A method and system for the resource utilization of photovoltaic wastewater

Abstract

The present invention provides a photovoltaic wastewater resource utilization method and resource utilization system, the method comprising the following steps: sequentially performing peroxide removal treatment and filtration treatment on photovoltaic wastewater to obtain filtered water; performing silicon element separation treatment on the filtered water to obtain sodium-rich wastewater and silicon-rich wastewater; performing heavy metal removal treatment and anion removal treatment on the sodium-rich wastewater to obtain product alkali solution; the peroxide removal treatment comprises contacting the photovoltaic wastewater with a catalytic filler, the catalytic filler comprises at least one of manganese sand, iron oxide, and aluminum oxide; the silicon element separation treatment comprises treating the filtered water with a silicon element separation membrane element; the silicon element separation membrane element is selected from at least one of polysulfone, polyamide, sulfonated polyether sulfone or sulfonated polysulfone. The photovoltaic wastewater resource utilization method provided by the present invention has the technical effect of recycling photovoltaic wastewater and low cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization, and in particular relates to a photovoltaic wastewater resource utilization method and resource utilization system. Background Art

[0002] The photovoltaic industry, especially in the production of solar cells, uses a variety of chemicals, including hydrofluoric acid, hydrochloric acid, sodium hydroxide, etc. These chemicals are used in processes such as texturing, cleaning, and etching, resulting in the generation of different types of wastewater, mainly including concentrated acid wastewater from pickling and etching processes using hydrofluoric acid and hydrochloric acid, concentrated alkaline wastewater from cleaning processes using alkaline solutions such as sodium hydroxide, dilute acid wastewater containing lower concentrations of acid and fluoride ions from the cleaning process after pickling and etching, dilute alkaline wastewater from the alkaline cleaning process, and ammonia nitrogen wastewater from the passivation treatment or other chemical reactions on the surface of the solar cells.

[0003] Among them, photovoltaic concentrated alkaline wastewater (hereinafter referred to as photovoltaic wastewater) comes from the texturing and alkaline polishing of battery cells. By utilizing the anisotropic corrosion characteristics of silicon in alkaline solution, Si and alkaline solution undergo a series of chemical reactions to form a pyramid velvet surface on the surface of the silicon wafer. Concentrated alkaline wastewater contains hydrogen peroxide and silicon-containing compounds. Among them, hydrogen peroxide will cause safety hazards in the subsequent treatment process, and the presence of silicon-containing compounds will affect the reuse of wastewater. At present, commonly used treatment methods often cannot effectively remove these two pollutants at the same time, resulting in waste of resources and environmental pollution.

[0004] When treating concentrated acid and dilute acid wastewater, a large amount of concentrated alkali is needed to adjust the pH to neutrality so that it can enter the reclaimed water reuse system for reuse. In the above process, the purchase of concentrated alkali is a large economic expense. The concentrated alkali wastewater generated by the production of battery cells contains some hydrogen peroxide and silicon dioxide. Therefore, the concentrated alkali wastewater can be used for the neutralization of concentrated acid and dilute acid wastewater after removing hydrogen peroxide and silicon dioxide from the concentrated alkali wastewater by selecting a suitable process.

[0005] Therefore, developing a method for resource utilization of photovoltaic wastewater has become the current research direction. Summary of the invention

[0006] The present invention provides a method for resource utilization of photovoltaic wastewater, which realizes the recycling of photovoltaic wastewater and has a technical effect of low cost.

[0007] The present invention also provides a photovoltaic wastewater resource utilization system, which has the effect of being able to recycle photovoltaic wastewater and having low operating costs.

[0008] The present invention provides a method for resource utilization of photovoltaic wastewater, which comprises the following steps:

[0009] The photovoltaic wastewater is sequentially subjected to peroxide removal treatment and filtration treatment to obtain filtered water;

[0010] The filtered water is subjected to silicon element separation treatment to obtain sodium-rich wastewater and silicon-rich wastewater;

[0011] The sodium-rich wastewater is subjected to heavy metal removal treatment and anion removal treatment to obtain a product alkali solution;

[0012] The peroxide removal treatment comprises contacting the photovoltaic wastewater with a catalytic filler, wherein the catalytic filler comprises at least one of manganese sand, iron oxide, and aluminum oxide;

[0013] The silicon element separation treatment includes treating the filtered water using a silicon element separation membrane element; the silicon element separation membrane element is selected from at least one of a polysulfone membrane element, a polyamide membrane element, a sulfonated polyethersulfone membrane element or a sulfonated polysulfone membrane element.

[0014] The photovoltaic wastewater resource utilization method as described above, wherein the method further comprises using a dispersant, an alkali metal bicarbonate, an alkali metal halide and carbon dioxide to perform silicon element precipitation treatment on the silicon-rich wastewater to obtain silicon dioxide and a mother liquor including sodium carbonate;

[0015] The dispersant is selected from at least one of disodium ethylenediaminetetraacetate, hexadecyltrimethylammonium chloride, lauryl alcohol polyoxyethylene ether, and sodium dodecyl sulfate.

[0016] As described above, in the photovoltaic wastewater resource utilization method, in the silicon element sedimentation treatment, the mass of the dispersant is 0.5~2% of the mass of SiO2 in the silicon-rich wastewater; the mass ratio of the alkali metal bicarbonate to SiO2 in the silicon-rich wastewater is 0.6~1.2:1, and the mass of the alkali metal halide is 0.5~1% of the mass of SiO2 in the silicon-rich wastewater.

[0017] In the photovoltaic wastewater resource utilization method as described above, the treatment temperature of the silicon element precipitation treatment is 60-80° C., the carbon dioxide filling pressure is 0.3-0.8 MPa, and the pressure holding time is 40-120 min.

[0018] The photovoltaic wastewater resource utilization method as described above, wherein, further comprises introducing carbon dioxide into the mother liquor comprising sodium carbonate to convert the sodium carbonate into sodium bicarbonate, and using the obtained mixed system as a raw material for the silicon element precipitation treatment.

[0019] The photovoltaic wastewater resource utilization method as described above, wherein the filtration treatment also includes heat exchange treatment before the filtration treatment; and / or,

[0020] The filtration treatment includes sand filtration treatment, ultrafiltration treatment and security filtration treatment performed in sequence, the ultrafiltration treatment uses any one of organic ultrafiltration membrane or inorganic ultrafiltration membrane, the treatment pressure of the ultrafiltration treatment is 0.05~0.5MPa; the filtration accuracy of the security filtration is 5~40μm; and / or,

[0021] The heavy metal removal treatment uses at least one of a sulfonic acid resin and a carboxyl resin; the anion removal treatment uses at least one of an amino acrylic resin and an amino styrene resin; and / or,

[0022] After the anion removal treatment is performed, a safety filtration treatment with a filtration accuracy of less than 0.2 μm is also performed.

[0023] The present invention also provides a photovoltaic wastewater resource utilization system, which is used to implement any of the photovoltaic wastewater resource utilization methods described above, wherein the system comprises a peroxide removal unit, a filtration unit, a silicon element separation unit, and a heavy metal anion removal unit connected in sequence;

[0024] The inlet of the heavy metal anion removal unit is communicated with the sodium-rich wastewater outlet of the silicon element separation unit.

[0025] The photovoltaic wastewater resource utilization system as described above, wherein the peroxide removal unit comprises a peroxide removal device;

[0026] The peroxide removal device comprises a packing layer, a gas-liquid separator, a clean water tank, a gas storage tank, an aeration pipe, and a compression pump;

[0027] The outlet of the packing layer is communicated with the inlet of the gas-liquid separator;

[0028] The liquid outlet of the gas-liquid separator is in communication with the clean water tank;

[0029] The gas outlet of the liquid separator is in communication with the gas storage tank;

[0030] The gas outlet of the gas storage tank is in communication with the gas inlet of the clean water tank;

[0031] The aeration pipe is in communication with the inlet of the filter material layer;

[0032] The compression pump is communicated with the gas inlet of the gas storage tank.

[0033] In the photovoltaic wastewater resource utilization system as described above, the thickness of the filler layer is 800-1200 mm, and includes activated carbon, coal powder, catalytic filler, and quartz sand arranged in sequence from bottom to top.

[0034] The photovoltaic wastewater resource utilization system as described above, wherein it further comprises a silicon element sedimentation unit, the inlet of the silicon element sedimentation unit is connected to the silicon-rich wastewater outlet of the silicon element separation unit; and / or,

[0035] A heat exchange unit is also included, and the peroxide removal unit is communicated with the filtering unit through the heat exchange unit.

[0036] The photovoltaic wastewater resource utilization method provided by the present invention can remove peroxides in the wastewater and intercept silicon dioxide through special membrane technology, and finally realize the recycling of photovoltaic wastewater. It has the technical effect of realizing the recycling of photovoltaic wastewater and having low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced one by one below. Obviously, the drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0038] Figure 1 A flow chart of a photovoltaic wastewater resource utilization method provided by the present invention;

[0039] Figure 2 A structural diagram of the first photovoltaic wastewater resource utilization system provided by the present invention;

[0040] Figure 3 This is a structural diagram of a peroxide removal device;

[0041] Figure 4 A structural diagram of a second photovoltaic wastewater resource utilization system provided by the present invention;

[0042] Figure 5 A device diagram of a second photovoltaic wastewater resource utilization system provided by the present invention;

[0043] Figure 6 This is an equipment diagram of the third photovoltaic wastewater resource utilization system provided by the present invention.

[0044] Description of reference numerals:

[0045] 100-peroxide removal unit;

[0046] 101-peroxide removal device;

[0047] 1001-filter pool water inlet pipe;

[0048] 1002-filler support;

[0049] 1003-support layer;

[0050] 1004- aeration pipe;

[0051] 1005- aeration branch pipe;

[0052] 1006-water cap;

[0053] 1007-filling layer;

[0054] 1008- filtration pool;

[0055] 1009-Filter pool cover;

[0056] 1010-gas-water mixture outlet pipe;

[0057] 1011-gas-liquid separator;

[0058] 1012-gas-liquid separator water outlet pipe;

[0059] 1013-gas-liquid separator outlet pipe;

[0060] 1014-first mesh partition;

[0061] 1015-water flow cap;

[0062] 1016- second mesh partition;

[0063] 1017-Clean water tank;

[0064] 1018-Clean water tank outlet pipe;

[0065] 1019-Compression pump;

[0066] 1020-Gas storage tank;

[0067] 1021- oxygen-rich gas aeration pipe;

[0068] 1022- oxygen-rich gas aeration branch pipe;

[0069] 200- filtration unit;

[0070] 201-Sand filtration equipment;

[0071] 202-Ultrafiltration equipment;

[0072] 203-first security filter;

[0073] 300-Silicon element separation unit;

[0074] 301-Silicon element membrane separation equipment;

[0075] 400-Heavy metal anion removal unit;

[0076] 401-Heavy metal resin adsorption equipment;

[0077] 402-Anion resin adsorption equipment;

[0078] 403-Second security filter;

[0079] 500-Silicon element precipitation unit;

[0080] 501-pressure keeping kettle;

[0081] 600-heat exchange unit;

[0082] 601-Shell and tube heat exchanger. DETAILED DESCRIPTION

[0083] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0084] In the prior art, photovoltaic wastewater is often not directly reused for neutralization of acidic solutions. The inventor speculates that the reason may be that the hydrogen peroxide and silicon-containing compounds contained in photovoltaic wastewater cannot be removed at the same time. Hydrogen peroxide will cause safety hazards in the subsequent treatment process, and the presence of silicon-containing compounds will affect the reuse of wastewater. Therefore, if a new treatment process can be developed to achieve the simultaneous removal of hydrogen peroxide and silicon-containing compounds, photovoltaic wastewater can be reused.

[0085] Based on this, the first aspect of the present invention protects a method for resource utilization of photovoltaic wastewater, which comprises the following steps:

[0086] The photovoltaic wastewater is sequentially subjected to peroxide removal treatment and filtration treatment to obtain filtered water;

[0087] The filtered water is subjected to silicon element separation treatment to obtain sodium-rich wastewater and silicon-rich wastewater;

[0088] The sodium-rich wastewater is subjected to heavy metal removal treatment and anion removal treatment to obtain a product alkali solution;

[0089] The peroxide removal treatment includes contacting the photovoltaic wastewater with a catalytic filler, the catalytic filler including at least one of manganese sand, iron oxide, and aluminum oxide;

[0090] The silicon element separation treatment includes treating the filtered water using a silicon element separation membrane element; the silicon element separation membrane element is selected from at least one of a polysulfone membrane element, a polyamide membrane element, a sulfonated polyethersulfone membrane element or a sulfonated polysulfone membrane element.

[0091] Among them, photovoltaic wastewater comes from the cell texturing and alkali polishing process, and contains hydrogen peroxide and silicon-containing compounds. The main characteristics of typical photovoltaic wastewater are as follows: water temperature 50~60℃, NaOH content of 0.5wt%~4wt%, Si content of 0.2wt%~1wt%, peroxide content of 0.5wt%~3wt%, COD content of 200~3000ppm. Since hydrogen peroxide poses a threat to production safety, it needs to be removed by peroxide removal treatment. The peroxide removal treatment includes contacting photovoltaic wastewater with catalytic fillers, which include at least one of manganese sand (the main component is manganese dioxide), iron oxide, and aluminum oxide. When the above substances come into contact with hydrogen peroxide, they can promote the decomposition of hydrogen peroxide into water and oxygen, thereby removing peroxides from photovoltaic wastewater.

[0092] The photovoltaic wastewater from which hydrogen peroxide has been removed is further filtered to remove suspended matter and large particles contained therein, thereby obtaining filtered water. The filtration treatment may be carried out using common filtration methods in the art, such as sand filtration, ultrafiltration, or filtration using a security filter.

[0093] The filtered water is further treated with silicon element separation using a silicon element separation membrane element. The silicon element separation membrane element can use a common system structure in the field, and is selected from at least one membrane element of polysulfone, polyamide, sulfonated polyethersulfone or sulfonated polysulfone. The silicon element separation membrane element can separate the 1-valent hydroxide anions and the 2-valent silicate anions in the filtered water, and realize the separation of sodium hydroxide and sodium silicate in the filtered water. Specifically, a liquid enriched with sodium hydroxide is obtained on one side of the silicon element separation membrane element, which is called sodium-rich wastewater; a liquid enriched with sodium silicate is obtained on the other side of the membrane, which is called silicon-rich wastewater. In silicon-rich wastewater, the mass fraction of silicon dioxide can reach 3%~6%.

[0094] The present invention does not limit the specific processing conditions for silicon element separation treatment, and common conditions in the art can be used. In one embodiment, the silicon element membrane separation equipment used for silicon element separation treatment uses at least one type of special alkali-resistant special membrane selected from polysulfone, polyamide, sulfonated polyethersulfone or sulfonated polysulfone, and the membrane operating flux is 10~30L / (m 2 ·h); the operating pressure of the silicon element membrane separation equipment is 5~8MPa, and the operating temperature is 25~35℃. The silicon element membrane separation equipment is not limited to the combination of one or more stages, one or more sections, etc.

[0095] After the sodium-rich wastewater is subjected to heavy metal removal treatment and anion removal treatment, the product alkali solution can be obtained. After being collected in the feed liquid barrel, it is pumped to the photovoltaic workshop for reuse. Among them, the heavy metal removal treatment can remove heavy metal elements in the sodium-rich wastewater, and the anion removal treatment can remove anions such as sulfate and chloride ions in the sodium-rich wastewater. The present invention does not limit the specific treatment method for the heavy metal removal treatment and anion removal treatment of sodium-rich wastewater, and conventional methods in the art can be used. For example, at least one resin selected from sulfonic acid resin and carboxyl resin can be used to remove heavy metals, and at least one resin selected from aminoacrylic resin and aminostyrene resin can be used to remove anions.

[0096] It is to be understood that the present invention does not limit the execution order of the heavy metal removal treatment and the anion removal treatment, and the heavy metal removal treatment may be performed first, and then the anion removal treatment, or the reverse order may be adopted. Furthermore, the present invention also does not limit the execution times of the heavy metal removal treatment and the anion removal treatment, and the heavy metal removal treatment and the anion removal treatment may be performed once or multiple times.

[0097] In order to further reduce the concentration of suspended particles in the sodium-rich wastewater, in one embodiment, after the sodium-rich wastewater is treated with heavy metal removal and anion removal, it also includes a security filtration treatment to obtain a product alkali solution. The concentration of sodium hydroxide in the product alkali solution is 3-5%, the Si content is <100 ppm, and the COD content is <30 ppm. The product alkali solution can be used in the photovoltaic workshop for texturing, alkali polishing and other processes. The indicators meet the requirements of electronic-grade NaOH in the photovoltaic workshop, reducing the use of electronic-grade purity NaOH chemicals.

[0098] The photovoltaic wastewater resource utilization method provided by the present invention can remove peroxides in photovoltaic wastewater and intercept silicon elements through special membrane technology, which has the technical effect of realizing the recycling of photovoltaic wastewater and low cost.

[0099] In order to achieve the recovery of silicon elements, the photovoltaic wastewater resource utilization method provided by the present invention also includes using a dispersant, alkali metal bicarbonate, alkali metal halide and carbon dioxide to carry out silicon element precipitation treatment on silicon-rich wastewater to obtain silicon dioxide and a mother liquor including sodium carbonate; the dispersant is selected from at least one of disodium ethylenediaminetetraacetate, hexadecyltrimethylammonium chloride, lauryl alcohol polyoxyethylene ether, and sodium dodecyl sulfate.

[0100] Among them, the silicon element precipitation treatment includes contacting the dispersant, alkali metal bicarbonate (for example, at least one selected from sodium bicarbonate, potassium bicarbonate, and lithium bicarbonate), alkali metal halide (for example, at least one selected from sodium chloride, potassium chloride, and lithium chloride) and carbon dioxide with the silicon-rich wastewater. Specifically, the dispersant, alkali metal bicarbonate, alkali metal halide and silicon-rich wastewater are first mixed, and then carbon dioxide is charged into the mixed system and the pressure is maintained for a period of time.

[0101] The main component of the silicon-rich solution is sodium silicate, which exists in the form of (SiO2)n·Na2O, and the modulus n is 1.8~3.3. Alkali metal bicarbonate can provide bicarbonate, which is conducive to the precipitation of silicon dioxide in (SiO2)n·Na2O; alkali metal halides are used to improve the whiteness of the product. The compound dispersant can promote the dissolution of carbon dioxide gas in the reaction solution and the ionization of bicarbonate in the reaction system, and promote the formation of silica colloid; at the same time, the dispersant can effectively coat the surface of the particles, reduce the surface energy of the particles, reduce particle agglomeration, and improve the dispersibility of the particles. As long as part of the loss of alkali metal bicarbonate and carbon dioxide is supplemented in time, the process can be carried out continuously and stably, which not only greatly reduces the manufacturing cost of silica colloid, but also greatly reduces the emission of salt-containing and acidic wastewater and carbon dioxide.

[0102] The present invention does not limit the specific treatment conditions for silicon element precipitation treatment, as long as the requirement of converting silicon element in silicon-rich wastewater into silicon dioxide is met.

[0103] The method provided by the present invention realizes the effective removal of peroxides and the efficient retention of silicon elements through the combination of catalytic oxidation and membrane separation technology, controls the TDS index of photovoltaic industry wastewater, ensures the recovery and utilization of high-quality NaOH and silicon dioxide, improves the environmental protection and economy of battery production, and promotes the recycling of resources.

[0104] In one embodiment, in the silicon element precipitation treatment, the mass of the dispersant is 0.5-2% of the mass of SiO2 in the silicon-rich wastewater; the mass ratio of alkali metal bicarbonate to SiO2 in the silicon-rich wastewater is 0.6-1.2:1, and the mass of chlor-alkali metal halide is 0.5-1% of the mass of SiO2 in the silicon-rich wastewater. Due to the appropriate raw material addition ratio, the above method can further reduce the agglomeration of silicon dioxide particles and improve the dispersibility of the particles. Furthermore, a dispersant including disodium ethylenediaminetetraacetate can also be selected, and the mass ratio of disodium ethylenediaminetetraacetate to the remaining dispersants is controlled to be =1:(0.5-1.2), so as to obtain a better particle dispersion effect.

[0105] In a more specific embodiment, the treatment temperature of the silicon element precipitation treatment can be controlled to be 60~80°C, the carbon dioxide filling pressure can be 0.3~0.8MPa, and the pressure holding time can be 40~120min, thereby further improving the recovery rate of silicon element in the method provided by the present invention.

[0106] Since the obtained mother liquor contains sodium carbonate, in one embodiment, the method provided by the present invention further comprises introducing carbon dioxide into the mother liquor containing sodium carbonate to convert the sodium carbonate contained therein into sodium bicarbonate, and using the obtained mixed system as a raw material for silicon element precipitation treatment. The above process can convert sodium carbonate back into the raw material required for silicon element precipitation treatment, thereby reducing the cost of the photovoltaic wastewater resource utilization method provided by the present invention.

[0107] In one embodiment, when the temperature of the photovoltaic wastewater is high, the photovoltaic wastewater is further subjected to heat exchange treatment before filtering, and the heat exchange treatment can reduce the temperature of the photovoltaic wastewater to 25-35° C. The present invention does not limit the specific execution equipment of the heat exchange treatment. In one embodiment, a heat exchanger can be used, and the heat exchanger is selected from at least one of a shell and tube heat exchanger and a plate heat exchanger, and the heat exchange medium is water.

[0108] More specifically, in order to improve the filtering treatment effect of the photovoltaic wastewater resource utilization method provided by the present invention, in one embodiment, the filtering treatment includes sand filtration treatment, ultrafiltration treatment and security filtration treatment performed in sequence, and the ultrafiltration treatment uses any one of organic ultrafiltration membrane or inorganic ultrafiltration membrane, and the ultrafiltration pressure (that is, the circulation pressure) is 0.05~0.5MPa; the filtration accuracy of the security filtration is 5~40μm, that is, the filter element pore size of the security filter used is 5~40μm. Sand filtration treatment can remove suspended matter and macromolecular organic matter in wastewater; ultrafiltration treatment can remove suspended matter and increase the operating time of special membranes; and the security filter prevents large particles from entering the next system. At the same time, controlling the flow rate of the filtration treatment to 10~25m / h can achieve better filtration effect while obtaining higher filtration efficiency.

[0109] In one embodiment, the heavy metal removal treatment uses a heavy metal removal ion exchange device, which includes at least one of a sulfonic acid resin and a carboxyl resin; the anion removal treatment uses an anion removal exchange device, which includes at least one of an amino acrylic resin and an amino styrene resin. Further, after the anion removal treatment, a security filtration treatment with a filtration accuracy of <0.2μm can be performed. The above security filtration treatments can all be performed using a security filter.

[0110] Figure 1 This is a flow chart of a photovoltaic wastewater resource utilization method provided by the present invention. Figure 1As shown, photovoltaic wastewater is first treated to remove peroxides, and the treated product is subjected to heat exchange treatment and then filtered, including sand filtration, ultrafiltration and security filtration, followed by silicon separation treatment to obtain sodium-rich wastewater and silicon-rich wastewater. The sodium-rich wastewater is treated to remove heavy metals and anions before being returned to the photovoltaic workshop for reuse. The silicon-rich wastewater is treated to precipitate silicon to obtain white carbon black. The mother liquor including sodium carbonate is regenerated with carbon dioxide to obtain a mixed system including sodium bicarbonate, which is reused as a raw material for silicon precipitation treatment.

[0111] A second aspect of the present invention provides a photovoltaic wastewater resource utilization system, which is used to execute the photovoltaic wastewater resource utilization method provided by the first aspect of the present invention. Figure 2 The first photovoltaic wastewater resource utilization system provided by the present invention is shown in FIG. Figure 2 As shown, the device includes 100-peroxide removal unit, 200-filtration unit, 300-silicon element separation unit, and 400-heavy metal anion removal unit which are connected in sequence; wherein, the inlet of 400-heavy metal anion removal unit is connected to the sodium-rich wastewater outlet of 300-silicon element separation unit.

[0112] 100-Peroxide removal unit is used to perform peroxide removal treatment. The present invention does not limit the specific structure of 100-peroxide removal unit, as long as it meets the requirement of being able to perform peroxide removal treatment. In one embodiment, 100-peroxide removal unit includes a container containing catalytic filler, photovoltaic wastewater enters the container, and under the action of the catalytic filler, hydrogen peroxide decomposes, thereby achieving the purpose of removing peroxide.

[0113] 200- filtration unit is used to perform filtration treatment. The present invention does not limit the specific structure of 200- filtration unit, as long as it can remove the suspended matter and macromolecular organic matter contained in photovoltaic wastewater. For example, in one embodiment, 200- filtration unit includes 201- sand filter equipment, 202- ultrafiltration equipment and security filter connected in sequence.

[0114] 300-Silicon element separation unit is used to perform silicon element separation treatment. 300-Silicon element separation unit includes a silicon sodium membrane separation device, which is used to separate sodium element and silicon element to obtain silicon-rich wastewater and sodium-rich wastewater. Among them, 301-Silicon element membrane separation equipment includes at least one membrane element selected from polysulfone, polyamide, sulfonated polyethersulfone or sulfonated polysulfone.

[0115] 400-heavy metal anion removal unit is used to remove heavy metals and anions contained in sodium-rich wastewater. The present invention does not limit the specific structure of 400-heavy metal anion removal unit, as long as it meets the requirement of removing heavy metals and anions contained in photovoltaic wastewater. In one embodiment, 400-heavy metal anion removal unit includes 401-heavy metal resin adsorption equipment and 402-anion resin adsorption equipment, wherein 401-heavy metal resin adsorption equipment includes at least one of sulfonic acid resin and carboxyl resin, and 402-anion resin adsorption equipment includes at least one of amino acrylic resin and aminostyrene resin.

[0116] The operation process of the above system is as follows: photovoltaic wastewater first enters the 100-peroxide removal unit for peroxide removal treatment, and then enters the 200-filtration unit for filtration treatment to obtain filtered water; the filtered water enters the 300-silicon element separation unit for silicon element separation treatment to obtain sodium-rich wastewater and silicon-rich wastewater; the sodium-rich wastewater enters the 400-heavy metal anion removal unit for heavy metal removal treatment and anion removal treatment, and the product is alkali solution.

[0117] The photovoltaic wastewater resource utilization system provided by the present invention can remove hydrogen peroxide in the wastewater and intercept silicon dioxide through special membrane technology, and finally realize the recycling of photovoltaic wastewater. It has the technical effect of realizing the recycling of photovoltaic wastewater at a low cost.

[0118] To further enhance the peroxide removal effect, in one embodiment, in the photovoltaic wastewater resource utilization system provided by the present invention, 100 - peroxide removal unit includes 101 - peroxide removal device.

[0119] Figure 3 This is a structural diagram of a 101-peroxide removal device in the photovoltaic wastewater resource utilization system provided by the present invention. Figure 3 As shown, the device includes 1007-packing layer, 1011-gas-liquid separator, 1017-clean water tank, 1020-gas storage tank, 1004-aeration pipe, 1019-compression pump;

[0120] The outlet of the packing layer 1007 is connected to the inlet of the gas-liquid separator 1011;

[0121] 1011-the liquid outlet of the gas-liquid separator is connected to 1017-the clean water tank;

[0122] 1011 - the gas outlet of the gas-liquid separator is connected to 1020 - the gas storage tank;

[0123] The gas outlet of the gas storage tank 1020 is connected to the gas inlet of the clean water tank 1017;

[0124] 1004-the aeration pipe is connected to the inlet of the filter material layer;

[0125] 1019-Compression pump is connected to the gas inlet of 1020-gas storage tank.

[0126] In addition, the device also includes components. In detail, the specific structure of the device is as follows:

[0127] The 101-peroxide removal device includes a 1007-filling layer, a 1008-filtering pool and a 1017-clean water tank, wherein the 1008-filtering pool and the 1017-clean water tank are connected by a 1015-flowing water cap, and the 1008-filtering pool is designed to be inlet and outlet from the bottom, so that the wastewater is fully in contact with the 1007-filling layer, and the peroxide in the wastewater is decomposed by the 1007-filling layer to generate oxygen. The 1007-filling layer bracket is arranged at the bottom of the 1008-filtering pool, and the 1003-supporting layer is arranged above the 1002-filling bracket to support the 1007-filling layer; the 1001-filtering pool water inlet pipe introduces photovoltaic wastewater from the bottom of the reaction pool and below the 1003-supporting layer; the 1003-supporting layer is provided with a 1006-water cap, and the wastewater can pass through the 1006-water cap to evenly distribute the water in the 1008-filtering pool. 1004-aeration pipe and 1005-aeration branch pipe are placed under the water inlet pipe, and air is distributed from 1004-aeration pipe to 1005-aeration branch pipe, so that the filler in 1007-filling layer is slightly fluidized, increasing the area for the reaction between the filler and the peroxide, and improving the reaction efficiency; 1009-filter tank top cover is designed with a slope, with the middle as the highest point, which is convenient for collecting the gas-water mixture; 1010-gas-water mixture outlet pipe is set on the top cover to collect the oxygen-water mixture rich in oxygen flowing out through overflow or power; 1010-gas-water mixture The water outlet pipe of the material is connected to the 1011-gas-liquid separator, the water outlet pipe of the 1012-gas-liquid separator is located at the lower end of the 1011-gas-liquid separator, and the gas outlet pipe (gas outlet) of the 1013-gas-liquid separator is designed at the upper end of the 1011-gas-liquid separator. The liquid separated by the 1011-gas-liquid separator is returned to the 1008-filtration tank through the 1012-gas-liquid separator water outlet pipe (liquid outlet), and the oxygen-rich gas is collected to the 1020-gas storage tank through the 1013-gas-liquid separator gas outlet pipe (gas outlet) through the 1019-compression pump. A 1014-first mesh partition with a pore size of 0.5-2mm is set at the rear end of the water outlet pipe (liquid outlet) of the 1012-gas-liquid separator. After the wastewater is filtered by the filler powder through the 1014-first mesh partition, it is introduced into the 1017-clean water tank through the 1015-flow cap set in the 1008-filter tank and the 1017-clean water tank. The 1015-flow cap has a pore size of 1 mm, which can block even smaller fillers. The gas outlet of the 1020-gas storage tank is connected to the bottom of the clean water tank, and the oxygen-rich gas is introduced into the 1017-clean water tank through the 1021-oxygen-rich gas aeration pipe and the 1022-oxygen-rich gas aeration branch pipe in turn to disturb the liquid therein; the water outlet of the 1017-clean water tank is located at the lower end of the 1017-clean water tank, and a 1016-second mesh partition with a pore size of 0.5-1mm is set at the water outlet. Under the turbulence of the oxygen-rich gas, the fillers and impurity particles flowing into the clean water tank are blocked, reducing the pressure of the rear heat exchange and filtration process. 1016-A clean water tank outlet pipe 1018 is set at the rear end of the second mesh partition, and 1018-The clean water tank outlet pipe is the outlet of 100-peroxide removal unit.

[0128] Since the presence of peroxides can cause the separation layer on the surface of the special membrane to fail, the catalytic filler included in the 1007-filler layer is used to decompose the peroxide and part of the COD into water and oxygen in the device through catalytic oxidation. The generated oxygen also disturbs the fluid, increases the contact between the peroxide, COD and the filler, accelerates the decomposition, and reduces the peroxide content to a safe level, with a removal rate of more than 90%. At the same time, the combination of multiple fillers can also effectively adsorb COD. Oxygen-rich gas is introduced into the 1017-clean water tank to disturb the liquid therein, further promote the decomposition of the residual peroxide, and oxidize and remove impurities from the COD therein. The removal of peroxides and COD can enable the subsequent silicon element separation unit to operate stably.

[0129] More specifically, the filtration flow rate of photovoltaic wastewater in the 101-peroxide removal device can be controlled to 4-12 m / h, which can achieve better filtration effect.

[0130] More specifically, in order to make the 101-peroxide removal device have a better peroxide removal effect, in one embodiment, the total thickness of the 1007-filling layer is 800-1200mm, including activated carbon, coal powder, catalytic filler, and quartz sand arranged in sequence from bottom to top. More specifically, the catalyst filler is 1000mm thick, with a total of six layers. From bottom to top, they are activated carbon, coal powder, catalytic filler, and quartz sand. The bottom layer is filled with activated carbon particles of 6-8mm and a thickness of 10cm; the coal powder particle size is 2mm~3mm and a thickness of 10cm. Three layers of catalytic fillers are filled in the middle, and the filling thickness is respectively: 4-8mm fills 10cm, 2-4mm fills 10cm, and 1-2mm fills 50cm. The top is filled with 2-4mm quartz sand, and the filling thickness is 10cm. The use of graded filter material can avoid the displacement of the catalytic filler and maintain the catalytic performance, so that the 101-peroxide removal device has a better peroxide removal effect.

[0131] Figure 4 The second photovoltaic wastewater resource utilization system provided by the present invention is shown in FIG. Figure 4 As shown, the device includes a 100-peroxide removal unit, a 200-filtration unit, a 300-silicon separation unit, and a 400-heavy metal anion removal unit, which are connected in sequence, and also includes a 600-heat exchange unit and a 500-silicon sedimentation unit. Among them, the 100-peroxide removal unit is connected to the 200-filtration unit through the 600-heat exchange unit, and the inlet of the 500-silicon sedimentation unit is connected to the silicon-rich wastewater outlet of the 300-silicon separation unit.

[0132] Among them, the 500-silicon element sedimentation unit is used to perform silicon element sedimentation treatment. The present invention does not limit the specific equipment selection of the 500-silicon element sedimentation unit, and it can meet the requirements of being able to accommodate silicon-rich wastewater in contact with dispersants, bicarbonates, sodium chloride and carbon dioxide, and maintaining a pressure of 0.3~0.8MPa for 40~120min. In one embodiment, the 500-silicon element sedimentation unit includes a pressure-resistant container that can be used for solid-liquid mixing, and specific equipment commonly used in the art, such as a pressure-maintaining kettle, can be used.

[0133] 600- heat exchange unit is used to perform heat exchange treatment, which can reduce the temperature of photovoltaic wastewater. The present invention does not limit the specific equipment included in 600- heat exchange unit. In one embodiment, 600- heat exchange unit includes at least one of a shell and tube heat exchanger and a plate heat exchanger, and the heat exchange medium is water.

[0134] Figure 5 The equipment diagram of the second photovoltaic wastewater resource utilization system provided by the present invention is as follows: Figure 5 As shown, the system includes 101-peroxide removal device, 601-shell-and-tube heat exchanger, 201-sand filter equipment, 202-ultrafiltration equipment and 203-first security filter, 301-silicon element membrane separation equipment, 401-heavy metal resin adsorption equipment, 402-anion resin adsorption equipment, 403-second security filter, 501-pressure kettle, wherein 601-shell-and-tube heat exchanger belongs to 600-heat exchange unit, 101-peroxide removal device belongs to 100-peroxide removal unit, 201-sand filter equipment, 202-ultrafiltration equipment and 203-first security filter belong to 200-filtration unit, 301-silicon element membrane separation equipment belongs to 300-silicon element separation unit, 401-heavy metal resin adsorption equipment, 402-anion resin adsorption equipment and 403-second security filter belong to 400-heavy metal anion removal unit, 501-pressure kettle belongs to 500-silicon element sedimentation unit.

[0135] The operation process of the above system is as follows: photovoltaic wastewater first enters 601-shell and tube heat exchanger for cooling, then enters 101-peroxide removal device for peroxide removal treatment, and then passes through 201-sand filter equipment, 202-ultrafiltration equipment and security filter for filtration treatment in sequence to obtain filtered water; the filtered water enters 301-silicon element membrane separation equipment for silicon element separation treatment to obtain sodium-rich wastewater and silicon-rich wastewater; the sodium-rich wastewater passes through 401-heavy metal resin adsorption equipment and 402-anion resin adsorption equipment in sequence to perform heavy metal removal treatment and anion removal treatment to obtain product alkali solution; the silicon-rich wastewater enters 501-pressure kettle, contacts with dispersant, bicarbonate, sodium chloride and carbon dioxide, obtains silicon dioxide and mother liquor including sodium carbonate, the mother liquor including sodium carbonate reacts with carbon dioxide to generate sodium bicarbonate, and is reused in 501-pressure kettle.

[0136] The photovoltaic wastewater resource utilization method provided by the present invention is further described below in conjunction with specific implementation methods.

[0137] Embodiment 1:

[0138] This embodiment uses Figure 6 The equipment of the photovoltaic wastewater resource utilization system shown treats the following substances: photovoltaic industry cell wastewater effluent, water temperature 60°C, NaOH content of 3wt%, Si content of 1wt%, peroxide (hydrogen peroxide) content of 1.5 wt%, COD content of 1500ppm.

[0139] Figure 6 and Figure 5 Basically the same, the difference is that Figure 6 In the device, the wastewater first enters 401-heavy metal resin adsorption equipment, then enters 402-anion resin adsorption equipment, and finally re-enters 401-heavy metal resin adsorption equipment and 403-second security filter to obtain product alkali solution.

[0140] 1) Photovoltaic wastewater is introduced into the 101-peroxide removal device through the 1001-filter pool inlet pipe, with a filtration flow rate of 5m / h. The wastewater flows into the 1007-filling layer through the 1006-water cap. The catalyst filler thickness is 1000mm, from bottom to top, the activated carbon particle size is 7mm, the thickness is 10cm; the coal powder particle size is 2mm, the thickness is 10cm; the middle is filled with 3 layers of catalytic filler (the component is manganese sand, and the effective component of manganese sand is manganese dioxide), and the filling thickness is: 7mm particle size is filled with 10cm, 2mm particle size is filled with 10cm, 1.5mm particle size is filled with 50cm; quartz sand particle size is 3mm is filled with 10cm.

[0141] Photovoltaic wastewater passes through the 1007-packing layer, and the peroxide decomposes to generate oxygen; at the same time, air is introduced into the 1004-aeration pipe, which together promotes slight fluidization of the packing and improves the catalytic efficiency; the oxygen-rich gas and water mixture enter the 1011-gas-liquid separator through the 1010-gas-water mixture outlet pipe on the top cover of the 1009-filter tank, and the oxygen-rich gas enters the gas storage tank. The effluent returns to the 1008-filter tank, and after the solid particles are initially separated by the 1014-first mesh partition (aperture 1mm), it flows to the 1017-clean water tank.

[0142] 1017- The wastewater in the clean water tank is further disturbed by oxygen-rich gas, which further promotes the decomposition of residual peroxides, and the COD in it is oxidized and impurities are removed, and then flows to the heat exchange filtration treatment system through 1016- the second mesh partition (pore size 0.5mm).

[0143] 2) After the effluent from the peroxide removal treatment passes through the 601-tube heat exchanger, the wastewater temperature drops to 30°C. It passes through the sand filter, the organic ultrafiltration membrane with a circulating pressure of 0.2MPa, and the 203-first security filter with a filter element pore size of 20μm to remove suspended solids, macromolecular organic matter and large particles in the wastewater, and then enters the 301-silicon element membrane separation equipment.

[0144] 3) 301-Silicon element membrane separation equipment adopts a two-stage membrane separation system, and the special membrane is polysulfone, and the membrane operating flux is 20L / (m 2 ·h), the operating pressure of the membrane separation system is 6MPa, the operating temperature is 25℃, and after separation, sodium-rich wastewater with a NaOH mass concentration of 4.5% and silicon-rich wastewater with a SiO2 mass concentration of 5% are obtained.

[0145] 4) The sodium-rich wastewater is passed through the 401-heavy metal resin adsorption equipment and the 402-anion resin adsorption equipment including sulfonic acid ion exchange resin, amino acrylic resin, and sulfonic acid ion exchange resin at a flow rate of 15m / h (the actual flow order is 401-heavy metal resin adsorption equipment, 402-anion resin adsorption equipment, and 401-heavy metal resin adsorption equipment) to remove heavy metals and anions, and finally filtered through the 403-second security filter with an accuracy of less than 0.2μm. The refined NaOH concentration is 4.5%, the Si content is 80 ppm, and the COD content is 25 ppm, which is reused in the texturing section of the photovoltaic workshop.

[0146] 5) Silicon-rich wastewater is put into a 501-pressure kettle, and dispersants disodium ethylenediaminetetraacetate and sodium dodecyl sulfate are added, with the amount being 1% of the mass of SiO2 in the silicon-rich wastewater, and the mass ratio of disodium ethylenediaminetetraacetate to sodium dodecyl sulfate being 1:0.8; sodium bicarbonate with a mass ratio of 1:0.8 to SiO2 and sodium chloride with an amount of 0.7% of the mass of SiO2 are added. Carbon dioxide is charged to a pressure of 0.5MPa, and the pressure is maintained at 70℃ for 60 min. The silica product with a particle size in the range of 30-60 nm is obtained by filtration. The filtrate is passed through carbon dioxide gas again to convert the sodium carbonate therein into sodium bicarbonate, which is then reused in step 5).

[0147] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0148] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for resource utilization of photovoltaic wastewater, characterized in that: The following steps are involved: The photovoltaic wastewater is sequentially subjected to peroxide removal treatment and filtration treatment to obtain filtered water; The filtered water is subjected to silicon element separation treatment to obtain sodium-rich wastewater and silicon-rich wastewater; The sodium-rich wastewater is subjected to heavy metal removal treatment and anion removal treatment to obtain a product alkali solution; The peroxide removal treatment comprises contacting the photovoltaic wastewater with a catalytic filler, wherein the catalytic filler comprises at least one of manganese sand, iron oxide, and aluminum oxide; The silicon element separation treatment comprises treating the filtered water using a silicon element separation membrane element; the silicon element separation membrane element is selected from at least one of a polysulfone membrane element, a polyamide membrane element, a sulfonated polyethersulfone membrane element or a sulfonated polysulfone membrane element; The method further comprises using a dispersant, an alkali metal bicarbonate, an alkali metal halide and carbon dioxide to perform silicon element precipitation treatment on the silicon-rich wastewater to obtain silicon dioxide and a mother liquor including sodium carbonate; The dispersant is selected from at least one of disodium ethylenediaminetetraacetate, hexadecyltrimethylammonium chloride, lauryl alcohol polyoxyethylene ether, and sodium lauryl sulfate; The method further comprises introducing carbon dioxide into the mother liquor comprising sodium carbonate to convert the sodium carbonate into sodium bicarbonate, and using the obtained mixed system as a raw material for the silicon element precipitation treatment.

2. The photovoltaic wastewater resource utilization method according to claim 1 is characterized in that: In the silicon element sedimentation treatment, the mass of the dispersant is 0.5~2% of the mass of SiO2 in the silicon-rich wastewater; the mass ratio of the alkali metal bicarbonate to SiO2 in the silicon-rich wastewater is 0.6~1.2:1, and the mass of the alkali metal halide is 0.5~1% of the mass of SiO2 in the silicon-rich wastewater.

3. The photovoltaic wastewater resource utilization method according to claim 1, characterized in that: The treatment temperature of the silicon element precipitation treatment is 60-80° C., the carbon dioxide filling pressure is 0.3-0.8 MPa, and the pressure holding time is 40-120 min.

4. The photovoltaic wastewater resource utilization method according to any one of claims 1 to 3, characterized in that: The filtering process also includes heat exchange treatment before the filtering process; and / or, The filtration treatment includes sand filtration treatment, ultrafiltration treatment and security filtration treatment performed in sequence, the ultrafiltration treatment uses any one of organic ultrafiltration membrane or inorganic ultrafiltration membrane, the treatment pressure of the ultrafiltration treatment is 0.05~0.5MPa; the filtration accuracy of the security filtration is 5~40μm; and / or, The heavy metal removal treatment uses at least one of a sulfonic acid resin and a carboxyl resin; the anion removal treatment uses at least one of an amino acrylic resin and an amino styrene resin; and / or, After the anion removal treatment is performed, a safety filtration treatment with a filtration accuracy of less than 0.2 μm is also performed.

5. A photovoltaic wastewater resource utilization system for executing the photovoltaic wastewater resource utilization method according to any one of claims 1 to 4, characterized in that: It includes a peroxide removal unit, a filtration unit, a silicon element separation unit, and a heavy metal anion removal unit which are connected in sequence; the heavy metal anion removal unit includes a heavy metal resin adsorption device and an anion resin adsorption device; The inlet of the heavy metal anion removal unit is communicated with the sodium-rich wastewater outlet of the silicon element separation unit.

6. The photovoltaic wastewater resource utilization system according to claim 5 is characterized in that: The peroxide removal unit includes a peroxide removal device; The peroxide removal device comprises a packing layer, a gas-liquid separator, a clean water tank, a gas storage tank, an aeration pipe, and a compression pump; The outlet of the packing layer is communicated with the inlet of the gas-liquid separator; The liquid outlet of the gas-liquid separator is in communication with the clean water tank; The gas outlet of the gas-liquid separator is in communication with the gas storage tank; The gas outlet of the gas storage tank is in communication with the gas inlet of the clean water tank; The aeration pipe is in communication with the inlet of the filter material layer; The compression pump is communicated with the gas inlet of the gas storage tank.

7. The photovoltaic wastewater resource utilization system according to claim 6 is characterized in that: The packing layer has a thickness of 800-1200 mm and includes activated carbon, coal powder, catalytic filler and quartz sand arranged in sequence from bottom to top.

8. The photovoltaic wastewater resource utilization system according to claim 5 is characterized in that: It also includes a silicon element sedimentation unit, the inlet of which is connected to the silicon-rich wastewater outlet of the silicon element separation unit; and / or, A heat exchange unit is also included, and the peroxide removal unit is communicated with the filtering unit through the heat exchange unit.

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