Silica gel production wastewater treatment process and system

Abstract

The invention relates to a silica gel production wastewater treatment process and system.The process comprises the steps that after silica gel production wastewater is subjected to sedimentation treatment, chemicals are added into supernate to remove silica, and produced water obtained after silica removal is precisely filtered; wherein the pH of the silica gel production wastewater is adjusted by sodium hydroxide during silica removal; carrying out material separation on the filtrate subjected to precise filtration by adopting a reverse osmosis process, adding an agent into the obtained reverse osmosis concentrated water to remove magnesium and calcium, filtering to remove suspended matters, and carrying out evaporative crystallization to obtain sodium sulfate crystal salt; and carrying out desalting treatment on the reverse osmosis produced water to obtain up-to-standard discharge water and reuse water. According to the method, only sodium hydroxide is adopted as a reagent to adjust the pH in the silica removal stage, a large amount of calcium sulfate sludge is not generated, sulfate ions in water are not consumed, meanwhile, the content of sodium sulfate in concentrated water can be increased, the problem of sludge treatment accompanying in traditional silica gel wastewater treatment is effectively solved, and the influence on the wastewater treatment effect is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to a silica gel production wastewater treatment process and system. Background Art

[0002] Silica gel is an important raw material in the fields of construction, electronics, machinery and plastics, but it produces a large amount of wastewater during the production process. The main characteristics of this wastewater are: high acidity. During the production process of silica gel, especially in the pickling process, a large amount of acidic wastewater will be produced, with a pH value of about 2, which is highly acidic; high salt content. The wastewater contains high salts such as sodium sulfate, which can easily inhibit the biodegradation process and increase the difficulty of treatment; high silicon content. The raw materials for silica gel production contain silicon elements, resulting in a high concentration of silicon compounds in the wastewater, which is difficult to effectively decompose by traditional biological treatment methods. Therefore, it is difficult to treat silica gel wastewater.

[0003] For example, a "process for treating wastewater from the production of inorganic silica gel" disclosed in Chinese patent literature has a publication number of CN117049737A. It adjusts the pH of the water by adding limestone to the silica gel wastewater, and sequentially performs flocculation and silicon removal, membrane filtration and resource recovery on the wastewater obtained by adjusting the pH, thereby achieving the purpose of treating the silica gel wastewater. However, since the patent uses lime as the agent for adjusting pH, a large amount of calcium sulfate sludge will be produced, and it will also be mixed with silicon compounds, which is easy to form a complex precipitation structure, causing the particle size, density and other properties of the precipitate to change, affecting the precipitation rate and effect, and further affecting the wastewater treatment effect. At the same time, lime will also consume sulfate ions in the water, affecting the yield of subsequent by-product crystalline salt.

[0004] Therefore, it is an urgent problem to provide a silica gel production wastewater treatment process that is not prone to produce a large amount of sludge and can also increase the yield of by-product crystalline salt. Summary of the invention

[0005] In view of this, the main purpose of the present invention is to provide a silica gel production wastewater treatment process and system, which only uses sodium hydroxide as a reagent to adjust the pH in the silicon removal stage, which neither produces a large amount of calcium sulfate sludge nor consumes sulfate ions in the water. At the same time, it can increase the sodium sulfate content in the concentrated water, effectively solving the sludge treatment problem associated with traditional silica gel wastewater treatment and reducing the impact on the wastewater treatment effect.

[0006] In a first aspect, the present application provides a silica gel production wastewater treatment process, comprising the following steps:

[0007] After the silica gel production wastewater is settled, a reagent is added to the supernatant to remove silicon, and the produced water after silicon removal is precisely filtered; during silicon removal, sodium hydroxide is used to adjust the pH of the silica gel production wastewater;

[0008] The filtrate after precision filtration is subjected to material separation by reverse osmosis process, and the obtained concentrated water is treated with reagents for magnesium and calcium removal, and then filtered to remove suspended matter and evaporated for crystallization to obtain sodium sulfate crystal salt;

[0009] The reverse osmosis produced water is desalinated to obtain qualified discharge water and recycled water.

[0010] In some embodiments, after the silica gel production wastewater is subjected to sedimentation treatment, a reagent is added to the supernatant to remove silicon, and the produced water after silicon removal is finely filtered, including:

[0011] Sedimentation treatment of silica gel production wastewater to remove particulate matter;

[0012] Add reagents in sequence to the supernatant obtained after sedimentation treatment to remove silicon dioxide and part of suspended solids, hardness and colloids; wherein, sodium hydroxide is used to adjust the pH of silica gel production wastewater to 7-8 during silicon removal;

[0013] The produced water after the addition of the agent is precisely filtered to remove bacteria and remaining suspended matter and colloids, and the backwash water after the precise filtration is returned to the sedimentation tank for further sedimentation.

[0014] In some embodiments, the reagents added to the supernatant are sodium aluminate, polyaluminium chloride and polyacrylamide in sequence; and

[0015] The dosage of the sodium aluminate is at least 1.5-2.5 times the mass of the silicon dioxide contained in the supernatant after sedimentation, and the reaction time of the sodium aluminate is 30-60 minutes;

[0016] The dosage of the polyaluminium chloride is 5-100 mg / L;

[0017] The dosage of the polyacrylamide is 1-5 mg / L.

[0018] In some of the embodiments, the precision filtration method is any one of a sand filtration ultrafiltration combination, a sand filtration microfiltration combination, a self-cleaning filtration ultrafiltration combination, a self-cleaning filtration microfiltration combination, tubular ultrafiltration, tubular microfiltration, submerged ultrafiltration or MCR microfiltration; and the material of the ultrafiltration membrane or microfiltration membrane is any one of ceramic, PP, PVDF or PTFE.

[0019] In some embodiments, the hardness-removing agents added to the reverse osmosis concentrated water are sodium hydroxide, sodium carbonate, polyaluminium chloride, polyacrylamide and sulfuric acid in sequence; and

[0020] The pH of the reverse osmosis concentrated water after the addition of sodium hydroxide is 11-12;

[0021] The dosage of the sodium carbonate is 0-3000 mg / L;

[0022] The dosage of the polyaluminium chloride is 5-100 mg / L;

[0023] The dosage of the polyacrylamide is 1-5 mg / L;

[0024] The pH of the reverse osmosis concentrated water after the addition of sulfuric acid is 7-8.

[0025] In some of the embodiments, when the reverse osmosis produced water is desalinated to obtain qualified discharge water and recycled water, the reverse osmosis process is used again to desalinate the reverse osmosis produced water, and the TDS of the qualified discharge water is ≤5000 mg / L, and the pH is 7-9, and the TDS of the recycled water is ≤200 mg / L, sodium sulfate is ≤30 mg / L, and the pH is 7-8.

[0026] In some embodiments, it also includes:

[0027] The precipitate after sedimentation treatment, the silicon-containing sludge after silicon removal and the chemical sludge after concentrated water demagnesium and decalcification are all subjected to sludge concentration and filter pressing. The obtained mud cake is outsourced for disposal, and the filtered filtrate is refluxed for sedimentation again.

[0028] In a second aspect, an embodiment of the present application provides a silica gel production wastewater treatment system, which is used to implement any of the silica gel production wastewater treatment processes described above, including:

[0029] The pretreatment unit includes a sedimentation tank, a silicon removal system, a silicon removal water production tank and a precision filtration system which are connected in sequence;

[0030] The concentration and crystallization unit comprises a filtrate pool, a material separation system, a concentrated water hardness removal system, a concentrated water filtration system, a concentrated brine pool and an evaporation and crystallization system which are sequentially connected and arranged, and the filtrate pool is connected and arranged with the precision filtration system;

[0031] The desalination unit comprises a water production pool, a desalination system and a water recycling pool which are connected in sequence, and the water production pool is connected with the material separation system.

[0032] In some embodiments, the pre-processing unit further comprises:

[0033] A wastewater collection tank, wherein the liquid inlet end is connected to the backwash water outlet end of the precision filtration system, and the liquid outlet end is connected to the wastewater liquid inlet end of the sedimentation tank;

[0034] The sludge treatment system has a sludge feed end which is respectively connected to the sludge discharge ends corresponding to the sedimentation tank, the silicon removal system and the concentrated water hardness removal system, and a filtrate end which is connected to the liquid inlet end of the sedimentation tank, and the sludge treatment system includes a sludge thickening tank and a plate and frame filter press which are connected in sequence.

[0035] In some of the embodiments, the sedimentation tank includes a tank body, a central pipe, a water inlet pipe, a reflector, a baffle, a water outlet pipe and a mud discharge pipe;

[0036] The bottom of the pool body is an inverted cone structure;

[0037] The central tube is vertically arranged inside the tank body;

[0038] The water inlet pipe is arranged from one side of the pool body in a direction perpendicular to the central pipe and is connected to the central pipe;

[0039] The reflecting plate is circumferentially arranged at the bottom of the central tube;

[0040] The baffle is circumferentially arranged on the inner side of the top of the pool body, and a water collecting trough is formed between the baffle and the pool body, and the water collecting trough is connected to the water outlet pipe;

[0041] The mud discharge pipe is arranged from top to bottom along the inner wall of the pool body.

[0042] Technical effects of the present invention:

[0043] After the silica gel production wastewater is treated by sedimentation, only sodium hydroxide is used to adjust the pH during silicon removal. It is not only not easy to produce a large amount of additional sludge, but also ensures that the sulfate ions in the wastewater are not consumed. At the same time, the sodium ions provided can also increase the content of the final byproduct sodium sulfate crystal salt. Not only that, the present application also performs precision filtration on the produced water after silicon removal, and uses the filtered filtrate to be reverse osmosis treated, and the reverse osmosis concentrated water is treated to remove hardness, and then evaporated and crystallized after filtering to remove suspended matter to obtain sodium sulfate crystal salt. Among them, after silicon removal and hardness removal, the obtained byproduct sodium sulfate crystal salt has a higher purity. At the same time, the reverse osmosis produced water is also desalted, so that the discharge water that meets the standards is directly discharged, reducing the cost of sewage discharge, and at the same time, it can also obtain recycled water for production according to actual conditions, reducing the water consumption of tap water during silica gel production.

[0044] Further features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.

[0046] Figure 1 The figure shows a schematic diagram of the process for treating wastewater from silica gel production according to an embodiment of the present application;

[0047] Figure 2Shown is a schematic structural diagram of a silica gel production wastewater treatment system according to an embodiment of the present application;

[0048] Figure 3 Shown is a schematic structural diagram of a sedimentation tank according to an embodiment of the present application. DETAILED DESCRIPTION

[0049] Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0050] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0051] In addition, in order to better illustrate the present disclosure, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present disclosure can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present disclosure.

[0052] Since silica gel wastewater has the characteristics of high acidity, high salt content and high silicon content, lime is used in the prior art to adjust the pH of silica gel wastewater to ensure the normal progress of the subsequent treatment process. However, since silica gel production wastewater also has the characteristics of high salt content and contains high salts such as sodium sulfate, the use of lime to adjust the pH will produce a large amount of calcium sulfate sludge, and it will also be mixed with silicides, thereby increasing the sludge discharge and the sewage discharge cost. Therefore, the present application provides a silica gel production wastewater treatment process that can reduce the sludge discharge. When removing silicon, only NaOH is used, which not only does not produce a large amount of sodium sulfate sludge, but also can increase the sodium sulfate content in the concentrated water without consuming sulfate ions in the wastewater, so that the content of crystalline salt obtained after the wastewater treatment is increased, thereby improving resource utilization.

[0053] like Figure 1 As shown, in the first aspect, the embodiment of the present application provides a silica gel production wastewater treatment process, comprising the following steps:

[0054] S100, after the silica gel production wastewater is subjected to sedimentation treatment, a reagent is added to the supernatant to remove silicon, and the produced water after silicon removal is finely filtered; wherein, sodium hydroxide is used to adjust the pH value of the silica gel production wastewater during silicon removal;

[0055] It should be noted that the water quality of the silica gel production wastewater treated in this step is specifically shown in Table 1. As can be seen from Table 1, this step is aimed at silica gel production wastewater containing a large amount of sulfate. After the silica gel production wastewater is subjected to sedimentation treatment and the particulate matter that can be naturally precipitated is removed, sodium hydroxide is added to the obtained supernatant to adjust the pH value. Compared with the addition of lime, it can effectively reduce the generation of sludge, and at the same time, it can also ensure the subsequent recycling of sulfate and reduce the loss of sulfate.

[0056] Analyze Project unit index pH Dimensionless 1.5-3 TDS (Total Dissolved Solids) mg / L 25000-45000 Sulfate mg / L 15000-30000 Silicon dioxide mg / L 200-400 Total hardness mg / L 100-500

[0057] Table 1 Schematic diagram of silica gel production wastewater water quality

[0058] In some embodiments, after the silica gel production wastewater is subjected to sedimentation treatment, a reagent is added to the supernatant to remove silicon, and the produced water after silicon removal is finely filtered, including:

[0059] Sedimentation treatment of silica gel production wastewater to remove particulate matter;

[0060] Add reagents in sequence to the supernatant obtained after sedimentation treatment to remove silicon dioxide and part of suspended solids, hardness and colloids; wherein, sodium hydroxide is used to adjust the pH of silica gel production wastewater to 7-8 during silicon removal;

[0061] The produced water after the addition of the agent is precisely filtered to remove bacteria and remaining suspended matter and colloids, and the backwash water after the precise filtration is returned to the sedimentation tank for further sedimentation.

[0062] In this embodiment, a sedimentation tank is used to treat the silica gel production wastewater by sedimentation to remove granular substances that can settle naturally, such as silica gel particles, and a circular vertical flow sedimentation tank is preferably used to remove the particles. It should be noted that in order to ensure the removal effect of the sedimentation tank on large particles, the bottom of the sedimentation tank is set to an inverted cone. Since large particles will quickly settle to the bottom under the action of gravity, the tapered slope can guide the settled large particles, which is easier to concentrate and collect than a flat-bottomed sedimentation tank. At the same time, it can also prevent the particles that have settled to the bottom of the pool from being suspended in the water again due to the disturbance of the water flow, thereby ensuring the particle removal effect and obtaining a supernatant.

[0063] Further, the pH of the supernatant is adjusted from 1.5-3 to 7-8 by adding sodium hydroxide. It should be noted that in addition to the silicon removal agent, the reagents added in this embodiment for silicon removal also include a flocculant, that is, the reagents are added in the order of sodium hydroxide, silicon removal agent and flocculant in this embodiment. Among them, the addition of sodium hydroxide changes the wastewater from the original strong acidity to weak alkalinity, which is more conducive to the subsequent silicon removal agent and flocculant to play a role. By adding a silicon removal agent to react with silicon dioxide, it can be converted into an insoluble silicon compound and precipitated, thereby reducing the silicon content in the wastewater, and at the same time, it can also prevent membrane pollution during subsequent membrane treatment, reducing the service life and treatment efficiency of the membrane. In addition, since the precipitation particles generated by the reaction of the silicon removal agent and silicon dioxide are usually small and difficult to precipitate quickly, the flocculant is added in this embodiment to precipitate and condense the fine particles into larger flocs, thereby accelerating the precipitation process, making the precipitation more thorough, and facilitating the subsequent solid-liquid separation. At the same time, it can also remove the settled suspended matter, a part of the hardness and colloids, etc., to achieve the purpose of purifying water quality.

[0064] In addition, this embodiment also performs precision filtration on the produced water after silicon removal, thereby filtering out the formed precipitates, and can also remove the remaining suspended matter, bacteria and colloids, etc., to obtain the filtrate for subsequent evaporation and crystallization to obtain sodium sulfate crystal salt, and to produce reusable recycled water and discharge water that meets the discharge requirements after desalination. It should be noted that this embodiment returns the backwash water that is backwashed after precision filtration to the sedimentation tank, and uses the volume of the sedimentation tank itself to adjust the silica gel production wastewater and the return water to mix them evenly, so as to settle again and circulate the treatment.

[0065] In some embodiments, the reagents added to the supernatant are sodium aluminate, polyaluminium chloride and polyacrylamide in sequence; and

[0066] The dosage of sodium aluminate is at least 1.5-2.5 times the mass of silicon dioxide contained in the supernatant after sedimentation, and the reaction time of sodium aluminate is 30-60 minutes;

[0067] The dosage of polyaluminium chloride is 5-100mg / L;

[0068] The dosage of polyacrylamide is 1-5 mg / L.

[0069] In this embodiment, the desiliconizing agent is preferably sodium aluminate, and the dosage of sodium aluminate is at least 1.5-2.5 times the mass of silicon dioxide contained in the supernatant. Here, it should be noted that the aluminum ions in sodium aluminate can react with the silicon dioxide in the supernatant to generate insoluble aluminosilicate precipitates, and the dosage of sodium aluminate is limited to at least 1.5-2.5 times the mass of silicon dioxide, and the reaction time of sodium aluminate is 30-60min, so as to ensure that there are enough aluminum ions to fully react with silicon dioxide, so that the silicon content of the produced water can be 5mg / L. At the same time, the generated aluminosilicate precipitate has a certain cohesiveness, which is helpful for the subsequent flocculation process, making it easier for the precipitate to form larger flocs, which is convenient for separation. Compared with the common magnesium oxide desiliconization in the prior art, the desiliconization effect is better.

[0070] The following will provide specific experimental results to explain in detail the selection of the silicon removal agent in this embodiment.

[0071] The specific steps of the silicon removal experiment include:

[0072] (1) Take 500 ml of raw water and add alkali to adjust the pH to the specified pH value;

[0073] (2) Add a specified amount of sodium aluminate and stir continuously for 60 minutes, or add a specified amount of magnesium oxide and heat and stir at 40°C for 90 minutes;

[0074] (3) Add 2 mg / L flocculant and react for 2 minutes;

[0075] (4) The supernatant was filtered and the silicon content of the filtrate was tested.

[0076] The experimental results are shown in Table 2.

[0077]

[0078] Table 2 Schematic diagram of silicon removal test results

[0079] As shown in Table 2, the effect of sodium aluminate in removing silicon is significantly better than that of magnesium oxide. When the pH is controlled at 7-9, the removal rate of sodium aluminate for silicon dioxide is high, and the silicon content of the effluent is 5 mg / L; when the pH is controlled at 9-11, the removal rate of magnesium oxide for silicon dioxide is low, and the effluent is 50 mg / L. Therefore, sodium aluminate is more effective as a silicon removal agent.

[0080] Moreover, the flocculants of this embodiment are preferably polyaluminium chloride and polyacrylamide, and they are added in order, because the flocs formed by polyaluminium chloride are usually small and loose, while the molecular chain of polyacrylamide carries a large number of active groups, which can connect the initially condensed tiny flocs to form larger and tighter flocs, have good sedimentation properties, and achieve solid-liquid separation. Specifically, the dosage of polyaluminium chloride is preferably 5-100mg / L. If the dosage is less than 5mg / L, there is a possibility that the colloid is not completely destabilized, and the flocs are not fully formed; if the dosage exceeds 100mg / L, there is a possibility that the surface of the colloid particles is over-neutralized, and the phenomenon of "re-stabilization" occurs, which is not conducive to subsequent treatment. Furthermore, the dosage of polyacrylamide is preferably 1-5 mg / L. When the dosage is lower than 1 mg / L, the bridging effect is not obvious and the flocs cannot be effectively enlarged. When the dosage is higher than 5 mg / L, the flocs may be too large and loose, which may be easily broken during the sedimentation process, affecting the sedimentation effect, and may also increase the viscosity of the effluent, bringing new treatment problems.

[0081] In some of the embodiments, the precision filtration method is any one of a sand filtration ultrafiltration combination, a sand filtration microfiltration combination, a self-cleaning filtration ultrafiltration combination, a self-cleaning filtration microfiltration combination, tubular ultrafiltration, tubular microfiltration, submerged ultrafiltration or MCR microfiltration; and the material of the ultrafiltration membrane or microfiltration membrane is any one of ceramic, PP, PVDF or PTFE.

[0082] It should be noted that in the prior art, a combination of sand filtration and ultrafiltration is usually used for filtration pretreatment, and a reverse osmosis membrane or a nanofiltration membrane is used for material separation. However, the water quality of the nanofiltration product is relatively poor. If it is directly reused for production, it is easy to interfere with the production process. Therefore, in this embodiment, reverse osmosis is used to separate the materials after filtration pretreatment. Among them, the filtration pretreatment process is preferably any one of a sand filtration ultrafiltration combination, a sand filtration microfiltration combination, a self-cleaning filtration ultrafiltration combination, a self-cleaning filtration microfiltration combination, a tubular ultrafiltration, a tubular microfiltration, an immersion ultrafiltration or an MCR microfiltration. Among them, sand filtration is combined with ultrafiltration or microfiltration to remove larger particles of suspended matter and other impurities in the water, and further intercept smaller colloids, bacteria and other substances through ultrafiltration or microfiltration to achieve graded filtration and improve the overall filtration effect and water quality; self-cleaning filtration equipment is combined with ultrafiltration or microfiltration to ensure the continuous and stable operation of the filtration process, provide good water inlet conditions for ultrafiltration or microfiltration, and improve the stability of the produced water quality; tubular ultrafiltration or microfiltration can maintain a higher flux when filtering wastewater to ensure filtration efficiency; MCR microfiltration can be placed in a sedimentation tank to separate suspended matter and reduce floor space.

[0083] It should also be noted that the material of the ultrafiltration membrane or microfiltration membrane in this embodiment is preferably any one of ceramic, PP, PVDF or PTFE, among which the ceramic membrane has good chemical stability and high mechanical strength, and can ensure the stability of the filtration effect during filtration; the PP membrane has a certain hydrophilicity, which can effectively improve the flux and filtration efficiency of the membrane and reduce the occurrence of membrane pollution; the PVDF membrane has good anti-pollution properties and can maintain stable operation for a long time; the PTFE membrane has high mechanical strength and good wear resistance, and can remain relatively stable even after long-term operation, ensuring the consistency and reliability of the filtration accuracy.

[0084] S200, using a reverse osmosis process to separate materials from the filtrate after precision filtration, and adding a reagent to the obtained reverse osmosis concentrated water for magnesium and calcium removal, and then filtering to remove suspended matter and evaporating and crystallizing to obtain sodium sulfate crystal salt;

[0085] In this step, the filtrate obtained by the precision filtration in step S100 is subjected to material separation by a reverse osmosis process to obtain reverse osmosis concentrated water and reverse osmosis produced water. The reverse osmosis concentrated water is treated with reagents in order to remove hardness, remove calcium ions and magnesium ions, and remove the remaining suspended matter and colloids after filtration to obtain concentrated brine, which is then evaporated and crystallized to produce sodium sulfate crystal salt. That is, while treating the wastewater, the output of the byproduct sodium sulfate crystal salt is increased, thereby improving resource utilization.

[0086] In some embodiments, the hardness-removing agents added to the reverse osmosis concentrated water are sodium hydroxide, sodium carbonate, polyaluminium chloride, polyacrylamide and sulfuric acid in sequence; and

[0087] The pH of the reverse osmosis concentrated water after the addition of sodium hydroxide is 11-12;

[0088] The dosage of sodium carbonate is 0-3000mg / L;

[0089] The dosage of polyaluminium chloride is 5-100mg / L;

[0090] The dosage of polyacrylamide is 1-5 mg / L;

[0091] The pH of the reverse osmosis concentrated water after the addition of sulfuric acid is 7-8.

[0092] In this embodiment, in order to achieve the purpose of removing hardness from reverse osmosis concentrated water, the reagents are added in the order of alkali, hardness removal agent, flocculant and acid. Specifically, the reagent combination is preferably sodium hydroxide, sodium carbonate, polyaluminium chloride, polyacrylamide and sulfuric acid. Among them, for the reverse osmosis concentrated water in this embodiment, the optimal reaction pH is 11-12, so this embodiment adds sodium hydroxide so that the inlet pH can be adjusted from 7-8 to 11-12, and then sodium carbonate is added to the reaction tank, and the addition amount is 0-3000mg / L, and the reaction time is 30-60min, to ensure that carbonate ions can fully react with calcium ions in the water and reduce the hardness of the water. Not only that, polyaluminium oxide and polyacrylamide are added in sequence, so that the fine precipitation particles can be condensed into flocs, and the flocs are connected into tighter flocs, which strengthens the coagulation effect and facilitates subsequent precipitation and separation. It should also be noted that after the hardness removal is completed, the pH of the effluent is 11-12, which is strongly alkaline, does not meet the requirements of the subsequent treatment process, and cannot be directly discharged. Therefore, sulfuric acid is used in this embodiment to adjust the pH to 7-8, making it neutral or weakly alkaline, so that the water quality is more suitable for subsequent treatment and discharge, and avoids adverse effects on the equipment. In addition, after silicon removal and concentrated water hardness removal, the subsequent crystallized salt has a higher purity.

[0093] S300, desalting the reverse osmosis produced water to obtain qualified discharge water and recycled water.

[0094] This step is to desalinate the reverse osmosis water obtained after the material separation in step S200, so that it can produce recycled water and qualified discharge water, wherein the recycled water can be reused in the production process, reducing the use of tap water, improving the recycling rate of water resources, and reducing water use costs; the obtained discharge water can meet the discharge standards and can be directly discharged, reducing sewage discharge costs.

[0095] In some of the embodiments, when the reverse osmosis produced water is desalinated to obtain qualified discharge water and recycled water, the reverse osmosis process is used again to desalinate the reverse osmosis produced water, and the qualified discharge water has a TDS ≤ 5000 mg / L and a pH of 7-9, and the recycled water has a TDS ≤ 200 mg / L, sodium sulfate ≤ 30 mg / L, and a pH of 7-8.

[0096] In this embodiment, the reverse osmosis process is specifically used to desalinate the reverse osmosis water obtained in step S200, and the pollutants such as salt in the water are separated, so that the discharged water meets the specified water quality standards, that is, TDS ≤ 5000 mg / L, pH 7-9, and reduces the risk of pollution to the ecological environment such as soil and water. At the same time, recycled water can also be obtained for reuse as production water, saving costs.

[0097] In some embodiments, it also includes:

[0098] The precipitate after sedimentation treatment, the silicon-containing sludge after silicon removal and the chemical sludge after concentrated water demagnesium and decalcification are all subjected to sludge concentration and filter pressing. The obtained mud cake is outsourced for disposal, and the filtered filtrate is refluxed for sedimentation again.

[0099] In this embodiment, the precipitate after sedimentation treatment in the sedimentation tank, the silicon-containing sludge obtained after silicon removal treatment, and the chemical sludge after reverse osmosis concentrated water demagnesization and decalcification are all subjected to sludge treatment, that is, sludge concentration and filter pressing are performed in sequence, so that a mud cake with a water content of 60% can be obtained for outsourced disposal, and the filtered filtrate is returned to the sedimentation tank for further sedimentation. The sedimentation tank can use its own volume to adjust the silica gel wastewater and the reflux water to make them evenly mixed, so that suspended matter, silica and colloids can be precipitated after adding drugs.

[0100] It can be seen from this that after the silica gel production wastewater is settled, only sodium hydroxide is used to adjust the pH during silicon removal, which is not only not easy to produce a large amount of additional sludge, but also ensures that the sulfate ions in the wastewater are not consumed, and the sodium ions provided can also increase the content of the final byproduct sodium sulfate crystal salt. Not only that, the present application also performs precision filtration on the produced water after silicon removal, and uses the reverse osmosis treatment of the filtered filtrate, and the reverse osmosis concentrated water is subjected to hardness removal treatment, so that the filtered concentrated brine can be evaporated and crystallized, and after silicon removal and hardness removal treatment, the obtained byproduct sodium sulfate crystal salt has a higher purity. At the same time, the reverse osmosis produced water is also subjected to desalination treatment, so as to obtain the discharge water that meets the standards and is directly discharged, reducing the cost of sewage discharge, and at the same time, it is also possible to obtain recycled water for reuse in production according to actual conditions, reducing the water consumption of tap water during silica gel production.

[0101] like Figure 2 As shown, in a second aspect, an embodiment of the present application provides a silica gel production wastewater treatment system, which is used to implement any of the above-mentioned silica gel production wastewater treatment processes, including:

[0102] The pretreatment unit 100 includes a sedimentation tank 110, a silicon removal system 120, a silicon removal water production tank 130 and a precision filtration system 140 which are connected in sequence;

[0103] The concentration and crystallization unit 200 includes a filtrate pool 210, a material separation system 220, a concentrated water hardness removal system 230, a concentrated water filtration system 240, a concentrated brine pool 250 and an evaporation and crystallization system 260 which are sequentially connected and arranged, and the filtrate pool 210 is connected and arranged with the precision filtration system 140;

[0104] The desalination unit 300 includes a water production pool 310 , a desalination system 320 and a water recycling pool 330 which are connected in sequence, and the water production pool 310 is connected to the material separation system 220 .

[0105] In this embodiment, the pretreatment unit 100 is used to sequentially perform sedimentation, desiliconization treatment and precision filtration on the original silica gel production wastewater, wherein the sedimentation tank 110 in the pretreatment unit 100 can remove naturally settled particulate matter, such as silica gel particles, the desiliconization system 120 can remove suspended matter, silica, a part of hardness and colloids that can be settled after adding drugs, and the precision filtration system 140 can remove the remaining suspended matter, bacteria and colloids, etc., so as to obtain the filtered filtrate. Among them, in order to ensure the particle removal effect of the sedimentation tank 110, a circular vertical flow sedimentation tank 110 is preferably used, and the bottom is an inverted cone, so that large particles can be concentrated at the bottom and are not easy to float with the water flow. The desiliconization system 120 is preferably a desiliconization sedimentation tank, and sodium hydroxide, sodium aluminate, polyaluminum chloride and polyacrylamide are added to the sedimentation tank in order during the desiliconization treatment, so that the silicon content of the produced water meets the requirement of 5 mg / L.

[0106] Further, the concentration crystallization unit 200 receives the filtrate filtered by the precision filtration system 140, stores it in the filtrate pool 210, and performs reverse osmosis treatment on the produced water of the precision filtration system 140 through the material analysis system connected to the filtrate pool 210, produces reverse osmosis concentrated water and reverse osmosis produced water, and removes calcium ions and magnesium ions from the reverse osmosis concentrated water through the concentrated water hardness removal system 230, removes the remaining suspended matter and colloids through the concentrated water filtration system 240, and finally produces concentrated brine stored in the concentrated brine pool 250, and uses the evaporation crystallization system 260 connected to the concentrated brine pool 250 for evaporation and crystallization to produce sodium sulfate crystal salt. Among them, the concentrated water hardness removal system 230 is preferably a hardness removal sedimentation tank, and sodium hydroxide, sodium carbonate, polyaluminum chloride, polyacrylamide and sulfuric acid are added to the sedimentation tank in sequence during hardness removal, so as to achieve the purpose of removing hardness from the wastewater. It should be noted that the desiliconization and dehardening functions of the desiliconization system 120 and the concentrated water dehardening system 230 effectively solve the scaling and clogging problems of the membrane and evaporation crystallization, greatly extend the service life of the equipment, reduce processing costs, and can also effectively improve the purity of the crystallized salt.

[0107] Finally, the reverse osmosis produced water is desalted by the desalination unit 300, and the reverse osmosis produced water after the concentration and crystallization unit 200 is stored in the produced water pool, and the desalination system 320 connected to the produced water pool is used to separate the salt again by the reverse osmosis process, and the final produced recycled water is stored in the recycled water pool 330, and is reused for production according to actual needs, reducing the amount of tap water. At the same time, the produced qualified discharge water is directly discharged to reduce the sewage discharge cost.

[0108] In some embodiments, the pre-processing unit 100 further includes:

[0109] The wastewater collection tank 150 has a liquid inlet connected to the backwash water outlet of the precision filtration system 140, and a liquid outlet connected to the wastewater liquid inlet of the sedimentation tank 110;

[0110] The sludge treatment system 160 has a sludge feed end connected to the sludge discharge ends corresponding to the sedimentation tank 110, the silicon removal system 120 and the concentrated water hardness removal system 230, and a filtrate end connected to the liquid inlet end of the sedimentation tank 110, and the sludge treatment system 160 includes a sludge thickening tank and a plate and frame filter press connected in sequence.

[0111] In this embodiment, the backwash water of the precision filtration system 140 is collected in the wastewater collection tank 150 and then sent to the sedimentation tank 110. At the same time, the sludge treatment system 160 is used to receive the precipitate produced by the sedimentation tank 110, the sludge produced by the silicon removal system 120, and the sludge produced by the concentrated water hardness removal system 230. After treatment, the mud cake is discharged, and the filtrate filtered by the sludge treatment system 160 is returned to the sedimentation tank 110, and the original silica gel production wastewater is mixed with the volume of the sedimentation tank 110, and the sedimentation treatment is performed again to improve the utilization rate of water resources. It should also be noted that the precipitate produced by the sedimentation tank 110, the sludge produced by the silicon removal system 120, and the sludge produced by the concentrated water hardness removal system 230 are concentrated and filtered in turn by using the sludge concentration tank and the plate and frame filter press, so that the mud cake with a water content of 60% can be produced for outsourcing. In this way, the water content in the sludge is reduced, the mud cake is formed, and the risk of the spread of harmful substances is reduced.

[0112] In some of the embodiments, the sedimentation tank 110 includes a tank body 111, a central tube 112, an inlet pipe 113, a reflector 114, a baffle 115, an outlet pipe and a mud discharge pipe 116; the bottom of the tank body 111 is an inverted cone structure; the central tube 112 is vertically arranged inside the tank body 111; the inlet pipe 113 is arranged from one side of the tank body 111 in a direction perpendicular to the central tube 112, and is connected to the central tube 112; the reflector 114 is circumferentially arranged at the bottom of the central tube 112; the baffle 115 is circumferentially arranged on the inner side of the top of the tank body 111, and a water collecting trough is formed between the baffle 115 and the tank body 111, and the water collecting trough is connected to the outlet pipe; the mud discharge pipe 116 is arranged from top to bottom along the inner wall of the tank body 111.

[0113] like Figure 3As shown, in this embodiment, a central pipe 112 is vertically arranged inside the tank body 111 of the sedimentation tank 110, and a water inlet pipe 113 extends from one side of the outside of the tank body 111 to the inside of the central pipe 112, and a reflector 114 is arranged at the bottom of the central pipe 112. When the wastewater flows into the central pipe 112 from the water inlet pipe 113, it flows downward along the central pipe 112 and flows out from the lower part of the central pipe 112. After being blocked by the reflector 114, it is evenly distributed around and flows upward to the water collection tank formed between the baffle 115 and the tank body 111, and finally discharged from the tank body 111 along the outlet pipe. It should be noted that the direction of particle precipitation in the wastewater is opposite to the rising direction of the water flow, that is, the sludge in the wastewater settles to the bottom of the tank body 111, and is discharged from the tank body 111 along the sludge outlet on the sludge discharge pipe 116 under the action of hydrostatic pressure. It should be noted that the bottom of the pool body 111 of this embodiment is an inverted cone structure, which can better ensure the removal effect of large particles. Compared with the flat-bottomed sedimentation tank, it can not only guide the dispersed particles to one place, but also effectively prevent the particles that have settled to the bottom of the pool from being suspended in the water again due to water flow disturbance, so that they are in a relatively stable state, thereby ensuring the particle removal effect.

[0114] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0115] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "one", "the" and the like involved in this application do not indicate a quantitative limitation and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more, and "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. The terms "first", "second", "third" and the like involved in this application are merely to distinguish similar objects and do not represent a specific ordering of objects.

[0116] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but the limitation of the scope of the invention patent cannot be understood as a result. It should be pointed out that, for a person of ordinary skill in the art, several variations or improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A silica gel production wastewater treatment process, characterized in that: The steps include: After the silica gel production wastewater is settled, a reagent is added to the supernatant to remove silicon, and the produced water after silicon removal is precisely filtered; during silicon removal, sodium hydroxide is used to adjust the pH of the silica gel production wastewater; The filtrate after precision filtration is subjected to material separation by reverse osmosis process, and the obtained concentrated water is treated with reagents for magnesium and calcium removal, and then filtered to remove suspended matter and evaporated for crystallization to obtain sodium sulfate crystal salt; The reverse osmosis produced water is desalinated to obtain qualified discharge water and recycled water.

2. The silica gel production wastewater treatment process according to claim 1, characterized in that: After the silica gel production wastewater is subjected to sedimentation treatment, a reagent is added to the supernatant to remove silicon, and the produced water after silicon removal is finely filtered, including: Sedimentation treatment of silica gel production wastewater to remove particulate matter; Add reagents in sequence to the supernatant obtained after sedimentation treatment to remove silicon dioxide and part of suspended solids, hardness and colloids; wherein, sodium hydroxide is used to adjust the pH of silica gel production wastewater to 7-8 during silicon removal; The produced water after the addition of the agent is precisely filtered to remove bacteria and remaining suspended matter and colloids, and the backwash water after the precise filtration is returned to the sedimentation tank for further sedimentation.

3. The silica gel production wastewater treatment process according to claim 2, characterized in that: The reagents added to the supernatant are sodium aluminate, polyaluminium chloride and polyacrylamide in sequence; and The dosage of the sodium aluminate is at least 1.5-2.5 times the mass of the silicon dioxide contained in the supernatant after sedimentation, and the reaction time of the sodium aluminate is 30-60 minutes; The dosage of the polyaluminium chloride is 5-100 mg / L; The dosage of the polyacrylamide is 1-5 mg / L.

4. The silica gel production wastewater treatment process according to claim 2, characterized in that: The precision filtration method is any one of sand filtration ultrafiltration combination, sand filtration microfiltration combination, self-cleaning filtration ultrafiltration combination, self-cleaning filtration microfiltration combination, tubular ultrafiltration, tubular microfiltration, immersion ultrafiltration or MCR microfiltration; and the material of the ultrafiltration membrane or microfiltration membrane is any one of ceramic, PP, PVDF or PTFE.

5. The silica gel production wastewater treatment process according to claim 1, characterized in that: The hardness-removing agents added to the reverse osmosis concentrated water are sodium hydroxide, sodium carbonate, polyaluminium chloride, polyacrylamide and sulfuric acid in sequence; and The pH of the reverse osmosis concentrated water after the addition of sodium hydroxide is 11-12; The dosage of the sodium carbonate is 0-3000 mg / L; The dosage of the polyaluminium chloride is 5-100 mg / L; The dosage of the polyacrylamide is 1-5 mg / L; The pH of the reverse osmosis concentrated water after the addition of sulfuric acid is 7-8.

6. The silica gel production wastewater treatment process according to claim 1, characterized in that: When the reverse osmosis produced water is desalinated to obtain qualified discharge water and recycled water, the reverse osmosis process is used again to desalinate the reverse osmosis produced water, and the TDS of the qualified discharge water is ≤5000mg / L, the pH is 7-9, and the TDS of the recycled water is ≤200mg / L, the sodium sulfate is ≤30mg / L, and the pH is 7-8.

7. The silica gel production wastewater treatment process according to any one of claims 1 to 6, characterized in that: Also includes: The precipitate after sedimentation treatment, the silicon-containing sludge after silicon removal and the chemical sludge after concentrated water demagnesium and decalcification are all subjected to sludge concentration and filter pressing. The obtained mud cake is outsourced for disposal, and the filtered filtrate is refluxed for sedimentation again.

8. A silica gel production wastewater treatment system, used to implement the silica gel production wastewater treatment process according to any one of claims 1 to 7, characterized in that: include: The pretreatment unit includes a sedimentation tank, a silicon removal system, a silicon removal water production tank and a precision filtration system which are connected in sequence; The concentration and crystallization unit comprises a filtrate pool, a material separation system, a concentrated water hardness removal system, a concentrated water filtration system, a concentrated brine pool and an evaporation and crystallization system which are sequentially connected and arranged, and the filtrate pool is connected and arranged with the precision filtration system; The desalination unit comprises a water production pool, a desalination system and a water recycling pool which are connected in sequence, and the water production pool is connected with the material separation system.

9. The silica gel production wastewater treatment system according to claim 8, characterized in that: The pre-processing unit further includes: A wastewater collection tank, wherein the liquid inlet end is connected to the backwash water outlet end of the precision filtration system, and the liquid outlet end is connected to the wastewater liquid inlet end of the sedimentation tank; The sludge treatment system has a sludge feed end which is respectively connected to the sludge discharge ends corresponding to the sedimentation tank, the silicon removal system and the concentrated water hardness removal system, and a filtrate end which is connected to the liquid inlet end of the sedimentation tank, and the sludge treatment system includes a sludge thickening tank and a plate and frame filter press which are connected in sequence.

10. The silica gel production wastewater treatment system according to claim 8, characterized in that: The sedimentation tank comprises a tank body, a central pipe, a water inlet pipe, a reflector, a baffle, a water outlet pipe and a mud discharge pipe; The bottom of the pool body is an inverted cone structure; The central tube is vertically arranged inside the tank body; The water inlet pipe is arranged from one side of the pool body in a direction perpendicular to the central pipe and is connected to the central pipe; The reflecting plate is circumferentially arranged at the bottom of the central tube; The baffle is circumferentially arranged on the inner side of the top of the pool body, and a water collecting trough is formed between the baffle and the pool body, and the water collecting trough is connected to the water outlet pipe; The mud discharge pipe is arranged from top to bottom along the inner wall of the pool body.

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