JP2008133147A - Method for producing silicon chloride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing silicon chloride, in which a return pipeline is hardly clogged with metallic silicon fine powder and consequently the operation of a fluidized bed can be stabilized when metallic silicon fine powder is chloridized in the fluidized bed to produce silicon chloride. <P>SOLUTION: The return pipeline is used which is constituted so that 0.2≤(S2/S1)≤0.8 (wherein S1 is the cross-sectional area of the return pipeline 6 to be connected to a cyclone of a fluidized bed furnace; S2 is the vertically projected area of a powder discharge port 7 of the return pipeline) is satisfied and 0.2≤(D2/D1)≤8 (wherein D1 is the inside diameter of the return pipeline; D2 is the distance from the powder discharge port to a nozzle 8 for sending a fluidizing gas) is also satisfied. Wherein, if the S1 and the opened area (S3) of the powder discharge port of the return pipeline satisfies the relation: 0.2≤(S3/S1)≤0.8, the occlusion suppression effect of the return pipeline is further enhanced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing silicon chloride in which a metal silicon powder and a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride are reacted in a fluidized bed.

  By reacting metal silicon powder with a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride, trichlorosilane is transformed into a by-product such as silicon tetrachloride (these reaction products are referred to herein as “silicon chloride”). It will be generated together with the item. Thereafter, ultrahigh-purity trichlorosilane obtained through a distillation step is used as a raw material for polycrystalline silicon, and the obtained polycrystalline silicon is used as a raw material for a silicon single crystal used as a substrate for a semiconductor device, for example, or as a solar material. Widely used as a battery substrate.

  The reaction between the metal silicon powder and a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride is performed in a fluidized bed in which a reaction gas is blown into metal silicon fine particles to fluidize the fine particles.

  This fluidization method can significantly increase the frequency of contact between solids and gas and increase the efficiency of the reaction. For example, gas reactions using solid catalysts, fluidized bed boilers that burn coal, municipal waste and sludge It is used for gas-solid catalytic reactions and gas-solid reactions such as fluidized bed incinerators for incineration, and is also applied to physical operations as a fluidized bed dryer.

  FIG. 1 is a diagram showing a schematic configuration example of a reactor for producing acrylonitrile. Air is supplied into the reactor 1 to form a fluidized bed 2 of a solid catalyst, and ammonia and propylene as raw materials are introduced into the fluidized bed 2 and reacted to synthesize acrylonitrile. Since the catalyst is finely divided, a multistage cyclone 3 for separating and recovering fine particles released out of the system is provided in the reactor 1. In order to suppress excessive heat generation and adjust the temperature of the fluidized bed 2 within a predetermined range, a cooling pipe 4 is attached.

  The generated gas containing acrylonitrile enters the cyclone 3 from the gas inlet 5 together with the fine solid catalyst, and after the catalyst is separated and recovered, it is discharged from the reactor 1 as a product gas. The fine solid catalyst collected by the cyclone 3 is returned to the fluidized bed 2 through the return pipe 6 and used again as a catalyst.

  As described above, in a device using a fluidized bed, in many cases, fine particles are released together with a gas. Particularly in a fluidized bed for reaction, useful components remain in the fine particles, which are recovered. In order to reuse in a fluidized bed, a cyclone (solid gas separator) having a simple structure is generally provided in a reactor (fluidized bed furnace).

  However, when the fine particles collected by the cyclone are returned to the fluid tank, the pipe (return pipe 6 illustrated in FIG. 1) is clogged, and the fine particles accumulate in the cyclone and the cyclone function may not be performed. Often occurs. Further, depending on the operation, there may be a case where fine particles flow back (blow up) in the return pipe.

  For this reason, a weight valve is usually attached to the tip of the return pipe. Since the pressure by the solid particles and gas constituting the fluidized bed is acting on the outer surface of the weight valve, the valve is initially closed, but fine particles accumulate in the return pipe and the pressure (pressure on the inner surface) ) Exceeds the pressure on the outer surface, the valve opens, and the fine particles in the return pipe are returned to the fluid tank. As a result, the pressure on the outer surface exceeds the pressure on the inner surface, and the valve closes again.

  However, since this weight valve has a structure using a metal hinge such as stainless steel (SUS type), for example, when hard particles such as metal silicon become the constituent particles of the fluidized bed, the metal hinge becomes poorly rotated in a short period due to wear. There is a problem that cannot be overlooked in practice, such as malfunction due to deterioration at high temperature.

  Further, for example, in Patent Document 1, as a result of repeating the operation of returning the fine particles in the particle discharge pipe (corresponding to the return pipe) into the fluidized tank by the weight valve, the particles constituting the fluidized bed are refined, and the volume of the fluidized bed is increased. The density decreases and the bulk (volume) increases, so the upper surface of the flow surface rises, the upper surface of the fine particles in the particle discharge pipe also rises and reaches the cyclone body, and there is a problem that the cyclone stops functioning. .

  Therefore, in this patent document, a seal gas such as hydrogen gas or argon gas is supplied in the middle of a particle discharge pipe, and a gas flow rising through the particle discharge pipe causes gas to be discharged out of the system in a cyclone. There have been proposed a cyclone configured to generate a sealed fluidized bed of separated fine particles and prevent blowing up in a particle discharge pipe (return pipe), and a fluidized bed reaction apparatus including the cyclone. In this device, when the bulk density of the fluidized bed decreases and the upper surface of the fluidized surface rises too much, the supply amount of the seal gas is reduced, stopped, or increased to reduce or eliminate the seal fluidized bed. By intentionally blowing up the return pipe, the fine particles are forcibly discharged to return the bulk density of the fluidized bed to the normal range.

  However, the present inventor applied and investigated a technique for preventing blow-up in the return pipe by blowing a seal gas in the middle of the return pipe in a fluidized bed of metal silicon powder, and found that the problem of blockage of the return pipe Was not solved, and it turned out that the blockage frequency at the tip of the return pipe is high. In addition, since the intermittent forced discharge of the fine particles is performed in order to suppress the excessive rise of the upper surface of the fluidized surface due to the decrease in the bulk density of the fluidized bed, the raw material yield is deteriorated.

  Also, when hydrogen is used as the seal gas, the partial pressure of hydrogen in the gas at the location where the gas supplied to the fluidized bed (using silicon tetrachloride and hydrogen) and the seal gas are mixed (particle surface below the cyclone). As a result, it was found that silicon was deposited and the seal gas introduction pipe was blocked. Furthermore, when the flow rate of the seal gas is high, fine powder is scattered, and when the flow rate is low, the formation of the seal fluidized bed becomes insufficient, so the flow rate of the seal gas must be strictly controlled and operation is difficult. There is also a problem.

  On the other hand, a circulating fluidized bed of a system different from the fluidized bed shown in FIG. 1 is used for combustion and thermal decomposition of sewage sludge, municipal waste, and the like. In this circulating fluidized bed, a large amount of fluidized gas is sent to the fluidized bed to intentionally blow up the fluidized bed, and the fluidized gas is changed to “fluidized bed” → “cyclone” → “return pipe” → “fluidized bed”. This is a method of circulating a large amount in the route. Although this circulating fluidized bed has a high reaction rate, the raw material yield is poor, and fine control for stabilizing the reaction required for chlorination of metal silicon powder is difficult, so it should be adopted for chlorination of metal silicon powder. I can't.

  Conventionally, when producing silicon chloride by chlorinating metal silicon powder in a fluidized bed, there has been a demand for a production method with less blockage in the return pipe, stable operation, and high raw material yield. However, the present situation is that the development of a technology that can sufficiently meet this demand has not yet been made.

JP-A-9-194207

  The present invention has been made in view of such a situation, and an object of the present invention is to make silicon chloride by reacting a metal silicon powder and a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride in a fluidized bed. When manufacturing products, there is little blockage of the return pipe provided for reuse in the fluidized bed of metal silicon fine powder recovered by the cyclone, stable operation is possible, and raw material yield is high. The object is to provide a method for producing silicon chloride.

  In order to achieve the above-mentioned object, the present inventor has investigated in detail the blockage at the front end portion of the return pipe having a particularly high blockage frequency. As a result, a part where the powder does not flow sufficiently at the tip of the return pipe, that is, a part where the fluidized state is not maintained well is likely to occur, and the inside of the fluidized bed furnace is at a high temperature. It was found that it gradually solidified due to the above, and the characteristics of the powder were impaired, resulting in clogging of the piping.

  Therefore, in order to eliminate parts where powder flow is insufficient, the shape and area of the opening (powder discharge port) of the return pipe are appropriately determined, and an air supply nozzle is provided near the tip of the return pipe to flow. When a part of the gas in the bed was forcibly sent, it was confirmed that the clogging of the piping could be suppressed.

  The gist of the present invention resides in the following method for producing silicon chloride.

That is, metal silicon powder is reacted with a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride in a fluidized bed to obtain a target silicon chloride, and the silicon chloride-containing gas discharged from the fluidized bed furnace Is a method for producing silicon chloride, in which metal silicon fine powder is separated and recovered from a cyclone and the recovered metal silicon fine powder is returned to a fluidized bed by a return pipe, wherein the pipe cross-sectional area (S1) of the return pipe and the return pipe The relationship with the vertical projection area (S2) of the powder outlet satisfies the following formula (1),
0.2 ≦ (S2 / S1) ≦ 0.8 (1)
When the inner diameter of the return pipe is D1 and the distance from the powder outlet to the flowing gas supply nozzle provided in the middle of the return pipe is D2, D1 and D2 satisfy the following expression (2): This is a method for producing silicon chloride.

0.2 ≦ (D2 / D1) ≦ 8 (2)
The term “silicon chloride” as used herein means a silicon compound containing chlorine produced by a reaction between a gas containing silicon and hydrogen chloride, or a gas containing silicon and hydrogen or a gas containing silicon chloride. Mainly trichlorosilane and silicon tetrachloride. Examples of silicon chloride include silicon tetrachloride and disilicon hexachloride. Usually, silicon tetrachloride is used.

  The “pipe cross-sectional area (S1)” is a cross-sectional area inside the return pipe, and is a cross-sectional area in a plane perpendicular to the axis (center line) direction of the pipe. In addition, the pipe cross-sectional area (S1) when the diameter of the return pipe is not constant is the pipe cross-sectional area at a total of 21 locations divided by 1 cm in the section from 10 cm to 30 cm in the upstream direction along the return pipe from the powder discharge port. The average value is measured as the pipe cross-sectional area (S1).

  The “vertical projected area (S2) of the powder discharge port” is a projected area when the powder discharge port is viewed from below, that is, a downward opening area.

  The “inner diameter (D1) of the return pipe” is an average inner diameter of a section from 10 cm to 30 cm upstream from the powder discharge port along the return pipe.

  In addition, the “powder discharge port” is also a standard for determining the distance D2, but when the “powder discharge port” is formed horizontally, the horizontal surface of the “powder discharge port” is cut obliquely. In this case, the horizontal plane including the center of gravity of the powder discharge port surface is used as a reference. In addition, when calculating | requiring the distance from a powder discharge port, when return piping is bent, the distance along the centerline of piping from the said reference | standard is measured.

  In the silicon chloride manufacturing method, if the relationship between the pipe cross-sectional area (S1) of the return pipe and the opening area (S3) of the powder discharge port of the return pipe satisfies the following expression (3), the return The blockage suppression effect of the piping is further improved.

            0.2 ≦ (S3 / S1) ≦ 0.8 (3)

  According to the method for producing silicon chloride of the present invention, when producing silicon chloride by reacting metal silicon powder with a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride in a fluidized bed. The return pipe provided for reuse in the fluidized bed of the metal silicon fine powder discharged with the silicon chloride-containing gas discharged from the fluidized bed furnace and recovered by the cyclone is less clogged. Stable operation is possible. Thereby, a high raw material yield can be maintained.

  Below, the manufacturing method of the silicon chloride of this invention is demonstrated concretely with reference to drawings.

  As described above, the silicon chloride production method of the present invention is obtained by reacting a metal silicon powder with a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride in a fluidized bed to obtain a target silicon chloride. A silicon chloride production method for separating and recovering metal silicon fine powder from a silicon chloride-containing gas discharged from a fluidized bed furnace with a cyclone and returning the recovered metal silicon fine powder to a fluidized bed through a return pipe. Using a return pipe with a special structure that has been modified, such as changing the shape of the opening (powder discharge port) and mounting an air supply nozzle to send fluid gas (gas in the fluidized bed) into the return pipe The manufacturing method of performing the operation while returning the recovered metal silicon fine powder to the fluidized bed.

  A fluidized bed is formed in the fluidized bed furnace, and a cyclone for separating and recovering metal silicon fine powder contained in a gas containing silicon chloride obtained by reaction in the fluidized bed is attached. ing. A return pipe is connected to the lower part of the cyclone (see FIG. 1). The cyclone may be attached outside the fluidized bed furnace.

  FIG. 2 is a view schematically showing a longitudinal section in the vicinity of the tip of a return pipe connected to a cyclone of a fluidized bed furnace, and (a) is an example of a return pipe used for carrying out the manufacturing method of the present invention. b) and (c) are piping examples used or proposed in the past.

  As shown in FIG. 2B, the return pipe 6 conventionally used in FIG. 2 is a straight pipe type in the vicinity of the tip of the pipe. Further, (c) is a return pipe whose opening (powder discharge port) described in the above-mentioned Patent Document 1 is oriented horizontally, and the return pipe shown in FIG. 1 is also included in this type.

  On the other hand, as shown in FIG. 2 (a), the return pipe 6 used for carrying out the manufacturing method of the present invention is improved in the shape of the powder discharge port 7, and in the middle of the pipe 6, that is, the powder. A fluid gas supply nozzle 8 is provided at a position of a distance D2 upward from the level of the discharge port 7, and a fluid gas (gas in the fluidized bed) can be injected from the gas supply nozzle 8. In addition, the code | symbol C shown in the figure is a position corresponded to the gravity center of the powder discharge port 7 surface cut diagonally.

  In the manufacturing method of the present invention, the relationship between the pipe cross-sectional area (S1) of the return pipe and the vertical projection area (S2) of the powder discharge port of the return pipe satisfies the following expression (1).

0.2 ≦ (S2 / S1) ≦ 0.8 (1)
If (S2 / S1) is less than 0.2, the amount of flowing gas flowing from the fluidized bed furnace side (that is, the powder discharge port side) into the return pipe is too small. This is because the flow state in the vicinity of the tip of the pipe is not well maintained, and the powder tends to solidify at that portion. Increasing the amount of flowing gas from the air supply nozzle provided in the middle of the return pipe can suppress the blockage of the return pipe to some extent, but the increase in the amount of flowing gas is likely to cause blow-up and stabilize the inside of the return pipe. It is difficult to maintain a fluid state. On the other hand, if (S2 / S1) exceeds 0.8, there is too much inflow of fluid gas from the fluidized bed furnace side, and blowing will occur even if the fluid gas from the fluid gas feed nozzle is stopped. It becomes easy.

  In the manufacturing method of the present invention, when the inner diameter of the return pipe is D1, and the distance from the powder discharge port to the flowing gas supply nozzle provided in the return pipe is D2, D1 and D2 are expressed by the following formula (2). It shall be satisfied. In other words, the mounting position of the air supply nozzle is returned upward from the powder discharge port to a position 0.2 to 8 times the inner diameter D1 of the pipe.

0.2 ≦ (D2 / D1) ≦ 8 (2)
If D2 is less than 0.2 times D1, that is, the attachment position of the air supply nozzle 8 is close to the level of the center of gravity position C in FIG. This is because most of the flowing gas injected from the air supply nozzle flows out into the fluidized bed furnace, and it is difficult to stably maintain the flowing state in the return pipe. On the other hand, if D2 exceeds 8 times D1, the attachment position of the air supply slip is too high, and the flow action of the gas sent from the air supply nozzle to the return pipe does not act near the tip of the return pipe. The blockage prevention effect near the end of the pipe is insufficient.

  The desirable range of (D2 / D1) is “0.8 ≦ (D2 / D1) ≦ 4”. By satisfying this condition, the blockage prevention effect of the return pipe is further improved.

When carrying out the production method of the present invention, the flow gas injection amount [A (m ³ / min)] into the return pipe may be determined as follows, for example. That is, the fluidized bed is maintained in a fluidized state, the amount of fluid gas flowing into the return pipe is gradually increased, and the fluid gas injection amount [A _(max) ] when the blow-up starts is detected in advance from the exhaust from the cyclone. The flow gas injection amount (A) may be set in the range of “A _(max) × 0.15 ≦ A ≦ A _(max) × 0.7”.

  In the silicon chloride manufacturing method of the present invention described above, the relationship between the pipe cross-sectional area (S1) of the return pipe and the opening area (S3) of the powder outlet of the return pipe satisfies the following expression (3): If it does so, the obstruction | occlusion suppression effect of return piping will improve further.

0.2 ≦ (S3 / S1) ≦ 0.8 (3)
This regulation means that the shape of the return pipe has a tapered outlet whose opening area of the powder outlet is 0.2 to 0.8 times the cross-sectional area of the return pipe. That is, in addition to reducing the vertical projected area of the powder discharge port of the return pipe (regulation according to the above equation (1)), the actual opening area is also reduced. Thereby, even if it is a case where blowing up cannot fully be prevented only by making the vertical projection area of a powder discharge port small, it can prevent reliably.

  The reason why (S3 / S1) is 0.2 or more is that if it is less than 0.2, not only does the inflow of the fluid gas from the fluidized bed furnace side become excessive, but also the powder does not easily flow out from the powder outlet, and the return pipe This is because there is a possibility that it may cause a blockage at the tip portion of the. The reason why (S3 / S1) is 0.8 or less is that when it exceeds 0.8, the inflow of the flowing gas becomes excessive, which is not desirable for reliably preventing the occurrence of blow-up.

  FIG. 3 is a diagram schematically showing a longitudinal section in the vicinity of the tip of a return pipe having a tapered powder discharge port. (A) is when (S3 / S1) is 0.8, and (b) is when (S3 / S1) is 0.3. In this case, the vertical projection area of the powder outlet and the actual opening area are the same. The attachment position of the air supply nozzle is the same in both (a) and (b), and (D2 / D1) is 0.8. That is, both (a) and (b) are return pipes that satisfy the conditions defined in the present invention.

  On the other hand, (c) in FIG. 3 is a return pipe that falls outside the conditions defined in the present invention when the air supply nozzle is mounted too close to the powder discharge port and is the same as the discharge port surface.

  FIG. 4 is a diagram schematically showing a longitudinal section of a return pipe in which a cyclone is provided outside the fluidized bed furnace. The return pipe is inserted diagonally downward into the fluidized bed furnace, but the vicinity of the tip is configured downward, so the shape of the powder discharge port, the installation of the air supply nozzle, etc. If defined similarly, it can be used in the production method of the present invention.

  The installation position of the return pipe in the fluidized bed furnace is not particularly limited and is arbitrary. However, the position is more biased toward the furnace wall than the vicinity of the center of the fluidized bed furnace, that is, the radius is 100 (dimensionless number). In this case, it is desirable to dispose at a position in the range of 50 to 90 from the center of the fluidized bed furnace toward the furnace wall, more preferably in a range of 80 to 90. Compared to the vicinity of the center of the fluidized bed furnace, the amount near the furnace wall is smaller in the amount of flowing fluid and tends to move downward, so that the fine powder in the return pipe easily returns to the fluidized bed. Because.

  As explained above, the silicon chloride production method of the present invention has a flow rate of flowing gas from the fluidized bed furnace side to the return pipe that is neither too much nor too little, in other words, “moderately” returns from the powder outlet. In this method, the flowing gas enters the vicinity of the tip of the pipe, the flowing gas is separately injected into the return pipe, and the flow state in the return pipe is stably maintained by the synergistic effect.

  According to this production method of the present invention, there is little blockage of the return pipe, stable operation is possible, and blow-up is suppressed, so that silicon chloride can be produced with a high raw material yield. Since the sealing gas described in Patent Document 1 is not used, there is an advantage that the operation is simple.

  In the circulating fluidized bed described above, since a large amount of fluidized gas is circulated, the particle size of the powder in the return pipe and the fluidized tank is close to each other, whereas in the silicon chloride production method of the present invention, it is formed in the fluidized bed furnace. In the fluidized bed, there is a difference that the powder particle size in the return pipe is much smaller than in the fluidized bed. Therefore, even if the clogging prevention method is effective in the circulating fluidized bed, it is presumed that the non-circulating fluidized bed according to the production method of the present invention cannot obtain a sufficient effect.

  In addition to improving the shape of the opening (powder discharge port), the production method of the present invention was carried out using the return pipe to which the air supply nozzle was attached, the raw material loss and the average life of the return pipe were investigated, The effect of the invention was confirmed. In addition, the quality of raw material yield can be evaluated by investigating “raw material loss”. “Average life” is a barometer of the blockage frequency of the return pipe. This is because once the return pipe is closed, the powder is sintered in the pipe, so that the closed state cannot be repaired even if flowing gas is injected, and the return pipe needs to be replaced.

[Specifications of implementation conditions]
Return pipe inner diameter: 76 mm (Pipe cross-sectional area is circular)
Return pipe cross-sectional area: 45 cm ² (7.6 × 7.6 × 3.14 / 4)
Fluidized tank temperature: 500 ° C (temperature of gas blown from the fluidized bed hearth)
Gas component fed to fluidized bed: Hydrogen + silicon tetrachloride Powder raw material charged into fluidized bed: Metallic silicon (silicon with a purity of 99% by mass or more)
The production method of the present invention was carried out under the above-mentioned conditions, and the raw material loss and the average life of the return pipe were investigated. For comparison, the same investigation was performed for a conventional return pipe without an air supply nozzle or a return pipe that does not satisfy the conditions defined in the present invention even if an air supply nozzle is provided. The survey results are shown in Table 1.

  In Table 1, “raw material loss α” is a relative value expressed as 100 (standard) when the discharge of metal silicon, which is a raw material, to the outside of the furnace is the maximum (No. 1 in Table 1). “Average life β” is a relative value expressed as 1 (reference) when the average life is the shortest (No. 2 in Table 1) because the return pipe needs to be replaced. The “evaluation index” is an index introduced for comprehensive evaluation that takes into account both raw material loss and the average life of the return pipe. Standards such as “x” and “o” in the “overall evaluation” column are as follows: It is as follows. If the evaluation index was 50 or more, it was considered good.

×: Evaluation index 49 or less ○: Evaluation index 50 to 99
◯: Evaluation index 100 to 149
OO: Evaluation index 150 to 199
OOXX: Evaluation index of 200 or more As is clear from the results shown in Table 1, in the examples of the present invention (No. 3 to No. 13), the evaluation index is 57 or more, and the overall evaluation is ◯ or more. there were. In particular, when using a return pipe having a tapered outlet, the opening area (S3) of the powder outlet is 0.2 to 0.8 times the cross-sectional area (S1) of the return pipe (No. 9 to No. 13), the overall evaluation was XX mark or XXX mark, and very good results were obtained. In addition, No. 7 is No. 7 when the return pipe of FIG. No. 9 shows the case where the return pipe shown in FIG. 11 corresponds to the case of using the return pipe of FIG.

  On the other hand, in Comparative Example 1 using a straight pipe-type return pipe (pipe corresponding to FIG. 2B) in the vicinity of the tip of the pipe, the material loss is extremely large because blow-up easily occurs. In Comparative Example 2 using a return pipe (pipe corresponding to FIG. 2 (c)) having an opening (powder discharge port) facing sideways, the pipe was easily blocked. Further, in Comparative Example 14, when a return pipe (pipe corresponding to FIG. 3C) in which the air supply nozzle is attached too close to the powder discharge port is used, in Comparative Example 15, the air supply nozzle is attached to the powder discharge port. In the case of using a return pipe that was too far from the outlet, all of the pipes were easily clogged at the tip.

  In the method for producing silicon chloride of the present invention, when producing silicon chloride by reacting metal silicon powder with a gas containing hydrogen chloride in a fluidized bed, the metal silicon fine powder recovered by the cyclone is used. A manufacturing method that uses a return pipe with an improved structure, such as mounting an air supply nozzle, to operate while returning to the fluidized bed. The return pipe is less clogged, stable operation is possible, and high raw materials Yield can be maintained.

  Therefore, the production method of the present invention is a method that can be effectively used for the production of silicon chloride, especially trichlorosilane and polycrystalline silicon using this as a raw material.

It is a figure which shows the schematic structural example of the reactor for acrylonitrile manufacture. It is a figure which shows typically the longitudinal cross-section of the front-end | tip vicinity of the return piping connected with the cyclone of the fluidized-bed furnace, (a) is an example of return piping used for implementation of the manufacturing method of this invention, (b) and ( c) is an example of a conventional return pipe. It is a figure which shows typically the longitudinal cross-section of the front-end | tip vicinity of the return piping which has a tapering powder discharge port. It is a figure which shows typically the longitudinal cross-section of the return piping in which the cyclone is provided in the outer side of the fluidized bed furnace.

Explanation of symbols

1: Reactor 2: Fluidized bed 3: Cyclone 4: Cooling pipe 5: Gas inlet 6: Return pipe 7: Powder outlet 8: Air supply nozzle

Claims (2)

Metallic silicon powder is reacted with a gas containing hydrogen chloride or a gas containing hydrogen and silicon chloride in a fluidized bed to obtain a target silicon chloride, and a cyclone is produced from the silicon chloride-containing gas discharged from the fluidized bed furnace. And separating and recovering the metal silicon fine powder, and returning the recovered metal silicon fine powder to the fluidized bed through the return pipe,
The relationship between the pipe cross-sectional area (S1) of the return pipe and the vertical projection area (S2) of the powder discharge port of the return pipe satisfies the following formula (1),
0.2 ≦ (S2 / S1) ≦ 0.8 (1)
When the inner diameter of the return pipe is D1 and the distance from the powder outlet to the flowing gas supply nozzle provided in the middle of the return pipe is D2, D1 and D2 satisfy the following expression (2): A method for producing silicon chloride.
0.2 ≦ (D2 / D1) ≦ 8 (2) 2. The method for producing silicon chloride according to claim 1, wherein a relationship between a pipe cross-sectional area (S1) of the return pipe and an opening area (S3) of the powder discharge port of the return pipe satisfies the following expression (3): .
0.2 ≦ (S3 / S1) ≦ 0.8 (3)

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