JP2010030825A - Method and apparatus for producing silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for producing silicon in which, in the reaction of tetrachlorosilane with a molten metal, a sufficiently high reaction rate is obtained. <P>SOLUTION: The method for producing silicon from tetrachlorosilane includes a reduction step where liquid tetrachlorosilane and a molten metal are allowed to collide with each other in a reactor and the tetrachlorosilane is reduced to obtain silicon. The method for producing silicon may further include a discharge step of discharging slurry comprising silicon particles obtained through the reduction step and unreacted liquid tetrachlorosilane from the reactor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method and apparatus for producing silicon from tetrachlorosilane.

  As a method for producing semiconductor grade silicon, the Siemens method in which trichlorosilane and hydrogen are reacted at a high temperature is mainly employed. In this method, extremely high-purity silicon can be obtained, but it is said that the cost is high and further cost reduction is difficult.

  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. Solar cell silicon is mainly made of non-standard semiconductor grade silicon. Thus, in order to further reduce the power generation cost, it is desired to secure a low-cost silicon raw material.

  As a silicon production method replacing the Siemens method, for example, Patent Documents 1 and 2 below disclose a method of producing silicon by reducing a halogenated silane with a reducing agent (for example, molten metal).

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

  By the way, as described in Patent Document 2, a gas atomizing method in which a gas is blown onto a flowing molten metal is known as a method for forming fine droplets of molten metal. In this gas atomizing method, it is common to use an inert gas as a gas (hereinafter referred to as “atomizing gas”) sprayed on the molten metal.

  However, the present inventor has found that there is room for improvement in the following points when the gas atomizing method using an inert gas is employed in the production of silicon. That is, a large amount of inert gas used for atomization of the molten metal remains in the reaction field where the chlorosilane gas is reduced and silicon is deposited. If a large amount of inert gas remains in the reaction field, it becomes difficult to sufficiently increase the partial pressure of the chlorosilane gas, and sufficient reactivity cannot be obtained.

  This invention is made | formed in view of the said subject, and it aims at providing the manufacturing method and manufacturing apparatus of silicon which show a sufficiently high reaction rate in reaction of tetrachlorosilane and a molten metal.

  The silicon production method according to the present invention is a method for producing silicon from tetrachlorosilane, and includes a reduction step of colliding liquid tetrachlorosilane and molten metal in a reactor to reduce tetrachlorosilane to obtain silicon. .

  In the silicon manufacturing method according to the present invention, liquid tetrachlorosilane and molten metal collide with each other. The liquid tetrachlorosilane colliding with the molten metal not only refines the molten metal by the energy of collision, but also refines the molten metal by rapid volume expansion accompanying vaporization. That is, liquid tetrachlorosilane is vaporized by the heat of the molten metal, the heat of the reaction field, and the heat of reaction in the reactor, and the volume rapidly expands. This promotes refinement of the molten metal.

  Thus, according to the silicon manufacturing method of the present invention, the molten metal can be sufficiently miniaturized without using an inert gas. Therefore, the partial pressure of the tetrachlorosilane gas in the reaction field can be made sufficiently high. In addition, according to the silicon production method of the present invention, microdroplets are formed by collision between liquid tetrachlorosilane and molten metal, and at the same time, tetrachlorosilane and molten metal microdroplets efficiently contact each other. To do. Therefore, a sufficiently high reaction rate can be achieved in the reaction between the molten metal and tetrachlorosilane.

  The method for producing silicon according to the present invention may further include a discharge step of discharging a slurry containing silicon particles obtained through the reduction step and unreacted liquid tetrachlorosilane from the reactor. . By adopting such a configuration, since it is not necessary to vaporize the entire amount of liquid tetrachlorosilane supplied to the reactor, the temperature in the reactor can be set relatively low, and power consumption can be reduced.

  Further, the silicon production method according to the present invention includes a separation step of separating liquid tetrachlorosilane from the slurry, and a return step of returning the liquid tetrachlorosilane obtained through the separation step to the upstream side of the reactor. May be further provided. By adopting such a configuration, the liquid tetrachlorosilane separated and recovered in the collision with the molten metal in the reduction process can be reused. If the tetrachlorosilane to be separated and recovered is a liquid, the pressure can be increased relatively easily to a pressure suitable for colliding with the molten metal.

  A silicon production apparatus according to the present invention is for producing silicon from tetrachlorosilane, a reactor for obtaining silicon by colliding liquid tetrachlorosilane and molten metal and reducing tetrachlorosilane, and a reactor. A tetrachlorosilane supplying means for supplying liquid tetrachlorosilane and a molten metal supplying means for supplying molten metal into the reactor are provided.

  In the silicon manufacturing apparatus according to the present invention, liquid tetrachlorosilane and molten metal collide with each other. The liquid tetrachlorosilane colliding with the molten metal not only refines the molten metal by the energy of collision, but also refines the molten metal by rapid volume expansion accompanying vaporization. That is, the liquid tetrachlorosilane is vaporized by the heat of the molten metal, the heat of the reaction field, and the reaction heat in the reactor and rapidly expands in volume, thereby promoting the refinement of the molten metal.

  Thus, according to the silicon manufacturing apparatus of the present invention, the molten metal can be sufficiently miniaturized without using an inert gas. Therefore, the partial pressure of the tetrachlorosilane gas in the reaction field can be made sufficiently high. In addition, according to the silicon manufacturing apparatus of the present invention, microdroplets are formed by collision of liquid tetrachlorosilane and molten metal, and at the same time, tetrachlorosilane and molten metal microdroplets efficiently contact each other. To do. Therefore, a sufficiently high reaction rate can be achieved in the reaction between the molten metal and tetrachlorosilane.

  The silicon production apparatus according to the present invention may further include a discharge means for discharging a slurry containing silicon particles generated in the reactor and unreacted liquid tetrachlorosilane from the reactor. By adopting such a configuration, since it is not necessary to vaporize the entire amount of liquid tetrachlorosilane supplied to the reactor, the temperature in the reactor can be set relatively low, and power consumption can be reduced.

  The silicon production apparatus according to the present invention includes a separation unit that separates liquid tetrachlorosilane from the slurry discharged from the reactor, and the liquid tetrachlorosilane separated by the separation unit is returned upstream of the reactor. It is preferable to further include a return means. By adopting such a configuration, the liquid tetrachlorosilane separated and recovered in the collision with the molten metal in the reactor can be reused. If the tetrachlorosilane to be separated and recovered is a liquid, the pressure can be increased relatively easily to a pressure suitable for colliding with the molten metal.

  In the present invention, the molten metal is preferably aluminum. When aluminum is used as the molten metal, there is an advantage that high-purity silicon is easily obtained. Even if aluminum remains in the generated silicon particles or on the surface thereof, the aluminum can be removed relatively easily by dissolution or segregation with acid or alkali.

  According to the present invention, a sufficiently high reaction rate can be achieved in the reaction between tetrachlorosilane and molten metal.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

<First Embodiment>
The silicon manufacturing method according to the first embodiment manufactures silicon using molten aluminum as a molten metal.

By bringing molten aluminum and liquid tetrachlorosilane into contact with each other, a reduction reaction represented by the following formula (A) proceeds to produce silicon.
3SiCl ₄ + 4Al → 3Si + 4AlCl ₃ (A)

  The configuration of the silicon manufacturing apparatus 10 according to the first embodiment and the operating conditions thereof will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram showing the configuration of the silicon manufacturing apparatus according to the present embodiment. FIG. 2 is an enlarged view showing a mechanism for causing liquid tetrachlorosilane and molten aluminum to collide with each other in the silicon manufacturing apparatus 10.

  1 includes a molten metal container (molten metal supply means) 1, a liquid tetrachlorosilane injection unit 2, a reactor 3, a solid-gas separator 5, a tank 21 for storing liquid tetrachlorosilane, a liquid tetra A line L1 for supplying chlorosilane to the injection unit 2 and a pump 22 for pressurizing liquid tetrachlorosilane are provided.

  In the present embodiment, the tetrachlorosilane supply unit is configured by the liquid tetrachlorosilane injection unit 2, the tank 21, the line L1, and the pump 22. Further, a mechanism for causing liquid tetrachlorosilane and molten aluminum to collide with each other is constituted by the nozzle 1a of the molten metal container 1 and the liquid tetrachlorosilane injection unit 2 described later.

  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. As shown in FIG. 2, a nozzle 1 a extending into the reactor 3 is provided at the bottom of the molten metal container 1, and a trickle F of molten aluminum flows down from the nozzle 1 a in the vertical direction. When the molten aluminum is accommodated in the molten metal container 1 in this manner, the molten aluminum can be stably flowed into the reactor 3 from the nozzle 1a, and silicon can be produced 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 nozzle 1a 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 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.

  The temperature in 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 the present embodiment, it is usually 700-1300 degreeC, Preferably it is 700-1200 degreeC, More preferably, it is 700-1000 degreeC. The temperature of the nozzle 1a is preferably about 700 to 1000 ° C.

  The liquid tetrachlorosilane injection part 2 is for injecting the liquid tetrachlorosilane supplied from the tank 21 through the line L1 toward the trickle F of molten aluminum, as shown in FIG. The liquid tetrachlorosilane injection unit 2 includes a nozzle 2a that injects liquid tetrachlorosilane from its periphery toward a trickle F of molten aluminum. By injecting a liquid stream L composed of liquid tetrachlorosilane (hereinafter referred to as “liquid tetrachlorosilane stream L”) onto a fine stream F of molten aluminum and causing the liquid tetrachlorosilane stream L and the molten aluminum to collide, A minute droplet P is formed.

  Thus, as a specific embodiment of the present invention, the collision between the liquid tetrachlorosilane and the molten metal is performed by ejecting the liquid tetrachlorosilane and the molten metal from the nozzles, respectively. The liquid tetrachlorosilane flow L colliding with the molten aluminum trickle F not only physically refines the molten aluminum, but also refines the molten aluminum by rapid volume expansion accompanying vaporization.

  From the viewpoint of obtaining high-purity silicon particles, the tetrachlorosilane used in the present embodiment preferably has a purity of 99.99% by mass or more, more preferably 99.999% by mass or more. More preferably, it is 9999 mass% or more.

  The liquid tetrachlorosilane to be injected into the molten aluminum trickle F is preferably injected at a pressure of 1 to 150 MPa, more preferably 5 to 100 MPa, and still more preferably 10 to 100 MPa. If the pressure at which liquid tetrachlorosilane is injected is less than 1 MPa, the formation of molten aluminum microdroplets P tends to be insufficient and the reaction represented by the above formula (A) tends to be insufficient. . On the other hand, in order to inject liquid tetrachlorosilane at a pressure exceeding 150 MPa, it is necessary to use various devices with high pressure resistance, and the cost tends to increase.

  The liquid tetrachlorosilane pressurizing pump 22 is not particularly limited as long as the liquid tetrachlorosilane can be increased to the target pressure. Specific examples of the pump 22 include a plunger pump and a diaphragm pump.

  Tetrachlorosilane has a property of corroding a metal material. In order to suppress metal corrosion caused by tetrachlorosilane, the nozzle 2a may be made of a member made of alumina, silicon carbide, silicon nitride, quartz, mullite, or carbon, or a member formed of a member coated with the above material. preferable.

  As shown in FIG. 1, the reactor 3 includes a cylindrical portion 3a extending in the vertical direction, and a reaction field in which the reaction represented by the above formula (A) proceeds is formed in the cylindrical portion 3a. By spraying liquid tetrachlorosilane from the nozzle 2a toward the trickle F, molten aluminum microdroplets P are formed, and at the same time, the tetrachlorosilane and the microdroplets P come into contact with each other. The reduction reaction (formula (A)) proceeds (reduction step).

As shown 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. From the viewpoint of productivity, the unit time supplied to the reaction field The ratio (M ₁ / M ₂ ) between the number of moles of tetrachlorosilane M ₁ and the number of moles M ₂ of molten aluminum supplied is preferably 0.75-20, more preferably 0.75-10. Preferably, it is 0.75-7.5. When the value of M 1 _/ M ₂ is less than 0.75, there is a tendency that the progress of the reaction becomes insufficient, while when it exceeds 20, there is a tendency that the amount of tetrachlorosilane which does not contribute to the reaction increases.

  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.

  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 is not more than ppm.

  The reactor 3 includes a reduced diameter portion 3b provided at a lower portion thereof and having an Si particle discharge port 3c for discharging silicon particles at the lower end while decreasing the inner diameter as going downward. A gas discharge port 3d for discharging aluminum chloride (gas) generated by the reaction, unreacted tetrachlorosilane (gas), and fine silicon particles is provided at a substantially intermediate position in the vertical direction of the reduced diameter portion 3b. It has been.

  The reduced diameter portion 3b provided at the lower portion of the reactor 3 functions as a first-stage solid-gas separator. A heater (not shown) is provided around the reduced diameter portion 3b so that the internal temperature can be adjusted. By maintaining the temperature inside the reduced diameter portion 3b at a temperature at which aluminum chloride (sublimation point: 180 ° C.) does not precipitate, the silicon particles and the gas are separated. Specifically, it is preferable to adjust the temperature inside the reduced diameter portion 3b to be 200 ° C. or higher. When the temperature inside the reduced diameter portion 3b is lower than 200 ° C., aluminum chloride tends to precipitate in the reduced diameter portion 3b and easily mix into the silicon particles.

  The gas discharged from the gas discharge port 3d is supplied to the solid-gas separator 5. The solid gas separator 5 functions as a second stage solid gas separator. The solid-gas separator 5 is for separating silicon particles present in the gas discharged from the gas discharge port 3d. It is preferable to adjust the temperature inside the solid-gas separator 5 to be 200 ° C. or higher. As a suitable example of the solid gas separator 5, a heat insulation cyclone type solid gas separator can be exemplified.

  The gas discharged from the solid gas separator 5 is supplied to the solid gas separator 8. The solid gas separator 8 functions as a third-stage solid gas separator. The solid gas separator 8 is for removing aluminum chloride contained in the gas from the solid gas separator 5. By maintaining the temperature in the solid-gas separator 8 at a temperature at which aluminum chloride precipitates but tetrachlorosilane (boiling point: 57 ° C.) does not condense, the precipitated aluminum chloride (solid) is removed. Specifically, it is preferable to maintain the internal temperature of the solid-gas separator 8 at 60 to 170 ° C. (more preferably 70 to 100 ° C.). When the temperature inside the solid-gas separator 8 is lower than 60 ° C., tetrachlorosilane is condensed in the solid-gas separator 8 and the amount of tetrachlorosilane gas to be recycled tends to be insufficient. On the other hand, when the temperature inside the solid-gas separator 8 is higher than 170 ° C., aluminum chloride is not sufficiently precipitated, and the content of aluminum chloride in the recycled tetrachlorosilane gas tends to be high.

  It is preferable that the solid-gas separator 8 includes a baffle plate (not shown) therein. By providing the baffle plate inside, the inner surface area of the solid-gas separator 8 is increased and aluminum chloride is efficiently precipitated, and the content of aluminum chloride in the gas can be sufficiently reduced. The internal surface area of the solid-gas separator 8 is preferably 5 times or more the device surface area of the solid-gas separator 8.

  The gas from which aluminum chloride has been removed in the solid-gas separator 8 is discharged from the solid-gas separator 8 through a line L7. The tetrachlorosilane gas discharged from the solid-gas separator 8 may be liquefied and then returned to the tank 21 for recycling. Before returning to the tank 21, it may be purified by distillation.

  Thus, the silicon manufacturing apparatus 10 according to the present embodiment includes the reduced diameter portion 3b as the first-stage solid-gas separator, and the solid-gas separator 5 as the second-stage solid-gas separator, Further, a solid-gas separator 8 is provided as a third-stage solid-gas separator. By adopting such a configuration, unreacted tetrachlorosilane can be efficiently recovered and reused. The number of stages of the solid-gas separator is not particularly limited. For example, the reduced diameter portion 3b and the solid-gas separator 8 may be connected without using the solid-gas separator 5, or the solid-gas separator may be connected. Four or more stages may be provided. In addition, when using a reactor that does not include the gas discharge port 3d, a solid-gas separator 5 or the like may be installed downstream of the Si particle discharge port 3c.

  According to the silicon manufacturing method and the manufacturing apparatus according to the present embodiment, the following effects can be obtained. That is, in this embodiment, the liquid tetrachlorosilane flow L and the molten aluminum trickle F collide with each other. The liquid tetrachlorosilane colliding with the trickle F not only refines the molten aluminum by the energy of the collision, but also refines the molten aluminum by rapid volume expansion accompanying vaporization. That is, the liquid tetrachlorosilane is vaporized by the heat of molten aluminum, the heat of the reaction field, and the heat of reaction in the reactor 3, and the volume rapidly expands. This promotes refinement of the molten aluminum.

  Therefore, according to this embodiment, molten aluminum can be sufficiently refined without using an inert gas. Therefore, the partial pressure of the tetrachlorosilane gas in the reaction field can be sufficiently increased. Further, according to the present embodiment, the liquid droplets of tetrachlorosilane and the trickle F of molten aluminum collide with each other to form microdroplets P, and at the same time, tetrachlorosilane and microdroplets P efficiently contact each other. . Therefore, a sufficiently high reaction rate can be achieved in the reaction between molten aluminum and tetrachlorosilane.

  Moreover, according to this embodiment, there exists an advantage that silicon can be manufactured with the reactor of a comparatively simple structure. That is, in the conventional silicon manufacturing method using the gas atomizing method, an inert gas (atomizing gas) supplying means for forming microdroplets, and tetrachlorosilane to be brought into contact with the formed microdroplets A reactor with both gas supply means is required. On the other hand, according to the present embodiment, silicon can be produced by injecting the liquid tetrachlorosilane flow L onto the molten aluminum trickle F, so that tetrachlorosilane gas is separately added as in the silicon production apparatus 10 shown in FIG. A production apparatus that does not have a mechanism for feeding to the reactor 3 can be used. However, you may use the manufacturing apparatus which comprises the mechanism which supplies tetrachlorosilane gas to the reactor 3 separately.

<Second Embodiment>
1st Embodiment mentioned above assumes the case where silicon is manufactured by vaporizing the whole quantity of the liquid tetrachlorosilane supplied in the reactor 3, However, A part of liquid tetrachlorosilane supplied in the reactor is used. Vaporization may be performed and unreacted tetrachlorosilane may be recovered in a liquid state. FIG. 3 is a schematic diagram showing a silicon production apparatus suitable for recovering unreacted liquid tetrachlorosilane from the reactor.

3 includes a molten metal storage unit 1, a liquid tetrachlorosilane injection unit 2, a reactor 23, a solid-liquid separator (separation means) 25, a filter 26, a dryer 27, an AlCl ₃ removal device 28, A tank 21 and a pump 22 are provided.

  The silicon production apparatus 20 should just set the temperature of the reactor 23 low compared with the temperature of the reactor 3 of the said 1st Embodiment, Specifically, the temperature in the reactor 23 is 0-50 degreeC ( More preferably, the temperature may be 0 to 30 ° C. For this reason, it is not always necessary to install a heater around the reactor 23. Or even if it installs a heater, there exists an advantage that power consumption can be reduced. The silicon manufacturing apparatus 20 is the same as the silicon manufacturing apparatus 10 of the first embodiment except that the temperature condition of the reactor 23 and the recovery mechanism of the generated silicon particles and unreacted tetrachlorosilane are different. It has the composition of. Hereinafter, the recovery mechanism of the silicon manufacturing apparatus 20 will be mainly described with reference to FIG.

  The silicon production apparatus 20 includes a reactor 23 having a slurry discharge port 23c for discharging a slurry containing silicon particles, aluminum chloride particles and unreacted liquid tetrachlorosilane. The reactor 23 includes a cylindrical portion 23a that extends in the vertical direction, and a reduced diameter portion 23b that is provided at the lower portion of the cylindrical portion 23a and that has an inner diameter that decreases as it goes downward and has a slurry discharge port 23c at the lower end. The slurry in the reactor 23 is discharged through the slurry discharge port 23c and the line L21 connected thereto (discharge step). In the present embodiment, the slurry discharge port 23c and the line L21 constitute a discharge unit.

  The slurry discharged from the reactor 23 contains silicon particles generated in the reactor 23 and aluminum chloride particles by-produced as solids. Since aluminum chloride has low solubility in liquid tetrachlorosilane, it is present in the slurry as a solid content like the silicon particles.

  The solid-liquid separator 25 is for separating liquid tetrachlorosilane from the slurry supplied through the line L21. By introducing the slurry into the solid-liquid separator 25, the liquid content (liquid tetrachlorosilane) and the solid content (silicon particles and aluminum chloride particles) contained in the slurry are separated (separation step). FIG. 3 shows an apparatus for solid-liquid separation by natural sedimentation as the solid-liquid separator 25, but the solid-liquid separation method is not particularly limited. For example, in addition to natural sedimentation, ultrafiltration and centrifugation are performed. A method based on the above may be applied. What is necessary is just to select suitably the apparatus which can implement these methods as the solid-liquid separator 25. FIG.

  The liquid tetrachlorosilane separated by the solid-liquid separator 25 is returned to the tank 21 through the line L22. A filter 26 is disposed in the middle of the line L22. Liquid tetrachlorosilane that has been filtered by the filter 26 and from which the remaining solid content has been sufficiently removed is returned to the tank 21 (returning step). The liquid tetrachlorosilane supplied to the tank 21 is pressurized by the pump 22 and used again for collision with the trickle F of molten aluminum. In this embodiment, a return means is comprised by the line L22 and the pump (not shown) etc. which are arrange | positioned in the middle.

  If the separated and recovered tetrachlorosilane is a gas, a step of liquefying it before returning it to the tank 21 is required. In this embodiment, the liquid tetrachlorosilane recovered without performing such a step is stored in the tank 21. Can be returned. Further, when tetrachlorosilane is liquid, there is an advantage that the pressure can be increased relatively easily to a pressure suitable for colliding with molten aluminum. Prior to supplying the liquid tetrachlorosilane to the tank 21, the liquid tetrachlorosilane may be purified by distillation.

  On the other hand, the slurry in which the solid content is concentrated by the processing in the solid-liquid separator 25 is supplied to the dryer 27 through the line L23. In the dryer 27, the concentrated slurry is dried to remove the remaining liquid tetrachlorosilane (drying step). Since liquid tetrachlorosilane has a high vapor pressure, it can be evaporated even if the drying temperature in the dryer 27 is relatively low, but it is above the boiling point of tetrachlorosilane and below the sublimation point of aluminum chloride. Is preferred.

The solid content discharged from the dryer 27 is introduced into the AlCl ₃ removing device 28 through the line L25. The aluminum chloride is vaporized and removed by heating the solid content above the sublimation point of aluminum chloride in the AlCl ₃ removal device 28 (de-AlCl ₃ step). Aluminum chloride (gas) is discharged from a line L26 connected to the AlCl ₃ removing device 28, while silicon particles are recovered from the line L27. From the viewpoint of efficiently vaporizing the aluminum chloride particles, the treatment in the AlCl ₃ removal device 28 may be performed under reduced pressure. The treatment under reduced pressure may be performed from the stage of the dryer 27.

  The tetrachlorosilane discharged from the dryer 27 is supplied to the upstream side of the filter 26 in the line L22 through the line L24, and is introduced into the tank 21 through the line L22.

Here, the case where a part of the liquid tetrachlorosilane is recovered by the separation process by the solid-liquid separator 25 prior to the treatment in the AlCl ₃ removing device 28 is illustrated, but the separation process by the solid-liquid separator 25 is performed. Alternatively, the entire amount of liquid tetrachlorosilane may be removed by a drying process using the dryer 27. Alternatively, the slurry discharged from the reactor 23 may be directly introduced into the AlCl ₃ removal device 28 without performing both the drying step and the separation step. In this case, silicon particles and a mixture of tetrachlorosilane and aluminum chloride are recovered from the AlCl ₃ removal device 28. By installing a device for recovering tetrachlorosilane from the mixture at the subsequent stage of the AlCl ₃ removal device 28, it becomes possible to reuse the tetrachlorosilane.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said 1st and 2nd embodiment.

  In the above embodiment, the case where aluminum is used as the molten metal is exemplified, but the molten metal is not limited to this, and one type selected from the group consisting of sodium, potassium, magnesium, calcium and zinc is used alone. Alternatively, two or more selected from the group consisting of sodium, potassium, magnesium, calcium, zinc and aluminum may be used in appropriate combination. Further, an alloy of aluminum and silicon may be used as the molten metal.

  Moreover, in the said embodiment, although the case where molten aluminum was discharged toward the downward direction from the nozzle 1a was illustrated, you may make it discharge upwards or a horizontal direction.

  Moreover, in the said embodiment, as shown in FIG. 2, although the case where liquid tetrachlorosilane was injected diagonally from the circumference toward the trickle F of molten aluminum was illustrated, liquid tetrachlorosilane is with respect to the trickle F of molten aluminum. Thus, they may be jetted opposite to each other, or may be jetted so that the angle formed with the direction of the trickle F is vertical.

It is a schematic block diagram which shows suitable embodiment of the silicon manufacturing apparatus which concerns on this invention. It is sectional drawing which shows the structure of the injection mechanism with which the silicon manufacturing apparatus shown in FIG. It is a schematic block diagram which shows other embodiment of the silicon manufacturing apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Molten metal accommodating part, 1a ... Nozzle for molten metal, 2 ... Liquid tetrachlorosilane injection part, 2a ... Nozzle for liquid tetrachlorosilane injection, 3 ... Reactor, 3a ... Cylindrical part of reactor, 3b ... Reactor Reduced diameter portion (solid gas separator), 3c ... Si particle outlet, 3d ... gas outlet, 5,8 ... solid gas separator, 10,20 ... silicon manufacturing apparatus, 11,13 ... heater, 15 ... sealed Container, 21 ... Tank, 22 ... Liquid tetrachlorosilane pressurizing pump, 23 ... Reactor, 23a ... Reactor cylindrical part, 23b ... Reducing diameter part of reactor, 23c ... Slurry outlet, 25 ... Solid-liquid separator, 26 ... filter, 27 ... dryer, 28 ... AlCl ₃ remover, F ... molten metal trickle, L ... liquid tetrachlorosilane flow, P ... microdroplets.

Claims (7)

A method of producing silicon from tetrachlorosilane,
A silicon production method comprising a reduction step of colliding liquid tetrachlorosilane and molten metal in a reactor to reduce tetrachlorosilane to obtain silicon.   The silicon production method according to claim 1, further comprising a discharge step of discharging a slurry containing silicon particles obtained through the reduction step and the unreacted liquid tetrachlorosilane from the reactor.   The separation step of separating liquid tetrachlorosilane from the slurry, and the return step of returning the liquid tetrachlorosilane obtained through the separation step to the upstream side of the reactor are further provided. Silicon manufacturing method.   The silicon manufacturing method according to claim 1, wherein the molten metal is aluminum. An apparatus for producing silicon from tetrachlorosilane,
A reactor in which liquid tetrachlorosilane collides with molten metal and tetrachlorosilane is reduced to obtain silicon;
Tetrachlorosilane supply means for supplying liquid tetrachlorosilane into the reactor;
Molten metal supply means for supplying molten metal into the reactor;
A silicon manufacturing apparatus comprising:   The silicon manufacturing apparatus according to claim 5, further comprising discharge means for discharging a slurry containing silicon particles produced in the reactor and the unreacted liquid tetrachlorosilane from the reactor.   The silicon according to claim 6, further comprising separation means for separating liquid tetrachlorosilane from the slurry, and return means for returning the liquid tetrachlorosilane separated by the separation means to the upstream side of the reactor. Manufacturing equipment.

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