Treatment system and treatment method for removing hardness, fluorine and silicon from high-salinity wastewater

Abstract

The present application relates to the field of water treatment process, disclose a kind of high-salinity wastewater hardness removal fluorine removal silicon processing system and processing method.The processing system includes: sequentially communicating first reaction precipitation unit, second reaction precipitation unit and optional depth fluorine removal unit.The processing method includes the following steps:(1) high-salinity wastewater is mixed with Ca (OH) 2Powder or high-concentration slurry for the first time, and the product is separated to obtain the first supernatant;(2) the first supernatant is mixed with Na2CO3Solution for the second time, and the product is separated to obtain the second supernatant;(3) optionally, the second supernatant is depth fluorine removal, and the product is obtained after processing water.The processing system and processing method not only can effectively remove calcium, magnesium, silicon and fluoride ions in high-salinity wastewater, ion removal rate is high, and can save the amount of reagent, save reaction time and equipment and the input of operation.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a treatment system and method for dehardening, defluorinating, and desiliconizing high-salinity wastewater. Background Technology

[0002] In recent years, with the rapid development of industry, most wastewater reuse technologies have become mature and stable, achieving wastewater reduction. However, the volume of complex wastewater, such as reverse osmosis concentrate after membrane concentration, is increasing year by year, generally exhibiting high salt content, high hardness, and complex components including silicon, fluoride, and organic matter. High-salt wastewater, such as the mother liquor from the crystallizer at the end of water treatment processes and the reverse osmosis concentrate from membrane concentration, has high hardness, silicon, and fluoride ion content. If these are not efficiently removed, it will not only affect the water recovery rate of the entire water system but also damage downstream equipment, impacting the overall economic stability of the process. Therefore, there is an urgent need for a treatment system and method that can effectively remove scale-forming ions such as calcium, magnesium, silicon, and fluoride ions from high-salt wastewater.

[0003] CN110606612A discloses a resource-based treatment process for high-salinity wastewater from coal coking. This process employs pretreatment + nanofiltration desalination + reverse osmosis concentration + advanced oxidation + evaporation crystallization to achieve zero discharge and differentiated resource utilization of high-salinity wastewater from coal coking. The pretreatment process includes defluorination, desiliconization, and hardness reduction. This patent removes fluoride through two-stage coagulation and sedimentation by adding calcium chloride, ferric chloride, PAM, and a special defluorination agent; removes silicon by adding sodium hydroxide, magnesium chloride, and PAM; and reduces hardness by adding soda ash and ferric chloride. The defluorination, desiliconization, and hardness reduction processes involve a total of four chemical coagulation and sedimentation steps. This invention requires four stages of chemical coagulation and sedimentation, with some flocculation retention times being relatively long. The pretreatment process involves numerous equipment and a large footprint. Furthermore, the addition of calcium chloride for defluorination forms calcium fluoride precipitate, which significantly affects the ionic strength of other components under high-concentration brine conditions, making the reliance solely on calcium ions for fluoride removal somewhat limited.

[0004] CN109734216A discloses a treatment system and process for removing hardness, silica, and turbidity from high-salinity wastewater. This patented process system includes an integrated reactor and a membrane separation unit. In the reactor, the wastewater reacts with reagents to generate different types of sludge particles, including but not limited to calcium carbonate, magnesium hydroxide, and silicate sludge particles. The sludge particle mixture enters the membrane tank, where it is aerated to achieve a uniform concentration. The membrane separation unit utilizes the principle of sieving and filtration to directly trap the sludge particles in the mixture on the outside of the membrane fibers. The treated water is recycled, and the sludge particles are discharged from the membrane separation unit. In the same reactor, Ca... 2+ The removal of ions and SiO2 are mutually influential processes, making it difficult to achieve optimal treatment results simultaneously. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of repeated use of reagents, large equipment investment, high operating costs, and the inability to achieve optimal results simultaneously due to mutual interference of ion precipitation in the existing high-salt wastewater treatment process. This invention provides a treatment system and method for reducing hardness, removing fluoride, and removing silicon from high-salt wastewater. This treatment system and method can save on reagent dosage, reaction time, equipment, and operating costs, and effectively remove calcium, magnesium, silicon, fluoride, and other ions from high-salt wastewater.

[0006] To achieve the above objectives, a first aspect of the present invention provides a treatment system for dehardening, desiliconizing, and defluorinating high-salinity wastewater, comprising: a primary reaction precipitation unit, a secondary reaction precipitation unit, and an optional deep defluorination unit connected in sequence; wherein,

[0007] The primary reaction precipitation unit includes a first dosing device, which is used to dosing Ca(OH)2 powder or Ca(OH)2 high-concentration slurry.

[0008] The primary reaction precipitation unit is used to simultaneously precipitate magnesium, silicon and primary fluoride in high-salt wastewater.

[0009] The secondary reaction precipitation unit is used to simultaneously perform calcium precipitation and secondary fluoride precipitation on the effluent from the primary reaction precipitation unit.

[0010] A second aspect of this invention provides a method for treating high-salinity wastewater by reducing hardness, removing silicon, and removing fluoride, comprising the following steps:

[0011] (1) The high-salt wastewater is mixed with the first reagent, and the resulting suspension is contacted with the coagulant aid and flocculant. The resulting product is then separated to obtain the first supernatant. The first reagent is Ca(OH)2 powder or Ca(OH)2 high-concentration slurry.

[0012] (2) The first supernatant is mixed with Na2CO3 solution for a second time, and the resulting suspension is contacted with coagulant aid and flocculant for a second time. Then the resulting product is separated to obtain the second supernatant.

[0013] (3) Optionally, the second supernatant is subjected to deep defluorination to obtain treated product water.

[0014] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0015] (1) Using Mg 2+ Ca 2+ Si, F - The removal reaction characteristics enable synergistic and stepwise removal; for example, synergistic removal of Si and F are achieved. - The stepwise removal process saves reaction time, equipment, and operational costs.

[0016] (2) The method of adding the drug was optimized, the amount of drug used was saved, and the reaction effect was increased.

[0017] (3) F was developed - Deep removal process and treatment system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a high-salinity wastewater hardening, silicon removal, and fluoride removal treatment system provided by the present invention.

[0019] Explanation of reference numerals in the attached figures

[0020] Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] In this invention, the terms "first", "second", "third", "fourth" and "fifth" do not limit the invention, but are only used to distinguish different dosing devices.

[0023] The first aspect of this invention provides a treatment system for dehardening, desiliconizing, and defluorinating high-salinity wastewater, as shown in the schematic diagram below. Figure 1 As shown, the processing system includes: a primary reaction precipitation unit I, a secondary reaction precipitation unit II, and an optional deep defluorination unit III, connected in sequence; wherein,

[0024] The primary reaction precipitation unit I includes a first dosing device 6, which is used to dosing Ca(OH)2 powder or Ca(OH)2 high-concentration slurry.

[0025] The primary reaction precipitation unit I is used to simultaneously precipitate magnesium, silicon and primary fluoride in high-salt wastewater.

[0026] The secondary reaction precipitation unit II is used to simultaneously perform calcium precipitation and secondary fluoride precipitation on the effluent from the primary reaction precipitation unit.

[0027] In some embodiments of the present invention, the primary reaction sedimentation unit I further includes: a primary mixing reaction tank 1, a primary coagulation tank 2, a primary flocculation tank 3, a primary sedimentation tank 4, and a primary inclined tube clarification tank 5.

[0028] In some embodiments of the present invention, the primary mixing reaction tank 1, the primary coagulation tank 2, and the primary flocculation tank 3 are all equipped with dosing ports; wherein, the dosing port of the primary mixing reaction tank 1 is connected to a first dosing device 6, the dosing port of the primary coagulation tank 2 is connected to a third dosing device 8, and the dosing port of the primary flocculation tank 3 is connected to a fourth dosing device 9. The first dosing device 6 is used for dosing Ca(OH)2 powder or high-concentration Ca(OH)2 slurry, the third dosing device 8 is used for dosing coagulant aids, and the fourth dosing device 9 is used for dosing flocculants.

[0029] In some embodiments of the present invention, the primary reaction precipitation unit I further includes an optional dosing device for dosing MgO or MgCl2.

[0030] In some embodiments of the present invention, a pH meter is provided in the primary coagulation tank 1 in order to control the pH value of the suspension.

[0031] In some embodiments of the present invention, the primary mixing reaction tank 1, the primary coagulation tank 2, the primary flocculation tank 3, and the primary sedimentation tank 4 are all equipped with stirring devices, and the primary inclined tube clarification tank 5 is equipped with a sewage outlet.

[0032] In some embodiments of the present invention, the secondary reaction sedimentation unit includes a secondary mixing reaction tank 11, a secondary coagulation tank 12, a secondary flocculation tank 13, a secondary sedimentation tank 14, and a secondary inclined tube clarifier 15.

[0033] In some embodiments of the present invention, the secondary mixing reaction tank 11, the secondary coagulation tank 12, and the secondary flocculation tank 13 are all provided with dosing ports; wherein, the dosing port of the secondary mixing reaction tank 11 is connected to the second dosing device 7; the dosing port of the secondary coagulation tank 12 is connected to the third dosing device 8; and the dosing port of the secondary flocculation tank 13 is connected to the fourth dosing device 9. The first dosing device 7 is used for dosing Na2CO3 solution, the third dosing device 8 is used for dosing coagulant aid, and the fourth dosing device 9 is used for dosing flocculant.

[0034] In some embodiments of the present invention, the secondary mixing reaction tank 11, the secondary coagulation tank 12, the secondary flocculation tank 13, and the secondary sedimentation tank 14 are all equipped with stirring devices, and the secondary inclined tube clarification tank 15 is equipped with a sewage outlet.

[0035] In some embodiments of the present invention, the deep defluorination unit III includes: a jet mixer 16, a dosing mixer 17, a cyclone reactor 18, and a micro-sand sedimentation tank 19 connected in sequence.

[0036] In some embodiments of the present invention, the dosing mixer 17 is provided with two dosing ports, which are respectively connected to the fourth dosing device 9 and the fifth dosing device 10. The fourth dosing device 9 is used to add flocculant, and the fifth dosing device 10 is used to add defluorination agent.

[0037] In some embodiments of the present invention, the cyclone reactor 18 is provided with a central tube, and a spiral structure is arranged inside the central tube. The cyclone reactor 18 is used to promote faster floc aggregation and accelerate the settling speed. Specifically, the incoming water, after being mixed by the dosing mixer 17, enters the cyclone reactor 18 tangentially and settles in a spiral manner inside the reactor. This extends the residence time of the incoming water in a limited space, promotes faster floc aggregation, and allows it to combine with micro-sand for rapid settling. The settled incoming water and flocs that have not reached the settling density rise along the central tube inside the cyclone reactor 18. As the micro-flocs rise along the spiral, they collide with the spiral blades and are then deflected back or adsorbed onto the outer wall of the spiral blades. The treated clean water rises to the top space of the cyclone reactor 18.

[0038] In some embodiments of the present invention, the micro-sand settling tank 19 is provided with a drain outlet. Sludge settled by the cyclone reactor 18 is discharged to the micro-sand settling tank 19. The lighter sludge (containing no micro-sand) in the upper part of the micro-sand settling tank 19 is discharged through the drain outlet, while the denser sludge (containing micro-sand) in the lower part is recycled to the jet mixer 16. A Venturi jet mixer is used for the recycling and reuse of micro-sand and sludge.

[0039] A second aspect of this invention provides a method for treating high-salinity wastewater by reducing hardness, removing silicon, and removing fluoride, comprising the following steps:

[0040] (1) The high-salt wastewater is mixed with the first reagent in the first mixing, and the resulting suspension is contacted with the coagulant aid and flocculant in the first contact. Then the resulting product is separated in the first separation to obtain the supernatant. The first reagent is Ca(OH)2 powder or Ca(OH)2 high-concentration slurry.

[0041] (2) The first supernatant is mixed with Na2CO3 solution for a second time, and the resulting suspension is contacted with coagulant aid and flocculant for a second time. Then the resulting product is separated to obtain the second supernatant.

[0042] (3) Optionally, the second supernatant is subjected to deep defluorination to obtain treated product water.

[0043] In this invention, the terms "first" and "second" do not limit the invention, but are only used to distinguish materials and operations performed at different stages.

[0044] In some embodiments of the present invention, the method for treating high-salinity wastewater by reducing hardness, removing silicon, and removing fluoride is implemented in the high-salinity wastewater treatment system for reducing hardness, removing silicon, and removing fluoride described in the first aspect above.

[0045] The inventors of this invention discovered during their research that by utilizing Mg 2+ Ca 2+ Si, F - The removal characteristics of this reaction target the simultaneous removal of a certain amount of other ions while removing a specific type of ion, i.e., the removal of Mg. 2+ The reaction steps synergistically remove Si and F - Remove Ca 2+ The reaction steps synergistically remove F - Difficult ions such as F - Achieving gradual, phased removal can save on reaction time, equipment, and operational costs.

[0046] In some embodiments of the present invention, in order to simultaneously perform magnesium precipitation, silicon precipitation and primary fluoride precipitation on high-salt wastewater, the high-salt wastewater is first mixed with a first reagent, the resulting suspension is first contacted with a coagulant aid and a flocculant, and then the resulting product is separated to obtain a first supernatant; the first reagent is Ca(OH)2 powder or Ca(OH)2 high-concentration slurry.

[0047] In some embodiments of the present invention, step (1) is carried out in the primary reaction sedimentation unit. Specifically, after high-salt wastewater enters the primary mixing reaction tank 1 and is mixed with Ca(OH)2 powder or high-concentration Ca(OH)2 slurry, the effluent enters the primary coagulation tank 2, and after contacting with the coagulant aid, the effluent enters the primary flocculation tank 3, and after contacting with the flocculant, the effluent sequentially enters the primary sedimentation tank 4 and the primary inclined tube clarifier 5. The effluent from the primary inclined tube clarifier 5 is recorded as the first supernatant.

[0048] The inventors of this invention discovered during their research that the following reaction occurs when high-salt wastewater is first mixed with Ca(OH)2 powder or a high-concentration Ca(OH)2 slurry:

[0049] (1) Magnesium precipitation: Under alkaline conditions, Mg in high-salinity wastewater precipitates. 2+ With the OH in the added Ca(OH)2 - The reaction produces Mg(OH)2 precipitate;

[0050] (2) Silicon precipitation: Under alkaline conditions, silica compounds react with Ca... 2+ Mg 2+ It will form insoluble silicates, and at the same time, silica compounds are adsorbed on the surface of Mg(OH)2 precipitate particles to form insoluble magnesium silicate. In addition, to some extent, silica colloids coagulate and calcium silicate is also formed.

[0051] (3) Primary fluoride precipitation: Ca in the added Ca(OH)2 2+With F in high-salinity wastewater - The reaction produces CaF2 precipitate, thereby reducing the F in high-salinity wastewater. - content.

[0052] The inventors of this invention discovered during their research that optimizing the method of reagent addition can improve the reaction effect. In this invention, by adding Ca(OH)₂ powder or a high-concentration Ca(OH)₂ slurry instead of Ca(OH)₂ solution, the unreacted Ca(OH)₂ powder particles provide aggregates during the reaction, accelerating the settling speed, and forming complexes with Mg(OH)₂ precipitate, SiO₂, and CaF₂, thus enhancing the settling effect. A large amount of sludge precipitate generated in the primary reaction sedimentation tank is recycled, with a sludge recycling rate of 20%-50%, which easily forms large alum flocs. Simultaneously, it facilitates the redissolution of undissolved calcium hydroxide, and the unreacted Ca(OH)₂ is reused, saving reagent dosage.

[0053] In some embodiments of the present invention, the amount of Ca(OH)2 powder or high-concentration Ca(OH)2 slurry added should be such that the pH value of the mixed suspension is 11-14, preferably 11-12.

[0054] In some embodiments of the present invention, in order to ensure that the reaction between high-salt wastewater and Ca(OH)2 powder or high-concentration Ca(OH)2 slurry is fully carried out, preferably, the conditions for the first mixing include: a stirring speed of 100-150 r / min; and a mixing residence time of 30-60 min.

[0055] In some embodiments of the present invention, in order to more effectively remove Si from high-salinity wastewater, based on the Mg content in the high-salinity wastewater... 2+ The mass ratio of magnesium to silicon determines whether a magnesium additive, such as MgO or MgCl2, is needed. If the wastewater contains high-salinity Mg... 2+ If the mass ratio of magnesium to silicon is less than 0.8, magnesium needs to be added; otherwise, magnesium does not need to be added.

[0056] In this invention, in order to increase the aggregation degree of suspended solids and the dewatering performance of high-salinity wastewater, the obtained suspension is subjected to a first contact with a coagulant aid and a flocculant. Preferably, the conditions for the first contact include: a stirring speed of 30-50 r / min and a contact residence time of 10-30 min.

[0057] In this invention, in order to further achieve simultaneous calcium precipitation and secondary fluoride precipitation of the effluent from the primary reaction precipitation unit, the first supernatant is mixed with Na2CO3 solution for a second time, and the resulting suspension is contacted with coagulant and flocculant for a second time. Then, the resulting product is separated to obtain the second supernatant.

[0058] In some embodiments of the present invention, step (2) is carried out in the secondary reaction sedimentation unit. Specifically, the effluent from the primary inclined tube clarifier 5 overflows into the secondary mixing reaction tank 11, undergoes a second mixing with the Na2CO3 solution, and then enters the secondary coagulation tank 12. After contacting with the coagulant aid, the effluent enters the secondary flocculation tank 13. After contacting with the flocculant, the effluent sequentially enters the secondary sedimentation tank 14 and the secondary inclined tube clarifier 15. The effluent from the secondary inclined tube clarifier 15 is recorded as the second supernatant.

[0059] The inventors of this invention discovered during their research that the following reaction occurs in the secondary reaction precipitation unit:

[0060] (1) Calcium precipitation: CO3 in Na2CO3 solution 2- With Ca in the first supernatant 2+ The reaction produces CaCO3 precipitate;

[0061] (2) Secondary fluoride precipitation: F in the first supernatant - With Ca 2+ CaF2 precipitate is formed, and it combines with CaCO3 precipitate or flocs and colloids formed by coagulants and flocculants through adsorption, bridging, electrostatic interaction, and complexation to form precipitate, further reducing the F content in the solution. - content.

[0062] In some embodiments of the present invention, in order to ensure that the Na2CO3 solution and the Ca in the first supernatant are in harmony... 2+ For the reaction to proceed fully, preferably, the conditions for the second mixing include: a stirring speed of 100-150 r / min and a mixing residence time of 10-30 min.

[0063] In this invention, in order to fully promote the aggregation of suspended matter in the suspension, preferably, the conditions for the second contact include: a stirring speed of 30-50 r / min and a contact residence time of 10-30 min.

[0064] In this invention, in order to ensure the Ca content in the first supernatant 2+ To be fully reacted and precipitated, preferably in the form of CO3. 2- The calculated Na2CO3 solution and Ca 2+ The mass ratio of the first supernatant was 3-5:1.

[0065] In this invention, for ions that are easily removed, such as Mg 2+ and Ca 2+ A one-step removal method is used; for Si, Mg removal is employed. 2 + Synergistic removal methods, such as those for removing Mg from high-salt wastewater 2+ Low content can be supplemented with either MgO or MgCl2, for F- If the two-step synergistic removal process can meet the requirements for system reuse or downstream process influent, it can be adopted. If the two-step synergistic removal process cannot meet the requirements for system reuse or downstream process influent, then deep defluorination must be performed after the two-step synergistic removal process to obtain treated product water.

[0066] In some embodiments of the present invention, the deep defluorination process includes: coagulating the second supernatant, defluorination agent, coagulant aid and flocculant under pH conditions of 6-7.

[0067] In some embodiments of the present invention, the pH value of the second supernatant may be adjusted by using an acid, preferably selected from hydrochloric acid and / or sulfuric acid.

[0068] In some embodiments of the present invention, the deep defluorination process is carried out in the deep defluorination unit. Specifically, the pH of the second supernatant is adjusted to 6-7 in the intermediate water tank 20. The effluent from the intermediate water tank 20 is mixed with sludge and micro-sand returned from the cyclone reactor 18 by the jet mixer 16, and then fully mixed with defluorination agent and flocculant by the dosing mixer 17 before entering the cyclone reactor 18. - The generated sediment particles and micro-sand form large flocs that continuously collide and combine with other sediment particles and flocs during the swirling process, forming denser and larger precipitates that settle at the bottom of the swirling reactor. Less dense particles and flocs spiral upwards along the central tube of the swirling reactor's spiral structure, constantly colliding with the spiral blades and returning to their original positions. During this return process, they form larger flocs or adhere to the outer surface of the spiral. Clear water spirals upwards along the spiral pipe to the upper space of the swirling reactor and overflows. After the swirling reactor has been running for a period of time, the turbidity of the effluent increases, so the influent is stopped, and the sludge discharge motor is started to rotate the spiral to discharge sludge. After sludge discharge is completed, the reactor is restarted, and the sludge is discharged to the micro-sand sedimentation tank 19. The lighter sludge without micro-sand in the upper part of the micro-sand sedimentation tank 19 is discharged, while the denser sludge containing micro-sand in the lower part is recycled back to the jet mixer 16, with a sludge return ratio of 40-70 wt%.

[0069] The inventors of this invention discovered in their research that by employing an integrated sludge recirculation and micro-sand recovery structure, fluoride ions react with a specialized agent to form flocs in the dosing mixer. These flocs then combine with micro-sand, increasing the density and settling velocity of the floc sediment. Furthermore, by using a cyclone reactor for deep fluoride ion removal, the density of the resulting floc sediment and the formation of large flocs can be further increased.

[0070] In some embodiments of the present invention, preferably, the defluorinating agent is selected from at least one of polyaluminum sulfate, polyaluminum chloride, polyferric sulfate, and polyferric chloride.

[0071] In this invention, in order to ensure that the F in the second supernatant - The reaction involves thorough mixing with defluorinating agents and flocculants. Preferably, the coagulation reaction is carried out under the following conditions: a residence time of 5-10 minutes in a cyclone reactor.

[0072] In some embodiments of the present invention, the coagulant aid and flocculant are substances capable of increasing the aggregation degree of suspended solids in high-salinity wastewater. Specific types of these substances are well known to those skilled in the art. Preferably, the coagulant aid is selected from at least one of polyaluminum chloride, polyferric chloride, and polyferric sulfate, with polyferric sulfate (PFS) being the most preferred. The flocculant is selected from polyacrylamide (PAM).

[0073] In some embodiments of the present invention, the dosage of the coagulant aid is 30-50 mg / L of wastewater relative to the volume of high-salinity wastewater, and the dosage of the flocculant is 1-3 mg / L of wastewater, wherein the concentration of the coagulant aid is 10-20%, and the concentration of the flocculant is 0.1-0.2%. This preferred method can effectively promote the aggregation of suspended solids in high-salinity wastewater.

[0074] In some embodiments of the present invention, Mg 2+ The removal rate of Ca is not less than 99%. 2+ The removal rate of is not less than 98%, the removal rate of Si is not less than 99%, and the removal rate of F is not less than 98%. - The removal rate is not less than 96%. The removal rate is calculated using the following formula:

[0075]

[0076] The present invention will be described in detail below through examples. Unless otherwise stated, all raw materials used in the following examples and comparative examples are commercially available products.

[0077] Example 1

[0078] The mother liquor quality of a crystallizer in a coal chemical enterprise is shown in Table 1.

[0079] exist Figure 1 The treatment system for dehardening, desiliconizing, and defluorinating high-salt wastewater, as shown, involves the treatment of crystallizer mother liquor. The specific operating steps are as follows:

[0080] (1) The mother liquor from the crystallizer enters the primary mixing reaction tank 1 at a certain flow rate. The amount of Ca(OH)2 powder added is adjusted, and the pH of the suspension is maintained at about 11.4 at a stirring speed of 150 r / min. After 30 min, the effluent enters the primary coagulation tank 2, where 30 mg / L of 10% concentration PFS is added and the mixture is stirred at 50 r / min for 10 min. The effluent then enters the primary flocculation tank 3, where 1 mg / L of 0.1% concentration PAM is added and the mixture is stirred at 50 r / min for 10 min. The effluent then enters the primary sedimentation tank 4 and is stirred at 30 r / min for 20 min. Finally, the effluent enters the primary inclined tube clarifier tank 5. The effluent from the primary inclined tube clarifier tank 5 is recorded as the first supernatant. The analysis of the first supernatant is shown in Table 1.

[0081] (2) The overflow of the primary inclined tube clarifier 5 into the secondary mixing reaction tank 11 is treated with 7.91 g / L Na2CO3 and stirred at 150 r / min for 30 min. The effluent then enters the secondary coagulation tank 12, where 30 mg / L of 10% PFS is added and stirred at 50 r / min for 10 min. The effluent then enters the secondary flocculation tank 13, where 1 mg / L of 0.1% PAM is added and stirred at 50 r / min for 10 min. The effluent then enters the secondary sedimentation tank 14 and is stirred at 30 r / min for 20 min. Finally, the effluent enters the secondary inclined tube clarifier 15. The effluent from the secondary inclined tube clarifier 15 is recorded as the second supernatant. The analysis of the second supernatant is shown in Table 1.

[0082] (3) The overflow of the secondary inclined tube clarifier into the intermediate water tank 20 is used to adjust the pH of the second supernatant to 6. The effluent from the intermediate water tank 20 is mixed with the sludge and micro-sand returned from the cyclone reactor 18 by the jet mixer 16, and then thoroughly mixed with the defluorination agent and 0.1% PAM by the dosing mixer 17 before entering the cyclone reactor 18. The effluent is held in the cyclone reactor 18 for 5 minutes to obtain the treated permeate. The defluorination agent used is polyaluminum chloride, with an addition amount of 700 mg / L, and the PAM addition amount is 2 mg / L. The analysis of the treated permeate is shown in Table 1.

[0083] Table 1

[0084]

[0085] As can be seen from Table 1, Mg 2+ The concentration of Mg was reduced from 307 mg / L to 2.2 mg / L. 2+ The removal rate was 99.3%; Ca 2+ The concentration of Ca was reduced from 626 mg / L to 6.6 mg / L. 2+ The removal rate was 98.9%; Si was removed from 80.1 mg / L to 0 mg / L, and the removal rate of Si was 100%; F -The concentration of particulate matter was reduced from 186 mg / L to 5.2 mg / L, with a removal rate of 97.2%.

[0086] Example 2

[0087] The mother liquor quality of a crystallizer in a coal chemical enterprise is shown in Table 2.

[0088] (1) The mother liquor from the crystallizer enters the primary mixing reaction tank 1 at a certain flow rate, and a high-concentration Ca(OH)2 slurry is added. The pH of the suspension is adjusted to about 11.4 under stirring at 100 r / min. After 20 min, the effluent enters the primary coagulation tank 2, and 50 mg / L of 10% PFS is added. The mixture is stirred at 40 r / min for 30 min, and the effluent enters the primary flocculation tank 3, where 3 mg / L of 0.1% PAM is added. The mixture is stirred at 40 r / min for 20 min, and the effluent enters the primary sedimentation tank 4. The mixture is stirred at 30 r / min for 20 min, and the effluent enters the primary inclined tube clarifier tank 5. The effluent from the primary inclined tube clarifier tank 5 is recorded as the first supernatant. The analysis of the first supernatant is shown in Table 2.

[0089] (2) The overflow of the primary inclined tube clarifier 5 into the secondary mixing reaction tank 11 is treated with 6.17 g / L Na2CO3 and stirred at 100 r / min for 20 min. The effluent then enters the secondary coagulation tank 12, where 30 mg / L of 10% PFS is added and stirred at 50 r / min for 10 min. The effluent then enters the secondary flocculation tank 13, where 2 mg / L of 0.1% PAM is added and stirred at 50 r / min for 10 min. The effluent then enters the secondary sedimentation tank 14 and is stirred at 30 r / min for 20 min. Finally, the effluent enters the secondary inclined tube clarifier 15. The effluent from the secondary inclined tube clarifier 15 is recorded as the second supernatant. The analysis of the second supernatant is shown in Table 2.

[0090] (3) The overflow effluent from the secondary inclined tube clarifier enters the intermediate water tank 20. In the intermediate water tank 20, the pH of the second supernatant is adjusted back to 6. The effluent from the intermediate water tank 20 is mixed with the sludge and micro-sand returned from the cyclone reactor 18 by the jet mixer 16, and then thoroughly mixed with the defluorination agent and 0.1% PAM by the dosing mixer 17 before entering the cyclone reactor 18. After staying in the cyclone reactor 18 for 5 minutes, the treated permeate is obtained. The defluorination agent used is polyaluminum chloride, with an addition amount of 700 mg / L, and the PAM addition amount is 2 mg / L. The analysis of the treated permeate is shown in Table 2.

[0091] Table 2

[0092]

[0093] As can be seen from Table 2, Mg 2+The concentration of Mg was reduced from 307 mg / L to 2.1 mg / L. 2+ The removal rate was 99.3%; Ca 2+ The concentration of Ca was reduced from 626 mg / L to 11.4 mg / L. 2+ The removal rate was 98.2%; Si was removed from 80.1 mg / L to 0 mg / L, and the removal rate of Si was 100%; F - The concentration was reduced from 186 mg / L to 7.21 mg / L, with a removal rate of 96.1%.

[0094] Example 3

[0095] The water quality of high-salinity wastewater is shown in Table 3, i.e., the F in the raw water... - When the content is low, the high-salinity wastewater is treated according to the method in Example 1, except that deep defluorination is not performed, i.e., step (2) is completed. The water quality before and after treatment is shown in Table 3.

[0096] Table 3

[0097]

[0098] As can be seen from Table 3, Mg 2+ Mg was removed from 64.8 mg / L to 0 mg / L. 2+ The removal rate was 100%; Ca 2+ The concentration of Ca was reduced from 436.6 mg / L to 4.7 mg / L. 2+ The removal rate was 98.9%; Si was removed from 76.7 mg / L to 0 mg / L, and the removal rate of Si was 100%; F - The concentration was reduced from 50.82 mg / L to 0 mg / L, with a removal rate of 100%.

[0099] Comparative Example 1

[0100] The high-salinity wastewater was treated according to the method in Example 1, except that the Ca(OH)₂ powder was replaced with a Ca(OH)₂ solution. The water quality before and after treatment is shown in Table 4.

[0101] Table 4

[0102]

[0103] As can be seen from Table 4, Mg 2+ The concentration of Mg was reduced from 307 mg / L to 1.8 mg / L. 2+ The removal rate was 99.4%; Ca 2+ The concentration of Ca was reduced from 626 mg / L to 27.1 mg / L. 2+ The removal rate was 95.7%; Si was removed from 80.1 mg / L to 0 mg / L, and the removal rate of Si was 100%; F- The concentration of particulate matter was reduced from 186 mg / L to 17.7 mg / L, with a removal rate of 90.5%.

[0104] The analysis results of the above embodiments and comparative examples show that when the treatment system and method provided by the present invention are used to treat high-salt wastewater, calcium, magnesium, silicon and fluoride ions in the high-salt wastewater can be effectively removed, and the ion removal rate is high.

[0105] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A treatment system for high-salinity wastewater hardness reduction, silicon removal and fluorine removal, characterized in that, The treatment system comprises: a first reaction precipitation unit, a second reaction precipitation unit and an optional deep fluorine removal unit connected in sequence; wherein, The first reaction precipitation unit comprises a first dosing device for adding Ca(OH)2 powder or Ca(OH)2 high-concentration slurry; The first reaction precipitation unit is used for simultaneously performing magnesium precipitation, silicon precipitation and primary fluorine precipitation on the high-salinity wastewater; The second reaction precipitation unit is used for simultaneously performing calcium precipitation and secondary fluorine precipitation on the effluent of the first reaction precipitation unit; The first reaction precipitation unit further comprises: a first mixed reaction tank, a first coagulation tank, a first flocculation tank, a first sedimentation tank and a first inclined-tube clarifier; the first mixed reaction tank, the first coagulation tank and the first flocculation tank are each provided with a dosing port; wherein, the dosing port of the first mixed reaction tank is connected with the first dosing device, the dosing port of the first coagulation tank is connected with a third dosing device, and the dosing port of the first flocculation tank is connected with a fourth dosing device; The second reaction precipitation unit comprises: a second mixed reaction tank, a second coagulation tank, a second flocculation tank, a second sedimentation tank and a second inclined-tube clarifier; the second mixed reaction tank, the second coagulation tank and the second flocculation tank are each provided with a dosing port; wherein, the dosing port of the second mixed reaction tank is connected with a second dosing device, the dosing port of the second coagulation tank is connected with the third dosing device, and the dosing port of the second flocculation tank is connected with the fourth dosing device; the second dosing device is used for adding Na2CO3 solution, the third dosing device is used for adding a coagulant aid, and the fourth dosing device is used for adding a flocculant.

2. The processing system of claim 1, wherein, The deep fluorine removal unit comprises: a jet mixer, a dosing mixer, a cyclone reactor and a micro-sand precipitation tank connected in sequence; wherein, the cyclone reactor is provided with a central pipe in which a spiral structure is arranged; the dosing mixer is provided with a dosing port; and the micro-sand precipitation tank is provided with a blowdown port.

3. The processing system of claim 2, wherein, The first coagulation tank is provided with a pH meter; The first mixed reaction tank, the first coagulation tank, the first flocculation tank, the second mixed reaction tank, the second coagulation tank and the second flocculation tank are each provided with a stirring device; The first inclined-tube clarifier and the second inclined-tube clarifier are each provided with a blowdown port.

4. A treatment method for removing hardness, silicon and fluorine from high-salinity wastewater, characterized by, The method is implemented in the treatment system of any one of claims 1-3, and comprises the following steps: (1) first mixing the high-salinity wastewater with a first medicament to obtain a suspension, and then first contacting the suspension with a coagulant aid and a flocculant, and then separating the product to obtain a first supernatant; the first medicament is Ca(OH)2 powder or Ca(OH)2 high-concentration slurry; (2) second mixing the first supernatant with Na2CO3 solution to obtain a suspension, and then second contacting the suspension with a coagulant aid and a flocculant, and then separating the product to obtain a second supernatant; (3) optionally, performing deep fluorine removal on the second supernatant to obtain treated effluent.

5. The treatment method of claim 4, wherein, Step (1) is performed in the first reaction precipitation unit.

6. The treatment method of claim 4, wherein, The pH value of the suspension obtained after the first mixing of the high-salinity wastewater with the first medicament is 11-14.

7. The treatment method according to claim 4 or 6, wherein, The pH value of the suspension obtained after the first mixing of the high-salinity wastewater with the first agent is 11-12.

8. The treatment method of claim 4, wherein, The conditions of the first mixing include: a stirring speed of 100-150 r / min, and a mixing residence time of 10-30 min.

9. The treatment method of claim 4, wherein, The conditions of the first contacting include: a stirring speed of 30-50 r / min, and a contacting residence time of 10-30 min.

10. The treatment method of claim 4, wherein, The step (2) is performed in a secondary reaction precipitation unit.

11. The treatment method according to claim 4 or 10, wherein, The conditions of the second mixing include: a stirring speed of 100-150 r / min, and a mixing residence time of 10-30 min.

12. The treatment method according to claim 4 or 10, wherein, The conditions of the second contacting include: a stirring speed of 30-50 r / min, and a contacting residence time of 10-30 min.

13. The treatment method according to claim 4 or 10, wherein, Na2CO3 solution in terms of CO3 2- and the first supernatant in terms of Ca 2+ is 3-5:

1.

14. The treatment method according to any one of claims 4, 5, 6, 8, 9 and 10, wherein, The deep fluorine removal is performed in a deep fluorine removal unit, and the process of the deep fluorine removal includes: performing a coagulation reaction on the second supernatant, a fluorine removal agent, and a flocculant under the condition that the pH value is 6-7.

15. The treatment method of claim 14, wherein, The conditions of the coagulation reaction include: a residence time of 5-10 min in a cyclone reactor.

16. The treatment method according to any one of claims 4, 5, 6, 8, 9, 10 and 15, wherein, The coagulant aid is at least one selected from polyaluminum chloride, polyferric chloride, and polyferric sulfate.

17. The treatment method according to any one of claims 4, 5, 6, 8, 9, 10 and 15, wherein, The coagulant aid is polyferric sulfate.

18. The treatment method according to any one of claims 4, 5, 6, 8, 9, 10 and 15, wherein, The flocculant is selected from polyacrylamide.

19. The treatment method according to any one of claims 4, 5, 6, 8, 9, 10 and 15, wherein, The amount of the coagulant aid is 30-80 mg / L of wastewater, and the amount of the flocculant is 1-3 mg / L of wastewater, relative to the volume of the high-salinity wastewater; wherein the concentration of the coagulant aid is 10-20%, and the concentration of the flocculant is 0.1-0.2%.

20. The treatment method according to any one of claims 4, 5, 6, 8, 9, 10 and 15, wherein, Mg 2+ removal rate of not less than 99%, Ca 2+ removal rate of not less than 98%, Si removal rate of not less than 99%, F - removal rate of not less than 96%.

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