JP2010095433A - Method of manufacturing silicon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing silicon having higher productivity than that of a conventional method. <P>SOLUTION: The method of manufacturing silicon includes: a process which heats an aluminum particle whose surface is oxidized so that a mass fraction of oxygen of the whole particle may be 0.005% or more and 0.5% or less; and a process in which the heated aluminum particle and a halogenated silane shown by the following formula (1) are contacted together, thereby the halogenated silane is reduced: SiH<SB>n</SB>X<SB>4-n</SB>(1). In the formula, n is an integer of 0-3; X respectively show an atom chosen from a group consisting of F, Cl, Br and I. When n is 0-2, X may mutually be the same or different. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing silicon by reducing a halogenated silane with a metal. In particular, the present invention relates to a method for producing high-purity silicon suitable for the production of solar cells.

  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. However, in this method, extremely high-purity silicon can be obtained, but the cost is high and it is said that 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 to 3 below disclose a method for producing silicon by reducing a halogenated silane with a reducing agent (for example, molten metal).

For example, in the above reduction reaction, when tetrachlorosilane and aluminum come into contact with each other, a reaction represented by the following formula (A) proceeds, and silicon and aluminum trichloride are generated.
3SiCl ₄ + 4Al → 3Si + 4AlCl ₃ (A)

Here, in the method of obtaining silicon by reducing a halogenated silane with a metal, from the viewpoint of achieving high reaction efficiency, the metal is melted, and a shape having a large specific surface area, for example, fine droplets (liquid particles) and It is said that it is preferable (for example, refer patent documents 1-3). And after producing | generating a metal solid particle previously by a gas atomization method etc., the manufacturing method of the silicon which reheats the obtained metal solid particle, supplies it in a reactor, and makes a halogenated silane contact, and performs a reductive reaction It has been known.
Japanese Patent Laid-Open No. 2-64006 JP 2007-77007 A JP 2007-284259 A

  In the method of reheating aluminum particles produced in advance using a gas atomization method or the like and supplying them into the reactor, it has been found that the aluminum particles may be fused or fixed together during reheating of the aluminum particles. did. Coarse aluminum particles are formed when fusion or fixation of aluminum particles occurs. When the above-mentioned halogenated silane is reduced using coarse aluminum particles, the utilization rate of aluminum becomes extremely low, so that productivity tends to deteriorate.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing silicon that is more productive than conventional ones.

  As a result of intensive studies, the present inventors have found that aluminum particles (liquid and solid) whose surfaces have been oxidized so as to have a predetermined amount of oxygen are hardly fused or fixed to each other even at high temperatures, and individual particles are separated. The present invention was found out that it was easy to obtain the existing state.

The method for producing silicon according to the present invention comprises the steps of heating aluminum particles whose surfaces are oxidized so that the mass fraction of oxygen in the whole particles is 0.005% or more and 0.5% or less, and heated aluminum And a step of reducing the halogenated silane by bringing the particles into contact with the halogenated silane represented by the following formula (1).
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. ]

  According to the present invention, since the surfaces of the aluminum particles are oxidized, fusion and adhesion when the aluminum particles are in contact with each other in a heated state is hindered. If the mass fraction of oxygen in the entire aluminum particles is less than 0.005%, the surface of the aluminum particles is not sufficiently oxidized, and the particles are easily fused or fixed together at a high temperature. On the other hand, if the mass fraction of oxygen in the entire aluminum particles is more than 0.5%, the surface of the aluminum particles will be excessively oxidized, and although fusion and fixation at high temperatures will be hindered, The reaction represented by the formula (A) is greatly inhibited.

Here, the mass fraction of oxygen in the entire aluminum particles is determined by melting the aluminum particles in a graphite crucible in an inert carrier gas atmosphere and absorbing CO gas and CO ₂ gas generated by the reaction between oxygen and the graphite crucible with infrared rays. It is measured by analyzing by the method.

  It is also preferable to heat the aluminum particles to a melting point of aluminum or higher and bring the molten aluminum particles into contact with the halogenated silane. Thereby, the reduction reaction can be performed quickly. In addition, when the average particle size of the aluminum particles is as small as, for example, less than 200 μm, it is also preferable to contact the aluminum particles with the halogenated silane in a solid state. When the particle size is small, the reaction surface area is large even for a solid, and the reduction reaction can be performed quickly.

  Further, before the heating step, the aluminum particles to be heated in the heating step are blown into a chamber in which atomized gas containing oxygen and / or moisture is blown to molten aluminum, or atomized gas is blown to molten aluminum. It is preferable to further include a step obtained by supplying a gas containing oxygen and / or moisture. Thereby, the above-mentioned aluminum particles can be easily obtained.

  Further, before the heating step, the aluminum particles to be heated in the heating step are blown into a chamber in which atomized gas containing oxygen and / or moisture is blown to molten aluminum, or atomized gas is blown to molten aluminum. It is also preferable to further include a step of obtaining particles obtained by classifying particles obtained by supplying a gas containing oxygen and / or moisture.

  By classification, for example, coarse aluminum particles having an average particle diameter of more than 1000 μm can be reliably removed, and the utilization rate of aluminum is increased, so that the reduction of halogenated silane can be performed more efficiently. Furthermore, since the surface of the aluminum particles is oxidized, problems such as aggregation in the classification process are reduced, and the aluminum particles having a particle size suitable for the reaction represented by the above formula (A) are efficiently classified and selected. Can do.

The aluminum particles are preferably heated at a temperature increase rate of 10 ° C./second or more. Since the temperature is increased at a high speed in this manner, the further acceleration of the surface oxidation that proceeds by the reaction shown in the following formula (B) in the temperature increasing process for heating the aluminum particles can be suppressed. It becomes difficult to be disturbed.
4Al + 3O ₂ → 2Al ₂ O ₃ (B)

Moreover, it is preferable to heat said aluminum particle in inert gas atmosphere with a dew point of -20 degrees C or less. Thereby, since further promotion of the oxidation of the surface which progresses by the reaction formula shown by following formula (C), etc. can be suppressed, reaction with halogenated silane becomes difficult to be inhibited.
2Al + 3H ₂ O → Al ₂ O ₃ + 3H ₂ (C)

The aluminum particles are preferably heated in an atmosphere containing at least hydrogen gas. As a result, as shown in the following formula (D), a part of the oxidized surface of the aluminum particles is reduced, and aluminum capable of the reduction reaction shown in the above formula (A) is exposed on the surface of the aluminum particles. In addition, since the effect of promoting the contact with the halogenated silane can be estimated, it is preferable because silicon can be produced while maintaining particularly high reaction efficiency.
Al ₂ O ₃ + 3H ₂ → 2Al + 3H ₂ O (D)

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the silicon which can achieve high productivity 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. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

(First embodiment)
A first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. The silicon production method according to this embodiment uses tetrachlorosilane as an example of a halogenated silane, and produces silicon particles by reducing the tetrachlorosilane with aluminum. In this embodiment, first, aluminum particles having a desired particle size range are obtained and stored at room temperature in the aluminum particle production apparatus 10 shown in FIG. 1, and then the aluminum particles are used using the reaction apparatus 20 shown in FIG. And tetrachlorosilane are contacted to obtain silicon particles.

  FIG. 1 is a schematic configuration diagram showing a configuration of an apparatus for producing aluminum particles according to the present embodiment. An aluminum particle manufacturing apparatus 10 shown in FIG. 1 includes an atomizing device 8a, a classifier 9, a particle container 21, and a pipe (hereinafter referred to as “line” in some cases) for connecting them.

(Atomizing device 8a)
The atomizing device 8 a mainly includes a molten metal container 1, an atomizing gas injection unit 2, and an atomizing container 3.

(Molten metal storage)
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 nozzle 1a extending into the atomizing container 3 is provided at the bottom of the molten metal container 1, and a trickle F of molten aluminum flows down from the nozzle 1a in the vertical direction. If the molten aluminum is stored in the molten metal container 1 in this way, the molten aluminum can be stably flowed from the nozzle 1a into the atomizing vessel 3, and the aluminum particles are produced stably and continuously. There is an advantage that you can. 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 aluminum to be used 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. In addition, the purity of aluminum here is content (mass%) of Fe, Cu, Ga, Ti, Ni, Na, Mg, and Zn among the elements measured by the glow discharge mass spectrometry of raw material aluminum. It means a value obtained by subtracting the total from 100% by mass.

  The temperature in the molten metal accommodating part 1 is 700-1300 degreeC normally, Preferably it is 700-1200 degreeC, More preferably, it is 700-1000 degreeC.

  In order to allow the molten metal to flow out stably from the nozzle 1a, the temperature of the nozzle 1a is preferably about 700 to 1300 ° C. In order to ensure the temperature, it is preferable to install a nozzle heat retention device (not shown) such as a heater attached to the nozzle 1a in order to prevent the nozzle from being blocked.

(Atomized gas injection unit)
The atomizing gas injection unit 2 is supplied with an inert gas supplied through the line L1 and, if necessary, a gas containing oxygen and / or moisture supplied from the line L2 from the nozzle 1a of the molten metal containing unit 1. It is injected as an atomized gas G toward a trickle F of molten aluminum. The atomizing gas injection unit 2 includes a nozzle 2a that injects an atomizing gas G from its periphery toward a trickle F of molten aluminum flowing down. By spraying the atomizing gas G on the trickle F that flows down, micro droplets P of aluminum are formed. The structure in which molten aluminum is flowed downward and atomized is called a downdraft type, and the structure in which the nozzle 1a for flowing liquid aluminum and the nozzle 2a for injecting atomized gas are arranged apart from each other is free-falling. Called a type.

  In the present embodiment, argon and / or helium are suitable as the inert gas. From the viewpoint of obtaining high-purity silicon particles, the inert gas preferably has a purity of 99.9% by volume or more, more preferably 99.99% by volume or more, and 99.999% by volume or more. More preferably, it is more preferably 99.9995% by volume or more.

  In order to suitably oxidize the surface of the aluminum microdroplet P, oxygen and / or moisture are mixed with the atomizing gas G, or oxygen and / or moisture are contained in the atmospheric gas in the atomizing vessel 3 from the line L10, for example. It is preferable to supply the gas to be used. The gas containing oxygen and / or moisture can contain an inert carrier gas. Argon and / or helium are suitable as the inert gas. Oxygen and water mixed in the atomizing gas are blown onto the molten aluminum trickle F to generate and consume oxides as shown in the above formulas (B) and (C), and the surfaces of the microdroplets P are oxidized. The The same applies when oxygen and / or moisture are present in the atmospheric gas in the atomizing container 3.

The concentration of oxygen gas when oxygen is mixed with the atomizing gas G is preferably 0.1% by volume to 3% by volume. When water is mixed in the atomizing gas G, it is preferable to mix the degassing point so that the dew point of the atomizing gas is −100 ° C. to 0 ° C. In this case, it is preferable that the oxygen concentration in the atmospheric gas in the atomizing container 3 is 1% by volume or less, and the dew point of the atmospheric gas as the moisture content is −20 ° C. or lower.
On the other hand, when oxygen is not included in the atomizing gas G, oxygen and / or moisture may be supplied into the atomizing container 3 as an atmospheric gas. In this case, it is preferable that the oxygen concentration of the atmosphere is 0.1% by volume to 3% by volume, and the dew point of the atmosphere as the amount of water is −60 ° C. to 0 ° C.
Note that the present invention can also be implemented by supplying oxygen and / or moisture to the atomizing gas G and supplying oxygen and / or moisture to the atmospheric gas in the atomizing vessel 3.
When the amount of oxygen or moisture present in the atomizing gas or atmospheric gas is lower than the above range, the surface of the microdroplet P tends not to be sufficiently oxidized. On the other hand, when the amount of oxygen or moisture is higher than the above range, the surface oxidation proceeds considerably and tends to inhibit the progress of the reduction reaction of the above formula (A) in the subsequent stage.

  In this way, aluminum particles whose surfaces are oxidized so that the mass fraction of oxygen in the entire particles is 0.005% or more and 0.5% or less can be suitably produced. In addition, since the aluminum particles whose surfaces are oxidized are difficult to be fused or fixed to each other as will be described later, there is an effect that aluminum particles having a uniform particle diameter can be easily obtained at the time of atomization. Can be easily formed. In this step, it is preferable to produce aluminum particles having an average particle diameter of about 3 to 1000 μm.

  The temperature of the atomizing gas sprayed on the trickle F of molten aluminum is preferably 10 to 700 ° C, and more preferably 20 to 500 ° C. By increasing the temperature of the atomizing gas, atomization efficiency can be improved, that is, molten aluminum can be atomized with a smaller amount of atomizing gas.

  The pressure of the atomizing gas sprayed on the trickle F of molten aluminum is preferably 0.1 to 15 MPa, more preferably 1 to 10 MPa, and further preferably 2 to 10 MPa. If the pressure of the atomizing gas is less than 0.1 MPa, the formation of aluminum microdroplets P tends to be insufficient. On the other hand, in order to use the atomized gas exceeding 15 MPa, it is necessary to use various devices having high pressure resistance, and the cost tends to increase.

(Atomized container)
The atomizing container 3 includes a cylindrical part 3a that extends in the vertical direction and is disposed so as to surround the atomizing gas injection part 2, and atomization of molten aluminum is performed in the cylindrical part 3a. It is preferable to adjust the temperature in the atomizing container 3 so that it is usually 10 to 500 ° C, preferably 20 to 300 ° C. Further, the internal pressure of the atomized container is usually set to about atmospheric pressure, and it is preferable to adjust the pressure so that the pressure is about 0.03 MPa higher than atmospheric pressure.

  The fine droplets P formed by gas atomization are cooled when falling in the atomization container 3 to become solid, and a large amount of solid aluminum particles are obtained.

  The atomizing container 3 is provided with a reduced diameter portion 3b having an aluminum particle discharge port 3c for discharging aluminum particles at the lower end and decreasing in inner diameter as it goes downward. A gas discharge port 3d for discharging the atomized gas is provided at a substantially intermediate position in the vertical direction of the reduced diameter portion 3b.

  The reduced diameter portion 3b provided at the lower portion of the atomizing container 3 functions as a solid-gas separator.

(Classifier 9)
A classifier 9 is connected to the aluminum particle discharge port 3c. The classifier 9 classifies the produced aluminum particles and separates aluminum particles having a desired average particle size range. Here, the desired average particle diameter range is, for example, 3 to 1000 μm. The aluminum particles having a desired average particle diameter range are then transferred to a particle container 21 such as a hopper and are usually stored at normal temperature and in an inert atmosphere. Unfavorable coarse particles (for example, particle size of more than 1000 μm) and undesired fine particles (for example, particle size of less than 3 μm) are returned to the molten metal container after reduction for removing oxygen as necessary, for example. be able to.

  The classification means is not particularly limited, but a vibration sieving machine, a cyclone, or the like can be used. Further, in the classification step, it is preferable to carry out in an inert gas atmosphere in order to prevent further oxidation of the aluminum particles more than necessary, and in particular, high purity with a dew point adjusted to −20 ° C. or lower. An atmosphere using an argon gas is suitable. For example, an inert gas such as argon or helium may be supplied from the line L18 shown in FIG. In addition, when the aluminum particles prepared by the gas atomizing method have a sufficiently narrow particle size distribution and there are no coarse particles or fine powders, it is not necessary to perform classification and sorting, and the aluminum particles can be accommodated as they are. . In the present invention, since the aluminum particles whose surface is oxidized so that the mass fraction of oxygen in the whole aluminum particles is 0.005% or more and 0.5% or less are used, further aggregation at the time of classification is performed. It is possible to classify and sort efficiently.

(Particle container 21)
The particle storage unit 21 stores the aluminum particles classified and selected in advance in the classifier 9 so as to have a desired average particle size range in an inert gas atmosphere, and preheats the aluminum particles as necessary. it can. A heater 21a is provided around the particle storage portion 21 so that the temperature of the aluminum particles to be stored can be adjusted. An inert carrier gas is supplied to the particle container 21 via a line L20. As the inert carrier gas, argon gas is preferable.

  Next, the reaction apparatus 20 will be described with reference to FIG. The reactor 20 includes a particle feeder 200, a particle heater 26, a reactor 23, an exhaust gas cooler 29, a solid-gas separator 25, 28, a tetrachlorosilane pressure heating unit 27, and these connected to the particle storage unit 21. A pipe (hereinafter referred to as “line” in some cases) is connected.

(Particle feeder 200)
The particle supply unit 200 extracts aluminum particles from the particle storage unit 21 and supplies them quantitatively to the reactor via the particle heater 26. Examples of the particle feeder 200 include a screw feeder. Further, as the particle feeder 200, an inert carrier gas is supplied into the particle storage unit 21 to fluidize the aluminum particles, and the aluminum particles overflowed from the upper end of the overflow pipe inserted into the particle storage unit 21 are used. A means for supplying a fixed amount to the particle heater 26 is also suitable. In addition, an inert carrier gas is introduce | transduced via the line L23 as needed, and an aluminum particle is conveyed.

(Particle heater 26)
The particle heater 26 heats the aluminum particles supplied from the particle supplier 200 and falling in the pipe 26a. The means for heating the aluminum particles is not particularly limited. For example, a high-frequency heater, a microwave irradiation heater, an arc discharge heater or the like provided around the tube 26a is preferable. Furthermore, an electric heater provided outside the pipe 26a may be used. Here, the aluminum particles may be heated to the melting point or higher, or may be heated to a temperature lower than the melting point. In the case where the average particle diameter of the falling aluminum particles is relatively large, for example, 200 μm or more, it is preferable to form droplets by heating above the melting point of aluminum from the viewpoint of increasing the reaction rate of the reduction reaction. In the case where the average particle diameter of the falling aluminum particles is relatively small, for example, less than 200 μm, the reduction reaction proceeds sufficiently even when the aluminum particles are below the melting point of aluminum.

  In the present embodiment, since the aluminum particles whose surfaces are oxidized so that the mass fraction of oxygen in the whole particles is 0.005% or more and 0.5% or less, in the heating step, Fusion and adhesion are suppressed, and aluminum particles (solid or liquid) having a desired particle size range can be supplied into the reactor 23 in a state of being dispersed individually.

  Here, when the heating capability of the heating means is low, it takes time to raise the temperature of the aluminum particles. Therefore, if oxygen or moisture is present in the atmosphere, the surface of the aluminum particles may be further oxidized more than necessary, so that the reduction reaction represented by the reaction formula (A) in the reactor 23 described later is hindered. Tend. Therefore, it is preferable to heat the aluminum particles at a temperature rising rate of 10 ° C./second or more because it is possible to sufficiently suppress unnecessary acceleration of surface oxidation during heating of the aluminum particles. Moreover, in order to suppress further surface oxidation of the aluminum particles more than necessary, it is also preferable to heat the aluminum particles in an inert gas atmosphere, and in particular, a high-purity argon gas whose dew point is adjusted to −20 ° C. or less. An inert gas atmosphere using is preferable.

  Furthermore, it is preferable because an effect of sufficiently preventing oxidation of the surface of the aluminum particles more than necessary can be presumed by mixing hydrogen gas in an inert gas atmosphere and heating the aluminum particles. .

(Reactor)
The reactor 23 includes a cylindrical portion 23a 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 23a. A tube 26a is inserted in the upper center of the cylindrical portion 23a, and the aluminum particles P heated by the particle heater 26 are supplied into the reactor 23 through the tube 26a and fall in the reactor 23. Into the reactor 23, tetrachlorosilane is supplied from the supply port exemplified by the line L21, and an inert gas such as argon is supplied from the supply port exemplified by the line L22 as necessary. Tetrachlorosilane gas and inert gas are preheated as necessary by the tetrachlorosilane pressure heating unit 27 and the gas heating unit 217, respectively.

  From the viewpoint of obtaining high-purity silicon particles, the tetrachlorosilane introduced from the line L21 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.

  A heater 213 and a cooling means 214 are provided around the cylindrical portion 23a so that the temperature of the reaction field can be adjusted. There is no restriction | limiting in particular as a heater, For example, the system using fluids, such as gas temperature-adjusted previously, besides the direct method using high frequency heating, resistance heating, lamp heating etc. can be used. The temperature of the reaction field is usually adjusted to be 300 to 1200 ° C. (preferably 500 to 1000 ° C.). That is, the aluminum particles can be both solid and liquid. The reaction field pressure is usually adjusted to be 0.1 MPa or more.

  In such a reactor 23, the aluminum particles supplied via the pipe 26a react with the tetrachlorosilane gas supplied via the line L21 to cause a tetrachlorosilane reduction reaction (the above formula (A)). , Silicon particles are formed.

  In this embodiment, since the surface is oxidized so that the mass fraction of oxygen in the whole supplied aluminum particles is 0.005% or more and 0.5% or less, the aluminum particles are also contained in the reactor 23. Are not fused or fixed to each other, and individual aluminum particles can be dispersed and kept in an isolated state. Accordingly, coarse particles are not formed, the utilization rate of aluminum is increased, and productivity is high.

  In particular, in the classifier 9, when aluminum particles having an average particle diameter of 200 μm or more that are likely to inhibit the reduction reaction (the above formula (A)) are classified and removed, the reaction is performed using the particle heater 26 or the heater 313. The need for heating until the aluminum particles become liquid, that is, liquid droplets in the vessel 23 is reduced, and a very high utilization rate of aluminum can be achieved even with the solid particles. If the silicon reduction reaction is performed while the aluminum particles are solid in the reactor 23, it is possible to suppress the production of silicon due to the aluminum droplets adhering to the members and walls in the reactor 23. Stable productivity can be achieved.

Of course, the present invention can be implemented even when the aluminum particles are used as droplets. Even in this case, since the surface is oxidized, fusion of aluminum droplets and the like are suppressed, which is preferable.
It is also preferable to provide a line L210 for supplying an inert gas and / or a tetrachlorosilane gas that promotes the flow and suspension of aluminum particles at the upper part and / or the lower part of the reactor 23.

As in the above formula (A), the stoichiometric ratio of the number of moles of tetrachlorosilane and the number of moles of aluminum in the reaction is 3: 4, but from the viewpoint of productivity and the like, per unit time supplied to the reaction field The ratio (M ₁ / M ₂ ) of the number of moles M ₁ of tetrachlorosilane and the number of moles M ₂ supplied of aluminum particles is preferably 0.75-20, more preferably 0.75-10. 0.75 to 7.5 is more preferable. 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.

  In this embodiment, hydrogen gas can be supplied to the reaction field. Thereby, a part of the oxidized surface of the aluminum particle is reduced, and the effect of exposing the aluminum capable of the reduction reaction represented by the above formula (A) on the surface of the aluminum particle can be estimated. Reaction efficiency can be expected. The hydrogen gas can be supplied in addition to the inert gas and / or tetrachlorosilane supplied from the line L210. The concentration of the hydrogen gas to be supplied is not particularly limited, but is preferably several volume%. Thereby, even in the fused and fixed aluminum particles, since the reduction reaction of the above formula (A) sufficiently proceeds, it is not necessary to keep the temperature of the reaction field particularly high, so that an inexpensive manufacturing apparatus can be used. This is preferable because energy costs can be reduced.

  The reactor 23 includes a reduced diameter portion 23b having a particle discharge port 23c for discharging the silicon particles generated at the lower end and the inner diameter of the reactor 23 at the lower end thereof. A gas discharge port 23d for discharging the atomized gas is provided at a substantially intermediate position in the vertical direction of the reduced diameter portion 23b. The silicon particles discharged from the particle discharge port 23c are preferably used as a raw material for solar cells, for example.

The reduced diameter part 23b provided in the lower part of the reactor 23 functions as a 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 23b at a temperature at which AlCl ₃ (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 23b to be 200 ° C. or higher. If lower than 200 ° C. The internal temperature of the reduced diameter portion 23b, AlCl ₃ is deposited in a reduced diameter portion 23b, it tends to be easily incorporated into silicon particles.

(Exhaust gas cooler 29)
The gas discharged from the gas discharge port 23d is supplied to the exhaust gas cooler 29 via the line L23. The exhaust gas cooler 29 is for cooling the gas discharged from the gas discharge port 23d. The temperature inside the exhaust gas cooler 29 is preferably adjusted to be 200 ° C. or higher as in the reduced diameter portion 23b. Preferable examples of the exhaust gas cooler 29 include a multi-tube heat exchanger that uses a heat medium, a double-tube heat exchanger, or a cooler that directly sprays a cooling medium to exhausted gas. . As the cooling medium, tetrachlorosilane discharged from a solid-gas separator 28 described later can be used. Although the exhaust gas cooler 29 is disposed in the line L23, it may be installed in the line L24 as necessary, or a cooling means may be provided to the line L23 itself to omit the exhaust gas cooler. An example of the cooling means is a jacket using a heat medium. Further, a cooling medium may be introduced into the reactor 23 in order to cool the gas discharged from the gas discharge port 23d.

(Solid gas separator 25)
The gas discharged from the gas discharge port 23d is supplied to the solid-gas separator 25 via the exhaust gas cooler 29 arranged in the line L23 or the path of the line L23. The solid gas separator 25 functions as a second stage solid gas separator. The solid-gas separator 25 is for separating fine silicon particles (solid) present in the gas discharged from the gas discharge port 23d. It is preferable to adjust the temperature inside the solid-gas separator 25 so as to be 200 ° C. or higher, similarly to the reduced diameter portion 23b. As a suitable example of the solid gas separator 25, a heat insulation cyclone type solid gas separator can be exemplified.

(Solid gas separator 28)
The gas discharged from the solid gas separator 25 is supplied to the solid gas separator 28 via a line L4. The solid gas separator 28 functions as a third-stage solid gas separator. The solid gas separator 28 is for removing AlCl ₃ contained in the gas from the solid gas separator 25. By maintaining the temperature in the solid-gas separator 28 at a temperature at which AlCl ₃ (sublimation point of AlCl ₃ : 180 ° C.) precipitates but SiCl ₄ (boiling point: 57 ° C.) does not condense, the precipitated AlCl ₃ (solid ) Is removed. Specifically, it is preferable to maintain the temperature inside the solid-gas separator 28 at 60 to 170 ° C. (more preferably 70 to 100 ° C.). When the temperature inside the solid-gas separator 28 is lower than 60 ° C., SiCl ₄ also condenses in the solid-gas separator 28 and handling of the recovered aluminum chloride tends to be complicated. On the other hand, when the temperature inside the solid-gas separator 28 is higher than 170 ° C., the precipitation of AlCl ₃ becomes insufficient, the content of AlCl _{3 in} the recycled tetrachlorosilane gas becomes high, and the handling becomes complicated. Tend.

The solid-gas separator 28 is preferably provided with a baffle plate (not shown) therein. By providing the baffle plate inside, the inner surface area of the solid-gas separator 28 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 separator 28 is preferably 5 times or more the device surface area of the solid-gas separator 28.

The gas that has been subjected to the removal process of AlCl _{3 in} the solid-gas separator 28 is discharged from the solid-gas separator 28 through the line L27. When unreacted tetrachlorosilane gas, inert gas, etc. and a small amount of aluminum chloride coexist in the gas, the inert gas is separated, and a small amount of aluminum chloride is separated and purified as necessary. Thus, tetrachlorosilane can be recovered. This tetrachlorosilane may be recycled as a reaction gas. Further, the separated inert gas or the like may be recycled.

  Thus, in the present embodiment, since the aluminum particles whose surfaces are oxidized so that the mass fraction of oxygen in the entire particles is 0.005% or more and 0.5% or less, in the heating step, Fusion and adhesion between the aluminum particles are suppressed, and the aluminum particles (solid or liquid) can be supplied into the reactor 23 in a dispersed state. Therefore, when silicon is produced by reducing tetrachlorosilane with aluminum, the utilization rate of aluminum can be increased and productivity can be increased.

(Second Embodiment)
A second embodiment of the present invention will be described in detail with reference to FIG. FIG. 3 is a schematic configuration diagram showing a configuration of the reaction apparatus 30 according to the second embodiment.

The method for producing silicon particles according to the second embodiment is mainly different from the method for producing silicon particles according to the first embodiment in the following (1).
(1) A point in which aluminum particles are produced using a gas atomizing method and the like, and aluminum particles having a suitable particle size range are selected with a classifier, and then reheated without being stored and supplied to the classifier.

  Hereinafter, the difference between the second embodiment and the first embodiment will be mainly described, and the description of matters common to the first embodiment will be omitted.

  The reactor 30 shown in FIG. 3 connects the atomizer 8b, the online particle classifier 300, the particle heater 26, the reactor 23, the exhaust gas cooler 29, the solid-gas separators 25 and 28, the tetrachlorosilane heating unit 37, and these. Piping (hereinafter referred to as “line” in some cases).

(Atomizing device 8b)
The atomizing device 8b mainly includes a molten metal storage unit 31, an atomizing gas injection unit 32, and an atomizing container.

  The molten metal container 31 includes a tubular member 31c that communicates with a nozzle 31a that allows molten aluminum to flow out, and a container 31d that accommodates molten aluminum. The tubular member 31c and the container 31d are provided in the sealed container 31e. A heater (not shown) is provided around the molten metal container 31 so that the temperature of the molten aluminum to be accommodated can be adjusted. As shown in FIG. 3, the nozzle 31 a extends into the atomizing container 34.

  An atomized gas injection unit 32 is provided on the molten metal storage unit 31. The atomizing gas injection unit 32 includes a nozzle 32a having an opening provided along the outer periphery of the nozzle 31a. Atomized gas that is appropriately heated as needed is ejected from the nozzle 32a. The molten aluminum flowing out of the nozzle 31a forms a thin stream of molten aluminum on the end face of the nozzle 31a, and atomized gas is blown from the nozzle 32a adjacent to the narrow stream, so that fine micro droplets P are efficiently formed. This is preferable. In this way, the structure in which molten aluminum is flowed upward and atomized is called an updraft type, and a structure in which a nozzle for flowing liquid aluminum and a nozzle for injecting atomized gas are arranged close to each other is a confined type ( It is called a Confined type or a Close-Coupled type).

  When atomizing gas is injected from the nozzle 32a, a negative pressure is generated in the vicinity of the outlet of the nozzle 31a, and the molten aluminum in the container 31d is sucked upward by this negative pressure. Molten aluminum sucked upward flows out of the nozzle 31a. In this way, by providing the atomizing gas injection unit 32 at the bottom of the atomizing container 34 and adopting a configuration in which molten aluminum flows out with a negative pressure by atomizing gas injection, the supply of the atomizing gas is inevitably stopped. In addition, the supply of molten aluminum into the atomizing vessel 34 is also interrupted at the same time. Therefore, even when such a situation occurs, aluminum particles can be accommodated without being contaminated by the molten aluminum lump. In addition, in order to make molten aluminum flow out stably, the pressure of the inert gas atmosphere in the airtight container 31e can be adjusted.

  The atomizing vessel 34 extends vertically and surrounds the atomizing gas injection unit 2. The atomizing vessel 34 is provided at the upper end of the cylindrical portion 34 a. A reduced diameter portion 34c having a solid-gas mixed fluid discharge port 34b for discharging the fluid to be discharged. In addition, when entering the solid-gas mixed fluid discharge port 34b, the aluminum particles are usually solid. The gas-atomized aluminum particles are supplied to the online particle classifier 300 through the discharge line L320 together with the atomized gas and / or carrier gas.

  A carrier gas containing an inert gas as a main component is introduced into the atomizing vessel 34 from the carrier gas supply port 34d in order to adjust the amount of aluminum particles discharged from the solid-gas mixed fluid discharge port 34b and the atmosphere in the atomizing vessel 34. be able to.

  As shown in FIG. 3, it is preferable to provide a heater 343 or, if necessary, cooling means 344 around the atomizing container 34. When the atmospheric temperature in the atomizing vessel 34 rises due to continuous gas atomization of molten aluminum, it is necessary to adjust the atmospheric temperature using the cooling means 344. Thereby, while suppressing the oxidation of the surface of the aluminum particle more than necessary, the high temperature damage of the member which comprises the atomization container 34 can be prevented, and it is suitable. In addition, when the atomizing gas temperature to be appropriately heated is low, it is preferable to adjust the temperature in the atomizing vessel 34 and the temperature of the aluminum particles to 100 ° C. or higher using the heater 343.

  In the second embodiment, the atomizing gas injected from the nozzle 32a and / or the carrier gas supplied from the carrier gas supply port 34d or the like is inert containing oxygen and / or moisture as in the first embodiment. By using the gas, it is possible to easily obtain aluminum particles whose surfaces are oxidized so that the mass fraction of oxygen contained in the entire aluminum particles is 0.005% or more and 0.5% or less. Various conditions in the atomizing gas and the atomizing container 34 can be the same as those in the first embodiment.

(Online particle classifier 300)
The online particle classifier 300 classifies and removes coarse aluminum particles contained in the aluminum particles formed by gas atomization, which are discharged from the solid-gas mixed fluid discharge port 34 b of the atomization vessel 34, and supplies them to the reactor 23. Although the online particle classifier 300 is not particularly limited, a cyclone solid-gas separator can be exemplified. By preventing coarse aluminum particles inevitably generated during gas atomization from being mixed and supplied to the reactor 23, a uniform reduction reaction (the above formula (A)) proceeds stably in the reactor 23. Is preferred. The temperature of the atmospheric gas in the online particle classifier 300 is preferably 100 ° C. or higher. Thereby, it can fully suppress that the moisture contained in atmosphere adheres to aluminum particles. Examples of the heating means include a means for heating the online particle classifier 300 from the outside by a heater or the like (not shown), a means for appropriately heating the carrier gas supplied from the carrier gas supply port 34d, and the like.

  Note that, in the line L320, the online particle classifier 300, and the line L330, the temperature of the aluminum particles is, for example, about 100 to 300 ° C., which is relatively low, so although the collision frequency of the aluminum particles is high, Sticking is hardly a problem.

  In the second embodiment, the on-line particle classifier 300 can classify and remove aluminum particles having an average particle diameter exceeding 1000 μm, which easily inhibit the reduction reaction (the above formula (A)), on-line. For example, by adjusting the supply amount of the carrier gas in addition to the atomizing gas flowing into the online particle classifier 300, the inflow gas speed to the cyclone can be changed, and aluminum particles having a desired particle diameter can be classified and removed. In the second embodiment, the case where the online particle classifier 300 is installed in one stage and the aluminum particles exceeding the average particle size of 1000 μm are classified and removed is exemplified. It is easy to exclude the classification of aluminum particles.

  Aluminum particles that have been classified and sorted in advance to a particle size range suitable for reaction with tetrachlorosilane by the online particle classifier 300 are supplied to the reactor 23 via the particle heater 26 arranged in the line L330. The particle heater 26 functions in the same manner as the particle heater 26 shown in the first embodiment. Further, a line heater (not shown) may be wound around the line L320 and / or the line L330 to heat the solid-gas mixed fluid flowing through the line L320 and / or L330. Moreover, you may supply an inert carrier gas to the line L330 via the line L31 as needed.

(Reactor 23)
The reactor 23 is the same as the reactor 23 shown in the first embodiment. In the present invention, since the surface of the aluminum particles is oxidized so that the mass fraction of oxygen in the whole particles is 0.005% or more and 0.5% or less, the same effects as those of the first embodiment are exhibited.

  According to the silicon manufacturing method according to the second embodiment, the following effects can be obtained in addition to the functions and effects of the first embodiment. That is, the temperature of the aluminum particles is once lowered to near room temperature by connecting the atomizer 8b for producing aluminum particles, the online particle classifier 300 for classifying and sorting the aluminum particles, and the reactor 23 online. Since it is not necessary, the amount of heat to be given by the particle heater 26 can be kept low, so that the energy cost can be reduced and high purity argon gas used in large quantities for atomizing gas, inert carrier gas, etc. This is preferable because the amount of heat used for heating can be reduced. Although not particularly shown, it is preferable to separate and purify high purity argon gas and the like.

  The first and second embodiments disclosed above are examples, and the scope of the present invention is not limited to these embodiments.

  For example, although tetrachlorosilane is used in the first and second embodiments, a halogenated silane other than tetrachlorosilane may be used. Here, the halogenated silane is defined by the above formula (1). Furthermore, you may use the halogenated silane which combined the halogenated silane individually by 1 type or 2 types or more. In the combination of two or more kinds of halogenated silanes, the composition is not particularly limited, but it is preferable that at least the ratio of tetrachlorosilane is contained more than that of another kind of halogenated silane.

  Further, the detailed shape and the like of the aluminum particle production apparatus 10 (for example, the atomized gas injection unit 2) and the reactor 23 of the first embodiment and the reaction apparatus 30 of the second embodiment are not particularly limited. For example, the present invention can be implemented by replacing the free fall-down draft type atomizing device 8a of the first embodiment with the confined-up draft type atomizing device 8b of the second embodiment. Further, in the atomizing device 8a of the first embodiment, a confined atomizing gas injection unit as in the second embodiment may be employed.

  In the first and second embodiments, the particle discharge port 23c for discharging silicon is illustrated in the lower portion of the reactor 23. However, the second structure described later is provided inside the reactor 23 without providing the particle discharge port 23c. A substrate that does not easily contaminate silicon as an object may be installed, and silicon may be deposited and recovered on the surface, or an internal container for collecting silicon may be installed as a second structure to be described later to melt the silicon. You may collect | recover as a liquid. Further, all of the silicon particles can be entrained in the gas discharged from the gas discharge port 23d and recovered using the solid-gas separator 25. Furthermore, the recovery rate of silicon particles can be improved by installing the solid-gas separator 25 in multiple stages.

  In the first and second embodiments, the heated aluminum particles may be supplied upward in the reactor 23 or may be supplied in the horizontal direction. When the aluminum particles move upward or downward in the reactor 23, the halogenated silane gas may be flowed in the same direction as the aluminum particles move (cocurrent flow), facing the direction in which the aluminum particles move. Then, a halogenated silane gas may be flowed (counterflow).

  In the first and second embodiments, the heater 213 and the cooling means 214 are installed outside the reactor 23. However, it is also preferable to install them in the reactor 23.

  Further, the method for producing the aluminum particles whose surfaces are oxidized is not limited to the above, and oxygen and moisture are not mixed in the atomizing gas and the atmospheric gas in the atomizing container, and then left in the air after being discharged from the atomizing container. The above-described aluminum particles whose surface has been oxidized may be manufactured.

  In the first and second embodiments, a mode is disclosed in which the aluminum particles are brought into contact with tetrachlorosilane while falling in the reactor 23. The aluminum particles are heated by the particle heater 26 to a temperature lower than the melting point. In this case, a known fluidized bed type reactor can also be used as the reactor 23. In this case as well, the pressure in the reaction field can be, for example, 0.1 MPa or more.

  In the first and second embodiments, a second structure can be further provided inside the structure (for example, the reactor 23) that forms a space in which tetrachlorosilane exists. As such a second structure, specifically, for example, a nozzle (for example, a nozzle for supplying tetrachlorosilane gas into the reactor 23) protruding into the structure such as the reactor described above, a reaction, etc. Examples include a base material for depositing and adhering silicon to the surface in the vessel 23, an internal container for collecting silicon particles, an internal heater, and the like. These second structures can be provided inside the above-described structure, such as the inside of the cylindrical portion 23a or the 2 reduced diameter portion 3b of the reactor 23 or the inside of the solid-gas separator 5 (for example, , Second structure 23e). Examples of the material of the second structure include at least one selected from the group consisting of alumina, silica, silicon nitride, silicon carbide, carbon, and silicon. As carbon, graphite is preferable. In particular, the second structure can be a structure in which the surface of the main body made of graphite is coated with silicon nitride or silicon carbide. By using the above-described materials for these second structures, silicon with higher purity can be obtained.

  Further, in the second embodiment, tetrachlorosilane gas and / or inert gas from the tetrachlorosilane heating unit 27 is supplied into the reactor 23 from the line L21 shown in FIG. Tetrachlorosilane gas or the like may be mixed with the carrier gas supplied from the carrier gas supply port 34d. As a result, the aluminum particles flowing through the line L320 and / or the line L330 generate heat by generating a reduction reaction (the above formula (A)), so the particle heater 26 for reheating the aluminum particles is omitted or the heating capacity is increased. Since it can reduce, it is suitable.

  In the second embodiment, one reactor 23 connected to the line L330 is illustrated, but it is also preferable to install a plurality of reactors 23 by providing a branch in the L330. Accordingly, it is easy to appropriately ensure a period during which the reduction reaction (the above formula (A)) is sufficiently completed in the reactor 23, which is preferable because high-purity silicon can be continuously produced.

  Furthermore, the solid-gas mixed fluid discharge port 34b of the second embodiment is not necessarily provided at the top of the atomizing container 34, and may be provided on the side surface of the atomizing container 34, for example.

It is a schematic block diagram which shows the structure of the manufacturing apparatus of the aluminum particle which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows the structure of the reaction apparatus which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows the structure of the reaction apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

1, 31 ... Molten metal container,
2, 32 ... atomized gas injection part,
20, 30 ... reactor,
200 ... Particle feeder,
21 ... Aluminum particle container,
23, 33 ... reactor,
25. Solid-gas separator,
26 ... Particle heater,
27 ... Tetrachlorosilane pressure heating section,
28 ... Solid-gas separator,
29 ... Exhaust gas cooler,
300 ... Online particle classifier,
34 ... Atomized container,
F ... trickle of molten aluminum,
P: Aluminum particles (solid or liquid),
G ... Atomized gas.

Claims (5)

Heating the aluminum particles whose surfaces are oxidized so that the mass fraction of oxygen in the whole particles is 0.005% or more and 0.5% or less;
A step of reducing the halogenated silane by bringing the heated aluminum particles into contact with the halogenated silane represented by the following formula (1).
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. ]   The method for producing silicon according to claim 1, wherein in the heating step, the aluminum particles are heated in an inert gas atmosphere having a dew point of −20 ° C. or less.   3. The silicon according to claim 1, wherein in the heating step, the aluminum particles are heated to a melting point of aluminum or higher to form molten aluminum, and in the reduction step, the molten aluminum particles are brought into contact with the halogenated silane. Production method. Before the heating step, the aluminum particles to be heated in the heating step,
A process obtained by blowing an atomized gas containing oxygen and / or moisture to molten aluminum or supplying a gas containing oxygen and / or moisture into a chamber for blowing atomized gas to molten aluminum. Furthermore, the manufacturing method of the silicon | silicone as described in any one of Claims 1-3 provided. Before the heating step, the aluminum particles to be heated in the heating step,
Particles obtained by blowing an atomized gas containing oxygen and / or moisture to molten aluminum, or supplying a gas containing oxygen and / or moisture into a chamber in which atomized gas is blown to molten aluminum The manufacturing method of the silicon | silicone as described in any one of Claims 1-3 further provided with the process obtained by classifying.

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