Fly ash washing water sodium potassium fractional salt evaporation equipment

Abstract

The present application is suitable for the technical field of chemical equipment, and particularly relates to a fly ash washing water sodium-potassium fractional salt evaporation equipment, which comprises a 1# MVR sodium chloride crystallization system, a 2# potassium chloride refrigeration crystallization system and a 3# sodium chloride crystallization system; after the salt-containing water after fly ash washing is subjected to heat exchange and gas-liquid separation through the 1# MVR evaporator, sodium chloride salt is precipitated due to evaporation supersaturation, the mother liquor is subjected to cooling flash evaporation through the 2# potassium chloride refrigeration crystallization system, potassium chloride is precipitated therefrom, and the mother liquor is subjected to heating evaporation to supersaturation through the 3# sodium chloride crystallization system, sodium chloride salt is precipitated, and the mother liquor after crystallization is returned to the potassium chloride refrigeration system. The present application reduces the impact on the MVR sodium chloride evaporation crystallization system, effectively realizes automation, flash evaporates the mother liquor of the potassium chloride refrigeration crystallization system, does not need to set a step of adding sodium chloride salt, reduces repeated evaporation of sodium chloride salt, and reduces system operation energy consumption; the flash evaporation process is adopted, traditional heat exchanger heat transfer is reduced, and system adhesion and heat transfer are reduced.

Description

Technical Field

[0001] This invention belongs to the field of chemical equipment technology, and in particular relates to a sodium and potassium salt separation and evaporation device for fly ash washing water. Background Technology

[0002] In response to the national call for energy conservation and emission reduction, the resource utilization of incineration fly ash is being pursued. Evaporators are being used to recover and reuse sodium chloride and potassium chloride from the high salinity of fly ash, reducing the waste of sodium and potassium salts. However, current technology for separating sodium chloride and potassium chloride (sodium-potassium salt separation) mainly focuses on a single-cycle salt separation process with low automation and the need to monitor potassium ion concentration at all times, making it impossible to accurately control the operating parameters of the equipment. Summary of the Invention

[0003] The purpose of this invention is to provide a sodium and potassium salt separation and evaporation device for fly ash washing water, which aims to solve the problems of existing technologies that mainly focus on a single-cycle salt separation process, have low self-control conditions, and require constant monitoring of potassium ion concentration, making it impossible to accurately control the operating parameters of the equipment.

[0004] This invention is implemented as follows: a fly ash washing water sodium and potassium salt separation and evaporation device, the device includes a 1#MVR sodium chloride evaporation and crystallization system, a 2# potassium chloride freeze crystallization system, and a 3# sodium chloride crystallization system. The brine containing water after washing fly ash is transported to the 1#MVR sodium chloride evaporation and crystallization system for heat exchange and gas-liquid separation, precipitating sodium chloride salts. The brine discharged from the 1#MVR sodium chloride evaporation and crystallization system is introduced into the 2# potassium chloride freeze crystallization system for cooling and flash evaporation, precipitating potassium chloride. The discharged liquid is input into the 3# sodium chloride crystallization system for heating and gas-liquid separation, precipitating sodium chloride salts. The remaining liquid is returned to the 2# potassium chloride freeze crystallization system.

[0005] Preferably, the No. 1 MVR sodium chloride evaporation crystallization system includes a first pump body, an MVR heat exchanger, and a gas-liquid separator. The first pump body is used to transport brine to the MVR heat exchanger, the MVR heat exchanger is used to heat the brine, and the heated brine enters the gas-liquid separator for gas-liquid separation treatment.

[0006] Preferably, the No. 2 potassium chloride freeze crystallization system includes a second pump body and a flash condenser. The second pump body is used to transport the liquid discharged from the No. 1 MVR sodium chloride evaporation crystallization system to the No. 2 potassium chloride freeze crystallization system, and the flash condenser is used to flash treat the brine.

[0007] Preferably, during the flash evaporation process, the gas pressure is controlled to -85~-90 kPa by a vacuum pump, and the temperature of the brine is reduced to about 38~42℃.

[0008] Preferably, the No. 3 sodium chloride crystallization system includes a sodium chloride heat exchanger and a sodium chloride separator. The brine from the No. 2 potassium chloride freeze crystallization system enters the sodium chloride heat exchanger for heat exchange, and then undergoes gas-liquid separation treatment through the sodium chloride separator.

[0009] Preferably, after treatment by the No. 3 sodium chloride crystallization system, the potassium chloride concentration in the brine reaches 21%~22% and the sodium chloride concentration reaches 15.8%~17.8%.

[0010] Preferably, after treatment by the No. 2 potassium chloride freeze crystallization system, the potassium chloride concentration in the brine reaches 12%~14% and the sodium chloride concentration reaches 18.6%~20.6%.

[0011] Preferably, the concentration of sodium chloride in the fly ash washing brine is 11%~13%, and the concentration of potassium chloride is 4%~6%.

[0012] The fly ash washing water sodium and potassium salt separation and evaporation equipment provided by this invention has the following advantages: After the potassium chloride (2#) is frozen and crystallized, the mother liquor is sent to the sodium chloride (3#) MVR evaporation and crystallization system. After being concentrated by the sodium chloride (3#) MVR system, the concentration of potassium chloride is 19%~20% and the concentration of sodium chloride is 15.8%~17.8%. The mother liquor is then returned to the potassium chloride (2#) frozen crystallization system. In this cycle, the high-salt concentrated liquid after freezing is returned to the sodium chloride (1#) MVR system, which reduces the impact on the sodium chloride evaporation and crystallization MVR system and can effectively achieve automation. The No. 2 cold crystallization unit flash evaporation increases the sodium chloride concentration from 15.8%~17.8% of the feed to 18.6%~20.6%, which can reach the co-saturation point of sodium chloride and potassium chloride. There is no need to set up a step to add sodium chloride salt, reducing the repeated evaporation of sodium chloride salt and reducing the energy consumption of system operation. The flash evaporation process reduces heat transfer in traditional heat exchangers and minimizes system wall adhesion. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a fly ash washing water sodium-potassium salt separation and evaporation device provided in an embodiment of the present invention.

[0014] In the attached diagram: 2, First pump body; 3, MVR heat exchanger; 4, Gas-liquid separator; 11, Second pump body; 12, Flash condenser; 18, Third pump body; 20, Vacuum pump; 21, Sodium chloride heat exchanger; 22, Sodium chloride separator. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0017] like Figure 1 The diagram shown is an architectural diagram of a fly ash washing water sodium and potassium salt separation and evaporation device provided in an embodiment of the present invention. The device includes a 1#MVR sodium chloride evaporation and crystallization system, a 2# potassium chloride freeze crystallization system, and a 3# sodium chloride crystallization system. The fly ash is washed to obtain brine, which is then transported to the 1#MVR sodium chloride evaporation and crystallization system for heat exchange and gas-liquid separation, from which sodium chloride salt is precipitated. The brine discharged from the 1#MVR sodium chloride evaporation and crystallization system is introduced into the 2# potassium chloride freeze crystallization system for cooling and flash evaporation, from which potassium chloride is precipitated. The discharged liquid is input into the 3# sodium chloride crystallization system for heating and gas-liquid separation, from which sodium chloride salt is precipitated. The remaining liquid is returned to the 2# potassium chloride freeze crystallization system.

[0018] In this embodiment, the equipment includes a 1# MVR sodium chloride evaporation crystallization system, a 2# potassium chloride freeze crystallization system, and a 3# sodium chloride crystallization system. The 1# MVR sodium chloride evaporation crystallization system includes a first pump body 2, an MVR heat exchanger 3, and a gas-liquid separator 4. Fly ash washing yields a brine containing sodium chloride and potassium chloride (sodium chloride concentration 11%~13%, potassium chloride concentration 4%~6%). This brine is then transported to the 1# MVR sodium chloride evaporation crystallization system (system evaporation temperature 98℃~100℃) for heat exchange and gas-liquid separation. The salt is evaporated and crystallized until the potassium chloride concentration reaches 19%~20%. At this point, sodium chloride is supersaturated (concentration >17.8%), and potassium chloride is unsaturated (potassium chloride solubility 21%~22% at 100℃). This process precipitates sodium chloride from the high-salt-water system. The chloride ions discharged from the 1# MVR sodium chloride evaporation crystallization system... A saturated solution of sodium chloride and potassium chloride is introduced into the No. 2 potassium chloride freeze crystallization system. The system undergoes flash evaporation (temperature after flash freezing is 38-42℃). As the temperature decreases from 98-100℃ to 38-42℃, the sodium chloride solubility in the system increases from 15.8%-17.8% to 18.6%-20.6%, making it an unsaturated solution. Meanwhile, the potassium chloride solubility decreases from 21%-22% to 12%-14%, making it supersaturated. Potassium chloride precipitates from the high-salt water mixture. The discharged liquid is then introduced into the No. 3 sodium chloride crystallization system. This system heats the solution (evaporation temperature is 98-100℃) and performs gas-liquid separation, evaporating the sodium chloride to a supersaturated state and the potassium chloride concentration to 19%-20%, thus precipitating sodium chloride salt. The remaining liquid is returned to the No. 2 potassium chloride freeze crystallization system.

[0019] In this embodiment of the invention, according to the sodium chloride and potassium chloride co-saturated system, under high temperature conditions (98℃~100℃), the concentration of potassium chloride in the sodium chloride and potassium chloride system is 21%~22%, and the concentration of sodium chloride is 15.8%~17.8%; under low temperature conditions (38℃~42℃), the concentration of potassium chloride in the sodium chloride and potassium chloride system is 12%~14%, and the concentration of sodium chloride is 18.6%~20.6%; the concentration of sodium chloride in the fly ash washing feed is 11%~13%, and the concentration of potassium chloride is 4%~6%.

[0020] After being washed, fly ash yields brine, which is then pumped to the No. 1 MVR sodium chloride evaporation and crystallization system. Heat exchange occurs in the MVR heat exchanger 3, followed by gas-liquid separation in the gas-liquid separator 4. The No. 1 MVR sodium chloride evaporation and crystallization system evaporates and concentrates the brine until the potassium chloride concentration reaches 19%–20%. At this point, sodium chloride is supersaturated (concentration > 17.8%), while potassium chloride is unsaturated (potassium chloride solubility is 21%–22% at 100℃). This process precipitates sodium chloride from the high-salt water system. The No. 2 potassium chloride cryogenic crystallization system adopts a flash freezing process, as follows: The brine is pumped to the No. 2 potassium chloride cryogenic crystallization system via the second pump 11. The system vacuum is increased to approximately -90 kPa by the flash condenser 12 and vacuum pump 20. After flash evaporation, the material is cooled from a high temperature to a low temperature of 38℃~42℃. This temperature reduction is provided by flash evaporation, reducing the contact between the heat exchanger and the material, and minimizing heat exchanger adhesion issues. Simultaneously, a portion of the solution is flashed, increasing the sodium chloride crystallization salt concentration to near the co-saturated system of sodium chloride and potassium chloride (sodium chloride concentration after flash evaporation is 18.6%~20.6%). At this point, the sodium chloride solubility is close to the co-saturation point, indicating an unsaturated solution. The potassium chloride solubility decreases from 19%~20% to 12%~14%, indicating a supersaturated state. Potassium chloride precipitates from the high-salt water mixture. After cold precipitation of potassium chloride, the solution is pumped to the No. 3 sodium chloride crystallization system by the third pump 18. The brine entering the No. 3 sodium chloride crystallization system is heated by the sodium chloride heat exchanger 21 and separated into gas and liquid by the sodium chloride separator 22. The material temperature is increased from a low temperature of 38℃~42℃ to a high temperature of 98℃~100℃. In the No. 3 sodium chloride MVR evaporation system, it is finally concentrated to a potassium chloride concentration of about 20%. At this point, the sodium chloride is supersaturated and the potassium chloride is unsaturated. Sodium chloride salt is precipitated in the No. 3 sodium chloride crystallization system (the solubility of potassium chloride at 100℃ is 21%~22%). The remaining mother liquor is returned to the No. 2 potassium chloride freeze crystallization system.

[0021] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fly ash washing water sodium-potassium salt separation and evaporation device, characterized in that, The equipment includes a 1#MVR sodium chloride evaporation crystallization system, a 2# potassium chloride freeze crystallization system, and a 3# sodium chloride crystallization system. The brine, after washing fly ash, is transported to the 1#MVR sodium chloride evaporation crystallization system for heat exchange and gas-liquid separation, precipitating sodium chloride. The brine discharged from the 1#MVR sodium chloride evaporation crystallization system is then introduced into the 2# potassium chloride freeze crystallization system for cooling and flash evaporation, precipitating potassium chloride. The discharged liquid is input into the 3# sodium chloride crystallization system, where it is heated and undergoes gas-liquid separation to precipitate sodium chloride. The remaining liquid is returned to the 2# potassium chloride freeze crystallization system.

2. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 1, characterized in that, The No. 1 MVR sodium chloride evaporation crystallization system includes a first pump body (2), an MVR heat exchanger (3) and a gas-liquid separator (4). The first pump body (2) is used to transport brine to the MVR heat exchanger (3). The MVR heat exchanger (3) is used to heat the brine. The heated brine enters the gas-liquid separator (4) for gas-liquid separation.

3. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 1, characterized in that, The No. 2 potassium chloride freeze crystallization system includes a second pump body (11) and a flash condenser (12). The second pump body (11) is used to transport the liquid discharged from the No. 1 MVR sodium chloride evaporation crystallization system to the No. 2 potassium chloride freeze crystallization system. The flash condenser (12) is used to flash treat the brine.

4. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 3, characterized in that, During the flash evaporation process, the gas pressure is controlled to -85~-90 kPa by a vacuum pump (20), and the temperature of the brine is reduced to about 38~42℃.

5. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 1, characterized in that, The No. 3 sodium chloride crystallization system includes a sodium chloride heat exchanger (21) and a sodium chloride separator (22). The brine from the No. 2 potassium chloride freeze crystallization system enters the sodium chloride heat exchanger (21) for heat exchange, and after heat exchange, it is separated into gas and liquid by the sodium chloride separator (22).

6. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 5, characterized in that, After treatment by the No. 3 sodium chloride crystallization system, the potassium chloride concentration in the brine reaches 21%~22%, and the sodium chloride concentration reaches 15.8%~17.8%.

7. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 5, characterized in that, After treatment by the No. 2 potassium chloride freeze crystallization system, the potassium chloride concentration in the brine reaches 12%~14%, and the sodium chloride concentration reaches 18.6%~20.6%.

8. The fly ash washing water sodium-potassium salt separation and evaporation equipment according to claim 1, characterized in that, In the brine of fly ash washing, the concentration of sodium chloride is 11%~13% and the concentration of potassium chloride is 4%~6%.

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