JP2009280474A - Apparatus for producing silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for producing silicon, which can improve the purity of silicon. <P>SOLUTION: The apparatus 10 for producing silicon has a reaction device for obtaining silicon particles by reducing a silane halide with a molten reductive metal. At least one portion of the inner surface of the apparatus 10 is coated with at least one of a silicon layer and a fluorine-based resin layer (coating layer 21). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a silicon manufacturing apparatus.

  As environmental problems are highlighted, solar cells are attracting attention as a clean energy source, and demand is rapidly increasing mainly for residential use. Since silicon-based solar cells are excellent in reliability and conversion efficiency, they account for about 80% of solar power generation. However, in order to further reduce the unit price of power generation, it is desired to secure a low-cost silicon raw material.

  Currently, the Siemens method in which trichlorosilane and hydrogen are reacted at a high temperature is mainly employed as a method for producing high-purity silicon. However, this method is said to be difficult to further reduce costs because there is a limit to the reduction in power consumption.

As an alternative to the Siemens method, for example, Patent Document 1 listed below discloses a gaseous silicon compound having the general formula SiH _n X _4-n (wherein X represents a halogen atom and n represents an integer of 0 to 3, respectively). Has been disclosed that contacts a finely dispersed pure aluminum or Al—Si alloy molten surface. Patent Document 2 below discloses a silicon manufacturing apparatus including a reaction vessel for obtaining silicon by reacting metal particles with gaseous silicon chlorine compound.

Japanese Patent Laid-Open No. 2-64006 JP 2007-284259 A

  However, when metal is used as the silicon production apparatus, the inner wall of the apparatus is easily corroded by halides such as silane halide, halide of reducing metal, and by-product during the production of silicon. The problem is that a part of the silicon is mixed in the silicon and the purity of the silicon is lowered. Another problem is that a part of the inner wall of the apparatus is scraped off by particles made of silicon generated in the manufacturing apparatus, and a part of the scraped inner wall is mixed into the silicon, thereby lowering the purity of silicon. .

  The present invention has been made in view of such circumstances, and provides a silicon manufacturing apparatus capable of improving the purity of silicon.

  In order to achieve the above object, a silicon production apparatus of the present invention is a silicon production apparatus having a reaction apparatus for obtaining silicon particles by reducing a halogenated silane with a molten reducing metal, At least a part of the inner surface (inner wall) is covered with at least one of a silicon layer and a fluorine resin layer.

  In the present invention, since at least a part of the inner surface (inner wall) of the apparatus is coated (lined) with at least one of a silicon layer and a fluorine resin layer, silane halide and reducing metal are not produced during the production of silicon. Corrosion of the inner wall of the apparatus due to halides such as halides and other by-products can be prevented, and a part of the corroded inner wall of the apparatus can be prevented from being mixed into silicon. Further, it is possible to prevent a part of the inner wall of the apparatus from being scraped off by silicon particles generated in the manufacturing apparatus by lining, and to prevent a part of the scraped inner wall of the apparatus from being mixed into silicon. Furthermore, even if a part of the silicon layer covering the inner wall is scraped off by silicon particles and mixed in the manufactured silicon, the silicon layer and the silicon manufactured by the manufacturing apparatus have the same composition, The purity of the silicon to be produced does not decrease. For the above reasons, in the present invention, it is possible to prevent silicon contamination and improve the purity of silicon.

  The present invention includes a reaction apparatus for obtaining silicon particles by reducing halogenated silane with a molten reducing metal, and a mixture containing silicon particles, halogenated silane, and reducing metal halide supplied from the reaction apparatus. , A solid-gas separation device for separating a gas containing a silane halide and a reducing metal halide and silicon particles, a storage device for temporarily storing silicon particles supplied from the solid-gas separation device, and a reaction device A first pipe for connecting the solid-gas separation device and the solid-gas separation device, a second pipe for connecting the solid-gas separation device and the storage device, and a third pipe for taking out the silicon particles stored in the storage device from the storage device, The inner surface of at least one of the solid-gas separation device, the storage device, the first piping, the second piping, and the third piping is covered with at least one of a silicon layer or a fluorine resin layer. It is preferable to have, solid-gas separation device, a storage device, the first pipe, it is more preferable that the entire inner surface of the second pipe and the third pipe is at least coated with one of the silicon layer or a fluorine-based resin layer.

  The silicon production apparatus includes a solid-gas separation device, a storage device, a first pipe, a second pipe, and a third pipe, and the inner surface thereof is covered with a silicon layer or a fluorine resin layer, thereby obtaining high-purity silicon. Can be easily manufactured.

  In the present invention, the solid-gas separation device is preferably a cyclone.

  When the silicon production apparatus includes a cyclone excellent in solid-gas separation ability as a solid-gas separation apparatus, it becomes easy to improve the purity and yield of silicon.

  The present invention preferably further includes a melting device for melting silicon particles. The present invention preferably further includes a solidifying device that cools and solidifies the silicon particles melted by the melting device.

  Since silicon particles have a large specific surface area and high activity compared to bulk silicon, they tend to be contaminated by reaction with halides, air, or the inner wall of the apparatus, and the purity of the silicon particles tends to decrease. However, in the present invention, the silicon particles are melted with a melting device to form liquid silicon, and further, the liquid silicon is cooled and solidified with a solidifying device, so that the specific surface area of silicon is reduced and there is an opportunity for contamination of silicon. Therefore, the purity of silicon can be improved more reliably.

  ADVANTAGE OF THE INVENTION According to this invention, the silicon manufacturing apparatus which can improve the purity of silicon can be provided.

  Hereinafter, a silicon manufacturing apparatus and operating conditions thereof according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  As shown in FIG. 1, the silicon production apparatus 10 according to this embodiment includes a reaction apparatus 3, solid-gas separation apparatuses 5 a, 5 b, 5 c, 6 a, 6 b, a storage apparatus 23, a melting apparatus 25, and a solidification apparatus 27. . The silicon production apparatus 10 includes a pipe L2 (first pipe) for connecting the reaction apparatus 3 and the solid-gas separation apparatus 5a, and a pipe L9 (first pipe) for connecting the reaction apparatus 3 and the solid-gas separation apparatus 5b. Pipes L15 and L13 (second piping) connecting the solid-gas separation device 5a and the storage device 23, piping L11 and L13 (second piping) connecting the solid-gas separation device 5b and the storage device 23, and the storage device 23 And a melting pipe 25 (third pipe) for connecting the melting device 25 is provided. Further, the manufacturing apparatus 10 includes a plurality of pipes other than these, which will be described later.

In the reactor 3, tetrachlorosilane, which is a kind of halogenated silane, is reduced with molten aluminum (reducing metal) to form silicon particles. In the solid-gas separation devices 5a and 5b, a mixture containing silicon particles supplied from the reaction device 3, unreacted tetrachlorosilane (SiCl ₄ ) gas, aluminum chloride (AlCl ₃ ) gas as a by-product, and the like is converted into tetrachlorosilane. It is separated into a mixed gas containing gas and aluminum chloride gas and silicon particles. In the storage device 23, the silicon particles supplied from the solid-gas separation devices 5a, 5b, and 5c are temporarily stored. In the melting device 25, the silicon particles supplied from the storage device 23 are melted to liquefy the silicon particles. In the solidifying device 27, the molten silicon supplied from the melting device 25 is cooled and solidified.

  The entire inner surfaces of the solid-gas separation devices 5a, 5b, 5c, the storage device 23, the pipes L2, L9, L11, L12, L13, L15, L17, and L23 (hereinafter referred to as “device inner surfaces”) are covered by the coating layer 21. It is covered. The coating layer 21 is composed of a fluorine resin layer that covers the inner surface of the device or a silicon layer that covers the inner surface of the device. By covering the entire inner surface of the apparatus with the coating layer 21, it becomes easy to prevent corrosion of the inner wall of the apparatus due to halides, and it becomes easy to prevent scraping of the inner wall of the apparatus due to silicon particles generated in the manufacturing apparatus. It becomes easy to improve.

  In order to obtain the above effect of the present invention, it is preferable that the entire inner surface of the apparatus except for the reactor 3 is coated with the coating layer 21, but even if the inner surface of the apparatus is partially coated with the coating layer 21, The effects of the present invention can be achieved. Further, the solid-gas separation devices 5a, 5b, 5c, the storage device 23, the pipes L2, L9, L11, L12, L13, L15, L17, and L23 are not only the inner wall made of the coating layer 21, but also a metal with high mechanical strength. Therefore, the mechanical strength of these devices and pipes is maintained.

  Examples of the fluorine resin contained in the fluorine resin layer include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF). As will be described later, the temperature inside the solid-gas separation devices 5a, 5b, 5c, the first piping, the second piping, and the third piping is adjusted to be 200 ° C. or higher, so that the coating layer 21 is required to have heat resistance under these temperature conditions. The coating layer 21 is also required to have corrosion resistance and mechanical strength against halides. Polytetrafluoroethylene is preferably used as the fluororesin from the viewpoint of excellent heat resistance, corrosion resistance to halides and mechanical strength.

A heater (not shown) is provided around the pipes L2, L9, L11, L12, L13, L15, L17, and L23 so that the temperature inside each pipe can be adjusted. It is preferable to maintain at a temperature at which AlCl ₃ (sublimation point: 180 ° C.) does not precipitate, and specifically, it is preferable to maintain at 200 ° C. or higher. Thereby, it becomes easy to improve the purity of the obtained silicon. When the temperature inside each pipe is lower than 200 ° C., AlCl ₃ precipitates inside each pipe and tends to be mixed into silicon particles.

(Reactor 3)
In the reactor 3, by spraying a raw material gas G1 containing tetrachlorosilane onto the molten aluminum F1 (a trickle of molten aluminum) as an atomizing gas, fine droplets made of the molten aluminum F1 are formed. When the tetrachlorosilane in G1 comes into contact, the reaction represented by the following formula (A) proceeds to form silicon particles.
3SiCl ₄ + 4Al → 3Si + 4AlCl ₃ (A)

  The reaction apparatus 3 includes a molten metal storage part (molten metal supply means) 1, a raw material gas discharge part (raw material gas supply means) 2, a cylindrical part 3a, a reduced diameter part 3b, and the like.

  The molten metal container 1 is for containing molten aluminum and is provided in the sealed container 15. A heater 11 is provided around the molten metal container 1 so that the temperature of the molten aluminum to be accommodated can be adjusted. A first nozzle extending to the inside of the reaction device 3 is provided at the bottom of the molten metal container 1. Molten aluminum F1 flows down from the first nozzle in the vertical direction. When the molten aluminum is stored in the molten metal container 1, the molten aluminum can be stably discharged from the first nozzle into the reaction device 3, and silicon particles can be manufactured stably and continuously. There is an advantage. Moreover, you may pressurize the inside of the airtight container 15 which accommodates the molten metal accommodating part 1 with an inert gas. Thereby, molten aluminum can flow down more stably.

  The molten aluminum flowing down from the first nozzle preferably has a purity of 99.9% by mass or more, more preferably 99.99% by mass or more, and further preferably 99.995% by mass or more. . By using high-purity molten aluminum, high-purity silicon particles can be obtained. The purity of molten aluminum here refers to the content (mass%) of Fe, Cu, Ga, Ti, Ni, Na, Mg, and Zn among the elements measured by glow discharge mass spectrometry of the raw material aluminum. Is the value obtained by subtracting the total of 100% by mass.

  In addition, from the viewpoint of obtaining silicon suitable as a silicon raw material for solar cells, the total content of boron B, phosphorus P and oxygen O contained in the raw material aluminum is preferably 1 mass ppm or less. Such high-purity aluminum can be obtained by purifying aluminum generally produced by electrolytic reduction by a segregation solidification method, a three-layer electrolytic method, or the like.

  The temperature in the molten metal accommodating part 1 is kept above the melting point of the molten metal, and the molten metal is kept warm so that the molten metal does not solidify. The temperature of the molten metal container 1 may be appropriately set according to the melting point of the metal to be melted. However, when aluminum (melting point: 660 ° C.) is used as the reducing metal as in this embodiment, it is usually 700. It is -1300 degreeC, Preferably it is 700-1200 degreeC, More preferably, it is 700-1000 degreeC. The temperature of the first nozzle is preferably about 700 to 1000 ° C.

  The raw material gas discharge unit 2 (second nozzle) is for injecting the raw material gas G1 supplied through the pipe L1 toward the molten aluminum F1 as an atomized gas and spraying the molten aluminum F1. As shown in FIG. 1, by spraying the raw material gas G1 on the molten aluminum F1, fine droplets of molten aluminum are formed, the microdroplets and the tetrachlorosilane contained in the raw material gas G1 come into contact with each other, and the chemical formula (A ) Proceeds efficiently.

  The angle α shown in FIG. 1 (the angle formed between the flowing direction of the molten aluminum F1 and the discharging direction of the raw material gas G1) is preferably larger than 0 ° and not larger than 90 °, larger than 0 ° and 55 °. More preferably, it is more preferably 0 ° or more and 40 ° or less. When the angle α exceeds 90 °, the supply of the molten aluminum F1 from the first nozzle into the reactor 3 is likely to be hindered by the raw material gas G1.

  The raw material gas G1 discharged from the second nozzle preferably has a flow rate of 50 to 1000 m / sec from the viewpoint of achieving a high reaction rate.

  The source gas (atomizing gas) discharged from the second nozzle is a mixed gas of tetrachlorosilane and an inert gas. As the inert gas contained in the source gas, argon and / or helium is preferable, and argon is more preferable from the viewpoint of cost.

  The concentration of tetrachlorosilane in the raw material gas is preferably 10% by volume or more, more preferably 20% by volume or more, and still more preferably 50% by volume or more. There exists a tendency for reaction of the said Formula (A) not to fully advance that the density | concentration of tetrachlorosilane is less than 10 volume%. In the reaction of the above formula (A), reaction heat of 95 kJ is generated per mole of aluminum. By adding a predetermined amount of inert gas to the raw material gas, the generated reaction heat can be controlled, and the reaction apparatus 3 can be sufficiently prevented from being damaged by the reaction heat. In addition to the inert gas, hydrogen that does not contribute to the reaction may be added to the source gas. Moreover, in order to prevent damage to the apparatus, an inner cylinder having heat insulation performance may be installed.

  From the viewpoint of obtaining high-purity silicon particles, the tetrachlorosilane used for the preparation of the source gas preferably has a purity of 99.99% by mass or more, more preferably 99.999% by mass or more, 99 More preferably, it is 9999% by mass or more.

  From the viewpoint of obtaining high-purity silicon particles, the inert gas used for the preparation of the raw material gas preferably has a purity of 99.9% by volume or more, more preferably 99.99% by volume or more, More preferably, it is 99.999 volume% or more, and it is especially preferable that it is 99.9995 volume% or more.

  The raw material gas sprayed onto the molten aluminum F1 is preferably discharged at a pressure of 0.1 to 15 MPa, more preferably discharged at a pressure of 1 to 10 MPa, and further preferably discharged at a pressure of 2 to 10 MPa. preferable. When the pressure at which the raw material gas is discharged is less than 0.1 MPa, the reaction represented by the above formula (A) tends to become insufficient. On the other hand, in order to discharge the raw material gas at a pressure exceeding 15 MPa, it is necessary to use various devices having high pressure resistance, and the cost tends to increase.

  The source gas sprayed on the molten aluminum F1 may be heated in advance. The temperature of the heated source gas is preferably 200 to 1200 ° C, and more preferably 200 to 1000 ° C. By increasing the temperature of the heated source gas, the reduction reaction of tetrachlorosilane is further facilitated. There is no restriction | limiting in particular as a method of heating source gas, For example, the method using high frequency heating, resistance heating, lamp heating etc. is mentioned. Alternatively, a gas heated to a temperature higher than the temperature of tetrachlorosilane (at least one or more selected from the group consisting of argon, helium and hydrogen) and tetrachlorosilane are mixed to obtain a high temperature source gas. Also good. According to this method, there is an advantage that it is not necessary to frequently use an expensive corrosion-resistant material having resistance to high temperature corrosion caused by tetrachlorosilane.

  Note that the source gas may be a liquid or a supercritical fluid depending on the temperature condition and the pressure condition in the stage before being discharged from the second nozzle.

  By spraying the source gas heated as described above onto the molten aluminum, the temperature drop of the molten aluminum can be suppressed, and the temperature of the molten aluminum F1 can be maintained at a temperature higher than the freezing point. If the temperature of the molten aluminum F1 is locally below the freezing point, stable supply of the molten aluminum F1 may be hindered.

  Tetrachlorosilane gas has a property of corroding a metal material. In order to suppress metal corrosion due to tetrachlorosilane gas, the second nozzle is made of a ceramic material or a carbon material, specifically, alumina, silicon carbide, silicon nitride, quartz, mullite, zirconia, cordierite or carbon. It is preferable to use a member formed of a member coated with the above-mentioned material.

  A reaction field in which the reaction represented by the above formula (A) proceeds is formed in the cylindrical portion 3a included in the reaction device 3. Here, as in the above formula (A), the stoichiometric ratio of the number of moles of tetrachlorosilane and the number of moles of molten aluminum in the reaction is 3: 4, but is supplied to the reaction field from the viewpoint of productivity and the like. The ratio (M1 / M2) of the number of moles M1 of tetrachlorosilane per unit time and the number of moles M2 of molten aluminum supplied (M1 / M2) is preferably 0.75 to 20, more preferably 0.75 to 10. 0.75 to 7.5 is more preferable. If the value of M1 / M2 is less than 0.75, the progress of the reaction tends to be insufficient, whereas if it exceeds 20, the amount of tetrachlorosilane that does not contribute to the reaction tends to increase.

  A heater 13 is provided around the cylindrical portion 3a so that the temperature of the reaction field can be adjusted. The heating method is not particularly limited. For example, in addition to a direct method using high-frequency heating, resistance heating, lamp heating, or the like, a method using a fluid such as a gas whose temperature is adjusted in advance can be used. The temperature of the reaction field is usually adjusted to be 300 to 1200 ° C. (preferably 500 to 1000 ° C.). Moreover, the pressure in the reaction field is usually adjusted to be 1 atm or higher. When the reaction in the reaction apparatus 3 is interrupted or stopped, if by-products or unreacted substances solidify on the wall surface of the reaction apparatus 3, stress corrosion cracking of the apparatus material may occur. As a preventive measure, the temperature in the reaction apparatus 3 may be maintained at a predetermined temperature even when the reaction is interrupted or stopped by using a heater 13 or an external jacket (not shown) and using a heat retaining gas.

  The oxygen concentration in the reaction field formed in the cylindrical portion 3a is preferably maintained as low as possible from the viewpoint of sufficiently suppressing the formation of oxides. Specifically, the oxygen concentration in the reaction field before starting the reaction is preferably 1% by volume or less, more preferably 0.1% by volume or less, and further preferably 100% by volume or less. It is preferably 10 ppm by volume or less, particularly preferably. As a method for lowering the oxygen concentration in the reaction field before the start of the reaction, there is a technique in which molten aluminum is sprayed for a predetermined time, and oxygen in the reaction field is adsorbed to aluminum droplets. In addition, as for the reaction field before starting reaction, it is preferable that a dew point is -20 degrees C or less, It is more preferable that it is -40 degrees C or less, It is still more preferable that it is -70 degrees C or less.

  In addition, the oxygen concentration in the reaction field is preferably maintained as low as possible from the viewpoint of sufficiently suppressing the formation of oxides even during the reaction. Specifically, the oxygen concentration in the reaction field during the reaction is preferably 1% by volume or less, more preferably 0.1% by volume or less, still more preferably 100% by volume or less. It is particularly preferable that the volume be ppm or less. By generating silicon under such conditions, silicon oxide film formation can be sufficiently suppressed. As a result, the silicon purification process can be simplified, and the production cost of silicon suitable for a solar cell material can be reduced.

The reactor 3 is provided with a reduced diameter portion 3b having a silicon particle discharge port 3c for discharging silicon particles at the lower end while decreasing the inner diameter as it goes downward in the lower part thereof. A solid gas for discharging a mixture containing AlCl ₃ (gas) generated by the reaction, unreacted SiCl ₄ (gas), fine silicon particles, and the like is provided at a substantially intermediate position in the vertical direction of the reduced diameter portion 3b. A mixed fluid discharge port (discharge means) 3d is provided. The solid / gas mixed fluid discharged from the solid / gas mixed fluid discharge port 3d is supplied to the solid / gas separation device 5a through the pipe L2.

A heater (not shown) is provided around the reduced diameter portion 3b provided at the lower part of the reaction apparatus 3, so that the internal temperature can be adjusted. By maintaining the temperature inside the reduced diameter portion 3b at a temperature at which AlCl ₃ (sublimation point: 180 ° C.) does not precipitate, the silicon particles and the gas are separated. The silicon particles separated from the gas by the reduced diameter portion 3b are discharged from the silicon particle discharge port 3c and supplied to the solid-gas separation device 5b through the pipe L9 (first pipe). In addition, it is preferable that the temperature inside the reduced diameter part 3b shall be 200 degreeC or more. When the temperature inside the reduced diameter portion 3b is lower than 200 ° C., AlCl ₃ tends to be precipitated in the reduced diameter portion 3b and easily mixed into silicon particles.

(Solid-gas separation device 5a)
The solid-gas separation device 5a is for separating and recovering silicon particles present in the gas supplied from the solid-gas mixed fluid discharge port 3d through the pipe L2. The silicon particles separated from the gas by the solid-gas separation device 5a are supplied to the storage device 23 through the pipes L15 and L13. In addition, it is preferable that the temperature inside the solid-gas separation device 5a is 200 ° C. or higher as in the case of the temperature inside the reduced diameter portion 3b. Moreover, as the solid-gas separation device 5a, a heat-retaining cyclone solid-gas separation device is preferable. Filters such as bag filters or membrane filters may be used as the solid-gas separation device 5a other than the heat-retaining cyclone solid-gas separation device.

(Solid-gas separation device 6a)
The gas discharged from the solid gas separation device 5a is supplied to the solid gas separation device 6a through the pipe L4. The solid gas separator 6a is for removing AlCl ₃ contained in the gas supplied from the solid gas separator 5a. By maintaining the temperature in the solid-gas separator 6a at a temperature at which AlCl ₃ is precipitated but SiCl ₄ (boiling point: 57 ° C.) is not condensed, the precipitated AlCl ₃ (solid) is removed. Specifically, the temperature inside the solid-gas separation device 6a is preferably maintained at 60 to 170 ° C, more preferably 70 to 100 ° C. When the temperature inside the solid-gas separator 6a is lower than 60 ° C., the SiCl ₄ is condensed in the solid-gas separator 6a, and the amount of SiCl ₄ to be recycled tends to be insufficient. On the other hand, if it is higher than 170 ° C. The temperature of the interior of the solid-gas separation device 6a, precipitation of AlCl ₃ becomes insufficient, tends to increase the amount of SiCl ₄ in AlCl ₃ that are recycled.

The solid-gas separation device 6a is preferably provided with a baffle plate (not shown) therein. By providing the baffle plate inside, the inner surface area of the solid-gas separation device 6a is increased, AlCl ₃ is efficiently precipitated, and the content of AlCl ₃ in the gas can be sufficiently reduced. The internal surface area of the solid-gas separation device 6a is preferably 5 times or more the device surface area of the solid-gas separation device 6a.

The gas from which AlCl ₃ is removed in the solid-gas separator 6a is discharged from the solid-gas separator 6a through the pipe L7. When an unreacted tetrachlorosilane gas and an inert gas coexist in the gas, the tetrachlorosilane can be recovered by separating the inert gas and performing purification as necessary. This tetrachlorosilane may be recycled as a raw material gas. In this way, by collecting unreacted gas and by-products and effectively using them, it is possible to suppress an increase in cost required for these detoxification, and it is possible to sufficiently reduce the manufacturing cost of silicon. In general, water or an alkaline aqueous solution can be used for detoxification of the halogenated silane, but sufficient attention must be paid to the generation of a hydrochloric acid component.

  In addition, when there is little unreacted gas contained in the gas discharged | emitted from the solid-gas separation apparatus 6 through the piping L7, when it can be removed at low cost with a simple removal means, unreacted gas and a by-product are removed. In the case where it is possible to reduce the manufacturing cost of silicon by directly removing the gas without collecting it, the gas may be transferred directly to the removal device.

(Solid-gas separation device 5b)
In the solid-gas separation device 5b, gas components (AlCl ₃ gas, unreacted SiCl ₄ gas, etc.) mixed therein are separated and removed from the silicon particles supplied from the reaction device 3 through the pipe L9 (first pipe). Is for. The silicon particles from which the gas components have been removed in the solid-gas separator 5b are supplied to the storage device 23 through the pipes L11 and L13. Further, the gas component separated from the silicon particles in the solid-gas separation device 5b is supplied to the solid-gas separation device 5c through the pipe L17.

(Solid-gas separation device 5c)
The solid-gas separator 5c is for recovering silicon particles remaining in gas components (AlCl ₃ gas, unreacted SiCl ₄ gas, etc.) supplied from the solid-gas separator 5b. The silicon particles separated from the gas component in the solid-gas separation device 5c are supplied to the storage device 23 through the pipes L12 and L13. The gas component separated from the silicon particles in the solid-gas separation device 5c is supplied to the solid-gas separation device 6b through the pipe L19.

  The solid-gas separation devices 5b and 5c have the same structure as the above-described solid-gas separation device 5a and operate under the same operating conditions as the solid-gas separation device 5a. As the solid-gas separation devices 5b and 5c, it is preferable to use a heat-retaining cyclone solid-gas separation device as in the case of the solid-gas separation device 5a.

(Solid-gas separation device 6b)
The solid-gas separation device 6b is for removing AlCl ₃ contained in the gas supplied from the solid-gas separation device 5c. The structure and operating conditions of the solid-gas separator 6b are the same as those of the solid-gas separator 6a.

The gas from which AlCl ₃ is removed in the solid-gas separation device 6b is discharged from the solid-gas separation device 6b through the pipe L21. Tetrachlorosilane can be recovered from the gas discharged from the pipe L21 as in the case of the gas discharged from the pipe L7. Further, when the amount of unreacted gas contained in the gas discharged from the solid-gas separation device 6b through the pipe L21 is small, the gas is directly transferred to the abatement equipment as in the case of the gas discharged from the pipe L7. May be.

(Storage device 23)
The silicon particles separated from the gas components in the solid-gas separation devices 5a, 5b, and 5c are supplied to the storage device 23. The silicon particles temporarily stored in the storage device 23 are supplied to the melting device 25 through the pipe L23 (third pipe). As described above, by temporarily storing the silicon particles in the storage device 23 and then supplying the silicon particles to the melting device 25, it is possible to adjust the processing capabilities of the melting device 25 and the solidifying device 27.

(Melting device 25)
In the melting device 25, the silicon particles are melted. Examples of the melting device 25 include an electric furnace (resistance heating furnace, induction heating furnace), a gas furnace, and the like. These furnaces are kept at about 1500 ° C. until a certain amount of silicon is stored in the crucible in the furnace. In the melting apparatus 25, it is preferable to melt the silicon particles in a high purity inert gas atmosphere (Ar or the like) or in a vacuum. Thereby, contamination (for example, oxidation and nitridation) of silicon particles in the melting apparatus 25 can be prevented, and contamination of impurities into molten silicon can be prevented.

(Solidification device 27)
The silicon melted by the melting device 25 is supplied to the solidifying device 27 through the pipe L25. In the solidifying device 27, the molten silicon is cooled and solidified to form an ingot made of silicon. By using silicon as an ingot, handling of silicon becomes easy. In the solidification device 27, it is preferable to cool and solidify the molten silicon in a high-purity inert gas atmosphere (Ar or the like) or in a vacuum. Thereby, silicon contamination (for example, oxidation and nitridation) in the solidifying device 27 can be prevented, and impurities can be prevented from being mixed into the silicon.

  In the present embodiment, the silicon particle recovery equipment (solid-gas separation devices 5a, 5b, 5c, storage device 23, piping L2, L9, L11, L12, L13, L15, L17, L23) formed in the reactor 3 is used. Since the inner surface (device inner surface) is lined with a coating layer 21 (at least one of a silicon layer and a fluorine resin layer), chlorides such as tetrachlorosilane, aluminum chloride, and other by-products are produced during the production of silicon. Corrosion of the inner surface of the apparatus due to the above is prevented, and a part of the corroded inner wall is also prevented from being mixed into silicon. Further, it is possible to prevent part of the inner surface of the apparatus from being scraped off by silicon particles generated in the manufacturing apparatus, and to prevent a part of the scraped inner wall from being mixed into silicon. Therefore, in this embodiment, it is possible to prevent contamination of silicon by a substance derived from the inner surface of the apparatus and improve the purity of silicon. That is, in the present embodiment, it is possible to recover the silicon with high purity without contaminating the silicon generated by the reaction device 3. In the present embodiment, the fact that the silicon particles are melted without being exposed to the outside air in the manufacturing apparatus 10 and then solidified also contributes to improving the purity of silicon.

  In the present embodiment, the diameter-reduced portion 3b of the reactor 3 and the solid-gas separation devices 5a, 5b, and 5c are provided as the silicon particle collection means, and the solid-gas separation device 6a is provided as the unreacted tetrachlorosilane gas collection means. , 6b. By adopting such a configuration, the silicon particles can be recovered in multiple stages to improve the purity and yield of the silicon particles, and the unreacted tetrachlorosilane can be efficiently recovered and a part of the raw material gas can be recovered. Can be reused as In addition, by removing solids (mainly silicon particles) in advance, unreacted substances can be easily separated by distillation from the mixed fluid of by-products and unreacted substances, and the wear of the recovery device that performs distillation separation is sufficient. Can be suppressed.

  The number of stages of the solid-gas separation device is not particularly limited. For example, the reduced-diameter portion 3b and the solid-gas separation device 6a may be connected without using the solid-gas separation device 5a, or the solid-gas separation device may be connected. One or more solid-gas separation devices may be further provided between the device 5b and the solid-gas separation device 5c. The gas discharge port 3d is not necessarily provided in the reduced diameter portion 3b, and may be provided in the cylindrical portion 3a of the reaction device 3, for example.

  Further, as a means for collecting silicon particles, a filter may be used in combination in addition to the solid-gas separator. In this case, in order to prevent clogging due to sticking of by-products or the like to the filter, the filter or the like may be kept warm. On the other hand, the life of the apparatus material can be extended by cooling to a temperature at which the by-products and unreacted substances do not aggregate. In general, leaching with an acid or alkali solution may be performed to remove a metal component mixed in the collected silicon. Thereafter, the silicon may be melted and purified for further purification by utilizing the segregation action during solidification.

  In the present embodiment, a raw material gas composed of a mixed gas of tetrachlorosilane and an inert gas is sprayed onto the molten aluminum F1 to cause a reaction on the spot. In comparison, it is possible to suppress a decrease in the temperature of molten aluminum or the reaction field. Therefore, according to this embodiment, a sufficiently high reaction rate can be achieved in the reduction reaction of the halogenated silane with molten aluminum.

  In the present embodiment, there is an advantage that silicon can be manufactured by a reaction apparatus having a relatively simple configuration. That is, in the conventional silicon manufacturing method using the gas atomizing method, an inert gas (atomizing gas) supply means for forming microdroplets, and a tetrachlorosilane gas brought into contact with the formed microdroplets The reaction apparatus provided with both of the supply means is required. On the other hand, in this embodiment, since silicon can be manufactured by spraying the raw material gas G1 on the molten aluminum F1, a mechanism for separately supplying the tetrachlorosilane gas to the reaction apparatus 3 is unnecessary.

  However, you may use the reaction apparatus which comprises the mechanism which supplies tetrachlorosilane gas and / or an inert gas to the reaction apparatus 3 separately. By separately supplying tetrachlorosilane gas into the reactor 3, the amount of high-pressure tetrachlorosilane supplied as part of the raw material gas can be reduced. From the viewpoint of obtaining a high reaction rate in the reactor 3, the temperatures of the tetrachlorosilane gas and the inert gas supplied separately are preferably 200 ° C. or higher. By adopting such a configuration and maintaining a high reaction rate, silicon suitable for a solar cell material can be manufactured without increasing the amount of aluminum remaining in the generated silicon.

  Further, the source gas is not necessarily a mixed gas of tetrachlorosilane and an inert gas, and may be tetrachlorosilane alone. By adopting such a configuration, the partial pressure of the tetrachlorosilane gas in the reaction field can be further increased, and a higher reaction rate can be achieved.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.

  For example, silicon melted by the melting device 25 may be solidified by cooling in the melting device 25.

Moreover, in the said embodiment, although the case where tetrachlorosilane was used as a halogenated silane was illustrated, it is not limited to this, In the halogenated silane shown by following formula (1), things other than tetrachlorosilane are used independently. Or two or more halogenated silanes represented by the following formula (1) may be used in appropriate combination.
SiH _n X _4-n (1)
[Wherein n is an integer of 0 to 3; X represents an atom selected from the group consisting of F, Cl, Br and I, respectively. When n is 0 to 2, X may be the same or different. ]

  Moreover, in the said embodiment, although the case where aluminum was used as a reducing metal was illustrated, it is not limited to this, One type selected from the group which consists of sodium, potassium, magnesium, calcium, and zinc is used independently. Alternatively, two or more selected from the group consisting of sodium, potassium, magnesium, calcium, zinc and aluminum may be used in appropriate combination. An aluminum-silicon alloy may be used as the reducing metal.

Moreover, in the said embodiment, as shown in FIG. 1, although the free fall method which sprays atomizing gas on the molten aluminum F1 flowed down from the molten metal accommodating part 1 was illustrated, you may employ | adopt gas atomizing methods other than this. . For example, a so-called confined method (Close-Coupled method) using an apparatus having an atomizing mechanism in which a molten aluminum supply port and an atomizing gas supply port are provided close to each other can be used. Also, a so-called Updraft atomizer device may be used to discharge molten aluminum upward. When molten aluminum is discharged upward or downward, tetrachlorosilane gas may be supplied in the same direction as the direction in which the molten aluminum moves, and it faces the direction in which the molten aluminum moves. Then, the tetrachlorosilane gas may be supplied countercurrently. Note that the atomized gas may be a liquid or a supercritical fluid depending on the temperature condition and the pressure condition before being discharged from a supply port such as a nozzle.

It is a schematic block diagram which shows the structure of the manufacturing apparatus of the silicon | silicone which concerns on one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Molten metal accommodating part, 2 ... Raw material gas discharge part, 3 ... Reaction apparatus, 3a ... Cylindrical part, 3b ... Reduced diameter part, 3c ... Silicon particle discharge port, 3d ... Solid-air mixed fluid outlet, 3d ... Gas outlet, 5a, 5b, 5c, 6a, 6b, 6c ... Solid-gas separator, 10 ... Manufacturing equipment, 11 ... Heater, DESCRIPTION OF SYMBOLS 15 ... Airtight container, 21 ... Coating layer, 23 ... Storage apparatus, 23 ... Melting apparatus, 25 ... Melting apparatus, 27 ... Solidification apparatus, F1 ... Molten aluminum, G1 ... source gas, L9 ... first pipe, L11, L13 ... second pipe, L23 ... third pipe.

Claims (5)

An apparatus for producing silicon having a reactor for obtaining silicon particles by reducing halogenated silane with a molten reducing metal,
A silicon manufacturing apparatus, wherein at least a part of an inner surface of the manufacturing apparatus is covered with at least one of a silicon layer and a fluorine resin layer. The reaction apparatus for obtaining silicon particles by reducing a halogenated silane with a molten reducing metal; and
The mixture containing the silicon particles, the silane halide and the reducing metal halide supplied from the reaction apparatus is separated into a gas containing the halogenated silane and the reducing metal halide and the silicon particles. A solid-gas separation device,
A storage device for temporarily storing the silicon particles supplied from the solid-gas separation device;
A first pipe connecting the reactor and the solid-gas separator;
A second pipe connecting the solid-gas separation device and the storage device;
A third pipe for taking out the silicon particles stored in the storage device from the storage device,
The inner surface of at least one of the solid-gas separation device, the storage device, the first pipe, the second pipe, and the third pipe is covered with at least one of the silicon layer or the fluorine-based resin layer, The silicon manufacturing apparatus according to claim 1.   The silicon production apparatus according to claim 2, wherein the solid-gas separation device is a cyclone.   The silicon manufacturing apparatus according to claim 2, further comprising a melting device for melting the silicon particles. The silicon manufacturing apparatus according to claim 4, further comprising a solidification device that cools and solidifies the silicon particles melted by the melting device.

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