Iron phosphate wastewater salt separation evaporation system

Abstract

The utility model discloses an iron phosphate wastewater salt separation evaporation system. A single-effect evaporation assembly for separating phosphorus salt is arranged between a triple-effect evaporation assembly and a roller drying evaporation assembly; the single-effect evaporation assembly comprises a single-effect evaporator, a single-effect crystallizer, a single-effect thickener, a single-effect separator and a liquid storage tank which are sequentially arranged, and further comprises a steam pipeline used for increasing the temperature of the system, a vacuum pump used for controlling the pressure of the system and a steam-jet pump used for regulating and controlling the temperature of the system. The temperature and the pressure of the system are adjusted to accurately control the evaporative crystallization temperature of the materials, so that the salt separation evaporation and separation efficiency of different supplied materials is improved, the system collapse caused by phosphorus salt accumulation is avoided, and the recovery treatment efficiency and benefits are improved; when the separation effect is not ideal, the crystallization slurry can be conveyed to the front end again for evaporative crystallization and reconstruction, so that the material recovery efficiency and the system flexibility are improved; the heat of materials and steam in the system is well recovered and utilized, and the energy consumption of the system is reduced.

Description

Technical Field

[0001] This utility model relates to a wastewater treatment device in the production process of lithium battery cathode material iron phosphate, and more particularly to an iron phosphate wastewater desalination evaporation system. Background Technology

[0002] The wastewater mother liquor and washing liquid generated during the production of lithium-ion battery cathode material iron phosphate are initially treated with impurities, membranes, and appropriate concentration before being combined for further processing. The concentrated liquid has a high salt content and enters an MVR (Medium-Voltage Reduction) unit for evaporation, concentration, crystallization, and drying, ultimately producing solid particulate salt as a byproduct. Typically, the produced byproduct salt is a mixture of ammonium sulfate and phosphate salts. The ammonium sulfate component is sold as the main product, while some of the mother liquor enters a drum dryer system for processing as coarser mixed salts. This results in the ineffective recovery and efficiency enhancement of the more economically valuable phosphate salts, leading to economic losses. Furthermore, existing MVR units do not separate ammonium sulfate and phosphate salts during incoming material processing. During operation, phosphate salts entering the triple-effect evaporation system cannot be completely discharged, leading to phosphate salt accumulation. When this accumulation reaches a certain level, it disrupts the balance of the entire evaporation system, causing system collapse, reduced evaporation, and eventually no evaporation, resulting in production shutdown and material discharge. Patent document CN218811046U discloses a desalination system for ferric phosphate production wastewater, comprising a preheating unit, a falling film evaporation unit, a forced circulation evaporation crystallization unit, a continuous vacuum flash crystallization unit, a mixed salt evaporation unit, and an insoluble matter discharge unit connected in sequence. This system can sequentially collect ammonium sulfate, monoammonium phosphate, mixed salts, and insoluble matter from ferric phosphate wastewater. However, when the material composition at the front end changes, the boiling points of phosphate salts and sulfates are different, and the evaporation and crystallization temperatures will change. The system cannot adjust the appropriate evaporation and crystallization temperatures according to the changes in material composition, which will greatly reduce the desalination effect and cannot ensure that phosphate salts are effectively separated and thus accumulate in the system, affecting the balance of the entire evaporation system operation. There is still a risk of system collapse or shutdown for maintenance. Utility Model Content

[0003] Purpose of the utility model: The purpose of this utility model is to avoid the inability of phosphate salts to be effectively separated after changes in material composition, which would lead to their accumulation in the system and affect the stability of the salt separation and evaporation system. This utility model provides a phosphate salt separation system with good separation effect and stable system operation for iron phosphate wastewater desalination and evaporation.

[0004] Technical Solution: The phosphate wastewater desalination evaporation system of this utility model includes a triple-effect evaporation assembly and a drum dryer evaporation assembly, and further includes a single-effect evaporation assembly disposed between the triple-effect evaporation assembly and the drum dryer evaporation assembly for separating phosphate salts; the single-effect evaporation assembly includes a single-effect evaporator, a single-effect crystallizer, a single-effect thickener, a single-effect separator and a storage tank arranged in sequence, and further includes a steam pipe connected to the single-effect evaporator for raising the system temperature, and a vacuum pump connected to the single-effect crystallizer for controlling the system pressure; the steam pipe and the single-effect evaporator also include a steam jet pump for regulating the system temperature.

[0005] Furthermore, when the composition of the material at the front end changes, and the boiling points of phosphate and sulfate differ, the evaporation rate of the material in the single-effect evaporator changes, causing the system to deviate from evaporation equilibrium and malfunction. In such cases, the temperature in the single-effect evaporator and single-effect crystallizer can be adjusted by using a vacuum pump to regulate the pressure and by using a steam jet pump to regulate the inflow of hot steam and recovered steam. This allows the system to return to evaporation equilibrium and further ensures the separation efficiency of phosphate when problems occur on the production line. At the same time, it prevents the accumulation of phosphate in the system and ensures the stability of the evaporation system.

[0006] Furthermore, the single-effect evaporator and single-effect crystallizer are equipped with circulation pipes, and circulation pumps are installed on the circulation pipes. The material vapor flowing in the circulation pipes can accelerate the evaporation of the material, and at the same time send the vapor that has not crystallized in the single-effect crystallizer back to the evaporator for regeneration, thereby improving the separation effect of the mixed salt.

[0007] Furthermore, two crystallization slurry pumps are connected in parallel on the connecting pipe between the single-effect crystallizer and the single-effect thickener to improve the efficiency of conveying viscous crystallization slurry backward, and at the same time, to prevent the system from failing due to the failure of a single device, which would affect production efficiency.

[0008] Furthermore, a first loop for recirculating the crystallized slurry is provided between the single-effect thickener and the circulation pipeline. This loop is normally closed. When the separation of components is not ideal, the crystallized slurry can be transported back to the front end for evaporation and crystallization reprocessing through this loop, improving the efficiency of material recovery and enhancing the flexibility of the entire system.

[0009] Furthermore, the single-effect evaporator also includes a condensate collection tank, which is connected to the triple-effect evaporation assembly via a heat exchanger; a surface cooler is provided between the single-effect crystallizer and the vacuum pump, and the outlet of the surface cooler is connected to the condensate collection tank, making full use of the waste heat of the material steam to transfer it back to the material steam, thereby reducing the energy consumption of the entire system.

[0010] Furthermore, a second loop for refluxing material vapor is provided between the storage tank and the circulation pipeline, further recovering material vapor and improving material recovery efficiency; a third loop for recovering material vapor is also provided between the steam pipeline after the single-effect crystallizer and before the surface cooler and at the front end of the steam jet pump. Through the second and third loops, material vapor waste can be avoided, further improving material recovery efficiency.

[0011] Furthermore, the single-effect separator and vacuum pump are also equipped with exhaust ports to ensure the stability of the system operation.

[0012] Furthermore, the single-effect evaporation unit also includes a rinsing device, which is connected to the single-effect evaporation unit via an independent valve to prevent viscous materials from clogging the pipes and affecting the normal operation of the system.

[0013] Beneficial effects: Compared with the prior art, this utility model has the following advantages: 1. By changing the temperature and pressure of the system, the evaporation and crystallization temperature of the material is precisely controlled, and the salt separation evaporation is carried out effectively for materials with different compositions, which improves the separation efficiency of phosphate salts, avoids the accumulation of phosphate salts in the system and avoids system collapse, and improves the efficiency and benefits of ferric phosphate wastewater recycling treatment; 2. A first loop is set between the single-effect thickener and the circulation pipeline. When the separation effect of the components is not ideal, the crystallized slurry can be transported back to the front end for evaporation and crystallization re-creation through this loop, which improves the efficiency of material recovery and enhances the flexibility of the entire system; 3. The material and steam heat in the system are well recovered and utilized, reducing the system energy consumption. Attached Figure Description

[0014] Figure 1 This is a system flowchart of the present invention. Detailed Implementation

[0015] The technical solution of this utility model will be further described below with reference to the accompanying drawings.

[0016] like Figure 1The illustrated ferric phosphate wastewater desalination evaporation system includes a triple-effect evaporator and a drum dryer evaporator, with a single-effect evaporator between the triple-effect evaporator and the drum dryer evaporator for separating phosphate salts. The single-effect evaporator includes, in sequence, a single-effect evaporator 5, a single-effect crystallizer 6, a single-effect thickener 7, a single-effect separator 8, and a storage tank 9. A pump 20 is installed at the outlet of the storage tank 9 to deliver the collected liquid to the drum dryer evaporator. The system also includes a steam pipe 1 connected to the single-effect evaporator 5 to raise the system temperature, and a vacuum pump 10 connected to the single-effect crystallizer 6 to control the system pressure. A circulation pipe 3 is provided between the single-effect evaporator 5 and the single-effect crystallizer 6, and a circulation pump 13 is installed on the circulation pipe 3. A crystallization slurry pump A17 and a crystallization slurry pump B18 are connected in parallel on the connecting pipe between the single-effect crystallizer 6 and the single-effect thickener 7. Through crystallization, pumps A / B transport the material in the single-effect crystallizer 6 to the single-effect thickener 7 for thickening treatment. A first loop 15 for recirculating the crystallized slurry is provided between the single-effect thickener 7 and the circulation pipe 3. This loop is normally closed, and can be collected and sent back to the evaporator and crystallizer for reprocessing when problems occur with the crystallized slurry. A second loop 16 for recirculating material vapor is also provided between the storage tank 9 and the circulation pipe 3. By setting up a loop for secondary recycling, the waste of material vapor is minimized. A steam jet pump 2 for regulating the system temperature is also provided between the steam pipe 1 and the single-effect evaporator 5. The single-effect evaporator 5 also includes a condensate collection tank 12. A surface cooler 11 is provided between the single-effect crystallizer 6 and the vacuum pump 10. The outlet of the surface cooler 11 is connected to the condensate collection tank 12. A condensate pump 19 is provided at the outlet of the condensate collection tank 12 to transport the preheated condensate to the heat exchanger 4 for heat exchange with the triple-effect evaporator components. A third loop 14 for recovering material vapor is also provided between the single-effect crystallizer 6 and the surface cooler 11 and the front end of the steam jet pump 2. The single-effect separator 8 and vacuum pump 10 are also equipped with exhaust ports. The single-effect evaporation unit also includes a rinsing device, which is connected to the single-effect evaporation unit via an independent valve to prevent pipe blockage.

[0017] In operation, the material flowing through the triple-effect evaporation system, along with the steam treated by the steam jet pump 2 in the steam pipe 1, enters the single-effect evaporator 5. The high-temperature steam promotes the evaporation of the material, which then enters the single-effect crystallizer 6. A circulation pipe 3 and a circulation pump 13 are installed between the two to ensure that the material is fully evaporated. The temperature of the material is adjusted by the vacuum pump 10 to regulate the pressure in the single-effect evaporator 5 and the single-effect crystallizer 6, and by the steam jet pump 2 to regulate the inflow of hot steam and recovered steam, thereby allowing the material to fully crystallize. The crystallized slurry is then transported to the single-effect thickener 7 for thickening treatment by the crystallization slurry pumps A / B, and then sent to the single-effect centrifuge 8 for centrifugal separation. After solid-liquid separation, phosphate salts are output from the bottom of the single-effect centrifuge 8, and mother liquor is output from the top to the storage tank 9. A pump 20 is installed at the outlet of the storage tank 9 to send the collected mother liquor to the drum dryer evaporation assembly. The system is equipped with a third loop 14 and a second loop 16 for recovering and reusing material steam, preventing the waste of material steam and further improving the material separation efficiency. The condensate recovered in the system is sent to the front end by a condensate pump 19 to exchange heat with the material transported by the triple-effect evaporator to increase the temperature of the material, thereby reducing steam consumption while ensuring evaporation efficiency, saving energy and reducing emissions. When the material composition at the front end changes, such as the different boiling points of phosphate and sulfate, the change in the evaporation amount of the material in the single-effect evaporator 5 causes the system to deviate from the evaporation balance and cause the system to malfunction, the pressure in the single-effect evaporator 5 and the single-effect crystallizer 6 can be adjusted by the vacuum pump 10, and the inflow of hot steam and recovered steam can be adjusted by the steam jet pump 2 to adjust the temperature in the single-effect evaporator 5 and the single-effect crystallizer 6, so that they can reach the evaporation balance state again, thereby further ensuring the phosphate separation efficiency when the production line encounters problems. When a problem is found with the crystallization slurry, the first loop 15 can be started to transport the crystallization slurry to the circulation pipeline 3 for re-evaporation and crystallization. The whole system is stable and easy to adjust, and can cope with various production line conditions.

Claims

1. A ferric phosphate wastewater desalination evaporation system, comprising a triple-effect evaporation unit and a drum dryer evaporation unit, characterized in that, It also includes a single-effect evaporation unit set between the triple-effect evaporation unit and the drum drying evaporation unit for separating phosphate salts; the single-effect evaporation unit includes a single-effect evaporator (5), a single-effect crystallizer (6), a single-effect thickener (7), a single-effect separator (8) and a storage tank (9) arranged in sequence, and also includes a steam pipe (1) connected to the single-effect evaporator (5) for raising the system temperature, and a vacuum pump (10) connected to the single-effect crystallizer (6) for controlling the system pressure; the steam pipe (1) and the single-effect evaporator (5) also include a steam jet pump (2) for regulating the system temperature.

2. The ferric phosphate wastewater desalination evaporation system according to claim 1, characterized in that, The single-effect evaporator (5) and the single-effect crystallizer (6) are provided with a circulation pipe (3), and a circulation pump (13) is provided on the circulation pipe (3).

3. The ferric phosphate wastewater desalination evaporation system according to claim 2, characterized in that, Two crystallization slurry pumps are connected in parallel on the connecting pipe between the single-effect crystallizer (6) and the single-effect thickener (7).

4. The ferric phosphate wastewater desalination evaporation system according to claim 3, characterized in that, A first loop (15) for reprocessing the reflux crystallization slurry is also provided between the single-effect thickener (7) and the circulation pipe (3).

5. The ferric phosphate wastewater desalination evaporation system according to claim 3, characterized in that, A second loop (16) for refluxing material vapor is also provided between the storage tank (9) and the circulation pipe (3).

6. The ferric phosphate wastewater desalination evaporation system according to claim 1, characterized in that, The single-effect evaporator (5) also includes a condensate collection tank (12), which is connected to the triple-effect evaporation assembly via a heat exchanger (4).

7. The ferric phosphate wastewater desalination evaporation system according to claim 6, characterized in that, A surface cooler (11) is provided between the single-effect crystallizer (6) and the vacuum pump (10), and the outlet of the surface cooler (11) is connected to a condensate collection tank (12).

8. The ferric phosphate wastewater desalination evaporation system according to claim 7, characterized in that, A third circuit (14) for recovering material steam is also provided between the single-effect crystallizer (6), the surface cooler (11), and the steam pipe (1) at the front end of the steam jet pump (2).

9. The ferric phosphate wastewater desalination evaporation system according to claim 1, characterized in that, The single-effect separator (8) and vacuum pump (10) are also equipped with exhaust ports.

10. The ferric phosphate wastewater desalination evaporation system according to claim 1, characterized in that, The single-effect evaporation unit also includes a rinsing device, which is connected to the single-effect evaporation unit via an independent valve.

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