CN117534074A - Production method of granular silicon - Google Patents
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- CN117534074A CN117534074A CN202311621296.4A CN202311621296A CN117534074A CN 117534074 A CN117534074 A CN 117534074A CN 202311621296 A CN202311621296 A CN 202311621296A CN 117534074 A CN117534074 A CN 117534074A
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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 158
- 239000010703 silicon Substances 0.000 title claims abstract description 158
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 157
- 239000007789 gas Substances 0.000 claims description 133
- 238000006243 chemical reaction Methods 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 28
- 238000000576 coating method Methods 0.000 claims description 21
- 239000011248 coating agent Substances 0.000 claims description 20
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 19
- 229910000077 silane Inorganic materials 0.000 claims description 19
- 239000002994 raw material Substances 0.000 claims description 15
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 claims description 15
- 239000005052 trichlorosilane Substances 0.000 claims description 15
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 claims description 5
- IBOKZQNMFSHYNQ-UHFFFAOYSA-N tribromosilane Chemical compound Br[SiH](Br)Br IBOKZQNMFSHYNQ-UHFFFAOYSA-N 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 8
- 229910002804 graphite Inorganic materials 0.000 abstract description 7
- 239000010439 graphite Substances 0.000 abstract description 7
- 238000012423 maintenance Methods 0.000 abstract description 6
- 230000002035 prolonged effect Effects 0.000 abstract description 4
- 230000009467 reduction Effects 0.000 abstract description 3
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 230000007774 longterm Effects 0.000 abstract description 2
- 230000015572 biosynthetic process Effects 0.000 abstract 1
- 230000035882 stress Effects 0.000 description 21
- 238000010438 heat treatment Methods 0.000 description 17
- 238000000151 deposition Methods 0.000 description 14
- 230000008021 deposition Effects 0.000 description 12
- 230000006698 induction Effects 0.000 description 12
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 11
- 239000001257 hydrogen Substances 0.000 description 8
- 229910052739 hydrogen Inorganic materials 0.000 description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
- 238000001514 detection method Methods 0.000 description 7
- 229920005591 polysilicon Polymers 0.000 description 7
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 6
- 229910010271 silicon carbide Inorganic materials 0.000 description 6
- 238000005979 thermal decomposition reaction Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 238000011109 contamination Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 238000005336 cracking Methods 0.000 description 3
- 239000012212 insulator Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 230000008646 thermal stress Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 238000003306 harvesting Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 1
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
Classifications
-
- 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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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention discloses a production method of granular silicon, which is characterized in that the concentration of feed raw gas is regulated to form a concentration ring layer on the inner wall of a fluidized bed, when the deposited silicon on the inner wall of a graphite inner part reaches a certain thickness and causes a temperature difference, the stress is reduced or weakened by the concentration ring layer, the stress is prevented from directly damaging the graphite inner part on the inner wall of the fluidized bed when the stress is released, the stress of the deposited silicon on the inner wall surface of the fluidized bed is dispersed by the formation of the concentration ring layer, the continuous operation time of the fluidized bed is prolonged, the reduction of the product quality due to the breakage of the graphite part and/or the shutdown maintenance and overhaul are avoided, the long-term stable operation of the fluidized bed is realized, and the operation period of the fluidized bed is prolonged.
Description
Technical Field
The invention belongs to the field of solar photovoltaic material preparation, and in particular relates to a production method of granular silicon.
Background
High purity polysilicon is a basic raw material for integrated circuits and silicon-based solar cells, and is prepared mainly by thermally decomposing a silicon source or reducing hydrogen to obtain high purity elemental silicon, which is known in the art as Chemical Vapor Deposition (CVD). The current mainstream method for preparing high-purity polysilicon is an improved Siemens method and a fluidized bed method, which are prepared by depositing silicon-containing gas on a silicon core or seed crystal through hydrogen reduction or thermal decomposition, wherein the improved Siemens method is characterized in that the silicon core is heated to a certain temperature by using current in a metal bell-shaped reaction furnace, then hydrogen and the silicon-containing gas are introduced, after the diameter of the silicon core grows to a certain diameter to form a large-diameter silicon rod, the current is stopped from being applied to heat and the hydrogen and the silicon-containing gas are stopped from being introduced, and after the temperature is reduced to below 50-100 ℃, the silicon rod is harvested, and once the silicon rod grows to a certain diameter, the harvesting is interrupted, and the intermittent operation is performed instead of the continuous operation; the fluidized bed method is that silicon-containing gas and hydrogen are introduced into a fluidized bed with seed crystals in a fluidized bed reactor, the silicon-containing gas is thermally decomposed in the fluidized bed at 600-1200 ℃ and deposited on the seed crystals, and then the surface of the seed crystals is continuously grown to form granular polycrystalline silicon products, which are also commonly called granular silicon, and the granular polycrystalline silicon can be continuously taken out from the fluidized bed, and simultaneously, the silicon-containing gas and the hydrogen can be continuously introduced from the lower part of the fluidized bed, the seed crystals are continuously added from the upper part of the fluidized bed, and the polycrystalline silicon is continuously produced, so that the continuous operation is realized. The silicon source gases used for preparing the granular silicon comprise silane, dichlorosilane, trichlorosilane, tribromosilane and the like, the silicon source gases commonly used at present for preparing the granular silicon comprise silane gas, dichlorosilane and trichlorosilane, the temperatures of different silicon source gases for preparing granular polycrystalline silicon by reaction are different, and the silane gas and the trichlorosilane are the main materials at present; in the production process of producing granular silicon by the fluidized bed method, a fluidized bed reactor is used as a core device of the fluidized bed method.
Typical fluidized bed structures for producing granular silicon are shown in patent US005260538A, CN107364869A, CN110770167A, CN108698008A, CN105658577a, in which heat is supplied by an induction heating device or a graphite resistance heating device during the production of granular silicon by the fluidized bed process. When the graphite resistance heating device is used for providing heat, the temperature of the inner wall of the fluidized bed is higher, and more silicon is deposited on the inner wall of the fluidized bed reactor. To reduce the problem of silicon deposition on the inner wall of the reactor, US2012/230903A1 discloses a fluidized bed reactor having a gas distributor for distributing gas in the reaction chamber of the reactor, comprising a plurality of distributor openings providing a connection in fluid communication between a first gas source, a second gas source and the reaction chamber, wherein the distributor openings each have at least one central opening and one non-central opening, wherein the non-central openings are connected in fluid communication only to the first gas source and not to the second gas source, by means of which the reactor should be avoided depositing silicon on the reactor walls. The fluidized bed reactor of the patent CN107364869A adopts an induction heating device to provide heat, the induction heating device is arranged in a hollow cavity formed by an inner pipe and an outer pipe, the hollow cavity is filled with hydrogen, nitrogen or inert gas for protection, and maintains the pressure of 0.01-5 MPa, and the fluidized bed reactor of the patent CN107364869A adopts an induction heating mode to directly heat silicon particles in a reaction chamber, so that the temperature of the reaction pipe is lower than the temperature in the reaction chamber, thereby avoiding pipe wall deposition, and the heating is more uniform, the fluidized bed reactor is suitable for a large-diameter fluidized bed reactor, the production capacity of a single-set reactor is greatly improved, however, even if the induction heating is adopted, the pipe wall temperature is still higher, although the pipe wall deposition can be greatly reduced by the patent CN107364869A, the pipe wall deposition is still unavoidable, and the thickness of the pipe wall deposited silicon is gradually increased along with the operation time.
Since even with induction heating, the temperature of the inner wall of the fluidized bed reactor is still high, it is unavoidable that silicon deposits occur not only on the inner wall of the fluidized bed but also sometimes at the nozzle position of the fluidized bed inlet gas. To solve these problems, patent US2002/0102850A1 discloses a method for avoiding or removing silicon deposits on the feed gas nozzles by continuously, discontinuously or controllably metering in hcl+inert gas (H2, N2, he, ar) or inert gas H2; patent US4868013a describes a method whereby the surface of the reactor tube is cooled by spraying a cold inert gas (e.g. H2) whereby the deposition on the wall is reduced; patent US2002/0081250A1 etches away or partially etches away deposits on the walls in the reactor tubes at or near the operating temperature of the fluidized bed reactor by means of halogen-containing gaseous etchants, such as hydrogen chloride, chlorine or silicon tetrachloride; the patent CN217490804U improves the gas distributor, improves the mixing uniformity of the raw material gas, improves the reaction efficiency and the product quality by arranging the inner ring distributor and the outer ring distributor, can reduce the concentration of the raw material gas in the furnace wall area of the reaction furnace, and is beneficial to reducing the silicon forming speed of the furnace wall of the reaction furnace.
The silicon deposited on the inner wall of the fluidized bed is unfavorable for the continuous operation of the granular silicon fluidized bed, on one hand, the expansion coefficients of the fluidized bed inner wall and the silicon on the inner surface are inconsistent, the difference of the expansion coefficients can increase the cracking risk in the fluidized bed, and the long-term operation of the fluidized bed is unfavorable; on the other hand, the silicon on the inner wall of the fluidized bed can prevent the transmission of external heat, and in order to maintain the temperature required by the reaction, the power of an electric heater for induction heating or resistance heating needs to be increased, which increases the power consumption and the running cost, and meanwhile, the temperature of the furnace wall is increased due to the increase of the power of the electric heater, so that the silicon on the inner wall of the fluidized bed is accelerated, and a vicious circle is formed.
Patent CN1088444C indicates that during the production of polysilicon by the modified siemens method, the temperature difference between the inside and the outside of the polysilicon rod increases with the increase of the diameter of the polysilicon rod, resulting in a larger residual stress inside the polysilicon rod. Patent CN108698008A also indicates that in practice, due to silicon deposition occurring on hot reactor components, such as the inner walls of the reactor tubes, heat accumulation and thus thermomechanical loading of the reactor tubes, occurs until mechanical failure occurs or the deposits on the walls melt when they reach a certain thickness; furthermore, due to the constriction of the flow cross section caused by the deposits on the walls, the seed crystals can only enter the fluidized bed from above to a limited extent, which leads to reactor malfunctions, which minimize problems of silicon deposition on the hot reactor surfaces, which is of decisive importance for the economic operation of the fluidized bed process.
Furthermore, CN110770167B also indicates that a general problem affecting fluidized bed reactors may be contamination of the fluidized bed and thus of the granular polysilicon at the operating temperature of the reactor, such contamination being caused in particular by the materials of construction of the reactor, in particular the reactor tubes in which deposition occurs, for example, it has been found that nickel from nickel-containing steel diffuses into the fluidized bed and contaminates the granular silicon, other stainless steel components with a high possibility of contamination being iron and chromium. To prevent or at least minimize such contamination, ceramic liners or coatings may be used, for example, and thus WO2015/197498A1 describes a fluidized bed reactor with reactor tubes having a matrix consisting of at least 60wt% silicon carbide and having a coating consisting of at least 99.99wt% silicon carbide inside it, with the problem that the ceramic liner is subjected to thermal and mechanical stresses over its entire length, which may lead to mechanical defects.
The internal stress, the thermal stress and the mechanical stress of the silicon deposited on the inner wall of the fluidized bed can lead to the damage of the reaction tube, especially the expansion coefficient of the silicon deposited on the inner wall of the fluidized bed is inconsistent with the expansion coefficient of the lining and the coating of the inner wall of the fluidized bed, and the internal stress, the thermal stress and the mechanical stress of the silicon deposited on the inner wall of the fluidized bed are aggravated along with the increase of the thickness of the silicon deposited on the inner wall of the fluidized bed; the combined action of the internal stress, the thermal stress and the mechanical stress causes the cracking of the fluidized bed reaction tube or the cracking of the coating, for example, when the silicon deposited on the inner wall of the fluidized bed, the inner wall of the graphite and the coating are cracked together, boron, phosphorus and metal impurities on the inner wall of the graphite can escape and enter the granular silicon, so that the granular silicon product is polluted, the quality of the granular silicon product is reduced, the fluidized bed reactor is caused to stop to continue to operate, and maintenance and overhaul are performed, so that the cost of materials in the fluidized bed is increased, and shutdown loss is caused, the unit maintenance cost and depreciation cost of the granular silicon product are increased, and the economical efficiency of the operation of a fluidized bed method is reduced.
Therefore, on the basis of the prior art, there is a need to develop a method for producing granular silicon, which can reduce or/and weaken the internal stress of silicon deposited on the inner wall of a fluidized bed, reduce or/and weaken the influence on the inner wall of a fluidized bed reactor or/and the lining and coating of the inner wall of the fluidized bed, and avoid the rupture of a reaction tube inside the fluidized bed or/and the rupture of the coating on the surface of the reaction tube inside the fluidized bed, under the unavoidable condition that silicon is deposited on the inner wall of the fluidized bed when the fluidized bed is operated, thereby prolonging the continuous operation time of the fluidized bed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a method for producing granular silicon, which can reduce the influence of the internal stress of silicon on the inner wall surface of a fluidized bed reactor on the inner wall of the fluidized bed reactor or/and the lining and the coating of the inner wall of the fluidized bed, avoid the rupture of reaction tubes in the fluidized bed or/and the rupture of the coating on the surface of the reaction tubes in the fluidized bed, and prolong the continuous operation time of the fluidized bed.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the invention provides a method for producing granular silicon, which comprises the following steps:
at least 2 concentration ring layers are formed on the inner wall of the fluidized bed reactor by adjusting the volume concentration of the silicon source gas in the inlet gas when granular silicon is produced in the fluidized bed at 650-1200 ℃ after the reaction is started, so that the density of deposited silicon is different between adjacent concentration ring layers.
Further, the concentration ring layer is an annular deposition silicon layer with different densities and crystallinity formed under the concentration of the silicon source gas in different inlet gases.
Further, the silicon source gas is silane, dichlorosilane, trichlorosilane and tribromosilane.
Further, the concentration ring layer is 2-50 layers.
Further, the concentration ring layer is 5-30 layers.
Further, the difference in volume concentration of the silicon source gas concentration is 2-20% when the concentration ring layer is formed.
Further, the difference in volume concentration of the silicon source gas concentration is 5-15% when the concentration ring layer is formed.
Further, when the concentration ring layer is formed, the volume concentration of the silicon source gas in the silicon source gas concentration raw material is 2-50%.
Further, when the concentration ring layer is formed, the volume concentration of the silicon source gas in the silicon source gas concentration raw material is 10% -30%.
Further, the thickness of the concentration ring layer is 0.1-4cm.
Further, the thickness of the concentration ring layer is 0.3-1.5cm.
Further, the inner wall of the fluidized bed further comprises a coating, and the concentration ring layer is deposited on the coating of the inner wall of the fluidized bed.
Compared with the prior art, the invention has the beneficial effects that:
according to the production method of the granular silicon, the purpose of forming the concentration ring layer in a controlled way when silicon is inevitably deposited on the inner wall of the fluidized bed is achieved by adjusting the volume concentration of the silicon source gas in the feed gas, when the deposited silicon on the inner wall of the fluidized bed reaches a certain thickness, and the stress is released excessively, the released stress is weakened or reduced at the junction of the concentration ring layer, so that the purpose that the released stress is reduced or/and weakened by the concentration ring layer is achieved, the damage to the inner wall of the fluidized bed reactor or/and the inner wall lining and the coating of the fluidized bed when the internal stress of the deposited silicon on the inner wall is released is avoided, the stress difference inside the fluidized bed is reduced and weakened through the concentration ring layer, and the quality reduction of granular silicon products or the maintenance of the fluidized bed caused by the breakage of the inner wall lining and the coating of the reactor or/and the fluidized bed is avoided, thereby the continuous running time of the fluidized bed is prolonged, the running period of the fluidized bed is improved, and the economical efficiency is improved.
Drawings
FIG. 1 is a schematic view of a fluidized bed reactor according to an embodiment of the present invention;
fig. 2 and 3 are schematic views of deposition of silicon on the inner surface of a liner according to an embodiment of the present invention.
In the figure: 1. is the outer wall of the fluidized bed reactor; 2. an induction heating coil; 3. an insulator; 4. a susceptor; 5. a fluidized bed reactor inner tube; 6. a feed gas inlet; 7. the gas distributor is provided with a raw gas nozzle; 8. a tail gas outlet; 9. a granular silicon product outlet; 10. a gas distributor; 11. a seed inlet; 12. a first temperature ring layer; 13. a second temperature ring layer; 14. a third temperature ring layer; 15. and a temperature loop layer IV.
Detailed Description
The technical scheme of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. In the case described below, the embodiments described below are only some of the embodiments of the present invention, but not all of them. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In this embodiment, the concentration of the feed raw material gas, that is, the concentration of the silicon-containing gas in the raw material gas is adjusted, under the condition that the continuous production of the granular silicon is not affected, by utilizing the problem that silicon is deposited on the unavoidable wall surface of the inner wall of the fluidized bed reactor during the production of the granular silicon, a circle of deposited silicon layer is formed on the inner wall of the fluidized bed reactor under the set concentration of the feed raw material gas, when the deposited silicon on the inner wall of the reactor reaches a certain thickness, the concentration of the feed raw material gas, that is, the volume concentration of the silicon source gas in the gas inlet is adjusted, and under the new volume concentration of the silicon source gas, silicon is deposited on the inner wall of the fluidized bed reactor during the normal production of the fluidized bed, because the concentration of the silicon source gas in the gas inlet is changed, the density and the crystallinity of the silicon deposited on the surface of the fluidized bed are different, and the silicon deposited on the inner surface of the fluidized bed forms another circle of deposited silicon layer under the concentration of the silicon source gas in different gas inlets. In the present invention, annular deposited silicon layers of different densities and degrees of crystallinity formed at different concentrations of the silicon source gas in the inlet gas are referred to as concentration ring layers.
It is particularly pointed out that in the present invention, the inner wall of the fluidized bed refers to the part of the wall that is in direct contact with the gas inside the fluidized bed, and is not limited to the inner liner without a silicon carbide coating deposited on the surface or the inner liner with a silicon carbide coating deposited on the surface, for example, the inner liner without a silicon carbide coating deposited on the surface or the inner liner with a silicon carbide coating deposited on the surface is collectively referred to as the inner wall of the fluidized bed.
When the internal stress of the silicon deposited on the inner wall of the fluidized bed reactor is released, the internal stress release is reduced or/and weakened at the junction of the concentration ring layer, so that the inner wall of the fluidized bed reactor or/and the lining and coating of the inner wall of the fluidized bed reactor are prevented from being damaged when the internal stress of the silicon deposited on the inner wall of the fluidized bed reactor is released, boron, phosphorus and metal impurities are prevented from entering a reaction zone of the fluidized bed reactor, the quality of the granular silicon product is prevented from being reduced, and then the operation is stopped for overhauling, thereby prolonging the continuous operation time of the fluidized bed and improving the economical efficiency of the operation of the fluidized bed. The specific implementation mode is that the proportion of the silicon source gas and the hydrogen is regulated within a certain running time, namely the concentration of the silicon source gas entering the fluidized bed gas is regulated, and the silicon source gas in the air inlet is utilized to have low concentration, slow deposition and higher corresponding density and crystallinity; the silicon source gas in the inlet gas has high concentration, quick deposition and low corresponding density and crystallinity, so that different concentration ring layers are formed, when the silicon deposited on the inner wall of the graphite inner part reaches a certain thickness, and the temperature difference is caused, the stress is reduced or/and weakened at the junction of the concentration ring layers, so that the damage to the inner wall of the fluidized bed reactor or/and the lining and coating of the inner wall of the fluidized bed when the internal stress of the silicon deposited on the inner wall is released is avoided, the stress difference inside the deposited silicon on the inner wall of the fluidized bed is reduced through the concentration ring layers, and the continuous operation time of the fluidized bed is prolonged.
A method of producing granular silicon, the method comprising the steps of:
the silicon source gas volume concentration in the feed gas is 2% -50%, preferably 10% -30% at 650-1200 ℃, and the silicon source gas is introduced into the fluidized bed reaction zone through a gas distributor to carry out continuous thermal decomposition reaction at the reaction temperature of 650-1200 ℃ to obtain the granular silicon product. The method comprises the steps of operating a fluidized bed for 1-120h, wherein the volume concentration of silicon source gas in feed gas is 5-30%, operating the fluidized bed for 6-240h, wherein the volume concentration of silicon source gas in feed gas is 10-35%, the difference between the volume concentration of silicon source gas in feed gas of 0.1-120h and the volume concentration of silicon source gas in feed gas of 24-240h is 5% -10%, the concentration can be adjusted every 6-120 h, the concentration can be adjusted for 1-50 times, preferably adjusted for 5-30 times, and 5-30 concentration circle layers are formed. For example, in the fluidized bed granular silicon production process, after the fluidized bed starts feeding, the volume concentration of silane gas is adjusted 1 st time after 4 hours of operation, the volume concentration of silane gas is adjusted 2 nd time after 10 hours of operation of the fluidized bed, and so on, to form 1-50 concentration ring layers, preferably 5-30 concentration ring layers.
The concentration of the silicon source gas entering the fluidized bed gas may be expressed in terms of volume concentration or molar concentration, however, both expressions are consistent in nature.
The description of the above embodiment will be made with reference to a preferred embodiment.
The fluidized bed reactor used in the examples is similar to that described in patent CN106660002B, and fig. 1 is a schematic view of the structure of the fluidized bed reactor used in the examples of the present invention; the device comprises a fluidized bed reactor outer wall, a 2 induction heating coil, a 3 insulator, a 4 receptor, a 5 fluidized bed reactor inner tube, a 6 raw material gas inlet, a 7 raw material gas nozzle on a gas distributor, a 8 tail gas outlet, a 9 granular silicon product outlet, a 10 gas distributor and a 11 seed crystal inlet. 12. Temperature circle layer one, 13, temperature circle layer two, 14, temperature circle layer three, 15, temperature circle layer four. The reaction chamber cavity is the internal area of the inner wall 5 of the reactor, the hollow cavity is the area between the outer wall 1 of the reactor and the inner wall 5 of the reactor, and the induction heating coil 2, the insulator 3 and the susceptor 4 are arranged in the area. The induction heating coil 2 generates an electromagnetic field that generates eddy currents in the susceptor 4 for heating the reaction chamber cavity instead of in the fluidized bed reactor inner tube 5, the induction heating coil 2 and the susceptor 4 working together to generate heat to supply heat to the fluidized bed reactor inner tube 5. The pressure detection device is arranged in the hollow cavity, the pressure in the hollow cavity is P2, the fluidized bed tail gas outlet 8 is provided with the pressure detection device, the pressure of the fluidized bed tail gas outlet is P1, and the pressure in the reaction chamber cavity is P3, wherein P2 is more than P3 and more than P1. The pressure in the reaction chamber cavity is P3 which cannot be directly measured, and the change condition of P3 can be replaced by monitoring the change condition of P1 in operation. When the inner wall 5 of the reactor is intact, the filling gas pressure of the hollow cavity is kept unchanged, and when the inner wall 5 of the reactor breaks, the pressure detection device detects that the pressure P2 in the hollow cavity fluctuates, which indicates that the inner wall 5 of the reactor breaks.
The silicon source gas is one or more of silane, dichlorosilane, trichlorosilane and tribromosilane.
The concentration ring layer is 2-30 layers, preferably 4-20 layers, and the concentration ring layer can be deposited for a plurality of times along with the extension of continuous operation time, and is not limited to the number of layers shown in the embodiment.
The difference of the volume concentration of the silicon source gas concentration is 2-20% when the concentration ring layer is formed.
The difference in the volume concentration of the silicon source gas concentration at the time of forming the concentration ring layer is preferably 5 to 15%.
And when the concentration ring layer is formed, the volume concentration of the silicon source gas in the silicon source gas concentration raw material is 2-50%.
The silicon source gas volume concentration in the silicon source gas concentration raw material is preferably 10% -30% when the concentration ring layer is formed.
The thickness of the concentration ring layer is 0.1-4cm.
The thickness of the concentration loop layer is preferably 0.3-1.5cm.
Examples:
embodiment one:
the silicon source gas in the feed gas is trichlorosilane, and enters the reaction chamber cavity of the fluidized bed reactor through the feed gas nozzle 7 on the gas distributor 10, and the continuous thermal decomposition reaction is carried out at the reaction temperature of 1150 ℃ to prepare the granular silicon product.
As shown in fig. 2, after the reaction starts, at 1150 ℃, the volume concentration of trichlorosilane contained in the feed gas is 50%, granular silicon is continuously produced, and after 24 hours of production operation, silicon is deposited on the inner surface of the liner 5 to form a concentration ring layer one 12; at the moment, the volume concentration of the trichlorosilane contained in the feed gas is reduced to 10%, and after the feed gas runs for 72 hours with the volume concentration of the trichlorosilane contained in the feed gas being 10%, a concentration circle layer II 13 is formed on the surface of the concentration circle layer I12; the volume concentration of the trichlorosilane contained in the feed gas is adjusted to be 15%, the operation is continued for 72 hours, a concentration circle layer III 14 is formed on the surface of the concentration circle layer II 13, the volume concentration of the subsequent trichlorosilane is adjusted to be 20% and is not changed, and after the continuous operation is carried out for 60 days, the pressure detection device arranged in the hollow cavity does not detect pressure fluctuation. At this time, the maintenance is stopped, and the thickness of the first concentration ring layer 12 is 0.2 cm, the thickness of the second concentration ring layer 13 is 0.1 cm, and the thickness of the third concentration ring layer 14 is 0.2 cm.
Comparative example one:
the silicon source gas in the feed gas is trichlorosilane, and enters the reaction chamber cavity of the fluidized bed reactor through the feed gas nozzle 7 on the gas distributor 10, and the continuous thermal decomposition reaction is carried out at the reaction temperature of 1150 ℃ to prepare the granular silicon product.
After the reaction starts, the volume concentration of trichlorosilane is 50% in the feed gas at 1150 ℃, granular silicon is continuously produced, the volume concentration of the subsequent trichlorosilane is unchanged, and after the continuous operation for 10 days, the pressure fluctuation is detected by a pressure detection device arranged in the hollow cavity, which indicates that the reaction inner tube is broken, so that the gas in the hollow cavity flows into the reaction zone.
Embodiment two:
the silicon source gas in the feed gas is silane gas, and enters the reaction chamber cavity of the fluidized bed reactor through the feed gas nozzle 7 on the gas distributor 10, and the continuous thermal decomposition reaction is carried out at the reaction temperature of 800 ℃ to prepare the granular silicon product.
As shown in fig. 3, after the reaction starts, the feed gas contains silane at a volume concentration of 30% at 800 ℃, granular silicon is continuously produced, and after 24 hours of production operation, silicon is deposited on the inner surface of the liner 5 to form a concentration ring layer one 12; the volume concentration of silane in the material gas is reduced to 15 percent, and after 72 hours of operation, a second concentration ring layer 13 is formed on the surface of the first concentration ring layer 12; adjusting the volume concentration of silane contained in the feed gas to be 10%, continuing to react for 72 hours, forming a third concentration ring layer 14 on the surface of the second concentration ring layer 13, lifting the volume concentration of silane contained in the feed gas to be 20%, and forming a fourth concentration ring layer 15 on the surface of the first concentration ring layer 14 after 72 hours of operation; the volume concentration of the subsequent silane is reduced to 15%, the subsequent silane is not changed any more, and the pressure fluctuation is not detected by a pressure detection device arranged in the hollow cavity after the subsequent silane runs continuously for 85 days. At this time, the maintenance is stopped, and the thickness of the first concentration ring layer 12 is 0.1 cm, the thickness of the second concentration ring layer 13 is 0.2 cm, the thickness of the third concentration ring layer 14 is 0.1 cm, and the thickness of the third concentration ring layer 15 is 0.2 cm.
Comparative example two:
the silicon source gas in the feed gas is silane, and enters the reaction chamber cavity of the fluidized bed reactor through the feed gas nozzle 7 on the gas distributor 10, and the continuous thermal decomposition reaction is carried out at the reaction temperature of 800 ℃ to prepare the granular silicon product.
After the reaction starts, the volume concentration of silane contained in the feed gas is 12 percent at 800 ℃, granular silicon is continuously produced, the volume concentration of the subsequent silane is unchanged, and after the continuous operation for 25 days, the pressure fluctuation is detected by a pressure detection device arranged in the hollow cavity, which indicates that the reaction inner tube is broken, so that the gas in the hollow cavity flows into the reaction zone.
The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by a person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.
Claims (12)
1. A method of producing granular silicon, the method comprising the steps of:
at least 2 concentration ring layers are formed on the inner wall of the fluidized bed reactor by adjusting the volume concentration of the silicon source gas in the inlet gas when granular silicon is produced in the fluidized bed at 650-1200 ℃ after the reaction is started, so that the density of deposited silicon is different between adjacent concentration ring layers.
2. A method of producing granular silicon as claimed in claim 1 wherein the concentration ring layer is a ring-shaped deposited silicon layer of different density and crystallinity formed at the concentration of the silicon source gas in the different inlet gases.
3. The method for producing granular silicon according to claim 1, wherein the silicon source gas is silane, dichlorosilane, trichlorosilane, or tribromosilane.
4. A method of producing granular silicon as claimed in claim 1 wherein the concentration ring layer is 2 to 50 layers.
5. The method of producing granular silicon of claim 4 wherein the concentration ring layer is 5-30 layers.
6. A method of producing granular silicon as claimed in claim 1 wherein the difference in the concentration of the silicon source gas by volume at the time of forming the concentration ring layer is 2 to 20%.
7. The method of producing granular silicon according to claim 6, wherein the difference in the concentration of the silicon source gas by volume at the time of forming the concentration ring layer is 5 to 15%.
8. The method of producing granular silicon according to claim 1, wherein the silicon source gas concentration raw material has a silicon source gas volume concentration of 2 to 50% when the concentration hoop layer is formed.
9. The method of claim 8, wherein the silicon source gas concentration of the silicon source gas concentration raw material is 10% -30% by volume when forming the concentration ring layer.
10. A method of producing granular silicon as claimed in claim 1 wherein the concentrated hoop layer has a thickness of 0.1 to 4cm.
11. A method of producing granular silicon as claimed in claim 10 wherein the concentrated collar layer has a thickness of 0.3 cm to 1.5cm.
12. A method of producing granular silicon as claimed in claim 1 wherein the fluidised bed inner wall further comprises a coating, the concentrated ring layer being deposited on the fluidised bed inner wall coating.
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