WO2014010457A1 - ポリシリコンの製造方法 - Google Patents
ポリシリコンの製造方法 Download PDFInfo
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- WO2014010457A1 WO2014010457A1 PCT/JP2013/068040 JP2013068040W WO2014010457A1 WO 2014010457 A1 WO2014010457 A1 WO 2014010457A1 JP 2013068040 W JP2013068040 W JP 2013068040W WO 2014010457 A1 WO2014010457 A1 WO 2014010457A1
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- exhaust gas
- heat recovery
- gas
- type heat
- boiler
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
- C01B33/03—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition of silicon halides or halosilanes or reduction thereof with hydrogen as the only reducing agent
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/02—Silicon
- C01B33/021—Preparation
- C01B33/027—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material
- C01B33/035—Preparation by decomposition or reduction of gaseous or vaporised silicon compounds other than silica or silica-containing material by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B1/00—Methods of steam generation characterised by form of heating method
- F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
- F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Definitions
- the present invention relates to a method of manufacturing polysilicon, and more specifically, includes a step of efficiently recovering heat from a high temperature exhaust gas generated from a deposition step of polysilicon, and further, a step of recovering an unreacted source gas as needed. And a method of manufacturing polysilicon that can contribute to reduction of manufacturing cost.
- Siemens method As a method of manufacturing polysilicon (also called polycrystalline silicon), Siemens method, VLD method, etc. are known.
- a silicon core wire disposed inside a bell jar type reaction vessel is heated to a deposition temperature of silicon by energization, and here a gas of a silane compound such as trichlorosilane (SiHCl 3 ) or monosilane (SiH 4 ) and hydrogen are used.
- SiHCl 3 trichlorosilane
- SiH 4 monosilane
- polycrystalline silicon is deposited on a silicon core by chemical vapor deposition to obtain a polycrystalline silicon rod of high purity.
- VLD method a cylindrical reaction vessel made of isotropic graphite is heated by high frequency heating, chlorosilanes and hydrogen as raw materials are supplied to the inside of the cylindrical reaction vessel, and polysilicon is deposited on the inner wall surface of the reaction vessel. It is a system.
- polysilicon is deposited by chemical vapor deposition as in the above-mentioned Siemens method.
- unreacted raw material gases such as unreacted silane compounds and hydrogen
- low polymers such as dimers and trimers of silane compounds (also referred to in the art as “polymers”)
- silicon An exhaust gas containing fine powder is generated.
- the polymer (Si X H Y Cl Z) is specifically a Si 2 HCl 5, Si 2 H 2 Cl 4, Si 2 Cl 6 , etc., SiCl 4 (silicon tetrachloride) further high boiling from It is a substance and exists as a highly viscous liquid at low temperatures, and condensed fine particles in mist form are called mists.
- Such a polymer or mist may be deposited and adhered in the piping, which may inhibit the exhaust of the exhaust gas.
- there is a risk that the polymer may ignite in the air when washing away the polymer adhering and remaining in the piping.
- Patent Document 1 Japanese Patent Laid-Open No. 2010-150131
- heat exchange is performed in order to suppress the generation of mist that causes a failure of the compressor. It is disclosed that the flow velocity of the exhaust gas flowing through the vessel is 4 m / s to 7 m / s.
- Patent Document 2 Japanese Patent Application Laid-Open No. 2008-266127 maintains a reaction exhaust gas containing chlorosilanes at 700 ° C. to 1500 ° C. generated from a reduction reaction of chlorosilanes and hydrogen at a temperature of 700 ° C. or more for 2 seconds or more. After that, it is disclosed that generation of mist can be suppressed by cooling to 350 ° C. or less with a heat exchanger.
- Patent Document 1 when cooling a high temperature exhaust gas with a heat exchanger, the polymer contained in the exhaust gas is surely condensed in the heat exchanger by limiting the flow velocity of the exhaust gas passing through the heat exchanger. To make it drop.
- the mixing of the polymer into the compressor is prevented. That is, in this method, the polymer inevitably adheres to the inside of the heat exchanger, and when silicon dust is contained in the exhaust gas, it promotes adhesion and deposition of the polymer in the heat exchanger. Furthermore, in the horizontal heat exchanger, discharging the polymer becomes difficult, and the polymer tends to be deposited in the heat exchanger.
- the heat exchanger needs to be cleaned frequently, which reduces the manufacturing efficiency. For this reason, before introduce
- This device is generally a filter device, and it is also necessary to reduce the exhaust gas temperature before the device is introduced according to the heat resistant temperature of the filter device.
- Patent Document 2 generation of mist is suppressed by maintaining the exhaust gas at a temperature of 700 ° C. or more for 2 seconds or more before supplying the exhaust gas to the heat exchanger, and cooling to 350 ° C. or less in the heat exchanger.
- the exhaust gas due to a small amount of mist in the exhaust gas and silicon fines in the exhaust gas, there has been a problem that local operation such as liquid pooling and adhesion residue of the polymer may occur in the heat exchanger after long operation.
- an object of the present invention is to efficiently recover heat from the high temperature exhaust gas generated from the deposition process of polysilicon.
- the present invention reduces adhesion residue of silicon fine powder and polymer in piping and equipment, improves recovery efficiency of unreacted raw material gas and the like, reduces cleaning frequency, and enables continuous operation for a long time,
- the purpose is to improve manufacturing efficiency.
- the present invention for achieving the above object includes the following gist.
- the gas temperature at the exhaust gas pipe outlet of the boiler type heat recovery apparatus is set to 200 ° C. or higher, and the flow velocity of the exhaust gas at the exhaust gas pipe outlet inside the boiler type heat recovery apparatus is adjusted to 10 m / sec or more.
- Production method is described in accordance with a boiler type heat recovery apparatus.
- a straight pipe type gas introduction pipe is installed before the boiler type heat recovery device, and the ratio of the length L and the inner diameter D of the gas introduction pipe (L: D) is 1: 1 to 5: 1, the method for producing polysilicon according to any one of (1) to (4).
- the deposition step is a step of depositing polysilicon on the inner wall of the cylindrical reaction container with a source gas containing chlorosilanes in the cylindrical reaction container, and after the precipitation step, the temperature of the cylindrical reaction container Further includes a melting step of heating at least the silicon melting point, melting a part or all of the deposited silicon, dropping and recovering the silicon, and repeatedly performing the deposition step and the melting step (1
- the method for producing polysilicon according to any one of (6) to (6).
- a plurality of the boiler-type heat recovery devices having different gas channel cross-sectional areas are arranged in parallel, and exhaust gases discharged from the deposition step and the melting step are each supplied to different boiler-type heat recovery devices.
- the gas temperature at the exhaust gas outlet in the boiler type heat recovery apparatus to 200 ° C. or higher, generation of mist is suppressed by converting the polymer into a gas state in the heat recovery apparatus. For this reason, the mist and the liquid pool are discharged together with the exhaust gas without remaining in the heat recovery apparatus, and continuous operation of the polysilicon manufacturing apparatus becomes possible.
- the heat recovery device a boiler type heat recovery device
- the surface temperature of the heat recovery device in contact with the exhaust gas becomes high, so that liquid accumulation in the heat recovery device is less likely to occur, and the recovered heat is It can be used as an industrial advantage.
- the exhaust gas after passing through the boiler-type heat recovery apparatus contains mist containing silicon fine powder and polymer, but all of these are also recovered by the cooling step (quenching step). For this reason, failure factors, such as a compressor, are also eliminated, and a long continuous operation becomes possible.
- FIG. 1 shows a schematic flow of the present invention.
- a method of manufacturing polysilicon according to the present invention includes a deposition step of depositing polysilicon from a source gas containing chlorosilanes, and a heat recovery step of introducing exhaust gas from the deposition step into a boiler type heat recovery apparatus and recovering heat . Furthermore, after the heat recovery step, it is preferable to include an exhaust gas cooling step for collecting unreacted chlorosilanes, a polymer and silicon fine powder contained in the exhaust gas. Further, it is preferable to include a step of recovering the unreacted source gas from the exhaust gas after the exhaust gas cooling step, and it is preferable to include a step of supplying the recovered unreacted source gas to the precipitation step.
- the deposition process for depositing polysilicon is not particularly limited, and is performed by the conventionally employed Siemens method, VLD method or the like.
- the silicon core wire placed in the bell jar is heated to a temperature of 900 to 1250 ° C., and polysilicon is deposited on the silicon core wire by supplying a raw material gas containing chlorosilanes and hydrogen thereto. It is a method of obtaining a polysilicon rod.
- a cylindrical cylindrical reaction vessel made of carbon suitably constituted of isotropic graphite is heated by high frequency heating to 1200 ° C. or higher, preferably about 1300 ° C.
- FIG. 1 shows a simplified configuration of a polysilicon manufacturing apparatus according to the VLD method provided with a cylindrical reaction vessel 1.
- the deposition and melting of silicon by the VLD method is carried out, for example, after the deposition step of depositing polysilicon at a temperature less than the melting point of silicon in a cylindrical reaction vessel made of carbon as shown in Japanese Patent No. 4064918. Step of heating the temperature of the reaction vessel above the melting point of silicon, melting a part or all of the deposited silicon, dropping and recovering the deposited silicon (hereinafter referred to as "melting step"), the deposition step A method of producing silicon is preferable by repeating and melting steps.
- the temperature is approximately 1410 ° C. to 1430 ° C.
- the temperature of the cylindrical reaction vessel in the melting step is 1430 ° C. to 1700 ° C.
- the deposition step and the melting step of the VLD method are alternately performed, it is not necessary to deposit polysilicon in the melting step, so it is possible to reduce the supply amount of chlorosilanes and hydrogen. From the viewpoint of utilization, it is preferable to stop the supply of chlorosilane in the melting step, and to reduce hydrogen to 0 to 30%, more preferably 0 to 10% of the amount supplied in the deposition step. Is preferred. Furthermore, by separately flowing dilution gases such as hydrogen, nitrogen, argon, etc., the concentration of chlorosilanes in the cylindrical reaction vessel is rapidly reduced to 0.01% or less, thereby reducing the formation of polymer and silicon fine powder. Is preferred.
- the chlorosilanes supplied to the reaction vessel are tetrachlorosilane, trichlorosilane, dichlorosilane, monochlorosilane and the like, and in general, trichlorosilane gas is preferably used.
- trichlorosilane gas a high purity product having a purity of 99.99% or higher may be used, or as shown in FIG. 1, a gas obtained by separating and purifying hydrogen contained in the exhaust gas and recycling It may be described as gas).
- the hydrogen concentration in the circulating gas is not particularly specified, but is usually 90 to 99 mol%.
- reaction container may be plural, and in this case, the reaction container by Siemens method and the reaction container by VLD method may be mixed.
- the exhaust gas from these reaction vessels is introduced into a boiler-type heat recovery apparatus described later.
- the gas discharged from the deposition step includes unreacted raw material gases such as unreacted chlorosilanes and hydrogen, low polymers (polymers) such as dimers and trimers of silane compounds, and further fine powder of silicon.
- unreacted raw material gases such as unreacted chlorosilanes and hydrogen
- low polymers such as dimers and trimers of silane compounds
- the polymer composition in the exhaust gas varies depending on the operating conditions such as temperature, the generation of mist due to the condensation of the polymer described later can be suppressed by reducing the amount of by-products as much as possible. Therefore, the polymer composition in the exhaust gas is usually 0.001 to 0.1 mol%, preferably 0.001 to 0.01 mol%.
- silicon is precipitated at 1200 ° C. or higher, relatively large amounts of silicon fines are contained in the exhaust gas.
- silicon fine powder refers to silicon particles having a particle size of about 0.01 to 1 ⁇ m.
- the temperature of the exhaust gas is usually about 700 ° C. to 1200 ° C. in the case of the VLD method, and it exists as a gas other than silicon fine powder.
- the polymer may be diluted by separately supplying and mixing hydrogen before the heat recovery step.
- tetrachlorosilane is supplied as chlorosilanes, and silicon fine powder contained in the exhaust gas is reacted and reduced.
- An object of the present invention is to efficiently recover heat and unreacted source gas from the exhaust gas.
- the temperature of the generated exhaust gas is higher than that of the Siemens method. For this reason, recovery of the thermal energy from the exhaust gas in the VLD method is very important industrially, and it is particularly preferable that the present invention is applied to the exhaust gas generated by the VLD method.
- the exhaust gas from the precipitation step and the melting step is introduced into the boiler-type heat recovery apparatus 10.
- a cooling means such as providing a water cooling jacket.
- the above-mentioned mist may be generated.
- a structure and means for thermally isolating (insulation) may be used between the cooling means and the exhaust gas.
- the heat insulation structure include a structure in which a carbon material is provided on the inner wall of a pipe.
- the carbon material When the carbon material is provided on the inner wall, it is preferable to interpose a heat insulating material such as fibrous carbon, fibrous silica, etc. between the carbon material and the inner wall surface.
- the exhaust gas temperature may be adjusted by a preliminary heating device (not shown) to maintain the exhaust gas at a predetermined temperature or higher, and then the exhaust gas may be introduced into the boiler-type heat recovery device.
- the exhaust gas temperature is 100 ° C. or less, mist may be generated due to condensation of the polymer and may adhere to the inside of the pipe.
- a straight pipe type gas introduction pipe 8 is preferably installed at the front stage of the boiler type heat recovery apparatus.
- the installation of the straight pipe type gas introduction pipe 8 rectifies the flow of the gas to the boiler type heat recovery apparatus, and the gas is uniformly supplied to the exhaust gas pipe, which is more preferable.
- the inner diameter of the gas introduction pipe 8 is not limited at all, but the length may be any as long as a rectifying effect is produced, and it is not preferable industrially to make the length longer than necessary. Accordingly, the ratio (L: D) of the length L and the inner diameter D of the gas inlet tube 8 is 1: 1 to 10: 1, more preferably 1: 1 to 5: 1, particularly preferably 1: 1 to 3: 1. It is.
- the inner diameter of the lining corresponds to the inner diameter of the gas introducing pipe 8 in that case.
- the material of the gas introduction pipe may be a heat resistant material resistant to chlorosilane contained in the exhaust gas, and for example, general materials such as stainless steel and carbon steel can be used. If necessary, the inside may have a jacket structure so that heating and cooling can be performed.
- the boiler type heat recovery apparatus 10 is provided with an exhaust gas pipe 2 through which exhaust gas flows, and on the surface of the exhaust gas pipe 2 through which high temperature exhaust gas flows, a suitable refrigerant such as water or hot water. It is an apparatus which makes it contact and recovers energy as steam, and may only be called a "boiler.”
- a temperature measuring device a flow meter and a pressure gauge at the inlet and the outlet of the boiler type heat recovery apparatus 10 so that the inlet temperature and the outlet temperature of the exhaust gas, the gas flow rate and the pressure can be monitored.
- the boiler type heat recovery apparatus 10 has a refrigerant supply port 4 for supplying a refrigerant such as water or hot water, and a steam discharge port 6 for discharging the generated steam.
- the refrigerant supplied from the refrigerant supply port 4 comes in contact with the exhaust gas pipe 2, is heated and becomes steam, and is discharged from the steam outlet 6.
- the flow velocity of the exhaust gas at the outlet of the exhaust gas pipe 2 is 10 m / sec or more, it is effective in removing the mist containing the silicon fine powder and the polymer.
- the flow velocity of the exhaust gas at the outlet of the exhaust gas pipe 2 is preferably 10 to 30 m / sec, more preferably 12 to 20 m. It is preferable to set so as to be 1 / second.
- the exhaust gas flow rate at the outlet of the exhaust gas pipe 2 in the boiler type heat recovery apparatus is the amount of gas introduced from the deposition process and the melting process to the heat recovery process, the gas flow passage cross sectional area of the exhaust gas pipe 2 and the outlet gas temperature of the exhaust gas pipe 2 And the pressure of the gas at the outlet of the boiler type heat recovery apparatus.
- the gas temperature at the outlet of each exhaust gas pipe is individually measured to be the average temperature of the obtained gas temperatures.
- the gas temperature at the outlet of the boiler type heat recovery apparatus may be used.
- the gas flow passage cross-sectional area of the exhaust gas piping 2 can be obtained by multiplying the cross-sectional area of the exhaust gas piping 2 in the boiler-type heat recovery apparatus by the number n of pipings.
- the inner diameter of the exhaust gas pipe 2 is not limited at all, but the boiler type heat recovery apparatus can be designed with a general size by setting it in the range of 15 to 75 mm. Moreover, in the same boiler type
- the outer diameter of the exhaust gas pipe 2 has mechanical strength required depending on the design temperature, the design pressure and the inner diameter, and thermal strength that can withstand temperature change and heat quantity change on the heat transfer surface of the exhaust gas pipe 2 is considered. Above, it is preferable to set the minimum thickness. Industrially, the range of 2 to 10 mm, more preferably 3 to 8 mm is preferable.
- the gas flow passage cross-sectional area of the exhaust gas pipe 2 smaller than the gas flow passage cross-sectional area of the gas introduction pipe 8
- unevenness in the amount of exhaust gas flowing through the exhaust gas pipe 2 is less likely to occur, which is preferable.
- the heat transfer area of the boiler type heat recovery apparatus is reduced when the gas flow path cross sectional area is reduced, the gas flow path cross sectional area A of the exhaust gas pipe 2 in the boiler type heat recovery apparatus is determined.
- the channel cross-sectional area is B
- the area ratio of A: B is preferably 1: 1.5 to 1:10, more preferably 1: 2 to 1: 6, particularly preferably 1: 3 to 1: 5
- the material of the exhaust gas pipe 2 may be a heat-resistant material having high thermal conductivity and resistance to chlorosilane contained in the exhaust gas, and for example, general materials such as stainless steel and carbon steel can be used.
- the shape of the exhaust gas pipe 2 may be a straight pipe shape as shown in the drawing, and the inner diameter may expand, contract or bend in the length direction, but when the pipe is bent, the exhaust gas flow is biased It is preferable that it has a straight pipe shape because it causes the deposition of silicon fines.
- the number of exhaust gas pipes 2 may be set by calculating a predetermined flow rate and a number by which a predetermined heat recovery amount described later can be obtained with the set inner diameter. Also, the total length per tube can be obtained by dividing the required heat transfer area [m 2 ] by the product of the logarithmic average perimeter L [m] obtained from the set inner diameter and outer diameter and the number n of pipes. it can.
- the boiler type heat recovery apparatus needs to be in an aspect according to the use environment, but the heat recovery efficiency depends on the flow velocity of the exhaust gas in the exhaust gas pipe 2, the exhaust gas inlet temperature and the boiling point of the recovered steam.
- the design of the boiler-type heat recovery system can be performed based on the following equation, as in a general heat exchanger.
- Q is the amount of heat
- U is the overall heat transfer coefficient
- A is the heat transfer area
- DT is the effective temperature difference
- the heat quantity Q to be heat exchanged can be calculated from the enthalpy difference between the inlet and the outlet.
- the effective temperature difference DT can be calculated by determining the logarithmic average temperature of the exhaust gas inlet gas temperature Tin [° C.], the outlet gas temperature Tout [° C.] and the boiling point Tboil [° C.] of the recovered steam.
- the heat transfer area A required from Q, U, and DT determined above can be calculated by the calculation of Q / U / DT.
- a boiler type heat recovery apparatus having a small gas passage cross-sectional area corresponding to such heat quantity is separately provided, and switching from the boiler type heat recovery apparatus used in the precipitation process It is preferred to use.
- the heat of the exhaust gas can be recovered as steam energy.
- the steam discharged from the steam discharge port 6 may be further subjected to a superheat treatment as needed, introduced into a turbine or the like and used for power generation, or may be used for a vaporizer using the steam as a heat source.
- the gas temperature at the exhaust gas pipe outlet of the boiler-type heat recovery apparatus 10 may be 200 ° C. or higher, but it is preferable in consideration of the heat recovery amount and the material selection of the apparatus constituting the process downstream of the boiler-type heat recovery apparatus.
- the temperature is set to about 250 to 450 ° C., more preferably about 300 to 350 ° C. Therefore, the temperature of the exhaust gas circulating in the boiler-type heat recovery apparatus is 200 ° C. or higher.
- the temperature of the exhaust gas in the boiler type heat recovery apparatus By keeping the temperature of the exhaust gas in the boiler type heat recovery apparatus at a predetermined temperature or higher, the generation of mist or liquid pooling due to polymer condensation in the boiler type heat recovery apparatus is prevented. If the outlet gas temperature of the exhaust gas pipe 2 in the boiler-type heat recovery apparatus is less than 200 ° C., a liquid pool is generated in the boiler-type heat recovery apparatus, silicon fine powder is easily attached, and the apparatus is clogged. Cleaning is required. If the outlet gas temperature of the exhaust gas pipe 2 of the boiler type heat recovery apparatus is too high, effective recovery of heat is not performed. Therefore.
- the outlet gas temperature of the exhaust gas pipe 2 of the boiler type heat recovery apparatus is monitored by a temperature measuring device, and if the outlet gas temperature becomes too low, the gas flow rate, the refrigerant supply amount and the refrigerant temperature are adjusted, and the gas temperature at the outlet Is controlled to be equal to or higher than a predetermined temperature.
- a boiler-type heat recovery apparatus water or hot water is supplied as a refrigerant, and the refrigerant is brought into contact with the surface of a pipe through which high-temperature exhaust gas flows to recover it as steam.
- the temperature of the refrigerant supplied to the boiler-type heat recovery apparatus be close to the saturation temperature of the steam to be recovered, since the heat amount of the sensible heat until the refrigerant is vaporized results in the loss of the recovered heat.
- thermal energy is efficiently recovered by the above-described heat recovery step, and the mist containing silicon fine powder and polymer is exhausted out of the apparatus at the flow rate, so there is no residual liquid pool in the heat recovery device.
- the frequency of cleaning of the device is reduced, enabling long-term continuous operation.
- the boiler type heat recovery system has many exhaust gas pipes and is complicated in structure, so cleaning is difficult. However, by satisfying the above conditions, the frequency of cleaning the system is reduced, and the production efficiency of polysilicon is significantly increased. improves.
- the liquid chlorosilane is tetrachlorosilane, trichlorosilane, dichlorosilane or the like, and may be a mixture thereof. Among these, tetrachlorosilane having a high boiling point is preferable.
- liquid temperature of the liquid chlorosilane rises by continuing the cooling of the exhaust gas, it is preferable to hold the liquid chlorosilane 12 in a container equipped with a cooling means such as a cooling jacket.
- the exhaust gas after the cooling step contains hydrogen used as a source gas
- a known method may be used to recover hydrogen.
- a hydrogen purifier 30 which cools the cooled exhaust gas and removes chlorosilanes contained in the exhaust gas is raised. It is preferable that hydrogen be supplied to the precipitation step and be used again as the source gas, after appropriately performing purification treatment and the like as necessary.
- chlorosilanes recovered by liquid chlorosilane which is a refrigerant in the exhaust gas cooling step, is also supplied to the distillation apparatus 40 to remove impurities, and is then supplied to the deposition step, and is preferably used again as source gas.
- pressurizing means 20 such as various pumps and compressors are used.
- the raw material gas recovered through the above steps contains almost no silicon powder or polymer, and therefore does not impair the performance of the pump or the compressor.
- a rotary compressor particularly a screw compressor, which is less susceptible to the adhesion of such silicon powder and polymer is used. Is preferred.
- Example 1 Polysilicon was manufactured according to the steps shown in the flow of FIG.
- the deposition process for depositing polysilicon was performed by the VLD method.
- the temperature of the silicon deposition part of the cylindrical reaction vessel 1 was raised to 1300 ° C., the source gas was supplied, and silicon was deposited. Thereafter, by controlling heating of the cylindrical reaction container to 1600 ° C. in the melting step, silicon deposited in the cylindrical reaction container was melted and dropped and recovered. The deposition and melting steps were repeated to produce silicon.
- the reaction was carried out by supplying trichlorosilane 1200 kg / h (about 200 Nm 3 / h) gas mixture (about 2200Nm 3 / h) as a hydrogen 2000 Nm 3 / h and chlorosilanes. It was 1050 degreeC when the temperature of the waste gas discharged
- the pressure at the outlet of the boiler-type heat recovery apparatus during the precipitation step was adjusted to 50 kPaG. After tetrachlorosilane was supplied to the gas discharged from the deposition step at 100 Nm 3 / h, the exhaust gas was supplied to the boiler-type heat recovery apparatus.
- the flow of trichlorosilane and hydrogen was stopped to flow hydrogen as a dilution gas at 10 Nm 3 / h. Further, the exhaust gas generated from the precipitation step and the exhaust gas generated from the melting step were supplied to the same boiler type heat recovery apparatus.
- the ratio of the length L and the inner diameter D of the gas introduction pipe is approximately 2: 1, and the ratio of the gas flow path cross section in the boiler type heat recovery apparatus to the gas flow path cross section of the gas introduction pipe is approximately 1: 4. did.
- the inner diameter of the exhaust gas pipe 2 in the boiler type heat recovery apparatus was 45 mm.
- the exhaust gas temperature before and after the boiler type heat recovery system in the precipitation step was 950 ° C. and 250 ° C., and the initial pressure difference was about 8 kPa.
- the overall heat transfer coefficient U was estimated to be 148 W ⁇ m ⁇ 2 ⁇ k ⁇ 1 .
- the exhaust gas flow rate at the outlet of the exhaust gas pipe in the boiler type heat recovery apparatus in the precipitation step was 12 m / s.
- the gas of about 250 ° C. discharged from the boiler type heat recovery apparatus was circulated so as to blow the gas into the liquid chlorosilane 12 of the exhaust gas cooling step 14 filled with the liquid chlorosilane containing tetrachlorosilane as a main component. .
- the temperature of the gas discharged from the exhaust gas cooling step 14 was cooled to about 50.degree.
- Example 2 In the deposition step, the same operation as in Example 1 was performed except that hydrogen was increased as a source gas.
- the exhaust gas temperatures before and after the boiler type heat recovery system in the precipitation step were about 980 ° C. and 300 ° C., and the initial pressure difference was about 10 kPa.
- the overall heat transfer coefficient U was estimated to be 206 W ⁇ m ⁇ 2 ⁇ K ⁇ 1 .
- the exhaust gas flow rate at the outlet of the exhaust gas pipe in the boiler type heat recovery apparatus in the precipitation step was 19 m / s.
- Example 3 The exhaust gas pipe 2 of the boiler type heat recovery apparatus has the same inner diameter and the same number as those of the first embodiment, but the one having a total length about one third of that of the first embodiment is used. The same operation was performed. As a result, the gas temperature at the outlet of the boiler-type heat recovery apparatus was about 450.degree. Further, the exhaust gas flow rate at the exhaust gas pipe outlet in the boiler type heat recovery apparatus in the precipitation step was 16 m / s.
- Example 4 In the exhaust gas cooling step 14 of the first embodiment, other than using an exhaust gas cooling device filled with liquid chlorosilane, another device using a conventional shell and tube type heat exchanger to cool a gas using cooling water of about 30 ° C. Performed the same operation as in Example 1.
- Example 1 In the deposition step, the same operation as in Example 1 was performed except that hydrogen was reduced as a source gas.
- the exhaust gas temperatures before and after the boiler type heat recovery system in the precipitation step were about 880 ° C. and 150 ° C., and the initial pressure difference was 5 kPa.
- the overall heat transfer coefficient U was estimated to be 93 W ⁇ m ⁇ 2 ⁇ K ⁇ 1 .
- the exhaust gas flow rate at the outlet of the exhaust gas pipe in the boiler type heat recovery apparatus in the precipitation step was 5 m / s.
- Example 2 In the heat recovery step, the same operation as in Example 1 was performed except that the inside diameter of the exhaust gas pipe of the boiler type heat recovery apparatus was expanded to expand the gas flow passage cross-sectional area.
- the inner diameter of the exhaust gas pipe 2 is 45 mm to 70 mm.
- the number of exhaust gas pipes was adjusted so as not to change the heat transfer area.
- the exhaust gas temperature before and after the boiler type heat recovery system in the precipitation step was about 850 ° C. and 320 ° C., and the initial pressure difference was about 4 kPa.
- the overall heat transfer coefficient U was estimated to be 115 W ⁇ m ⁇ 2 ⁇ K ⁇ 1 .
- the exhaust gas flow rate at the outlet of the exhaust gas pipe in the boiler type heat recovery apparatus in the precipitation step was 7 m / s.
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Abstract
Description
(1)クロロシラン類を含む原料ガスによりポリシリコンを析出させる析出工程、および析出工程からの排ガスを、排ガス配管を備えたボイラー型熱回収装置に供給し熱回収する熱回収工程を備え、
前記ボイラー型熱回収装置の排ガス配管出口におけるガス温度を200℃以上とすると共に、ボイラー型熱回収装置内の排ガス配管出口における排ガス流速を10m/秒以上に調整することを特徴とするポリシリコンの製造方法。
ポリシリコンを析出させる析出工程は、特に限定はされず、従来から採用されてきたシーメンス法、VLD法などにより行われる。
析出工程及び溶融工程からの排ガスは、ボイラー型熱回収装置10に導入される。ここで排ガスは高温である為、導入配管全体も高温になることから、例えば水冷ジャケットを設ける等、冷却手段を有することが一般的である。しかしながら冷却壁面によって排ガスが冷却されると前述したミストが生成することがある。これを防ぐ為に冷却手段と排ガスの間には熱的に隔離(断熱)する構造及び手段を用いてよい。断熱構造としては例えば配管内壁にカーボン材が設けられた構造等が挙げられる。内壁にカーボン材を設ける場合、カーボン材と内壁面との間に断熱材、例えば繊維状カーボン、繊維状シリカなどを介在させることが好ましい。また、排ガスを所定温度以上に保つため予備加熱装置(図示せず)により排ガス温度を調整した後に、ボイラー型熱回収装置に排ガスを導入してもよい。一般に排ガス温度が100℃以下になると、ポリマーの凝結によりミストが発生し、配管内に付着してしまうことがある。
次いで、ボイラー型熱回収装置10から排出された排ガスを、液状クロロシラン12との接触により冷却する。液状クロロシランは、テトラクロロシラン、トリクロロシラン、ジクロロシランなどであり、これらの混合物であってもよい。これらの中でも沸点の高いテトラクロロシランが好ましい。
冷却工程後の排ガスには、原料ガスとして用いた水素が含まれるため、水素を回収する為に公知の方法を用いてよい。たとえば冷却後の排ガスを冷却し排ガス中に含まれるクロロシラン類を除去する水素精製装置30などが上げられる。適宜、必要に応じ精製処理等を施した後、水素を析出工程に供給し、再度原料ガスとして使用することが好ましい。
図1のフローに示した工程に従って、ポリシリコンを製造した。ポリシリコンを析出させる析出工程はVLD法により実施した。
円筒状反応容器1のシリコン析出部を1300℃に昇温せしめ、原料ガスを供給し、シリコンを析出させた。その後溶融工程において円筒状反応容器を1600℃に加熱制御することにより、円筒状反応容器に析出したシリコンを溶融落下させて回収した。析出工程及び溶融工程を繰り返し、シリコンを製造した。
析出工程において、原料ガスとして、水素を増加した以外は、実施例1と同様の操作を行った。
ボイラー型熱回収装置の排ガス配管2について、内径と本数は実施例1のものと同じとしつつ、全長が実施例1のものよりも約1/3のものを使用したほかは、実施例1と同様の操作を行った。その結果、ボイラー型熱回収装置の出口でのガス温度が約450℃となった。また、析出工程におけるボイラー型熱回収装置内の排ガス配管出口の排ガス流速は16m/sであった。
実施例1の排ガス冷却工程14において、液状クロロシランを充填した排ガス冷却装置にかえ、通常のシェルアンドチューブ型の熱交換器で約30℃の冷却水を用いてガスを冷却する装置を用いた他は、実施例1と同じ操作を行った。
析出工程において、原料ガスとして水素を減少させた以外は、実施例1と同様の操作を行った。
熱回収工程において、ボイラー型熱回収装置の排ガス配管の内径を拡大し、ガス流路断面積を拡大した以外は、実施例1と同じ操作を行った。
2…排ガス配管
4…冷媒供給口
6…蒸気排出口
8…ガス導入管
10…ボイラー型熱回収装置
12…液状クロロシラン
14…排ガス冷却工程
20…加圧手段
30…水素精製処理装置
40…蒸留装置
Claims (8)
- クロロシラン類を含む原料ガスによりポリシリコンを析出させる析出工程、および析出工程からの排ガスを、排ガス配管を備えたボイラー型熱回収装置に供給し熱回収する熱回収工程を備え、
前記ボイラー型熱回収装置の排ガス配管出口におけるガス温度を200℃以上とすると共に、ボイラー型熱回収装置内の排ガス配管出口における排ガス流速を10m/秒以上に調整することを特徴とするポリシリコンの製造方法。 - 熱回収工程後の排ガスを、液状クロロシランとの接触により冷却する排ガス冷却工程を含む、請求項1に記載のポリシリコンの製造方法。
- 排ガス冷却工程後の排ガスから、未反応原料ガスを回収し、析出工程に供給する工程を含む、請求項1または2に記載のポリシリコンの製造方法。
- 排ガス冷却工程における液状クロロシランから、未反応原料ガスを回収し、析出工程に供給する工程を含む、請求項2に記載のポリシリコンの製造方法。
- 析出工程からの排ガスを熱回収工程へ導入する配管において、ボイラー型熱回収装置前に、直管型のガス導入管が設置され、該ガス導入管の長さL及び内径Dの比(L:D)が1:1~5:1であることを特徴とする請求項1~4の何れかに記載のポリシリコンの製造方法。
- ボイラー型熱回収装置内の排ガス配管のガス流路断面積Aと、ボイラー型熱回収装置前のガス導入管のガス流路断面積Bの比(A:B)が1:1.5~1:10であることを特徴とする請求項1~5に記載のポリシリコンの製造方法。
- 前記析出工程が、円筒状反応容器中にて、クロロシラン類を含む原料ガスによりポリシリコンを該円筒状反応容器内壁に析出させる工程であり、析出工程の後、円筒状反応容器の温度をシリコン融点以上に加熱させ、析出させたシリコンの一部または全部を溶融させてシリコンを落下させ且つ回収する溶融工程をさらに含み、これら析出工程と溶融工程を繰り返し行うことを特徴とする請求項1~6の何れかに記載のポリシリコンの製造方法。
- ガス流路断面積が異なる複数の該ボイラー型熱回収装置が並列され、析出工程及び溶融工程より排出される排ガスを其々別々のボイラー型熱回収装置に供給することを特徴とする、請求項7に記載のポリシリコンの製造方法。
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EP13817417.2A EP2871155A4 (en) | 2012-07-09 | 2013-07-01 | PROCESS FOR PRODUCING POLYSILICON |
KR20147036932A KR20150035803A (ko) | 2012-07-09 | 2013-07-01 | 폴리실리콘의 제조 방법 |
CN201380034608.XA CN104395237A (zh) | 2012-07-09 | 2013-07-01 | 多晶硅的制造方法 |
US14/412,220 US20150175430A1 (en) | 2012-07-09 | 2013-07-01 | Method for Producing Polysilicon |
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WO2018230380A1 (ja) * | 2017-06-16 | 2018-12-20 | 株式会社トクヤマ | ポリシリコンの製造方法 |
CN114735706A (zh) * | 2022-04-27 | 2022-07-12 | 新疆大全新能源股份有限公司 | 一种多晶硅的生产还原工艺 |
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DE102017125221A1 (de) * | 2017-10-27 | 2019-05-02 | Nexwafe Gmbh | Verfahren und Vorrichtung zur Entfernung von Verunreinigungen aus Chlorsilanen |
CN108658082B (zh) * | 2018-08-31 | 2020-09-01 | 内蒙古通威高纯晶硅有限公司 | 多晶硅生产中高沸物裂解工艺 |
CN111043870A (zh) * | 2019-12-25 | 2020-04-21 | 罗智心 | 多晶硅还原炉热量回收利用系统及方法 |
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CN104395237A (zh) | 2015-03-04 |
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EP2871155A4 (en) | 2016-03-30 |
US20150175430A1 (en) | 2015-06-25 |
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