CN103896425A - Polycrystalline silicon wastewater treatment device and method - Google Patents
Polycrystalline silicon wastewater treatment device and method Download PDFInfo
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- CN103896425A CN103896425A CN201210588234.3A CN201210588234A CN103896425A CN 103896425 A CN103896425 A CN 103896425A CN 201210588234 A CN201210588234 A CN 201210588234A CN 103896425 A CN103896425 A CN 103896425A
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 38
- 238000004065 wastewater treatment Methods 0.000 title claims abstract description 23
- 238000000034 method Methods 0.000 title abstract description 30
- 239000007788 liquid Substances 0.000 claims abstract description 92
- 239000012528 membrane Substances 0.000 claims abstract description 55
- 238000000926 separation method Methods 0.000 claims abstract description 54
- 239000000919 ceramic Substances 0.000 claims abstract description 49
- 239000012530 fluid Substances 0.000 claims abstract description 40
- 239000002699 waste material Substances 0.000 claims abstract description 31
- 238000011282 treatment Methods 0.000 claims abstract description 21
- 238000003860 storage Methods 0.000 claims abstract description 6
- 239000002202 Polyethylene glycol Substances 0.000 claims description 42
- 229920001223 polyethylene glycol Polymers 0.000 claims description 42
- 239000007787 solid Substances 0.000 claims description 31
- 229920005591 polysilicon Polymers 0.000 claims description 26
- 239000002245 particle Substances 0.000 claims description 25
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- 229910001868 water Inorganic materials 0.000 claims description 21
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- 238000004064 recycling Methods 0.000 claims description 12
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000005266 casting Methods 0.000 claims description 6
- 239000011780 sodium chloride Substances 0.000 claims description 6
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 5
- 239000001110 calcium chloride Substances 0.000 claims description 5
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000011148 porous material Substances 0.000 claims description 4
- 238000004140 cleaning Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 239000008247 solid mixture Substances 0.000 claims description 3
- 239000004408 titanium dioxide Substances 0.000 claims description 3
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 claims 1
- 230000008901 benefit Effects 0.000 abstract description 10
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- 239000012466 permeate Substances 0.000 abstract description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 52
- 229910010271 silicon carbide Inorganic materials 0.000 description 49
- 238000011084 recovery Methods 0.000 description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 12
- 238000005516 engineering process Methods 0.000 description 12
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 10
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- 235000012431 wafers Nutrition 0.000 description 2
- RZVAJINKPMORJF-UHFFFAOYSA-N Acetaminophen Chemical compound CC(=O)NC1=CC=C(O)C=C1 RZVAJINKPMORJF-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- 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
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W10/00—Technologies for wastewater treatment
- Y02W10/30—Wastewater or sewage treatment systems using renewable energies
- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
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- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention discloses a polycrystalline silicon wastewater treatment device and a method. The device comprises a ceramic membrane system, wherein the ceramic membrane system comprises a material liquid tank, a supply pump, a circulation pump, a ceramic membrane, a permeate tank and a plurality of connecting pipelines, wherein pressure regulation valves and/or instruments and meters are arranged on the connecting pipelines; a liquid separator is further connected through the pipelines; the liquid separator comprises a separation chamber as well as a fluid storage tank and a flow supply pump connected with the separation chamber; the flow supply pump is arranged between the separation chamber and the fluid storage tank. By adopting the method, the original pollutant treatment is converted into industrial resources which can be recycled, so that the waste is turned into wealth, and very high economic values and environment benefits are achieved.
Description
Technical Field
The invention relates to a wastewater treatment method, in particular to a polysilicon wastewater treatment method and a polysilicon wastewater treatment device, and belongs to the field of wastewater recycling.
Background
The silicon is used as an important photoelectric material and a semiconductor material, the strategic resource position is increasingly obvious, and the global demand is continuously increased. In the photoelectric and semiconductor industries, a single silicon body needs to be cut into silicon wafers meeting requirements, at present, a multi-wire cutting technology is mainly adopted for polycrystalline silicon, about 50% of silicon materials are mixed into cutting fluid consisting of polyethylene glycol (PEG) cutting fluid and silicon carbide powder (SiC) grinding materials in the cutting process, so that the composition, the particle size and the hardness of micro powder in the cutting fluid do not meet the standard, the cutting performance is reduced, the micro powder cannot be recycled, old cutting fluid needs to be continuously discharged in the cutting process, new cutting fluid needs to be continuously supplemented, and a large amount of cutting waste liquid is generated.
The cutting waste liquid is black viscous suspension, and the main component and content are 40-50% of polyethylene glycol (PEG); 23 to 33 percent of silicon carbide (SiC), 20 to 24 percent of silicon (Si) and 2.5 to 3.0 percent of scrap iron (Fe). The PEG is prepared by extracting PEG from petroleum and polymerizing, has stable molecular structure, is not easy to decompose, is very easy to dissolve in water, has low biological oxygen consumption, is not easy to degrade in nature, has COD (chemical oxygen demand) value greatly exceeding the wastewater discharge standard, and causes huge pollution if the PEG flows into the natural environment without special treatment. SiC and Si are important industrial raw materials and belong to non-renewable resources. Huge energy is consumed in the process of producing the SiC raw material, and the state limits the new industrial project. The Si is high-purity silicon powder cut and ground, and if the silicon powder is directly discharged, environmental pollution and waste of silicon materials are caused.
At present, two ideas exist for the treatment of the wastewater: one is to discharge after the treatment reaches the standard. Common methods comprise a microbiological method, an advanced oxidation method and the like, and for the important PEG-containing wastewater, the microbiological method has the disadvantages of complex process, low treatment efficiency and poor treatment effect, and can hardly reach the standard; the advanced oxidation method has good treatment effect, but has high operation cost and complex process control; other common sewage treatment methods are difficult to be applied; the other idea is to recycle the waste liquid by stages, because PEG, SiC and Si in the waste liquid are important industrial raw materials, wherein the market price of polyethylene glycol (PEG) is 12 yuan per kilogram, the market price of SiC is 24 yuan per kilogram, and the market price of Si is 140 yuan per kilogram. Therefore, the classified recovery and utilization of the silicon cutting waste liquid have important significance for saving resources, protecting the environment and improving economic benefits, relatively mature treatment and recovery technologies exist abroad, the technology in the aspect of China is immature, and most of the technology is in the research stage.
The domestic existing treatment and recovery technology comprises the following steps: a photovoltaic wastewater zero discharge process (CN 102557291A), the system flow is too long, the process is complex, the investment is too large, and the practical application of the project is difficult to realize; a method for treating wastewater containing polyethylene glycol (CN 1023722388A) adopts flocculation precipitation and Fendon oxidation technologies, the treated wastewater needs to enter a wastewater treatment plant for treatment, the use cost is high, and the method is not suitable for the treatment of polysilicon wastewater; the patent method (CN 101244823A) for recovering silicon carbide from the by-products of silicon wafer cutting processing adopts centrifugal solid-liquid separation, and only recovers silicon carbide, polyethylene glycol and silicon with higher recovery value in waste liquid;
the main problems of the existing recovery technology are that: the solid-liquid separation effect is not good, and multi-stage separation is often needed, such as: centrifugal separation, inclined plate precipitation, filtration, filter pressing and the like, wherein the separated PEG liquid contains part of light impurities and can be recycled only by further purification; ② the SiC and Si separation process is complex and the effect is not good enough, needs to use a plurality of chemical agents or pass through a plurality of physical processes, and lacks a simple and effective separation method.
Disclosure of Invention
The invention aims to solve the technical problem of high-efficiency treatment and recycling technology, and can thoroughly solve the problem of poor solid-liquid separation effect, so that the invention provides a device and a method for treating polycrystalline silicon wastewater.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a polysilicon wastewater treatment device comprises: a ceramic membrane system;
the ceramic membrane system comprises a feed liquid tank, a feed pump, a circulating pump, a ceramic membrane, a permeation liquid tank and a plurality of connecting pipelines, wherein a pressure regulating valve and/or an instrument are/is further arranged on each connecting pipeline.
Further, preferably, the ceramic membrane has a tubular multi-stage bent hollow structure, and the membrane pores are smaller than 1 μm.
Further, it is preferable that the ceramic membrane is made of titanium dioxide and zirconia frit.
Further, it is preferable that a liquid separator is further connected through the pipe, including:
the device comprises a separation cavity, a fluid storage tank connected with the separation cavity, and a flow supply pump, wherein the flow supply pump is arranged between the separation cavity and the fluid storage tank.
Further, it is preferred that the liquid inlet of the separation chamber opens at a position below the separation chamber.
Further, it is preferable that the liquid is pure water or calcium chloride or a sodium chloride solution.
A polysilicon wastewater treatment method comprises the following steps:
(1) pressurizing the polycrystalline silicon waste liquid, then feeding the polycrystalline silicon waste liquid into a ceramic membrane system, carrying out solid-liquid separation under the pressure of 0.20MPa-0.55MPa, separating out polyethylene glycol liquid, storing the polyethylene glycol liquid for recycling production, and feeding the solid-liquid mixture subjected to treatment into the step (2);
(2) washing a solid-liquid mixture separated by the ceramic membrane system with pure water to obtain a product comprising: adding the solid mixture of SiC, Si, Fe and impurities into hydrochloric acid, stirring and cleaning to separate out mixed particles of solid SiC, solid Si and impurities;
(3) adding the solid SiC and Si mixed particles into a fluid separator, controlling the flow rate of the fluid separator to layer SiC and Si, respectively collecting the layered SiC and Si, and not separating part of the solid SiC, solid Si and impurities in the mixed state.
Further, it is preferable that, after the step (3), the method further comprises: casting and purifying the separated Si to obtain solar grade polysilicon; and/or; drying the separated SiC, carrying out micro powder grading separation, and selecting and recycling according to the particle size.
Further, it is preferable that the hydrochloric acid has a temperature of 30 to 45 ℃ and a concentration of 10 to 30% in the step (2), and the stirring is performed for 30 to 90 minutes in the step (2).
Further, it is preferable that, in the step (3), the flow rate of the fluid separator is in the range of 40m/h to 60 m/h.
After the scheme is adopted, the invention has the following advantages:
firstly, the original waste liquid is directly pressurized and separated without any treatment, no chemicals are added, the purity of the separated PEG reaches 99.7 percent, the process is simple and reliable, the PEG separation and purification process can be completed once, and the PEG recovery rate reaches 92 percent;
the innovative SiC and Si fluid separator technology is simple to operate and has good separation effect, the Si recovery rate can reach 85% at most, and the SiC recovery rate is over 90%. Since the SiC and Si mixture of the separation interface can be continuously separated in the next separation, the separation rate is theoretically higher the more separation times.
The invention changes waste liquid to be treated into valuable, realizes zero discharge of pollutants and has high economic benefit.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The present invention will be described in detail below with reference to the accompanying drawings so that the above advantages of the present invention will be more apparent. Wherein,
FIG. 1 is a schematic flow diagram of a polysilicon wastewater treatment process according to the present invention;
FIG. 2 is a schematic structural view of a ceramic membrane system of the polysilicon wastewater treatment apparatus of the present invention;
FIG. 3 is a schematic view showing the construction of a fluid separator of the polysilicon wastewater treatment apparatus according to the present invention.
Detailed Description
The following detailed description of the embodiments of the present invention will be provided with reference to the drawings and examples, so that how to apply the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, the embodiments and the features of the embodiments of the present invention may be combined with each other, and the technical solutions formed are within the scope of the present invention.
Additionally, the steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions and, although a logical order is illustrated in the flow charts, in some cases, the steps illustrated or described may be performed in an order different than here.
As shown in figure 1, the method for treating the polycrystalline silicon wastewater comprises the following steps:
(1) pressurizing the polycrystalline silicon waste liquid, then feeding the polycrystalline silicon waste liquid into a ceramic membrane system, carrying out solid-liquid separation under the pressure of 0.20MPa-0.55MPa, separating out polyethylene glycol liquid, storing the polyethylene glycol liquid for recycling production, and feeding the solid-liquid mixture subjected to treatment into the step (2);
(2) washing a solid-liquid mixture separated by the ceramic membrane system with pure water to obtain a product comprising: adding the solid mixture of SiC, Si, Fe and impurities into hydrochloric acid, stirring and cleaning to separate out mixed particles of solid SiC, solid Si and impurities;
(3) adding the solid SiC and Si mixed particles into a fluid separator, controlling the flow rate of the fluid separator to layer SiC and Si, respectively collecting the layered SiC and Si, and not separating part of the solid SiC, solid Si and impurities in the mixed state.
Further, it is preferable that, after the step (3), the method further comprises: casting and purifying the separated Si to obtain solar grade polysilicon; and/or; drying the separated SiC, carrying out micro powder grading separation, and selecting and recycling according to the particle size.
Further, it is preferable that the hydrochloric acid has a temperature of 30 to 45 ℃ and a concentration of 10 to 30% in the step (2), and the stirring is performed for 30 to 90 minutes in the step (2).
Further, it is preferable that, in the step (3), the flow rate of the fluid separator is in the range of 40m/h to 60 m/h.
In one embodiment, the method comprises the following steps:
the first step is as follows: pressurizing the waste liquid, then introducing the waste liquid into a ceramic membrane system, and performing solid-liquid separation under the pressure of 0.20-0.55 MPa, wherein the ceramic membrane system is a microporous filtration technology, the effective filtration pore diameter is less than 1 mu m, PEG liquid in the waste liquid passes through micropores under the pressure driving, solid particles in the waste liquid cannot pass through the micropores, the separation process is performed at normal temperature without adding any chemical agent, no phase change occurs in the whole process, the purity of the separated PEG liquid reaches 99.7%, the separated PEG liquid completely meets the cutting production requirement, the PEG liquid can be directly stored for reuse production, and the PEG recovery rate is more than 92%;
the second step is that: washing concentrated slurry separated by a ceramic membrane system with pure water to obtain solid of SiC, Si, Fe and a very small amount of impurities, adding the solid into hydrochloric acid with the temperature of 30-45 ℃ and the concentration of 10-30%, stirring and washing for 30-90 minutes, reacting Fe and a small amount of impurities with the hydrochloric acid, dissolving the Fe and the small amount of impurities in the hydrochloric acid to remove the impurities, washing with the pure water after acid washing, and obtaining solid particles of SiC and Si;
the third step: adding the mixed particles obtained in the previous step into a fluid separator, controlling the flow rate of the fluid separator to be 40m/h-60 m/h, wherein the liquid used in the fluid separator is pure water or calcium chloride and sodium chloride solution, and because SiC and Si have different densities (SiC 3.2g/cm3 and Si 2.4g/cm 3), when the liquid in the fluid separator flows from bottom to top at a certain flow rate, the whole mixed particles are in a suspension state, low-density Si is suspended in an upper layer, high-density SiC is suspended in a lower layer, the flow of the fluid is stopped, the suspended mixed particles are separated and settled down in layers, the separation can be completed, SiC and Si are respectively collected, a small amount of mixture of SiC and Si is arranged in the middle of the separation layer of the fluid separator, the mixture can be collected additionally, and the mixture is separated again when the mixture is separated next time, so that the purity of the collected SiC and Si can be ensured, after multiple separation, the separation rate is improved;
the fourth step: the collected Si is cast and purified to obtain solar grade polysilicon, and the highest Si recovery rate can reach 85%; the fifth step: drying SiC, then carrying out micro powder grading separation, selecting and recycling according to the particle size, and the recovery rate is more than 90%.
As shown in fig. 2 and 3, the present embodiment also discloses a polysilicon wastewater treatment apparatus, wherein the invention of the present embodiment mainly consists in a ceramic membrane system and a fluid separator, and thus, the structure thereof is mainly illustrated in fig. 2 and 3, and other components can adopt existing ones, which will not be described in detail herein, and are known to those skilled in the art.
As shown in fig. 2, the ceramic membrane system includes a feed liquid tank 11, a feed pump 12, a circulation pump 13, a ceramic membrane 14, a permeate liquid tank 15, and a plurality of connection pipes, wherein pressure regulating valves and/or instruments are further disposed on the connection pipes.
Further, preferably, the ceramic membrane has a tubular multi-stage bent hollow structure, and the membrane pores are smaller than 1 μm.
Further, it is preferable that the ceramic membrane is made of titanium dioxide and zirconia frit.
Further, it is preferable that a liquid separator is further connected through the pipe, including:
a separation chamber 31 and a tank 33 connected thereto, a flow feed pump 32 being provided between the separation chamber and the tank.
Further, it is preferred that the liquid inlet of the separation chamber opens at a lower position of the separation chamber, where the low density fraction 34 is above and the high density fraction 35 is below, where there will be an incompletely separated mixture at the lowest.
Further, it is preferable that the liquid is pure water or calcium chloride or sodium chloride solution, more specifically, in the fluid separator, the liquid enters the separator from bottom to top, the mixture to be separated is in a suspension state by adjusting the flow rate of the liquid in the fluid separator, and the liquid used in the fluid separator is pure water or calcium chloride or sodium chloride solution with a certain concentration.
The present invention will be described in detail below with reference to the accompanying drawings.
Example 1, one of the treatments, was carried out according to the following steps:
the first step is as follows: supplying the collected waste liquid to a ceramic membrane system through a feed pump, starting a circulating pump, controlling the inlet pressure of the ceramic membrane system to be 0.55MPa, the outlet pressure of the ceramic membrane system to be 0.40MPa, the filter aperture of a filling membrane of the ceramic membrane system to be 0.14 mu m by adjusting a rear valve of the feed pump, a rear valve of the circulating pump and a return valve of concentrated liquid, allowing PEG liquid in the waste liquid to pass through micropores of the ceramic membrane under the driving of pressure, preventing solid particles in the waste liquid from passing through, collecting and storing the penetrated PEG liquid, and collecting concentrated slurry after no PEG liquid is penetrated out;
the second step is that: washing concentrated slurry separated by a ceramic membrane system with pure water to obtain solid of SiC, Si, Fe and a very small amount of impurities, adding the solid into hydrochloric acid with the temperature of 30 ℃ and the concentration of 10%, stirring and washing for 90 minutes to remove Fe and a small amount of impurities, washing with pure water after acid washing, and obtaining solid particles of SiC and Si;
the third step: adding the mixed particulate matters obtained in the previous step into a fluid separator, and controlling the flow speed of the fluid separator to be 60 m/h, wherein the liquid used in the fluid separator is pure water, when the mixed particulate matters are all in a suspension state, rapidly stopping water inlet of the fluid separator, rapidly settling the mixture, and respectively collecting Si on the upper layer and SiC on the lower layer;
the fourth step: casting and purifying the collected Si to obtain solar grade polysilicon;
the fifth step: drying SiC, carrying out micro powder grading separation, and selecting and recycling according to the particle size;
the second treatment method of example 2 was carried out by the following steps:
the first step is as follows: supplying the collected waste liquid to a ceramic membrane system through a feed pump, starting a circulating pump, controlling the inlet pressure of the ceramic membrane system to be 0.35MPa, the outlet pressure of the ceramic membrane system to be 0.2MPa, the filtering aperture of a filling membrane of the ceramic membrane system to be 0.3 mu m by adjusting a rear valve of the feed pump, a rear valve of the circulating pump and a reflux valve of concentrated liquid, wherein PEG liquid in the waste liquid passes through micropores of the ceramic membrane under the driving of pressure, solid particles in the waste liquid cannot pass through the micropores of the ceramic membrane, collecting and storing the penetrated PEG liquid, and collecting concentrated slurry after no PEG liquid is penetrated out;
the second step is that: washing concentrated slurry separated by a ceramic membrane system with pure water to obtain solid of SiC, Si, Fe and a very small amount of impurities, adding the solid into hydrochloric acid with the temperature of 40 ℃ and the concentration of 20%, stirring and washing for 60 minutes to remove Fe and a small amount of impurities, washing with pure water after acid washing, and obtaining solid particles of SiC and Si;
the third step: adding the mixed particulate matters obtained in the previous step into a fluid separator, and controlling the flow rate of the fluid separator to be 50 m/h, wherein the liquid used in the fluid separator is a 20% sodium chloride solution, when the mixed particulate matters are all in a suspension state, quickly stopping water inlet of the fluid separator, quickly settling the mixture, and respectively collecting the Si on the upper layer and the SiC on the lower layer;
the fourth step: casting and purifying the collected Si to obtain solar grade polysilicon;
the fifth step: drying SiC, carrying out micro powder grading separation, and selecting and recycling according to the particle size;
example 3, the third treatment method, was carried out as follows:
the first step is as follows: supplying the collected waste liquid to a ceramic membrane system through a feed pump, starting a circulating pump, controlling the inlet pressure of the ceramic membrane system to be 0.25MPa, the outlet pressure of the ceramic membrane system to be 0.1MPa, the filter aperture of a filling membrane of the ceramic membrane system to be 0.8 mu m by adjusting a rear valve of the feed pump, a rear valve of the circulating pump and a reflux valve of concentrated liquid, wherein PEG liquid in the waste liquid passes through micropores of the ceramic membrane under the driving of pressure, solid particles in the waste liquid cannot pass through the micropores of the ceramic membrane, collecting and storing the penetrated PEG liquid, and collecting concentrated slurry after no PEG liquid is penetrated out;
the second step is that: washing concentrated slurry separated by a ceramic membrane system with pure water to obtain solid of SiC, Si, Fe and a very small amount of impurities, adding the solid into hydrochloric acid with the temperature of 45 ℃ and the concentration of 30%, stirring and washing for 30 minutes to remove Fe and a small amount of impurities, washing with pure water after acid washing, and obtaining solid particles of SiC and Si;
the third step: adding the mixed particulate matters obtained in the previous step into a fluid separator, and controlling the flow rate of the fluid separator to be 40m/h, wherein the liquid used in the fluid separator is a 30% calcium chloride solution, when the mixed particulate matters are all in a suspension state, quickly stopping water inlet of the fluid separator, quickly settling the mixture, and respectively collecting the Si on the upper layer and the SiC on the lower layer;
the fourth step: casting and purifying the collected Si to obtain solar grade polysilicon;
the fifth step: drying SiC, carrying out micro powder grading separation, and selecting and recycling according to the particle size;
the invention has the following advantages:
the ceramic membrane solid-liquid separation technology has the advantages that the original waste liquid is directly subjected to pressure separation without any treatment, no chemicals are added, the purity of the separated PEG reaches 99.7%, the process is simple and reliable, the PEG separation and purification process can be completed at one time, and the PEG recovery rate reaches 92%;
the innovative SiC and Si fluid separator technology is simple to operate and has good separation effect, the Si recovery rate can reach 85% at most, and the SiC recovery rate is over 90%. Since the SiC and Si mixture of the separation interface can be continuously separated in the next separation, the separation rate is theoretically higher the more separation times.
The waste liquid to be treated is changed into valuable, so that zero emission of pollutants is realized, and the method has high economic benefits:
| market price (Yuan/kilogram) | Recycle price (Yuan/kg) | |
| Polyethylene glycol (PEG) | 12 | 12 |
| Silicon carbide (SiC) | 24 | 18 |
| Silicon (Si) | 140 | 140 |
It should be noted that for simplicity of description, the above method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the present application is not limited by the order of acts described, as some steps may occur in other orders or concurrently depending on the application. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required in this application.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A polysilicon wastewater treatment device is characterized by comprising: a ceramic membrane system;
the ceramic membrane system comprises a feed liquid tank, a feed pump, a circulating pump, a ceramic membrane, a permeation liquid tank and a plurality of connecting pipelines, wherein a pressure regulating valve and/or an instrument are/is further arranged on each connecting pipeline.
2. The polysilicon wastewater treatment device according to claim 1, wherein the ceramic membrane has a tubular multi-section bent hollow structure, and the membrane pores are smaller than 1 μm.
3. The polysilicon wastewater treatment apparatus according to claim 2, wherein the ceramic membrane is made of titanium dioxide and zirconium dioxide.
4. The polysilicon wastewater treatment apparatus according to claim 1, wherein a liquid separator is further connected through a pipe, comprising:
the device comprises a separation cavity, a fluid storage tank connected with the separation cavity, and a flow supply pump, wherein the flow supply pump is arranged between the separation cavity and the fluid storage tank.
5. The polysilicon wastewater treatment apparatus according to claim 4, wherein the liquid inlet of the separation chamber is opened at a lower position of the separation chamber.
6. The polysilicon wastewater treatment apparatus according to claim 5, wherein the liquid is pure water or calcium chloride or sodium chloride solution.
7. A polysilicon wastewater treatment method is characterized by comprising the following steps:
(1) pressurizing the polycrystalline silicon waste liquid, then feeding the polycrystalline silicon waste liquid into a ceramic membrane system, carrying out solid-liquid separation under the pressure of 0.20MPa-0.55MPa, separating out polyethylene glycol liquid, storing the polyethylene glycol liquid for recycling production, and feeding the solid-liquid mixture subjected to treatment into the step (2);
(2) washing a solid-liquid mixture separated by the ceramic membrane system with pure water to obtain a product comprising: adding the solid mixture of SiC, Si, Fe and impurities into hydrochloric acid, stirring and cleaning to separate out mixed particles of solid SiC, solid Si and impurities;
(3) adding the solid SiC and Si mixed particles into a fluid separator, controlling the flow rate of the fluid separator to layer SiC and Si, respectively collecting the layered SiC and Si, and not separating part of the solid SiC, solid Si and impurities in the mixed state.
8. The polysilicon wastewater treatment method according to claim 7, further comprising, after the step (3): casting and purifying the separated Si to obtain solar grade polysilicon;
and/or; drying the separated SiC, carrying out micro powder grading separation, and selecting and recycling according to the particle size.
9. The polysilicon wastewater treatment method according to claim 7, wherein the hydrochloric acid has a temperature of 30-45 ℃ and a concentration of 10-30% in step (2), and the stirring is further performed for 30-90 minutes in step (2).
10. The polysilicon wastewater treatment method according to claim 7, wherein in the step (3), the flow rate of the fluid separator is 40m/h to 60 m/h.
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