CN116067220A - Cleaning method suitable for heat exchanger for semiconductor grade polysilicon production - Google Patents
Cleaning method suitable for heat exchanger for semiconductor grade polysilicon production Download PDFInfo
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- CN116067220A CN116067220A CN202310103461.0A CN202310103461A CN116067220A CN 116067220 A CN116067220 A CN 116067220A CN 202310103461 A CN202310103461 A CN 202310103461A CN 116067220 A CN116067220 A CN 116067220A
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- 238000004140 cleaning Methods 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 40
- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 38
- 239000004065 semiconductor Substances 0.000 title claims abstract description 34
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 229920005591 polysilicon Polymers 0.000 title abstract description 20
- 238000005406 washing Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 14
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 12
- 238000005238 degreasing Methods 0.000 claims abstract description 11
- 238000011010 flushing procedure Methods 0.000 claims abstract description 11
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 9
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000005554 pickling Methods 0.000 claims abstract description 8
- 239000012498 ultrapure water Substances 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 239000002518 antifoaming agent Substances 0.000 claims abstract description 4
- 238000002156 mixing Methods 0.000 claims abstract description 4
- 239000004094 surface-active agent Substances 0.000 claims abstract description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 5
- -1 polytetrafluoroethylene Polymers 0.000 claims description 4
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 4
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 3
- 230000007935 neutral effect Effects 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 7
- 239000003153 chemical reaction reagent Substances 0.000 description 6
- 238000002791 soaking Methods 0.000 description 6
- 238000001514 detection method Methods 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 231100000252 nontoxic Toxicity 0.000 description 3
- 230000003000 nontoxic effect Effects 0.000 description 3
- 230000000536 complexating effect Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000002161 passivation Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 231100000331 toxic Toxicity 0.000 description 2
- 230000002588 toxic effect Effects 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000013043 chemical agent Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
- F28G9/00—Cleaning by flushing or washing, e.g. with chemical solvents
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
-
- 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
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Thermal Sciences (AREA)
- Physics & Mathematics (AREA)
- Combustion & Propulsion (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Cleaning Or Drying Semiconductors (AREA)
Abstract
The invention relates to the technical field of polysilicon production, in particular to a cleaning method suitable for a heat exchanger for semiconductor grade polysilicon production, which comprises the following steps of S1: connecting the heat exchanger to be cleaned; s2: washing with desalted water; s3: uniformly mixing a sodium hydroxide solution, a surfactant and an anti-foaming agent, and degreasing the heat exchanger; s4: flushing the heat exchanger with desalted water; s5: pickling the heat exchanger by using a nitric acid solution and a hydrofluoric acid solution; s6: flushing the heat exchanger with desalted water; s7: passivating the heat exchanger by using a nitric acid solution with the mass fraction of 18%; s8: washing with desalted water; s9: the heat exchanger is cleaned in a flushing mode that the heat exchanger is filled with high-purity water; s10: the heat exchanger was dried with nitrogen. The invention can improve the cleaning efficiency of the heat exchanger and the cleaning effect of the heat exchanger.
Description
Technical Field
The invention relates to the technical field of polysilicon production, in particular to a cleaning method suitable for a heat exchanger for semiconductor grade polysilicon production.
Background
The semiconductor grade polysilicon is used as an upstream basic raw material of the integrated circuit silicon chip, has very wide application in the field of electronic information, and the hysteresis of China in the production capacity thereof seriously hinders the development of the integrated circuit industry in China, and the requirement on the production process is very severe due to the high purity characteristic thereof, so that the technical barrier is brought, and a great challenge is provided for the continuous development of the industry. In the process of producing semiconductor grade polysilicon by adopting an improved Siemens method, heat exchange between a plurality of cold and hot fluids is involved, so that the utilization efficiency of energy sources is improved, the production cost of enterprises is reduced, the production efficiency of the enterprises is improved, and a large number of heat exchangers are widely applied to the field of polysilicon. Because the material is in direct contact with the inner wall of the heat exchanger during the production of semiconductor grade polysilicon, the heat exchanger is usually required to be cleaned before use in order to ensure that the purity of the produced polysilicon meets the requirements of semiconductor grade polysilicon.
The cleaning method of the heat exchanger in the prior art mainly comprises the following steps: the soaking tank is connected with the heating circulation tank through the circulating pump, equipment is soaked in cleaning liquid in the soaking tank, one end of the equipment is connected with a cleaning liquid inlet of the soaking tank through a pipeline, the other end of the equipment is connected with a cleaning liquid outlet of the soaking tank through a pipeline, the all-round cleaning of the inner wall and the outer wall of the pipe is realized, and the plurality of soaking tanks are simultaneously cleaned through the serial connection of the circulating pump. However, the method can wash the outer wall of the heat exchanger, which inevitably causes waste of cleaning liquid, and the method washes a plurality of soaking tanks in a serial connection mode, so that the cleaning efficiency is low, and the risk of excessive corrosion of a head pipeline or incomplete cleaning of a tail pipeline is caused.
Secondly, the cleaning is carried out by a chemical complexing cleaning method, a large amount of chemical reagents are adopted in the method, the working procedure is complicated, the reaction rate of the adopted complexing cleaning method is slow, and the complex cleaning method can definitely cause the increase of the production cost; in addition, the cleaning liquid adopted by the method contains a large amount of organic solvent, and the risk of carbon content residue exists after the cleaning, which is very unfavorable for the production of semiconductor grade polysilicon; some reagents are highly toxic or potentially toxic, creating a safety risk; in addition, the turbidity is not detected in the cleaning process, so whether the surface cleanliness of the heat exchanger cleaned by the method is suitable for the production of semiconductor grade polysilicon is still to be confirmed.
Thirdly, degreasing, acidifying and drying the equipment by only potassium hydroxide. The method adopts nitric acid or a rust remover to remove rust, the rust is directly dried after removal, passivation treatment is not carried out on the rust remover before drying, and in the using process of a subsequent device, the risk that residues on the inner wall of a pipe react with materials is large, so that the problem that the materials are polluted is caused.
Disclosure of Invention
In view of the above, the present invention provides a cleaning method suitable for a heat exchanger for producing semiconductor grade polysilicon, and mainly aims to improve the cleaning efficiency of the heat exchanger, improve the cleaning effect of the heat exchanger, and enable the cleaned heat exchanger to meet the requirement of producing high-purity semiconductor grade polysilicon.
In order to achieve the above purpose, the present invention mainly provides the following technical solutions:
the embodiment of the invention provides a cleaning method suitable for a heat exchanger for producing semiconductor grade polycrystalline silicon, which comprises the following steps:
s1: connecting a tube side and a shell side of the heat exchanger to be cleaned with polytetrafluoroethylene lining hoses;
s2: washing the heat exchanger with desalted water until the turbidity of the inner wall of the heat exchanger is less than 5ppm;
s3: uniformly mixing 5% sodium hydroxide solution, 0.3% -0.5% surfactant and anti-foaming agent at 55-75 ℃, and degreasing the heat exchanger; degreasing until no fluorescence is detected by using a purple light lamp;
s4: washing the heat exchanger with desalted water for 3h until the turbidity of the inner wall of the heat exchanger is less than 5ppm and the pH value is neutral;
s5: pickling the heat exchanger by using a nitric acid solution with the mass fraction of 18% and a hydrofluoric acid solution with the mass fraction of 2%; acid washing until the measured acidity is 20%, wherein the total iron content is less than 35g/L;
s6: flushing the heat exchanger with desalted water; until the turbidity, the conductivity and the pH value of the inlet and the outlet of the heat exchanger are unchanged;
s7: passivating the heat exchanger by using a nitric acid solution with the mass fraction of 18%; until the detected total iron content value is 0, the acidity is 18%, and the pH value is less than 1;
s8: washing the heat exchanger with desalted water until the turbidity and pH value of the inlet and outlet of the heat exchanger are unchanged after washing; the electrical conductivity of the outlet is less than 0.8 mu.S/cm;
s9: washing the heat exchanger in a flushing mode of filling the heat exchanger with high-purity water until the turbidity and the pH value of an inlet and an outlet of the heat exchanger are unchanged after washing; the electrical conductivity of the outlet is less than 0.4 mu.S/cm;
s10: and drying the heat exchanger by adopting nitrogen with the dew point of less than-60 ℃.
Further, in S1, the tube passes of the heat exchangers are connected in parallel; the shell passes of the plurality of heat exchangers are connected in parallel.
Further, the tube side of the heat exchanger is cleaned first, and then the shell side of the heat exchanger is cleaned.
In S2 to S9, the washing liquid is circulated by flowing in the lower inlet and upper outlet.
Further, in S2, S4, S6, S8, the heat exchanger is rinsed with desalted water for 3-4 hours.
Further, in S3, the heat exchanger is subjected to degreasing treatment for 4 to 5 hours.
Further, in S5, the heat exchanger is subjected to an acid washing treatment for 3 to 5 hours.
Further, in S7, the heat exchanger is subjected to passivation treatment for 2 to 3 hours.
Further, in S9, the heat exchanger is rinsed with high purity water for 2 to 3 hours.
Further, in S10, the heat exchanger is dried for 4 to 5 hours by nitrogen.
By means of the technical scheme, the cleaning method suitable for the heat exchanger for producing the semiconductor grade polycrystalline silicon has at least the following advantages:
the cleaning efficiency of the heat exchanger can be improved, and the cleaning effect of the heat exchanger is improved.
The invention adopts a mode of parallel connection of heat exchangers to realize a high-efficiency and high-quality cleaning mode of the heat exchangers, adopts nontoxic, low-cost and effective chemical agents, circularly degreasing, pickling, passivating and washing with high-purity water in a lower-in and upper-out mode, then uses high-purity dry gas to dry, optimizes cleaning reagent components, concentration and cleaning conditions, reasonably detects the whole cleaning process flow in an efficient detection mode, and finally cleans the heat exchangers meeting the conditions for producing high-purity semiconductor grade polycrystalline silicon.
The foregoing description is only an overview of the present invention, and is intended to provide a better understanding of the present invention, as it is embodied in the following description, with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
Fig. 1 is a flowchart of a method for cleaning a heat exchanger for producing semiconductor grade polysilicon according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of pipeline connection of a heat exchanger in a cleaning method suitable for a heat exchanger for semiconductor grade polysilicon production according to an embodiment of the present invention.
Detailed Description
In order to further describe the technical means and effects adopted for achieving the preset aim of the invention, the following detailed description refers to the specific implementation, structure, characteristics and effects according to the application of the invention with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.
As shown in fig. 1 and 2, a cleaning method suitable for a heat exchanger for producing semiconductor grade polysilicon according to an embodiment of the present invention includes the following steps:
s1: connecting a tube side and a shell side of the heat exchanger to be cleaned through a pipeline; before the pipeline connection, all pipe orifices can be pretreated before cleaning, and the pump station is self-cleaned. Preferably, in S1, the tube passes of a plurality of heat exchangers are connected in parallel; the shell passes of the plurality of heat exchangers are connected in parallel. Can realize cleaning a plurality of heat exchangers simultaneously, and can not cause the pollution each other. Only the tube side and the shell side of the heat exchanger are cleaned, the outer side of the heat exchanger is not cleaned, and the waste of chemical reagents is reduced.
S2: washing the heat exchanger with desalted water until the turbidity of the inner wall of the heat exchanger is less than 5ppm; preferably, the heat exchanger is subjected to desalted water washing in S3 for 3-4 hours.
S3: uniformly mixing 5% sodium hydroxide solution, 0.3% -0.5% surfactant and anti-foaming agent at 55-75 ℃, and degreasing the heat exchanger; degreasing treatment until detection using a violet lamp showed no fluorescence. Preferably, in S3, the heat exchanger is degreased for 4-5 hours to meet the cleaning requirements in the current cleaning environment.
S4: washing the heat exchanger with desalted water for 3h until the turbidity of the inner wall of the heat exchanger is less than 5ppm and the pH value is neutral; preferably, the heat exchanger is subjected to desalted water washing in S4 for 3-4 hours.
S5: pickling the heat exchanger by using a nitric acid solution with the mass fraction of 18% and a hydrofluoric acid solution with the mass fraction of 2%; the pickling treatment is carried out until the measured acidity is 20%, and the total iron content is less than 35g/L. Preferably, in S5, the heat exchanger is subjected to pickling treatment for 3-5 hours to meet the cleaning requirements in the current cleaning environment.
S6: flushing the heat exchanger with desalted water; until the turbidity, the conductivity and the pH value of the inlet and the outlet of the heat exchanger are unchanged. Preferably, in S6, the heat exchanger is subjected to a desalted water rinse for at least 2 hours to achieve the cleaning requirements in the current cleaning environment.
S7: passivating the heat exchanger by using a nitric acid solution with the mass fraction of 18%; until the detected total iron content value is 0; acidity 18%; the pH value is less than 1. Preferably, in S7, the heat exchanger is passivated for 2-3 hours to meet the cleaning requirements in the current cleaning environment.
S8: washing the heat exchanger with desalted water until the turbidity and pH value of the inlet and outlet of the heat exchanger are unchanged after washing; the electrical conductivity of the outlet is less than 0.8 mu.S/cm; preferably, the heat exchanger is subjected to desalted water washing in S8 for 3-4 hours.
S9: the heat exchanger is cleaned in a flushing mode that the heat exchanger is filled with high-purity water; until the turbidity and the pH value of the inlet and the outlet of the heat exchanger are unchanged after cleaning; the electrical conductivity of the outlet is less than 0.4 mu.S/cm; preferably, in S9, the heat exchanger is cleaned with high purity water for 2-3 hours to meet the cleaning requirements in the current cleaning environment.
S10: and drying the heat exchanger by adopting nitrogen with the dew point of less than-60 ℃. Preferably, in S10, the heat exchanger is dried for 4-5 hours by nitrogen so as to meet the cleaning requirement in the current cleaning environment.
In this embodiment, the tube side of the heat exchanger is preferably cleaned first, and then the shell side of the heat exchanger is cleaned. So as to meet the high clean requirement of the tube side. When the shell side is cleaned, a valve is added at a low point at a position where polytetrafluoroethylene lining hose connection is not performed, and blind sealing is performed at a high point; after the shell side is passivated, the flange at the blind seal position is required to be washed cleanly, and then the whole water washing is carried out. Preferably, the shell side is cleaned once in parallel and the tube side is cleaned once in parallel.
In the preferred embodiments, in S2 to S9, the flow mode of the flushing liquid is the lower inlet and upper outlet, and the circulating cleaning is performed, so as to achieve a better cleaning effect.
When the heat exchanger is cleaned by the cleaning method suitable for the heat exchanger for producing the semiconductor grade polysilicon, the pipe orifices of all the heat exchangers can be cleaned first, the pump station is cleaned automatically, then polytetrafluoroethylene lining hose connection is carried out, and the pipe side and the shell side of the heat exchanger are cleaned respectively.
The cleaning method for the heat exchanger for producing the semiconductor grade polycrystalline silicon provided by the embodiment of the invention can improve the cleaning efficiency of the heat exchanger and the cleaning effect of the heat exchanger.
According to the cleaning method suitable for the heat exchanger for producing the semiconductor grade polycrystalline silicon, provided by the embodiment of the invention, the heat exchanger is cleaned by adopting a nontoxic, low-cost and effective chemical reagent, and corresponding detection is carried out on each cleaning step in combination with an efficient detection mode, so that the cleaned heat exchanger meets the requirement of producing the high-purity semiconductor grade polycrystalline silicon.
According to the cleaning method suitable for the heat exchanger for the semiconductor grade polycrystalline silicon production, provided by the embodiment of the invention, the heat exchangers can be cleaned simultaneously by adopting a nontoxic, low-cost and effective chemical reagent and adopting a parallel cleaning mode, the heat exchangers can be cleaned without causing pollution, and each cleaning step is reasonably detected by combining an efficient detection mode, so that the finally cleaned heat exchanger meets the requirement of producing high-purity semiconductor grade polycrystalline silicon.
In the description of the present invention, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "secured" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Standard parts used in the invention can be purchased from the market, special-shaped parts can be customized according to the description of the specification and the drawings, the specific connection modes of all parts adopt conventional means such as mature bolts, rivets and welding in the prior art, the machinery, the parts and the equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection modes in the prior art, so that the details are not described.
The above description is only of the preferred embodiments of the present invention, and is not intended to limit the present invention in any way, but any simple modification, equivalent variation and modification made to the above embodiments according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.
Claims (10)
1. The cleaning method suitable for the heat exchanger for producing the semiconductor grade polycrystalline silicon is characterized by comprising the following steps of:
s1: connecting a tube side and a shell side of the heat exchanger to be cleaned with polytetrafluoroethylene lining hoses;
s2: washing the heat exchanger with desalted water until the turbidity of the inner wall of the heat exchanger is less than 5ppm;
s3: uniformly mixing 5% sodium hydroxide solution, 0.3% -0.5% surfactant and anti-foaming agent at 55-75 ℃, and degreasing the heat exchanger; degreasing until no fluorescence is detected by using a purple light lamp;
s4: washing the heat exchanger with desalted water for 3h until the turbidity of the inner wall of the heat exchanger is less than 5ppm and the pH value is neutral;
s5: pickling the heat exchanger by using a nitric acid solution with the mass fraction of 18% and a hydrofluoric acid solution with the mass fraction of 2%; acid washing until the measured acidity is 20%, wherein the total iron content is less than 35g/L;
s6: flushing the heat exchanger with desalted water; until the turbidity, the conductivity and the pH value of the inlet and the outlet of the heat exchanger are unchanged;
s7: passivating the heat exchanger by using a nitric acid solution with the mass fraction of 18%; until the detected total iron content value is 0, the acidity is 18%, and the pH value is less than 1;
s8: washing the heat exchanger with desalted water until the turbidity and pH value of the inlet and outlet of the heat exchanger are unchanged after washing; the electrical conductivity of the outlet is less than 0.8 mu.S/cm;
s9: washing the heat exchanger in a flushing mode of filling the heat exchanger with high-purity water until the turbidity and the pH value of an inlet and an outlet of the heat exchanger are unchanged after washing; the electrical conductivity of the outlet is less than 0.4 mu.S/cm;
s10: and drying the heat exchanger by adopting nitrogen with the dew point of less than-60 ℃.
2. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
s1, the tube passes of a plurality of heat exchangers are connected in parallel; the shell passes of the plurality of heat exchangers are connected in parallel.
3. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
the tube side of the heat exchanger is cleaned firstly, and then the shell side of the heat exchanger is cleaned.
4. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S2-S9, the flow mode of the flushing liquid is lower inlet and upper outlet, and the circulating cleaning is carried out.
5. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S2, S4, S6 and S8, the heat exchanger is subjected to desalted water washing for 3-4 hours.
6. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S3, degreasing treatment is carried out on the heat exchanger for 4-5 hours.
7. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S5, the heat exchanger is subjected to pickling treatment for 3-5 hours.
8. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S7, passivating the heat exchanger for 2-3 hours.
9. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S9, the heat exchanger is cleaned with high purity water for 2-3 hours.
10. The method for cleaning a heat exchanger for semiconductor grade polycrystalline silicon production according to claim 1, wherein,
in S10, the heat exchanger is dried for 4 to 5 hours by nitrogen.
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2023
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