System and method for refining and purifying potassium and sodium salts from fly ash water washing liquid

Abstract

The invention belongs to the technical field of environmental protection, and relates to a system and a method for refining and purifying potassium and sodium salts from fly ash water washing liquid, the system comprises a sodium salt purification unit, a potassium salt purification unit and a potassium ion online analyzer; the sodium salt purification unit comprises a preheater, an evaporation crystallizer, a first thickener and a first centrifugal machine which are connected in sequence; the potassium salt purification unit comprises a cooling crystallizer and a second centrifugal machine which are connected in sequence, and the cooling crystallizer is connected with the first thickener; and the potassium ion online analyzer is arranged on the evaporation crystallizer. According to the system for refining and purifying the potassium and sodium salts from the fly ash water washing liquid, the content of impurities in the potassium and sodium salts refined and purified from the fly ash water washing liquid can be remarkably reduced, the problem that the purity of the potassium and sodium salts extracted from the fly ash water washing liquid is not high is solved, and a technical support is provided for popularization and application of a cement kiln co-processing fly ash water washing technology.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, and specifically relates to a system and method for refining and purifying potassium and sodium salts from fly ash washing liquid. Background Technology

[0002] Municipal solid waste incineration fly ash (hereinafter referred to as fly ash) is a solid powder collected by the flue gas purification system of municipal solid waste incineration power plants. Due to its high concentration of heavy metals, dioxins, and other toxic and harmful components, it is classified as hazardous waste (No. HW18) in my country's National Hazardous Waste List. Traditionally, fly ash is disposed of through landfill, but landfilling cannot completely eliminate the toxic substances and salts in the fly ash, resulting in severe secondary pollution. Water-washing-based co-processing in cement kilns is a new fly ash disposal technology independently developed in my country in recent years. It offers advantages such as thorough disposal, no secondary pollution, and resource utilization, and has now become one of the mainstream technologies for fly ash treatment.

[0003] The cement kiln co-processing technology based on water washing removes harmful substances such as chlorine, potassium, and sodium from fly ash, significantly increasing the amount of fly ash fed into the kiln. However, the treatment of the fly ash washing liquid containing potassium, sodium, and chlorine has become a problem. Mechanical vapor recompression (MVR) technology is generally used for evaporation and desalination of the fly ash washing liquid, but the resulting crystalline salt is a mixed salt (mainly containing sodium chloride and potassium chloride). This mixed salt has low utilization value and is difficult to market, creating a major obstacle to the application and promotion of cement kiln co-processing fly ash washing technology. Therefore, there is a strong and urgent need for refining and purifying the mixed salt to achieve high-value utilization. Furthermore, in recent years, the global demand for potassium salts has been gradually increasing; sodium chloride, as an important raw material in industrial production, is also in high demand, while fly ash contains high levels of potassium chloride and sodium chloride. Therefore, the recovery of potassium and sodium resources from fly ash is of significant practical importance.

[0004] In existing technologies, the sodium chloride and potassium chloride salts obtained from the treatment and separation of fly ash washing liquid have low purity and contain many impurities, such as KCl and SO4 in the sodium chloride salt. 2- Potassium chloride salts contain NaCl and SO4. 2- Further issues to be addressed include how to reduce the impurity content in sodium chloride and potassium chloride salts. Summary of the Invention

[0005] The main objective of this invention is to overcome the problem that the separation of sodium chloride and potassium chloride salts by fly ash washing liquid in the prior art results in a large number of impurities and low purity, and to provide a system and method for refining and purifying potassium and sodium salts from fly ash washing liquid.

[0006] To achieve the above objectives, the specific technical solution is as follows: This invention provides a system for refining and purifying potassium and sodium salts from fly ash washing liquid, including a sodium salt purification unit, a potassium salt purification unit, and an online potassium ion analyzer; The sodium salt purification unit includes a preheater, an evaporator crystallizer, a first thickener, and a first centrifuge connected in sequence. The potassium salt purification unit includes a cooling crystallizer and a second centrifuge connected in sequence, and the cooling crystallizer is connected to the first thickener. The online potassium ion analyzer is installed on the evaporator crystallizer.

[0007] In existing technologies, sodium chloride salts contain a relatively high amount of potassium chloride because potassium chloride is often in a saturated or supersaturated state within the evaporator crystallizer. Potassium chloride precipitates out during this process and is then separated from sodium chloride by centrifugation, thus limiting the purity of the sodium chloride salt. Furthermore, during the separation of sodium chloride and potassium chloride, both sodium chloride and potassium chloride salts contain a certain amount of SO4. 2- This also limits the purity of these two salts.

[0008] The fly ash washing liquid refining and purification system for potassium and sodium salts provided by this invention adds an online potassium ion analyzer to the evaporator crystallizer to detect the concentration of potassium ions in the high-temperature feed liquid of the evaporator crystallizer, thereby determining the potassium chloride content in the high-temperature feed liquid of the evaporator crystallizer. At the three-phase co-saturation point of potassium chloride, sodium chloride, and water, the feed liquid in the evaporator crystallizer is discharged into the first thickener. In the evaporator crystallizer, sodium chloride first reaches saturation concentration and begins to precipitate. As evaporation proceeds, the potassium chloride concentration continuously increases. Due to the common ion effect, the sodium chloride concentration in the solution continuously decreases, but it is still saturated. When the potassium chloride concentration is close to or just reaches saturation, it is the three-phase co-saturation point of potassium chloride, sodium chloride, and water. When the potassium chloride content is close to or equal to 21.7% at 100°C, the feed liquid in the evaporator crystallizer is discharged into the first thickener. The liquid discharged into the first thickener is concentrated after natural sedimentation and then enters the first centrifuge for separation, thereby significantly reducing the potassium salt content in the separated sodium salt. The centrifuged sodium salt is washed to further remove impurities from the sodium chloride, thus obtaining high-purity sodium chloride. The supernatant from the first thickener of the sodium salt purification unit flows by gravity to the cooling crystallizer of the potassium salt purification unit. The cooled liquid then enters the second centrifuge for centrifugal separation to obtain high-purity potassium chloride.

[0009] Therefore, the fly ash washing liquid refining and purification potassium and sodium salt system of the present invention can significantly reduce the impurity content in the fly ash washing liquid refining and purification potassium and sodium salt, solve the problem of low purity of potassium and sodium salt extracted from fly ash washing liquid, and provide technical support for the promotion and application of fly ash washing technology in cement kilns.

[0010] Furthermore, the fly ash washing liquid refining and purification system for potassium and sodium salts also includes a second thickener, which is disposed between the cooling crystallizer and the second centrifuge.

[0011] This invention adds a second thickener between the cooling crystallizer and the second centrifuge, which effectively improves the solid-liquid separation effect, making the concentration of material entering the second centrifuge more suitable and avoiding the problem of reduced centrifuge separation efficiency due to excessively low material concentration. At the same time, the second thickener can buffer and store the material, ensuring continuous operation of the system when the second centrifuge experiences a brief malfunction or needs maintenance, reducing production interruptions caused by equipment failure, and improving the stability and reliability of the entire system. In addition, the operation of the second thickener is relatively simple and the maintenance cost is low, without placing too much additional burden on the system. Thus, while ensuring the purification effect, it reduces production costs and improves the overall economic benefits of the system.

[0012] Furthermore, the evaporator crystallizer is a forced circulation evaporator crystallizer.

[0013] Forced circulation evaporator crystallizer can enhance the circulation of the liquid within the evaporator crystallizer, accelerate the evaporation of water in the liquid, and ensure that the liquid is heated evenly within the evaporator crystallizer. This effectively avoids local overheating or uneven crystallization, thereby improving the efficiency and quality of evaporation crystallization, ensuring a more stable and reliable separation effect, and further enhancing the purity of the final sodium chloride and potassium chloride salts obtained.

[0014] Furthermore, the first centrifuge is a centrifuge with online washing and separation functions, such as a multi-cone sedimentation filter centrifuge.

[0015] The first centrifuge of the present invention has online washing and separation functions. Washing liquid is added in real time during the salt separation process to effectively remove impurities from the salt product, thereby improving the purity of sodium salt. At the same time, the short-process online washing and separation can improve production efficiency and reduce production costs.

[0016] Furthermore, the fly ash washing liquid refining and purification system for potassium and sodium salts also includes a second mother liquor tank. The inlet pipe of the second mother liquor tank is connected to the second centrifuge, and the outlet pipe of the second mother liquor tank is connected to the calcium ion tank. The calcium ion tank can store the fly ash washing water containing a high concentration of calcium ions obtained after solid-liquid separation.

[0017] In this invention, the solution in the second mother liquor tank is rich in SO4. 2- Impurities are removed by connecting the second mother liquor tank to the calcium ion tank, allowing it to chemically react with the high-concentration calcium ion solution produced during fly ash washing solid-liquid separation, generating calcium sulfate precipitate, thereby removing most of the enriched SO4. 2-The calcium sulfate-containing precipitate produced can be returned to the fly ash washing system. After solid-liquid separation, it enters the cement kiln for treatment and is removed from the system, thereby further increasing the purity of the separated sodium chloride and potassium chloride salts and realizing the deep purification of potassium and sodium salts from fly ash washing liquid.

[0018] Furthermore, the second centrifuge is a horizontal screw centrifuge or a piston pusher centrifuge.

[0019] Horizontal screw centrifuges have high separation efficiency and are suitable for separating liquids with low solid content. They can complete the separation of large quantities of materials in a short time, effectively improving separation capacity and resulting in low water content in potassium chloride salts, further improving the purity of potassium salts. At the same time, horizontal screw centrifuges operate stably with a low failure rate, reducing maintenance frequency and downtime, thereby ensuring the continuity and stability of production.

[0020] Furthermore, the fly ash washing liquid refining and purification system for potassium and sodium salts also includes a first mother liquor tank, the inlet pipe of which is connected to the first centrifuge, and the outlet pipe of which is connected to the evaporator crystallizer.

[0021] The present invention includes a first mother liquor tank, into which the liquid separated by the first centrifuge is fed and then pumped to an evaporator crystallizer for evaporation treatment, thereby recovering potassium and sodium salt components and improving the overall purification efficiency of potassium and sodium salts.

[0022] Furthermore, the cooling crystallizer is a jacketed enamel-lined autoclave.

[0023] The cooling crystallizer jacket is circulated with relatively constant temperature water, which can better control the temperature during the crystallization process, ensure the stability of the crystallization environment, and help improve the quality and purity of potassium and sodium salt crystals. The enamel material has excellent corrosion resistance and can resist the erosion of various chemicals in fly ash washing liquid, extend the service life of the equipment, reduce equipment replacement costs, and thus further improve the overall economic benefits of the system.

[0024] A method for refining and purifying potassium and sodium salts from fly ash washing liquid, using the above-mentioned system for refining and purifying potassium and sodium salts from fly ash washing liquid.

[0025] Specifically, it includes the following steps: (1) After the fly ash washing liquid is preheated by the preheater, it enters the evaporator crystallizer for treatment. The potassium chloride content of the fly ash washing liquid in the evaporator crystallizer is analyzed by the online potassium ion analyzer. When the evaporation crystallization temperature is 100℃ and the potassium chloride content is 20.7-21.7%, the liquid in the evaporator crystallizer is discharged into the first thickener. (2) The concentrated liquid after natural settling in the first thickener enters the first centrifuge for washing and centrifugation to obtain sodium chloride salt; (3) The supernatant of the first thickener flows by gravity to the cooling crystallizer to cool down. After cooling, the liquid is concentrated and then enters the second centrifuge for centrifugal separation to obtain potassium chloride salt. Preferably, the solution after washing and separation in the first centrifuge is sent to an evaporator crystallizer for evaporation treatment; the solution after separation in the second centrifuge is sent to a calcium ion tank, where it reacts chemically with a calcium ion solution to generate calcium sulfate precipitate, thus removing the enriched SO4. 2- .

[0026] Furthermore, the fly ash washing liquid is pretreated by filtering to separate particulate matter from the fly ash washing liquid and by adding sodium carbonate or sodium sulfate solution to remove calcium ions from the fly ash washing liquid.

[0027] Pretreatment of fly ash washing solution can effectively remove impurities such as calcium ions, preventing calcium ion precipitation and scaling during the evaporation process of fly ash washing solution, which would affect evaporation efficiency.

[0028] Further, in step (1), the fly ash washing liquid enters the preheater and is preheated to 95-100°C before entering the evaporator crystallizer for treatment; And / or, in step (3), the liquid in the cooling crystallizer is cooled to 40-50°C.

[0029] The fly ash washing liquid is preheated to near the evaporation temperature of the evaporator crystallizer by the preheater, and can evaporate rapidly after entering the evaporator crystallizer, thus improving the evaporation efficiency. The liquid in the cooling crystallizer is cooled to 40-50℃, which is more conducive to the precipitation of potassium salt and improves the crystallization efficiency.

[0030] Furthermore, the washing liquid introduced into the first centrifuge is pretreated fly ash washing liquid, clean water, or a saturated sodium chloride solution.

[0031] In one specific embodiment of the invention, the method for refining and purifying potassium and sodium salts from fly ash washing liquid includes the following steps: 1) Pretreatment of fly ash washing solution; 2) The pretreated fly ash washing liquid enters the preheater and is preheated to 95°C before entering the evaporator crystallizer for processing. The evaporation and crystallization temperature is 100°C. The potassium chloride content of the fly ash washing liquid in the evaporator crystallizer is analyzed by an online potassium ion analyzer. When the potassium chloride content is 21.7%, the liquid in the evaporator crystallizer is discharged into the first thickener. 3) The concentrated liquid after natural sedimentation in the first thickener enters the first centrifuge for separation. At the same time, a saturated sodium chloride solution is introduced into the first centrifuge as a washing liquid to wash the sodium salt during centrifugation. Sodium chloride salt is obtained after centrifugation in the first centrifuge. 4) The supernatant of the first thickener flows by gravity into the cooling crystallizer. Circulating water is used as the cooling medium to cool the liquid in the cooling crystallizer. After the liquid is cooled to 40°C, it enters the second thickener for concentration. When the solid accounts for 40%-60% of the volume of the liquid, the concentrated liquid enters the second centrifuge for centrifugal separation to obtain potassium chloride salt. 5) The solution after washing and separation in the first centrifuge enters the first mother liquor tank and is then sent to the evaporator crystallizer for evaporation treatment; 6) The solution separated by the second centrifuge enters the second mother liquor tank, and is then sent to the calcium ion tank, where it reacts chemically with the calcium ion solution to form calcium sulfate precipitate, removing the enriched SO4. 2- .

[0032] This invention achieves efficient separation and purification of potassium and sodium salts by controlling the temperature and concentration at each stage.

[0033] Compared with the prior art, the present invention has the following significant advantages: (1) The system for refining and purifying potassium and sodium salts from fly ash washing liquid of the present invention analyzes the potassium chloride content in the high-temperature liquid in the evaporator crystallizer, so that the potassium chloride is in an unsaturated or just saturated state and the sodium chloride is in a saturated state and is discharged into the first thickener. Then, sodium chloride salt is obtained by online washing and centrifugation. At the same time, the supernatant of the first thickener is cooled and centrifuged to obtain potassium chloride salt, thereby achieving a more thorough separation of potassium and sodium salts in fly ash washing liquid.

[0034] (2) The present invention removes most of the SO4 from sodium chloride salt by washing and separating it. 2－ Impurities, while refining and purifying the fly ash washing liquid to remove most of the SO4 enriched in the potassium and sodium salt system. 2－ The sodium chloride and potassium chloride salts are removed from the system by generating calcium sulfate precipitate, thereby further increasing the purity of the separated sodium chloride and potassium chloride salts and realizing the deep purification of potassium and sodium salts from fly ash washing liquid. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a flow chart of the system for refining and purifying potassium and sodium salts from fly ash washing liquid in Embodiment 1 of the present invention; Figure 2 This is a flow chart of the system for refining and purifying potassium and sodium salts from fly ash washing liquid in Embodiment 2 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] Example 1 like Figure 1 As shown, this embodiment provides a system for refining and purifying potassium and sodium salts from fly ash washing liquid, including a sodium salt purification unit, a potassium salt purification unit, and an online potassium ion analyzer; The sodium salt purification unit includes a preheater, an evaporator crystallizer, a first thickener, a first centrifuge, and a first mother liquor tank connected in sequence. The first mother liquor tank is connected to the evaporator crystallizer. The evaporator crystallizer is a forced circulation evaporator crystallizer; the first centrifuge is a multi-cone sedimentation filter centrifuge.

[0039] The potassium salt purification unit includes a cooling crystallizer, a second centrifuge, a second mother liquor tank, and a calcium ion tank connected in sequence. The cooling crystallizer is connected to the first thickener. The cooling crystallizer is a jacketed enamel-lined kettle, and the second centrifuge is a horizontal screw centrifuge. The calcium ion tank stores the fly ash washing water containing a high concentration of calcium ions, obtained after solid-liquid separation.

[0040] The online potassium ion analyzer is installed on the evaporator crystallizer.

[0041] This embodiment provides a method for refining and purifying potassium and sodium salts from fly ash washing liquid. Using the aforementioned fly ash washing liquid refining and purification system for potassium and sodium salts, the method includes the following steps: (1) Pretreatment of fly ash washing liquid: Sand filtration and fine filtration are used to separate particulate matter in fly ash washing liquid, and calcium ions in fly ash washing liquid are removed by adding sodium carbonate solution.

[0042] (2) The pretreated fly ash washing liquid enters the preheater and is preheated to 95°C before entering the evaporator crystallizer for processing. The evaporation crystallization temperature is 100°C. The potassium chloride content of the fly ash washing liquid in the evaporator crystallizer is analyzed by the online potassium ion analyzer. When the potassium chloride content is 21.7%, the liquid in the evaporator crystallizer is discharged to the first thickener. Sodium chloride first reaches saturation concentration in the evaporator crystallizer and begins to precipitate. As evaporation proceeds, the potassium chloride concentration continuously increases. Due to the common ion effect, the sodium chloride concentration in the solution continuously decreases, but it is still saturated. When the potassium chloride concentration just reaches saturation, it is the three-phase co-saturation point of potassium chloride, sodium chloride and water (when the potassium chloride content is 21.7% at 100°C).

[0043] (3) The concentrated liquid after natural sedimentation in the first thickener is fed into the first centrifuge for separation. At the same time, a saturated sodium chloride solution is passed into the first centrifuge as a washing liquid to wash the sodium salt during centrifugation. Sodium chloride is obtained after centrifugation in the first centrifuge; the purity of the sodium chloride is 96.8%. (4) The supernatant from the first thickener flows by gravity into the cooling crystallizer. Circulating water is used as the cooling medium to cool the liquid in the cooling crystallizer. After the liquid is cooled to 40°C, it enters the second centrifuge for centrifugal separation to obtain potassium chloride salt. The purity of the potassium chloride salt is 95.7%. (5) The solution after washing and separation in the first centrifuge enters the first mother liquor tank and is pumped to the evaporator crystallizer for evaporation treatment; (6) The solution separated by the second centrifuge enters the second mother liquor tank and is pumped to the calcium ion tank, where the solution in the second mother liquor tank reacts with the calcium ion solution to form calcium sulfate precipitate, thus removing the enriched SO4. 2- .

[0044] Example 2 like Figure 2 As shown, this embodiment provides a system for refining and purifying potassium and sodium salts from fly ash washing liquid. Based on embodiment 1, this embodiment also includes a second thickener, which is disposed between the cooling crystallizer and the second centrifuge. The second centrifuge is a piston pusher centrifuge.

[0045] This embodiment provides a method for refining and purifying potassium and sodium salts from fly ash washing liquid. The difference between this embodiment and Embodiment 1 lies in step (4). In this embodiment, step (4) involves the supernatant from the first thickener flowing by gravity into the cooling crystallizer. Circulating water is used as the cooling medium to cool the liquid in the cooling crystallizer. After cooling to 40°C, the liquid is pumped into the second thickener for natural sedimentation and concentration. When the solid content of the liquid volume is 55%, the concentrated liquid enters the second centrifuge for centrifugal separation to obtain potassium chloride. The purity of the sodium chloride obtained in this embodiment is 97.1%; the purity of the potassium chloride obtained is 96.3%. This embodiment can remove SO4 from both sodium and potassium salts. 2- .

[0046] Comparative Example 1 This comparative example provides a system for refining and purifying potassium and sodium salts from fly ash washing liquid. The difference between this comparative example and Example 2 is that this comparative example does not include an online potassium ion analyzer.

[0047] The method for refining and purifying potassium and sodium salts from fly ash washing liquid provided in this embodiment differs from that in embodiment 2 in step (2). In this comparative example, step (2) involves the pretreated fly ash washing liquid entering a preheater and being preheated to 95°C before entering an evaporator crystallizer for processing. The evaporation crystallization temperature is 100°C. In this comparative example, because there is no online potassium ion analyzer, the potassium chloride content is not easy to control and is easily in a saturated or supersaturated state, i.e., the potassium chloride content is greater than 21.7% at 100°C. The liquid in the evaporator crystallizer is discharged into the first thickener.

[0048] The purity of the sodium chloride salt obtained in this comparative example was 93.1%; the purity of the potassium chloride salt obtained was 90.2%.

[0049] Comparative Example 2 This comparative example provides a system for refining and purifying potassium and sodium salts from fly ash washing liquid. The difference between this system and Example 2 is that the first centrifuge used in this comparative example does not have an online washing function.

[0050] The method for refining and purifying potassium and sodium salts from fly ash washing liquid provided in this comparative example differs from that in Example 2 in step (3). In step (3) of this comparative example, the concentrated liquid after natural sedimentation in the first thickener enters the first centrifuge and is directly centrifuged to obtain sodium chloride. The purity of the sodium chloride obtained in this comparative example is 94.9%; the purity of the potassium chloride obtained is 92.8%.

[0051] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A system for refining and purifying potassium and sodium salts from fly ash water wash liquor, characterized by, The sodium salt purification unit, the potassium salt purification unit and the potassium ion on-line analyzer are included. The sodium salt purification unit includes a preheater, an evaporation crystallizer, a first thickener and a first centrifuge connected in sequence. The potassium salt purification unit includes a cooling crystallizer and a second centrifuge connected in sequence, and the cooling crystallizer is connected with the first thickener. The potassium ion on-line analyzer is installed on the evaporation crystallizer.

2. The fly ash water scrubber liquor refined purification of potassium sodium salt system according to claim 1, characterized in that, A second thickener is further included, which is arranged between the cooling crystallizer and the second centrifuge.

3. The fly ash water scrubber liquor refined purification of potassium sodium salt system according to claim 1 or 2, characterized in that, The evaporation crystallizer is a forced circulation evaporation crystallizer, and / or the cooling crystallizer is a jacketed enamel kettle.

4. The fly ash water scrubber liquor refined purification of potassium sodium salt system according to claim 3, characterized in that, The first centrifuge is a centrifuge with on-line washing and separation functions, and / or the second centrifuge is a horizontal screw centrifuge or a piston pusher centrifuge.

5. The fly ash water scrubber liquor refined purification of potassium sodium salt system according to claim 1 or 2, characterized in that, A second mother liquor tank is further included, and a liquid inlet pipeline of the second mother liquor tank is connected with the second centrifuge, and a liquid outlet pipeline of the second mother liquor tank is connected with a calcium ion tank.

6. The fly ash water scrubber liquor refined purification of potassium sodium salt system according to claim 1 or 2 or 4, characterized in that, A first mother liquor tank is further included, and a liquid inlet pipeline of the first mother liquor tank is connected with the first centrifuge, and a liquid outlet pipeline of the first mother liquor tank is connected with the evaporation crystallizer.

7. A method for refining and purifying potassium sodium salt from fly ash water wash liquor, characterized by, The fly ash water washing liquid purification potassium and sodium salt system is prepared by using the system according to any one of claims 1-6.

8. The method of fly ash water scrubber liquor purification of potassium sodium salts according to claim 7, characterized by the fact that, The system includes the following steps: (1) The fly ash water washing liquid is preheated by a preheater and then enters an evaporation crystallizer for treatment, a potassium ion on-line analyzer is used to analyze the potassium chloride content of the fly ash water washing liquid in the evaporation crystallizer, the evaporation crystallization temperature is 100°C, and when the potassium chloride content is 20.7-21.7%, the liquid in the evaporation crystallizer is discharged into a first thickener; (2) The concentrated liquid in the first thickener after natural sedimentation enters a first centrifuge for washing and centrifugal separation to obtain a sodium chloride salt; (3) The supernatant of the first thickener flows into a cooling crystallizer for cooling, and the liquid after concentration enters a second centrifuge for centrifugal separation to obtain a potassium chloride salt; Preferably, the solution after washing and separation of the first centrifuge is sent to the evaporation crystallizer for evaporation treatment; The solution separated by the second centrifuge is sent to a calcium ion tank, and a chemical reaction occurs with the calcium ion solution to generate calcium sulfate precipitate, and the enriched SO4 2- is removed.

9. The method for refining and purifying potassium and sodium salts from fly ash washing liquid according to claim 8, characterized in that, The fly ash water washing liquid is pretreated by filtering and separating particulate matters in the fly ash water washing liquid and removing calcium ions in the fly ash water washing liquid by adding sodium carbonate or sodium sulfate solution.

10. The method for refining and purifying potassium and sodium salts from fly ash washing liquid according to claim 8 or 9, characterized in that, In step (1), the fly ash water washing liquid enters the preheater, is preheated to 95-100°C and then enters the evaporation crystallizer for treatment; And / or in step (3), the liquid in the cooling crystallizer is cooled to 40-50°C.

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