manufactured by CKD), is first introduced into the activated carbon adsorption tower 3. Activated carbon that adsorbs part of hydrocarbons and oil in argon gas is accommodated in the activated carbon adsorption tower 3.

  The amount of oxygen in the argon gas after some of the hydrocarbons and oil are adsorbed on the activated carbon exceeds the set amount of oxygen required to react with all of the hydrogen, carbon monoxide, and hydrocarbons in the argon gas. It is determined whether or not. In this embodiment, the set amount of oxygen is the stoichiometric amount of oxygen necessary to react with all of hydrogen, carbon monoxide, and hydrocarbon in the argon gas.

Depending on the type of hydrocarbon contained in the argon gas, the amount of oxygen required to completely burn the hydrocarbon varies. Therefore, it is preferable to make the above determination after previously obtaining the composition and concentration of impurities contained in the argon gas through experiments. For example, when the hydrocarbon contained in the argon gas is methane, the reaction formula when hydrogen, carbon monoxide, and methane in the argon gas react with oxygen to produce water and carbon dioxide is as follows: .
H ₂ +1/2 O ₂ → H ₂ O
CO + 1/2 O ₂ → CO ₂
CH ₄ + 2O ₂ → CO ₂ + 2H ₂ O
In this case, the oxygen concentration in the argon gas depends on whether the oxygen molar concentration in the argon gas exceeds a value equal to the sum of 1/2 the hydrogen molar concentration, 1/2 the carbon monoxide molar concentration and twice the methane molar concentration. What is necessary is just to determine whether the quantity exceeds the said stoichiometric quantity. Of course, the hydrocarbon contained in the argon gas is not limited to methane, and two or more kinds of hydrocarbons may be contained.

  The set amount of oxygen does not have to be the stoichiometric amount, and may be more than the stoichiometric amount. For example, the value is preferably 1.05 to 2.0 times the stoichiometric amount, and 1.05 times or more ensures that the oxygen in the argon gas is hydrogen, carbon monoxide, and hydrocarbon. The oxygen concentration can be prevented from becoming unnecessarily high by setting it to 2.0 times or less.

  When the oxygen amount in the argon gas is equal to or less than the set amount, oxygen is added to the argon gas by the oxygen supplier 8 so as to exceed the set amount. When the amount of oxygen in the argon gas exceeds the set amount, it is not necessary to add oxygen. That is, the purifier α directly purifies the argon gas when the oxygen amount in the argon gas exceeds the set amount, and exceeds the set amount when the oxygen amount is equal to or less than the set amount. Purify the argon gas after the oxygen is added. By providing the oxygen supply device 8 capable of adding oxygen to the argon gas introduced into the first reactor 5a, when the oxygen amount in the argon gas is equal to or less than the set amount, the argon gas is set to exceed the set amount. Oxygen can be added.

  The oxygen supply device 8 can be constituted by a device capable of adding oxygen at a flow rate corresponding to the flow rate of argon gas introduced into the first reactor 5a, such as a high-pressure oxygen container having a flow control valve. Before the oxygen supply, a sampling line for sampling the argon gas introduced into the first reactor 5a is provided, and an oxygen analyzer (for example, DE-150ε manufactured by GE Sensing & Inspection Technologies) is provided in the sampling line. A hydrogen analysis gas chromatography (for example, GC-PDD manufactured by GLscience), a carbon monoxide analyzer (for example, ZRE manufactured by Fuji Electric Systems) and a total hydrocarbon analyzer (for example, FIA-510 manufactured by Horiba), and It is preferable to provide an oxygen analyzer and a carbon monoxide analyzer in an argon gas sampling line before being introduced into the second reactor 5b. Thus, by monitoring the impurity composition in the argon gas continuously, a slight excess of oxygen can be added more reliably.

  Argon gas flowing out from the activated carbon adsorption tower 3 is introduced into the first reactor 5 a via the heater 4. The heating temperature of the argon gas by the heater 4 is preferably 200 ° C. or higher in order to complete the reaction in the first reactor 5a, and preferably 400 ° C. or lower from the viewpoint of preventing the catalyst life from being shortened. .

  The first reactor is configured such that carbon monoxide, hydrogen, and hydrocarbons in the argon gas react with oxygen in the first reactor 5a so that carbon dioxide and water are generated in a state where oxygen remains. Rhodium (Rh) is accommodated in 5a as the first reaction catalyst. When the argon gas contains a large amount of lower hydrocarbons such as methane, the reaction temperature is preferably set to 300 ° C. or higher so that the reaction proceeds sufficiently. Therefore, it is preferable to use a catalyst in which rhodium having good heat resistance and high reactivity is supported on alumina. Palladium or the like can be used as a catalyst for reacting carbon monoxide, hydrogen, and hydrocarbon with oxygen, but rhodium is more heat-resistant than palladium and palladium is an example of a heat-resistant temperature under these conditions. Is 500 ° C to 600 ° C, platinum (Pt) is 500 ° C to 600 ° C, ruthenium (Ru) is about 350 ° C to 400 ° C, while rhodium is about 700 ° C to 800 ° C. Excellent durability. By using such a rhodium catalyst, hydrocarbons in the argon gas can be effectively reduced in the first reactor 5a.

  The dehydrator 6 is provided between the first reactor 5a and the second reactor 5b, and can reduce the moisture content in the argon gas flowing out from the first reactor 5a. In the present embodiment, the argon gas flowing out from the first reactor 5a is introduced into the second reactor 5b via the dehydrator 6 or directly. That is, the pipe connecting the first reactor 5a and the dehydrator 6 is opened and closed by the switching valve 6a, and the pipe connecting the first reactor 5a and the second reactor 5b is opened and closed by the switch valve 6b. The pipe connecting the second reactor 5b is opened and closed by the switching valve 6c. Argon gas flowing out of the first reactor 5a is introduced into the second reactor 5b through the dehydrator 6 by opening the switching valves 6a and 6c and closing the switching valve 6b, and switching by switching the switching valves 6a and 6c. It is directly introduced into the second reactor 5b by opening the valve 6b. Thereby, when it is not necessary to introduce the argon gas flowing out from the first reactor 5a into the dehydrator 6, the argon gas flowing out from the first reactor 5a can be directly introduced into the second reactor 5b. It is said that.

  The configuration of the dehydrator 6 is not limited as long as the moisture content in the argon gas can be reduced by dehydration between the reaction using the first reaction catalyst and the reaction using the second reaction catalyst described later. . For example, a pressurized dehydration device that pressurizes argon gas and adsorbs moisture in the argon gas with an adsorbent and regenerates the adsorbent under reduced pressure. Removes condensed moisture by pressurizing and cooling the argon gas. As the dehydrating apparatus 6, a refrigeration-type dehydrating apparatus, a heat-regenerating dehydrating apparatus that removes moisture contained in argon gas with a dehydrating agent, and heats the dehydrating agent to regenerate can be used.

  Carbon monoxide is added by the carbon monoxide supplier 9 to the argon gas that flows out from the dehydrator 6 or the first reactor 5a and is introduced into the second reactor 5b. The added carbon monoxide is introduced into the second reactor 5b together with argon gas. By the addition of carbon monoxide, the amount of carbon monoxide in the argon gas introduced into the second reactor 5b exceeds the set amount necessary for reacting with all of the residual oxygen in the argon gas. In this embodiment, the set amount of carbon monoxide is the stoichiometric amount of carbon monoxide necessary to react with all of the oxygen in the argon gas. In this case, the carbon monoxide molar concentration in the argon gas exceeds twice the oxygen molar concentration measured at the outlet of the first reactor 5a, so that the carbon monoxide amount in the argon gas exceeds the stoichiometric amount.

  The set amount of the carbon monoxide does not need to be the stoichiometric amount, and may be more than the stoichiometric amount. For example, the value is preferably 1.05 to 2.0 times the stoichiometric amount, and by making the value 1.05 times or more, the carbon monoxide in the argon gas is reliably reacted with the residual oxygen to remain. Oxygen can be consumed, and by making it 2.0 times or less, it is possible to prevent the residual carbon monoxide concentration from becoming higher than necessary.

  The carbon monoxide feeder 9 is configured by a device capable of adding carbon monoxide at a flow rate corresponding to the flow rate of argon gas introduced into the second reactor 5b, such as a high-pressure carbon monoxide container having a flow rate control valve. it can. Before supplying the carbon monoxide, a sampling line for sampling the argon gas introduced into the second reactor 5b is provided, and an oxygen analyzer and a carbon monoxide analyzer are provided in the sampling line. It is preferable to provide a carbon monoxide analyzer in the sampling line of the argon gas before flowing out from the second reactor 5b and being introduced into the adsorption device 7. Thereby, by monitoring the impurity composition in argon gas continuously, a slight excess of carbon monoxide can be added more reliably.

  In the second reactor 5b, oxygen in the argon gas reacts with carbon monoxide, so that carbon dioxide is generated with carbon monoxide remaining in the second reactor 5b. Ruthenium (Ru), rhodium, or a mixture thereof is accommodated as a catalyst. The ruthenium, rhodium, or a mixture thereof is preferably supported on alumina.

  The higher the reaction temperature in the second reactor 5b, the easier it is to generate hydrogen due to the reaction between carbon monoxide and water. On the other hand, the lower the reaction temperature, the more the carbon monoxide becomes the second reaction catalyst. The reaction between oxygen and carbon monoxide is hindered by poisoning phenomena that hinder its function. In addition, it is necessary to increase the amount of carbon monoxide added and promote the reaction between oxygen and carbon monoxide as the residual oxygen concentration in the argon gas introduced into the second reactor 5b increases. On the other hand, as the amount of carbon monoxide added increases, hydrogen is more likely to be generated by the reaction between carbon monoxide and water, and carbon monoxide tends to hinder the function of the second reaction catalyst. Therefore, it is preferable to limit the oxygen concentration, the carbon monoxide concentration, and the reaction temperature of the argon gas in the second reactor 5b to a range in which conditions suitable for purification can be obtained. For example, when the reaction temperature is less than 50 ° C., the reactivity between oxygen and carbon monoxide is reduced, and when it is 130 ° C. or more, hydrogen is easily generated due to the reaction between carbon monoxide and water. Therefore, the reaction temperature is 50 ° C. to 130 ° C., the molar concentration of carbon monoxide is 2.1 to 2.4 times the molar oxygen concentration, or 3000 mol ppm or less, and the molar concentration of oxygen is 1000 mol ppm or less. Is preferred.

  The argon gas flowing out of the second reactor 5b reaches the adsorption device 7 after the moisture is reduced by being cooled by the cooler C. The adsorption device 7 includes a PSA unit 10 and a TSA unit 20.

  The PSA unit 10 adsorbs at least carbon monoxide, carbon dioxide, water, and nitrogen in argon gas to the adsorbent by a pressure swing adsorption method at room temperature. The argon gas cooled by the cooler C is introduced into the PSA unit 10. Thereby, the carbon dioxide and water produced | generated in the 1st reactor 5a, the carbon dioxide produced | generated in the 2nd reactor 5b, and the residual carbon monoxide are PSA with the nitrogen originally contained in argon gas. It is adsorbed by the adsorbent in the unit 10. Further, when hydrocarbons remain in the argon gas introduced into the PSA unit 10, the hydrocarbons can be adsorbed.

As the PSA unit 10, a known unit can be used. For example, the PSA unit 10 shown in FIG. 2 is a four-column type, and includes a compressor 12 that compresses argon gas flowing out from the second reactor 5b, and four first to fourth adsorption towers 13, each adsorption tower. 13 is filled with an adsorbent. The adsorbent is capable of adsorbing carbon monoxide, carbon dioxide, water, and nitrogen. In this embodiment, activated alumina and X-type zeolite are used. As the X-type zeolite, Li-X type and Ca- X-type synthetic zeolite is preferred. The arrangement of the activated alumina and the X-type zeolite in each adsorption tower 13 is not particularly limited. For example, the activated alumina and the X-type zeolite may be alternately arranged in layers. The weight ratio of activated alumina to X-type zeolite is preferably 5/95 to 30/70. When the two layers are alternately arranged, it is preferable to arrange activated alumina upstream of the argon gas flow and arrange X-type zeolite downstream.
The compressor 12 is connected to the inlet 13a of each adsorption tower 13 via the switching valve 13b.
Each of the inlets 13a of the adsorption tower 13 is connected to the atmosphere via a switching valve 13e and a silencer 13f.
Each of the outlets 13k of the adsorption tower 13 is connected to the outflow pipe 13m via the switching valve 13l, connected to the boosting pipe 13o via the switching valve 13n, and connected to the pressure equalization / washing outlet side pipe 13q via the switching valve 13p. Connected to the pressure equalization / cleaning inlet side pipe 13s through the switching valve 13r.
The outflow pipe 13m is connected to the product tank T via the pressure control valve 13t.
The booster pipe 13o is connected to the outflow pipe 13m via the flow rate control valve 13u and the flow rate indicating controller 13v, and the argon gas introduced into the product tank T is adjusted by adjusting the flow rate in the booster pipe 13o to be constant. Flow rate fluctuation is prevented.
The pressure equalizing / cleaning outlet side pipe 13q and the pressure equalizing / cleaning inlet side pipe 13s are connected to each other via a pair of connecting pipes 13w, and a switching valve 13x is provided in each connecting pipe 13w.

In each of the first to fourth adsorption towers 13 of the PSA unit 10, an adsorption process, a reduced pressure I process (cleaning gas outflow process), a reduced pressure II process (equal pressure gas outflow process), a desorption process, and a cleaning process (cleaning gas input process). The step-up I step (equal pressure gas entering step) and the step-up II step are sequentially performed. Each process is demonstrated as follows on the basis of the 1st adsorption tower 13. FIG.
That is, only the switching valve 13b and the switching valve 13l are opened in the first adsorption tower 13, and the argon gas supplied from the second reactor 5b is introduced from the compressor 12 into the first adsorption tower 13 through the switching valve 13b. The As a result, at least nitrogen, carbon monoxide, carbon dioxide and moisture in the argon gas introduced in the first adsorption tower 13 are adsorbed by the adsorbent, thereby reducing the impurity content. Argon gas is sent from the first adsorption tower 13 to the product tank T through the outflow pipe 13m. At this time, a part of the argon gas sent to the outflow pipe 13m is sent to the second adsorption tower 13 through the pressure raising pipe 13o and the flow rate control valve 13u, and the pressure raising II process is performed in the second adsorption tower 13.
Next, the switching valves 13b and 13l of the first adsorption tower 13 are closed, the switching valve 13p is opened, the switching valve 13r of the fourth adsorption tower 13 is opened, and one of the switching valves 13x is opened. As a result, the argon gas having a relatively small impurity content at the upper part of the first adsorption tower 13 is sent to the fourth adsorption tower 13 via the pressure equalization / cleaning inlet side pipe 13s. A process is performed. At this time, in the fourth adsorption tower 13, the switching valve 13e is opened, and a cleaning process is performed.
Next, the switching valve 13e of the fourth adsorption tower 13 is closed while the switching valve 13p of the first adsorption tower 13 and the switching valve 13r of the fourth adsorption tower 13 are open. As a result, the decompression II step is performed in which the fourth adsorption tower 13 recovers the gas until the internal pressures of the first adsorption tower 13 and the fourth adsorption tower 13 become uniform or substantially uniform. At this time, the two switching valves 13x may be opened depending on circumstances.
Next, a desorption process for desorbing impurities from the adsorbent is performed by opening the switching valve 13e of the first adsorption tower 13 and closing the switching valve 13p. The impurities are released into the atmosphere together with the gas through the silencer 13f. The
Next, the switching valve 13r of the first adsorption tower 13 is opened, the switching valves 13b and 13l of the second adsorption tower 13 in the state where the adsorption process is finished are closed, and the switching valve 13p is opened. As a result, the argon gas having a relatively low impurity content in the upper part of the second adsorption tower 13 is sent to the first adsorption tower 13 via the pressure equalization / washing inlet side pipe 13s, and the first adsorption tower 13 performs the washing step. Is done. The gas used in the cleaning process in the first adsorption tower 13 is released into the atmosphere through the switching valve 13e and the silencer 13f. At this time, a reduced pressure I step is performed in the second adsorption tower 13.
Next, the step-up I process is performed by closing the switching valve 13e of the first adsorption tower 13 while the switching valve 13p of the second adsorption tower 13 and the switching valve 13r of the first adsorption tower 13 are opened. At this time, two switching valves 13x may be opened depending on circumstances.
After that, the switching valve 13r of the first adsorption tower 13 is closed. Thereby, it will be in the standby state without a process once. This state continues until the step-up II process of the fourth adsorption tower 13 is completed. When the pressurization of the fourth adsorption tower 13 is completed and the adsorption process is switched from the third adsorption tower 13 to the fourth adsorption tower 13, the switching valve 13n of the first adsorption tower is opened. Thereby, a part of the argon gas sent from the fourth adsorption tower 13 in the adsorption process to the outflow pipe 13m is sent to the first adsorption tower 13 through the pressure raising pipe 13o and the flow rate control valve 13u, so that the first A pressure increasing step is performed in the single adsorption tower 13.
The above steps are sequentially repeated in each of the first to fourth adsorption towers 13 so that argon gas with a reduced impurity content is continuously sent to the product tank T.
The PSA unit 10 is not limited to the one shown in FIG. 2, and the number of towers may be other than 4, for example, 2 or 3, for example.

  Argon gas containing nitrogen that has not been adsorbed by the adsorbent in the PSA unit 10 is introduced into the TSA unit 20. The TSA unit 20 adsorbs nitrogen in the argon gas to the adsorbent by a thermal swing adsorption method at −10 ° C. to −50 ° C.

A known TSA unit 20 can be used. For example, the TSA unit 20 shown in FIG. 3 is a two-column type, and a heat exchange type precooler 21 that precools the argon gas sent from the PSA unit 10 and heat that further cools the argon gas cooled by the precooler 21. The heat exchanger 24 that covers the exchange-type cooler 22, the first and second adsorption towers 23, and the respective adsorption towers 23 is provided. The heat exchanging unit 24 cools the adsorbent with a refrigerant during the adsorption process, and heats the adsorbent with a heat medium during the desorption process. Each adsorption tower 23 has a large number of inner tubes filled with an adsorbent. As the adsorbent, those suitable for adsorption of nitrogen are used. For example, it is preferable to use an X-type zeolite adsorbent ion-exchanged with calcium (Ca) or lithium (Li), and an ion exchange rate of 70%. The specific surface area is particularly preferably 600 m ² / g or more.
The cooler 22 is connected to the inlet 23a of each adsorption tower 23 via a switching valve 23b.
Each of the inlets 23a of the adsorption tower 23 communicates with the atmosphere via the switching valve 23c.
Each of the outlets 23e of the adsorption tower 23 is connected to an outflow pipe 23g through a switching valve 23f, connected to a cooling / pressure-increasing pipe 23i through a switching valve 23h, and connected to a cleaning pipe 23k through a switching valve 23j. Is done.
The outflow pipe 23g constitutes a part of the precooler 21, and the argon gas sent from the PSA unit 10 is cooled by the purified argon gas flowing out from the outflow pipe 23g. The purified argon gas flows out from the outflow pipe 23g through the switching valve 23l.
The cooling / pressurizing piping 23i and the cleaning piping 23k are connected to the outflow piping 23g via a flow meter 23m, a flow control valve 23o, and a switching valve 23n.
The heat exchanging unit 24 is a multi-tube type, and includes an outer tube 24a surrounding a large number of inner tubes constituting the adsorption tower 23, a refrigerant supply source 24b, a refrigerant radiator 24c, a heat medium supply source 24d, and a heat medium radiator 24e. Is done. In addition, the refrigerant supplied from the refrigerant supply source 24b is circulated through the outer pipe 24a and the refrigerant radiator 24c, and the heat medium supplied from the heat medium supply source 24d is supplied to the outer pipe 24a and the heat medium radiator 24e. A plurality of switching valves 24f are provided for switching to a state of circulation through the switching valves 24f. Further, a part of the cooler 22 is constituted by a pipe branched from the refrigerant radiator 24c, and the argon gas is cooled in the cooler 22 by the refrigerant supplied from the refrigerant supply source 24b, and the refrigerant is returned to the tank 24g. .

In each of the first and second adsorption towers 23 of the TSA unit 20, an adsorption process, a desorption process, a cleaning process, a cooling process, and a pressure increasing process are sequentially performed.
That is, in the TSA unit 20, the argon gas supplied from the PSA unit 10 is cooled in the precooler 21 and the cooler 22, and then introduced into the first adsorption tower 23 via the switching valve 23b. At this time, the first adsorption tower 23 is cooled to −10 ° C. to −50 ° C. by circulating the refrigerant in the heat exchanger 24, the switching valves 23c, 23h, and 23j are closed, and the switching valve 23f is opened. In addition, at least nitrogen contained in the argon gas is adsorbed by the adsorbent. As a result, an adsorption step is performed in the first adsorption tower 23, and purified argon gas with reduced impurity content flows out from the adsorption tower 23 through the switching valve 23 l and is sent to the product tank T.
While the adsorption process is performed in the first adsorption tower 23, the desorption process, the cleaning process, the cooling process, and the pressure increasing process are performed in the second adsorption tower 23.
That is, in the second adsorption tower 23, the switching valves 23b and 23f are closed and the switching valve 23c is opened to perform the desorption process after the adsorption process is completed. Thereby, in the 2nd adsorption tower 23, argon gas containing an impurity is discharge | released in air | atmosphere, and a pressure is reduced to substantially atmospheric pressure. In this desorption process, the switching valve 24f of the heat exchanging section 24 that has circulated the refrigerant in the second adsorption tower 23 during the adsorption process is switched to the closed state to stop the circulation of the refrigerant, and the refrigerant is extracted from the heat exchanging section 24. The switching valve 24f that returns to the refrigerant supply source 24b is switched to the open state.
Next, in order to carry out the cleaning process in the second adsorption tower 23, the switching valves 23c, 23j of the second adsorption tower 23 and the switching valve 23n of the cleaning pipe 23k are opened, and the heat in the heat exchange type precooler 21 is heated. Part of the purified argon gas heated by the exchange is introduced into the second adsorption tower 23 through the cleaning pipe 23k. Thus, in the second adsorption tower 23, desorption of impurities from the adsorbent and cleaning with purified argon gas are performed, and the argon gas used for the cleaning is released into the atmosphere together with the impurities from the switching valve 23c. In this cleaning step, the switching valve 24f of the heat exchange unit 24 for circulating the heat medium in the second adsorption tower 23 is switched to the open state.
Next, in order to perform the cooling process in the second adsorption tower 23, the switching valve 23j of the second adsorption tower 23 and the switching valve 23n of the cleaning pipe 23k are closed, and the switching valve 23h of the second adsorption tower 23 The switching valve 23n of the cooling / pressurizing pipe 23i is opened, and a part of the purified argon gas flowing out from the first adsorption tower 23 is introduced into the second adsorption tower 23 through the cooling / pressurizing pipe 23i. As a result, the purified argon gas cooled in the second adsorption tower 23 is released into the atmosphere through the switching valve 23c. In this cooling process, the switching valve 24f for circulating the heat medium is switched to the closed state to stop the circulation of the heat medium, and the switching valve 24f that extracts the heat medium from the heat exchange unit 24 and returns it to the heat medium supply source 24d is provided. Switch to the open state. After completion of the extraction of the heat medium, the switching valve 24f of the heat exchanging unit 24 for circulating the refrigerant in the second adsorption tower 23 is switched to the open state to set the refrigerant circulation state. This refrigerant circulation state continues until the end of the next pressurization step and the subsequent adsorption step.
Next, in order to perform the pressure increasing process in the second adsorption tower 23, the switching valve 23c of the second adsorption tower 23 is closed, and a part of the purified argon gas flowing out from the first adsorption tower 23 is introduced. The inside of the two adsorption tower 23 is pressurized. This pressure increasing process is continued until the internal pressure of the second adsorption tower 23 becomes substantially equal to the internal pressure of the first adsorption tower 23. When the pressure increasing process is completed, the switching valve 23h of the second adsorption tower 23 and the switching valve 23n of the cooling / pressure increasing pipe 23i are closed, whereby all the switching valves 23b, 23c, 23f, 23h of the second adsorption tower 23 are closed. , 23j are closed, and the second adsorption tower 23 is in a standby state until the next adsorption step.
The adsorption process of the second adsorption tower 23 is performed in the same manner as the adsorption process of the first adsorption tower 23. While the adsorption process is performed in the second adsorption tower 23, the desorption process, the washing process, the cooling process, and the pressure increasing process are performed in the first adsorption tower 23 in the same manner as in the second adsorption tower 23.
The TSA unit 20 is not limited to the one shown in FIG. 3, and the number of towers may be 2 or more, for example, 3 or 4.

  According to the purification apparatus α, when the argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil, and nitrogen as impurities is recovered and purified, the oil contained in the argon gas is adsorbed by activated carbon. To do. Furthermore, some of the hydrocarbons derived from the oil can also be adsorbed by activated carbon, and in particular, hydrocarbons other than those having 1 to 6 carbon atoms can be effectively adsorbed by activated carbon. Next, it is determined whether or not the amount of oxygen in the argon gas exceeds the set amount of oxygen necessary to react with all of hydrogen, carbon monoxide, and hydrocarbons in the argon gas, and the amount of oxygen is determined as described above. When the amount is less than the amount, oxygen is added so as to exceed the set amount. Thereafter, carbon monoxide, hydrogen, and hydrocarbon in argon gas are reacted with oxygen using rhodium as the first reaction catalyst, thereby generating carbon dioxide and water in a state where oxygen remains. Thereby, main impurities in the argon gas are carbon dioxide, water, oxygen, and nitrogen. Next, carbon monoxide is added so that the amount of carbon monoxide in the argon gas exceeds the set amount necessary to react with all of the remaining oxygen. Thereafter, oxygen and carbon monoxide in the argon gas are reacted using ruthenium, rhodium, or a mixture thereof as the second reaction catalyst, thereby generating carbon dioxide with carbon monoxide remaining. . Thereby, main impurities in the argon gas are water, carbon monoxide, carbon dioxide, and nitrogen. Thereafter, carbon monoxide, carbon dioxide, water, and nitrogen in the argon gas are adsorbed on the adsorbent by the pressure swing adsorption method and removed from the argon gas.

  That is, the refiner α reduces the amount of hydrocarbons in the argon gas by effectively adsorbing hydrocarbons other than oil and carbon number of 1 to 6 with activated carbon. Thereby, while reducing the quantity of the water and carbon dioxide which are produced | generated by reaction with subsequent hydrocarbon and oxygen, the adsorption | suction load in the latter adsorption | suction apparatus 7 can be reduced. In addition, rhodium used as the first reaction catalyst has high heat resistance and high reactivity. Therefore, when the argon gas contains a large amount of lower hydrocarbons such as methane, the reaction temperature is raised to sufficiently advance the reaction. The hydrocarbon in the argon gas can be effectively reduced. Furthermore, by using ruthenium, rhodium, or a mixture thereof as the second reaction catalyst, the reaction between water and carbon monoxide can be suppressed to prevent hydrogen from being generated. Therefore, it is possible to prevent hydrogen that is difficult to be removed by the adsorption process by the adsorption device 7 from remaining in the argon gas, so that the argon gas can be purified with high purity. In addition, since oxygen can be removed from the argon gas in the pretreatment stage of the adsorption process by the adsorption device 7, the purification load can be reduced and impurities can be effectively removed by the adsorption device 7. Furthermore, by using activated alumina and X-type zeolite as adsorbents used for the pressure swing adsorption method, adsorption and desorption of moisture and carbon dioxide in argon gas are performed with activated alumina, carbon monoxide by X-type zeolite, Nitrogen and hydrocarbon adsorption effect can be enhanced. Thereby, even if hydrocarbons remain in the argon gas in the previous stage of the adsorption process by the adsorption device 7, the hydrocarbons are effectively adsorbed by the adsorbent by the pressure swing adsorption method without increasing the size of the PSA unit 10. be able to.

  Moreover, according to the said refinement | purification apparatus (alpha), between the reaction using the catalyst for 1st reactions, and the reaction using the catalyst for 2nd reactions, the water content rate in argon gas is carried out by the dehydration process using a dehydrator. Can be reduced. Thereby, generation | occurrence | production of hydrogen can be prevented by suppressing reaction of water and carbon monoxide reliably.

  Furthermore, according to the said refinement | purification apparatus (alpha), after adsorption | suction of the impurity by a pressure swing adsorption method, nitrogen in argon gas can be made to adsorb | suck to an adsorbent by the thermal swing adsorption method at -10 degreeC--50 degreeC. Thus, by using the adsorption by the thermal swing adsorption method together, the load on the PSA unit 10 can be reduced, and the impurities can be reliably removed in response to the fluctuation of the impurity concentration in the argon gas before purification. Therefore, the purity of the argon gas after purification can be further increased. In addition, oxygen can be removed from the argon gas at the pretreatment stage of the adsorption treatment by the thermal swing adsorption method, and carbon monoxide can be removed by the pressure swing adsorption method, thereby reducing the cooling energy during the adsorption treatment by the thermal swing adsorption method. it can. In addition, hydrocarbons can be removed from the argon gas in the pretreatment stage of the thermal swing adsorption method, so it is necessary to desorb other than nitrogen during regeneration of the adsorbent used for the thermal swing adsorption method. There is no, and regenerative energy can be reduced. In addition, since the adsorption effect of nitrogen can be enhanced by using activated alumina and X-type zeolite as the adsorbent in the PSA unit 10, the adsorption load of nitrogen in the TSA unit 20 is reduced, and the recovered argon gas is increased. Purified to purity.

Argon gas was purified using the purification apparatus α. Before purification, the argon gas contains 200 molppm of oxygen, 50 molppm of hydrogen, 1000 molppm of carbon monoxide, 750 molppm of nitrogen, 60 molppm of carbon dioxide, 500 molppm of water, and hydrocarbons as impurities. 20 mol ppm of methane, 32 mol ppm of C2-C6 hydrocarbon in terms of C1 hydrocarbon, and 4.5 g / m ^{3 of} oil were contained. This argon gas was introduced into the activated carbon adsorption tower 3 at a flow rate of 4.0 L / min under standard conditions. The activated carbon adsorption tower 3 was made into a pipe shape with a nominal diameter of 32A and filled with 10 L of GX6 / 8 cast charcoal manufactured by Nippon Envirochemicals.
Next, oxygen was added from the oxygen supplier 8 to the argon gas flowing out from the activated carbon adsorption tower 3 at a flow rate of 3.2 ml / min and introduced into the first reactor 5a. In the first reactor 5a, 60 mL of alumina-supported rhodium (NE Chemcat 0.5% alumina pellets) was filled, and the reaction conditions were a temperature of 350 ° C., an atmospheric pressure, and a space velocity of 4000 / h. In this case, oxygen in the argon gas is contained about 1.6 times the theoretical value necessary for reacting with hydrogen, carbon monoxide, and hydrocarbons. Carbon monoxide was added from the carbon monoxide supplier 9 at a flow rate of 3.6 ml / min to the argon gas flowing out from the first reactor 5a and introduced into the second reactor 5b. In this case, carbon monoxide in the argon gas is contained about 1.2 times the theoretical value necessary for consuming residual oxygen. In the second reactor 5b, 60 ml of an alumina-supported ruthenium catalyst (RUA3MM manufactured by Sued Chemie) was charged, and the reaction conditions were a temperature of 110 ° C., an atmospheric pressure, and a space velocity of 4000 / h.
The argon gas flowing out from the second reactor 5 b was cooled, and the impurity content was reduced by the adsorption device 7. The PSA unit 10 is a four-column type, each column is in the shape of a pipe having a nominal diameter of 32 A and a length of 1 m, and 10 wt% of activated alumina (KHD-24 manufactured by Sumitomo Chemical) is used as an adsorbent in each column. 90 wt% of Tosoh NSA-700) was filled. The operating conditions of the PSA unit 10 were an adsorption pressure of 0.8 MPaG, a desorption pressure of 10 kPaG, a cycle time of 400 sec / column, and a pressure equalization of 15 sec. The TSA unit 20 is a two-column type, and each column is filled with 1.25 L of Ca-X zeolite (SA-600A manufactured by Tosoh) as an adsorbent, the adsorption pressure is 0.8 MPaG, the adsorption temperature is -35 ° C, and the desorption pressure. Was 0.1 MPaG, and the desorption temperature was 40 ° C.
In this case, the impurity composition of the argon gas at the outlet of the first reactor 5a, the outlet of the second reactor 5b, the outlet of the PSA unit 10, and the outlet of the TSA unit 20 was as shown in Table 1 below. The hydrocarbon composition in Table 1 represents the sum of the methane concentration and the C1-hydrocarbon equivalent concentration of C2-C6 hydrocarbons.
The composition of the argon gas at the outlet of the activated carbon adsorption tower 3 was as follows.
Activated carbon adsorption tower outlet Hydrogen: 50 mol ppm, oxygen: 200 mol ppm, nitrogen: 750 mol ppm, carbon monoxide: 1000 mol ppm, carbon dioxide: 60 mol ppm, methane: 20 mol ppm, C2-C6 hydrocarbon: 30 mol ppm in terms of C1 hydrocarbon, moisture: 500 mol ppm, oil content: less than 0.1 g / m ³ Note that the oxygen concentration in the purified argon gas was measured by an oxygen analyzer DE-150ε manufactured by GE Sensing & Inspection Technologies. The concentration of carbon monoxide and silicon dioxide is measured using a GC-FID manufactured by Shimadzu Corporation through a methanizer, the hydrogen concentration is measured by GC-PDD manufactured by GLscience, and the nitrogen concentration is a trace amount manufactured by Round Science. Measured with nitrogen analyzer PES-2000, hydrocarbon concentration is made by Shimadzu Measured by Tokoro made GC-FID, determined by calculation from increasing filtering CKD filter made VFA1000 for oil, moisture was measured using a GE Sensing & Inspection Technologies Co. dew DEWMET-2.

The catalyst used in the second reactor 5b was rhodium carrying alumina (0.5% alumina pellet made by NE Chemcat). Otherwise, argon gas was purified under the same conditions as in Example 1.
In this case, the impurity composition of argon gas at the outlet of the first reactor 5a, the outlet of the second reactor 5b, the outlet of the PSA unit 10, and the outlet of the TSA unit 20 was as shown in Table 1.

Comparative Example 1

The catalyst used in the first reactor 5a was alumina-supported platinum (NEchemcat DASH-220), and the catalyst used in the second reactor 5b was alumina-supported platinum (NEchemcat DASH-220). Further, each adsorption tower of the PSA unit 10 was filled with only Li-X type zeolite as an adsorbent. Otherwise, argon gas was purified under the same conditions as in Example 1.
In this case, the impurity composition of argon gas at the outlet of the first reactor 5a, the outlet of the second reactor 5b, the outlet of the PSA unit 10, and the outlet of the TSA unit 20 was as shown in Table 1.

Argon gas flowing out from the first reactor 5a was introduced into the dehydrator 6 at a flow rate of 4.0 L / min in a standard state. The dehydrator 6 was formed into a pipe shape having a nominal diameter of 32A, and filled with 8 L of activated alumina (KHD-24 manufactured by Sumitomo Chemical). Carbon monoxide was added from the carbon monoxide feeder 9 at a flow rate of 3.6 ml / min to the argon gas flowing out from the dehydrator 6 and introduced into the second reactor 5b. In this case, carbon monoxide in the argon gas is contained about 1.2 times the theoretical value necessary for consuming residual oxygen. Otherwise, argon gas was purified under the same conditions as in Example 1.
In this case, the impurity composition of the argon gas at the outlet of the first reactor 5a, the outlet of the second reactor 5b, the outlet of the PSA unit 10, and the outlet of the TSA unit 20 was as shown in Table 2.

Argon gas flowing out from the first reactor 5a was introduced into the dehydrator 6 at a flow rate of 4.0 L / min in a standard state. The dehydrator 6 was formed into a pipe shape having a nominal diameter of 32A, and filled with 8 L of activated alumina (KHD-24 manufactured by Sumitomo Chemical). Carbon monoxide was added from the carbon monoxide feeder 9 at a flow rate of 3.6 ml / min to the argon gas flowing out from the dehydrator 6 and introduced into the second reactor 5b. In this case, carbon monoxide in the argon gas is contained about 1.2 times the theoretical value necessary for consuming residual oxygen. Otherwise, argon gas was purified under the same conditions as in Example 2.
In this case, the impurity composition of the argon gas at the outlet of the first reactor 5a, the outlet of the second reactor 5b, the outlet of the PSA unit 10, and the outlet of the TSA unit 20 was as shown in Table 2.

Comparative Example 2

Argon gas flowing out from the first reactor 5a was introduced into the dehydrator 6 at a flow rate of 4.0 L / min in a standard state. The dehydrator 6 was formed into a pipe shape having a nominal diameter of 32A, and filled with 8 L of activated alumina (KHD-24 manufactured by Sumitomo Chemical). Carbon monoxide was added from the carbon monoxide feeder 9 at a flow rate of 3.6 ml / min to the argon gas flowing out from the dehydrator 6 and introduced into the second reactor 5b. In this case, carbon monoxide in the argon gas is contained about 1.2 times the theoretical value necessary for consuming residual oxygen. Otherwise, argon gas was purified under the same conditions as in Comparative Example 1.
In this case, the impurity composition of the argon gas at the outlet of the first reactor 5a, the outlet of the second reactor 5b, the outlet of the PSA unit 10, and the outlet of the TSA unit 20 was as shown in Table 2.

Comparative Example 3

Without performing the pretreatment of the adsorption treatment, the argon gas was purified only by the adsorption treatment using the PSA unit 10 and the TSA unit 20. The argon gas before purification contained 5000 molppm of carbon monoxide, 5000 molppm of nitrogen and 1 mol% of carbon dioxide as impurities. The PSA unit 10 is a four-column type, each column is in the shape of a pipe having a nominal diameter of 32 A and a length of 1 m, and 10 wt% of activated alumina (KHD-24 manufactured by Sumitomo Chemical Co.) is used as an adsorbent in each column. 90 wt% of UOP 5A-HP) was filled. The operating conditions of the PSA unit 10 were an adsorption pressure of 0.8 MPaG, a desorption pressure of 10 kPaG, a cycle time of 710 sec / column, and the argon gas was purified under conditions of a pressure equalization of 15 sec. The TSA unit 20 is a two-column type, and each column is filled with 1.25 L of Ca-X zeolite (SA-600A manufactured by Tosoh) as an adsorbent, the adsorption pressure is 0.8 MPaG, the adsorption temperature is -35 ° C, and the desorption pressure. The desorption temperature of 0.1 MPaG was 40 ° C.
The impurity composition of the argon gas at the outlet of the PSA unit 10 and the outlet of the TSA unit 20 in this case was as shown in Table 3. Further, the recovery rate of argon gas at the outlet of the PSA unit 10 was 65.3%.

Comparative Example 4

Each adsorption tower of the PSA unit 10 is filled with 30 wt% activated alumina (KHD-24 manufactured by Sumitomo Chemical Co., Ltd.) and 70 wt% Li-X zeolite (NSA-700 manufactured by Tosoh Corporation) as an adsorbent, and the cycle time is set to 1000 sec / column. . Otherwise, argon gas was purified under the same conditions as in Comparative Example 3.
The impurity composition of the argon gas at the outlet of the PSA unit 10 and the outlet of the TSA unit 20 in this case was as shown in Table 3. The recovery rate of argon gas at the outlet of the PSA unit 10 was 75.2%.

Comparative Example 5

Each adsorption tower of the PSA unit 10 is filled with 10 wt% of active alumina (KHD-24 manufactured by Sumitomo Chemical Co., Ltd.) and 90 wt% of Li-X zeolite (NSA-700 manufactured by Tosoh Corporation) as an adsorbent, and the cycle time is set to 770 sec / column. . Otherwise, argon gas was purified under the same conditions as in Comparative Example 3.
The impurity composition of the argon gas at the outlet of the PSA unit 10 and the outlet of the TSA unit 20 in this case was as shown in Table 3. The recovery rate of argon gas at the outlet of the PSA unit 10 was 69%.

The following points can be confirmed from the respective examples and comparative examples.
It can be confirmed that hydrocarbons can be effectively reacted by using a rhodium catalyst in the first reactor 5a, and that hydrogen can be prevented from being generated by using a ruthenium or rhodium catalyst in the second reactor 5b.
It can be confirmed that hydrocarbons can be effectively adsorbed by using activated alumina and X-type zeolite as the adsorbent used for the pressure swing adsorption method.
From Examples 1 and 2, it can be confirmed that the nitrogen concentration of the argon gas at the outlet of the PSA unit 10 is sufficiently reduced, and the recovered argon gas can be purified with high purity. Further, it can be confirmed that the nitrogen concentration of the argon gas at the outlet of the TSA unit 20 is further reduced.
The nitrogen concentration of the argon gas at the outlet of the PSA unit 10 in Comparative Example 5 is lower than the nitrogen concentration of the argon gas at the outlet of the PSA unit 10 in Comparative Example 4, but the cycle time is longer in Comparative Example 5 than in Comparative Example 4. Therefore, a large amount of argon gas is discarded, and the recovery rate of argon gas is reduced. On the other hand, the nitrogen concentration of the argon gas at the outlet of the TSA unit 20 in Comparative Example 4 and Comparative Example 5 is similarly reduced. Therefore, it can be confirmed that the load on the PSA unit can be reduced by using the TSA unit together.
From Comparative Examples 3 and 5, the adsorbent used for the pressure swing adsorption method is activated alumina and Li-X zeolite, so that the argon gas after purification is more purified than when activated alumina and Ca-A zeolite are used. It can be confirmed that the nitrogen concentration can be reduced. Further, it can be confirmed from Comparative Examples 4 and 5 that the nitrogen concentration of the argon gas can be sufficiently reduced even when purification is performed only by the adsorption treatment.

  The present invention is not limited to the above-described embodiments and examples. For example, equipment used for the recovery of argon gas is not limited to equipment using oil such as an oil rotary vacuum pump, and for example, an oilless vacuum pump may be used. Further, the TSA unit may be omitted according to the purity requirement of the argon gas.

  α ... purification device, 3 ... activated carbon adsorption tower, 5 ... reaction device, 5a ... first reactor, 5b ... second reactor, 6 ... dehydration device, 7 ... adsorption device, 8 ... oxygen supply device, 9 ... monoxide Carbon feeder, 10 ... PSA unit, 20 ... TSA unit

Claims (8)

A method for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil and nitrogen as impurities,
Adsorbing a part of hydrocarbons and oil in the argon gas to activated carbon,
Next, it is determined whether the amount of oxygen in the argon gas exceeds a set amount necessary to react with all of hydrogen, carbon monoxide, and hydrocarbons in the argon gas,
When the amount of oxygen in the argon gas is less than or equal to the set amount, oxygen is added to exceed the set amount,
Next, carbon monoxide, hydrogen, and hydrocarbon in the argon gas are reacted with oxygen using rhodium as a first reaction catalyst, thereby generating carbon dioxide and water in a state where oxygen remains. ,
Next, carbon monoxide is added so that the amount of carbon monoxide in the argon gas exceeds the set amount necessary to react with all of the remaining oxygen,
Next, oxygen and carbon monoxide in the argon gas are reacted using ruthenium, rhodium, or a mixture thereof as a second reaction catalyst, thereby generating carbon dioxide with carbon monoxide remaining. And
Next, a method for purifying argon gas, wherein at least carbon monoxide, carbon dioxide, water, and nitrogen in the argon gas are adsorbed on an adsorbent by a pressure swing adsorption method.   The moisture content in the argon gas is reduced by a dehydration process using a dehydrator between a reaction using the first reaction catalyst and a reaction using the second reaction catalyst. Of purifying argon gas.   The method for purifying argon gas according to claim 1 or 2, wherein activated alumina and X-type zeolite are used as the adsorbent used for the pressure swing adsorption method.   The method for purifying argon gas according to claim 3, wherein the activated alumina and the X-type zeolite are arranged in layers, and the weight ratio of the activated alumina to the X-type zeolite is 5/95 to 30/70. .   The argon according to any one of claims 1 to 4, wherein after the adsorption by the pressure swing adsorption method, nitrogen in the argon gas is adsorbed on the adsorbent by a thermal swing adsorption method at -10 ° C to -50 ° C. Gas purification method. An apparatus for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, hydrocarbons, oil and nitrogen as impurities,
An activated carbon adsorption tower into which the argon gas is introduced;
A first reactor into which argon gas flowing out from the activated carbon adsorption tower is introduced;
An oxygen supplier capable of adding oxygen to the argon gas introduced into the first reactor;
A second reactor into which argon gas flowing out of the first reactor is introduced;
A carbon monoxide supplier capable of adding carbon monoxide to the argon gas introduced into the second reactor;
An adsorption device into which argon gas flowing out from the second reactor is introduced,
In the activated carbon adsorption tower, activated carbon that adsorbs a part of hydrocarbons and oil in the argon gas is accommodated,
Rhodium is accommodated in the first reactor as a first reaction catalyst for reacting carbon monoxide, hydrogen, and hydrocarbon with oxygen in the argon gas,
Ruthenium, rhodium, or a mixture thereof is accommodated in the second reactor as a second reaction catalyst for reacting oxygen and carbon monoxide in the argon gas,
The said adsorption | suction apparatus has a PSA unit which adsorb | sucks at least carbon monoxide, carbon dioxide, water, and nitrogen in the said argon gas by a pressure swing adsorption method, The refinement | purification apparatus of the argon gas characterized by the above-mentioned.   The purification of argon gas according to claim 6, wherein a dehydrating device for reducing a moisture content in the argon gas flowing out from the first reactor is provided between the first reactor and the second reactor. apparatus.   The said adsorption | suction apparatus has the TSA unit which adsorb | sucks the nitrogen in the said argon gas which flows out out of the said PSA unit by the thermal swing adsorption method at -10 degreeC--50 degreeC, The refinement | purification of the argon gas of Claim 6 or 7 apparatus.

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