JPS6369708A - Apparatus for producing silicon - Google Patents

Abstract

PURPOSE:To improve the yield of silicon while retarding the deposition of silicon on the surface of an inside wall in the process for prepg. silicon in a fluidized reactor, by specifying the distance between the inside wall surface of the reactor and a blowing inlet of gaseous chlorosilane, etc. CONSTITUTION:Silicon particles are held in a fluidized reactor 1 to form a fluidized bed, and gaseous chlorosilane or gaseous silane is blown through a blowing inlet 2 to form silicon and formed silicon is deposited on the silicon particles. In this stage, the distance (s) from the blowing inlet 2 of the reactant gas provided to the center of the bottom the reactor 1 to the inside wall surface 3 of the reactor 1 is regulated to such distance that the reactant gas may contact with the inside wall surface 3 after the reactant gas has reacted under thermodynamically equilibrium condition calculating from the flow rate of the blown reactant gas toward the inside wall direction and necessary reaction time until the reactant gas reaches the equilibrium composition. In this case, the preferred particle size of the silicon particle constituting the fluidized bed 4 is ca. 0.3-2mm, and the preferred flow rate of the reactant gas passing through the fluidized bed 4 is ca. 200-2,000mm/sec.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a silicon manufacturing apparatus, specifically, silicon obtained by thermally decomposing or hydrogen reducing chlorosilane gas or silane gas injected using a fluidized bed reactor. The present invention relates to a silicon manufacturing apparatus configured to deposit silicon particles on silicon particles forming a fluidized bed.

<Prior Art> One of the methods for manufacturing polycrystalline silicon is the Siemens method. In this method, a thin silicon rod placed in a health jar is heated with electricity, and a mixed gas of chlorosilane and hydrogen is supplied to cause a reaction, and silicon is deposited on the surface of the thin silicon rod to produce rond-shaped silicon. It's a method. However, this method has the disadvantages of low productivity due to the small reaction surface area, and high heat dissipation from the Herger surface, which results in high power consumption and very high production costs.

On the other hand, in order to improve the drawbacks of the Siemens method, several methods and apparatus for producing polycrystalline silicon using a fluidized bed reactor have recently been proposed, including the invention described in JP-A-57-135708. has been done.

A method or apparatus for producing polycrystalline silicon using a fluidized bed reactor is a method or apparatus for producing polycrystalline silicon by blowing chlorosilane gas or silane gas into a reactor that holds silicon particles in a fluidized bed state, and producing polycrystalline silicon by thermal decomposition or hydrogen reduction of chlorosilane. This is a method or a manufacturing apparatus for manufacturing granular silicon particles by depositing silicon on the surface of the silicon particles.

<Problems to be Solved by the Invention> However, the conventional method or apparatus for producing silicon using a fluidized bed reactor is not disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 57-1357.
As described in Publication No. 08, a heating heater is installed outside the reactor, and the temperature of the fluidized bed is controlled by this heating heater. There were drawbacks such as precipitation of the reactor, narrowing the inside of the reactor or reaction tube, and sometimes destruction of the reaction tube.

<Objective> The present invention aims to eliminate the drawbacks of the above-mentioned conventional techniques, and to provide a silicon manufacturing apparatus in which precipitation of silicon on the inner wall surface of a reactor is suppressed and a high yield of silicon is obtained.

Means for Solving the Problems> The silicon production apparatus of the present invention uses a fluidized bed reactor,
Holding silicon particles in a fluidized bed in the fluidized bed reactor,
A silicon production apparatus, which is configured to deposit silicon produced by thermal decomposition or hydrogen reduction of chlorosilane gas or silane gas blown into a fluidized bed reactor onto silicon particles forming the fluidized bed. , the chlorosilane gas or silane gas that is blown into the fluidized bed reactor from the inlet at a constant rate through the inner wall surface of the fluidized bed reactor almost reaches a thermodynamic equilibrium concentration with respect to the ambient temperature inside the fluidized bed reactor. It is characterized in that it is provided at a distance from the air inlet at least a distance corresponding to the time required to reach the air.

In completing the above solution, the present inventor conducted various studies on the precipitation behavior of chlorosilane gas, etc. sent to a fluidized bed reactor, and found that the thermal decomposition or hydrogen reduction reaction of chlorosilane gas and silane gas occurs at high temperatures. It was found that the process progresses rapidly and reaches an equilibrium composition within a very short time. That is, 5ick.

Hz mixed gas at 1000°C or higher, 5iHC13 at 950°C or higher, 5iH
zC]□ at 800° C. or higher, and SiH4 gas at 600° C. or higher, the required reaction time was 0.5 seconds or less in both cases.

Based on such knowledge, the present inventor further investigated the precipitation behavior of silicon by variously changing the distance between the gas inlet to the fluidized bed reactor and the inner wall surface of the fluidized bed reactor.
It has been found that when the inner wall surface of the fluidized bed reactor is separated from the gas inlet by a distance corresponding to the required reaction time, that is, the time to reach equilibrium composition, silicon precipitation on the inner wall surface is drastically reduced. Ta. The present invention was completed based on this knowledge.

FIG. 1 shows a diagram of the principle of the device of the present invention. A reaction gas inlet 2 is provided at the center of the bottom of the fluidized bed reactor 1 . The distance S from the injection port 2 to the inner wall surface 3 of the fluidized bed reactor 1 is calculated from the flow rate of the injected reaction gas in the direction of the inner wall surface 3 and the reaction time required to reach the equilibrium composition of the reaction gas. The distance is calculated such that the reaction gas contacts the inner wall surface 3 after reaching a thermodynamic equilibrium state. Conversely, if the distance S, the composition of the reaction gas, and the reaction temperature are determined in advance,
This means that it is only necessary to calculate the allowable range of the flow rate of the reactant gas blown in according to the conditions.

Generally, when silicon is produced using this type of fluidized bed reaction, the particle diameter of the silicon particles that are the constituent elements of the fluidized bed 4 formed in the reactor 1 is preferably about 0.3 mm to 2 mm; According to research conducted by the present inventors, the flow rate of the reaction gas passing through the tube 4 is preferably 200 to 2000 mm/sec, and more preferably 800 to 1500 mm/sec.

On the other hand, according to the research conducted by the present inventor, for example, in the case of a reaction gas composition of 30 to 50% trichlorosilane gas and residual hydrogen gas, the time required for the reaction gas to reach equilibrium concentration at normal pressure is as shown in Table 1 below. .

Table 1 From the above, we now use a reaction gas with a trichlorosilane gas concentration of 30%, and set the reaction gas flow rate to 1000 mm/sec.
If the atmosphere inside the reactor is adjusted to 1000°C, it takes 0.05 to 0.1 seconds to reach the equilibrium concentration of the reaction gas. Distance S is 1000 x 0.1-100 (mm)
It would be good if it was above that level.

Similarly, an appropriate distance s can be calculated depending on the type, concentration, reaction temperature, etc. of the reaction gas. Furthermore, when the distance S is determined in advance, the flow rate of the reactant gas can be adjusted accordingly.

Conventionally, no consideration was given to the relationship between the flow rate of the reaction gas, the time it takes to reach equilibrium concentration, and the distance S from the reaction gas inlet to the inner wall of the fluidized bed reactor. This resulted in the precipitation of a large amount of silicon.

<Effect> Chlorosilane gas or silane gas, which is blown into the fluidized bed reactor from the inlet at a constant rate, reaches a thermodynamic equilibrium concentration with respect to the ambient temperature inside the fluidized bed reactor. Since the inlet is placed at least a distance corresponding to the time required for the inlet to arrive, by the time the injected reactant gas reaches the inner wall surface of the reactor, the reactant gas in the excessively concentrated bone has already undergone a decomposition reaction. Alternatively, the reduction reaction has been completed, and therefore precipitation near the wall surface is slightly suppressed. Therefore, according to the device of the present invention, there is less silicon precipitation on the inner wall surface of the fluidized bed reactor, and as a result, the troubles and maintenance of the device are reduced, and continuous operation for a long time is possible. , the yield and productivity of silicon production can be greatly improved.

<Example> (Example 1) Using the fluidized bed reactor shown in FIG. 1, a reaction was carried out for 10 hours under the conditions shown in Table 2 to produce silicon. The diameter of the reactor was 5 cm. As a comparative example, a similar reaction was carried out using a conventional apparatus as shown in FIG. 2, that is, an apparatus in which raw material gas is blown into the entire surface. The diameter of the conventional device was also adjusted to 5 cm.

Table 2 *TC3: Chlorosilane gas nozzle flow rate: Ejection rate from the gas inlet 2 [Results] After 10 hours of reaction, the reactor body was disassembled and the amount of silicon deposited on the furnace wall was measured. In the conventional apparatus in which the distance between the furnace wall and the furnace wall is Qcm, the amount of silicon deposited on the furnace wall was about 10% of the total amount of silicon deposited. On the other hand, in the case of the device of the present invention, the amount of silicon deposited on the furnace wall is 3 to 5% of the total.
Met. That is, it has been reduced to about 172 to I73 compared to the conventional value, and it has been found that it is suitable for long-term continuous operation.

(Example 2) Using a reactor with a diameter of 10c+n, a 10-hour reaction was carried out under the conditions shown in Table 3 in the same manner as in Example 1 in comparison with the conventional apparatus.

Table 3 [Results] As in Example 1, the furnace body was dismantled and the amount of silicon deposited on the furnace wall was compared.
In this device, the amount was 1 to 2% of the total, and it became clear that the device of the present invention caused very little silicon precipitation on the furnace wall and was suitable for long-term operation.

(Example 3) Using the reactor shown in FIG. 1, the nozzle flow rate (the jetting speed from the blowing port 2) was changed at A and B under the conditions shown in Table 4.

After 10 hours of reaction, the amount of silicon deposited on the furnace wall was compared.

Table 4 [Results] When the nozzle flow velocity was reduced, the amount of silicon deposited on the furnace wall was less than 1% of the total, which was reduced to about 2% compared to less than 2% in case A. That is, it has become clear that by adjusting the nozzle flow rate, the same effect as adjusting the distance S from the blowing port 2 to the inner wall surface of the reactor can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus for implementing the present invention, and FIG. 2 is a block diagram of a conventional apparatus. 1: Fluidized bed reactor 2: Inlet 3: Inner wall surface I S: Distance from inlet to inner wall surface D: Diameter of fluidized bed reactor

Claims (1)

[Claims] Using a fluidized bed reactor, silicon particles are held in a fluidized bed form in the fluidized bed reactor, and silicon produced by thermal decomposition or hydrogen reduction of chlorosilane gas or silane gas blown into the fluidized bed reactor is used. , an apparatus for producing silicon in which silicon particles are deposited on silicon particles forming the fluidized bed, the inner wall surface of the fluidized bed reactor being
At least a distance corresponding to the time required for chlorosilane gas or silane gas, which is blown into the fluidized bed reactor from the inlet at a constant rate, to almost reach a thermodynamic equilibrium concentration with respect to the ambient temperature in the fluidized bed reactor, as described above. A silicon manufacturing device characterized by being installed away from a blowing port.