JP2002173313A - Method for manufacturing silicon tetrachloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing silicon tetrachloride by reacting metal silicon with chlorine. SOLUTION: Silicon tetrachloride is manufactured by supplying chlorine whose volume is increased by three to ten by diluting with an inert gas to the lower part of a reactor and reacting the supplied chlorine with metal silicon of a semi-fluidized (slagging) state at 450-800 deg.C. The metal silicon having <=5 mm particle size and >=90% purity is preferably used. It is preferable to spray silicon tetrachloride from the upper part of the reactor for the purpose of removing the reaction heat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing silicon tetrachloride by reacting metallic silicon with chlorine.

[0002]

2. Description of the Related Art To produce silicon tetrachloride, there is a method using ferrosilicon having a low Si content and chlorine and hydrochloric acid as raw materials in a fixed bed (JP-B-52-38518). This method has a lot of residue, especially iron chloride is deliquescent, so there are many troubles that clog the outlet. Further, the reaction with chlorine was intense, the reaction often proceeded locally, and it was difficult to proceed uniformly. Chlorine drift occurs, and often chlorine is detected outside the reactor. On the other hand, the fluidized bed has no local reaction, but has a characteristic that the amount of gas is large and detection outside the reactor does not stop. Since a great deal of cost is required to separate and remove excess chlorine, it is desirable that the chlorine conversion be as high as possible. Other production methods include, for example, a method of chlorinating finely divided silicon carbide (JP-A-63-117907) and a method of mixing silica stone with coke to chlorinate (Japanese Patent Publication No. 60-118623).

[0003]

SUMMARY OF THE INVENTION The present invention provides a novel method for producing silicon tetrachloride which facilitates the removal of heat of reaction, controls the reaction and prevents the drift of chlorine.

[0004]

According to the present invention, chlorine supplied from the lower part of the reactor after being diluted 3 to 10 times (by volume) with an inert gas and metallic silicon are reacted at a reaction temperature in a semi-fluid state (slugging). This is a method for producing silicon tetrachloride which is reacted at 450 ° C. to 800 ° C. The metal silicon preferably has a particle size of 5 mm or less and a purity of 90% or more, and it is preferable to spray silicon tetrachloride from the upper part of the reactor to remove reaction heat.
In order to control the reaction and prevent the drift of chlorine, chlorine is diluted with an inert gas such as silicon tetrachloride or nitrogen gas and introduced, and the metal silicon is allowed to react in a semi-fluid state, so that the reaction is performed in a uniform state. Progress and the reaction can be well controlled.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is necessary that metallic silicon be in a semi-fluid state (slugging), and if so, its size, shape, filling amount, etc. are not particularly limited, but the size is preferably a particle size. 5 mm or less, more preferably 350 to 6
It is in the range of 00 μm. If it is large, metallic silicon is less likely to flow, and it is difficult to obtain a semi-fluid state, which tends to cause chlorine drift. On the other hand, if it is smaller than 350 μm, it is liable to be scattered and to be easily lost as dust. Preferably, the metallic silicon is filled in the reactor in a thickness of 20 to 800 mm, more preferably in the range of 200 to 500 mm.
If it is less than 20 mm, chlorine will be detected outside the reactor, and if it exceeds 800 mm, it will be difficult for the metallic silicon to fluidize (slag). Here, the thickness means that in a stationary state. The metallic silicon is preferably in the form of particles.

[0006] The purity of metallic silicon is preferably 90% or more, and the residue can be reduced. The components of the residue are chlorides such as Ti, Fe, and Al. If these substances are present in a large amount, they adhere to the inner surfaces of the reactor and pipes, causing a blockage. Residues which have become small and light in response to the terminal velocity of the air flow are scattered upward.
It is collected in a cyclone following the reactor and discharged out of the system. If it is not wet collection, processing such as drying of the residue becomes unnecessary. Even if the purity of the silicon metal is low or the particle size is large, the amount thereof is 20% or less of the whole metal silicon having the above-mentioned preferable particle size, shape and purity, slugging is possible, and the purity of silicon tetrachloride is high. Can be used if is within the range required for the intended use.

[0007] Chlorine and metal silicon diluted from 3 to 10 times (volume ratio) with an inert gas and supplied from the lower part of the reactor have a reaction temperature of 450 ° C to 800 ° C in a semi-fluid state (slugging).
To react. Here, the reaction temperature means the temperature of the metal silicon layer. The reaction temperature must be 450 ° C. or higher,
The temperature is preferably in the range of 0 to 800 ° C. If the temperature is lower than 450 ° C., the reaction is extremely slow. Although there is no problem with the high reaction temperature, none of the reactor materials has corrosion resistance. Therefore, the temperature is preferably 800 ° C. or less.

The reaction between metallic silicon and chlorine is a huge exothermic reaction. In order to remove this heat of reaction, it is preferable to spray silicon tetrachloride from the upper part of the reactor in the form of a shower, and remove the heat of reaction by the heat of evaporation. It is preferable to spray directly in the form of a shower. As the silicon tetrachloride to be sprayed, the generated silicon tetrachloride can be used, and the amount thereof is not particularly limited, but is preferably in the range of 70 to 90% of the generated amount.

The reaction proceeds very rapidly. Often a local reaction occurs in contact with chlorine, metallic silicon glows red,
The reaction temperature can partially exceed 1000 ° C. The reaction is performed in a slugging state to prevent local overheating. Here, the slugging state refers to a state in which the entire metal silicon particles are fluidized without floating and do not scatter. At this time, in order to avoid a rapid reaction near the entrance, chlorine is preferably diluted 3 to 10 times (by volume) with an inert gas that does not react with chlorine. As the inert gas, for example, gasified tetrachloride is used. There are silicon, nitrogen gas and the like. Diluted chlorine is introduced from the bottom of the reactor.

[0010] The reactor is not particularly limited as long as the metal silicon can maintain a slugging state, but a fixed bed reactor can be suitably used. A carbon plate (distributor) is placed at the bottom of the reactor, and a chlorine introducing device is placed at the bottom of the plate. The reactor is made of a heat insulating material that can withstand high-temperature chlorine, for example, alumina, carbon, silicon carbide, or the like, and a vessel made of a steel case is used outside the reactor. In addition, a grid having a pitch of # 50 to 200 mm was placed on the perforated plate to generate a stable slugging state.

Chlorine has a very high conversion rate of 99.9.
% Or more. Therefore, in the case of purification, separation of silicon tetrachloride and unreacted chlorine is easy, and the equipment for treating the separated chlorine can be small. In order to obtain a higher reaction rate, a layer containing metal silicon having a coarse particle diameter heated to 450 ° C. or higher may be placed on the shower portion.

[0012]

EXAMPLE 1 A reactor 1 is filled with metallic silicon. The silicon tetrachloride generated by the reaction is cooled by the cooler 2. Thereafter, metal chlorides such as Ti, Fe, and Al entrained in the gas and unreacted metal silicon particles which have become smaller by reaction and scattered from the reactor 1 are collected by the cyclone 3 and discharged from the lower part thereof. The silicon tetrachloride gas from which the solid content has been separated in the cyclone 3 is condensed in the condenser 4 and stored in the reaction liquid tank 5. A part of the reaction solution 5 goes to 10 showers and is used for cooling the reactor 1. It is also used for diluting chlorine introduced into the reactor 1 by gasification in the evaporator 8. In a reactor 1 having an inner diameter of 200 mm, a particle size of 35
0 to 600 μm, 99.6% pure metal silicon (main component of impurities: Fe 420 ppm, Al = 920 ppm, Ca 4
50 ppm) with a thickness of 300 mm (2.0 kg). Preheat to 600 ° C with a heater. There chlorine 6.0dm ³ / min, the reaction by blowing from the bottom of the reactor a mixed gas prepared by diluting with silicon tetrachloride gas 80dm ³ / min gasified starts in the evaporator. At this time, the reactor inlet pressure is 0.03 kPa. Further, a silicon tetrachloride solution of 120 cm ³ / min is sprayed from the upper part of the reactor. The reaction temperature was maintained at 600 ° C. by measuring the temperature of the metal silicon layer with a thermocouple. 13.6 kg / hr of silicon tetrachloride was produced. At this time, the residual reaction amount was 9 g.
(Residual rate: 0.44%). The reaction rate of chlorine was 99.9% or more.

Example 2 Example 1 was carried out using a metal silicon having a purity of 90%. The reaction situation was almost the same as in Example 1, but the residual amount was about 200 g, and the obtained silicon tetrachloride weighed 12.2 kg.
/ H. The reaction rate of chlorine was 99.9% or more.

Comparative Example 1 The test conditions were the same as those of the example, and only chlorine was introduced from the lower part of the reactor, and the test was carried out without dilution with silicon tetrachloride. The vicinity of the contact between chlorine and silicon glowed red, the reaction partially proceeded, and after a while, chlorine drift occurred, and 1% of chlorine was detected from the reactor outlet.

[0015]

According to the present invention, the following effects can be obtained. 1. A rapid local reaction near the chlorine inlet in the reactor can be avoided, and a uniform reaction can be obtained in the entire metal silicon layer in the reactor. 2. Since the silicon metal particles can be sufficiently reacted, there is very little residue. 3. An extremely high conversion of 99% or more of chlorine is obtained. 4. It collects by-products such as metal silicon chlorides such as Ti, Fe and Al originating from impurities in the raw materials and unreacted metallic silicon particles scattered from the reactor with a dry cyclone. No treatment such as drying of the residue is required. 5. High-purity silicon tetrachloride can be obtained without special purification equipment.

[Brief description of the drawings]

FIG. 1 Reaction apparatus

FIG. 2 Reactor

FIG. 3 Reactor

FIG. 4 Reactor

[Explanation of symbols]

 1: Reactor 2: Cooler 3: Cyclone 4: Condenser 5: Reaction liquid tank 6, 7: Pump 8: Evaporator 9: Discharge valve 10: Spray nozzle 11, 12: Flow control valve 16: Carbon plate 17: Insulation material for reactor 18: Case 21: Metallic silicon 22: Plate 31: Grid

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiko Ono 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Prefecture Inside the Electrochemical Industry Co., Ltd. F-term in stock association (reference) 4G072 AA12 BB05 GG03 HH01 JJ06 MM38 RR17

Claims (3)

[Claims] 1. A reaction temperature of 450 ° C. to 800 ° C. in a semi-fluid state (slugging) of chlorine and metal silicon diluted from 3 to 10 times (volume ratio) with an inert gas and supplied from the lower part of the reactor.
For producing silicon tetrachloride. 2. The method for producing silicon tetrachloride according to claim 1, wherein the metal silicon has a particle size of 5 mm or less and a purity of 90% or more. 3. The method for producing silicon tetrachloride according to claim 1, wherein one or more of the following requirements are satisfied. 1. 1. Spray silicon tetrachloride onto metal silicon from the top of the reactor 2. The reactor has a carbon plate (distributor) 3. The reactor has high temperature chlorine-resistant insulation and a steel case surrounding it. Metal silicon is packed in a fixed bed reactor in 20 to 800 mm