JP6195753B2 - Inert gas pre-treatment facility - Google Patents

Description

  The present invention relates to a facility for performing a pretreatment for recovering and reusing an inert gas discharged from a silicon single crystal pulling apparatus.

  When producing a silicon single crystal by the Czochralski method (CZ method), a single crystal pulling device is used, and the seed crystal is silicon in the crucible in the single crystal pulling device in an inert gas atmosphere such as argon gas. A single crystal is grown by pulling it in contact with the melt while rotating. In recent years, as the production scale of silicon single crystals has expanded, the amount of inert gas used has also increased, and it is possible to recover and reuse the inert gas discharged from the silicon single crystal manufacturing equipment in order to reduce costs. It is an important issue.

  The inert gas discharged from the silicon single crystal production apparatus includes impurities such as silicon oxide generated in the single crystal production apparatus. For this reason, in order to recover and purify the inert gas, it is necessary to perform a pretreatment for removing impurities such as silicon oxide contained in the discharged inert gas. The silicon oxide contained in the inert gas is in the form of particles of several microns to several tens of microns. Generally, wet processing is performed as a method for removing such silicon oxide.

JP 2011-51872 A

As an example of the above-described wet treatment, Patent Document 1 discloses an apparatus that can dissolve and remove silicon oxide by a stirring effect with a strong alkaline solution such as a caustic soda solution.
FIG. 5 is a schematic view showing an example of an inert gas recovery pretreatment facility of Patent Document 1. In the facility of FIG. 5, the inert gas discharged from the silicon single crystal manufacturing apparatus 1 is stirred with the strong alkali solution 7 by the Nash pump 60 or the static mixer 50, and the silicon oxide in the inert gas is converted into the strong alkali solution. Dissolve in 7 and remove.
In Patent Document 1, there is a description that silicon oxide can be effectively removed by processing with a system combining two or more of a scrubber, a mixer, an ejector, and a Nash pump as a means of stirring. Moreover, in the apparatus of patent document 1, the alkaline solution of the temperature higher than normal temperature (50 degreeC or more) is used in order to make reaction with a silicon oxide quick.

  However, when silicon oxide is dissolved and removed with such equipment, a mist containing an alkali component derived from the strong alkali solution used for removing the silicon oxide (hereinafter, alkali mist) is accompanied by the inert gas. If this alkali mist remains, it will cause a great hindrance in the recovery and purification process and reuse of the inert gas in the subsequent process. Therefore, it is necessary to completely remove the alkali mist contained in the inert gas after removing the silicon oxide. There is.

Therefore, in the facility of FIG. 5, after removing the silicon oxide, the water scrubber 9 neutralizes the alkali mist accompanying the inert gas.
In Patent Document 1, an acid scrubber that performs neutralization with an acid solution is listed as a neutralization means in addition to a water scrubber, but the use of an acid scrubber may cause corrosion or contamination in the subsequent process. There is.

  Thus, although the conventional equipment can remove the silicon oxide in the inert gas, the scrubber system alone cannot completely remove the alkali mist in the inert gas. This is because the alkali mist is actually in the form of mist or fume having a particle size of submicron level, and gas-liquid contact is not efficiently performed in a packed tower type scrubber or the like.

  The present invention has been made to solve the above-described problems. After the silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus is sufficiently removed and the silicon oxide is removed. An object of the present invention is to provide an inert gas recovery pretreatment facility capable of effectively removing mist containing an alkali component in the inert gas.

In order to solve the above problems, in the present invention,
A recovery pretreatment facility for inert gas discharged from a silicon single crystal manufacturing apparatus,
Means for dissolving and removing silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus by contacting it with a strong alkali solution; and alkali in the inert gas after removing the silicon oxide Provided is an inert gas recovery pretreatment facility having means for removing a mist containing components using a demister.

  With the inert gas recovery pretreatment facility of the present invention, the silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus can be sufficiently removed, and the inert gas after the silicon oxide is removed Mist containing the alkali component therein can also be effectively removed.

  Further, the means for dissolving and removing the silicon oxide by bringing it into contact with a strong alkaline solution is one of a liquid ring compressor, an ejector, a static mixer and a Nash pump, or a combination of two or more. Preferably there is.

  If this is the case, it is possible to efficiently contact the silicon oxide in the strong alkali solution and the inert gas to promote the dissolution of the silicon oxide, so that the silicon oxide can be removed more reliably. Can do.

  At this time, the demister is preferably installed in a gas-liquid separation tower in which the strong alkali solution circulates.

  As described above, by installing the demister in the gas-liquid separation tower, it is possible to more effectively remove the mist containing the alkali component in the inert gas after removing the silicon oxide.

  At this time, it is preferable that the demister is installed either before or after the washing scrubber that neutralizes the mist containing the alkali component.

  By doing in this way, the mist containing the alkali component in the inert gas after removing silicon oxide can be removed more effectively.

  At this time, the demister is preferably a candle demister.

  By setting it as such a demister, the fine submicron size alkali mist which is carrying out Brownian motion can be removed.

  Moreover, it is preferable to remove moisture with a cooling condenser after removing the alkali component with the demister.

  Thereby, since saturated mist can be cooled and dehumidified below the normal dew point temperature, the burden at the time of the collection | recovery and refinement | purification of the inert gas of a post process can be reduced.

  At this time, the strong alkali solution is preferably a caustic soda solution.

  Thus, a caustic soda solution is inexpensive and can be implemented at low cost.

  According to the present invention, the silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus can be sufficiently removed, and the mist containing the alkali component in the inert gas after removing the silicon oxide is also effective. Therefore, it is possible to stably carry out the recovery and purification of the inert gas in the subsequent step. Further, by performing dehumidification after removing the alkali mist, it is possible to reduce the burden at the time of recovery and purification of the inert gas in the subsequent step. Moreover, phosphorus and boron which are concerned when the recovered and purified gas is reused can be removed at the same time.

It is the schematic which shows an example of the collection | recovery pre-processing equipment of the inert gas of this invention. It is the schematic which shows another example of the collection | recovery pre-processing equipment of the inert gas of this invention. It is the schematic which shows another example of the collection | recovery pre-processing equipment of the inert gas of this invention. It is the schematic which shows another example of the collection | recovery pre-processing equipment of the inert gas of this invention. It is the schematic which shows an example of the collection | recovery pretreatment equipment of the inert gas of patent documents 1. It is the schematic which shows an example of the ejector which can be used with the collection | recovery pre-processing equipment of the inert gas of this invention. It is the schematic which shows an example of the static mixer which can be used with the collection | recovery pre-processing equipment of the inert gas of this invention. It is the schematic which shows an example of the Nash pump which can be used with the collection | recovery pre-processing equipment of the inert gas of this invention.

  As described above, recovery of the inert gas that can remove the silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus and also remove the alkali mist in the inert gas after removing the silicon oxide. The development of pretreatment equipment was required.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have removed the silicon oxide using a strong alkaline solution and then removed the alkali mist in the inert gas to the limit using a demister. Thus, it has been found that an inert gas from which silicon oxide and alkali mist have been removed can be obtained, and that recovery and purification in subsequent steps can be stably operated, and the present invention has been completed.

  Hereinafter, the present invention will be described in detail as an example of an embodiment with reference to the drawings. However, the present invention is not limited to this.

  FIG. 1 is a schematic view showing an example of an inert gas recovery pretreatment facility according to the present invention. In the pre-recovery treatment facility of the present invention, the inert gas discharged from the silicon single crystal production apparatus 1 is passed through the water 3a and received in the gas holder 2, and the strong alkaline solution 7 in the lower water tank of the gas-liquid separation tower 6 is circulated. The pump 8 is sent to the Nash pump 60 and the static mixer 50 to stir the inert gas and the strong alkali solution 7 fed from the gas holder 2. By stirring with the Nash pump 60 or the static mixer 50, the silicon oxide in the inert gas is dissolved in the strong alkaline solution 7 and removed.

  At this time, as the strong alkali solution, for example, a caustic soda solution, a potassium hydroxide solution, a lithium hydroxide solution, a rubidium hydroxide solution, a cesium hydroxide solution, or the like can be used. Among these, it is preferable to use an inexpensive caustic soda solution because the cost can be suppressed.

  Moreover, the means for dissolving and removing silicon oxide by contacting it with a strong alkali solution is one of a liquid ring compressor, an ejector, a static mixer, and a Nash pump, or a combination of two or more. It is preferable.

  Since the liquid ring compressor is capable of dissolving the silicon oxide in the inert gas by increasing the pressure of the inert gas to a predetermined pressure and bringing it into vigorous contact with the strong alkaline solution used as the sealing liquid, It is effective when contacting an inert gas with a large air volume with a strong alkaline solution.

  FIG. 6 shows a schematic diagram of the ejector. As shown in FIG. 6, the ejector 40 has a chamber 41 whose inside is narrowed and a suction port 42 inside the center. A strong alkaline solution flows in from the inlet of the chamber 41 (see A in FIG. 6), and passes through the constricted portion inside. At this point, the flow rate of the strong alkali solution increases to become a mist state, and the pressure decreases. With this pressure loss, the inert gas is sucked from the suction port 42 and comes into contact with the mist strong alkali solution. Thus, by making a strong alkali solution into mist form, a contact and melt | dissolution with a silicon oxide can be accelerated | stimulated.

  FIG. 7 shows a schematic diagram of the static mixer. As shown in FIG. 7, the static mixer 50 has a plurality of elements 52 in the chamber 51 for stirring the inert gas and the strong alkaline solution. Then, a strong alkaline solution flows in from the inlet of the chamber 51 (see A in FIG. 7), an inert gas flows in from the gas inlet 53, and both elements that are in contact with each other are stirred by the element 52. Thus, the contact and dissolution with the silicon oxide can be promoted by the stirring effect of the static mixer 50.

  FIG. 8 shows a schematic diagram of a Nash pump. As shown in FIG. 8, the Nash pump 60 has a cylindrical casing 61 that stores a strong alkaline solution, an impeller 62 that has a central axis at a position eccentric to the central axis of the casing 61, and that can be rotated around the axis. It has a mouth 63 and an air inlet 64. When the impeller 62 having blades on the outer periphery is rotated, a strong alkaline solution flows along the inner cylindrical wall of the casing 61 to form a recirculation flow, compressing the inside of the pump, and an inert gas flows in from the intake port 64 Then, they come into contact with the strong alkali solution, and both are stirred by the rotation of the impeller 62, and the contact and dissolution with the silicon oxide are promoted. Then, the inert gas from which the silicon oxide has been removed is discharged from the exhaust port 63.

  If the means for dissolving and removing silicon oxide by bringing it into contact with a strong alkaline solution is as described above, the silicon oxide can be efficiently brought into contact with the silicon oxide in the inert gas. Therefore, silicon oxide can be more reliably removed.

  As described above, the inert gas and the strong alkali solution 7 are stirred to dissolve and remove the silicon oxide, and then the inert gas and the strong alkali solution 7 are separated by the gas-liquid separation tower 6. At this time, in order to remove the alkali mist accompanying the inert gas, neutralization of the alkali mist is performed using a water scrubber 9 after the gas-liquid separation tower 6. Further, in the present invention, the alkali mist is removed using the demister 10a in addition to the water scrubber 9. After removing the alkali mist, gas is sent from the pipe 15 to the recovery and purification facility to the recovery and purification facility in the subsequent step.

As the demister 10a, a candle demister is preferably used. If it is a candle type demister, it is possible to remove a submicron sized alkali mist that is moving in brown.
In addition to a candle type demister, a wire mesh type or inertial collision type demister can also be used to remove mist having a relatively large particle size.

  Further, it is most effective to install the demister in the gas-liquid separation tower 6 in which the strong alkali solution 7 that is the source of alkali mist is circulating as shown in FIG. Alkaline mist can be removed almost completely. In addition, the demister may not be installed in the gas-liquid separation tower 6 as shown in FIG. 4 but may be installed before and after the flush scrubber 9, and when installed before and after the flush scrubber 9, the alkali mist is removed with a removal rate of 95% or more. Can be removed.

  In the washing scrubber 9, the water 3b is sprayed from the upper part of the washing scrubber 9 using a pump, and the inert gas containing the alkali mist introduced from the lower part is brought into contact with the water 3b to neutralize the alkali mist.

  Moreover, in this invention, the fluctuation | variation of the acceptance amount of the inert gas from the silicon single crystal manufacturing apparatus 1 using the automatic flow regulator 12, the LICA (level indication controller) 13, and the FICA (flow indication controller) 14 is used. The air volume control can be automatically performed according to the above.

  Furthermore, as a preferred example of the inert gas recovery pretreatment facility of the present invention, a liquid ring compressor 4 is installed instead of the Nash pump 60 of FIG. 1, and a candle type demister 10b is installed at the upper part of the gas-liquid separation tower 6. FIG. 2 shows a cooling type condenser 11 installed after the candle type demister 10a.

  In the pre-recovery treatment facility shown in FIG. 2, the inert gas discharged from the silicon single crystal manufacturing apparatus 1 is passed through the water 3 a and received in the gas holder 2. Increase to pressure. By compressing, the strong alkali solution 7 used as a sealing liquid in the liquid seal compressor 4 is brought into vigorous contact with the inert gas, and the silicon oxide in the inert gas is dissolved in the strong alkali solution 7 and removed. To do.

  At this time, the strong alkaline solution 7 used as the sealing liquid is circulated from the lower water tank of the gas-liquid separation tower 6 by the circulation pump 8. After adjusting the temperature of the strong alkaline solution 7, the strong alkaline solution 7 is introduced into the liquid seal compressor 4, mixed with an inert gas, and introduced into the static mixer 50 as it is.

  After the temperature of the strong alkaline solution 7 taken out from the circulation pump 8 is adjusted with a heat exchanger for temperature adjustment, it is introduced into the static mixer 50 and mixed with vigorous contact with the above inert gas to strongly strengthen the silicon oxide. It is dissolved in the alkaline solution 7 and removed. Thereafter, the mixture is introduced into the gas-liquid separation tower 6 in a gas-liquid mixed state to separate the inert gas and the strong alkali solution 7, and the alkali mist accompanying the inert gas by the candle type demister 10 b installed at the upper part of the gas-liquid separation tower 6. Remove.

  The strong alkali solution 7 returned to the gas-liquid separation tower 6 returns to the water tank below the gas-liquid separation tower 6 and continuously circulates. Moreover, since a small amount of water glass is produced by the reaction between the strong alkali solution 7 and silicon oxide, this is periodically or automatically blown out of the system.

  Moreover, since the strong alkali solution 7 and water are consumed by continuous operation, the consumed strong alkali solution 7 and water are automatically replenished according to the fluctuation | variation of the level meter installed in the water tank. Further, the temperature of the circulating strong alkali solution is constantly adjusted by a heat exchanger, and the concentration is always measured.

  The alkali mist in the inert gas that has passed through the candle demister 10 b is neutralized by the water scrubber 9, and further removed by the candle demister 10 a installed after the water scrubber 9. The cooling water is cooled to 10 ° C. or less by the cooling condenser 11 to condense the accompanying water, and is discharged from the drain 16 to the outside of the system.

  Even after the alkali mist is removed, the moisture in the inert gas is almost saturated, and it is desirable to control the temperature according to the subsequent process. Specifically, the inert gas is cooled using the cooling condenser 11, and the mist component is condensed and discharged from the drain 16 to the outside of the system. As a heat source for condensing the mist, cold water such as brine is used, and the temperature is controlled to be a predetermined dew point or lower.

  As described above, with the inert gas recovery pretreatment facility of the present invention, the silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus can be sufficiently removed, and the silicon oxide has been removed. Since the mist containing the alkali component in the subsequent inert gas can also be effectively removed, the recovery and purification of the inert gas in the subsequent step can be stably operated. Further, by performing dehumidification after removing the alkali mist, it is possible to reduce the burden at the time of recovery and purification of the inert gas in the subsequent step. Further, there is a concern when the recovered and purified gas is reused, and phosphorus and boron contained in the inert gas together with the silicon oxide can be removed at the same time.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

Example 1
In Example 1, argon gas pre-recovery treatment was performed in the inert gas pre-treatment facility shown in the schematic diagram of FIG.
1) Argon gas is received in the gas holder with an air volume of 3.3 to 13.5 Nm ³ / min, and the liquid-sealed compressor always compresses 10 to 20 Nm ³ / min of argon gas, and the circulation pump from the gas-liquid separation tower The silicon oxide in the argon gas was dissolved and removed by stirring with a caustic soda solution of 6 to 8 m ³ / min and a static mixer. At this time, the temperature of the caustic soda solution was 40 to 50 ° C., the concentration of the caustic soda solution was 10 to 15%, the argon gas was at room temperature, and the treatment time was continuous for 24 hours.
2) The argon gas and the caustic soda solution were separated in the gas-liquid separation tower, and the alkali mist accompanying the argon gas was removed by a candle type demister (i) installed at the upper part of the gas-liquid separation tower.
3) After neutralizing the argon gas exiting the gas-liquid separation tower with a water scrubber, alkali mist accompanying the argon gas was removed with a candle type demister (ii) installed after the water scrubber.
4) Argon gas was cooled to 10 ° C. or less with a cooling condenser, and the silicon oxide removal rate at the outlet after removing the condensed mist drain, the detected amount of alkali mist, and pH were confirmed.
5) A part of the argon gas was returned to the liquid ring compressor before the cooling condenser, and the air volume control was automatically performed according to the variation in the amount of waste argon gas received.

(Example 2)
The inert gas recovery pretreatment was performed using the same equipment as in Example 1 except that the candle type demister (i) installed in the gas-liquid separation tower in Example 1 was not installed.

(Comparative Example 1)
Except for the candle type demister (i) installed in the gas-liquid separation tower in Example 1 and the candle type demister (ii) installed after the flush scrubber, the same equipment as in Example 1 was used. Collection pretreatment was performed.

(Comparative Example 2)
In Comparative Example 2, the argon gas and the caustic soda solution were stirred with a Nash pump, an ejector and a static mixer to dissolve and remove the silicon oxide in the argon gas. Subsequently, the argon gas from which the silicon oxide was removed was neutralized with a water scrubber. This facility corresponds to the silicon oxide removing apparatus described in Patent Document 1.

  Silicon gas removal rate, alkali components, dew point temperature of cooling condenser inlet, and cooling condenser outlet of argon gas subjected to pre-recovery treatment using the inert gas recovery pretreatment equipment of Examples and Comparative Examples The results of measuring the dew point temperature are shown in Table 1 below.

As shown in Table 1, in Example 1 and Example 2 in which a demister was installed, silicon oxide could be sufficiently removed, and alkali mist could be effectively removed. In particular, in Example 1 in which two demisters were installed, the alkali mist could be removed almost completely. Furthermore, the water | moisture content in argon gas was also removable by using a cooling-type capacitor | condenser.
On the other hand, in Comparative Example 1 and Comparative Example 2 in which no demister was installed, the silicon oxide was sufficiently removed, but the alkali mist was not sufficiently removed.

  From the above, with the inert gas recovery pretreatment facility of the present invention, the silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus is sufficiently removed, and the silicon oxide is removed. It became clear that the mist containing the alkali component in later inert gas can be removed effectively.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... Silicon single crystal manufacturing apparatus, 2 ... Gas holder, 3a, 3b ... Water,
4 ... Liquid ring compressor, 6 ... Gas-liquid separation tower, 7 ... Strong alkaline solution,
8 ... circulation pump, 9 ... wash scrubber,
10a, 10b, 10c ... candle type demister, 11 ... cooling condenser,
12 ... Automatic flow controller, 13 ... LICA, 14 ... FICA,
15 ... Pipe to recovery and purification equipment, 16 ... Drain, 40 ... Ejector,
41 ... Ejector chamber, 42 ... Suction port,
50 ... Static mixer, 51 ... Static mixer chamber,
52 ... Element, 53 ... Gas inlet, 60 ... Nash pump,
61 ... casing, 62 ... impeller, 63 ... exhaust port, 64 ... intake port.

Claims (5)

A recovery pretreatment facility for inert gas discharged from a silicon single crystal manufacturing apparatus,
Means for dissolving and removing silicon oxide in the inert gas discharged from the silicon single crystal manufacturing apparatus by contacting it with a strong alkali solution; and alkali in the inert gas after removing the silicon oxide It has a means for removing mist containing components using a demister,
The demister is installed after a washing scrubber for neutralizing the mist containing the alkali component, and further installed in a gas-liquid separation tower in which the strong alkali solution circulates. Recovery pretreatment equipment.   The means for dissolving and removing the silicon oxide by bringing it into contact with a strong alkali solution is one of a liquid ring compressor, an ejector, a static mixer, and a Nash pump, or a combination of two or more. The inert gas recovery pretreatment facility according to claim 1.   The inert gas recovery pretreatment facility according to claim 1 or 2, wherein the demister is a candle type demister.   The inert gas recovery pretreatment facility according to any one of claims 1 to 3, wherein moisture is removed by a cooling condenser after the alkali component is removed by the demister.   The inert gas recovery pretreatment facility according to any one of claims 1 to 4, wherein the strong alkali solution is a caustic soda solution.

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