JP5679433B2 - Argon gas purification method and purification apparatus - Google Patents

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., and more than the reaction between carbon monoxide and oxygen. A catalyst that gives priority to the reaction between hydrogen and oxygen is used. Therefore, complete combustion of hydrogen is achieved by the reaction, and unreacted carbon monoxide remains positively. However, although a trace amount of hydrogen is difficult to remove by an adsorption treatment, in many cases, the use of argon gas allows hydrogen to remain. On the other hand, carbon monoxide becomes a catalyst poison and is difficult to adsorb than carbon dioxide depending on a general adsorbent such as zeolite. That is, in the previous stage of the adsorption treatment, complete combustion of hydrogen with few problems even if it is left is attempted, while carbon monoxide that is difficult to adsorb due to the possibility of reducing the function of the catalyst is actively left. This is an unreasonable process.

  In the method described in Patent Document 2, the amount of oxygen in the argon gas is set to a sufficient amount to completely burn hydrogen, carbon monoxide, etc., and the oxygen in the argon gas is converted to carbon monoxide using a palladium-based catalyst. , Reacting with hydrogen and the like. For this reason, complete reaction of hydrogen, carbon monoxide, and the like is achieved by the reaction, and oxygen, which often remains a problem in the use of argon gas, actively remains. However, as described above, in the use of argon gas, hydrogen is often allowed to remain. On the other hand, in order to adsorb oxygen, it is necessary to lower the temperature during adsorption to about -170 ° C. In other words, in the previous stage of the adsorption process, complete combustion of hydrogen with few problems even if left is attempted, while oxygen that increases the purification load due to an increase in cooling energy during the adsorption process is actively left. Unreasonable processing.

  According to the above-mentioned unreasonable prior art, there is a problem that the management cost and the construction cost of the argon gas recovery facility increase. It is an object of the present invention to provide an argon gas purification method and a purification apparatus that can solve such 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 calculated by combining the carbon monoxide molar concentration and the hydrogen molar concentration. When the oxygen molar concentration in the argon gas is set to a value less than 1/2 of the sum and exceeding 1/2 of the carbon monoxide molar concentration , the oxygen molar concentration is the carbon monoxide molar concentration and the hydrogen molar concentration. Hydrogen is added when it is ½ or more of the sum with the concentration, oxygen is added when the oxygen molar concentration is ½ or less of the carbon monoxide molar concentration, and then the reaction between hydrogen and oxygen Using a catalyst that prioritizes the reaction between carbon monoxide and oxygen, and reacting oxygen in the argon gas with carbon monoxide and hydrogen to produce carbon dioxide and water with hydrogen remaining, After that, the content ratio of impurities in the argon gas was reduced using an adsorbent, wherein the catalyst is characterized in that it comprises as a main component platinum.
According to the present invention, the oxygen molar concentration in the argon gas is set to less than ½ of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, and the reaction between carbon monoxide and oxygen rather than the reaction between hydrogen and oxygen. Oxygen in argon gas is reacted with carbon monoxide and hydrogen using a catalyst that gives priority to the above. As a result, when hydrogen remains with little problem even if it is left and is adsorbed and removed, it is possible to achieve complete combustion of oxygen to increase the cooling energy, and further, the catalyst function may be deteriorated and carbon dioxide. There is no need to actively leave carbon monoxide, which is more difficult to adsorb than carbon. Thereby, management of the refinery facility can be facilitated and the size can be reduced, and energy consumption can be reduced.
To prioritize the reaction of carbon monoxide with oxygen than the reaction of hydrogen and oxygen in the method of the present invention, said catalyst including as a main component platinum. In order to efficiently adsorb carbon dioxide, water, and nitrogen in the method of the present invention, when reducing the content of impurities in the argon gas using an adsorbent, at least carbon dioxide and water in the impurities are at room temperature. It is preferable that at least nitrogen in the impurities is adsorbed by a thermal swing adsorption method at −10 ° C. to −50 ° C. after adsorption by the pressure swing adsorption method.

In the process of the present invention, to set the oxygen molar concentration in the argon gas to a value greater than 1/2 of the carbon monoxide molar.
Thereby, complete combustion of carbon monoxide which may reduce the function of the catalyst can be achieved. In this case, when setting the oxygen molar concentration in the argon gas, hydrogen is added when the oxygen molar concentration is 1/2 or more of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration. If it is 1/2 or less of carbon monoxide molar you add oxygen. Thereby, since carbon monoxide is not added when setting oxygen molar concentration, it can prevent that the reaction by-product of carbon monoxide and water reduces the purity of argon gas.
In the method of the present invention, after reducing the content of impurities in the argon gas using an adsorbent, the hydrogen concentration in the argon gas may be reduced by removing hydrogen in the impurities. Thereby, it can respond to the case where it is requested | required that the hydrogen concentration in argon gas is further reduced rather than reducing using an adsorbent.

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 A concentration controller for setting the oxygen molar concentration in the argon gas to a value less than 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration and exceeding 1/2 of the carbon monoxide molar concentration; and the reactor When the oxygen molar concentration in the argon gas is set, when the oxygen molar concentration is ½ or more of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, the hydrogen is it is added, if the oxygen molar concentration is 1/2 or less of carbon monoxide molar concentrations are added oxygen, the argon oxygen may react with carbon monoxide and hydrogen in the gas in the reactor The reactor is filled with a catalyst that gives priority to the reaction of carbon monoxide and oxygen over the reaction of hydrogen and oxygen so that carbon dioxide and water are generated in a state where hydrogen remains. may have a sorbent for reducing the content of impurities in the argon gas flowing out of the reactor, the catalyst is characterized in that it comprises as a main component platinum.
According to the apparatus of the present invention, the method of the present invention can be carried out.

  According to the present invention, the purity of the recovered impurity-containing argon gas is increased by a rational purification process, so that the functional degradation of the purification catalyst is prevented, the purification load is reduced, and the management costs and construction costs of the recovery equipment are reduced. It is possible to provide a method and an apparatus that contribute to the reduction of the above.

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 cooler 5, and an adsorption device 6.

  The argon gas supplied from the supply source α is dedusted by a filter (not shown) and introduced into the heater 2 via the blower 7 as a gas feeding means. Impurities contained in the argon gas to be purified are at least oxygen, hydrogen, carbon monoxide, and nitrogen, but may contain other impurities such as carbon dioxide and hydrocarbons. 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 set to 200 ° C. or higher from the viewpoint of preventing carbon monoxide from adsorbing on the active sites of the catalyst and inhibiting the reaction between hydrogen and oxygen in the reactor 3. From the viewpoint of preventing shortening of the catalyst life, the temperature is preferably 300 ° C. or lower.

  Argon gas heated by the heater 2 is introduced into the reactor 3. The concentration controller 4 sets the oxygen molar concentration in the argon gas introduced into the reactor 3 through the heater 2 to be less than ½ of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration. The concentration adjusting device 4 of this embodiment includes a concentration measuring device 4a, a hydrogen supply source 4b, a hydrogen amount adjusting device 4c, an oxygen supply source 4d, an oxygen amount adjusting device 4e, and a controller 4f. The concentration measuring device 4a measures the oxygen molar concentration, carbon monoxide molar concentration, and hydrogen molar concentration in the argon gas introduced into the heater 2, and sends the measurement signal to the controller 4f. When the measured oxygen molar concentration is ½ or more of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, the controller 4f generates a control signal corresponding to the amount of hydrogen necessary to make it less than ½. When the measured oxygen molar concentration is less than 1/2 of the carbon monoxide molar concentration, the control signal corresponding to the amount of oxygen necessary to exceed 1/2 is sent to the hydrogen amount regulator 4c. It sends to the oxygen amount controller 4e. The hydrogen amount adjuster 4c adjusts the opening of the flow path from the hydrogen supply source 4b to the reactor 3 so that an amount of hydrogen corresponding to the control signal is supplied. The oxygen amount adjuster 4e adjusts the opening of the flow path from the oxygen supply source 4d to the reactor 3 so that an amount of oxygen corresponding to the control signal is supplied. Thus, when setting the oxygen molar concentration in the argon gas to be purified, hydrogen is added if the oxygen molar concentration is ½ or more of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration. Oxygen is added when the molar concentration of carbon oxide is ½ or less.

  The reactor 3 is filled with a catalyst that prioritizes the reaction of carbon monoxide and oxygen over the reaction of hydrogen and oxygen. Thus, oxygen in the argon gas reacts with carbon monoxide and hydrogen at a temperature of 200 ° C. to 300 ° C. in the reactor 3 to generate carbon dioxide and water with hydrogen remaining. The catalyst contains platinum as a main component. In this embodiment, a platinum catalyst supported by alumina is used. The catalyst is not limited to platinum. For example, a platinum alloy may be used, and a small amount of other components such as palladium may be included.

  The cooler 5 is connected to the reactor 3 and cools the argon gas flowing out from the reactor 3 to about 40 ° C. Argon gas cooled by the cooler 5 is introduced into the adsorption device 6.

  The adsorption device 6 has an adsorbent for reducing the content of impurities in the argon gas flowing out from the reactor 3. The adsorption apparatus 6 of the present embodiment has a PSA unit 10 that performs adsorption of impurities in argon gas by a pressure swing adsorption method at room temperature, and a TSA unit 20 that performs a thermal swing adsorption method at −10 ° C. to −50 ° C. Then, after the adsorption by the pressure swing adsorption method, the adsorption by the thermal swing adsorption method is performed.

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. Adsorbent is filled. As the adsorbent, those suitable for adsorption of carbon dioxide and moisture are used, and for example, activated alumina, activated carbon and CaA type zeolite are used.
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, 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. In Step II, a step-up II process is performed.
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 that shown in FIG. 2, and the number of towers may be other than 4, for example.

A known TSA unit 20 can be used. For example, the TSA unit 20 of this embodiment 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 an argon gas cooled by the precooler 21 are used. Furthermore, it has a heat exchange type cooler 22 for cooling, a first and second adsorption tower 23, and a heat exchanger 24 that covers each adsorption tower 23. 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 for example, CaX type zeolite is used.
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 exchanger 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. 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.
Note that the TSA unit 20 is not limited to the one shown in FIG.

  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. Next, using a catalyst that prioritizes the reaction between carbon monoxide and oxygen over the reaction between hydrogen and oxygen, and reacting oxygen in the argon gas with carbon monoxide and hydrogen. Thus, carbon dioxide and water are produced with hydrogen remaining, and then the content of impurities in the argon gas can be reduced using an adsorbent. This makes it possible to achieve complete combustion of oxygen to increase the cooling energy in the case of actively remaining hydrogen with few problems even if it remains, and removing it by adsorption. Further, there is no need to positively leave carbon monoxide, which may lower the catalytic function and is more difficult to adsorb than carbon dioxide. Thereby, management of the refinery facility can be facilitated and the size can be reduced, and energy consumption can be reduced. Further, when reducing the content of impurities in the argon gas by using an adsorbent, after adsorbing at least carbon dioxide and water in the impurities by a pressure swing adsorption method at room temperature, at least nitrogen in the impurities Is adsorbed by a thermal swing adsorption method at −10 ° C. to −50 ° C., so that carbon dioxide, water, and nitrogen can be adsorbed efficiently. Further, by setting the oxygen molar concentration in the argon gas to a value exceeding 1/2 of the carbon monoxide molar concentration, it is possible to achieve complete combustion of carbon monoxide which may reduce the function of the catalyst. Furthermore, when setting the oxygen molar concentration in argon gas, if the oxygen molar concentration is more than half of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, hydrogen is added and the oxygen molar concentration is When the carbon molar concentration is ½ or less, by adding oxygen, carbon monoxide is not added, so that the reaction by-product of carbon monoxide and water can be prevented from lowering the purity of the argon gas. .

Using the purification apparatus α, the argon gas recovered from the polycrystalline silicon casting furnace was purified. Argon gas contains 3000 mol ppm of nitrogen, 550 mol ppm of oxygen, 200 mol ppm of hydrogen, 1000 mol ppm of carbon monoxide, and 10 mol ppm of carbon dioxide as impurities. The argon gas was pressurized to 0.05 MPaG by the blower 7 and introduced into the heater 2 at a flow rate of 200 Nm ³ / h, temperature-controlled at 250 ° C., and introduced into the reactor 3. The reactor 3 was a cylinder having a diameter of 400 mm and a length of 1,200 mm, and was filled with a platinum catalyst (DASH-220 manufactured by NE Chemcat) supported by alumina. Due to the reaction in the reactor 3, the impurity concentration of argon gas is 3000 mol ppm for nitrogen, 1 mol ppm or less for oxygen, 100 mol ppm for hydrogen, 1 mol ppm or less for carbon monoxide, 1010 mol ppm for carbon dioxide, moisture Was 100 mol ppm.
The argon gas was cooled to 40 ° C. by a cooler 5 constituted by a water-cooled cooler, and then introduced into one of the adsorption towers 13 of the PSA unit 10 via the compressor 12. Each adsorption tower 13 has a cylindrical shape with a diameter of 600 mm and a length of 1800 mm, and is filled with CaA-type zeolite (5AHP manufactured by Union Showa) as an adsorbent. In each adsorption tower 13, one cycle of the pressure raising process, the adsorption process, the washing process, and the desorption process was performed in 800 seconds. The argon gas was pressurized to 0.8 MPaG by the compressor 12. The flow rate of argon gas flowing out from the PSA unit 10 is 120 Nm ³ / h, and the impurity concentration in argon is 150 mol ppm for nitrogen, 0.1 mol ppm or less for oxygen, 100 mol ppm for hydrogen, and 0.1 mol for carbon monoxide. 5 mol ppm or less, moisture and carbon dioxide were 0.5 mol ppm or less, and the dew point was −70 ° C. or less.
The argon gas purified by the PSA unit 10 was cooled in the precooler 21 and the cooler 22 and then introduced into one adsorption tower 23 of the TSA unit 20. Each adsorption tower 23 has a cylindrical shape with a diameter of 900 mm and a length of 1500 mm, and has 50 inner tubes filled with CaX-type zeolite (SA600A manufactured by Tosoh Corporation) as an adsorbent. The argon gas passing through one inner tube was cooled to −35 ° C. by the heat exchanger 24, and the argon gas passing through the other inner tube was heated to 40 ° C. The flow rate of argon gas flowing out of the TSA unit 20 is 110 Nm ³ / h, and the impurity concentration in argon is 0.1 mol ppm or less for nitrogen, 0.1 mol ppm or less for oxygen, 110 mol ppm for hydrogen, and monoxide Carbon was 0.5 mol ppm or less, carbon dioxide was 0.5 mol ppm or less, the dew point was −70 ° C. or less, and hydrogen was the only substantial impurity.

The present invention is not limited to the above embodiments and examples. For example, when it is necessary to reduce the hydrogen concentration in the argon gas purified according to the present invention, a hydrogen removing device 30 as shown by a broken line in FIG. 1 may be provided. The hydrogen removing device 30 is a reactor in which argon gas and hydrogen are separated by a hydrogen permeable gas separation membrane such as a polyimide membrane, or a catalyst filled with a metal oxide such as copper or nickel. Thus, it can be constituted by a material that reacts with the metal oxide to remove hydrogen. The moisture generated by the reaction between the metal oxide and hydrogen is removed by filling a moisture absorbent such as alumina gel or zeolite on the downstream side of the catalyst, for example. The hydrogen removal apparatus 30 may be disposed downstream of the TSA unit 20 as illustrated in FIG. 1 or may be disposed between the PSA unit 10 and the TSA unit 20. Thus, after reducing the impurity content in the argon gas using the adsorbent, the hydrogen concentration in the argon gas can be further reduced than by using the adsorbent by removing the hydrogen in the impurity. For example, it can be 1 mol ppm or less. A hydrogen removing device 30 having a cylindrical reactor having a diameter of 300 mm is provided downstream of the TSA unit 20, and the reactor is filled with a catalyst mainly composed of copper oxide, and passes through the argon gas purified by the above embodiment. As a result, the flow rate of argon gas was 110 Nm ³ / h, and the impurity concentration in argon was 0.1 mol ppm or less for nitrogen, 0.1 mol ppm or less for oxygen, 0.5 mol ppm or less for hydrogen, Carbon oxide was 0.5 mol ppm or less, carbon dioxide was 0.5 mol ppm or less, and the dew point was −70 ° C. or less, confirming the removal of hydrogen. By providing such a hydrogen removing device 30, it is possible to cope with applications in which reduction of hydrogen contained in the argon gas is required.

α ... purification device, 3 ... reactor, 4 ... concentration control device, 6 ... adsorption device, 10 ... PSA unit, 20 ... TSA unit

Claims (4)

A method for purifying argon gas containing at least oxygen, hydrogen, carbon monoxide, and nitrogen as impurities,
The oxygen molar concentration in the argon gas is set to a value less than 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration , and more than 1/2 of the carbon monoxide molar concentration ,
When setting the oxygen molar concentration in the argon gas, hydrogen is added if the oxygen molar concentration is ½ or more of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, and the oxygen molar concentration is carbon monoxide. If it is less than half the molar concentration, add oxygen,
Next, using a catalyst that prioritizes the reaction between carbon monoxide and oxygen over the reaction between hydrogen and oxygen, the oxygen in the argon gas is reacted with carbon monoxide and hydrogen, leaving hydrogen remaining. Producing carbon dioxide and water,
Thereafter, the content of impurities in the argon gas is reduced using an adsorbent ,
The said catalyst contains platinum as a main component , The purification method of argon gas characterized by the above-mentioned . When reducing the content of impurities in the argon gas using an adsorbent, at least carbon dioxide and water in the impurities are adsorbed by a pressure swing adsorption method at room temperature, and then at least nitrogen in the impurities is removed. The method for purifying argon gas according to claim 1, wherein the adsorption is performed by a thermal swing adsorption method at -10 ° C to -50 ° C. 3. The purification of argon gas according to claim 1, wherein the hydrogen concentration in the argon gas is reduced by removing hydrogen in the impurities after reducing the impurity content in the argon gas using an adsorbent. 4. Method. 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;
The oxygen molar concentration in the argon gas introduced into the reactor is set to a value less than 1/2 of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration , and more than 1/2 of the carbon monoxide molar concentration. A concentration adjusting device;
An adsorption device connected to the reactor,
When setting the oxygen molar concentration in the argon gas, hydrogen is added if the oxygen molar concentration is ½ or more of the sum of the carbon monoxide molar concentration and the hydrogen molar concentration, and the oxygen molar concentration is carbon monoxide. If it is less than or equal to 1/2 the molar concentration, oxygen is added,
In the reactor, oxygen in the argon gas reacts with carbon monoxide and hydrogen, so that carbon dioxide and water are generated in a state where hydrogen remains, rather than carbon monoxide than the reaction between hydrogen and oxygen. The reactor is charged with a catalyst that prioritizes the reaction of oxygen with oxygen,
The suction device, have a sorbent for reducing the content of impurities in the argon gas flowing out of the reactor,
An apparatus for purifying argon gas, wherein the catalyst contains platinum as a main component .

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