Sodium fluosilicate sewage treatment system

Abstract

The utility model discloses a sodium fluosilicate sewage treatment system, which is characterized in that sodium fluosilicate wastewater is subjected to fluorine removal and phosphorus removal, then sodium carbonate or sodium hydroxide is added, SO4 < 2-> in the wastewater is converted into a sodium sulfate solution, the wastewater is subjected to hardness removal treatment, then is subjected to ultrafiltration and nanofiltration membrane filtration, concentrated water containing the sodium sulfate solution is recovered to a sodium sulfate collection tank, and the sodium fluosilicate sewage is obtained. Produced water is recycled as replenishing water of the device, so that zero discharge of sewage can be realized.

Description

Technical Field

[0001] The present invention relates to the field of sodium fluorosilicate wastewater treatment, and in particular to a sodium fluorosilicate wastewater treatment system. Background Art

[0002] The sodium fluosilicate production process generates large amounts of wastewater, which contains fluorine, acid, and phosphorus, making wastewater treatment extremely difficult. Traditionally, slaked lime has been added to defluorinate, dephosphorize, and deacidify the wastewater, followed by pH adjustment. The wastewater is then diluted with clean water and discharged after meeting standards. This process has several drawbacks: First, the addition of slaked lime to defluorinate, dephosphorize, and deacidify the wastewater and adjust its pH before discharge. This process generates large amounts of hazardous sludge, which is difficult to dispose of. Second, the high consumption of slaked lime increases wastewater treatment costs. Third, the need to add large amounts of clean water increases water consumption. Fourth, the discharged wastewater pollutes the environment, resulting in high treatment costs. Fifth, sodium sulfate loss is high, resulting in low yields, increasing the production cost of sodium fluosilicate. Utility Model Content

[0003] The novel method solves the problem of sodium fluorosilicate wastewater generating a large amount of hazardous waste sludge; solves the problem of large consumption of slaked lime in wastewater treatment; solves the problem of high wastewater treatment cost; solves the problem of high water consumption in the sodium fluorosilicate wastewater treatment process; solves the problem of sodium sulfate recovery in sodium fluorosilicate wastewater, and solves the problem of high sodium sulfate consumption in the sodium fluorosilicate production process.

[0004] In order to solve the above problems, the present invention is achieved through the following technical solutions:

[0005] A sodium fluorosilicate wastewater treatment system comprises a sodium fluorosilicate wastewater pool, wherein the sodium fluorosilicate wastewater pool is connected to the inlet of a sewage regulating pool; the outlet of the sewage regulating pool is connected to the inlet of a sludge sedimentation pool; the sludge outlet of the sludge sedimentation pool is connected to the inlet of a sludge dewatering device; the sewage outlet of the sludge sedimentation pool is connected to the inlet of a primary hardness removal device; the sewage outlet of the primary hardness removal device is connected to the inlet of a multi-media filter; the filtrate outlet of the multi-media filter is connected to the inlet of an ultrafiltration (UF) impurity removal device; the filtrate outlet of the ultrafiltration (UF) impurity removal device is connected to the inlet of a resin softening secondary hardness removal device; the clear water outlet of the resin softening secondary hardness removal device is connected to the inlet of a nanofiltration (NF) device; and the concentrated water outlet of the nanofiltration (NF) device is connected to the inlet of a nanofiltration concentrated water pool.

[0006] The sludge outlet of the sludge dewatering device is connected to the sludge transport device.

[0007] The outlet of the nanofiltration concentrated water pool is connected to the inlet of the concentrated water evaporation MVR device, the condensate outlet of the concentrated water evaporation MVR device is connected to the inlet of the evaporation condensation water device, and the outlet of the evaporation condensation water device is connected to the water recovery device; the concentrated water outlet of the concentrated water evaporation MVR device is connected to the sodium sulfate collection tank.

[0008] The inlet of the sewage regulating tank is also connected to the filter residue outlet of the multi-media filter, the filter residue outlet of the ultrafiltration UF impurity removal device and the concentrated water outlet of the resin softening secondary hardness removal device.

[0009] The clean water outlet of the nanofiltration NF device is connected to the inlet of the nanofiltration water production device, the regenerated water outlet of the nanofiltration water production device is connected to the inlet of the resin softening secondary hardness removal device, the second backwash water outlet of the nanofiltration water production device is connected to the inlet of the multi-media filter, and the first backwash water outlet of the nanofiltration water production device is connected to the inlet of the ultrafiltration UF impurity removal device.

[0010] The outlet of the nanofiltration water production device is connected to a water production recovery device.

[0011] The sewage outlet of the sludge dewatering device is connected to the inlet of the sewage regulating tank.

[0012] The sludge outlet of the first-stage hardness removal device is connected to the inlet of the sludge dewatering device.

[0013] The inlet of the sewage regulating tank is also connected to a slaked lime tank.

[0014] The inlet of the first-level hardness removal device is also connected to the sodium carbonate reagent tank.

[0015] Compared with the existing technology, the beneficial effects of this new technology are:

[0016] 1. This new method can treat sodium fluorosilicate wastewater by converting SO4 2- After being converted into Na2SO4 and then concentrated and reused, it not only increases SO4 2- The recovery rate is high, and the consumption of slaked lime in wastewater is greatly reduced, which also saves disposal costs and the consumption of sodium sulfate, the raw material required for the production of sodium fluorosilicate.

[0017] 2. This new method reduces the amount of sludge produced by sodium fluorosilicate wastewater, thereby reducing the difficulty and cost of sludge disposal.

[0018] 3. The clean water and condensate generated by the new sodium fluorosilicate wastewater treatment system are recycled as production water, reducing the amount of water replenished outside the device system and lowering production costs.

[0019] 4. This new sodium fluorosilicate wastewater passes through a two-stage hardness removal device, and then undergoes a three-stage purification and separation process of multi-media filtration, ultrafiltration UF impurity removal device, and nanofiltration water production; the resulting reclaimed water and backwash water can be recycled, achieving zero discharge of sodium fluorosilicate production wastewater and saving sewage treatment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of the sodium fluorosilicate wastewater treatment system;

[0021] Figure numerals: sodium fluosilicate wastewater tank 1, sewage regulating tank 2, slaked lime tank 3, sludge sedimentation tank 4, sludge dewatering device 5, sludge transport device 6, primary hardness removal device 7, sodium carbonate agent tank 8, multi-media filter 9, ultrafiltration UF impurity removal device 10, resin softening secondary hardness removal device 11, nanofiltration NF device 12, nanofiltration concentrated water tank 13, concentrated water evaporation MVR device 14, sodium sulfate collection tank 15, evaporation condensation water device 16, nanofiltration water production device 17, water production recovery device 18, regenerated water outlet 19, first backwash water outlet 20, second backwash water outlet 21. DETAILED DESCRIPTION

[0022] In order to further understand the content and features of the present invention, embodiments of the present invention are given below. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention.

[0023] This new method adds slaked lime to sodium fluorosilicate wastewater to remove fluorine and phosphorus, then adds sodium carbonate to remove SO4 2- The concentrated water containing sodium sulfate solution is obtained after the wastewater is converted into sodium sulfate and hardness removal treatment is carried out on the wastewater. The concentrated water is then recycled to the sodium sulfate collection pool 15 and the nanofiltration water production device 17 is used as water replenishment for the device, thereby achieving zero wastewater discharge.

[0024] Example 1

[0025] A sodium fluorosilicate wastewater treatment system comprises a sodium fluorosilicate wastewater pool 1, wherein the sodium fluorosilicate wastewater pool 1 is connected to the inlet of a sewage regulating pool 2; the outlet of the sewage regulating pool 2 is connected to the inlet of a sludge sedimentation pool 4; the sludge outlet of the sludge sedimentation pool 4 is connected to the inlet of a sludge dewatering device 5; the sewage outlet of the sludge sedimentation pool 4 is connected to the inlet of a primary hardness removal device 7; the sewage outlet of the primary hardness removal device 7 is connected to the inlet of a multi-media filter 9; the filtrate outlet of the multi-media filter 9 is connected to the inlet of an ultrafiltration (UF) impurity removal device 10; the filtrate outlet of the ultrafiltration (UF) impurity removal device 10 is connected to the inlet of a resin softening secondary hardness removal device 11; the clear water outlet of the resin softening secondary hardness removal device 11 is connected to the inlet of a nanofiltration (NF) device 12; and the concentrated water outlet of the nanofiltration (NF) device 12 is connected to the inlet of a nanofiltration concentrated water pool 13.

[0026] The sludge outlet of the sludge dewatering device 5 is connected to the sludge transport device 6 .

[0027] The outlet of the nanofiltration concentrated water pool 13 is connected to the inlet of the concentrated water evaporation MVR device 14, the condensate outlet of the concentrated water evaporation MVR device 14 is connected to the inlet of the evaporation condensation water device 16, and the outlet of the evaporation condensation water device 16 is connected to the water recovery device 18; the concentrated water outlet of the concentrated water evaporation MVR device 14 is connected to the sodium sulfate collection pool 15.

[0028] The inlet of the sewage regulating tank 2 is also connected to the filter residue outlet of the multi-media filter 9, the filter residue outlet of the ultrafiltration UF impurity removal device 10 and the concentrated water outlet of the resin softening secondary hardness removal device 11.

[0029] The clean water outlet of the nanofiltration NF device 12 is connected to the inlet of the nanofiltration water production device 17, the regenerated water outlet 19 of the nanofiltration water production device 17 is connected to the inlet of the resin softening secondary hardness removal device 11, the second backwash water outlet 21 of the nanofiltration water production device 17 is connected to the inlet of the multi-media filter 9, and the first backwash water outlet 20 of the nanofiltration water production device 17 is connected to the inlet of the ultrafiltration UF impurity removal device 10.

[0030] The outlet of the nanofiltration water production device 17 is connected to the water production recovery device 18 .

[0031] The sewage outlet of the sludge dewatering device 5 is connected to the inlet of the sewage regulating tank 2 .

[0032] The sludge outlet of the primary hardness removal device 7 is connected to the inlet of the sludge dewatering device 5 .

[0033] The inlet of the sewage regulating tank 2 is also connected to the slaked lime tank 3. The inlet of the first-stage hardness removal device 7 is also connected to the sodium carbonate reagent tank 8.

[0034] The following combination Figure 1 Description: This wastewater treatment system is specially designed for sodium fluorosilicate wastewater.

[0035] The sodium fluorosilicate wastewater in the sodium fluorosilicate wastewater pool 1 enters the sewage regulating pool 2, and Ca(OH)2 is added through the slaked lime tank 3, and sedimentation and separation are carried out in the sludge sedimentation tank 4. The settled sludge is input into the sludge dewatering device 5 through the sludge outlet of the sludge sedimentation tank 4 for dehydration and treatment. The sludge generated in the sludge dewatering device 5 is transported out for treatment through the sludge transport device 6. The sewage separated in the sludge sedimentation tank 4 enters the primary hardness removal device 7 through the sewage outlet of the sludge sedimentation tank 4. The primary hardness removal device 7 adds Na2CO3 through the sodium carbonate agent tank 8 for hardness removal treatment. The primary hardness removal device 7 sends the sludge to the sludge dewatering device 5 through the sludge outlet. The primary hardness removal device 7 removes The hardened sewage enters the multi-media filter 9 for preliminary filtration, and the filtrate after filtration by the multi-media filter 9 enters the ultrafiltration UF impurity removal device 10 for impurity removal, the resin softening secondary hardness removal device 11, and the nanofiltration NF device 12 for water separation in sequence. Among them, the concentrated water produced by the nanofiltration NF device 12 enters the nanofiltration concentrated water pool 13 for temporary storage, and then enters the concentrated water evaporation MVR device 14. The evaporated concentrated water Na2SO4 is sent to the sodium sulfate collection pool 15 for reuse. The condensed water obtained after the steam of the evaporation MVR device 14 passes through the evaporation condensation water device 16 is combined with the nanofiltration water flowing into the nanofiltration water production device 17 of the nanofiltration NF12 device and stored in the water production recovery device 18.

[0036] The principle of this new sodium fluorosilicate wastewater treatment system is as follows: when the sodium fluorosilicate wastewater pool 1 enters the sewage regulating tank 2, it reacts with the slaked lime added in the slaked lime tank 3 to generate calcium fluoride, calcium phosphate, and calcium sulfate. The sludge is then separated in the sludge sedimentation tank 4. After the sludge enters the sludge dewatering device 5, the generated sludge is transported out for treatment, and the wastewater returns to the wastewater regulating tank 3. The sewage from the sludge sedimentation tank 4 enters the primary hardness removal device 7, where the sodium carbonate agent is added to the agent tank 8 for hardness removal treatment. The sludge then enters the sludge dewatering device 5. The sewage after hardness removal enters the multi-media filter 9 for preliminary filtration. After filtering out suspended matter and colloidal impurities, it enters the ultrafiltration UF impurity removal device 10 to remove bacteria, microorganisms, and macromolecular substances. It then passes through the resin softening secondary hardness removal device 11 to remove residual calcium. The wastewater after secondary hardness removal enters the nanofiltration NF device 12 for separation, and the Na2SO4 in the sewage enters the nanofiltration concentrated water pool 13. After concentration by the concentrated water evaporation MVR device 14, the mass fraction of Na2SO4 reaches more than 10% and is then sent to the concentrated water Na2SO4 for reuse to the sodium sulfate collection pool 15 for reuse. The clear water produced by the nanofiltration NF device 12 and the condensate of the concentrated water evaporation MVR device 14 pass through the condensate evaporation device 16 and are used as production water for the water recovery device 18.

[0037] Preferably, the sludge dewatering device 5 is purchased from Hubei Meichen Environmental Protection Co., Ltd.; model: plate and frame sludge dewatering machine;

[0038] Preferably, the first-stage hardness removal device 7 is purchased from Hubei Meichen Environmental Protection Co., Ltd. CY-1 model;

[0039] Preferably, the multi-media filter 9 is purchased from Hubei Meichen Environmental Protection Co., Ltd. Model MF-1;

[0040] Preferably, the ultrafiltration UF impurity removal device 10 is purchased from Hubei Meichen Environmental Protection Co., Ltd. UF-1 model;

[0041] Preferably, the resin softening and secondary hardness removal device 11 is purchased from Hubei Meichen Environmental Protection Co., Ltd. Model TKO-2;

[0042] Preferably, the nanofiltration NF device 12 is purchased from Hubei Meichen Environmental Protection Co., Ltd. Model NF-1;

[0043] Preferably, the concentrated water evaporation MVR device 14 is purchased from Hubei Meichen Environmental Protection Co., Ltd. Model MVR-1;

[0044] Preferably, the nanofiltration water production device 17 is purchased from Hubei Meichen Environmental Protection Co., Ltd. as model RO-1.

[0045] Preferably, the aromatic polyamide composite membrane provided in the nanofiltration concentrated water tank 13 is purchased from Hubei Meichen Environmental Protection Co., Ltd.; model NM-1.

[0046] The main ions, ammonia nitrogen content (TN and TP) and impurity content of the wastewater in the sodium fluosilicate wastewater pool 1 are shown in Table 1:

[0047] NH3-N is the ammoniacal nitrogen content in the wastewater; TP is the total phosphorus content in the wastewater; TN is the total nitrogen content in the wastewater.

[0048] Table 1

[0049]

[0050] Sodium fluorosilicate wastewater is acidic, and the water in the wastewater contains Cl - 、F - 、Na + , nitrogen (nitrogen includes free NH3 and NH4 + ions), SO4 2- PO4 3- , also contains H + The hydrogen ion content is the residual after the charge of each component in Table 1 is neutralized. Other impurities in Table 1 include bacteria, microorganisms, macromolecules, E. coli, and proteins. Sodium fluosilicate wastewater also contains colloids and suspended matter. These impurities are not measurable, so the specific content of each impurity ion is not detailed.

[0051] Sodium fluorosilicate wastewater and Ca(OH)2 are stirred evenly in sewage regulating tank 2 to obtain sludge slurry, and free NH3 and NH4 in sodium fluorosilicate wastewater are separated. + The ions are converted into gaseous NH3 and discharged.

[0052] The sludge slurry settles in the sludge sedimentation tank 4 to obtain primary sludge and mixed liquid. The water in the mixed liquid contains dissolved CaCl2, NaCl, Na2SO4 and other impurities.

[0053] Primary sludge is dehydrated by sludge dewatering unit 5 and then transported to a sludge transport unit. This sludge contains water, CaSO₄, CaCO₃, CaF₂, and Ca₃(PO₄)₂. CaCO₃ is due to the dissolution of CO₂ in the air during the open discharge of ammonia from sewage regulating tank 2 and sludge sedimentation tank 4, and the amount of CaCO₃ is negligible. The amount of Ca₃(PO₄)₂ in the transported sludge is extremely low and can be ignored.

[0054] The mixed liquid after removing fluorine and phosphorus is passed into the primary hardness removal device 7, in which the excessive calcium ions are removed, and then filtered through the multi-media filter 9 to filter out suspended matter and colloidal impurities, and then passed through the ultrafiltration UF impurity removal device 10 to remove bacteria, microorganisms, macromolecules, Escherichia coli, and proteins. The obtained filtrate is then softened by the resin and passed through the secondary hardness removal device 11 to remove residual calcium ions to obtain secondary hardness removal wastewater. The secondary hardness removal wastewater enters the nanofiltration NF device 12 for separation to obtain clean water and concentrated water; the clean water is H2O, and the concentrated water contains Na2SO4, NaCl and water.

[0055] The clean water separated by the nanofiltration (NF) device 12 is fed into the nanofiltration water production device 17, and the concentrated water is passed into the nanofiltration concentrated water tank 13. The nanofiltration concentrated water tank 13 removes the NaCl impurity from the concentrated water to produce an aqueous solution of Na2SO4. After the aqueous solution of Na2SO4 is concentrated in the concentrated water evaporation (MVR) device 14, the concentrated Na2SO4 solution is fed into the sodium sulfate collection tank 15. The concentrated Na2SO4 solution can be used as a raw material for the production of sodium fluorosilicate.

[0056] The clean water in the concentrated water evaporation MVR device 14 is then sent to the evaporation and condensation device 16 for evaporation and condensation to obtain purified water condensate which is then sent to the water recovery device 18 as production water for the production of sodium fluorosilicate.

[0057] In addition to using the concentrated water evaporation MVR device 14 for concentrated water, this patent also allows the use of other evaporation treatment equipment without affecting the overall operational performance. The concentrated water evaporation MVR device 14 in this patent also concentrates the Na2SO4 concentration and sends it to the sodium sulfate collection tank 15. The collected sodium sulfate can be used as raw material for the production of sodium fluorosilicate. The instrument model of this patent is only a preferred embodiment, and does not limit the use of this instrument model. Those skilled in the art can also choose other different models of equipment as substitutes, and such equivalent conversions fall within the technical solution of this patent.

Claims

1. A sodium fluorosilicate wastewater treatment system, comprising a sodium fluorosilicate wastewater pool (1), characterized in that: The sodium fluorosilicate wastewater tank (1) is connected to the inlet of the sewage regulating tank (2); the outlet of the sewage regulating tank (2) is connected to the inlet of the sludge sedimentation tank (4); the sludge outlet of the sludge sedimentation tank (4) is connected to the inlet of the sludge dewatering device (5); the sewage outlet of the sludge sedimentation tank (4) is connected to the inlet of the primary hardness removal device (7); the sewage outlet of the primary hardness removal device (7) is connected to the inlet of the multi-media filter (9); the filtrate outlet of the multi-media filter (9) is connected to the inlet of the ultrafiltration UF impurity removal device (10); the filtrate outlet of the ultrafiltration UF impurity removal device (10) is connected to the inlet of the resin softening secondary hardness removal device (11); The clean water outlet of the resin softening secondary hardness removal device (11) is connected to the inlet of the nanofiltration NF device (12); and the concentrated water outlet of the nanofiltration NF device (12) is connected to the inlet of the nanofiltration concentrated water pool (13).

2. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The sludge outlet of the sludge dewatering device (5) is connected to the sludge transport device (6).

3. The sodium fluorosilicate wastewater treatment system according to claim 1, wherein: The outlet of the nanofiltration concentrated water pool (13) is connected to the inlet of the concentrated water evaporation MVR device (14), the condensate outlet of the concentrated water evaporation MVR device (14) is connected to the inlet of the evaporation condensation water device (16), and the outlet of the evaporation condensation water device (16) is connected to the produced water recovery device (18); the concentrated water outlet of the concentrated water evaporation MVR device (14) is connected to the sodium sulfate collection pool (15).

4. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The inlet of the sewage regulating tank (2) is also connected to the filter residue outlet of the multi-media filter (9), the filter residue outlet of the ultrafiltration UF impurity removal device (10), and the concentrated water outlet of the resin softening secondary hardness removal device (11).

5. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The clean water outlet of the nanofiltration NF device (12) is connected to the inlet of the nanofiltration water production device (17), the regenerated water outlet (19) of the nanofiltration water production device (17) is connected to the inlet of the resin softening secondary hardness removal device (11), the second backwash water outlet (21) of the nanofiltration water production device (17) is connected to the inlet of the multi-media filter (9), and the first backwash water outlet (20) of the nanofiltration water production device (17) is connected to the inlet of the ultrafiltration UF impurity removal device (10).

6. The sodium fluorosilicate wastewater treatment system according to claim 5, characterized in that: The outlet of the nanofiltration water production device (17) is connected to a water production recovery device (18).

7. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The sewage outlet of the sludge dewatering device (5) is connected to the inlet of the sewage regulating tank (2).

8. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The sludge outlet of the primary hardness removal device (7) is connected to the inlet of the sludge dewatering device (5).

9. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The inlet of the sewage regulating tank (2) is also connected to the slaked lime tank (3).

10. The sodium fluorosilicate wastewater treatment system according to claim 1, characterized in that: The inlet of the primary hardness removal device (7) is also connected to the sodium carbonate reagent tank (8).

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