JP2011195434A - Refining method and refining apparatus for argon gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refining method and a refining device, both being practically usable and capable of purifying an argon gas to a high purity by reducing energy for refining by effectively reducing impurity contents of the argon gas to reduce the loading of a subsequent adsorption treatment.SOLUTION: In the method for purifying an argon gas at least including oxygen, hydrogen, carbon monoxide and nitrogen as impurities, the oxygen mol concentration in the argon gas is set to a value higher than 1/2 of the sum of the carbon monoxide mol concentration and hydrogen mol concentration; then, the oxygen is reacted with the carbon monoxide and hydrogen to generate carbon dioxide and water in such a state that the oxygen remains; then, the moisture content is reduced by dehydrating operation; then, at least the oxygen and carbon dioxide in the impurities are adsorbed by a pressure swing adsorption process using a carbonic adsorbent; and then, at least the nitrogen in the impurities is adsorbed by a thermal swing adsorption process at -10 to -50°C.

Description

  The present invention relates to a method and apparatus for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, 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 with combustible components as a pretreatment of the adsorption treatment (see Patent Documents 1 and 2).

  In the method disclosed in Patent Document 1, 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, Next, by using palladium or gold, which gives priority to the reaction of hydrogen and oxygen over the reaction of carbon monoxide and oxygen, oxygen in argon gas is reacted with carbon monoxide, hydrogen, etc. Carbon dioxide and water are produced in the state of remaining, and then 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 adsorbed. It is made to adsorb | suck to adsorption agent at the temperature of -10 degreeC--50 degreeC.

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

Japanese Patent No. 3496079 Japanese Patent No. 3737900

  In the method described in Patent Document 1, the amount of oxygen in the argon gas is less than the stoichiometric amount necessary for complete combustion of hydrogen, carbon monoxide, etc. in the pretreatment stage, and carbon monoxide and oxygen By using a catalyst that gives priority to the reaction of hydrogen and oxygen over the reaction of carbon dioxide, carbon dioxide and water are generated with carbon monoxide remaining. However, unreacted carbon monoxide undergoes a water-gas shift reaction with water vapor, so that hydrogen is regenerated, and there is a drawback that it is not possible to cope with a case where reduction of hydrogen is required. In addition, in the method described in Patent Document 1, carbon dioxide and water are adsorbed at room temperature after adsorbing carbon dioxide and water at the stage of the adsorption treatment after reacting oxygen in the impurities and the combustible component. Nitrogen is adsorbed on the adsorbent at −10 ° C. to −50 ° C. When regenerating an adsorbent that adsorbs carbon monoxide and nitrogen at such a low temperature, carbon monoxide is industrially disadvantageous because it requires more energy to desorb from the adsorbent than nitrogen.

  In the method described in Patent Document 2, the amount of oxygen in the argon gas is set to a sufficient amount for complete combustion of hydrogen, carbon monoxide, etc. in the pretreatment stage, so that oxygen remains in a state where oxygen remains. It produces carbon and water. However, in order to adsorb oxygen, it is necessary to lower the temperature during adsorption to about -170 ° C. That is, since oxygen remains in the pretreatment of the adsorption treatment, there is a problem that the cooling energy during the adsorption treatment increases and the purification load increases.

  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, and nitrogen as impurities, wherein the oxygen molar concentration in the argon gas is a carbon monoxide molar concentration and a hydrogen molar concentration. If it is less than or equal to 1/2 of the sum, it is set to a value exceeding 1/2 by adding oxygen, and then oxygen in the argon gas is reacted with carbon monoxide and hydrogen using a catalyst. , Producing carbon dioxide and water in a state in which oxygen remains, and then reducing the moisture content in the argon gas by dehydration, and then removing at least oxygen and carbon dioxide from impurities in the argon gas. Adsorbed by a pressure swing adsorption method using a carbon-based adsorbent, and then at least nitrogen in impurities in the argon gas is −10 Characterized by suction by thermal swing adsorption method at ~-50 ° C..
According to the present invention, by reacting oxygen in argon gas with carbon monoxide and hydrogen, carbon dioxide and water are generated with oxygen remaining, and then the moisture content of the argon gas is reduced by dehydration. Reduced. As a result, the main impurities of argon gas are oxygen, carbon dioxide, and nitrogen, which eliminates the need for moisture adsorption during the adsorption of impurities by the pressure swing adsorption method and reduces the adsorption load. A carbon-based adsorbent having a high oxygen adsorbing effect is used as the adsorbent. As a result, the oxygen adsorption effect by the pressure swing adsorption method using the PSA unit is enhanced, so that the subsequent oxygen swing adsorption by the thermal swing adsorption method using the TSA unit is unnecessary, and the impurity adsorption by the thermal swing adsorption method. The temperature can be made higher than when oxygen is adsorbed. Therefore, even if oxygen remains in the pretreatment of the adsorption treatment, the recovery rate and purity of argon gas can be increased without increasing the cooling energy.

  In the present invention, in order to enhance the oxygen adsorption effect by the pressure swing adsorption method, the carbon-based adsorbent is preferably a carbon molecular sieve.

The apparatus of the present invention is an apparatus for purifying an argon gas containing at least oxygen, hydrogen, carbon monoxide, and nitrogen as impurities, the reactor into which the argon gas is introduced, and the reactor that is introduced into the reactor When the oxygen molar concentration in the argon gas is ½ or less of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, the concentration adjusting device is set to a value exceeding 1/2 by adding oxygen; A drier that reduces the moisture content of the argon gas flowing out of the reactor by performing a dehydration operation; and an adsorption device connected to the drier, wherein oxygen in the argon gas is one in the reactor. The reactor is filled with a catalyst so that carbon dioxide and water are generated in a state where oxygen remains by reacting with carbon oxide and hydrogen, and the adsorption device is configured to use the argon gas. A PSA unit that adsorbs at least oxygen and carbon dioxide in impurities in a pressure swing adsorption method using a carbon-based adsorbent, and at least nitrogen in impurities in the argon gas at −10 ° C. to −50 ° C. And a TSA unit adsorbed by the thermal swing adsorption method.
According to the apparatus of the present invention, the method of the present invention can be carried out.

  According to the present invention, by effectively reducing the impurity content of argon gas, it is possible to reduce the load of subsequent adsorption treatment, reduce the energy required for purification, and purify argon gas with high purity. Methods and apparatus can be provided.

Arrangement explanatory drawing of the purification apparatus of argon gas concerning the embodiment of the present invention Structure explanatory drawing of the pressure swing adsorption | suction apparatus in the refiner | purifier of the argon gas which concerns on embodiment of this invention Structure explanatory drawing of the temperature swing adsorption apparatus in the refiner | purifier of the argon gas which concerns on embodiment of this invention

  An argon gas refining device α shown in FIG. 1 is for purifying spent argon gas supplied from an argon gas supply source 1 such as a polycrystalline silicon casting furnace so that it can be reused. 2, a reactor 3, a concentration adjusting device 4, a dryer 5, a cooler 8, and an adsorption device 9.

  The argon gas supplied from the supply source α is dust-removed by a filter (not shown) or the like and introduced into the heater 2 through gas feeding means (not shown) such as a blower. The trace amount of impurities contained in the argon gas to be purified is at least oxygen, hydrogen, carbon monoxide, and nitrogen, but may contain other impurities such as carbon dioxide, hydrocarbons, and water. The concentration of impurities in the argon gas to be purified is not particularly limited, and is, for example, about 5 mol ppm to 40000 mol ppm. The heating temperature of the argon gas by the heater 2 is preferably 250 ° C. or higher in order to complete the reaction in each of the reactors 3 and 6, and 450 ° C. or lower from the viewpoint of preventing shortening of the catalyst life. preferable.

  Argon gas heated by the heater 2 is introduced into the reactor 3. When the oxygen molar concentration in the argon gas introduced into the reactor 3 is less than or equal to 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, the concentration adjusting device 4 adds 1 / Set to a value greater than 2. The concentration adjusting device 4 of the present embodiment includes a concentration measuring device 4a, an oxygen supply source 4b, an oxygen amount adjusting device 4c, and a controller 4d. The concentration measuring device 4a measures the oxygen molar concentration, the carbon monoxide molar concentration, and the hydrogen molar concentration in the argon gas introduced into the reactor 3, and sends the measurement signal to the controller 4d. When the measured oxygen molar concentration is ½ or less of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, the controller 4d performs control corresponding to the amount of oxygen necessary to obtain a value exceeding 1/2. A signal is sent to the oxygen amount adjuster 4c. The oxygen amount adjuster 4c adjusts the opening of the flow path from the oxygen supply source 4b to the reactor 3 so that an amount of oxygen corresponding to the control signal is supplied. Thereby, the oxygen molar concentration in the argon gas to be purified is set to a value exceeding 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration.

  Reactor 3 is filled with a catalyst that reacts oxygen with hydrogen and carbon monoxide. As a result, oxygen in the argon gas reacts with carbon monoxide and hydrogen in the reactor 3 to generate carbon dioxide and water with oxygen remaining. In addition, although argon gas collect | recovered from a polycrystalline-silicon casting furnace etc. contains a hydrocarbon as a combustible component, the molar concentration is usually 1/100 or less of the total molar concentration of hydrogen and carbon monoxide. Therefore, normally, if the oxygen molar concentration is set so as to slightly exceed 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, carbon dioxide and water can be generated with oxygen remaining. The catalyst charged in the reactor 3 is not particularly limited as long as it allows oxygen to react with carbon monoxide and hydrogen. For example, a catalyst in which platinum, platinum alloy, palladium or the like is supported on alumina or the like can be used. .

  The dryer 5 reduces the moisture content of the argon gas flowing out from the reactor 3 by performing a dehydration operation. A commercially available one may be used as the dryer 5. For example, a pressurized dehydrator that pressurizes argon gas to remove moisture with an adsorbent and regenerates the adsorbent under reduced pressure. A refrigerating dehydrator that removes the generated moisture, a heat regeneration dehydrator that removes moisture contained in the argon gas with a dehydrating agent, and heats and regenerates the dehydrating agent can be used. It is preferable for effectively reducing the moisture content, and it is preferable to remove about 99% of the moisture in the argon gas.

  An adsorption device 9 is connected to the dryer 5 via a cooler 8. The argon gas dehydrated by the dryer 5 and reduced in water content is introduced into the adsorption device 9 after being cooled by the cooler 8. The adsorption device 9 includes a PSA unit 10 and a TSA unit 20. The PSA unit 10 adsorbs at least oxygen and carbon dioxide among impurities in argon gas by a pressure swing adsorption method at room temperature using a carbon-based adsorbent. The TSA unit 20 adsorbs at least nitrogen in the impurities in the argon gas by a thermal swing adsorption method at −10 ° C. to −50 ° C.

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 has a compressor 12 for compressing argon gas flowing out from the reactor 3 and four first to fourth adsorption towers 13. Filled with carbon-based adsorbent. As the carbon-based adsorbent, carbon molecular sieve is preferable for enhancing the oxygen adsorption effect.
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 TSA unit 20 via the pressure control valve 13t, and the pressure of the argon gas introduced into the TSA unit 20 is constant.
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 TSA unit 20 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.
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 reactor 3 is introduced from the compressor 12 to the first adsorption tower 13 through the switching valve 13b. As a result, an adsorption process is performed by adsorbing at least carbon dioxide and moisture in the argon gas introduced in the first adsorption tower 13 to the adsorbent, and the argon gas with reduced impurity content is first adsorbed. It is sent from the tower 13 to the TSA unit 20 through the outflow pipe 13m. At this time, a part of the argon gas sent to the outflow pipe 13m is sent to another adsorption tower (second adsorption tower 13 in the present embodiment) via the boosting pipe 13o and the flow rate control valve 13u, and the second adsorption. In the tower 13, a pressure increase II step is performed.
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 another adsorption tower (the fourth adsorption tower 13 in this embodiment) is opened, and the switching valve 13x is opened. Open one of the. 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 opened, so that the first adsorption tower 13 and the fourth adsorption tower 13 are closed. A depressurization II step is performed in which the fourth adsorption tower 13 recovers the gas until the internal pressure becomes uniform or almost uniform between the towers 13. At this time, 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, and 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 pressure increase I process is performed by closing the switching valve 13e of the first adsorption tower 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 to temporarily enter a standby state without a process. This 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, and another adsorption tower in the adsorption process ( In the present embodiment, a part of the argon gas sent from the fourth adsorption tower 13) to the outflow pipe 13m is sent to the first adsorption tower 13 via the pressure raising pipe 13o and the flow rate control valve 13u, and the first adsorption tower 13 is supplied. The step-up II process is performed in
The above steps are sequentially repeated in each of the first to fourth adsorption towers 13 so that the argon gas with a reduced impurity content is continuously sent to the TSA unit 20.
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.

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, and it is preferable to use X-type zeolite or Y-type zeolite whose exchange ion is a divalent cation, such as calcium (Ca) or lithium (Li). An ion-exchanged zeolite adsorbent can be used, and the divalent cation is at least one selected from magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). It is more preferable that
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 primary pressure control 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 primary pressure control valve 231.
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 second adsorption tower 23, helium gas containing impurities is released into the atmosphere, and the pressure is reduced to almost 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 purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, and nitrogen, the oxygen molar concentration in the argon gas is the sum of the carbon monoxide molar concentration and the hydrogen molar concentration. Is set to a value exceeding 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration by adding oxygen, oxygen in the argon gas is changed to carbon monoxide. In addition, by reacting with hydrogen and a catalyst, carbon dioxide and water are generated with oxygen remaining, and then the moisture content in the argon gas is reduced by dehydration. As a result, since the main impurities of argon gas are oxygen, carbon dioxide, and nitrogen, the adsorption of moisture becomes unnecessary during the adsorption of impurities by the subsequent pressure swing adsorption method, and the adsorption load is reduced. A carbon-based adsorbent having a high oxygen adsorption effect is used as an adsorbent by the adsorption method. As a result, the oxygen adsorption effect by the pressure swing adsorption method is enhanced, so that the oxygen adsorption in the subsequent thermal swing adsorption method is unnecessary, and the impurity adsorption temperature in the thermal swing adsorption method is compared with the case of adsorbing oxygen. Can be high. Therefore, even if oxygen remains in the pretreatment of the adsorption treatment, the recovery rate and purity of argon gas can be increased without increasing the cooling energy.

Argon gas was purified using the purification apparatus α. Argon gas contains 500 mol ppm of oxygen, 20 mol ppm of hydrogen, 1800 mol ppm of carbon monoxide, 1000 mol ppm of nitrogen, 20 mol ppm of carbon dioxide and 20 mol ppm of water as impurities. This argon gas was introduced into the reactor 3 at a flow rate of 3.74 L / min under standard conditions, and oxygen was added to the argon gas at a flow rate of 3.4 mL / min under standard conditions. The reactor 3 was filled with 45 mL of an alumina-supported platinum catalyst, and the reaction conditions were a temperature of 300 ° C., an atmospheric pressure, and a space velocity of 5000 / h.
The argon gas flowing out from the reactor 3 was cooled to −35 ° C. using a refrigeration dehydrator as the dryer 5 to remove the moisture, thereby performing a dehydration operation, thereby reducing the moisture content of the argon gas.
After the argon gas flowing out from the dryer 5 was cooled by the cooler 8, the impurity content was reduced by the adsorption device 9. The PSA unit 10 is of a three-column type, and each column is filled with 1.25 L of carbon molecular sieve (3k-172, manufactured by Nippon Envirochemicals) of 2 mm in diameter as an adsorbent, and the adsorption pressure is 0.9 MPa. The pressure was 0.1 MPa.
Argon gas purified by the PSA unit 10 was introduced into the TSA unit 20. The TSA unit 20 is of a two-column type, and each column is filled with 1.5 L of CaX type zeolite as an adsorbent, the adsorption pressure is 0.8 MPa, the adsorption temperature is −35 ° C., the desorption pressure is 0.1 MPa, and the desorption temperature is 40 C.
The composition of the purified argon gas flowing out from the TSA unit 20 is shown in Table 1 below. The oxygen concentration in the purified argon gas was measured with a trace oxygen analyzer model 311 manufactured by Teledyne, and the concentrations of carbon monoxide and carbon dioxide were measured with a Shimadzu GC-FID through a methanizer. The hydrogen concentration was measured using GC-PID manufactured by GLscience.

  Argon gas was purified in the same manner as in Example 1 except that the oxygen addition flow rate was 5.00 mL / min in the standard state. The composition of the purified argon gas is shown in Table 1 below.

  Argon gas was purified in the same manner as in Example 1 except that the adsorbent used in the TSA unit 20 was MgX type zeolite. The composition of the purified argon gas is shown in Table 1 below.

  Argon gas was purified in the same manner as in Example 1 except that the adsorption temperature in the TSA unit 20 was set to −50 ° C. The composition of the purified argon gas is shown in Table 1 below.

Comparative Example 1

  Argon gas was purified in the same manner as in Example 1 except that the oxygen addition flow rate was 1 mL / min in the standard state. The composition of the purified argon gas is shown in Table 1 below.

Comparative Example 2

  Argon gas was purified in the same manner as in Example 1 except that the adsorbent used in the PSA unit 10 was CaA-type zeolite. The composition of the purified argon gas is shown in Table 1 below.

Comparative Example 3

  Argon gas was purified in the same manner as in Example 1 except that the dehydration operation was not performed using a dryer. The composition of the purified argon gas is shown in Table 1 below.

  From Table 1 above, according to each example, the argon gas purity is higher than each comparative example, the oxygen concentration is lower than Comparative Examples 2 and 3, the carbon monoxide concentration is lower than Comparative Example 1, It can be confirmed that the hydrogen concentration is lower than 3.

α ... Purification device, 3 ... Reactor, 4 ... Concentration control device, 5 ... Dryer, 9 ... Adsorption device, 10 ... PSA unit, 20 ... TSA unit

Claims (3)

A method for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, and nitrogen as impurities,
When the oxygen molar concentration in the argon gas is less than or equal to 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, it is set to a value exceeding 1/2 by adding oxygen,
Next, by reacting oxygen in the argon gas with carbon monoxide and hydrogen using a catalyst, carbon dioxide and water are generated with oxygen remaining,
Next, the moisture content in the argon gas is reduced by a dehydration operation,
Next, at least oxygen and carbon dioxide among impurities in the argon gas are adsorbed by a pressure swing adsorption method using a carbon-based adsorbent,
Thereafter, at least nitrogen in the impurities in the argon gas is adsorbed by a thermal swing adsorption method at -10 ° C to -50 ° C.   The method for purifying argon gas according to claim 1, wherein the carbon-based adsorbent is a carbon molecular sieve. An apparatus for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, and nitrogen as impurities,
A reactor into which the argon gas is introduced;
When the molar oxygen concentration in the argon gas introduced into the reactor is ½ or less of the sum of the molar concentration of carbon monoxide and the molar hydrogen concentration, it is increased to a value exceeding ½ by adding oxygen. A concentration control device to be set;
A dryer that reduces the moisture content of the argon gas flowing out of the reactor by performing a dehydration operation;
An adsorption device connected to the dryer,
In the reactor, oxygen in the argon gas reacts with carbon monoxide and hydrogen, so that carbon dioxide and water are generated with oxygen remaining, and the reactor is filled with a catalyst.
The adsorption device includes a PSA unit that adsorbs at least oxygen and carbon dioxide in impurities in the argon gas by a pressure swing adsorption method using a carbon-based adsorbent, and at least nitrogen in impurities in the argon gas. And a TSA unit adsorbed by a thermal swing adsorption method at −10 ° C. to −50 ° C.

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