CN116969467A - Novel improved Siemens process polysilicon production technology - Google Patents
Novel improved Siemens process polysilicon production technology Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 50
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 37
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 28
- 229920005591 polysilicon Polymers 0.000 title claims abstract description 22
- 238000005516 engineering process Methods 0.000 title description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 89
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 claims abstract description 86
- 239000005052 trichlorosilane Substances 0.000 claims abstract description 86
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 64
- 239000001257 hydrogen Substances 0.000 claims abstract description 62
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 53
- 239000007789 gas Substances 0.000 claims abstract description 50
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 49
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims abstract description 45
- 239000012535 impurity Substances 0.000 claims abstract description 44
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims abstract description 43
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 37
- 239000002002 slurry Substances 0.000 claims abstract description 29
- 230000009467 reduction Effects 0.000 claims abstract description 23
- 239000011863 silicon-based powder Substances 0.000 claims abstract description 23
- 239000002893 slag Substances 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 18
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 6
- 239000010703 silicon Substances 0.000 claims abstract description 6
- 238000007740 vapor deposition Methods 0.000 claims abstract description 5
- 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 claims description 33
- 239000005049 silicon tetrachloride Substances 0.000 claims description 33
- 238000001179 sorption measurement Methods 0.000 claims description 28
- 238000011084 recovery Methods 0.000 claims description 18
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 claims description 13
- 239000002918 waste heat Substances 0.000 claims description 12
- 239000003463 adsorbent Substances 0.000 claims description 11
- 239000007787 solid Substances 0.000 claims description 11
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 10
- 229910052796 boron Inorganic materials 0.000 claims description 10
- 150000002431 hydrogen Chemical class 0.000 claims description 10
- 239000000126 substance Substances 0.000 claims description 10
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 9
- 238000007323 disproportionation reaction Methods 0.000 claims description 9
- 229910052698 phosphorus Inorganic materials 0.000 claims description 9
- 239000011574 phosphorus Substances 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 238000006356 dehydrogenation reaction Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 239000000428 dust Substances 0.000 claims description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 239000003456 ion exchange resin Substances 0.000 claims description 3
- 229920003303 ion-exchange polymer Polymers 0.000 claims description 3
- 239000000741 silica gel Substances 0.000 claims description 3
- 229910002027 silica gel Inorganic materials 0.000 claims description 3
- 239000011573 trace mineral Substances 0.000 claims description 3
- 235000013619 trace mineral Nutrition 0.000 claims description 3
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 claims description 2
- 239000000460 chlorine Substances 0.000 abstract description 12
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 abstract description 10
- 229910052801 chlorine Inorganic materials 0.000 abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 7
- 238000012946 outsourcing Methods 0.000 abstract description 6
- 230000001502 supplementing effect Effects 0.000 abstract description 5
- 238000005868 electrolysis reaction Methods 0.000 abstract description 4
- 238000004458 analytical method Methods 0.000 abstract description 3
- 239000000047 product Substances 0.000 description 12
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 6
- 239000013589 supplement Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000005046 Chlorosilane Substances 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 description 2
- 238000009833 condensation Methods 0.000 description 2
- 230000005494 condensation Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005485 electric heating Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 229910003902 SiCl 4 Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000012043 crude product Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- -1 hydrogen tetrachloride Chemical class 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 150000003018 phosphorus compounds Chemical class 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 238000005406 washing Methods 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
- C01B33/035—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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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention discloses a novel improved Siemens process polysilicon production process, which comprises a hydrochloric acid resolving unit, a cold hydrogenation unit, a slurry unit, a rectifying unit, a reduction unit and a hydrogen production unit; the hydrochloric acid resolving unit is used for preparing high-purity hydrogen chloride gas, and sending the high-purity hydrogen chloride gas into the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to a rectifying unit for impurity removal, then is sent to a reduction unit together with hydrogen from a hydrogen production unit, and is subjected to vapor deposition reaction on a silicon core to obtain a polysilicon silicon rod product; the slag slurry is sent to a slag slurry unit for further treatment. According to the invention, the hydrochloric acid deep analysis device is used for supplementing chlorine and hydrogen for the system, so that the production cost is remarkably reduced compared with the process of outsourcing trichlorosilane and hydrogen production by water electrolysis. Hydrogen chloride gas is introduced into the inlet of the cold hydrogenation fluidized bed, and the hydrogen chloride gas reacts with silicon powder in the fluidized bed to prepare trichlorosilane.
Description
Technical Field
The invention belongs to the field of polysilicon production, and particularly relates to a novel improved Siemens process polysilicon production process.
Background
At present, 90% of the production process of polysilicon at home and abroad is Siemens method, which comprises the steps of placing silicon core in a reaction vessel in advance, and using SiHCl 3 、H 2 Raw material is SiHCl which enters into a reducing furnace under the high temperature condition of 1100-1200 DEG C 3 、H 2 The mixed gas of the silicon core is subjected to vapor deposition reaction on the surface of the silicon core, so that the silicon core is continuously grown and thickened into a silicon rod. At the same time, siCl is generated 4 、SiH 2 Cl 2 、H 2 And by-products such as high boiling substances. The improved Siemens method is carried out by adopting SiCl 4 、SiH 2 Cl 2 And conversion of high boiling substances to SiHCl 3 The closed circulation of the polysilicon production process is realized.
The raw material of the improved Siemens process polysilicon production process is only industrial silicon powder in an ideal state. In actual operation, the process operations of reducing furnace replacement, system overhaul replacement, tail gas emptying and the like and the treatment process of cold hydrogenation byproduct slurry can cause the loss of system hydrogen element, chlorine element and silicon element. At present, hydrogen is mostly produced by electrolysis of water to supplement hydrogen element, and finished SiHCl is purchased outsourcly 3 And supplementing chlorine and hydrogen.
In the prior art at home and abroad, impurities in chlorosilane are removed through multistage rectification, and partial impurities such as iron, copper, aluminum, calcium, manganese and other compounds can be removed easily through rectification, but because the properties of boron and phosphorus compounds are similar to those of chlorosilane, the reflux ratio is increased and the extraction amount is reduced during multistage rectification to ensure indexes. The operation process has high energy consumption, low yield and unstable product quality.
At present, the electrolytic water produces hydrogen to supplement hydrogen, and the production cost of hydrogen per mole is 0.03 yuan; the outsourcing trichlorosilane supplements hydrogen and chlorine, the production cost of each mole of hydrogen is 2.95 yuan, the production cost of each mole of chlorine is 0.98 yuan, and the production cost is relatively high. When outsourcing trichlorosilane is adopted to supplement chlorine elements of the system, the trichlorosilane is a flammable and explosive dangerous chemical, and the risk of highway transportation, loading and unloading safety is high. The trichlorosilane rectifying device needs a plurality of large rectifying towers to remove impurities in the trichlorosilane, so that the investment cost of the rectifying device is huge, the product quality is unstable, and the energy consumption is large.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, the invention provides an improved Siemens method polysilicon production process for supplementing chlorine and hydrogen and reducing cost.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a novel improved Siemens process polysilicon production process comprises a hydrochloric acid resolving unit, a cold hydrogenation unit, a slurry unit, a rectifying unit, a reduction unit and a hydrogen production unit; the hydrochloric acid resolving unit is used for preparing high-purity hydrogen chloride gas, and sending the high-purity hydrogen chloride gas into the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to a rectifying unit for impurity removal, then is sent to a reduction unit together with hydrogen from a hydrogen production unit, and is subjected to vapor deposition reaction on a silicon core to obtain a polysilicon silicon rod product; the slag slurry is sent to a slag slurry unit for further treatment.
Specifically, the cold hydrogenation unit mixes preheated silicon tetrachloride and hydrogen, then mixes the preheated hydrogen tetrachloride and hydrogen with hydrogen chloride from the hydrochloric acid resolving unit after electric heating, and sends the mixture into a cold hydrogenation fluidized bed to react with silicon powder in the fluidized bed to generate trichlorosilane, hydrogen and slag slurry; and (3) extracting mixed gas of trichlorosilane, hydrogen which is not completely reacted and silicon tetrachloride from the top of the cold hydrogenation fluidized bed, feeding the mixed gas into a dust removal condensation separation device after passing through a waste heat recovery heat exchanger to obtain crude trichlorosilane and hydrogen, pressurizing the hydrogen by a recycle hydrogen compressor, re-preheating the hydrogen, and feeding the hydrogen into the cold hydrogenation fluidized bed again as a raw material.
Further, part of hydrogen chloride generated by the hydrochloric acid resolving unit is sent into the cold hydrogenation fluidized bed through a first tube pass, and the other part of hydrogen chloride is mixed with mixed gas extracted from the top of the cold hydrogenation fluidized bed through a second tube pass to react with silicon powder entrained in gas phase at an outlet of the fluidized bed and silicon powder attached to the inner wall of the waste heat recovery heat exchanger.
Specifically, the rectification unit comprises a baffle rectification tower, a first adsorption tower, a dehydrogenation rectification tower and a heavy removal rectification tower which are connected in sequence; separating dichlorosilane and trace silicon tetrachloride in crude trichlorosilane from a cold hydrogenation unit through a baffle rectifying tower, and then removing boron and phosphorus trace elements in the trichlorosilane by entering a first adsorption tower; sequentially entering a light component removal rectifying tower and a heavy component removal rectifying tower, and removing part of trichlorosilane with higher impurity concentration from the tower top and the tower bottom respectively; and finally, high-purity trichlorosilane is adopted from the top of the heavy-removal rectifying tower and is sent to a reduction unit.
Further, the cut materials in the baffle rectifying tower, the dehydrogenation rectifying tower and the heavy removal rectifying tower are sent into the second adsorption tower together for impurity removal, and then are mixed with crude trichlorosilane sent into the rectifying unit, and the mixture is re-sent into the baffle rectifying tower for impurity removal.
Further, the process also comprises a tail gas recovery unit and a disproportionation unit; the reduction tail gas generated by the reduction unit is sent to a tail gas recovery unit to separate silicon tetrachloride, trichlorosilane, hydrogen chloride and high-boiling-point substances; the method comprises the steps that trichlorosilane is sent into a reduction unit again, silicon tetrachloride, hydrogen chloride and part of silicon tetrachloride are sent into a cold hydrogenation unit, and the other part of silicon tetrachloride is sent into an anti-disproportionation unit; the high-boiling-point substances are sent into a slag slurry unit.
Further, the dichlorosilane extracted by the rectification unit is sent to an anti-disproportionation unit to react with silicon tetrachloride, and the generated trichlorosilane is returned to the rectification unit again to remove impurities and then sent to a reduction unit.
Further, the silicon tetrachloride and the trichlorosilane generated by the separation of the slag-slurry unit are sent to a cold hydrogenation unit for reaction.
Further, a part of the high-purity hydrogen chloride gas prepared by the hydrochloric acid resolving unit is sent into the slag slurry unit.
Further, the first adsorption tower or the second adsorption tower is filled with a solid adsorbent, and the solid adsorbent is selected from any one of activated alumina, activated carbon, silica gel or ion exchange resin.
The beneficial effects are that:
(1) According to the invention, the hydrochloric acid analysis device is used for supplementing chlorine and hydrogen elements to the system, so that the production cost is remarkably reduced compared with the process of outsourcing trichlorosilane and hydrogen production by water electrolysis. Hydrogen chloride gas is introduced into the inlet of the cold hydrogenation fluidized bed, and the hydrogen chloride gas reacts with silicon powder in the fluidized bed to prepare trichlorosilane. Meanwhile, the reaction is exothermic, so that the operation load of an electric heater of the cold hydrogenation reaction device can be reduced. Hydrogen chloride gas is introduced into the outlet pipeline of the fluidized bed, so that the hydrogen chloride gas can react with silicon powder attached to the inner wall of the waste heat recovery heat exchange device, the heat transfer efficiency of the waste heat recovery heat exchanger can be effectively ensured, and the service cycle of the device is prolonged.
(2) Compared with the traditional rectification impurity removal process, the invention can greatly reduce the equipment investment of the rectification tower by adding the fixed bed adsorption tower to the rectification device. The process index of the large-scale rectifying tower in the traditional rectifying process can be realized by using a smaller-scale rectifying tower. The crude trichlorosilane is firstly subjected to component separation to remove dichlorosilane and silicon tetrachloride, so that adverse effects of polar molecular dichlorosilane on removal of trace impurities by an adsorption device can be reduced. Impurities in the trichlorosilane are concentrated through the light removal rectifying tower and the heavy removal rectifying tower, and then the impurities are removed through the fixed bed absorption device, so that microelements in the trichlorosilane can be efficiently removed, the trichlorosilane can be recovered, and the system loss is reduced. Compared with the traditional large rectifying tower, the solid adsorbent has higher efficiency and higher product purity, and can realize the replacement due to the solid adsorbent, so that the product quality is stable.
Drawings
The foregoing and/or other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings and detailed description.
FIG. 1 is a schematic flow chart of a novel improved Siemens process polysilicon production process of the present invention.
FIG. 2 is a schematic flow diagram of a cold hydrogenation unit of the present invention.
FIG. 3 is a schematic flow diagram of a rectification unit of the present invention.
Detailed Description
The invention will be better understood from the following examples.
As shown in figure 1, the novel improved Siemens process polysilicon production process comprises a hydrochloric acid resolving unit, a cold hydrogenation unit, a slurry unit, a rectifying unit, a reduction unit and a hydrogen production unit; the hydrochloric acid resolving unit is used for preparing high-purity hydrogen chloride gas, and sending the high-purity hydrogen chloride gas into the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to a rectifying unit for impurity removal, then is sent to a reduction unit together with hydrogen from a hydrogen production unit, and is subjected to vapor deposition reaction on a silicon core to obtain a polysilicon silicon rod product; the slag slurry is sent to a slag slurry unit for further treatment.
The outsourcing hydrochloric acid of the invention is prepared into high-purity hydrogen chloride gas through a deep resolution process, the high-purity hydrogen chloride gas is pressurized to 3.2-3.5 MPa through a compressor and then is sent into a cold hydrogenation fluidized bed, and the reaction Si+3HCl= =SiHCl occurs 3 +H 2 The system is supplemented with chlorine and hydrogen.
Referring to fig. 2, the cold hydrogenation unit mixes the preheated silicon tetrachloride and hydrogen, and then sends the mixture into a cold hydrogenation fluidized bed after electric heating. Meanwhile, hydrogen chloride gas from the hydrochloric acid resolving unit is conveyed to an inlet of a cold hydrogenation fluidized bed through a pipeline to react with silicon powder in the fluidized bed to generate Trichlorosilane (TCS), hydrogen and slag slurry; and (3) extracting mixed gas of trichlorosilane, hydrogen which is not completely reacted and silicon tetrachloride from the top of the cold hydrogenation fluidized bed, feeding the mixed gas into a dust removal condensation separation device after passing through a waste heat recovery heat exchanger to obtain crude trichlorosilane and hydrogen, pressurizing the hydrogen by a recycle hydrogen compressor, re-preheating the hydrogen, and feeding the hydrogen into the cold hydrogenation fluidized bed again as a raw material.
In the invention, one part of hydrogen chloride generated by the hydrochloric acid resolving unit is sent into the cold hydrogenation fluidized bed through the first tube pass, and the other part of hydrogen chloride is mixed with mixed gas extracted from the top of the cold hydrogenation fluidized bed through the second tube pass, and reacts with silicon powder entrained in gas phase at an outlet of the fluidized bed and silicon powder attached to the inner wall of the waste heat recovery heat exchanger, so that the production load of a dust removal system can be effectively reduced.
Referring to fig. 3, the rectification unit includes a separator rectification column, a first adsorption column, a dehydrogenation rectification column, and a heavy removal rectification column connected in this order; separating Dichlorosilane (DCS) and trace Silicon Tetrachloride (STC) in crude Trichlorosilane (TCS) from a cold hydrogenation unit through a baffle rectifying tower, and then removing trace elements such as boron, phosphorus and the like in the trichlorosilane by entering a first adsorption tower; sequentially entering a light component removal rectifying tower and a heavy component removal rectifying tower, and cutting off part of Trichlorosilane (TCS) with higher impurity concentration from the tower top and the tower bottom respectively; finally, high-purity Trichlorosilane (TCS) is adopted from the top of the heavy removal rectifying tower and is sent to a reduction unit.
The cut materials in the baffle rectifying tower, the dehydrogenation rectifying tower and the heavy removal rectifying tower are sent into a second adsorption tower together for impurity removal, and then are mixed with crude Trichlorosilane (TCS) sent into the rectifying unit, and the mixture is re-sent into the baffle rectifying tower for impurity removal. And adsorbing and removing impurities from the Trichlorosilane (TCS) with the impurity content enriched by using a solid adsorbent, and recovering the Trichlorosilane (TCS) after the impurities are removed.
The first adsorption tower or the second adsorption tower is filled with solid adsorbent, and the solid adsorbent is selected from substances with larger specific surface area and larger surface activity. For example: activated alumina, activated carbon, silica gel, ion exchange resins, and the like.
With reference to fig. 1, the process of the present invention further comprises a tail gas recovery unit and a disproportionation unit; the reduction tail gas generated by the reduction unit is sent to a tail gas recovery unit to separate silicon tetrachloride, trichlorosilane, hydrogen chloride and high-boiling-point substances; the method comprises the steps that trichlorosilane is sent into a reduction unit again, silicon tetrachloride, hydrogen chloride and part of silicon tetrachloride are sent into a cold hydrogenation unit, and the other part of silicon tetrachloride is sent into an anti-disproportionation unit; the high-boiling-point substances are sent into a slag slurry unit.
The dichlorosilane extracted by the rectifying unit is sent to the anti-disproportionation unit to react with silicon tetrachloride, and the generated trichlorosilane returns to the rectifying unit again to remove impurities and then is sent to the reduction unit.
And sending the silicon tetrachloride and trichlorosilane generated by the separation of the slag-slurry unit into a cold hydrogenation unit for reaction.
And part of the high-purity hydrogen chloride gas prepared by the hydrochloric acid resolving unit is sent into the slag slurry unit.
According to the invention, the hydrochloric acid analysis device is used for supplementing chlorine and hydrogen elements to the system, so that the production cost is remarkably reduced compared with the process of outsourcing trichlorosilane and hydrogen production by water electrolysis. Hydrogen chloride gas is introduced into the inlet of the cold hydrogenation fluidized bed, and the hydrogen chloride gas reacts with silicon powder in the fluidized bed to prepare trichlorosilane. Meanwhile, the reaction is exothermic, so that the operation load of an electric heater of the cold hydrogenation reaction device can be reduced. Hydrogen chloride gas is introduced into the outlet pipeline of the fluidized bed, so that the hydrogen chloride gas can react with silicon powder attached to the inner wall of the waste heat recovery heat exchange device, the heat transfer efficiency of the waste heat recovery heat exchanger can be effectively ensured, and the service cycle of the device is prolonged.
By adding the fixed bed adsorption tower in the rectifying device, compared with the traditional rectifying impurity removal process, the equipment investment of the rectifying tower can be greatly reduced. The process index of the large-scale rectifying tower in the traditional rectifying process can be realized by using a smaller-scale rectifying tower. The crude trichlorosilane is firstly subjected to component separation to remove dichlorosilane and silicon tetrachloride, so that adverse effects of polar molecular dichlorosilane on removal of trace impurities by an adsorption device can be reduced. Impurities in the trichlorosilane are concentrated through the light removal rectifying tower and the heavy removal rectifying tower, and then the impurities are removed through the fixed bed absorption device, so that microelements in the trichlorosilane can be efficiently removed, the trichlorosilane can be recovered, and the system loss is reduced. Compared with the traditional large rectifying tower, the solid adsorbent has higher efficiency and higher product purity, and can realize the replacement due to the solid adsorbent, so that the product quality is stable.
Examples
The main production raw materials of the invention are industrial silicon powder, 30% hydrochloric acid and water, and the product is polysilicon. The product of the hydrochloric acid resolving unit is high-purity hydrogen chloride with the water content of less than 20 ppm. For use in the downstream preparation of trichlorosilane.
The traditional process flow for preparing trichlorosilane by using the cold hydrogenation unit by the improved Siemens method is as follows: mixing hydrogen and silicon tetrachloride after heating and vaporizing, wherein the mixing molar ratio is 2.5-2.8, heating to 540-550 ℃, then introducing into a fluidized bed to react with silicon powder (reaction equation (2)), and obtaining a crude product of trichlorosilane through waste heat recovery, washing and dedusting, cooling and separating and rectifying and separating.
As shown in the combination of FIG. 1 and FIG. 2, the cold hydrogenation process of the invention is to introduce high-purity hydrogen chloride gas into a mixed fluid pipeline of high-temperature hydrogen and silicon tetrachloride (first pipe pass of FIG. 2), add the reaction process of silicon powder and hydrogen chloride into a fluidized bed, generate trichlorosilane and hydrogen by the reaction, and release a large amount of heat energy (reaction equation (1)). Trichlorosilane is a product of a cold hydrogenation device, and hydrogen can be used as a raw material in the reaction process (2).
Si + 3HCL ＝＝＝ SiHCl 3 + H 2 ①
According to the invention, the hydrogen chloride pipeline (the second tube side in the figure 2) is added to the gas phase outlet pipeline of the cold hydrogenation fluidized bed, and part of fine silicon powder particles with the particle size smaller than 50 mu m are entrained in the gas phase at the outlet of the fluidized bed and gradually adhere to the wall of the waste heat recovery heat exchanger, so that the heat exchange efficiency is affected. As shown in the second tube side process of FIG. 2, hydrogen chloride is added to be introduced into the pipeline to react with fine silica powder particles, so that the influence of silica powder wall adhesion on heat exchange efficiency is reduced.
The crude trichlorosilane containing 98% trichlorosilane, 2% dichlorosilane, 50ppbw of phosphorus impurities and 150ppbw of boron impurities prepared by the cold hydrogenation unit is sent to a rectification unit (figure 3). Separating in a baffle rectifying tower, wherein the temperature of the tower top is 80 ℃, the pressure is 0.32MPa, dichlorosilane and light component impurities are extracted from the tower top, and trichlorosilane carrying heavy component impurities is extracted from the tower bottom. The side-stream extracted trichlorosilane is sent to a first adsorption tower, the adsorption temperature is 0-25 ℃, the adsorption pressure is 0.55-0.6 Mpa, and the impurity of the trichlorosilane produced by the first adsorption tower is less than that of the trichlorosilane: boron 20ppbw, phosphorus 5ppbw. And delivering the adsorbed trichlorosilane to a light component removal tower to remove part of light component impurities, and delivering the light component impurities to a heavy component removal tower to remove heavy component impurities to obtain high-purity trichlorosilane with boron impurities less than 0.05ppbw and phosphorus impurities less than 0.03 ppbw.
The cut materials of the tower bottoms of the baffle rectifying tower, the tower top of the light component removing tower and the tower bottom of the heavy component removing tower are pressurized by pump equipment and then are conveyed to a second adsorption tower, and boron and phosphorus impurities in trichlorosilane are concentrated by the baffle rectifying tower, the light component removing tower and the heavy component removing tower: the boron content is 50ppbw and the phosphorus content is 15ppbw, and the high concentration of impurities is favorable for the adsorption of the impurities. The adsorption temperature is 0-25 ℃, and the adsorption pressure is 0.55-0.6 Mpa. The impurity content of the product after passing through the adsorption tower is less than 0.1ppbw of boron and 0.1ppbw of phosphorus. The partially cut material is returned to the inlet of the baffle rectifying tower.
The invention provides a new idea and a method for improving the polysilicon production process by the Siemens method, and particularly the method and the way for realizing the technical scheme are numerous, the above is only a preferred embodiment of the invention, and it should be pointed out that a plurality of improvements and modifications can be made to those skilled in the art without departing from the principle of the invention, and the improvements and modifications are also considered as the protection scope of the invention. The components not explicitly described in this embodiment can be implemented by using the prior art.
Claims (10)
1. The novel improved Siemens process polysilicon production process is characterized by comprising a hydrochloric acid resolving unit, a cold hydrogenation unit, a slurry unit, a rectifying unit, a reduction unit and a hydrogen production unit; the hydrochloric acid resolving unit is used for preparing high-purity hydrogen chloride gas, and sending the high-purity hydrogen chloride gas into the cold hydrogenation unit to react with silicon powder to generate crude trichlorosilane, hydrogen and slag slurry; the crude trichlorosilane is sent to the rectifying unit for impurity removal, then is sent to the reduction unit together with the hydrogen from the hydrogen production unit, and is subjected to vapor deposition reaction in a silicon core to obtain a polysilicon silicon rod product; and sending the slag slurry into the slag slurry unit for further treatment.
2. The novel improved siemens process polysilicon production process according to claim 1, characterized in that the cold hydrogenation unit mixes preheated silicon tetrachloride and hydrogen, then mixes the preheated silicon tetrachloride and hydrogen with hydrogen chloride from the hydrochloric acid resolving unit, sends the mixture into a fluidized bed of the cold hydrogenation unit, and reacts with silicon powder in the fluidized bed to generate trichlorosilane, hydrogen and slag slurry; and extracting mixed gas of trichlorosilane, hydrogen which is not completely reacted and silicon tetrachloride from the top of the cold hydrogenation fluidized bed, sending the mixed gas into a dust removal condensing separation device after passing through a waste heat recovery heat exchanger to obtain crude trichlorosilane and hydrogen, pressurizing the hydrogen by a circulating hydrogen compressor, re-preheating the hydrogen, and sending the hydrogen as a raw material into the cold hydrogenation fluidized bed again.
3. The process for producing polycrystalline silicon by a novel improved siemens method according to claim 2, characterized in that a part of hydrogen chloride generated by the hydrochloric acid resolving unit is sent into the cold hydrogenation fluidized bed through a first tube pass, and the other part of hydrogen chloride is mixed with mixed gas extracted from the top of the cold hydrogenation fluidized bed through a second tube pass to react with silicon powder entrained in gas phase at an outlet of the fluidized bed and silicon powder attached to the inner wall of the waste heat recovery heat exchanger.
4. The novel process for producing polycrystalline silicon by the improved siemens process according to claim 1, characterized in that the rectification unit comprises a baffle rectification tower, a first adsorption tower, a dehydrogenation rectification tower and a de-duplication rectification tower which are connected in sequence; separating dichlorosilane and trace silicon tetrachloride in crude trichlorosilane from a cold hydrogenation unit through a baffle rectifying tower, and then removing boron and phosphorus trace elements in the trichlorosilane by entering a first adsorption tower; sequentially entering a light component removal rectifying tower and a heavy component removal rectifying tower, and removing part of trichlorosilane with higher impurity concentration from the tower top and the tower bottom respectively; and finally, high-purity trichlorosilane is adopted from the top of the heavy-removal rectifying tower and is sent to a reduction unit.
5. The process for producing polycrystalline silicon by a novel improved siemens process according to claim 4, characterized in that the cut materials in the baffle rectifying tower, the dehydrogenation rectifying tower and the heavy removal rectifying tower are sent into the second adsorption tower together for impurity removal, and then are mixed with crude trichlorosilane sent into the rectifying unit, and enter the baffle rectifying tower again for impurity removal.
6. The novel modified siemens process polysilicon production process of claim 1, further comprising a tail gas recovery unit and a reverse disproportionation unit; the reduction tail gas generated by the reduction unit is sent to a tail gas recovery unit to separate silicon tetrachloride, trichlorosilane, hydrogen chloride and high-boiling-point substances; the method comprises the steps that trichlorosilane is sent into a reduction unit again, silicon tetrachloride, hydrogen chloride and part of silicon tetrachloride are sent into a cold hydrogenation unit, and the other part of silicon tetrachloride is sent into an anti-disproportionation unit; the high-boiling-point substances are sent into a slag slurry unit.
7. The novel process for producing polycrystalline silicon by an improved siemens method according to claim 1, characterized in that dichlorosilane extracted by the rectification unit is sent to an anti-disproportionation unit to react with silicon tetrachloride, and the generated trichlorosilane is returned to the rectification unit again to remove impurities and then is sent to a reduction unit.
8. The novel process for producing polycrystalline silicon by the improved siemens method according to claim 1, characterized in that silicon tetrachloride and trichlorosilane generated by the separation of the slag-slurry unit are sent to a cold hydrogenation unit for reaction.
9. The novel improved siemens process polysilicon production process of claim 1 wherein a portion of the high purity hydrogen chloride gas produced by the hydrochloric acid resolution unit is fed into the slurry unit.
10. The process for producing polycrystalline silicon by the new improved siemens process according to claim 4 or 5, characterized in that the first adsorption tower or the second adsorption tower is filled with a solid adsorbent, and the solid adsorbent is selected from any one of activated alumina, activated carbon, silica gel or ion exchange resin.
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