JPH1163813A - Method and device for recovering argon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable rectifying operation by suppressing a fluctuation of an amount of treated gas at a rectifying tower. SOLUTION: A part or all of high impurity argon from a rectifying tower 4 is fed back through a bypass line 8 to the inlet side of a raw material compressor 2 to boost raw material argon gas, and mixed with raw material argon gas. A bypass control valve 9 is located in the bypass line 8. Based on a signal from a pressure sensor 10 to detect the pressure of a holder 1 to which a raw material is introduced, the bypass control valve 9 is controlled by a controller 11 such that a total sum of an amount of feedback high impurity argon gas and an amount of raw material argon gas amount is kept at a constant value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recovering argon, which is used as an atmosphere gas in a single crystal manufacturing furnace for semiconductors and purifies and recovers argon gas containing impurities.

[0002]

2. Description of the Related Art Conventionally, a method disclosed in Japanese Patent Publication No. Hei 4-12393 has been known as a method for recovering impure argon gas.

In this known technique, after removing flammable components such as hydrocarbons from impure argon gas, the argon gas still containing impurities is cooled by a heat exchanger and then rectified (argon distillation column). Where it is separated from low-boiling components by cryogenic separation, and the resulting high-purity liquid argon is stored in a tank.

[0004]

However, this known technique has the following drawbacks.

In the case of a single crystal production furnace for semiconductors, the above-mentioned recovery device is shared by a plurality of furnaces, and an impure argon gas is supplied in each exhaust stroke (discontinuous) of each furnace with a slightly shifted timing. .

[0006] Therefore, the supply amount of the impure argon gas to the recovery device constantly fluctuates, and the amount of the processing gas in the rectification column also fluctuates. Therefore, it is difficult to control the rectification column according to this processing gas amount.
Stable operation becomes difficult.

[0007] As another problem, in the above-mentioned known technique, liquefied and separated high-purity argon is temporarily stored in a tank, extracted in a required amount from this tank, and the pressure is increased to a reusable pressure. It is supplied to a single crystal manufacturing furnace and the like.

[0008] Therefore, a pressurizing facility (compressor) is required at the tank outlet side, so that highly purified argon gas may be contaminated in the pressurizing facility during the pressurization.

[0009] As another problem, according to the above-mentioned known technique, a part of the impure argon gas supplied to the rectification column is taken into a reboiler in the rectification column as a heat source. Since the supply amount of the impure argon gas fluctuates, the fluctuation in the supply amount of the argon gas causes a shortage of the heat source of the reboiler, which also prevents stable operation of the rectification column.

Therefore, the present invention provides a method and an apparatus for recovering argon gas, which can perform a stable rectification operation while suppressing fluctuations in the amount of processing gas in a rectification column.

The present invention also provides a method and apparatus for recovering an argon gas which does not require high-pressure argon gas to be pressurized by a pressurizing facility when reused, and which does not cause gas contamination by the pressurizing operation. .

Further, the present invention provides a method and an apparatus for recovering argon gas capable of stably supplying a heat source of a reboiler of a rectification column.

[0013]

The invention according to claim 1 (method for recovering argon) is characterized in that an impurity argon gas as a raw material is
After being cooled by a heat exchanger through a purification process for removing predetermined impurities such as hydrocarbons, water, carbon dioxide, etc., the mixture is put into a rectification column, and the cryogenic separation action in the rectification column lowers the levels of hydrogen, nitrogen, etc. In the method for recovering argon, which is separated from the boiling point component and is highly purified, the required amount of the high-purity argon gas discharged from the rectification column is fed back to the raw material inlet side to be mixed with the raw material argon gas. .

According to a second aspect of the present invention, in the method of the first aspect, the raw argon gas is raised to a reusable pressure and then subjected to high purity treatment.

According to a third aspect of the present invention, in the method of the first or second aspect, nitrogen is circulated and supplied as a heat source for the reboiler in the rectification column and a cold heat source for the condenser.

The invention of claim 4 (Argon recovery apparatus)
A purifier that removes predetermined impurities such as hydrocarbons, water, and carbon dioxide from the impure argon gas as a raw material to be supplied, and a heat exchanger that cools the impure argon gas purified by the purifier, In an argon recovery apparatus provided with a rectification tower that obtains high-purity argon gas by separating low-boiling components such as hydrogen and nitrogen from the impure argon gas cooled by the heat exchanger by cryogenic separation, A branch line that is branched from a recovery line for recovering high-purity argon gas from the rectification column, and provided with a bypass line for feeding back the required amount of the high-purity argon gas to the raw material inlet side and mixing with the raw material argon gas It is.

According to a fifth aspect of the present invention, in the configuration of the fourth aspect, a bypass control valve for controlling a flow rate of the high-purity argon gas fed back by the bypass line, and a flow rate detection for detecting a flow rate of the introduced raw material argon gas. Means and a controller for controlling the flow rate of the bypass control valve in accordance with the amount of the raw material argon gas detected by the flow rate detecting means.

According to a sixth aspect of the present invention, in the configuration of the fourth or fifth aspect, a raw material compressor for increasing the pressure of the raw material argon gas to a reusable pressure is provided.

According to a seventh aspect of the present invention, in any one of the fourth to sixth aspects, a nitrogen circulating line for circulating and supplying nitrogen is provided as a heat source of the reboiler in the rectification column and a cold heat source of the condenser. It is.

According to the method and apparatus described above, a part or all of the high-purity argon gas discharged from the rectification column is fed back to the raw material inlet side. And a stable rectification operation can be performed.

In particular, according to the apparatus of claim 5, it is possible to automatically control the feedback amount of the high-purity argon gas in accordance with the amount of the raw material argon gas, thereby keeping the amount of the processing gas in the rectification column constant. Become.

According to the method of claim 2 and the apparatus of claim 6, since the raw gas is pre-pressurized to a reusable pressure and then subjected to the high-purity treatment, the high-purity argon discharged from the rectification column is obtained. The gas can be reused as it is (without increasing the pressure) in a single crystal manufacturing furnace for semiconductors or the like.

For this reason, there is no risk that the argon highly purified in the rectification column will be contaminated during the pressurization.

Furthermore, according to the method of claim 3 and the apparatus of claim 7, since the circulating nitrogen is used as the heat source of the reboiler and the cold source of the condenser, the heat source of the reboiler does not run short due to a change in the amount of the raw material gas. A stable rectification operation can be performed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

The raw material argon gas containing impurities used in a semiconductor single crystal manufacturing furnace or the like is first introduced into the holder 1 as a relay tank.

A raw material compressor 2 is provided downstream of the holder 1, and the raw material gas discharged from the holder 1 is sufficiently compressed by the raw material compressor 2 (for example, 6.5).
After being compressed to Kg / cm ² G), it enters the purification device 3.

In the purifying device 3, harmful impurities (hydrocarbon, water, carbon dioxide, oxygen, etc.) are removed from the impurities contained in the impure argon gas by the rectification column 4, which will be described later. For details, see, for example,
No.).

The argon gas, which still contains impurities, from the purifier 3 is passed through an argon heat exchanger 5 and cooled, and then introduced into the rectification column 4.

In the rectification column 4, low boiling components such as hydrogen and nitrogen in the impure argon gas are separated by cryogenic separation, and discharged as waste gas from the top of the column.

The high-purity argon gas from which impurities have been removed passes through a pipe 6 as a recovered gas and passes through an argon heat exchanger 5.
Heat exchanges with the impure argon gas in the inside to reach room temperature, and is used again as an atmosphere gas of a single crystal production furnace through the recovery line 7.

In this case, since the pressure of the argon gas has been raised to a reusable pressure by the raw material compressor 2 at the raw material stage as described above, there is no need to raise the pressure when reusing. For this reason, there is no possibility that the highly purified argon gas is contaminated in the pressurizing equipment.

On the other hand, a bypass line 8 is branched and connected to the recovery line 7, and a branch end of the bypass line 8 is connected to an inlet side of the raw material compressor 2.

The bypass line 8 is provided with a bypass control valve 9 for adjusting the feedback amount of the high-purity argon gas, and a pressure sensor 10 for detecting the pressure of the holder 1 (the inflow amount of the raw material argon gas). I have.

The signal from the pressure sensor 10 is input to a controller 11, which controls the opening of the bypass control valve 9 so that the sum of the raw material gas amount and the high-purity argon gas amount is always constant. You.

Here, the feedback amount of the high-purity argon gas is usually a part of the one coming out of the rectification column 4, but when the amount of the raw gas is insufficient, the whole amount of the high-purity argon gas is fed back. You.

Therefore, the collection amount control valve 1 is connected to the collection line 7.
2, the control valve 12 is closed by a signal from the controller 11 in the case of full amount feedback.

With this configuration, the processing gas amount in the rectification tower 4 is kept constant irrespective of the fluctuation of the raw material gas amount, and a stable rectification operation is performed.

The rectification column 4 is provided with a reboiler 13 for evaporating the liquefied argon gas to form an upward flow, and a condenser (condenser) 14 for producing a reflux liquid at the top of the column. Is provided.

In this argon recovery apparatus, circulating nitrogen is used as a heat source of the reboiler 13 and a cold heat source of the condenser 14.

That is, a circulating nitrogen compressor 15 is provided, and a nitrogen outgoing line 16 connected to an outlet of the compressor 15.
Is connected to the inlet end of the reboiler 13 via the argon heat exchanger 5, and the reboiler 13 and the condenser 1
4 is connected by a nitrogen pipe 18 having an expansion valve 17, and a nitrogen return line 19 connected to an outlet end of the condenser 14 is connected to a circulating nitrogen compressor 15 through an argon heat exchanger 5.
Connected to the entrance.

The rectification column 4 is pressurized (for example, 5.3 kg / c
m ² G, described below in this example)
About 16 kg / cm ² G nitrogen gas is used as a heat source for the reboiler 13, and about 6 kg / c as a cold heat source for the condenser 14.
It is necessary to supply m ² G of liquid nitrogen.

In the circulating nitrogen compressor 15, the pressure of the nitrogen gas is increased to about 16 kg / cm ² G, and the nitrogen gas is supplied to the reboiler 13 through the argon heat exchanger 5.

The liquid argon in the rectification column 4 is evaporated by the reboiler 13 to produce ascending argon gas necessary for rectification, and the nitrogen gas itself becomes liquid nitrogen.

The liquid nitrogen is supplied by the expansion valve 17 to about 6K.
g / cm ² G and supplied to the capacitor 14.

In the condenser 14, the reflux liquid necessary for rectification is produced by the heat exchange between the argon gas and liquid nitrogen in the rectification column 4, and the liquid nitrogen itself becomes nitrogen gas, which is impure in the argon heat exchanger 5. After the heat exchange with the argon gas, the process returns to the circulating nitrogen compressor 15.

As described above, by supplying both the heat source of the reboiler 13 necessary for rectification and the cold heat source of the condenser 14 by circulating nitrogen, as in the case of a known apparatus using impure argon gas as a heat source of the reboiler 13, There is no danger of a shortage of the heat source, and a more stable rectification operation and a high-purity argon gas can be recovered.

In the figure, reference numeral 20 denotes a liquid nitrogen line for cold supply.

In the above embodiment, the high-purity argon gas is fed back through the bypass line 8 so that the amount of the processing gas in the rectification tower 4 is always constant. , The feedback amount of the high-purity argon gas may be adjusted within a range in which the amount of the processing gas that enables stable operation in the rectification column 4 is maintained.

In the above embodiment, the pressure of the holder 1 is detected by the pressure sensor 10 as means for detecting the amount of the raw material argon gas. However, when a water seal holder is used as the holder 1, the liquid level is detected. You may make it.

[0051]

According to the present invention as described above, a part or all of the high-purity argon gas discharged from the rectification column is fed back to the raw material inlet side and mixed with the raw material argon gas. By appropriately adjusting the temperature, fluctuations in the amount of processing gas in the rectification column can be suppressed, and a stable rectification operation can be performed.

In particular, according to the invention of claim 5, it is possible to control the feedback amount of the high-purity argon gas in accordance with the amount of the raw material argon gas, and to keep the amount of the processing gas in the rectification column constant.

According to the second and sixth aspects of the present invention, since the high purity treatment is performed after the pressure of the raw material gas is increased to a reusable pressure in advance, the high purity argon gas discharged from the rectification column is used. It can be reused as it is (without increasing the pressure) in a single crystal manufacturing furnace for semiconductors and the like.

For this reason, there is no possibility that the argon highly purified in the rectification column will be contaminated by the pressurizing equipment.

Furthermore, according to the third and seventh aspects of the present invention, since the circulating nitrogen is used as a heat source for the reboiler and a cold source for the condenser, a shortage of the heat source of the reboiler due to fluctuations in the amount of the raw material gas does not occur, and the system is more stable. Rectification operation can be performed.

[Brief description of the drawings]

FIG. 1 is a flow sheet of an argon recovery device according to an embodiment of the present invention.

[Description of Signs] 2 Raw material compressor for raising the raw material argon gas to a reusable pressure 3 Purifier for removing impurities 5 Heat exchanger 4 Rectifier 13 Refractor for rectifier 14 Condenser for rectifier 15 Circulation Nitrogen compressor 16 Nitrogen feed line for supplying circulating nitrogen to reboiler 18 Nitrogen pipe connecting reboiler and condenser 19 Nitrogen return line for returning circulating nitrogen from condenser to compressor 7 Argon recovery line 8 Bypass line 9 Provided in bypass line Bypass control valve 11 Controller for controlling bypass control valve 10 Pressure sensor as means for detecting flow rate of raw material argon gas

Claims (7)

[Claims] Claims 1. An impure argon gas as a raw material is cooled by a heat exchanger through a purification step for removing predetermined impurities such as hydrocarbons, water, and carbon dioxide, and then is introduced into a rectification column.
In the method of recovering argon, which is separated from low-boiling components such as hydrogen and nitrogen by the cryogenic separation action in the rectification column and is highly purified and recovered, the required amount of the high-purity argon gas discharged from the rectification column is reduced. A method for recovering argon, wherein the raw material is fed back to the raw material inlet side and mixed with the raw material argon gas. 2. The method for recovering argon according to claim 1, wherein the raw material argon gas is raised to a reusable pressure and then subjected to high purity treatment. 3. The method for recovering argon according to claim 1, wherein nitrogen is circulated and supplied as a heat source of the reboiler in the rectification column and a cold heat source of the condenser. 4. A purifier for removing predetermined impurities such as hydrocarbons, water and carbon dioxide from impure argon gas as a raw material to be supplied, and a heat exchange for cooling the impure argon gas purified by the purifier. And a rectification column for obtaining high-purity argon gas by separating low boiling components such as hydrogen and nitrogen from the impure argon gas cooled by the heat exchanger by cryogenic separation. A bypass line is provided which branches off from a recovery line for recovering the high-purity argon gas discharged from the rectification column and feeds a required amount of the high-purity argon gas back to the raw material inlet side to mix with the raw argon gas. An argon recovery device, characterized in that: 5. The argon recovery device according to claim 4, wherein a bypass control valve for controlling a flow rate of the high-purity argon gas fed back by the bypass line;
Flow rate detection means for detecting the flow rate of the raw material argon gas introduced, and a controller for controlling the flow rate of the bypass control valve according to the raw material argon gas amount detected by the flow rate detection means are provided. Argon recovery device. 6. The argon recovery apparatus according to claim 4, further comprising a raw material compressor for raising the raw material argon gas pressure to a reusable pressure. 7. The argon recovery apparatus according to claim 4, wherein a nitrogen circulation line for circulating and supplying nitrogen is provided as a heat source for the reboiler in the rectification column and a cold heat source for the condenser. A recovery device for argon.