CN110078261B - Method and system for treating wastewater - Google Patents
Method and system for treating wastewater Download PDFInfo
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- CN110078261B CN110078261B CN201910418342.8A CN201910418342A CN110078261B CN 110078261 B CN110078261 B CN 110078261B CN 201910418342 A CN201910418342 A CN 201910418342A CN 110078261 B CN110078261 B CN 110078261B
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- 239000002351 wastewater Substances 0.000 title claims abstract description 170
- 238000000034 method Methods 0.000 title claims abstract description 90
- 239000003513 alkali Substances 0.000 claims abstract description 235
- 239000002699 waste material Substances 0.000 claims abstract description 165
- 239000002253 acid Substances 0.000 claims abstract description 156
- 238000005406 washing Methods 0.000 claims abstract description 121
- 239000007788 liquid Substances 0.000 claims abstract description 97
- 239000006228 supernatant Substances 0.000 claims abstract description 61
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000000463 material Substances 0.000 claims abstract description 49
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 37
- 238000002156 mixing Methods 0.000 claims abstract description 27
- 238000001914 filtration Methods 0.000 claims abstract description 16
- 239000002893 slag Substances 0.000 claims abstract description 11
- 230000003472 neutralizing effect Effects 0.000 claims abstract description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 87
- 238000004062 sedimentation Methods 0.000 claims description 70
- 238000004140 cleaning Methods 0.000 claims description 60
- 238000006386 neutralization reaction Methods 0.000 claims description 55
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 40
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 34
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 24
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims description 23
- 229910002804 graphite Inorganic materials 0.000 claims description 23
- 239000010439 graphite Substances 0.000 claims description 23
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 20
- 229910017604 nitric acid Inorganic materials 0.000 claims description 20
- 239000007787 solid Substances 0.000 claims description 18
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 13
- 238000000926 separation method Methods 0.000 claims description 10
- 235000008733 Citrus aurantifolia Nutrition 0.000 claims description 6
- 235000011941 Tilia x europaea Nutrition 0.000 claims description 6
- 239000004571 lime Substances 0.000 claims description 6
- 238000005554 pickling Methods 0.000 claims description 6
- 239000000920 calcium hydroxide Substances 0.000 claims description 4
- 229910001861 calcium hydroxide Inorganic materials 0.000 claims description 4
- 239000013049 sediment Substances 0.000 claims description 2
- 239000000758 substrate Substances 0.000 claims 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 32
- 230000008901 benefit Effects 0.000 abstract description 22
- 230000007613 environmental effect Effects 0.000 abstract description 19
- 230000008569 process Effects 0.000 description 45
- 238000004519 manufacturing process Methods 0.000 description 15
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 15
- 229920005591 polysilicon Polymers 0.000 description 13
- -1 fluoride ions Chemical class 0.000 description 9
- 238000004064 recycling Methods 0.000 description 9
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 8
- 229910052731 fluorine Inorganic materials 0.000 description 8
- 239000011737 fluorine Substances 0.000 description 8
- 239000012535 impurity Substances 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 230000007797 corrosion Effects 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 239000013505 freshwater Substances 0.000 description 6
- 229920002401 polyacrylamide Polymers 0.000 description 6
- 239000003518 caustics Substances 0.000 description 5
- 238000006115 defluorination reaction Methods 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000004065 wastewater treatment Methods 0.000 description 4
- 230000006378 damage Effects 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 238000001556 precipitation Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- RPAJSBKBKSSMLJ-DFWYDOINSA-N (2s)-2-aminopentanedioic acid;hydrochloride Chemical class Cl.OC(=O)[C@@H](N)CCC(O)=O RPAJSBKBKSSMLJ-DFWYDOINSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 239000011863 silicon-based powder Substances 0.000 description 2
- 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 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000000701 coagulant Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000009297 electrocoagulation Methods 0.000 description 1
- 238000000909 electrodialysis Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 229920000592 inorganic polymer Polymers 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000008267 milk Substances 0.000 description 1
- 210000004080 milk Anatomy 0.000 description 1
- 235000013336 milk Nutrition 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 239000008247 solid mixture Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 description 1
- 239000005052 trichlorosilane Substances 0.000 description 1
- 238000000108 ultra-filtration Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F2001/007—Processes including a sedimentation step
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/12—Halogens or halogen-containing compounds
- C02F2101/14—Fluorine or fluorine-containing compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/12—Nature of the water, waste water, sewage or sludge to be treated from the silicate or ceramic industries, e.g. waste waters from cement or glass factories
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Removal Of Specific Substances (AREA)
- Separation Of Suspended Particles By Flocculating Agents (AREA)
Abstract
The invention discloses a method and a system for treating wastewater, wherein the method comprises the following steps: (1) Neutralizing waste acid obtained by acid washing of a lump material washing machine and/or a silicon core washing machine with alkali liquor so as to obtain neutralized waste water; (2) Mixing and settling acid-containing wastewater obtained by washing the lump material washing machine and/or the silicon core washing machine with the neutralized wastewater and a settling agent, and filtering to obtain waste residues and waste liquid; (3) Settling the waste alkali to obtain supernatant and settled slag; (4) Mixing the supernatant with alkali-containing wastewater and the waste liquid so as to obtain a prepared alkali liquor, and returning the prepared alkali liquor to the step (1) to be used as the alkali liquor. The method can reduce the treatment capacity of the acid washing wastewater by 60%, save water by 50%, reduce the use amount of the neoalkali by 50%, and has excellent economic and environmental benefits.
Description
Technical Field
The invention belongs to the field of polysilicon production, and particularly relates to a method and a system for treating wastewater.
Background
Polysilicon is an important base material in the information industry and solar photovoltaic, and is a national strategic material. At present, the domestic polysilicon is mainly produced by adopting an improved Siemens method. The improved Siemens method is to utilize trichlorosilane and hydrogen to carry out vapor deposition reaction in a CVD reduction furnace, and deposit and form a polysilicon rod on a prefabricated silicon core.
The post-treatment process of the polysilicon product is the last processing process of polysilicon production, and the main production task is to process the polysilicon rod produced in the reducing furnace to generate the final product. The post-treatment process of the polysilicon product mainly comprises four aspects: crushing and packaging, silicon core processing, graphite piece processing and product detection. In the post-treatment process of the polysilicon product, the mixture of hydrofluoric acid and nitric acid is used for carrying out acid washing on part of silicon blocks with impurities on the surfaces and processed silicon cores, and the surface impurities on the silicon blocks and the silicon cores are cleaned. A large amount of wastewater containing hydrofluoric acid and nitric acid is generated in the cleaning process, the wastewater has strong corrosiveness, and high requirements are put on corrosion resistance of pipelines of conveying equipment, so that equipment investment is large, the wastewater contains a large amount of fluoride ions, and the discharge of the wastewater containing fluorine has great influence on the environment.
At present, the methods for treating industrial fluorine-containing wastewater at home and abroad mainly comprise a precipitation method, an adsorption method, a freezing method, an ion exchange resin defluorination method, a liquid membrane method, a reverse osmosis method, an ultrafiltration defluorination method, an active carbon defluorination method, an electrodialysis method, an electrocoagulation method, a co-distillation method and the like. The industrial treatment of waste water with high acid fluorine content mainly adopts precipitation method, uses lime milk to neutralize acidity of waste water, and adds PAC solution (polymerized Al) 2 O 3 Inorganic polymer coagulant) and PAM solution precipitation (polyacrylamide, nonionic polymer flocculant), and can realize better defluorination effect. The process has the advantages of small dosage, simple method, convenient treatment, low cost and the like.
The cleaning of the silicon blocks and the silicon cores is respectively carried out in a block cleaning machine and a silicon core cleaning machine, the processes of acid washing, water washing, drying and the like are respectively carried out in the cleaning machines, and waste acid discharged by acid washing and acid-containing waste water discharged by water washing in the cleaning process are mixed and then sent to a fluorine-containing waste water treatment process. The waste acid and the acid-containing waste water are intermittently discharged in the cleaning process, the concentration of hydrofluoric acid and nitric acid in the waste acid is high, and the acid-containing waste water only contains trace hydrofluoric acid and nitric acid, and a large amount of acid waste water is generated after the waste acid and the acid-containing waste water are mixed, so that the treatment load of the downstream process is high, a large amount of alkali liquor is needed for neutralizing the acidity of the waste acid, the investment cost is high, and the environmental pollution is serious.
Accordingly, the technology of waste acid obtained by acid washing and acid-containing wastewater obtained by water washing of the existing lump material washing machine and/or silicon core washing machine is still further improved.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, an object of the present invention is to propose a method and a system for treating wastewater. The method can reduce the treatment capacity of the acid washing wastewater by 60%, save water by 50%, reduce the use amount of the neoalkali by 50%, and has excellent economic and environmental benefits.
In one aspect of the invention, the invention provides a method of treating wastewater, the method comprising, according to an embodiment of the invention:
(1) Neutralizing waste acid obtained by acid washing of a lump material washing machine and/or a silicon core washing machine with alkali liquor so as to obtain neutralized waste water;
(2) Mixing and settling acid-containing wastewater obtained by washing the lump material washing machine and/or the silicon core washing machine with the neutralized wastewater and a settling agent, and filtering to obtain waste residues and waste liquid;
(3) Settling the waste alkali to obtain supernatant and settled slag;
(4) Mixing the supernatant with alkali-containing wastewater and the waste liquid so as to obtain a prepared alkali liquor, and returning the prepared alkali liquor to the step (1) to be used as the alkali liquor.
According to the method for treating wastewater, disclosed by the embodiment of the invention, the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is subjected to neutralization treatment with the alkali liquor, and then the acid-containing wastewater obtained by water washing of the lump material washing machine and/or the silicon core washing machine is mixed with the neutralized wastewater and the sedimentation agent for sedimentation, so that the amount of the neutralized waste acid and the consumption of the alkali liquor in the neutralization process can be remarkably reduced, the conveying amount of the acid wastewater can be reduced, and the requirement on corrosion resistance of conveying equipment is reduced; the supernatant, the alkali-containing wastewater and the waste liquid are mixed to prepare the alkali liquid, and the prepared alkali liquid is returned to be used as the alkali liquid, so that the recycling of the waste liquid and the waste alkali can be realized, the internal circulation of materials is realized, the discharge amount of the final waste liquid is reduced, the use amount of fresh water and fresh alkali in the process of preparing the alkali liquid can be obviously reduced, and the economic and environmental benefits of the process are improved. Therefore, by adopting the method, the treatment capacity of the pickling wastewater can be reduced by 60%, the water consumption can be saved by 50%, the use amount of the neoalkali can be reduced by 50%, and the method has excellent economic and environmental benefits.
In addition, the method for treating wastewater according to the above embodiment of the present invention may have the following additional technical features:
in some embodiments of the invention, in step (1), the spent acid from the block washer and/or the silicon core washer acid wash is added to the lye for the neutralization treatment to obtain the neutralized wastewater. Therefore, the damage to people and the environment caused by boiling in the neutralization process due to high concentration of waste acid can be avoided.
In some embodiments of the invention, in step (1), the mass ratio of the spent acid to the lye is 1:10-50. Thereby, it is advantageous to improve the neutralization efficiency while avoiding an excessively rapid temperature rise during the neutralization.
In some embodiments of the invention, in step (1), the concentration of hydrofluoric acid in the spent acid is 10-30wt% and the concentration of nitric acid is 30-60wt%.
In some embodiments of the invention, in step (1), the lye concentration is 20 to 52.6wt%. Thereby, the neutralization efficiency can be further improved.
In some embodiments of the invention, in step (1), the lye is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide. Thereby, the neutralization efficiency can be further improved.
In some embodiments of the invention, in step (2), the concentration of hydrofluoric acid in the acid-containing wastewater is 0.1-0.3wt% and the concentration of nitric acid is 0.3-0.6wt%.
In some embodiments of the invention, in step (2), the settling agent is at least one selected from lime, PAM, PAC, caustic soda. Thus, the sedimentation efficiency and effect can be further improved.
In some embodiments of the invention, in step (2), the mass ratio of the acid-containing wastewater to the neutralized wastewater to the settling agent is 100:1000-2000:1. thus, the sedimentation efficiency and effect can be further improved.
In some embodiments of the invention, in step (3), the spent caustic is a caustic wash of a graphite piece washer. Therefore, the internal consumption of materials in the production process of the polycrystalline silicon can be further realized, and the cost is further saved.
In some embodiments of the invention, in step (3), the concentration of the supernatant is 35-45wt%. Thereby being beneficial to improving the quality of the prepared alkali liquor.
In some embodiments of the invention, in step (3), the supernatant is at least one selected from the group consisting of sodium hydroxide solution, potassium hydroxide solution, and calcium hydroxide solution. Thus, the quality of the prepared alkali liquor can be further improved.
In some embodiments of the invention, in step (4), the alkali-containing wastewater has a concentration of 0.1 to 10wt%.
In some embodiments of the invention, in step (4), the alkali-containing wastewater is at least one selected from a sodium hydroxide solution, a potassium hydroxide solution, and a calcium hydroxide solution.
In some embodiments of the invention, in step (4), the alkali-containing wastewater is obtained by washing the graphite piece with water. Therefore, the internal consumption of materials in the production process of the polycrystalline silicon can be further realized, and the cost is further saved.
In some embodiments of the invention, in step (4), the mass ratio of the supernatant to the alkali-containing wastewater, the waste liquid is 1-50:10-50:1. thus, the quality of the prepared alkali liquor can be further improved.
In a further aspect of the invention, the invention proposes a system for implementing the above-mentioned method of treating wastewater, comprising, according to an embodiment of the invention:
the neutralization device is provided with a waste acid inlet, an alkali liquor inlet and a neutralized waste water outlet;
the first sedimentation device is provided with an acid-containing wastewater inlet, a neutralized wastewater inlet, a sedimentation agent inlet and a settled mixture outlet, and the neutralized wastewater inlet is connected with the neutralized wastewater outlet;
the filtering device is provided with a mixture inlet after sedimentation, a waste residue outlet and a waste liquid outlet, and the mixture inlet after sedimentation is connected with the mixture outlet after sedimentation;
the second sedimentation device is provided with a waste alkali inlet, a supernatant outlet and a sediments outlet;
the mixing device is provided with a supernatant inlet, an alkali-containing wastewater inlet, a waste liquid inlet and an alkali liquor outlet, wherein the supernatant inlet is connected with the supernatant outlet, the waste liquid inlet is connected with the waste liquid outlet, and the alkali liquor outlet is connected with the alkali liquor inlet.
According to the system for treating wastewater, disclosed by the embodiment of the invention, the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is subjected to neutralization treatment with the alkali liquor, and then the acid-containing wastewater obtained by water washing of the lump material washing machine and/or the silicon core washing machine is mixed with the neutralized wastewater and the sedimentation agent for sedimentation, so that the amount of the neutralized waste acid and the consumption of the alkali liquor in the neutralization process can be remarkably reduced, the conveying amount of the acid wastewater can be reduced, and the requirement on corrosion resistance of conveying equipment is reduced; the supernatant, the alkali-containing wastewater and the waste liquid are mixed to prepare the alkali liquid, and the prepared alkali liquid is returned to be used as the alkali liquid, so that the recycling of the waste liquid and the waste alkali can be realized, the internal circulation of materials is realized, the discharge amount of the final waste liquid is reduced, the use amount of fresh water and fresh alkali in the process of preparing the alkali liquid can be obviously reduced, and the economic and environmental benefits of the process are improved. Therefore, by adopting the system, the treatment capacity of the pickling wastewater can be reduced by 60%, the water consumption can be saved by 50%, the use amount of the neoalkali can be reduced by 50%, and the system has excellent economic and environmental benefits.
In addition, the system for treating wastewater according to the above embodiment of the present invention may have the following additional technical features:
in some embodiments of the invention, the neutralization device is a tank or reservoir with a stirrer.
In some embodiments of the invention, the first settling device and the second settling device are each independently a settling tank or a settling pond.
In some embodiments of the invention, the filtration device is a liquid-solid separation tank or a liquid-solid separation cell.
In some embodiments of the invention, the mixing device is a tank or reservoir with a stirrer.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic flow diagram of a method of treating wastewater according to one embodiment of the invention;
fig. 2 is a schematic diagram of a system for treating wastewater according to one embodiment of the invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
In one aspect of the invention, the invention provides a method of treating wastewater, in accordance with an embodiment of the invention, with reference to fig. 1, the method comprising:
s100: neutralizing waste acid and alkali liquor obtained by acid washing of lump material cleaning machine and/or silicon core cleaning machine
In the step, waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is subjected to neutralization treatment with alkali liquor so as to obtain neutralized waste water. Specifically, hydrofluoric acid in waste acid and hydrogen ions in nitric acid are subjected to chemical reaction with hydroxyl ions in alkali liquor to generate water, and the alkali liquor for treating the waste acid needs to be excessive in order to avoid too fast temperature rise of the solution in the neutralization process due to large reaction heat of the neutralization reaction. Further, waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine can be added into alkali liquor for neutralization treatment so as to obtain neutralized waste water. The inventor finds that the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is added into alkali liquor for neutralization treatment, instead of adding the alkali liquor into the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine, the phenomenon that the waste acid boils when the alkali liquor is added and the like, which causes harm to people and environment, can be avoided.
According to one embodiment of the invention, the mass ratio of spent acid to lye may be 1:10-50, for example, can be 1:10/20/30/40/50. The inventor finds that if the mass ratio of the waste acid to the alkali liquor is too large, the content of the waste acid is high, the temperature of the solution rises too fast in the neutralization process, and a fuming phenomenon can occur; if the mass ratio of the waste acid to the alkali liquor is too small, the alkali liquor content is high, so that the waste of the alkali liquor is caused, and the production cost is increased. Further, the concentration of hydrofluoric acid in the waste acid can be 10-30wt%, such as 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, and the concentration of nitric acid can be 30-60wt%, such as 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%. The concentration of the lye may be 20-52.6 wt.%, for example 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 52.6 wt.%. The inventor finds that the condition that the alkali liquor has too high concentration, the moisture content in the solution is low, and the temperature of the solution rises too fast in the neutralization process; the concentration of the alkali liquor is too low, the water quantity used for preparing the alkali liquor is increased, and waste is caused. Further, the alkali liquor is at least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide. When the alkali is neutralized with waste acid obtained by acid washing of a lump material cleaning machine and/or a silicon core cleaning machine, the reaction rate is high, and the neutralization effect is good.
S200: mixing acid-containing wastewater obtained by washing a lump material washing machine and/or a silicon core washing machine with neutralized wastewater and a sedimentation agent for sedimentation
In the step, acid-containing wastewater obtained by washing a lump material washing machine and/or a silicon core washing machine is mixed with neutralized wastewater and a sedimentation agent for sedimentation, and waste residue and waste liquid are obtained after filtration. Specifically, fluoride ions in the acid-containing wastewater and the neutralized wastewater can react with a sedimentation agent to generate fluorine-containing solids, and separation of the fluorine-containing solids from liquid can be realized after sedimentation and filtration. The inventor finds that the waste acid obtained by acid washing of the lump material cleaning machine and/or the silicon core cleaning machine is firstly subjected to neutralization treatment with alkali liquor, and then the acid-containing waste water obtained by water washing of the lump material cleaning machine and/or the silicon core cleaning machine is mixed with the neutralized waste water and a sedimentation agent for sedimentation, so that the amount of the neutralized waste acid and the amount of the alkali liquor used in the neutralization process can be remarkably reduced, the conveying amount of the acid waste water can be reduced, and the requirement on corrosion resistance of conveying equipment can be reduced. Further, the concentration of hydrofluoric acid in the acid-containing wastewater may be 0.1 to 0.3wt%, for example, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, and the concentration of nitric acid may be 0.3 to 0.6wt%, for example, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%. Further, the sedimentation agent may be at least one selected from lime, PAM, PAC, caustic soda. Further, the mass ratio of the acid-containing wastewater to the neutralized wastewater to the sedimentation agent can be 100:1000-2000:1, for example, may be 100:1000/1200/1400/1600/1800/2000:1. the inventor finds that when the consumption of the sedimentation agent is small, the fluoride ions in the acid-containing wastewater and the neutralized wastewater cannot be completely removed, so that the fluoride ion concentration in the waste liquid is still high, and the discharge requirement of the wastewater is not met; when the usage amount of the sedimentation agent is large, the sedimentation agent is wasted, and the production cost is increased.
S300: settling the waste alkali
In this step, the spent caustic is subjected to a sedimentation treatment so as to obtain a supernatant and a sedimented slag. Specifically, the waste alkali contains a small amount of silicon powder or other solid impurities, and after sedimentation and liquid-solid separation, the solid impurities in the waste alkali can be removed in the form of sedimentation slag to obtain supernatant. Further, the concentration of the supernatant may be 35 to 45wt%, for example, 35wt%, 37wt%, 39wt%, 41wt%, 43wt%, 45wt%. Further, the supernatant may be at least one selected from a sodium hydroxide solution, a potassium hydroxide solution, and a calcium hydroxide solution. Further, the waste alkali can be obtained by alkali washing of a graphite piece cleaning machine. The inventor finds that the graphite piece cleaning machine is used in the production process of polysilicon, the waste liquid obtained by alkaline cleaning is adopted as waste alkali for sedimentation, the obtained supernatant is used for subsequent alkali preparation, the obtained alkali preparation is returned to S100 to be used as alkali, the recycling of the waste liquid obtained by alkaline cleaning of the graphite piece cleaning machine can be realized, the treatment cost of waste acid obtained by acid cleaning of the block cleaning machine and/or the silicon core cleaning machine is obviously reduced, and meanwhile, the water consumption and the new alkali amount can be obviously saved because no new alkali is required to be prepared, and the economic and environmental benefits are obvious.
S400: mixing the supernatant with alkali-containing wastewater and waste liquid
In the step, the supernatant is mixed with alkali-containing wastewater and waste liquid so as to obtain a prepared alkali liquor, and the prepared alkali liquor is returned to S100 to be used as alkali liquor. Specifically, the concentration of alkali in the supernatant is higher, and alkali liquor meeting the requirement of S100 can be obtained by mixing the supernatant with alkali-containing wastewater with lower alkali concentration and nearly neutral waste liquid and controlling the amount of each component in the mixing process according to the requirement of the alkali liquor alkali concentration in S100. The inventor finds that the recycling of waste liquid and waste alkali can be realized by mixing the supernatant with alkali-containing waste water and waste liquid to prepare alkali liquid and returning the prepared alkali liquid to be used as the alkali liquid, the internal circulation of materials is realized, the discharge amount of final waste liquid is reduced, the use amount of fresh water and fresh alkali in the process of preparing the alkali liquid can be obviously reduced, and the economic and environmental benefits of the process are improved. Further, the concentration of the alkali-containing wastewater may be 0.1 to 10wt%, for example, 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%. Further, the alkali-containing wastewater may be at least one selected from a sodium hydroxide solution, a potassium hydroxide solution, and a calcium hydroxide solution. Furthermore, the alkali-containing wastewater can be obtained by washing a graphite piece cleaning machine. The inventor finds that the graphite piece cleaning machine is used in the production process of polysilicon, the waste liquid obtained by water washing is used as alkali-containing waste water for preparing alkali liquid, and the prepared alkali liquid is returned to S100 for being used as alkali liquid, so that the recycling of the waste liquid obtained by water washing of the graphite piece cleaning machine can be realized, the treatment cost of waste acid obtained by acid washing of the block cleaning machine and/or the silicon core cleaning machine is obviously reduced, and meanwhile, the water consumption and the new alkali amount can be further saved because no new alkali is needed to be prepared, and the economic and environmental benefits of the process are further improved. Further, the mass ratio of the supernatant to the alkali-containing wastewater and the waste liquid can be 1-50:10-50:1, for example, may be 1/10/20/30/40/50:10/20/30/40/50:1. the inventor finds that, as part of solid impurities are contained in the supernatant, if the proportion of the supernatant is higher in preparing alkali liquor, the effect of the obtained prepared alkali liquor in the neutralization treatment for returning the prepared alkali liquor to be used as the alkali liquor is affected; if the proportion of the supernatant liquid is lower in the process of preparing alkali liquor, the use amount of neoalkali can be increased, and the production cost is increased.
According to the method for treating wastewater, disclosed by the embodiment of the invention, the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is subjected to neutralization treatment with the alkali liquor, and then the acid-containing wastewater obtained by water washing of the lump material washing machine and/or the silicon core washing machine is mixed with the neutralized wastewater and the sedimentation agent for sedimentation, so that the amount of the neutralized waste acid and the consumption of the alkali liquor in the neutralization process can be remarkably reduced, the conveying amount of the acid wastewater can be reduced, and the requirement on corrosion resistance of conveying equipment is reduced; the supernatant, the alkali-containing wastewater and the waste liquid are mixed to prepare the alkali liquid, and the prepared alkali liquid is returned to be used as the alkali liquid, so that the recycling of the waste liquid and the waste alkali can be realized, the internal circulation of materials is realized, the discharge amount of the final waste liquid is reduced, the use amount of fresh water and fresh alkali in the process of preparing the alkali liquid can be obviously reduced, and the economic and environmental benefits of the process are improved. Therefore, by adopting the method, the treatment capacity of the pickling wastewater can be reduced by 60%, the water consumption can be saved by 50%, the use amount of the neoalkali can be reduced by 50%, and the method has excellent economic and environmental benefits.
In a further aspect of the invention, the invention proposes a system for implementing the above-mentioned method of treating wastewater, according to an embodiment of the invention, with reference to fig. 2, comprising: neutralization apparatus 100, first settling apparatus 200, filtration apparatus 300, second settling apparatus 400, and mixing apparatus 500.
According to an embodiment of the present invention, the neutralization apparatus 100 has a spent acid inlet 101, an alkali liquor inlet 102, and a neutralized waste water outlet 103, and is adapted to neutralize spent acid from the pickling of the block and/or silicon core washers with alkali liquor to obtain neutralized waste water. Specifically, hydrofluoric acid in waste acid and hydrogen ions in nitric acid are subjected to chemical reaction with hydroxyl ions in alkali liquor to generate water, and the alkali liquor for treating the waste acid needs to be excessive in order to avoid too fast temperature rise of the solution in the neutralization process due to large reaction heat of the neutralization reaction. The particular type of neutralization apparatus is not particularly limited, and those skilled in the art may choose according to actual needs, and may be, for example, a tank or a tank with a stirrer. Further, waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine can be added into alkali liquor for neutralization treatment so as to obtain neutralized waste water. The inventor finds that the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is added into alkali liquor for neutralization treatment, instead of adding the alkali liquor into the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine, the phenomenon that the waste acid boils when the alkali liquor is added and the like, which causes harm to people and environment, can be avoided.
According to one embodiment of the invention, the mass ratio of spent acid to lye may be 1:10-50, for example, can be 1:10/20/30/40/50. The inventor finds that if the mass ratio of the waste acid to the alkali liquor is too large, the content of the waste acid is high, the temperature of the solution rises too fast in the neutralization process, and a fuming phenomenon can occur; if the mass ratio of the waste acid to the alkali liquor is too small, the alkali liquor content is high, so that the waste of the alkali liquor is caused, and the production cost is increased. Further, the concentration of hydrofluoric acid in the waste acid can be 10-30wt%, such as 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, and the concentration of nitric acid can be 30-60wt%, such as 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%. The concentration of the lye may be 20-52.6 wt.%, for example 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 52.6 wt.%. The inventor finds that the condition that the alkali liquor has too high concentration, the moisture content in the solution is low, and the temperature of the solution rises too fast in the neutralization process; the concentration of the alkali liquor is too low, the water quantity used for preparing the alkali liquor is increased, and waste is caused. Further, the alkali liquor is at least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide. When the alkali is neutralized with waste acid obtained by acid washing of a lump material cleaning machine and/or a silicon core cleaning machine, the reaction rate is high, and the neutralization effect is good.
According to an embodiment of the present invention, the first settling device 200 has an acid-containing wastewater inlet 201, a post-neutralization wastewater inlet 202, a settling agent inlet 203, and a post-settling mixture outlet 204, the post-neutralization wastewater inlet 202 being connected to the post-neutralization wastewater outlet 103 and being adapted to mix and settle acid-containing wastewater from water washing of the block and/or silicon core washers with the post-neutralization wastewater, the settling agent. Specifically, fluoride ions in the acid-containing wastewater and the neutralized wastewater can react with a sedimentation agent to generate fluorine-containing solids, and separation of the fluorine-containing solids from liquid can be realized after sedimentation and filtration. The inventor finds that the waste acid obtained by acid washing of the lump material cleaning machine and/or the silicon core cleaning machine is firstly subjected to neutralization treatment with alkali liquor, and then the acid-containing waste water obtained by water washing of the lump material cleaning machine and/or the silicon core cleaning machine is mixed with the neutralized waste water and a sedimentation agent for sedimentation, so that the amount of the neutralized waste acid and the amount of the alkali liquor used in the neutralization process can be remarkably reduced, the conveying amount of the acid waste water can be reduced, and the requirement on corrosion resistance of conveying equipment can be reduced. The specific type of the first settling device is not particularly limited, and may be selected according to actual needs by those skilled in the art, and may be, for example, a settling tank or a settling pond. Further, the concentration of hydrofluoric acid in the acid-containing wastewater may be 0.1 to 0.3wt%, for example, 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, and the concentration of nitric acid may be 0.3 to 0.6wt%, for example, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%. Further, the sedimentation agent may be at least one selected from lime, PAM, PAC, caustic soda. Further, the mass ratio of the acid-containing wastewater to the neutralized wastewater to the sedimentation agent can be 100:1000-2000:1, for example, may be 100:1000/1200/1400/1600/1800/2000:1. the inventor finds that when the consumption of the sedimentation agent is small, the fluoride ions in the acid-containing wastewater and the neutralized wastewater cannot be completely removed, so that the fluoride ion concentration in the waste liquid is still high, and the discharge requirement of the wastewater is not met; when the usage amount of the sedimentation agent is large, the sedimentation agent is wasted, and the production cost is increased.
According to an embodiment of the present invention, the filtering device 300 has a post-sedimentation mixture inlet 301, a waste residue outlet 302 and a waste liquid outlet 303, and the post-sedimentation mixture inlet 301 is connected to the post-sedimentation mixture outlet 204 and is adapted to filter the liquid-solid mixture obtained after sedimentation in the first sedimentation device 200, to obtain waste residues and waste liquids. The specific type of the filtration device is not particularly limited, and may be selected according to actual needs by those skilled in the art, and may be, for example, a liquid-solid separation tank or a liquid-solid separation tank.
According to an embodiment of the invention, the second settling device 400 has a spent caustic inlet 401, a supernatant outlet 402 and a settled slag outlet 403 and is adapted to subject spent caustic to a settling treatment in order to obtain a supernatant and a settled slag. Specifically, the waste alkali contains a small amount of silicon powder or other solid impurities, and after sedimentation and liquid-solid separation, the solid impurities in the waste alkali can be removed in the form of sedimentation slag to obtain supernatant. The specific type of the second settling device is not particularly limited, and may be selected according to actual needs by those skilled in the art, and may be, for example, a settling tank or a settling pond. Further, the concentration of the supernatant may be 35 to 45wt%, for example, 35wt%, 37wt%, 39wt%, 41wt%, 43wt%, 45wt%. Further, the supernatant may be at least one selected from a sodium hydroxide solution, a potassium hydroxide solution, and a calcium hydroxide solution. Further, the waste alkali can be obtained by alkali washing of a graphite piece cleaning machine. The inventor finds that the graphite piece cleaning machine is used in the production process of polysilicon, the waste liquid obtained by alkaline cleaning is used as waste alkali for sedimentation, the obtained supernatant is used for subsequent alkali preparation, and the obtained alkali preparation is returned to the neutralization device to be used as alkali, so that the waste liquid obtained by alkaline cleaning of the graphite piece cleaning machine can be recycled, the treatment cost of waste acid obtained by acid cleaning of the block cleaning machine and/or the silicon core cleaning machine is obviously reduced, and meanwhile, the water consumption and the new alkali amount can be obviously saved because no new alkali is needed to be prepared, and the economic and environmental benefits are obvious.
According to an embodiment of the invention, the mixing device 500 has a supernatant inlet 501, an alkali-containing wastewater inlet 502, a waste liquid inlet 503 and a configuration lye outlet 504, the supernatant inlet 501 being connected to the supernatant outlet 402, the waste liquid inlet 503 being connected to the waste liquid outlet 303, the configuration lye outlet 504 being connected to the lye inlet 102 and being adapted to mix the supernatant with the alkali-containing wastewater, the waste liquid, so as to obtain a configuration lye, and to return the configuration lye to the neutralization device 100 for use as lye. Specifically, the alkali concentration in the supernatant is higher, and alkali liquor meeting the requirement of the neutralization device can be obtained by mixing the supernatant with alkali-containing wastewater with lower alkali concentration and nearly neutral waste liquor and controlling the amount of each component in the mixing process according to the requirement of the neutralization device on the alkali concentration of the alkali liquor. The inventor finds that the recycling of waste liquid and waste alkali can be realized by mixing the supernatant with alkali-containing waste water and waste liquid to prepare alkali liquid and returning the prepared alkali liquid to be used as the alkali liquid, the internal circulation of materials is realized, the discharge amount of final waste liquid is reduced, the use amount of fresh water and fresh alkali in the process of preparing the alkali liquid can be obviously reduced, and the economic and environmental benefits of the process are improved. The specific type of the mixing device is not particularly limited, and may be selected according to actual needs by those skilled in the art, and may be, for example, a tank or a tank with a stirrer.
According to one embodiment of the invention, the concentration of the alkali-containing wastewater may be 0.1-10wt%, for example, may be 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%. Further, the alkali-containing wastewater may be at least one selected from a sodium hydroxide solution, a potassium hydroxide solution, and a calcium hydroxide solution. Furthermore, the alkali-containing wastewater can be obtained by washing a graphite piece cleaning machine. The inventor finds that the graphite piece cleaning machine is used in the production process of polysilicon, the waste liquid obtained by water washing is used as alkali-containing waste water for preparing alkali liquid, and the prepared alkali liquid is returned to the neutralization device for use as alkali liquid, so that the recycling of the waste liquid obtained by water washing of the graphite piece cleaning machine can be realized, the treatment cost of waste acid obtained by acid washing of the block cleaning machine and/or the silicon core cleaning machine is obviously reduced, and meanwhile, the water consumption and the new alkali amount can be further saved because no new alkali is needed to be prepared, and the economic and environmental benefits of the process are further improved. Further, the mass ratio of the supernatant to the alkali-containing wastewater and the waste liquid can be 1-50:10-50:1, for example, may be 1/10/20/30/40/50:10/20/30/40/50:1. the inventor finds that, as part of solid impurities are contained in the supernatant, if the proportion of the supernatant is higher in preparing alkali liquor, the effect of the obtained prepared alkali liquor in the neutralization treatment for returning the prepared alkali liquor to be used as the alkali liquor is affected; if the proportion of the supernatant liquid is lower in the process of preparing alkali liquor, the use amount of neoalkali can be increased, and the production cost is increased.
According to the system for treating wastewater, disclosed by the embodiment of the invention, the waste acid obtained by acid washing of the lump material washing machine and/or the silicon core washing machine is subjected to neutralization treatment with the alkali liquor, and then the acid-containing wastewater obtained by water washing of the lump material washing machine and/or the silicon core washing machine is mixed with the neutralized wastewater and the sedimentation agent for sedimentation, so that the amount of the neutralized waste acid and the consumption of the alkali liquor in the neutralization process can be remarkably reduced, the conveying amount of the acid wastewater can be reduced, and the requirement on corrosion resistance of conveying equipment is reduced; the supernatant, the alkali-containing wastewater and the waste liquid are mixed to prepare the alkali liquid, and the prepared alkali liquid is returned to be used as the alkali liquid, so that the recycling of the waste liquid and the waste alkali can be realized, the internal circulation of materials is realized, the discharge amount of the final waste liquid is reduced, the use amount of fresh water and fresh alkali in the process of preparing the alkali liquid can be obviously reduced, and the economic and environmental benefits of the process are improved. Therefore, by adopting the system, the treatment capacity of the pickling wastewater can be reduced by 60%, the water consumption can be saved by 50%, the use amount of the neoalkali can be reduced by 50%, and the system has excellent economic and environmental benefits.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
Example 1
Adding waste acid obtained by acid washing of a lump material cleaning machine and/or a silicon core cleaning machine into alkali liquor for neutralization treatment, wherein the mass ratio of the waste acid to the alkali liquor is 1:100, the concentration of hydrofluoric acid in the waste acid is 10wt% and the concentration of nitric acid is 30wt%. The alkali liquor is sodium hydroxide solution with the concentration of 20 weight percent, and the neutralized wastewater is obtained; mixing acid-containing wastewater obtained by washing a lump material washing machine and/or a silicon core washing machine with neutralized wastewater and a settling agent lime for settlement, wherein the concentration of hydrofluoric acid in the acid-containing wastewater is 0.3wt%, the concentration of nitric acid is 0.3wt%, and the mass ratio of the acid-containing wastewater to the neutralized wastewater and the settling agent is 100:1000:1, filtering to obtain waste residue and waste liquid; performing sedimentation treatment on waste alkali obtained by alkali washing of a graphite piece cleaning machine to obtain supernatant sodium hydroxide solution with the concentration of 35wt% and sedimentation slag; washing the supernatant with 0.1wt% alkali-containing wastewater sodium hydroxide solution and waste liquid obtained by washing a graphite piece cleaning machine according to the mass ratio of 1:50:1, mixing to obtain a prepared alkali liquor, and returning the prepared alkali liquor to be used as alkali liquor. The whole process can reduce the acid wastewater treatment amount by 60%, save the water consumption by 50% and reduce the new alkali amount by 50%, and has good economic and environmental benefits.
Example 2
Adding waste acid obtained by acid washing of a lump material cleaning machine and/or a silicon core cleaning machine into alkali liquor for neutralization treatment, wherein the mass ratio of the waste acid to the alkali liquor is 1:30, the concentration of hydrofluoric acid in the waste acid is 20wt% and the concentration of nitric acid is 50wt%. The alkali liquor is potassium hydroxide solution with the concentration of 35 weight percent, and the neutralized wastewater is obtained; mixing acid-containing wastewater obtained by washing a lump material washing machine and/or a silicon core washing machine with neutralized wastewater and a sedimentation agent PAM for sedimentation, wherein the concentration of hydrofluoric acid in the acid-containing wastewater is 0.1wt%, the concentration of nitric acid is 0.5wt%, and the mass ratio of the acid-containing wastewater to the neutralized wastewater and the sedimentation agent is 100:1500:1, filtering to obtain waste residue and waste liquid; performing sedimentation treatment on waste alkali obtained by alkali washing of a graphite piece cleaning machine to obtain supernatant potassium hydroxide solution with the concentration of 40wt% and sedimentation slag; washing the supernatant with a graphite piece washing machine to obtain an alkali-containing wastewater potassium hydroxide solution with the concentration of 0.5wt% and a waste liquid according to the mass ratio of 25:30:1, mixing to obtain a prepared alkali liquor, and returning the prepared alkali liquor to be used as alkali liquor. The whole process can reduce the acid wastewater treatment capacity by 50%, save water consumption by 45% and reduce new alkali content by 45%, and has good economic and environmental benefits.
Example 3
Adding waste acid obtained by acid washing of a lump material cleaning machine and/or a silicon core cleaning machine into alkali liquor for neutralization treatment, wherein the mass ratio of the waste acid to the alkali liquor is 1:50, the concentration of hydrofluoric acid in the waste acid is 30wt% and the concentration of nitric acid is 60wt%. The alkali liquor is calcium hydroxide solution with the concentration of 52.6 weight percent, and the neutralized wastewater is obtained; mixing acid-containing wastewater obtained by washing a lump material washing machine and/or a silicon core washing machine with neutralized wastewater and a sedimentation agent PAC for sedimentation, wherein the concentration of hydrofluoric acid in the acid-containing wastewater is 0.15wt%, the concentration of nitric acid is 0.6wt%, and the mass ratio of the acid-containing wastewater to the neutralized wastewater and the sedimentation agent is 100:2000:1, filtering to obtain waste residue and waste liquid; carrying out sedimentation treatment on waste alkali obtained by alkali washing of a graphite piece cleaning machine to obtain supernatant calcium hydroxide solution with the concentration of 45wt% and sedimentation slag; washing the supernatant with a graphite piece cleaning machine to obtain an alkali-containing wastewater calcium hydroxide solution with the concentration of 0.1wt% and a waste liquid according to the mass ratio of 50:10:1. mixing to obtain a prepared alkali liquor, and returning the prepared alkali liquor to be used as alkali liquor. The whole process can reduce the acid wastewater treatment capacity by 40%, save water consumption by 40% and reduce the new alkali content by 40%, and has good economic and environmental benefits.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (8)
1. A method of treating wastewater, comprising:
(1) Neutralizing waste acid obtained by acid washing of a lump material washing machine and/or a silicon core washing machine with alkali liquor so as to obtain neutralized waste water;
(2) Mixing and settling acid-containing wastewater obtained by washing the lump material washing machine and/or the silicon core washing machine with the neutralized wastewater and a settling agent, and filtering to obtain waste residues and waste liquid;
(3) Settling the waste alkali to obtain supernatant and settled slag;
(4) Mixing the supernatant with alkali-containing wastewater and the waste liquid so as to obtain a prepared alkali liquor, and returning the prepared alkali liquor to the step (1) to be used as the alkali liquor;
in the step (1), the mass ratio of the waste acid to the alkali liquor is 1:10-50;
in the step (2), the sedimentation agent is at least one selected from lime, PAM, PAC and caustic soda;
in the step (3), the waste alkali is obtained by alkali washing of a graphite piece cleaning machine;
in the step (4), the alkali-containing wastewater is obtained by washing a graphite piece cleaning machine;
in the step (4), the mass ratio of the supernatant to the alkali-containing wastewater to the waste liquid is 1-50:10-50:1.
2. the method according to claim 1, wherein in step (1), the waste acid obtained by pickling the block washer and/or the silicon core washer is added to the alkali solution to perform the neutralization treatment so as to obtain the neutralized waste water.
3. The method according to claim 1 or 2, wherein in step (1), the concentration of hydrofluoric acid in the spent acid is 10 to 30wt% and the concentration of nitric acid is 30 to 60wt%;
optionally, in step (1), the lye is at a concentration of 20 to 52.6 wt.%;
optionally, in step (1), the alkali liquor is at least one selected from sodium hydroxide, potassium hydroxide and calcium hydroxide.
4. A method according to claim 3, wherein in step (2), the concentration of hydrofluoric acid in the acid-containing wastewater is 0.1 to 0.3wt% and the concentration of nitric acid is 0.3 to 0.6wt%;
optionally, in the step (2), the mass ratio of the acid-containing wastewater to the neutralized wastewater to the sedimentation agent is 100:1000-2000:1.
5. the method of claim 1, wherein the step of determining the position of the substrate comprises,
in step (3), the concentration of the supernatant is 35-45wt%;
optionally, the supernatant is at least one selected from sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution.
6. The method according to claim 1 or 2, wherein in step (4), the concentration of the alkali-containing wastewater is 0.1 to 10wt%;
optionally, in step (4), the alkali-containing wastewater is at least one selected from sodium hydroxide solution, potassium hydroxide solution and calcium hydroxide solution.
7. A system for carrying out the method of treating wastewater of any one of claims 1-6, comprising:
the neutralization device is provided with a waste acid inlet, an alkali liquor inlet and a neutralized waste water outlet;
the first sedimentation device is provided with an acid-containing wastewater inlet, a neutralized wastewater inlet, a sedimentation agent inlet and a settled mixture outlet, and the neutralized wastewater inlet is connected with the neutralized wastewater outlet;
the filtering device is provided with a mixture inlet after sedimentation, a waste residue outlet and a waste liquid outlet, and the mixture inlet after sedimentation is connected with the mixture outlet after sedimentation;
the second sedimentation device is provided with a waste alkali inlet, a supernatant outlet and a sediments outlet;
the mixing device is provided with a supernatant inlet, an alkali-containing wastewater inlet, a waste liquid inlet and an alkali liquor preparing outlet, wherein the supernatant inlet is connected with the supernatant outlet, the waste liquid inlet is connected with the waste liquid outlet, and the alkali liquor preparing outlet is connected with the alkali liquor inlet;
the filtering device is a liquid-solid separation tank or a liquid-solid separation tank;
the mixing device is a storage tank or a storage tank with a stirrer.
8. The system of claim 7, wherein the neutralization device is a tank or reservoir with a stirrer;
optionally, the first settling device and the second settling device are each independently a settling tank or a settling pond.
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