CN113860608B

CN113860608B - Method and system for fractional separation, crystallization, recovery and recycling of high-salinity wastewater

Info

Publication number: CN113860608B
Application number: CN202010614316.5A
Authority: CN
Inventors: 杨本涛; 魏进超; 彭杰; 梁明华; 李佳
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2020-06-30
Filing date: 2020-06-30
Publication date: 2023-04-07
Anticipated expiration: 2040-06-30
Also published as: CN113860608A

Abstract

A method and a system for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater comprise the following steps: 1) Separating to obtain fluorine-chlorine wastewater: carrying out filtration treatment on the high-salinity wastewater by adopting a nanofiltration mode to obtain filtered fluorine-chlorine wastewater, wherein the residual part after filtration is miscellaneous salt wastewater containing sulfate radicals; 2) Separating to obtain fluoride crystals: the concentration of chloride ions in the fluorine-chlorine wastewater is improved, fluoride ions are crystallized and separated out to obtain fluoride crystals, and a high-chlorine mixed solution is remained; 3) Concentration gave a saturated chlorine-containing solution: carrying out over-concentration treatment on the high-chlorine mixed solution to obtain a saturated chlorine-containing solution and a fluorine-chlorine mixture; 4) Obtaining chloride crystal salt: crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt. The technical scheme provided by the application can reduce the investment of the precipitating agent and is simple to operate; the effect of fluorine-chlorine separation on high-salinity wastewater can be greatly improved.

Description

Method and system for fractional separation, crystallization, recovery and recycling of high-salinity wastewater

Technical Field

The invention relates to a high-salinity wastewater separation method, in particular to a method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater, belonging to the technical field of sintering wastewater treatment; the invention also relates to a fractional separation, crystallization, recovery and recycling system for the high-salinity wastewater.

Background

The high-salinity wastewater generally contains a large amount of fluorine, chlorine, sulfate and other compounds, has high concentration, complex components and large discharge amount, seriously influences the safety and the product quality of the industrial production process, and simultaneously can generate high toxic risk to the ecological environment.

Aiming at the treatment of high-salt wastewater, if an evaporation/concentration crystallization method is simply adopted, only low-value mixed salt can be obtained, resource utilization cannot be realized, the energy consumption is high, and the production cost is high. The idea of purification and recovery generally adopts a process route of 'defluorination, nanofiltration, freezing crystallization and evaporative crystallization', wherein the defluorination process generally adopts methods such as a precipitation method, an adsorption method, an ion exchange method, an electrodialysis method, chemical flocculation precipitation and the like to convert fluorine into other forms so as to realize the defluorination. The methods have different advantages and disadvantages and use conditions, and have the defects of complex operation, higher investment and low resource utilization rate in general. And sodium fluoride/potassium fluoride is an important chemical raw material and is widely used for chemical industry, metallurgy, wood preservatives and the like. At present, the main production methods of sodium fluoride/potassium fluoride comprise a melt leaching method, a neutralization method, a sodium fluosilicate method, an ion exchange method and the like. However, these methods require a higher concentration of fluoride ions, which is generally much higher than the concentration of the actual wastewater containing fluorine, and therefore, the wastewater containing fluorine in the prior art cannot be generally used for preparing and recovering sodium fluoride. Only a few patents and documents report methods for preparing recycled sodium fluoride using fluorine waste water, for example, chinese patent CN201710109272 reports a method for separating fluorine from waste water by adding a calcium-containing precipitant, a magnesium-containing precipitant, a sodium-containing precipitant, and an ammonium-or ammonia-containing precipitant to fluorine-containing waste water. However, the method has the defects of large medicament investment and complicated operation. Further innovation is needed.

Therefore, how to provide a method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater, which can reduce the investment of a precipitator and is simple to operate; the method can greatly improve the effect of fluorine-chlorine separation on high-salinity wastewater, and is a technical problem to be solved urgently by technical personnel in the field.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to reduce the investment of a precipitator and has simple operation; the method can greatly improve the fluorine-chlorine separation effect aiming at the high-salt wastewater, thereby being beneficial to the recovery of valuable substances, namely fluoride, chloride and sulfate in the process of treating the high-salt wastewater. The invention provides a method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater, which comprises the following steps: 1) Separating to obtain fluorine-chlorine wastewater: carrying out filtration treatment on the high-salinity wastewater by adopting a nanofiltration mode to obtain filtered fluorine-chlorine wastewater, wherein the residual part after filtration is miscellaneous salt wastewater containing sulfate radicals; 2) Separating to obtain fluoride crystals: the concentration of chloride ions in the fluorine-chlorine wastewater is improved, fluoride ions are crystallized and separated out to obtain fluoride crystals, and a high-chlorine mixed solution is remained; 3) Concentration gave a saturated chlorine-containing solution: carrying out over-concentration treatment on the high-chlorine mixed solution to obtain a saturated chlorine-containing solution and a fluorine-chlorine mixture; 4) Obtaining chloride crystal salt: crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt.

According to the first embodiment of the invention, a method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater is provided:

a method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater comprises the following steps: 1) Separating to obtain fluorine-chlorine wastewater: carrying out filtration treatment on the high-salinity wastewater by adopting a nanofiltration mode to obtain filtered fluorine-chlorine wastewater, wherein the residual part after filtration is miscellaneous salt wastewater containing sulfate radicals; 2) Separating to obtain fluoride crystals: increasing the concentration of chloride ions in the fluorine-chlorine wastewater, carrying out solid-liquid separation treatment, separating out fluorine ion crystals to obtain fluoride crystals, and remaining high-chlorine mixed solution; 3) Concentration to give a saturated chlorine-containing solution: carrying out overconcentration treatment on the high-chlorine mixed solution, and then carrying out solid-liquid separation treatment to obtain a saturated chlorine-containing solution and a fluorine-chlorine mixture; 4) Obtaining chloride crystal salt: crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt.

Preferably, the step 2) of increasing the concentration of the chloride ions in the fluorine-chlorine wastewater specifically comprises the following steps: introducing the fluorine-chlorine mixture obtained in the step 3) into a homogeneous dissolving tank, mixing with the fluorine-chlorine wastewater obtained in the step 1), and circulating in this way.

Preferably, the chloride crystal salt obtained in the step 4) is introduced into a homogeneous dissolving tank, mixed with the fluorine-chlorine wastewater in the step 1), and circulated in such a way.

Preferably, the concentration of the chlorine ions in the fluorine-chlorine wastewater is increased to the concentration C of the fluorine ions in the high fluorine-chlorine wastewater in the step 2) _F1 Comprises the following steps: 0 < C _F1 Is less than 15g/L. Preferably, the concentration of the chlorine ions in the fluorine-chlorine wastewater is increased to the concentration C of the fluorine ions in the high fluorine-chlorine wastewater in the step 2) _F1 Comprises the following steps: 0 < C _F1 < 12g/L. More preferably, the concentration of chlorine ions in the chlorofluorocarbon wastewater is increased to a high concentration C of fluorine ions in the chlorofluorocarbon wastewater in step 2) _F1 Comprises the following steps: 0 < C _F1 ＜10g/L。

Preferably, in the step 3), the concentration C of the fluorine ions in the high-chlorine mixed solution is monitored during the over-concentration treatment of the high-chlorine mixed solution _F2 (ii) a When C is present _F2 When the concentration is less than 0.1g/L, the concentration treatment is finished; preferably when C _F2 When the concentration is less than 0.05g/L, the concentration treatment is finished; more preferably when C _F2 When the concentration is less than 0.01g/L, the concentration treatment is completed.

Preferably, in step 3), the concentration of chloride ions in the high-chlorine mixed solution obtained in step 2) is detected and marked as C _{Cl mixture} g/L; controlling the volume multiple of the high-chlorine mixed solution subjected to concentration treatment to be X; wherein: x is 180/C _{Cl mixture} ～360/C _{Cl mixture} When it is preferable that X is 200/C _{Cl mixture} ～340/C _{Cl mixture} More preferably, X is 210/C _{Cl mixture} ～330/C _{Cl mixture} 。

Preferably, the concentration treatment in step 3) is any one or more of normal pressure heating concentration, reduced pressure distillation, heating evaporation, vacuum concentration, freeze concentration and membrane concentration.

Preferably, the method comprises the steps of: 5) Separating to obtain sulfate: freezing and crystallizing the mixed salt wastewater containing sulfate radicals obtained in the step 1), and then carrying out solid-liquid separation treatment to obtain sulfate crystals and mixed salt mother liquor; 6) And (4) introducing the mixed salt mother liquor into the high-salinity wastewater for cyclic treatment.

Preferably, the temperature T of the cold freezing crystallization treatment in the step 5) is-10 ℃ to 10 ℃; preferably T is-5 ℃ to 5 ℃; more preferably T is-5 ℃ to 0 ℃; freezing and crystallizing the mixed salt wastewater containing sulfate radical obtained in the step 1) to the concentration C of sulfate radical in the mixed salt mother liquor _{Sulfate radical} Comprises the following steps: 0 < C _{Sulfate radical} < 8g/L, preferably C _{Sulfate radical} Is 0 < C _{Sulfate radical} < 7g/L, more preferably C _{Sulfate radical} Is 0 < C _{Sulfate radical} ＜6g/L；。

Preferably, in the step 2), the step 3) and the step 5), one or more of centrifugal separation, gravity settling and filtration separation are adopted for solid-liquid separation.

Preferably, the crystallization treatment in step 4) and step 5) is one or more of evaporative crystallization, temperature-reduced crystallization, and freeze-dried crystallization.

Preferably, the high-salt wastewater is wastewater containing sulfate, fluoride and chloride which are easily soluble in water, or a mixture of wastewater containing sulfate, fluoride and chloride which are easily soluble in water.

Preferably, the high-salinity wastewater is one or more of wastewater containing sodium sulfate, sodium fluoride and sodium chloride, wastewater containing potassium sulfate, potassium fluoride and potassium chloride, and wastewater containing ammonium sulfate, ammonium fluoride and ammonium chloride.

Preferably, the step (a)In the step 3), the concentration degree of the wastewater is controlled according to the salt components in the fluorine-chlorine wastewater; the method comprises the following specific steps: when the fluorine-chlorine wastewater is wastewater containing sodium fluoride and sodium chloride, controlling the volume multiple of the high-chlorine mixed solution to be subjected to the over-concentration treatment to be 200/C _{Cl mixture} ～300/C _{Cl mixture} Preferably X is 230/C _{Cl mixture} ～260/C _{Cl mixture} (ii) a When the fluorine-chlorine wastewater is wastewater containing potassium fluoride and potassium chloride, the volume multiple of the high-chlorine mixed solution subjected to concentration treatment is controlled to be 180/C _{Cl mixture} ～270/C _{Cl mixture} Preferably X is 210/C _{Cl mixture} ～240/C _{Cl mixture} (ii) a When the fluorine-chlorine wastewater is wastewater containing ammonium fluoride and ammonium chloride, the volume multiple of the high-chlorine mixed solution subjected to concentration treatment is controlled to be X240/C _{Cl mixture} ～360/C _{Cl mixture} Preferably X is 270/C _{Cl mixture} ～330/C _Cl And (4) mixing.

Preferably, the sulfate concentration in the high-salt wastewater is greater than the fluoride ion concentration.

Preferably, the sulfate radical concentration is 0.05-100 g/L; the concentration of the fluorinion is 0.05 g/L-15 g/L; the concentration of the chloride ions is 0.01 g/L-150 g/L.

Preferably, in the step 1), the concentration multiple A of the high-salinity wastewater subjected to the filtration treatment by adopting a nanofiltration mode is 2-30 times; preferably, A is 3 to 10 times; more preferably, A is 4 to 9 times.

Preferably, the sulfate ion concentration of the sulfate-containing mixed salt wastewater is less than 300g/L; preferably less than 250g/L; more preferably less than 200g/L.

According to a second embodiment of the invention, a fractional separation, crystallization, recovery and recycling system for high-salinity wastewater is provided:

a high salinity wastewater fractional separation crystallization recovery and resource utilization system applying the method of the first embodiment, which comprises: a nano filter, a mixed dissolving and precipitating device, a solution concentrating and precipitating device and a solution crystallizing device; the original high-salinity wastewater pipeline is communicated with the liquid inlet of the nano filter, and the filtering outlet of the nano filter is communicated with the liquid inlet of the mixed dissolution and precipitation device; the liquid outlet of the mixed dissolution and precipitation device is communicated with the liquid inlet of the solution concentration and precipitation device; the liquid outlet of the solution concentration and precipitation device is communicated with the liquid inlet of the solution crystallization device; a solid outlet of the mixed dissolution and precipitation device discharges fluoride crystals, and a solid outlet of the solution concentration and precipitation device discharges a fluorine-chlorine mixture; discharging chloride crystal salt from solid outlet of solution crystallizing device

Preferably, the system further comprises: a solution freezing and crystallizing device; the mother liquor outlet of the nano filter is communicated with the liquid inlet of the solution freezing and crystallizing device; and a solid outlet of the solution freezing and crystallizing device discharges sulfate crystals.

Preferably, the liquid outlet of the solution freezing and crystallizing device is connected to the original high-salinity wastewater pipeline through a first circulating pipeline.

Preferably, a solid outlet of the solution concentration and precipitation device is communicated into the mixed dissolution and precipitation device through a second circulating pipeline.

Preferably, a solid outlet of the solution crystallization device is communicated into the mixed dissolution and precipitation device through a third circulating pipeline.

In the first embodiment of the application, the high-salinity wastewater is treated in a nanofiltration mode, and by utilizing the characteristic that a nanofiltration membrane selectively penetrates low-valence ions, fluorine ions and chlorine ions are separated from the high-salinity wastewater to obtain filtered fluorine-chlorine wastewater and filtered residual sulfate radical-containing miscellaneous salt wastewater. And then, controlling only fluorine ion crystallization to separate out by increasing the concentration of chloride ions in the fluorine-chlorine wastewater to obtain a fluoride crystal and high-chlorine mixed solution. Then concentrating the high-chlorine mixed solution to obtain a saturated chlorine-containing solution and a fluorine-chlorine mixture; and finally, crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt. In the present application, the homoionic effect between fluorine and chlorine ions is utilized, i.e. the higher the concentration of chlorine ions in the same solution, the lower the solubility of fluorine ions. That is, when the concentration of chloride ions in the solution is increased, fluoride ions are preferentially precipitated from the solution to obtain fluoride crystals. In the application of the invention, the chloride ions in the wastewater are controlled to be close to saturation in the process of increasing the chloride ion concentration of the fluorine-chlorine wastewater. The precipitated crystals are fluoride crystals. And finally, crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt. The technical scheme provided by the application reduces the investment of the precipitator and is simple to operate; the fluorine-chlorine separation effect of the high-salinity wastewater can be greatly improved, so that the recovery of valuable substances, namely fluoride and chloride in the process of treating the high-salinity wastewater is facilitated.

It should be noted that, the preferential separation of sulfate ions and fluorine and chlorine elements by means of nanofiltration is a distinguishing technical feature of the technical scheme provided by the present application, which is different from the prior art. Compared with the prior art that the fluorine element is preferentially separated, the quality of fluorine-chlorine separation in the later period can be effectively improved.

As shown in FIG. 2, the NaF solubility was nearly zero when the sodium chloride concentration exceeded 240g/L under the influence of the homoionic effect of fluorine and chlorine.

In one example of the first embodiment of the present application, the addition of the chlorofluoro mixture obtained in step 3) to the chlorofluoro waste water enables the increase of the concentration of chloride ions in the chlorofluoro waste water. Thereby being beneficial to the precipitation of fluoride crystal in the step 2). In the process of charging the fluorine-chlorine mixture, although the fluoride of the fluorine-chlorine mixture is dissolved in water at the beginning, as the concentration of the chlorine ion increases, all fluorine ions are precipitated finally, and fluoride crystals are obtained.

In another example of the first embodiment of the present application, the chloride crystal salt obtained in step 4) may be partially added to the chlorofluoro waste water obtained in step 1) in step 2), so as to simply increase the concentration of chloride ions in the chlorofluoro waste water. The amount of fluorine and chlorine to be charged can be controlled more favorably than the amount of fluorine and chlorine to be charged.

It should be noted that step 2) includes: by detecting the concentration C of fluorine ions _F To judge whether the chloride ions are nearly saturated or not, and when the chloride ions are saturated, the fluoride ions are completely precipitated from the solvent. Thus, the lower the concentration of fluoride ion detected, the closer the chloride ion is to saturation.

In the first embodiment of the present application, in the process of concentrating the high chlorine mixed solution in step 3), whether the concentration treatment is completed is judged by detecting the lowest value of the concentration of fluorine ions or the expansion factor of the concentration of chlorine ions in the solution. When crystals were precipitated in the solution and the fluoride ion concentration was close to 0, the remaining solution was judged to be a saturated chlorine-containing solution.

In step 3), the crystals are concentrated by stepwise cyclic evaporation, and the supersaturation of chloride ion in the wastewater is controlled to be increased, thereby increasing the salt concentration of the wastewater itself, so that all the fluoride and part of the chloride are crystallized and precipitated. The separated fluoride and chloride mixed salt is returned to the wastewater, and the fluoride is difficult to dissolve finally through repeated enrichment to obtain a supersaturated chloride solution, so that chloride crystal salt is obtained, and fluorine and chlorine separation is realized.

In the first embodiment of the present application, the concentration treatment of step 3) includes, but is not limited to, any one or more of atmospheric heating concentration, reduced pressure distillation, heating evaporation, vacuum concentration, freeze concentration, and membrane concentration.

In a first embodiment of the application, step 5) is carried out by subjecting the sulfate-containing waste brine to a freeze crystallization treatment. Because the solubility of the sodium sulfate is greatly changed along with the temperature, and the solubility of the fluorine chloride is basically unchanged along with the temperature, the crystallization and precipitation of the sodium sulfate can be realized by freezing and crystallizing the mixed salt wastewater containing the sulfate radical and consisting of high-concentration sulfate radical and low-concentration fluorine chloride, the solid is the sodium sulfate by further solid-liquid separation, and the liquid is the mixed salt mother liquor consisting of the fluorine chloride and a small amount of sulfate radical. In a preferred scheme, the mixed salt mother liquor is introduced into the high-salt wastewater through the step 6) and participates in the process flow again, so that the loss of substances to be recovered is prevented, and the separation effect of the method is improved.

The temperature of the freezing crystallization treatment is controlled within the range of-10 ℃ to 10 ℃, preferably T is-5 ℃ to 5 ℃; more preferably T is-5 ℃ to 0 ℃; can accelerate the separation of sodium sulfate in the crystallization process and improve the production efficiency.

In the first embodiment of the present application, step 2), step 3) and step 5) all precipitate solids, and the whole scheme involves solid-liquid separation treatment. The solid-liquid separation mode in the scheme provided by the application comprises but is not limited to one or more modes of centrifugal separation, gravity settling and filtration separation. And the crystallization treatment modes in the step 4) and the step 5) comprise but are not limited to one or more of evaporative crystallization, cooling crystallization and freeze drying crystallization. Different modes can be flexibly selected according to the requirements of the production process of the existing equipment.

In a first embodiment of the application, the high-salinity wastewater is filtered in the step 1) in a nanofiltration way, so that the unfiltered stock solution is concentrated to generate concentrated water; the concentration multiple A of the process is 2 to 30 times; preferably, A is 3 to 10 times; more preferably, A is 4 to 9 times.

In a second embodiment of the present application, a high salinity wastewater fractional separation crystallization recovery and resource utilization system comprises: a nano filter, a mixed dissolution and precipitation device, a solution concentration and precipitation device, a solution crystallization device and the like. And the devices are sequentially assembled into a whole system according to the process requirements. The system separates fluorine-chlorine wastewater from high-salinity wastewater through a nano filter. And (3) precipitating fluoride crystals in the fluorine-chlorine wastewater through a mixing, dissolving and precipitating device. Obtaining saturated chlorine-containing solution through a solution concentration and precipitation device. Finally, the chloride crystal salt is obtained through a solution crystallization device. The technical scheme that this application provided can improve and separate out fluoride crystallization and chloride crystal salt's efficiency from the high salt waste water.

In a second embodiment of the present application, the fractional separation, crystallization, recovery and recycling system for high salinity wastewater further comprises: a solution freezing and crystallizing device. And precipitating sulfate crystals from the miscellaneous salt wastewater containing sulfate by a solution freezing crystallization device.

It is further noted that in the prior art, the conventional high-salinity wastewater is subjected to fluoride removal and then sulfate and chloride ion separation and crystallization. Because the properties of fluorine and chlorine are relatively close, if the sulfate radical is not removed firstly, the fluorine and chlorine mixed wastewater can be obtained after the sulfate radical is separated. The traditional fluorine-chlorine wastewater evaporation adopts one-step evaporation without effective control, and only mixed crystal salt of fluorine and chlorine can be obtained. Therefore, the invention can also be said to control the conventional evaporation technology, and realizes the separation of fluorine and chlorine by combining the circulating crystallization with the re-dissolution concentration. Adopts the simplest adjustment, and can realize the separation of fluorine and chlorine without special equipment.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the technical scheme provided by the application, sulfate radical wastewater and fluorine-chlorine wastewater can be preferentially separated from high-salinity wastewater by using a nanofiltration mode, so that a foundation is laid for subsequent treatment, and the accuracy and speed of the integral fluorine-chlorine-sulfur separation are improved;

2. according to the technical scheme provided by the application, the process is simple to control, and the concentration of the chlorine element and the fluorine element can be quickly controlled by only detecting the concentration of the chlorine element and the fluorine element, so that fluoride crystals and chloride crystal salts can be obtained;

3. according to the technical scheme provided by the application, the conventional treatment mode is utilized, the wastewater is treated under the created method, and the initial investment cost of high-salinity wastewater treatment enterprises can be reduced.

4. The application provides a technical scheme, the in-process, the material that mainly utilizes self technology link to produce handles waste water, reduces extra additive demand to reduce the consumptive material cost among the high salt waste water treatment process.

Drawings

FIG. 1 is a flow chart of a method for fractional separation, crystallization, recovery and recycling of high-salt wastewater in the technical scheme of the invention;

FIG. 2 is a curve showing the variation of F ion concentration in a saturated NaF solution with the addition of NaCl;

FIG. 3 is a structural flow chart of a fractional separation, crystallization, recovery and recycling system for high-salinity wastewater in the technical scheme of the invention.

Reference numerals:

1: a nanofilter; 2: a mixing, dissolving and separating device; 3: a solution concentration and precipitation device; 4: a solution crystallization device; 5: a solution freezing and crystallizing device;

l0: an original high-salinity wastewater pipeline; l1: a first circulation pipe; l2: a second circulation pipe; l3: a third circulation conduit.

Detailed Description

a method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater comprises the following steps: 1) Separating to obtain fluorine-chlorine wastewater: carrying out filtration treatment on the high-salinity wastewater by adopting a nanofiltration mode to obtain filtered fluorine-chlorine wastewater, wherein the residual part after filtration is miscellaneous salt wastewater containing sulfate radicals; 2) Separating to obtain fluoride crystals: improving the concentration of chloride ions in the fluorine-chlorine wastewater through a homogenizing dissolving tank, carrying out solid-liquid separation treatment, separating out fluoride ions to obtain fluoride crystals, and remaining high-chlorine mixed solution; 3) Concentration gave a saturated chlorine-containing solution: carrying out overconcentration treatment on the high-chlorine mixed solution, and then carrying out solid-liquid separation treatment to obtain a saturated chlorine-containing solution and a fluorine-chlorine mixture; 4) Obtaining chloride crystal salt: crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt.

Preferably, the concentration of the chlorine ions in the fluorine-chlorine wastewater is increased to the degree C of the fluorine ions in the high fluorine-chlorine wastewater in the step 2) _F1 Comprises the following steps: 0 < C _F1 ＜15g/L。

Preferably, in step 3), the concentration of chloride ions in the high-chlorine mixed solution obtained in step 2) is detected and marked as C _{Cl mixture} g/L; controlling the volume multiple of the high-chlorine mixed solution subjected to concentration treatment to be X; wherein: x is 180/C _{Cl mixture} ～360/C _{Cl mixture} Preferably, X is 200/C _{Cl mixture} ～340/C _{Cl mixture} More preferably, X is 210/C _{Cl mixture} ～330/C _{Cl mixture} 。

Preferably, the method comprises the steps of: 5) Separating to obtain sulfate: freezing and crystallizing the sulfate radical-containing mixed salt wastewater obtained in the step 1), and then carrying out solid-liquid separation treatment to obtain sulfate crystals and mixed salt mother liquor; 6) And (4) introducing the mixed salt mother liquor into the high-salinity wastewater for cyclic treatment.

Preferably, the temperature T of the cold freezing crystallization treatment in the step 5) is-10 ℃ to 10 ℃; preferably T is-5 ℃ to 5 ℃; more preferably T is-5 ℃ to 0 ℃; freezing and crystallizing the mixed salt wastewater containing sulfate radical obtained in the step 1) to the concentration C of sulfate radical in the mixed salt mother liquor _{Sulfate radical} Comprises the following steps: 0 < C _{Sulfate radical} < 8g/L, preferably C _{Sulfate radical} Is 0 < C _{Sulfate radical} < 7g/L, more preferably C _{Sulfate radical} Is 0 < C _{Sulfate radical} ＜6g/L。

Preferably, the crystallization treatment in step 4) and step 5) is one or more of evaporative crystallization, crystallization at a reduced temperature, and freeze-drying crystallization.

Preferably, the concentration degree of the wastewater is controlled according to the salt content in the fluorine-chlorine wastewater in the step 3); the method specifically comprises the following steps:

when the fluorine-chlorine wastewater is wastewater containing sodium fluoride and sodium chloride, controlling the volume multiple of the high-chlorine mixed solution to be subjected to the over-concentration treatment to be 200/C _{Cl mixture} ～300/C _{Cl mixture} Preferably X is 230/C _{Cl mixture} ～260/C _{Cl mixture} ；

When the fluorine-chlorine wastewater is wastewater containing potassium fluoride and potassium chloride, the volume multiple of the high-chlorine mixed solution subjected to the over-concentration treatment is controlled to be X of 180/C _{Cl mixture} ～270/C _{Cl mixture} Preferably X is 210/C _{Cl mixture} ～240/C _{Cl mixture} ；

When the fluorine-chlorine wastewater is wastewater containing ammonium fluoride and ammonium chloride, the volume multiple of the high-chlorine mixed solution subjected to concentration treatment is controlled to be X240/C _{Cl mixture} ～360/C _{Cl mixture} Preferably X is 270/C _{Cl mixture} ～330/C _{Cl mixture} 。

Preferably, in the step 1), the concentration multiple A of the high-salinity wastewater subjected to filtration treatment in a nanofiltration mode is 2-30 times; preferably, A is 3 to 10 times; more preferably, A is 4 to 9 times.

a high salinity wastewater fractional separation crystallization recovery and resource utilization system applying the method of the first embodiment, which comprises: a nano filter 1, a mixed dissolution and precipitation device 2, a solution concentration and precipitation device 3 and a solution crystallization device 4; the original high-salinity wastewater pipeline L0 is communicated with the liquid inlet of the nano filter 1, and the filtering outlet of the nano filter 1 is communicated with the liquid inlet of the mixed dissolution and precipitation device 2; the liquid outlet of the mixed dissolution and precipitation device 2 is communicated with the liquid inlet of the solution concentration and precipitation device 3; the liquid outlet of the solution concentration and precipitation device 3 is communicated with the liquid inlet of the solution crystallization device 4; a solid outlet of the mixed dissolving and precipitating device 2 discharges fluoride crystals, and a solid outlet of the solution concentrating and precipitating device 3 discharges a fluorine-chlorine mixture; discharging chloride crystal salt from a solid outlet of the solution crystallizing device 4

Preferably, the system further comprises: a solution freezing and crystallizing device 5; the mother liquor outlet of the nano filter 1 is communicated with the liquid inlet of the solution freezing and crystallizing device 5; and a solid outlet of the solution freezing and crystallizing device 5 discharges sulfate crystals.

Preferably, the liquid outlet of the solution freezing and crystallizing device 5 is connected to the raw high-salinity wastewater pipeline L0 through a first circulating pipeline L1.

Preferably, the solid outlet of the solution concentration and precipitation device 3 is introduced into the mixed dissolution and precipitation device 2 through a second circulation pipeline L2.

Preferably, a solid outlet of the solution crystallization device 4 is communicated into the mixed dissolution and precipitation device 2 through a third circulating pipeline L3.

Example 1

Example 2

Example 1 was repeated except that the concentration of chloride ions in the chlorofluoro-waste water was increased in step 2) specifically as follows: introducing the fluorine-chlorine mixture obtained in the step 3) into a homogeneous dissolving tank, mixing with the fluorine-chlorine wastewater obtained in the step 1), and circulating in this way.

Example 3

Example 2 is repeated except that the chloride crystalline salt obtained in step 4) is introduced into the homogeneous dissolving tank and mixed with the fluorine-chlorine wastewater in step 1), and the circulation is carried out. Increasing the concentration of the chloride ions in the fluorine-chlorine wastewater to the concentration C of the fluoride ions in the high fluorine-chlorine wastewater in the step 2) _F1 Is less than 15g/L.

Example 4

Example 3 was repeated except that in step 3), the concentration C of fluorine ions in the high-chlorine mixed solution was monitored during the over-concentration treatment of the high-chlorine mixed solution _F2 (ii) a When C is _F2 When the concentration is less than 0.1g/L, the concentration treatment is completed.

Example 5

Example 4 was repeated except that in step 3), the concentration of chloride ions in the high-chlorine mixed solution obtained in step 2) was measured and designated as C _{Cl mixture} g/L; controlling the volume multiple of the high-chlorine mixed solution subjected to the concentration treatment to be X; wherein: x is 250/C _{Cl mixture} ～270/C _{Cl mixture} 。

Example 6

Example 5 was repeated except that the concentration treatment in step 3) was carried out by heating under atmospheric pressure.

Example 7

Example 6 was repeated except that the process included the following steps: 5) Separating to obtain sulfate: freezing and crystallizing the mixed salt wastewater containing sulfate radicals obtained in the step 1), and then carrying out solid-liquid separation treatment to obtain sulfate crystals and mixed salt mother liquor; 6) And (4) introducing the mixed salt mother liquor into the high-salinity wastewater for circular treatment.

Example 8

Example 7 was repeated, except that the temperature T of the cold-frozen crystallization treatment in step 5) was-3 ℃; freezing and crystallizing the mixed salt wastewater containing sulfate radical obtained in the step 1) to the concentration C of sulfate radical in the mixed salt mother liquor _{Sulfate radical} Comprises the following steps: 0 < C _{Sulfate radical} ＜8g/L。

Example 9

Example 8 was repeated except that solid-liquid separation was carried out by filtration separation in step 2), step 3) and step 5).

Example 10

Example 9 was repeated except that the way of the crystallization treatment in step 4) and step 5) was evaporative crystallization.

Example 11

Example 10 was repeated except that the high-salt wastewater was wastewater containing sulfate, fluoride and chloride salts which were easily soluble in water.

Example 12

Example 10 was repeated except that the high-salt wastewater was a mixture of wastewater containing sulfate salt, fluoride salt and chloride salt, which are easily soluble in water.

Example 13

Example 10 was repeated except that the high-salt wastewater was a mixture of wastewater containing sodium sulfate, sodium fluoride and sodium chloride, wastewater containing potassium sulfate, potassium fluoride and potassium chloride, and wastewater containing ammonium sulfate, ammonium fluoride and ammonium chloride.

Example 14

Example 10 was repeated except that the concentration degree of the wastewater was controlled according to the salt content in the chlorofluoro wastewater in step 3); the method comprises the following specific steps: when the fluorine-chlorine wastewater is wastewater containing sodium fluoride and sodium chloride, the volume multiple of the high-chlorine mixed solution subjected to concentration treatment is controlled to be 200/C _{Cl mixture} ～300/C _{Cl mixture} In this case, the concentration treatment is completed.

Example 15

Example 10 was repeated except that the concentration degree of the wastewater was controlled according to the salt content in the chlorofluoro wastewater in step 3); the method comprises the following specific steps: when the fluorine-chlorine wastewater is wastewater containing potassium fluoride and potassium chloride, the concentration multiple X of chloride ions is controlled to be 180/C _{Cl mixture} ～270/C _{Cl mixture} When the concentration is completed, the concentration treatment is completed.

Example 16

Example 10 was repeated except that the concentration degree of the wastewater was controlled according to the salt content in the fluorine-chlorine wastewater in step 3); the method specifically comprises the following steps: when the fluorine-chlorine wastewater is wastewater containing ammonium fluoride and ammonium chloride, the concentration multiple X of chloride ions is controlled to be 240/C _{Cl mixture} ～360/C _{Cl mixture} When the utility model is used, the water is discharged,the concentration treatment is completed.

Example 17

Example 10 was repeated except that the sulfate concentration in the high-salt wastewater was greater than the fluoride ion concentration.

Example 18

Example 10 is repeated, except that the sulfate concentration is from 0.05 to 100g/L; the concentration of the fluorinion is 0.05 g/L-15 g/L; the concentration of the chloride ions is 0.01 g/L-150 g/L.

Example 19

Example 18 is repeated except that in step 1), the concentration multiple A of the high-salinity wastewater filtered by adopting a nanofiltration mode is 2 to 30 times; preferably, A is 3 to 10 times; more preferably, A is 4 to 9 times.

Example 20

Example 19 is repeated, except that the sulfate ion concentration of the sulfate-containing heterosalt wastewater is less than 180g/L.

Example 21

A fractional separation, crystallization, recovery and recycling system for high-salinity wastewater by applying the method of the embodiment 5 comprises the following components: a nano filter 1, a mixed dissolution and precipitation device 2, a solution concentration and precipitation device 3 and a solution crystallization device 4; the original high-salinity wastewater pipeline L0 is communicated with the liquid inlet of the nano filter 1, and the filtering outlet of the nano filter 1 is communicated with the liquid inlet of the mixed dissolution and precipitation device 2; the liquid outlet of the mixed dissolution and precipitation device 2 is communicated with the liquid inlet of the solution concentration and precipitation device 3; the liquid outlet of the solution concentration and precipitation device 3 is communicated with the liquid inlet of the solution crystallization device 4; a solid outlet of the mixed dissolving and precipitating device 2 discharges fluoride crystals, and a solid outlet of the solution concentrating and precipitating device 3 discharges a fluorine-chlorine mixture; discharging chloride crystal salt from a solid outlet of the solution crystallizing device 4

Example 22

Example 21 is repeated except that the system further comprises: a solution freezing and crystallizing device 5; the mother liquor outlet of the nano filter 1 is communicated with the liquid inlet of the solution freezing and crystallizing device 5; and a solid outlet of the solution freezing and crystallizing device 5 discharges sulfate crystals.

Example 23

Example 22 was repeated except that the outlet of the solution freezing and crystallizing device 5 was connected to the raw high-salinity wastewater line L0 via the first circulating line L1.

Example 24

Example 23 was repeated except that the solid outlet of the solution concentration and precipitation unit 3 was opened to the mixed solution precipitation unit 2 through the second circulation line L2.

Example 25

Example 14 was repeated except that the solid outlet of the solution crystallizing device 4 was passed into the mixed solution precipitating device 2 through the third circulating line L3.

Experiment 1

Experiments are carried out according to the method for fractional separation, crystallization, recovery and resource utilization of the high-salinity wastewater provided by the application. The experiment was started after the concentrations of chloride, fluoride and sulfate ions in the high-salinity wastewater obtained in the process were determined.

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Claims

1. A method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater is characterized by comprising the following steps:

1) Separating to obtain fluorine-chlorine wastewater: carrying out filtration treatment on the high-salinity wastewater by adopting a nanofiltration mode to obtain filtered fluorine-chlorine wastewater, wherein the residual part after filtration is miscellaneous salt wastewater containing sulfate radicals;

2) Separating to obtain fluoride crystals: improving the concentration of chloride ions in the fluorine-chlorine wastewater through a homogenizing dissolving tank, carrying out solid-liquid separation treatment, separating out fluoride ions to obtain fluoride crystals, and remaining high-chlorine mixed solution;

3) Concentration gave a saturated chlorine-containing solution: carrying out over-concentration treatment on the high-chlorine mixed solution, and then carrying out solid-liquid separation treatment to obtain a saturated chlorine-containing solution and a fluorine-chlorine mixture;

4) Obtaining chloride crystal salt: crystallizing the saturated chlorine-containing solution to obtain chloride crystal salt;

the step 2) of improving the concentration of chloride ions in the fluorine-chlorine wastewater specifically comprises the following steps: introducing the fluorine-chlorine mixture obtained in the step 3) into a homogeneous dissolving tank, mixing with the fluorine-chlorine wastewater obtained in the step 1), and circulating in the same way; and/or

Introducing the chloride crystal salt obtained in the step 4) into a homogeneous dissolving tank, mixing with the fluorine-chlorine wastewater obtained in the step 1), and circulating in the same way;

the high-salinity wastewater is one or two of wastewater containing sodium sulfate, sodium fluoride and sodium chloride and wastewater containing ammonium sulfate, ammonium fluoride and ammonium chloride.

2. The method for fractional separation, crystallization, recovery and resource utilization of high salinity wastewater according to claim 1, wherein the concentration of chloride ions in the chlorofluoro wastewater is increased to the concentration C of fluoride ions in the high salinity wastewater in step 2) _F1 Comprises the following steps: 0 < C _F1 Less than 15g/L; and/or

In the step 3), the concentration C of the fluorinion in the high-chlorine mixed solution is monitored during the process of the over-concentration treatment of the high-chlorine mixed solution _F2 (ii) a When C is present _F2 When less than 0.1g/L, the concentration treatment is completed and/or

In the step 3), the concentration of chloride ions in the high-chlorine mixed solution obtained in the step 2) is detected and marked as C _{Cl mixture} g/L; controlling the volume multiple of the high-chlorine mixed solution subjected to concentration treatment to be X; wherein: x is 180/C _{Cl mixture} ～360/C _{Cl mixture} 。

3. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater according to claim 2, characterized in that when C is reached _F2 When the concentration is less than 0.05g/L, the concentration treatment is finished; and/or

X is 200/C _{Cl mixture} ～340/C _{Cl mixture} 。

4. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater as claimed in claim 3, wherein when C is _F2 When the concentration is less than 0.01g/L, the concentration treatment is finished; and/or

X is 210/C _{Cl mixture} ～330/C _{Cl mixture} 。

5. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater according to any one of claims 1 to 4, wherein the concentration treatment in step 3) is any one or more of atmospheric heating concentration, reduced pressure distillation, heating evaporation, vacuum concentration, freezing concentration and membrane concentration.

6. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater according to any one of claims 1 to 4, characterized in that the method comprises the following steps:

5) Separating to obtain sulfate: freezing and crystallizing the sulfate radical-containing mixed salt wastewater obtained in the step 1), and then carrying out solid-liquid separation treatment to obtain sulfate crystals and mixed salt mother liquor;

6) And (4) introducing the mixed salt mother liquor into the high-salinity wastewater for cyclic treatment.

7. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater as claimed in claim 6, wherein the temperature T of the cold freezing crystallization treatment in the step 5) is-10 ℃ to 10 ℃; freezing and crystallizing the mixed salt wastewater containing sulfate radical obtained in the step 1) to the concentration C of sulfate radical in the mixed salt mother liquor _{Sulfate radical} Comprises the following steps: 0 < C _{Sulfate radical} Less than 8g/L; and/or

Performing solid-liquid separation in one or more of centrifugal separation, gravity settling and filtration separation in the step 2), the step 3) and the step 5); the crystallization treatment in the step 4) and the step 5) is one or more of evaporative crystallization, cooling crystallization and freeze drying crystallization.

8. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater according to claim 7, characterized in that T is-5 ℃ to 5 ℃; c _{Sulfate radical} Is 0 < C _{Sulfate radical} ＜7g/L。

9. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater according to claim 8, characterized in that T is-5 ℃ to 0 ℃; c _{Sulfate radical} Is 0 < C _{Sulfate radical} ＜6g/L。

10. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater as claimed in claim 1, wherein in step 3), the concentration degree of the wastewater is controlled according to the salt content in the fluorine-chlorine wastewater; the method specifically comprises the following steps:

when the fluorine-chlorine wastewater is wastewater containing sodium fluoride and sodium chloride, the volume multiple of the high-chlorine mixed solution subjected to concentration treatment is controlled to be 200/C _{Cl mixture} ～300/C _{Cl mixture} ；

When the fluorine-chlorine wastewater is wastewater containing ammonium fluoride and ammonium chloride, the volume multiple of the high-chlorine mixed solution subjected to concentration treatment is controlled to be 240/C _{Cl mixture} ～360/C _{Cl mixture} 。

11. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater as claimed in claim 10, wherein when the fluorine-chlorine wastewater is wastewater containing sodium fluoride and sodium chloride, the volume multiple X of the concentrated high-salinity mixed solution is controlled to be 230/C _{Cl mixture} ～260/C _{Cl mixture} ；

When the fluorine-chlorine wastewater is wastewater containing ammonium fluoride and ammonium chloride, the volume multiple X of the high-chlorine mixed solution subjected to concentration treatment is controlled to be 270/C _{Cl mixture} ～330/C _{Cl mixture} 。

12. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater according to claim 10 or 11, characterized in that the sulfate concentration in the high-salinity wastewater is greater than the fluoride ion concentration.

13. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater as claimed in claim 12, wherein the concentration of sulfate radicals is 0.05-100 g/L; the concentration of the fluorinion is 0.05 g/L-15 g/L; the concentration of the chloride ions is 0.01 g/L-150 g/L.

14. The method for fractional separation, crystallization, recovery and recycling of high-salinity wastewater according to any one of claims 1 to 4, 7 to 11 and 13, characterized in that in the step 1), the concentration multiple A of the high-salinity wastewater filtered by nanofiltration is 2 to 30 times; the concentration of sulfate ions in the sulfate radical-containing mixed salt wastewater is less than 300g/L.

15. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater according to claim 14, characterized in that A is 3-10 times; the concentration of sulfate ions in the sulfate radical-containing mixed salt wastewater is less than 250g/L.

16. The method for fractional separation, crystallization, recovery and resource utilization of high-salinity wastewater according to claim 15, characterized in that A is 4-9 times; the concentration of sulfate ions in the sulfate radical-containing mixed salt wastewater is less than 200g/L.

17. A high-salinity wastewater fractional separation, crystallization, recovery and recycling system applying the high-salinity wastewater fractional separation, crystallization, recovery and recycling method of any one of claims 1 to 16, characterized in that the system comprises: a nano filter (1), a mixed dissolution and precipitation device (2), a solution concentration and precipitation device (3) and a solution crystallization device (4); the original high-salinity wastewater pipeline (L0) is communicated with the liquid inlet of the nano filter (1), and the filtering outlet of the nano filter (1) is communicated with the liquid inlet of the mixed dissolution and precipitation device (2); the liquid outlet of the mixed dissolution and precipitation device (2) is communicated with the liquid inlet of the solution concentration and precipitation device (3); the liquid outlet of the solution concentration and precipitation device (3) is communicated with the liquid inlet of the solution crystallization device (4); a solid outlet of the mixed dissolving and separating device (2) discharges fluoride crystals, and a solid outlet of the solution concentrating and separating device (3) discharges a fluorine-chlorine mixture; the solid outlet of the solution crystallization device (4) discharges chloride crystal salt.

18. The high salinity wastewater fractional separation crystallization recovery and resource system of claim 17, wherein the system further comprises: a solution freezing and crystallizing device (5); a mother liquor outlet of the nano filter (1) is communicated with a liquid inlet of the solution freezing and crystallizing device (5); and a solid outlet of the solution freezing and crystallizing device (5) discharges sulfate crystals.

19. The high-salinity wastewater fractional separation, crystallization, recovery and resource system according to claim 18, wherein the liquid outlet of the solution freezing and crystallizing device (5) is connected to the original high-salinity wastewater pipeline (L0) through a first circulation pipeline (L1).

20. The high-salinity wastewater fractional-separation, crystallization, recovery and recycling system according to any one of claims 17 to 19, characterized in that the solid outlet of the solution concentration and precipitation device (3) is communicated into the mixed dissolution and precipitation device (2) through a second circulation pipeline (L2); and/or

And a solid outlet of the solution crystallization device (4) is introduced into the mixed dissolution precipitation device (2) through a third circulating pipeline (L3).