JPH08310808A - Production of granular polysilicon - Google Patents

Abstract

PURPOSE: To efficiently treat the by-produced fine powder by passing the waste gas of a reactor for producing granular polysilicon through a fine powder collector provided with an agitated tank at its bottom. CONSTITUTION: A reactor 1 packed with the silicon seed grains having 250-1500μm grain size distribution is heated by a heater 14, silanes of desired concn. are introduced from a reacting gas inlet pipe 17 to fluidize the silicon, and the silicon grains is grown by thermal decomposition or reduction. The reaction gas contg. fine grains is discharged from a gas discharge pipe 16 and introduced into a fine powder collector 2, the fine powder is separated by a filter 7 and accumulated on a silicon grain-packed bed 3 at the bottom of the collector 2, and the gas is passed through a gas discharge pipe 8 and sent to a booster compressor 21. After reaction, valves 10 and 13 are closed, valves 11 and 12 are opened, a fine powder carrier gas is supplied from a feed port 4 to fluidize the silicon-packed bed, the fine powder layer is agitated, and the fine powder is entrained by the carrier gas and discharged into a tower 22 for making fine powder harmless through a gas discharge pipe 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently treating exhaust gas and fine powder produced as a by-product in a method for producing granular polysilicon by decomposing or reducing silanes. .

[0002]

2. Description of the Related Art Conventionally, granular polysilicon is produced by depositing polysilicon produced by thermal decomposition or reduction reaction of silanes in a fluidized bed reactor on the fluidized silicon granules in the reactor. . In this method, the polysilicon produced by the thermal decomposition or reduction reaction of silanes not only deposits on the surface of silicon granules but also aggregates and nucleates to become silicon fine powder. The reaction gas or the fluid driving gas is discharged as an exhaust gas to the outside of the fluidized bed reactor together with most of the generated silicon fine powder. Exhaust gas is passed through a fines collector to remove fines in the gas,
Recovered and reused. Further, the collected fine powder is conveyed from the fine powder collector to the abatement tower and subjected to a harmful treatment.

However, when the conventional fine powder collector is used, the fine powder collected at the inner bottom of the collector solidifies into a cake or block during collection and is carried out from the collector to the abatement tower. There was a problem that it was very difficult. For the collected matter of the fine powder collector, the fine powder discharge gas is supplied from the upper portion of the fine powder collector, and the fine powder discharge port (diameter: D is provided at the bottom of the fine powder collector.
From t), it is conveyed to the fine powder abatement tower by pressure. At this time, the fine powder produced as a by-product in the production of granular polysilicon is 1 to 10 μm.
Therefore, the maximum discharge rate F of fine powder per discharge port cross-sectional area is F = ρs × (1−εs) × (uo-ut) [ρ
s: Silicon density, εs: Porosity, uo: Gas linear velocity, u
t; end velocity of fine powder], and blockage. Also,
There is also a method in which a screen is provided at the bottom of the fine powder collector, a fine powder discharge gas is supplied from below the screen upward, and the fine powder is carried along with the gas to the abatement tower. In this case, since the fine powder accumulated on the bottom of the vessel is in the form of a cake or block, the fine powder carry-out gas flows through the fine powder layer in one direction (channeling), and the amount of fine powder entrained is extremely small. However, the carrying-out time is long and a large amount of fine powder carrying-out gas is required, so that there is a problem in practicality.

[0004]

It has been desired to develop a new technique for compensating for the drawbacks of the above conventional methods. That is, there has been a demand for development of a method for easily carrying out the fine powder collected in the fine powder collector to the outside of the collector.

[0005]

As a result of intensive studies to solve the above-mentioned technical problems, the present inventor has collected in a collector a cake-like or block-like collected fine powder. Dispersed into the original fine powder by stirring, and by introducing the fine powder discharge gas into the collector under a stirring atmosphere,
They have found that they can be easily and quickly discharged out of the system by being entrained by the gas, and completed the present invention.

That is, according to the present invention, in the method for producing granular polysilicon by the thermal decomposition or reduction reaction of silanes, the gas discharged from the reactor is passed through a fine powder collector having a stirring tank at the bottom. And a method for manufacturing granular polysilicon.

In the present invention, a known method can be applied to the thermal decomposition or reduction reaction of silanes for producing granular polysilicon without particular limitation. As silanes, monosilane, disilane or halogenated silanes are usually used alone or in a mixture. Monosilane is preferably used advantageously. Here, as the halogenated silane, specifically, monochlorosilane, dichlorosilane, trichlorosilane, tetrachlorosilane, hexachlorosilane and the like are preferably used. These halogenated silanes are usually mixed with hydrogen gas and subjected to a reduction reaction.

The stirring tank provided at the bottom of the fine powder collector used in the present invention is not particularly limited as long as it has a function of stirring the fine powder collected in the collector. For example, the agitation tank may be a fine powder collector having a fluidized bed of silicon particles, a collector having a mechanical stirring function by a screw at the bottom, or a screen provided at the bottom with a screen. The structure may be such that the fine powder layer can be stirred by vibrating the liquid.

Next, details of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of the present invention. The fine powder collector 2 has a flow driving gas supply pipe 4 and a screen 5 at the bottom. Further, a predetermined amount of granular silicon 3 is filled on the screen 5. The silicon particle size is preferably about 150 to 300 μm, and if it is smaller than this, a sufficient stirring effect cannot be obtained, and if it is larger, the amount of gas to be fluidized is increased, which is not preferable. An inlet 6 for gas from the reactor and a gas vent pipe 8 for the filter 7 are provided in the upper part and are connected to the booster compressor -21 for the recovered gas. A gas vent pipe 9 not passing through the filter 7 is also provided and is connected to the fine powder abatement tower 22. The degassing pipes 8 and 9 are provided with valves 10 and 11, respectively. Flow drive gas supply pipe 4
A valve 12 is provided in the. 250 ~ in the reactor 1
Seed particles with a particle size distribution of 1500 μm have a stationary bed height of 10
Gas is blown into the reaction container 1 through the reaction gas introduction pipe 17 so that the monosilane concentration becomes a desired concentration, preferably 10 mol%, while the container is filled with 00 mm and heated by the heater 14. The gas blown into the reaction vessel 1 rises in the reaction vessel 1, and in this process, the silicon in the vessel is physically fluidized to form a fluidized bed, and chemically, silicon is formed on the surface of the silicon particles. Are deposited to grow silicon particles. Along with that, fine powder is produced as a by-product. The silicon that has undergone a predetermined deposition reaction is sequentially withdrawn from the reaction vessel 1 through a granular silicon withdrawal tube 19, and seed particles are inserted into the reaction vessel from the supply tube 20 instead.

The gas containing the fine powder that has been used for the silicon deposition reaction is discharged from the reaction vessel 1 through the degassing tube 16 and introduced into the fine powder collector 2. The fine powder in the gas is separated by the filter 7 in the fine powder collector 2 and deposited on the silicon-filled layer at the bottom of the collector 2. The gas discharged from the degassing tube 8 is pressurized to a predetermined pressure by the pressure boosting compressor 21 and is supplied to the reactor 1 together with the gas introduced from the supplementary gas supply tube 18 so that the monosilane concentration becomes the desired value. . After the completion of the predetermined reaction, the gas supply to the reactor 1 is stopped, the valves 10 and 13 are closed, and the valves 11 and 12 are opened. A gas is supplied from the bottom of the fine powder collector 2, preferably a gas linear velocity u is u = a × umf [a;
3, umf; minimum fluidization rate].
When the gas linear velocity u is in the above range, the silicon-filled layer at the bottom of the collector is stirred particularly well, and an efficient amount of gas can be obtained, which is preferable. As the silicon filling at the bottom of the fine powder collector 2 flows, the fine powder accumulated during the reaction above the packed bed is agitated and dispersed. As a result, the fine gas is entrained in the gas discharged from the degassing tube 9, and the maximum discharge speed F = ρs × (1−εs) × (uo−
ut) [ρs: silicon density, εs: porosity, uo: gas linear velocity, ut: final velocity of fine powder], and conveyed to the fine powder removal tower 22.

Although the case where the fluidized bed of silicon particles is used as the stirring tank has been described above, the stirring tank is not particularly limited as long as it has a stirring function, and as shown in FIG. It is also possible to provide a mechanical stirring function 15 by a screw and to provide a carrying-out gas supply port 4, a carrying-out gas vent 9 and valves 11 and 12 at the bottom. Also, FIG.
Similar results can be obtained even if the screen has a vibrating function without filling the screen 5 with granular silicon.

[0012]

As can be understood from the above description, according to the present invention, fine powder produced as a by-product during the production of granular silicon by the thermal decomposition or reduction reaction of silanes is deposited on the bottom of the fine powder collector. Even if it accumulates in a box shape or a block shape, it can be easily carried out of the container, so that it can be carried out in a short time and with a small amount of gas, and the carry-out port is not clogged with fine powder, so the reaction exhaust gas and fine powder can be efficiently treated It is possible to exert the effect of being able to.

[0013]

【Example】

Example 1 Granular silicon was produced under the following conditions according to the embodiment shown in FIG. A reactor 1 having a diameter of 150 mm and a height of 2500 mm was filled with seed particles having a particle size distribution of 250 to 1500 μm so that the stationary layer height was 1000 mm, and the reaction was performed while heating the inside of the container to 650 ° C. with a heater 14. The reaction vessel 1 is adjusted so that the monosilane concentration is 10 mol% through the gas introduction pipe 17.
Gas was blown inside. Exhaust gas from the reactor is passed through the reactor degassing pipe 16 and the valve 13 and then the fine powder collector 2 (diameter 150 mm, height 1500 mm, 100 μm opening sintered filter 5 at the bottom is installed from the supply port 6). Silicon particles with an average particle diameter of 300 μm are deposited on the top of the layer with a height of 300 mm
Introduced into the filter, the filter-7 (opening 1μ)
m), the gas is discharged from the degassing tube 8 through the valve 10 to the pressurizing compressor-21, the pressure is increased to a predetermined pressure, and the monosilane concentration is 10 mol% together with the gas introduced from the supplementary gas supply tube 18 to the reactor 1. Was supplied. The fine powder collector 2 has an average fine powder of 1 to 10 μm of 0.0
It entered through the supply port 6 at a concentration of 13 g / l. After the reaction,
The valves 10 and 13 are closed, the valves 11 and 12 are opened, and the fine powder discharge gas (argon) is supplied from the supply port 4 so that the gas linear velocity u becomes u = 2 × umf in the silicon-filled layer, and the baking is performed. The silicon particles on the binding filter-5 were caused to flow, and the fine powder layer deposited thereon was stirred. The fine powder that was stirred and dispersed was entrained in the gas, passed through the degassing tube 11, and was discharged to the fine powder removal tower 22. The discharge rate of fine powder at that time was a maximum of 190 kg / h.

Comparative Example The same operation was performed except that the bottom of the fine powder collector 2 was not filled with silicon particles having an average particle diameter of 300 μm, and the discharge rate of the fine powder was only 1.5 kg / h at the maximum.

[Brief description of drawings]

1 is a systematic diagram of an apparatus for carrying out the method of the present invention.

FIG. 2 is an apparatus diagram of a fine powder collector for carrying out the method of the present invention.

[Explanation of symbols]

 1, granular silicon manufacturing device 2, fine powder collector 3, granular silicon packed bed 4, fine powder carrying gas supply port 5, sintering filter-6, reaction exhaust gas introduction port 7, filter-8, degassing during reaction Port 9, gas outlet 10 for discharging fine powder, valve 11, 〃 12, 〃 13, 〃 14, reactor heating heater 15, screw agitator 16, reaction gas discharge pipe 17, reactor gas supply port 18 , Supplementary gas inlet 19, granular silicon outlet 20, seed supply pipe 21, booster compressor 22, fine powder abatement tower

Claims (2)

[Claims] 1. A method for producing granular polysilicon by thermal decomposition or reduction reaction of silanes, characterized in that the gas discharged from the reactor is passed through a fine powder collector having a stirring tank at the bottom. Manufacturing method of granular polysilicon. 2. The method for producing granular polysilicon according to claim 1, wherein the stirring tank of the fine powder collector is a fluidized bed of silicon particles.