JPH1111915A - Recovery of argon and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To refine exhaust gas from a single crystal production furnace, to efficiently recover argon having a high purity and to allow to follow to even reduction of a generating exhaust gas volume. SOLUTION: The exhaust gas is compressed and also solids such as powder and dust and an oil component are removed, more excessive quantity of hydrogen than a stoichiometric quantity required to a reaction of oxygen in the exhaust gas is added to convert oxygen with a catalystic reaction into water. Water and carbon dioxide are absorbed and removed and impurities having lower boiling points than argon are separated by a fractional separation to recover argon having a high purity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recovering argon, and more particularly, to argon discharged from a single crystal manufacturing furnace for manufacturing a single crystal such as a silicon single crystal used as a base material of a semiconductor. The present invention relates to a method and an apparatus for recovering argon, which recovers high-purity argon from exhaust gas containing as a main component.

[0002]

2. Description of the Related Art Since argon gas has an inert property, it is widely used in various industrial fields as a shielding gas for welding or an atmosphere gas for heat treatment of metals. In recent years, in a single crystal manufacturing furnace for manufacturing a single crystal such as a silicon single crystal used as a semiconductor substrate material, high-purity (99.999% by volume) argon has been used to obtain a high-quality single crystal. Gas is used as furnace atmosphere gas. Therefore, an exhaust gas containing argon as a main component is discharged from such a single crystal production furnace, and the composition of the exhaust gas is such that 99 to 99.9% by volume of argon is used as an atmosphere gas of the furnace. As a result, not only are dusts such as silicon oxide, silicon dioxide and carbon mixed in and entrained, but also various components such as oil, moisture, carbon monoxide, carbon dioxide, oxygen, hydrogen and nitrogen are trace amounts of impurities. Yes, but in a mixed state.

Various methods for recovering and reusing argon from exhaust gas of such components have been proposed in the past, for example, Japanese Patent Application Laid-Open Nos. 63-189774, 1-230975 and 1-230975. JP-A-2-272288, JP-A-2-282682, JP-A-3-398
No. 86, Japanese Patent Publication No. 4-123393, Japanese Patent Publication 5-
No. 29834, JP-A-5-256570, JP-A-9-72656 and the like.

[0004]

However, in the conventional method, it is difficult to efficiently remove various types of impurities as described above, and it has not been sufficient yet. Also, little consideration was given to fluctuations in the amount of waste gas. Therefore, the appearance of a method capable of efficiently and economically recovering argon has been desired.

[0005] Accordingly, the present invention provides a method comprising:
Purification of exhaust gas from a single crystal manufacturing furnace containing various impurity components such as dust, oil, water, carbon monoxide, carbon dioxide, oxygen, hydrogen, nitrogen, and hydrocarbons to efficiently recover high-purity argon. It is an object of the present invention to provide a method and apparatus for recovering argon, which can follow the reduction of the amount of generated exhaust gas.

[0006]

In order to achieve the above object, a method for recovering argon according to the present invention comprises argon as a main component and impurities such as dust, oil, water, carbon monoxide, carbon dioxide, oxygen, hydrogen, A method for recovering argon in exhaust gas from a single crystal production furnace containing nitrogen and the like, wherein the step of compressing the exhaust gas and removing solids and oil such as dust and the reaction of oxygen in the exhaust gas The process of adding oxygen in excess of the required stoichiometric amount to convert oxygen to water by a catalytic reaction, the process of adsorbing and removing water and carbon dioxide, and the separation of impurities with a boiling point lower than that of argon by rectification And recovering argon.

Further, the method for recovering argon according to the present invention comprises:
In performing the rectification and separation in a cryogenic separation device provided with a rectification column and a condenser, the argon gas separated and generated in the rectification column is extracted by controlling the gas at a constant pressure, and is introduced into the rectification column. The gas in which the separated low-boiling-point impurities are concentrated is controlled and extracted to a constant purity, or the temperature of the outlet of the low-boiling-point impurities concentrated gas from the rectification column is controlled and extracted to a constant temperature, and the condenser is extracted. The cooling liquid to be injected into the rectifying cylinder is controlled so that the liquid level at the bottom of the rectifying cylinder is constant, and the cooling gas vaporized by the condenser is discharged while controlling the liquid level of the condenser. Characterized in that at least a part of the argon gas recovered by the rectification separation, or at least a part of the low-boiling-point impurity-enriched gas separated by the rectification separation, is returned to the exhaust gas before compression to be combined. Features.

The apparatus for recovering argon according to the present invention is characterized in that an exhaust gas from a single crystal manufacturing furnace containing argon as a main component and containing dust, oil, moisture, carbon monoxide, carbon dioxide, oxygen, hydrogen, nitrogen and the like as impurities. A device for collecting argon, a dust collecting means for removing solids such as the dust, a compressing means for compressing exhaust gas to a required pressure, an oil removing means for removing oil, and an oxygen removing means for adding hydrogen. Reaction means for converting water into water by a catalytic reaction, adsorption means for adsorbing and removing moisture and carbon dioxide, and liquefaction rectification of exhaust gas containing residual impurities to separate impurities having lower boiling point than argon into argon A cryogenic separation means, and a recovery argon supply path for recovering the argon separated by the cryogenic separation means and supplying the recovered argon to the single crystal production furnace, and the rectification cylinder has an exhaust gas introduction path connected to a middle stage of the cylinder. A condenser for introducing an external chilled liquid at the upper part to generate a reflux liquid, a low-boiling-point impurity-enriched gas deriving path for deriving the low-boiling-point impurity gas from the condenser, and an argon gas from the lower part of the cylinder. And an argon derivation path for derivation.

Further, the argon recovery apparatus of the present invention
Argon pressure control means for controlling the degree of opening of an argon discharge valve provided in the path based on a signal from a pressure detection means provided in the argon gas discharge path, and identification of a gas provided in the low boiling point impurity-enriched gas discharge path. Low-boiling-point impurity-enriched-gas purity control means for controlling the degree of opening of a low-boiling-point impurity deriving valve provided in the path based on a signal from the analyzing means for detecting the component of A low-boiling-point impurity-concentrated gas temperature control means for controlling the degree of opening of a low-boiling-point impurity outlet valve provided in the path by a signal from A rectifying cylinder liquid level control means for controlling the opening of an external chilled liquid introduction valve provided in a path for introducing an external chilled liquid, and a signal from the chilled liquid level measuring means provided for the condenser, and Vaporized cold gas Condenser level control means for controlling the degree of opening of the vaporized gas discharge valve provided in the path for deriving the exhaust gas, the recovered argon supply path, and the exhaust gas upstream of the compression means. An argon return path for returning argon from the recovered argon supply path to the exhaust gas path between the recovery argon supply path and the low-boiling-point impurity-enriched gas lead-out path and an exhaust gas path upstream of the compression means. A low-boiling-point impurity return path for returning a low-boiling-point impurity-enriched gas from a boiling-point impurity-enriched gas lead-out path to an exhaust gas path is provided.

[0010]

FIG. 1 is a system diagram showing one embodiment of the present invention. This argon recovery apparatus is for processing argon-containing exhaust gas discharged from a single crystal manufacturing furnace 1, for example, a silicon single crystal manufacturing furnace, to recover argon with high purity, and includes solid components such as dust in the exhaust gas. A dust collector 2 as dust collecting means for removing oil, a compressor 3 as compression means for compressing exhaust gas to a required pressure, an oil removing cylinder 4 and an oil filter 5 as oil removing means for removing oil. A hydrogen introduction path 6 and a catalyst tube 7 which are catalytic reaction means for adding hydrogen to the exhaust gas to convert oxygen to water by a catalytic reaction, and an adsorbent such as zeolite which is an adsorption means for adsorbing and removing water and carbon dioxide. The apparatus is provided with a packed adsorption column 8 and a rectification column 9 as cryogenic separation means for separating and removing impurities having a boiling point lower than that of argon by liquefaction rectification.

Exhaust gas from the single crystal production furnace 1, for example, 150 mg / Nm ^{3 of} solid dust, 200 ppm by volume of hydrogen, 100 ppm by volume of oxygen, 2000 ppm by volume of carbon monoxide,
100 ppm by volume of carbon dioxide, 400 ppm by volume of nitrogen,
Exhaust gas 300 Nm ³ / h containing impurities consisting of an oil content of 10 ppm by volume and a saturated amount of water is supplied to a blower 11 provided as required depending on the operating pressure of the single crystal production furnace 1.
After the pressure is increased to about mmAq, it is stored in the gas holder 13 via the conduit 12. The exhaust gas in the gas holder 13 is
The dust is introduced into the dust collector 2 by the conduit 14, and solid dust such as silicon oxide, silicon dioxide, and carbon contained in the exhaust gas is removed, and the dust is led to the conduit 15.

Next, the exhaust gas is compressed by the compressor 3 to a pressure of a product (high-purity argon) or a pressure necessary for processing in the subsequent steps. For example, to obtain a product of 5 kg / cm ² G, the exhaust gas is compressed to 6.5 kg / cm ² G.

The compressed exhaust gas is supplied to the aftercooler 1
6, the oil is introduced into the oil removal cylinder 4 through the conduit 17, and oil is removed by activated carbon or the like filled in the cylinder.
The oil is introduced into the oil filter 5 to remove the oil. In addition, only one of the oil removing cylinder 4 and the oil filter 5 may be provided according to the situation of the oil component in the exhaust gas.

The exhaust gas from which dust and oil have been removed is heated from a conduit 18 through a heat exchanger 19 for preheating and a heater 20 to a predetermined temperature, for example, 100 to 350 ° C., and is led out to a conduit 21 to be introduced into a hydrogen introduction path 6. Mixed with the hydrogen added from the conduit 22 of the above, and introduced into the catalyst tube 7. The catalyst tube 7 is filled with a catalyst such as palladium or platinum, and the reaction between oxygen and hydrogen in the exhaust gas introduced into the catalyst tube 7 is promoted,
The oxygen content is removed from the exhaust gas by converting the oxygen content into water.

The amount of hydrogen introduced and added from the hydrogen introduction path 6 is included in the exhaust gas so as to be an excess of the stoichiometric amount required for converting oxygen in the exhaust gas flowing through the conduit 18 into water. It is determined in consideration of the oxygen content and the hydrogen content. For example, an oximeter (QOI) 23
And a flow meter (FI) 24 for measuring the amount of oxygen in the exhaust gas heading toward the catalyst cylinder 7, and a hydrogen concentration meter (QHI) 26 for providing a hydrogen concentration meter (QHI) 26 to the conduit 25 from which the catalyst cylinder 7 is led out. The hydrogen flow controller (FIC) 2 provided in the hydrogen introduction path 6 according to the measured oxygen amount and hydrogen amount
By adjusting the opening degree of the valve 27a with 7, an appropriate amount of hydrogen can be added, and the oxygen content in the exhaust gas can be effectively removed.

The exhaust gas from which oxygen has been removed by converting oxygen into water in the catalyst tube 7 is recovered in a preheat heat exchanger 19 and led out to a conduit 25, which is then cooled by a cooling device 28 to about 10 ° C.
After being cooled down, it is introduced into the adsorption column 8. The cooling device 28 is provided to improve the efficiency of adsorption in the adsorption column 8 by cooling the exhaust gas and to reduce the size of the adsorption column 8, but may be omitted depending on the situation. .

The plurality of adsorption cylinders 8 sequentially switch between an adsorption step of adsorbing and removing moisture and carbon dioxide by an adsorbent filled therein and a regeneration step of desorbing moisture and carbon dioxide adsorbed by the adsorbent. The switching between the adsorption step and the regeneration step is performed by opening and closing a switching valve provided before and after the adsorption cylinder 8 in a predetermined order.

The inside of the adsorption column 8 is filled with zeolite or the like as an adsorbent for adsorbing and removing moisture and carbon dioxide. By passing the exhaust gas through the adsorption column 8, the moisture and carbon dioxide in the exhaust gas are adsorbed and removed. Is done.

In the adsorption cylinder regeneration step, a regeneration gas, for example, nitrogen gas introduced from a conduit 29 is heated by a regeneration heater 30 and introduced into the adsorption cylinder 8 to desorb moisture and carbon dioxide from the adsorbent. Then, the operation of stopping the regenerative heater 30 and cooling the adsorbent is performed. In addition, as the regeneration gas, a part of the exhaust gas after the adsorption process was used, as shown in FIG.
Can be used by branching to a conduit 29a indicated by a broken line.

As described above, the exhaust gas led to the conduit 31 through the dust collector 2, the oil removing cylinder 4, the oil filter 5, the catalyst cylinder 7, and the adsorption cylinder 8 has argon as a main component and has a boiling point lower than that of argon. 2000 vol ppm of carbon monoxide as a component,
It contains 400 ppm by volume of nitrogen and 300 ppm by volume of excess hydrogen that has not reacted in the catalyst tube 7, and is introduced into a cold box 32 equipped with a rectification tube 9 in order to separate and remove these low-boiling components from argon. Is done.

In the cold box 32, in addition to the rectification cylinder 9, a main heat exchanger 33, a subcooler 34, a condenser 35, a reboiler 36 and the like necessary for performing liquefaction rectification are provided. Various control devices for efficiently obtaining argon with high purity are provided.

The exhaust gas flowing from the conduit 31 into the cold box 32 is cooled to a predetermined temperature by exchanging heat with a return gas such as high-purity argon or the like in a main heat exchanger 33, and is rectified through a conduit 37. The tube 9 is introduced into the middle stage. The gas introduced into the rectification cylinder 9 is rectified by gas-liquid contact between the gas rising from the reboiler 36 at the bottom of the cylinder and the liquid flowing down from the condenser 35 at the top of the cylinder, and is purified by high-purity argon at the bottom of the cylinder. It is separated from the gas containing low-boiling components at the top of the cylinder.

As the heating source for the reboiler 36 and the cooling source for the condenser 35, nitrogen circulated by being circulated by the circulating compressor 38 is used. 15.5 kg /
The nitrogen gas 1200 Nm ³ / h compressed to cm ² G is
After being introduced into the cold box 32 from the conduit 39 and being exchanged with the return gas in the main heat exchanger 33 to be cooled to a predetermined temperature, it is introduced into the reboiler 36. Reboiler 3
The nitrogen gas introduced into 6 performs heat exchange with the cylinder bottom liquid, evaporates the cylinder bottom liquid to generate a rising gas, and itself condenses to liquefied nitrogen.

The liquefied nitrogen generated by the reboiler 36 is led out to a conduit 40 and further cooled by a supercooler 34,
The pressure is reduced to 8 kg / cm ² G by 1 and introduced into the condenser 35. Further, liquefied nitrogen 10 Nm ³ / h for supplementing the cold is introduced into the condenser 35 from the conduit 42. Condenser 35
The liquefied nitrogen introduced into the tube condenses the gas at the top of the cylinder to generate a falling liquid, and itself evaporates to become nitrogen gas again. This nitrogen gas is led from the condenser 35 to the conduit 43 and passes through the subcooler 34 and the conduit 44 to the main heat exchanger 33.
, And is drawn out of the cold box 32 by a conduit 45, and is sucked into the circulating compressor 38 through a conduit 46 and circulated. The surplus nitrogen gas is discharged from the valve 47, and the insufficient nitrogen gas at the time of starting is supplied from the valve 48.

From the lower part of the rectification column 9, 295 Nm ³ / h of high-purity argon gas separated by the rectification is extracted to a conduit 49, and the temperature is increased in the main heat exchanger 33 to a conduit 50.
, And collected through a conduit 51 and a valve 52, and supplied as high-purity argon gas (PAr). From the condenser 35, a gas 5 Nm ³ / h in which the low-boiling-point impurity component is concentrated is extracted to the conduit 53, and is discharged through the main heat exchanger 33, the conduit 54, the conduit 55, and the valve 56. The composition of the low-boiling-point impurity concentrated gas released is, for example, 83.8% argon.
%, Nitrogen 2.4%, hydrogen 1.8%, carbon monoxide 12.0
%.

The present invention basically purifies and recovers argon as described above. However, in the single crystal production furnace 1, the amount of argon gas used as an atmospheric gas varies depending on the operation state of the furnace. May be. in this case,
The flow rate and the impurity concentration of the exhaust gas discharged from the single crystal manufacturing furnace 1 change. Even in such a case, it is necessary to continue the argon recovery operation in a stable state.

For this reason, as described above, in the catalyst tube 7 for removing oxygen in the exhaust gas, the amount of oxygen in the exhaust gas is measured by the oxygen concentration meter 23 and the flow meter 24 to adjust the flow rate of the hydrogen introduction path 6. The mechanism 27 is controlled, and the catalyst cylinder 7
The hydrogen concentration in the gas derived from the above is measured by the hydrogen concentration meter 26 to correct the flow rate adjusting mechanism 27. Therefore, even if the amount of oxygen in the exhaust gas fluctuates, the amount of hydrogen can be reliably increased and decreased, and the fluctuation of the amount of hydrogen originally contained in the exhaust gas can be followed. While removing, the amount of added hydrogen can be minimized.

On the other hand, in the cryogenic separation means, the conduit 50
Pressure controller (PIC) 57 and a valve 57a for controlling the pressure of the high-purity argon gas derived from the gas at a constant level, and for controlling the purity of specific components in the low-boiling-point impurity-enriched gas derived from the conduit 54 at a constant level. Purity Controller (QIC) 5
8 and a valve 58a, a liquid level controller (LIC) 59 and a valve 59a for adjusting the amount of liquefied nitrogen introduced from the conduit 42 in order to constantly control the liquid level of the bottom liquid of the rectification column 9, and a condenser 3
5 for controlling the liquid level controller (LIC) 60 and the valve 60a for controlling the amount of nitrogen gas led out to the conduit 43 from 5 and the valve 41 for reducing the pressure of the liquefied nitrogen cooled by the subcooler 34. Pressure controller (PIC) 61 is provided. The specific component whose purity is to be measured by the purity controller 58 is usually argon, which accounts for most of the low-boiling-point impurity-enriched gas.

By providing such various controllers and operating the rectification cylinder 9 under a constant condition, high-purity argon can be recovered at a predetermined purity even when the amount of exhaust gas is reduced. For example, if the amount of gas introduced into the rectification cylinder 9 decreases due to a decrease in the amount of exhaust gas, the pressure in the rectification cylinder 9 will decrease. Here, the pressure controller 57 operates to operate the valve 57.
By reducing a, the amount of gas (high-purity argon) derived from the rectification cylinder 9 decreases, and the inside of the rectification cylinder 9 is maintained at a constant pressure. At the same time, if the amount of the low-boiling-point impurity-concentrated gas withdrawn remains constant, the purity of argon in the gas increases. The purity controller 58 detects this, and the valve 58a is throttled so that the argon purity is constant. . As a result, the rectification cylinder 9 automatically enters the reduced operation state. Further, when the liquid level of the bottom of the cylinder or the condenser 35 fluctuates due to the reduction operation, the liquid level controllers 59 and 60 operate to automatically adjust the liquid level to a constant level.

In place of the purity controller 58 of the conduit 54, a temperature controller for controlling the temperature of the low-boiling-point impurity component-containing gas derived from the rectification column 9 (condenser 35) to the conduit 53 is provided. The valve 58a may be controlled so as to be constant. Similarly, the valve 41 can be controlled by a flow controller instead of the pressure controller 61.

Although it is possible to reduce the amount to some extent by the above-described control, if the amount is reduced to 30% or less, the controllability may be deteriorated depending on the sizing of the control valve. Depending on the capacity and type of the machine 3, there is a case where the power hardly decreases due to the weight reduction, and such a case is dealt with by the following means.

That is, when the amount of exhaust gas from the single crystal production furnace 1 is reduced, a part of the argon gas is branched from the conduit 51 through which the high-purity argon gas flows to the circulation conduit 62 and is diverted to the suction side of the compressor 3. The gas is returned to the conduit 15, or a part of the gas from the conduit 54 through which the low-boiling-point impurity-enriched gas flows is branched into the circulation conduit 63 and returned to the conduit 15 on the suction side of the compressor 3. At this time, the gas circulated back to the suction side of the compressor 3 can be arbitrarily selected from one or both of a high-purity argon gas and a low-boiling-point impurity-enriched gas in accordance with the reduction width of the exhaust gas. When the loss width is relatively small, it is preferable to give priority to high-purity argon gas. The amount of gas circulated through each of the circulation conduits 62 and 63 can be controlled by adjusting the opening of the valves 52 and 56 and the valves 64 and 65 provided in the circulation conduits 62 and 63, respectively. Can be performed automatically in accordance with the amount of exhaust gas.

Further, even when the exhaust gas is no longer discharged from the single crystal production furnace 1, the rectification column 9 is fully refluxed by returning and circulating all of the high-purity argon gas and the low-boiling-point impurity-enriched gas. Since it can be maintained, the next time the exhaust gas increases, it can be automatically recovered without deteriorating the purity of the recovered argon.

By circulating the gas derived from the rectification cylinder 9 through the compressor 3 in this manner, the rectification can be performed without increasing the load on the oil removal cylinder 4, the oil filter 5, the catalyst cylinder 7, and the adsorption cylinder 8. Since the amount of gas introduced into the cylinder 9 can be secured to a certain amount or more, the controllability does not deteriorate, and even when the amount of exhaust gas is greatly reduced, a stable operation state is automatically continued. Can be.

[0035]

As described above, according to the method and apparatus for recovering argon of the present invention, argon can be efficiently recovered from gas discharged from a single crystal manufacturing furnace. In particular, by operating the rectification column for separating low-boiling impurities under constant conditions, even when the amount of exhaust gas is reduced, argon of a predetermined purity can be obtained, and an increase in the amount of released argon can be suppressed. Further, by circulating the rectified gas back to the compressor suction side, stable operation can be continued even when the amount of exhaust gas is significantly reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Single crystal manufacturing furnace, 2 ... Dust collector, 3 ... Compressor, 4 ... Oil removal cylinder, 5 ... Oil filter, 6 ... Hydrogen introduction path, 7 ... Catalyst cylinder, 8 ... Adsorption cylinder, 9 ... Rectification cylinder , 11 ... blower, 13 ...
Gas holder, 16 aftercooler, 19 heat exchanger for preheating, 20 heater, 23 oxygen concentration meter, 24 flow meter, 26 hydrogen concentration meter, 27 hydrogen flow controller, 28
... cooling device, 32 ... cold box, 33 ... main heat exchanger, 34 ... subcooler, 35 ... condenser, 36 ... reboiler,
38: circulation compressor, 57: pressure controller, 58: purity controller, 59: liquid level controller, 60: liquid level controller, 61: pressure controller, 62, 63: circulation conduit

Claims (9)

[Claims] 1. A method for recovering argon in an exhaust gas from a single crystal production furnace containing argon as a main component and containing dust, oil, moisture, carbon monoxide, carbon dioxide, oxygen, hydrogen, nitrogen and the like as impurities. A step of compressing the exhaust gas and removing solids and oils such as dust, and adding a hydrogen in excess of a stoichiometric amount necessary for a reaction of oxygen in the exhaust gas to convert oxygen into a catalytic reaction. Converting to water,
A method for recovering argon, comprising: a step of adsorbing and removing water and carbon dioxide; and a step of recovering argon by separating impurities having a lower boiling point than argon by rectification separation. 2. When performing the rectification separation by a cryogenic separation device provided with a rectification column and a condenser, the argon gas separated and generated in the rectification column is controlled and extracted at a constant pressure, The low-boiling-point impurities separated in the rectifying column may be extracted by controlling the concentration of the gas having a low boiling point concentration to a constant purity, or the temperature of the outlet of the low-boiling-point impurity concentrated gas from the rectifying column may be controlled to a constant temperature. Withdrawing and injecting the cooling liquid to be injected into the condenser while controlling the liquid level at the bottom of the rectifying cylinder at a constant level, and controlling the liquid level of the condenser at a constant level with the cooling gas vaporized by the condenser. 2. The method for recovering argon according to claim 1, wherein the argon is extracted. 3. The method for recovering argon according to claim 1, wherein at least a part of the argon gas recovered by the rectification separation is returned to the exhaust gas before compression and merged. 4. The method for recovering argon according to claim 1, wherein at least a part of the low-boiling-point impurity-enriched gas separated by the rectification separation is returned to the uncompressed exhaust gas and joined. 5. An apparatus for recovering argon in an exhaust gas from a single crystal production furnace containing argon as a main component and containing dust, oil, moisture, carbon monoxide, carbon dioxide, oxygen, hydrogen, nitrogen, etc. as impurities. Dust collecting means for removing solids such as dust, compression means for compressing exhaust gas to a required pressure, oil removing means for removing oil, and adding hydrogen to convert oxygen to water by a catalytic reaction. A catalytic reaction means, an adsorption means for adsorbing and removing moisture and carbon dioxide, a cryogenic separation means for liquefying and liquefying an exhaust gas containing residual impurities to separate impurities and argon having a boiling point lower than argon, and A recovery argon supply path for recovering the argon separated by the cryogenic separation means and supplying the recovered argon to the single crystal production furnace, wherein the rectification cylinder has an exhaust gas introduction path connected to the middle stage of the cylinder, and an external cooling liquid Introduce A low-boiling-point impurity-enriched gas deriving path for deriving the low-boiling-point impurity gas from the condenser, and an argon deriving path for deriving argon gas from the lower part of the cylinder. An argon recovery device, characterized in that: 6. An argon pressure control means for controlling an opening degree of an argon discharge valve provided on the argon gas discharge path based on a signal from a pressure detection means provided on the path, and an argon pressure control means provided on the low boiling point impurity concentrated gas discharge path. Low-boiling-point impurity-enriched gas purity control means for controlling the degree of opening of a low-boiling-point impurity outlet valve provided in the path with a signal from an analyzing means for detecting a specific component in the gas, and provided at the bottom of the rectification column. A rectifying cylinder liquid level control means for controlling an opening of an external chilled liquid introduction valve provided in a path for introducing an external chilled liquid into the condenser by a signal from the liquid level measuring means, and a chiller provided in the condenser. And a condenser liquid level control means for controlling an opening of a vaporized gas derivation valve provided in a path for deriving the cooling gas vaporized in the condenser by a signal from the liquid level measurement means. The argon recovery device according to claim 5. 7. An opening degree of a low boiling point impurity derivation valve provided in a low boiling point impurity concentrated gas deriving path provided by a signal from a temperature detecting means provided in the low boiling point impurity concentrated gas deriving path instead of the low boiling point impurity concentrated gas purity controlling means. 7. The argon recovery apparatus according to claim 6, further comprising a low-boiling-point impurity-concentrated gas temperature control means for controlling. 8. An argon return path for returning argon from the recovered argon supply path to the exhaust gas path is provided between the recovered argon supply path and an exhaust gas path upstream of the compression means. 6. The argon recovery device according to 5. 9. The low-boiling-point impurity-enriched gas deriving path,
6. A low-boiling-point impurity return path for returning a low-boiling-point impurity-enriched gas from a low-boiling-point impurity-enriched gas lead-out path to an exhaust gas path between the exhaust-gas path and the exhaust gas path on the upstream side of the compression means. Argon recovery device.