Low-cost treatment system for sodium chloride type fluorine-containing wastewater

Abstract

The utility model relates to a sodium chloride type fluorine-containing wastewater low-cost treatment system which comprises a destabilization crystallizer, a nanofiltration membrane device is arranged on one side of the destabilization crystallizer, and the concentrated water end of the nanofiltration membrane device is communicated with the destabilization crystallizer. The utility model relates to the technical field of fluorine-containing wastewater treatment. When the device is started for the first time for wastewater treatment, a large amount of calcium chloride is added into the destabilization crystallizer, the calcium ion concentration is improved, after wastewater enters the destabilization crystallizer, calcium fluoride is separated out in a supersaturated mode, the defluorination effect is good, then the wastewater enters the nanofiltration membrane device for salt separation, concentrated water mainly comprises calcium chloride and flows back to the destabilization crystallizer, and the defluorination effect is good. Therefore, in the subsequent water purification process, only a small amount of calcium chloride consumed by calcium fluoride precipitation needs to be supplemented into the destabilization crystallizer, the consumption of the calcium chloride is reduced, and the treatment cost of the sodium chloride type fluorine-containing wastewater is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of fluorine-containing wastewater treatment, in particular to a sodium chloride type fluorine-containing wastewater low-cost treatment system. Background Art

[0002] Sodium chloride type fluoride-containing wastewater mainly comes from industrial production drainage, which contains a large amount of fluoride, sodium chloride and other pollutants, so it needs to be purified. At present, the fluoride removal technologies widely used in engineering are mainly chemical precipitation, coagulation precipitation and adsorption. The principle of chemical precipitation fluoride removal is to add calcium salt to the wastewater to make Ca 2+ It reacts with F- to form CaF2 precipitate. Lime and calcium chloride are often used in engineering projects. Among them, lime is cheap and easy to purchase, so it is widely used in engineering projects.

[0003] However, the treatment effect of adding lime (calcium carbonate) alone to sodium chloride-type fluoride-containing wastewater at room temperature is limited. Generally, the fluoride ion concentration can only be reduced to 20~30mg / L, and the defluorination effect is not good enough. Although adding calcium chloride has a better defluorination effect, this method requires a large amount of calcium chloride and the water purification cost is high. Therefore, a low-cost treatment system for sodium chloride-type fluoride-containing wastewater is proposed. Utility Model Content

[0004] In view of the shortcomings of the prior art, the purpose of the utility model is to provide a low-cost treatment system for sodium chloride type fluorine-containing wastewater, so as to solve the technical problems mentioned in the above background technology.

[0005] The above technical objectives of the utility model are achieved through the following technical solutions:

[0006] A low-cost treatment system for sodium chloride type fluorine-containing wastewater comprises a destabilization crystallizer, a nanofiltration membrane device is arranged on one side of the destabilization crystallizer, and a concentrated water end of the nanofiltration membrane device is connected to the destabilization crystallizer.

[0007] By adopting the above technical scheme, when the machine is started for the first time to treat wastewater, a large amount of calcium chloride is added to the destabilization crystallizer to increase the calcium ion concentration. After the wastewater enters the destabilization crystallizer, calcium fluoride is supersaturated and precipitated, and the defluorination effect is better. Then the wastewater enters the nanofiltration membrane device for salt separation, and the concentrated water is mainly calcium chloride, which flows back to the destabilization crystallizer. Therefore, in the subsequent water purification process, only a small amount of calcium chloride consumed by calcium fluoride precipitation needs to be supplemented to the destabilization crystallizer, which reduces the consumption of calcium chloride and thus reduces the treatment cost of sodium chloride-type fluoride-containing wastewater.

[0008] In a preferred example, the utility model can be further configured as follows: the output end of the destabilization crystallizer is connected to a filtering device, and the output end of the filtering device is connected to the input end of the nanofiltration membrane device.

[0009] By adopting the above technical solution, the filtering device filters the solid or colloid in the wastewater, thereby improving the inlet water quality of the nanofiltration membrane device.

[0010] In a preferred example, the utility model can be further configured as follows: the water production end of the nanofiltration membrane device is connected to a reverse osmosis device, and the output end of the reverse osmosis device is connected to an evaporation crystallizer.

[0011] By adopting the above technical solution, the nanofiltration membrane device intercepts the divalent ions and the monovalent ions are discharged through the water production end. Therefore, the produced water contains a large amount of relatively pure sodium chloride, which is concentrated again by the reverse osmosis device and then enters the evaporation crystallizer to obtain high-purity sodium chloride, which can be sold as a product to make up for part of the water treatment costs, thereby reducing the cost of water purification.

[0012] In a preferred example, the utility model can be further configured as follows: a pretreatment system is provided on one side of the destabilization crystallizer, and the output end of the pretreatment system is connected to the input end of the destabilization crystallizer.

[0013] By adopting the above technical solution, the pretreatment system removes suspended solids, colloids, COD and organic matter in the wastewater that have an impact on the subsequent membrane system and chemical reaction system to a lower level, making the turbidity of the wastewater less than 5NTU, thereby ensuring that the water treatment can proceed normally.

[0014] In summary, the utility model includes at least one of the following beneficial technical effects:

[0015] 1. This low-cost treatment system for sodium chloride-type fluoride-containing wastewater, when it is first started up for wastewater treatment, adds a large amount of calcium chloride to the destabilization crystallizer to increase the calcium ion concentration. After the wastewater enters the destabilization crystallizer, calcium fluoride is supersaturated and precipitated, and the defluorination effect is better. Then the wastewater enters the nanofiltration membrane device for salt separation, and the concentrated water is mainly calcium chloride, which flows back to the destabilization crystallizer. Therefore, in the subsequent water purification process, only a small amount of calcium chloride consumed by calcium fluoride precipitation needs to be added to the destabilization crystallizer, which reduces the consumption of calcium chloride, thereby reducing the treatment cost of sodium chloride-type fluoride-containing wastewater;

[0016] 2. This low-cost treatment system for sodium chloride-type fluorine-containing wastewater only needs to keep the reaction process in a weak acidic state to prevent scaling, without the need to add additional softening agents, further reducing the cost of water treatment;

[0017] 3. This is a low-cost treatment system for sodium chloride-type fluoride-containing wastewater. The nanofiltration membrane device intercepts divalent ions and discharges monovalent ions through the water production end. Therefore, the produced water contains a large amount of relatively pure sodium chloride. It is concentrated again by the reverse osmosis device and then enters the evaporation crystallizer to obtain high-purity sodium chloride, which can be sold as a product to make up for part of the water treatment costs, thereby reducing the cost of water purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for describing the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a flow chart of a low-cost treatment system for sodium chloride-type fluoride-containing wastewater according to this embodiment.

[0020] In the figure, 1. destabilization crystallizer; 2. nanofiltration membrane device; 3. filtration device; 4. reverse osmosis device; 5. pretreatment system; 6. evaporation crystallizer. DETAILED DESCRIPTION

[0021] The utility model is further described in detail below in conjunction with the accompanying drawings. Example 1

[0022] Reference Figure 1 The utility model discloses a low-cost treatment system for sodium chloride type fluorine-containing wastewater, comprising a destabilization crystallizer 1, a nanofiltration membrane device 2 is arranged on one side of the destabilization crystallizer 1, and a concentrated water end of the nanofiltration membrane device 2 is connected to the destabilization crystallizer 1.

[0023] In this embodiment, the nanofiltration membrane device 2 can intercept divalent and high-valent ions in the wastewater and allow the sodium chloride solution to pass through.

[0024] When the machine is first started for wastewater treatment, a large amount of calcium chloride is added to the destabilization crystallizer 1 to increase the calcium ion concentration and adjust the calcium hardness to 5000ppm. After the wastewater enters the destabilization crystallizer 1, calcium fluoride is supersaturated and precipitated, the defluorination effect is better, and the fluoride ion concentration can be reduced to 10 to 20mg / L.

[0025] Then the wastewater enters the nanofiltration membrane device 2 for salt separation, and the concentrated water is mainly calcium chloride, which flows back to the destabilization crystallizer 1. Therefore, in the subsequent water purification process, only a small amount of calcium chloride consumed by calcium fluoride precipitation needs to be supplemented to the destabilization crystallizer 1, which reduces the consumption of calcium chloride and thus reduces the treatment cost of sodium chloride-type fluoride-containing wastewater.

[0026] During this process, the solution pH is maintained between 6 and 6.5 to prevent calcium ions from absorbing carbon dioxide and forming scale.

[0027] Furthermore, the concentrated water end of the nanofiltration membrane device 2 flows back to the input end of the destabilization crystallizer 1, and is first mixed with the wastewater before entering the destabilization crystallizer 1, so that the dechlorination effect is better.

[0028] In a further preferred embodiment of the present invention, Figure 1 As shown, the output end of the destabilization crystallizer 1 is connected to a filtering device 3 , and the output end of the filtering device 3 is connected to the input end of the nanofiltration membrane device 2 .

[0029] In this embodiment, the filter device filters the solid or colloid in the wastewater to improve the water quality of the inlet water of the nanofiltration membrane device 2.

[0030] In a further preferred embodiment of the present invention, Figure 1 As shown, the water production end of the nanofiltration membrane device 2 is connected to a reverse osmosis device 4 , and the output end of the reverse osmosis device 4 is connected to an evaporation crystallizer 6 .

[0031] In this embodiment, the water production end of the nanofiltration membrane device 2 is a sodium chloride solution, which is concentrated again by the reverse osmosis device 4 and then enters the evaporation crystallizer 6 to obtain high-purity sodium chloride, which can be sold as a product to make up for part of the water treatment cost, thereby reducing the water purification cost.

[0032] In a further preferred embodiment of the present invention, Figure 1 As shown, a pretreatment system 5 is provided on one side of the destabilization crystallizer 1 , and an output end of the pretreatment system 5 is connected to an input end of the destabilization crystallizer 1 .

[0033] In this embodiment, the pretreatment system 5 removes suspended solids, colloids, COD and organic matter in the wastewater that have an impact on the subsequent membrane system and chemical reaction system to a lower level, making the wastewater turbidity less than 5NTU, thereby ensuring that the water treatment can proceed normally.

[0034] The implementation principle of the above embodiment is:

[0035] When the machine is first started, a large amount of calcium chloride is added to the destabilizing crystallizer 1 to increase the calcium ion concentration. The wastewater passes through the pretreatment system 5 to remove the suspended solids, colloids, COD and organic matter in the wastewater that affect the subsequent membrane system and chemical reaction system to a lower level, and then the wastewater enters the destabilizing crystallizer 1, and the fluoride ions react with the calcium ions to form calcium fluoride precipitation, which can be sold as a product. The defluorinated wastewater enters the filtration device 3 for filtration and then enters the nanofiltration membrane device 2 for salt separation. The concentrated water is mainly calcium chloride, which flows back to the destabilizing crystallizer 1 to replenish the calcium chloride in the destabilizing crystallizer 1. Therefore, in the subsequent water purification process, only a small amount of calcium chloride consumed by the calcium fluoride precipitation needs to be replenished in the destabilizing crystallizer 1, which reduces the consumption of calcium chloride. The water production end of the nanofiltration membrane device 2 is concentrated again by the reverse osmosis device 4, and then enters the evaporation crystallizer 6 to obtain high-purity sodium chloride, which can be sold as a product. In this process, the system is kept weakly acidic to prevent scaling after the calcium ions react with carbon dioxide in the air.

[0036] The embodiments of this specific implementation method are all preferred embodiments of the utility model, and are not intended to limit the protection scope of the utility model. Therefore, all equivalent changes made based on the structure, shape, and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A low-cost treatment system for sodium chloride type fluoride-containing wastewater, characterized in that: The invention comprises a destabilizing crystallizer (1), wherein a nanofiltration membrane device (2) is arranged on one side of the destabilizing crystallizer (1), the concentrated water end of the nanofiltration membrane device (2) is connected to the destabilizing crystallizer (1), the output end of the destabilizing crystallizer (1) is connected to a filtering device (3), the output end of the filtering device (3) is connected to the input end of the nanofiltration membrane device (2), the water production end of the nanofiltration membrane device (2) is connected to a reverse osmosis device (4), the output end of the reverse osmosis device (4) is connected to an evaporation crystallizer (6), and a pretreatment system (5) is arranged on one side of the destabilizing crystallizer (1), the output end of the pretreatment system (5) is connected to the input end of the destabilizing crystallizer (1).

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