Flocculating agent dosing system for solving material leakage of horizontal screw centrifuge for iron phosphate production

Abstract

The invention discloses a flocculating agent dosing system for solving material leakage of a horizontal screw centrifuge for iron phosphate production, and relates to the technical field of iron phosphate production equipment.The system comprises a flocculating agent preparation unit, a metering and conveying unit, a mixed reaction unit and a control system which are sequentially connected through pipelines, and the discharging end of the mixed reaction unit communicates with a feeding port of the horizontal screw centrifuge; the flocculant preparation unit is used for preparing an anionic polyacrylamide solution with specific parameters, the metering and conveying unit is used for dynamically and accurately conveying, the mixing reaction unit is used for realizing full mixing reaction, and the control system is used for guaranteeing accurate feeding through PLC closed-loop control; the invention aims to solve the problems of material leakage of a horizontal screw centrifuge and high solid content of filtrate caused by fine particle size and strong suspension stability in iron phosphate production, which cannot be fundamentally solved by the prior art, easily affected product quality and high energy consumption.

Description

Technical Field

[0001] This invention belongs to the technical field of ferric phosphate production equipment, and relates to a flocculant dosing system for solving the problem of material leakage in horizontal screw centrifuges during ferric phosphate production. Background Technology

[0002] As a core precursor for lithium-ion battery cathode materials, the production quality of iron phosphate directly affects the electrochemical performance of end-product batteries, holding a crucial position in the new energy industry. The production process of iron phosphate typically encompasses core steps such as dissolution, reaction, precipitation, separation, aging, washing, drying, and calcination. Among these, solid-liquid separation is the key step determining product yield and purity. Horizontal screw centrifuges, with their advantages of large processing capacity, high automation, and stable separation efficiency, have become the preferred continuous separation equipment for the washing process after aging in iron phosphate production. They are particularly well-suited to the needs of large-scale continuous industrial production, enabling efficient and continuous separation of feed and liquid, ensuring the continuity of the production process.

[0003] However, in practical production applications, horizontal screw centrifuges face a significant problem of material loss. Due to the small particle size (micrometer level) and extremely strong suspension stability of ferric phosphate particles, they are difficult to settle quickly during centrifugation. Some solid particles cannot be effectively retained and are discharged from the centrifuge along with the mother liquor, resulting in a high solids content in the filtrate, around 1%. This problem not only reduces the yield of ferric phosphate, increases raw material loss and production costs, but also significantly increases the load and difficulty of subsequent mother liquor treatment, affecting the stability and continuity of the entire production process. Simultaneously, the product loss caused by material loss indirectly affects production efficiency, becoming a key bottleneck restricting the large-scale, efficient production of ferric phosphate.

[0004] To address the issues of material spillage and incomplete solid-liquid separation in decanter centrifuges, several solutions have been developed in existing technologies. One approach is to improve separation efficiency by optimizing equipment operating parameters, such as adjusting the centrifuge's rotation speed, feed flow rate, or optimizing the material pretreatment temperature. The advantage of this approach is that it requires no additional equipment, is easy to operate, and has low modification costs, and can alleviate material spillage to some extent in the short term. However, its disadvantages are also significant. Adjusting the rotation speed and feed flow rate is limited by the equipment's inherent performance, with limited adjustable range. Excessive adjustments can lead to a substantial increase in energy consumption, while changing the pretreatment temperature may damage the crystal structure and physicochemical properties of ferric phosphate, failing to fundamentally solve the problem of incomplete separation caused by particle suspension. Another solution involves using flocculants to assist separation. By adding flocculants, fine particles are promoted to aggregate, improving the separation effect. This technology has already been applied in some solid-liquid separation equipment. For example, patent CN220879220U discloses a "horizontal screw centrifuge with flocculant injection device". This patent adds an injection device containing a mixing box, a water tank and a flocculant tank to the casing of the horizontal screw centrifuge. The flocculant and water are mixed in the mixing box and then directly injected into the centrifuge chamber. Rotating blades and stirring rods are used to assist the material in mixing with the flocculant, thereby improving the separation efficiency. Its advantages lie in the integrated design of flocculant dosing and centrifuge, eliminating the need for additional independent equipment, reducing floor space, and ensuring that the flocculant concentration meets usage requirements. However, this solution has significant drawbacks: it does not select specialized flocculants for the characteristics of ferric phosphate solution, using a general-purpose flocculant dosing design, which is difficult to adapt to the adsorption and coagulation requirements of ferric phosphate particles; the flocculant and solution are only mixed through mechanical stirring in the centrifuge chamber, resulting in short mixing time and insufficient reaction, making it difficult to form stable large-diameter flocs; at the same time, it only achieves basic flow regulation through a flow control switch, lacking a precise control mechanism that dynamically matches the solution flow, and cannot cope with fluctuations in solution flow during production, leading to unstable flocculation effects and difficulty in completely solving the problem of material loss in ferric phosphate production. In addition, some technologies use general-purpose flocculant dosing devices, but they generally suffer from problems such as improper flocculant selection, insufficient dosing accuracy, and insufficient mixing reaction, and some flocculant may remain in the product, affecting the purity of ferric phosphate. In summary, existing solutions either fail to fundamentally solve the problem or suffer from poor adaptability and insufficient stability, making it difficult to meet the high requirements of ferric phosphate production for separation efficiency, product quality, and production continuity. Therefore, there is an urgent need to develop a specialized solution that is highly targeted, provides stable separation, and does not affect product quality. This solution should be developed by precisely selecting flocculants and optimizing the dosing system structure and control logic to fundamentally enhance the agglomeration effect of ferric phosphate particles and completely solve the problem of material leakage in horizontal screw centrifuges. Summary of the Invention

[0005] This invention provides a flocculant dosing system to solve the problem of material leakage in the decanter centrifuge during ferric phosphate production. It addresses the technical problems caused by the small particle size and strong suspension stability of ferric phosphate particles, which leads to material leakage in the decanter centrifuge and high solids content in the filtrate. Existing technologies, which only adjust equipment parameters or use general treatment solutions, cannot fundamentally solve these problems and are prone to affecting product quality and have high energy consumption.

[0006] To solve the above problems, the technical solution adopted by the invention is as follows: A flocculant dosing system for solving material leakage in a horizontal screw centrifuge during ferric phosphate production includes a flocculant preparation unit, a metering and conveying unit, a mixing and reaction unit, and a control system connected sequentially via pipelines. The discharge end of the mixing and reaction unit is connected to the inlet of the horizontal screw centrifuge. The flocculant preparation unit is used to mix and dissolve anionic polyacrylamide raw material with deionized water at a preset mass ratio to prepare a uniform and stable flocculant solution. The anionic polyacrylamide has a molecular weight of 8-12 million, and its mixing mass ratio with deionized water is 0.05-0.15:100. The metering and conveying unit is used to convey the flocculant solution to the mixing and reaction unit. This metering and conveying unit includes a variable frequency metering pump, a flow sensor, and a buffer tank. The variable frequency metering pump dynamically adjusts the output flow rate according to the feed flow rate of the ferric phosphate solution, ensuring that the flocculant solution and the ferric phosphate solution are in a uniform volume. The product ratio is 0.5-1.5:1000. The flow sensor monitors the flocculant solution delivery flow rate in real time and feeds it back to the control system. The mixing reaction unit includes a static mixer and a reaction pipeline. The feed end of the static mixer is connected to the discharge end of the metering and conveying unit and the ferric phosphate solution delivery pipeline. It is equipped with spiral mixing blades inside. The reaction pipeline is 5-8m long and has a diameter of DN50-DN80. The material residence time in the pipeline is 30-60s. The control system includes a PLC controller, a flow acquisition module, and an execution module. The flow acquisition module collects the ferric phosphate solution feed flow rate and the flocculant solution delivery flow rate and transmits them to the PLC controller. The PLC controller controls the frequency conversion speed of the metering pump according to the preset liquid-liquid ratio parameters. The control system is also equipped with an alarm module, which automatically issues an alarm signal when the flow deviation exceeds ±5%.

[0007] The principle and advantages of this scheme are as follows: The core principle of this solution is to utilize the characteristics of fine particle size and strong suspension stability of ferric phosphate particles. Anionic polyacrylamide with a molecular weight of 8-12 million is selected as a specialized flocculant. The polar groups on the flocculant's molecular chain can specifically adsorb onto the surface of ferric phosphate particles, bridging the dispersed fine particles to form large-sized, stable flocs, significantly improving particle settling velocity and centrifugal separation compatibility. The flocculant preparation unit mixes polyacrylamide and deionized water at a mass ratio of 0.05-0.15:100 to prepare a uniform and stable flocculant solution under specific process conditions, providing a foundation for subsequent coagulation. The metering and delivery unit uses a variable frequency metering pump to dynamically adjust the output flow rate of the flocculant solution based on the ferric phosphate feed flow rate, ensuring that the volume ratio of the two remains stable at 0.5- 1.5:1000, the flow sensor provides real-time feedback data to ensure accurate dosing; in the mixing reaction unit, the static mixer achieves forced and sufficient contact between the flocculant solution and the ferric phosphate solution through internal spiral mixing blades, and then through a reaction pipe with a length of 5-8m and a diameter of DN50-DN80, the material completes the full reaction within a residence time of 30-60s, forming large-particle flocs with a particle size of 50-100μm; the control system receives dual-channel flow data transmitted by the flow acquisition module through a PLC controller, adjusts the speed of the metering pump according to preset proportional parameters, and simultaneously provides early warning for flow deviations exceeding ±5% through an alarm module, constructing a closed-loop control throughout the entire process to ensure stable and efficient system operation, ultimately achieving efficient separation of flocs in the horizontal screw centrifuge, solving the material loss problem at its root.

[0008] The selection and precise proportioning of specialized flocculants have achieved a breakthrough improvement in separation efficiency. Existing technologies often use general-purpose flocculants or lack clearly defined flocculant characteristics, failing to specifically address the coagulation requirements of ferric phosphate particles. This solution, however, uses anionic polyacrylamide within a specific molecular weight range, combined with precise preparation and dosage ratios, reducing the material loss rate in horizontal screw centrifuges from 5-8% in existing technologies to below 0.5%, and significantly lowering the solids content of the filtrate from around 1%. This completely solves the long-standing material loss problem plaguing the industry, resulting in a significant 5-8% increase in product yield—a technological breakthrough that cannot be achieved simply by adjusting equipment parameters or using general-purpose flocculants. The dynamic closed-loop control system significantly improves system adaptability and stability. Existing technologies often use fixed flow control or lack precise regulation mechanisms, making it difficult to cope with fluctuations in the liquid flow rate during production. This solution, through the synergistic action of a PLC controller, a variable frequency metering pump, and a flow sensor, achieves real-time dynamic matching between the flocculant dosage and the ferric phosphate liquid flow rate, even when production load changes. The variation in flocculant concentration ensures stable coagulation, avoiding the separation efficiency decline caused by feed fluctuations in existing technologies. The specialized design of the mixing reaction unit guarantees sufficient reaction. In existing technologies, flocculants and feed are often mixed for a short time or directly injected into the centrifuge chamber, resulting in insufficient mixing and reaction time, making it difficult to form stable large-particle flocs. This solution, through forced mixing with a static mixer and a dedicated reaction pipeline design, ensures that each iron phosphate particle effectively contacts and coagulates with the flocculant. The resulting large-particle flocs are less likely to be carried over by the mother liquor during centrifugation, significantly improving separation efficiency. This solution ensures separation effectiveness without affecting product quality and has lower operating costs. The selected anionic polyacrylamide can be completely decomposed into harmless gas during the subsequent calcination process at 600-700℃, leaving no solid residue. This ensures the iron phosphate product purity is ≥99.5%, meeting the stringent requirements for lithium-ion battery cathode material precursors, whereas some existing technologies may have residual risks with the flocculants used.

[0009] Furthermore, the flocculant preparation unit includes a dissolving tank, a stirrer, and a temperature control module. The stirrer is located inside the dissolving tank, with a stirring speed of 60-120 r / min. The temperature control module controls the dissolution temperature at 25-35℃. This speed range provides sufficient shear force and hybrid power to break down the liquid film resistance on the surface of polyacrylamide particles, avoiding incomplete dissolution caused by raw material agglomeration and ensuring the flocculant molecular chains are fully extended. It also avoids molecular chain breakage and degradation due to excessive speed, maintaining its core flocculation performance of 8-12 million molecular weight. A dissolution temperature range of 5-35℃ is suitable for the dissolution characteristics of anionic polyacrylamide. Within this temperature range, the dissolution rate of raw materials can be accelerated, the preparation cycle shortened, and the rhythm requirements of continuous production can be met. At the same time, it avoids the slow dissolution and poor solution uniformity caused by low temperatures, or the thermal degradation of polyacrylamide caused by high temperatures. The final product is a flocculant solution with uniform concentration and stable performance, ensuring that it can fully exert its "bridging" and coagulation effect after mixing with the ferric phosphate solution, forming flocs with acceptable particle size and strong stability. This provides a reliable guarantee for the efficient subsequent centrifugation and the complete solution of material loss problems.

[0010] Furthermore, the dissolving tank is equipped with a feed port with a dust cover at the top, a slag discharge port at the bottom, and a level gauge on the side wall. The feed port with the dust cover effectively prevents airborne dust and impurities from entering the tank when adding anionic polyacrylamide raw materials, avoiding contamination of the flocculant solution and preventing impurities from affecting the subsequent adsorption and coagulation effect of the flocculant and ferric phosphate particles, thus ensuring the stability of solution purity and flocculation performance. The slag discharge port at the bottom can periodically discharge raw material residues and undissolved small amounts of impurities deposited in the tank, preventing long-term accumulation of impurities that could hinder stirring and cause uneven solution mixing, while also reducing... This reduces the risk of blockage in subsequent metering pumps and pipelines, lowering equipment maintenance frequency and costs. The side-wall level gauge provides real-time, intuitive display of the flocculant solution level in the tank, allowing operators to accurately control the amount of material and water added. This ensures that polyacrylamide and deionized water are always mixed at the preset mass ratio of 0.05-0.15:100, avoiding fluctuations in solution concentration due to level deviations. It also facilitates timely replenishment, ensuring the continuity of flocculant preparation. This is suitable for the continuous separation requirements of horizontal screw centrifuges in ferric phosphate production, ensuring the coordinated stability of the entire dosing system and production process.

[0011] Furthermore, the static mixer is made of 304 stainless steel. 304 stainless steel possesses excellent corrosion resistance, effectively resisting the acidic environment of the ferric phosphate solution from corroding the equipment. This prevents equipment damage and leakage due to material corrosion, while also preventing impurities generated by corrosion from mixing into the solution. This ensures that the adsorption and coagulation effect of the flocculant and ferric phosphate particles is not interfered with, and avoids impurity contamination affecting the purity of the ferric phosphate product. In addition, 304 stainless steel also has good high-temperature resistance and mechanical strength, capable of adapting to temperature fluctuations in the solution during production and the stirring impact of the spiral mixing blades inside the static mixer. It is not prone to deformation or damage, extending the service life of the equipment, reducing maintenance and replacement frequency and costs, and ensuring that the mixing reaction unit can continuously and stably achieve forced and sufficient contact of materials. This lays a solid equipment foundation for the subsequent formation of large-particle-size stable flocs and the complete solution to the material leakage problem.

[0012] Furthermore, the anionic polyacrylamide can be completely decomposed into carbon dioxide and nitrogen at 600-700℃, leaving no solid foreign matter residue. Iron phosphate, as a core precursor for lithium-ion battery cathode materials, has stringent requirements for product purity (≥99.5%) and physicochemical properties. However, some flocculants in existing technologies cannot be completely decomposed and easily leave solid impurities, directly affecting the battery's electrochemical performance. The anionic polyacrylamide selected in this solution is compatible with the subsequent calcination process of iron phosphate at 600-700℃. At this temperature, it can be completely decomposed into harmless gases, which are discharged from the system with the exhaust gas, leaving no solid foreign matter residue in the product. This ensures that the purity of the iron phosphate product meets the usage standards for lithium-ion battery cathode material precursors, and that all physicochemical indicators remain unaffected. Simultaneously, there is no need to design additional filtration and washing processes to remove flocculant residues, avoiding increased production complexity and costs. This ensures both product quality stability and production continuity, solving the industry pain point of balancing flocculant addition and product purity.

[0013] Furthermore, the buffer tank of the metering and conveying unit is equipped with an anti-sedimentation stirring structure with a stirring speed of 30-50 r / min. This ensures the uniformity and stability of the flocculant solution during temporary storage and conveying, avoiding deviations in dosing accuracy caused by solution stratification and flocculant sedimentation, and providing a reliable guarantee for the subsequent mixing reaction effect. During temporary storage in the buffer tank, if the flocculant solution lacks stirring, flocculant molecules are prone to sedimentation and uneven solution concentration, which in turn leads to fluctuations in the flocculant concentration output by the metering pump, affecting the accuracy of the ratio with the ferric phosphate solution and weakening the coagulation effect. The low-speed stirring of 30-50 r / min can create gentle and continuous fluid dynamics, effectively preventing flocculant sedimentation. This layered design maintains a consistently uniform solution concentration while preventing flocculant molecular chain breakage or premature flocculation caused by excessive rotation speed, thus preserving its original flocculation performance. Simultaneously, this design ensures that the flow sensor monitors the true flow rate of the uniform solution, enabling the control system to achieve precise adjustments based on accurate data. This avoids dosage imbalances caused by localized concentration deviations and ensures a stable volume ratio of 0.5-1.5:1000 between the flocculant solution and the ferric phosphate solution. This provides a crucial transport link for forming large-particle-size stable flocs and completely resolving material leakage issues. It also reduces the risk of pipeline or metering pump blockage due to sedimentation, improving the continuity and stability of system operation.

[0014] Furthermore, the inner wall of the reaction pipe is provided with an anti-corrosion coating, which is a polytetrafluoroethylene (PTFE) coating with a thickness of 0.5-1.0 mm. PTFE has extremely strong corrosion resistance, completely resisting the acidic erosion of the ferric phosphate solution, preventing leakage due to corrosion damage to the inner wall of the pipe, and preventing metallic impurities generated by corrosion from mixing into the solution. This avoids impurities interfering with the adsorption "bridging" effect between anionic polyacrylamide and ferric phosphate particles, ensuring the integrity and stability of floc formation, and also prevents impurities from affecting the purity of the ferric phosphate product. Its extremely low surface friction coefficient reduces the flow resistance of the solution in the pipe, ensuring that the material flows at the preset rate. Stable conveying ensures a precise 30-60s residence time, preventing incomplete reactions due to flow rate fluctuations. A 0.5-1.0mm coating thickness forms a dense and effective corrosion barrier, meeting the wear and corrosion resistance requirements for long-term use, without reducing pipe diameter or affecting flow rate due to excessive coating thickness. Furthermore, the chemically stable PTFE material does not react with flocculants or ferric phosphate solutions, further ensuring stable material performance, reducing pipeline maintenance and cleaning frequency and costs, and ensuring the continuous and stable operation of the mixing reaction unit. This provides reliable pipeline support for efficient separation in horizontal screw centrifuges and effectively solves the problem of material leakage.

[0015] Furthermore, the control system also includes a touch screen that can display material flow rate, liquid-liquid ratio, dissolution temperature, and equipment operating status in real time. It also supports manual parameter adjustment. Operators can intuitively obtain real-time flow rates of the ferric phosphate solution and flocculant solution, their liquid-liquid ratio, the dissolution temperature of the flocculant preparation, and the operating status of each unit, such as the metering pump's working status and alarm information, through the touch screen. This eliminates the need to check each device individually or read scattered instrument data, achieving centralized and visual monitoring of key production parameters. This facilitates quick understanding of system operation and timely detection of anomalies. Simultaneously, when special adjustments are needed in production conditions, such as slight changes in the characteristics of the solution, the system can be adjusted accordingly. When adjusting chemical processes or temporary production loads, preset parameters such as liquid-liquid ratio, dissolution temperature, and metering pump speed can be manually adjusted directly via the touch screen without disassembling the equipment or modifying complex backend settings. This flexible and efficient operation can quickly adapt to the fine-tuning needs of different production scenarios. In addition, the centralized display and operation design reduces the workload of manual recording and calculation, and reduces production fluctuations caused by deviations in manual data reading or incorrect parameter settings. This further enhances the precise control capability of the control system, making the operation of the entire dosing system easier to control. It provides more convenient operational support for continuously and stably solving the problem of material leakage in the decanter centrifuge and ensuring product quality and production efficiency.

[0016] Furthermore, the flocculant preparation unit is equipped with an online concentration monitoring module, which monitors the flocculant solution concentration in real time and feeds the data back to the PLC controller. When the concentration deviation exceeds ±3%, the PLC controller automatically adjusts the feed or water dosage. Flocculant concentration is a key factor affecting the coagulation effect of ferric phosphate particles. If the concentration is too low, it is difficult to fully achieve particle "bridging" coagulation, and large-diameter flocs cannot be formed, resulting in material loss during centrifugation. If the concentration is too high, it will not only waste flocculant and increase operating costs, but may also lead to excessively large or agglomerated flocs, affecting centrifugation efficiency. The online concentration monitoring module can capture changes in solution concentration in real time without manual sampling and testing, avoiding the lag and error of manual monitoring. When the concentration deviation exceeds the preset range of ±3%, the PLC controller automatically adjusts the feed or water dosage to quickly correct the concentration to the preset range, ensuring that the anionic polyacrylamide and deionized water are always stably mixed at a mass ratio of 0.05-0.15:100, ensuring consistent flocculant solution performance. This design effectively avoids concentration deviations caused by factors such as fluctuations in raw material purity, insufficient stirring, and slight temperature changes. It solves the problem of easy concentration loss in traditional preparation methods, making the effects of subsequent metering, conveying, mixing, and reaction stages more stable. This ensures that the material loss rate of the horizontal screw centrifuge remains consistently below 0.5%, while reducing manual intervention costs and improving the system's automation level and the continuity of the production process. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the structure for preparing the flocculant of the present invention. Detailed Implementation

[0019] The reference numerals in the accompanying drawings include: 1. Flocculant preparation unit; 2. Tank; 3. Stirring mechanism; 4. Feeding port; 5. Metering and conveying unit; 6. Control system; 7. Discharge end; 8. Dissolving tank; 9. Stirring device; 10. Temperature control module; 11. Level gauge; 12. Slag discharge port; 13. Reaction pipeline; 14. Flow sensor; 15. Variable frequency metering pump; 16. Buffer tank; 17. Control valve; 18. Static mixer; 19. Metering and conveying unit discharge end; 20. Conveying pipeline; 21. Flow acquisition module; 22. Stirring blades; 23. Overflow pipe; 24. Drain pipe; 25. Mixing reaction unit.

[0020] Example 1 like Figure 1-2 As shown, a flocculant dosing system for solving material leakage in a horizontal screw centrifuge during ferric phosphate production includes a flocculant preparation unit 1, a metering and conveying unit 5, a mixing and reaction unit 25, and a control system 6, which are sequentially and sealed together by pipelines. The discharge end 7 of the mixing and reaction unit 25 is fixedly connected to the feed inlet of the horizontal screw centrifuge via a flange to ensure that there is no leakage during the material conveying process.

[0021] The flocculant preparation unit 1 includes a tank 2, which contains a dissolving tank 8 and a buffer tank 16. A stirring mechanism 3 is fixedly installed inside the dissolving tank. The stirring mechanism 3 consists of a stirring motor and a stirring device 9. The stirring motor drives the stirring device 9 to rotate at a speed of 60 r / min. A temperature control module 10 is installed on the outside of the dissolving tank 8. The temperature control module 10 uses electric heating to stably control the dissolving temperature in the dissolving tank 8 at 25℃. A feed port 4 with a dust cover is located at the top of the tank 2 and is connected to the dissolving tank 8. This port is used to add anionic polyacrylamide raw material with a molecular weight of 8 million. An overflow pipe 23 (DN40) is also connected to the top. A slag discharge port 12 and a drain pipe 24 (DN40) are located at the bottom. A level gauge 11 is embedded in the side wall to monitor the solution level in real time. During preparation, anionic polyacrylamide raw material and deionized water are added to the tank 2 at a mass ratio of 0.05:100. The stirring mechanism 3 and the temperature control module 10 are started, and stirring is continued for 30 minutes to obtain a uniform and stable flocculant solution.

[0022] The metering and conveying unit 5 includes a buffer tank 16, a variable frequency metering pump 15, and a flow sensor 14. The inlet of the buffer tank 16 is connected to the outlet of the dissolving tank 8 via a pipeline, and the outlet of the buffer tank 16 is connected to the inlet of the variable frequency metering pump 15 via a pipeline. The flow sensor 14 is connected in series on the outlet pipeline of the variable frequency metering pump 15. The outlet of the variable frequency metering pump 15 is connected to one of the inlets of the static mixer 18 of the mixing reaction unit 25 via a pipeline. The ferric phosphate solution conveying pipeline 20 is directly connected to the other inlet of the static mixer 18. A control valve 17 is installed in the middle of the pipeline to control the flow of the solution. During operation, the variable frequency metering pump 15 dynamically adjusts the output flow rate according to the feed flow rate of the ferric phosphate solution to ensure that the volume ratio of the flocculant solution to the ferric phosphate solution is stable at 0.5:1000. The flow sensor 14 monitors the conveying flow rate of the flocculant solution in real time and feeds the data back to the control system 6.

[0023] The mixing reaction unit includes a static mixer 18 and a reaction pipeline 13. The static mixer 18 is made of 304 stainless steel and has spiral stirring blades 22 inside. Its two feed ends are connected to the discharge end 19 of the metering and conveying unit and the iron phosphate liquid conveying pipeline 20, respectively. The discharge end of the static mixer 18 is welded and fixed to one end of the reaction pipeline 13. The other end of the reaction pipeline 13 is connected to the feed port of the horizontal screw centrifuge. The specification of the reaction pipeline 13 is DN50 and the length is set to 5m. The pipeline layout ensures that the residence time of the material in the pipeline is 30s, so that the flocculant and the iron phosphate liquid can fully react to form large-particle flocs.

[0024] The control system 6 includes a PLC controller, a flow acquisition module 21, and an alarm module. The flow acquisition module 21 is connected to the flow sensor on the ferric phosphate liquid conveying pipeline 20 and the flow sensor 14 on the metering and conveying unit 5, respectively, to collect the flow data of the two liquids and transmit them to the PLC controller. The PLC controller is connected to the variable frequency metering pump 15, the temperature control module 10, and the stirring mechanism 3, and controls the variable frequency speed of the variable frequency metering pump 15 according to the preset liquid-liquid ratio parameters. The alarm module is connected to the PLC controller and automatically issues an audible and visual alarm signal when the flow deviation exceeds ±5%.

[0025] This system was applied to a ferric phosphate production line. Before operation, the material loss rate of the horizontal screw centrifuge was 7.2%, and the solid content of the filtrate was 1.0%. After starting the system, the flocculant solution and ferric phosphate solution were mixed and reacted according to a preset ratio, and the resulting flocs had a particle size of 50-80μm. After separation by the horizontal screw centrifuge, the material loss rate dropped to 0.3%, the solid content of the filtrate dropped to below 0.1%, the ferric phosphate product yield increased by 6.9%, and the product purity was 99.6%. All performance indicators met the requirements for use as precursors for lithium-ion battery cathode materials.

[0026] Example 2 The difference between this embodiment and Embodiment 1 is as follows: the molecular weight of the anionic polyacrylamide raw material is 10 million, and its mixing mass ratio with deionized water is 0.08:100; the stirring speed of the stirring mechanism 3 is 90 r / min, and the temperature control module 10 controls the dissolution temperature to 30℃; the variable frequency metering pump 15 adjusts the volume ratio of flocculant solution to ferric phosphate solution to 1.0:1000; the specification of the reaction pipeline 13 is DN65, the length is 6.5m, and the residence time of the material in the pipeline is 45s.

[0027] When this system was applied to a ferric phosphate production line, the material loss rate of the horizontal screw centrifuge was 6.8% before operation, and the solid content of the filtrate was 0.95%. After the system was put into operation, the material loss rate dropped to 0.2%, the solid content of the filtrate dropped to 0.08%, the yield of ferric phosphate increased by 6.6%, the product purity was 99.7%, and the system ran continuously for 72 hours without failure. Each unit operated stably and the maintenance cost was low.

[0028] Example 3 The difference between this embodiment and Embodiment 1 is as follows: the molecular weight of the anionic polyacrylamide raw material is 12 million, and its mixing mass ratio with deionized water is 0.1:100; the stirring speed of the stirring mechanism 3 is 120 r / min, and the temperature control module 10 controls the dissolution temperature to 35℃; the variable frequency metering pump 15 adjusts the volume ratio of flocculant solution to ferric phosphate solution to 1.5:1000; the specification of the reaction pipeline 13 is DN80, the length is 8m, and the residence time of the material in the pipeline is 60s.

[0029] When this system was applied to a ferric phosphate production line, the material loss rate of the horizontal screw centrifuge was 8.0% before operation, and the solid content of the filtrate was 1.1%. After the system was put into operation, the material loss rate dropped to 0.4%, the solid content of the filtrate dropped to 0.12%, the yield of ferric phosphate product increased by 7.6%, and the product purity was 99.5%, meeting the continuous operation requirements of large-scale industrial production.

[0030] The above are merely embodiments of the present invention. Commonly known structures and characteristics of the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A flocculant dosing system for solving the problem of material leakage in a horizontal screw centrifuge during ferric phosphate production, characterized in that, The system includes a flocculant preparation unit, a metering and conveying unit, a mixing and reaction unit, and a control system. The discharge end of the mixing and reaction unit is connected to the inlet of a horizontal screw centrifuge. The flocculant preparation unit is used to mix and dissolve anionic polyacrylamide raw material with deionized water at a preset mass ratio to prepare a uniform and stable flocculant solution. The anionic polyacrylamide has a molecular weight of 8-12 million, and its mixing mass ratio with deionized water is 0.05-0.15:

100. The metering and conveying unit is used to convey the flocculant solution to the mixing and reaction unit. This metering and conveying unit includes a variable frequency metering pump, a flow sensor, and a buffer tank. The variable frequency metering pump dynamically adjusts the output flow rate according to the feed flow rate of the ferric phosphate solution, so that the volume ratio of the flocculant solution to the ferric phosphate solution is 0.5-1.5:1000. The flow sensor monitors the flocculant solution delivery flow rate in real time and feeds it back to the control system. The mixing reaction unit includes a static mixer and a reaction pipeline. The feed end of the static mixer is connected to the discharge end of the metering and conveying unit and the ferric phosphate solution delivery pipeline. It is equipped with spiral mixing blades inside. The reaction pipeline is 5-8m long and has a diameter of DN50-DN80. The material residence time in the pipeline is 30-60s. The control system includes a PLC controller, a flow acquisition module, and an execution module. The flow acquisition module collects the ferric phosphate solution feed flow rate and the flocculant solution delivery flow rate and transmits them to the PLC controller. The PLC controller controls the frequency conversion speed of the metering pump according to the preset liquid-liquid ratio parameters. The control system is also equipped with an alarm module, which automatically issues an alarm signal when the flow deviation exceeds ±5%.

2. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The flocculant preparation unit includes a dissolving tank, a stirrer, and a temperature control module. The stirrer is located inside the dissolving tank and the stirring speed is 60-120 r / min. The temperature control module controls the dissolving temperature at 25-35℃.

3. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 2, is characterized in that... The dissolving tank is equipped with a feeding port with a dust cover at the top, a slag discharge port at the bottom, and a level gauge on the side wall.

4. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The static mixer is made of 304 stainless steel.

5. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The anionic polyacrylamide can be completely decomposed into carbon dioxide and nitrogen at 600-700℃, leaving no solid foreign matter residue.

6. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The buffer tank of the metering and conveying unit is equipped with an anti-sedimentation stirring structure, and the stirring speed is 30-50 r / min.

7. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The inner wall of the reaction pipeline is provided with an anti-corrosion coating, which is a polytetrafluoroethylene coating with a thickness of 0.5-1.0 mm.

8. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The control system also includes a touch screen, which can display material flow rate, liquid-liquid ratio, dissolution temperature and equipment operating status in real time, and supports manual parameter adjustment.

9. The flocculant dosing system for solving the problem of material leakage in the horizontal screw centrifuge during ferric phosphate production, as described in claim 1, is characterized in that... The flocculant preparation unit is also equipped with an online concentration monitoring module, which monitors the concentration of the flocculant solution in real time and feeds the data back to the PLC controller. When the concentration deviation exceeds ±3%, the PLC controller automatically adjusts the amount of feed or water added.

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