JP2014189475A - Method of producing silicon tetrachloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing silicon tetrachloride which chlorinates silica efficiently and recycles efficiently a raw material scattered from a chlorination furnace during production of silicon tetrachloride.SOLUTION: A method of producing silicon tetrachloride is based on chlorinating an oxide containing silicon dioxide as a raw material and is characterized by returning the raw material scattered from a chlorination furnace used in the production process to the chlorination furnace or a solid matter recovery system arranged in the downstream of the chlorination furnace so as to reuse.

Description

  The present invention relates to a method for producing silicon tetrachloride by a chlorine method, and more particularly to a technology for reusing raw materials recovered in a production process of silicon tetrachloride.

  Silicon tetrachloride is a valuable raw material for high-purity silicon. Conventionally, silicon tetrachloride is made by bringing crude silicon into contact with chlorine gas or hydrochloric acid, and the silicon tetrachloride is reduced by hydrogen to produce a high-purity semiconductor. Metallic silicon is manufactured.

  On the other hand, a method of producing silicon tetrachloride by reacting silica, which is cheaper than crude silicon, with chlorine gas (hereinafter sometimes referred to as “chlorine method”) is also known. In this method, since the formation reaction of silicon tetrachloride is an endothermic reaction, some form of heat replenishment is required, which contributes to the delay in practical application of the method.

  In response to such a problem, an attempt has been reported in which metal silicon is added to silicon tetrachloride and the reaction heat generated during chlorination of the metal silicon is used (for example, see Patent Document 1). .

  In addition, a technique for chlorinating metal silicon cuttings generated in a silicon wafer manufacturing process and recovering it as silicon tetrachloride is also known (for example, see Patent Document 2).

  However, simply adding metal silicon into the fluidized bed in the chlorination furnace leaves the problem that metal silicon reacts preferentially over silica and the chlorination reaction of silica is delayed. Improvement measures are required.

  Moreover, raw materials are consumed with the chlorination reaction, and fine powder is produced. There is also a so-called carry-over problem that the fine powder of the raw material is transported unreacted by the gas flow to the solids recovery system downstream of the chlorination furnace.

  Thus, a method for efficiently producing silicon tetrachloride from silica as a raw material, and further recovering the carry-over raw material generated from a chlorinating furnace for producing silicon tetrachloride and efficiently recovering the raw material as tetrachloride is desired. It is rare.

WO2011 / 078225 Publication WO2008 / 133525 Publication

  An object of the present invention is to provide a technology for efficiently chlorinating silica and efficiently recycling raw materials scattered from a chlorination furnace when producing silicon tetrachloride in a method for producing silicon tetrachloride by a chlorine method. Is.

  In view of the actual situation, the inventors have intensively studied the means for solving the above-mentioned problems. After recovery, the raw material is blended with a new raw material, granulated, and supplied to a chlorination furnace, or the raw material is chlorinated in a reaction vessel in advance to produce silicon tetrachloride from the scattered raw material. It was confirmed that there was an effect that the raw material scattered from the chlorinating furnace could be efficiently recovered by recycling it to the chlorinating furnace together with chlorine gas, and the present invention was completed.

  That is, the method for producing silicon tetrachloride according to the present invention uses a silicon dioxide-containing oxide as a raw material (hereinafter simply referred to as “raw material”), and chlorinates the silicon tetrachloride production method. The raw material scattered from the chlorination furnace used in 1 is returned to the chlorination furnace or the solid matter recovery system disposed downstream of the chlorination furnace and reused.

  In the method for producing silicon tetrachloride according to the present invention, it is preferable to directly return the raw material scattered from the chlorination furnace into the fluidized bed of the chlorination furnace.

  In the method for producing silicon tetrachloride according to the present invention, the raw material scattered from the chlorination furnace is granulated and then supplied to the fluidized bed from above or from the bottom of the fluidized bed in the chlorination furnace. is there.

  In the method for producing silicon tetrachloride according to the present invention, it is preferable that the raw material contains silicon dioxide, coke and metal silicon.

  In the method for producing silicon tetrachloride according to the present invention, it is preferable that the granule is 100 to 2000 μm.

  In the method for producing silicon tetrachloride according to the present invention, the granule includes a non-standard fine powder raw material that has been excluded in advance from the lot raw material supplied as the raw material for the chlorination furnace. This is a preferred embodiment.

  In the method for producing silicon tetrachloride according to the present invention, it is preferable that the raw material and granulated material scattered from the chlorination furnace are supplied into the fluidized bed together with chlorine gas from the bottom of the chlorination furnace.

  In the method for producing silicon tetrachloride according to the present invention, a gas generated by chlorinating the raw material and granulated material scattered from the chlorination furnace in another reaction vessel is supplied to the chlorination furnace together with chlorine gas. Is a preferred embodiment.

  In the method for producing silicon tetrachloride according to the present invention, the gas generated by chlorinating the raw material scattered from the chlorination furnace in another reaction vessel is supplied to a solids recovery step disposed at the latter stage of the chlorination furnace. This is a preferred embodiment.

  By following the method according to the present invention, the silicon component can be efficiently recovered from the solid material scattered from the chlorination furnace for producing silicon tetrachloride, and silicon tetrachloride can be produced.

It is a flowchart which shows 1st Embodiment of this invention. It is a flowchart which shows 2nd Embodiment of this invention. It is a flowchart which shows 3rd Embodiment of this invention. It is a flowchart which shows 4th Embodiment of this invention.

1. First Embodiment The best embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of a preferred embodiment of the process for producing silicon tetrachloride according to the present invention.

In the embodiment shown in FIG. 1, a raw material containing silica is supplied from the top of the chlorination furnace 1, chlorine gas is supplied from the bottom of the chlorination furnace 1, and a fluidized bed 3 is formed in the chlorination furnace 1. Inside, the raw material is chlorinated to produce silicon tetrachloride. In this process, most of the raw material is consumed and converted to silicon tetrachloride, but a part of the raw material is carried over to the solids recovery system in the form of fine powder.
As used herein, the term “solid matter recovery system” means an equipment configuration including piping arranged on the downstream side with respect to the chlorination furnace 1.

  In this method, the generated silicon tetrachloride gas and the finely divided silica raw material which has been scattered without reacting with the chlorine gas and flowed downstream from the chlorination furnace 1 are recovered by the cyclone 2 and recovered with the silicon tetrachloride gas. It is preferable to separate the fine powder raw material and return the recovered fine powder raw material to the chlorination furnace 1.

  In the present invention, it is also preferable that the fine powder raw material recovered by the cyclone 2 is directly returned to the fluidized bed 3 formed in the chlorination furnace 1. Thus, by recovering the raw material scattered from the chlorination furnace 1 and returning it directly to the fluidized bed 3, the above-mentioned unreacted recovered fine powder raw material can be chlorinated efficiently. As a result, the raw material of silicon oxide There is an effect that the basic unit can be greatly improved.

  Here, as a specific method of returning the recovered fine powder raw material directly into the fluidized bed 3, for example, the raw material recovered by the cyclone 2 can be directly returned into the fluidized bed 3 by air current transportation using chlorine gas. .

2. Second Embodiment FIG. 2 shows another preferred embodiment according to the present invention. In this embodiment, after the recovered fine powder raw material scattered from the chlorination furnace 1 is recovered by the cyclone 2, it is made into a granulated body of a predetermined size in the granulating device 5, and this is used as a raw material for producing silicon tetrachloride. It is preferable to return to the chlorination furnace 1 as a preferred embodiment.

  By performing the treatment as described above, the recovered fine powder raw material is prevented from being scattered again from the chlorination furnace, and is reliably consumed by the chlorination reaction, and the raw material scattered from the chlorination furnace 1 is efficiently used as a raw material for producing silicon tetrachloride. It can be reused as an effect.

  The size of the granulated body is preferably granulated in the range of 100 μm to 2000 μm.

  In the present invention, the granulated body is a preferred embodiment in which the granulated silica and coke scattered from the chlorination furnace 1 are returned to the chlorination furnace 1. May be blended to form a granulated body.

  By blending the aforementioned metal silicon into silica and coke, the effect that the reaction heat generated by the reaction between the metal silicon and chlorine gas can be compensated as a heat source that is insufficient to maintain the chlorination reaction temperature with silica. It plays.

The composition of the granulated body of the recovered fine powder raw material is preferably adjusted to 65 to 75 wt% for silica and 25 to 35 wt% for coke.
Moreover, when mix | blending metal silicon with the said granulated body, it is preferable to adjust to 55-70 wt% of silica, 20-30 wt% of coke, and 5-25 wt% of metal silicon.
By adjusting to the above composition, there is an effect that the chlorination reaction of silica can be performed efficiently. Moreover, it is preferable that the diameter of a granulated body shall be the range of 100 micrometers-2000 micrometers.
By adjusting to the above range, there is an effect that chlorination of silica can be efficiently advanced.

  By forming a granule having a composition in the above-described range, the effect that the chlorination reaction of silica can be efficiently advanced is achieved.

  As the binder used in the production of the granulated material used in the present invention, it is preferable to use water glass or an organic silane binder. By using the above-mentioned binder, the chlorination reaction can be promoted without impairing the purity of silicon tetrachloride produced by the chlorination reaction of the granulated body.

  Moreover, in the said embodiment, it is preferable that the granule contains a non-standard fine powder raw material that has been conventionally excluded from the lot raw material related to silica supplied as a raw material for the chlorination furnace. To do.

  The raw material silica has been conventionally prepared and supplied so as to obtain a raw material having a predetermined particle size or more by removing fine particles having a predetermined particle size or less prior to supply to the chlorination furnace. By using this fine silica as a granulated product, there is an effect that fine silica, which has been conventionally discarded, can be efficiently used as a raw material for silicon tetrachloride.

  In the present invention, the original raw material supplied to the chlorination furnace 1 can also be configured as a granulated body containing silica and coke as described above. By configuring as a granule as described above, the chlorination reaction of silica can be efficiently advanced.

3. Third Embodiment FIG. 3 further shows another preferred embodiment according to the present invention. In this embodiment, the recovered fine powder material scattered from the chlorination furnace 1 is separated and recovered by the cyclone 2 and then chlorinated by another reactor 4 to form silicon tetrachloride, and then returned to the chlorination furnace 1 as a preferred embodiment. Is.

  By taking the measures as described above, it is possible to effectively use silicon in the recovered fine powder raw material scattered from the chlorination furnace 1 as silicon tetrachloride.

4). Fourth Embodiment FIG. 4 further shows another preferred embodiment according to the present invention. In the present invention, the silicon tetrachloride gas generated by chlorinating the recovered fine powder raw material scattered from the chlorination furnace 1 in the reactor 4 is returned between the cyclone 2 disposed downstream of the chlorination furnace 1 and the cooler 6. Is a preferred embodiment.

  By setting it as the above-mentioned aspect, there exists an effect that the silicon tetrachloride which scattered from the chlorination furnace 1 and produced | generated by the chlorination reaction of the unreacted silica and coke can be efficiently collect | recovered.

  In the fourth embodiment, the gas containing silicon tetrachloride generated in the reactor 4 may be returned between the cyclone 2 and the chlorination furnace 1. In this case, the solid content accompanying the silicon tetrachloride gas produced in the reactor 4 can be efficiently separated from the silicon tetrachloride by the cyclone 2, and as a result, the liquid silicon tetrachloride recovered by the cooling system 6 can be separated. There is an effect that it is possible to suppress a decrease in purity.

  The above-described reactor 4 is preferably provided with a preheating or pre-chlorination function. The preheating function has an effect that the fine raw material can be effectively preheated by disposing an external heating device to the reactor 4.

  By performing the preheating operation of the solid matter as described above, when the recovered fine powder raw material is re-supplied into the chlorination furnace 1, the reactivity is increased and the effect that it can be chlorinated efficiently is obtained. It is what you play.

  Further, by supplying chlorine gas to the reactor 4, the raw material recovered by the cyclone 2 can be chlorinated efficiently.

  In the present invention, metallic silicon can also be added to the reactor 4 from the outside. As the metal silicon, for example, scrap material generated in a silicon tetrachloride reduction process or a high-purity silicon ingot processing process can be used. The metal silicon supplied to the reactor 4 reacts with chlorine gas to form silicon tetrachloride gas, and at this time, reaction heat is generated, and the generated heat effectively uses the fine powder raw material supplied to the chlorination furnace 1. Not only can it be preheated, it can also be used as a heat compensation source for the chlorination reaction section of silica in the chlorination furnace 1.

  By adopting the method as described above, the recovered fine powder raw material scattered from the chlorination furnace 1 can be effectively reused. As a result, the loss of the raw material source unit with respect to silicon tetrachloride can be effectively suppressed, and the amount of waste to be processed in the process can be effectively reduced.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
The conditions used in the examples according to the method for producing silicon tetrachloride according to the present invention are shown below.
1. Raw material 1) Silica (main raw material)
SiO ₂ grade: 99.5%
Particle size: 0.1 μm to 5 μm
2) Coke grade: 98%
Particle size: 0.1 μm to 5 μm
3) Granule Composition: Silica: Coke = 1 mol: 2.2 mol
Particle size: 100 μm to 2000 μm
4) Chlorine gas purity: 99%
2. Chlorination furnace 1) Refractory: Graphite 2) Chlorination temperature: 1300-1400 ° C
3) Dispersion disk: Graphite Treatment furnace 1) Refractory: Graphite 2) Chlorination temperature: 1300-1400 ° C

[Example 1]
Using the apparatus flow shown in FIG. 1, chlorination of silica was performed under the above conditions to produce silicon tetrachloride. As a result, the utilization rate of silica was about 99% from the weight of silica charged into the chlorination furnace 1 and the weight of recovered silicon tetrachloride. Moreover, the chlorination reaction rate of the fine raw material scattered from the chlorination furnace 1 was 75%.

[Example 2]
Using the apparatus flow shown in FIG. 2, chlorination of silica was performed under the conditions described above to produce silicon tetrachloride. As a result, the utilization rate of silica subjected to chlorination with respect to the weight of silica supplied to the chlorination furnace 1 was 75% from the weight of silica charged into the chlorination furnace 1 and the recovered silicon tetrachloride.

[Example 3]
Using the apparatus flow shown in FIG. 3, chlorination of silica was performed under the above-described conditions to produce silicon tetrachloride. The utilization rate of silica subjected to chlorination in this example was 99%. Moreover, the chlorination reaction rate of the fine raw material scattered from the chlorination furnace 1 was 75%.

[Example 4]
Silica chlorination shown in FIG. 4 was performed to produce silicon tetrachloride. The utilization rate of silica used in the chlorination reaction was 94%. Moreover, the chlorination reaction rate of the fine raw material scattered from the chlorination furnace 1 was 75%.

[Comparative Example 1]
In Example 1, the ratio of the raw material recovered in the cyclone to the raw material ore charged in the chlorinating furnace 1 was 25% when the weight of the raw material recovered in the cyclone 2 was measured. From this ratio, the utilization rate of silica in the chlorination furnace 1 was calculated to be 75%. In addition, the waste has conventionally been to be disposed of at a high cost.

  By producing silicon tetrachloride by the method according to the present invention according to the above-described examples and comparative examples, not only can chlorination of silica be effectively advanced, but also the amount of waste generated in the process is effectively reduced. The effect that it can suppress can be produced.

  The present invention can efficiently improve the production cost of titanium tetrachloride produced using a chlorinating furnace for producing titanium tetrachloride, and also reduces the environmental burden by reducing the amount of waste.

DESCRIPTION OF SYMBOLS 1 ... Chlorination furnace 2 ... Cyclone 3 ... Fluidized bed 4 ... Reactor 5 ... Granulator 6 ... Cooler

Claims (9)

  In the method for producing silicon tetrachloride using an oxide containing silicon dioxide as a raw material (hereinafter simply referred to as “raw material”), the raw material scattered from a chlorination furnace used in the production step is A method for producing silicon tetrachloride, wherein the method is returned to a chlorination furnace or a solids recovery system disposed downstream of the chlorination furnace and reused.   The method for producing silicon tetrachloride according to claim 1, wherein the raw material scattered from the chlorination furnace is directly returned into the fluidized bed of the chlorination furnace.   The method for producing silicon tetrachloride according to claim 1, wherein the raw material scattered from the chlorination furnace is granulated and then supplied to the fluidized bed from above or at the bottom of the fluidized bed in the chlorination furnace.   The method for producing silicon tetrachloride according to any one of claims 1 to 3, wherein the raw material contains at least silicon dioxide and coke among silicon dioxide, coke and metal silicon.   The said granulated body exists in the range of 100-2000 micrometers, The manufacturing method of the silicon tetrachloride of Claim 3 characterized by the above-mentioned.   4. The silicon tetrachloride according to claim 3, wherein the granulated material includes a non-standard fine powder raw material that has been excluded in advance from a lot raw material supplied as a raw material for the chlorination furnace. Production method.   The raw material scattered from the chlorination furnace and / or a granule of the raw material are supplied into the fluidized bed together with chlorine gas from the bottom of the chlorination furnace. Process for producing silicon tetrachloride.   The gas produced by chlorinating the raw material and / or the granule of the raw material scattered from the chlorination furnace in another reaction vessel is returned to the chlorination furnace together with chlorine gas. 8. The method for producing silicon tetrachloride according to any one of 7 above. The gas generated by chlorinating the raw material scattered from the chlorination furnace in a separate reaction vessel is supplied to a solids recovery system disposed at the rear stage of the chlorination furnace. The manufacturing method of the silicon tetrachloride in any one.

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