A device and method for concentrating and recovering nickel sulfate from a crude iron phosphate washing water

Abstract

The application provides a device and method for concentrating and recovering nickel sulfate in crude iron phosphate washing water, and belongs to the technical field of industrial wastewater treatment. The device comprises a raw solution buffering unit, a pretreatment unit, a fine filtration unit, a scale inhibition protection unit, a high-pressure concentration unit, a resource recovery unit, a reused water unit and a sludge treatment unit, and each unit is sequentially connected through pipelines, valves and conveying equipment. The application removes suspended solids through an integrated water purifier, and then is subjected to fine membrane filtration and high-pressure acid-resistant RO treatment, so that the concentration and recovery of nickel sulfate in wastewater and the reuse of water are realized, and the problems of high treatment cost, resource waste and unstable operation in the prior art are solved. The device has the beneficial effects of high recovery efficiency, stable operation, high automation degree and the like, and is suitable for resource treatment of iron phosphate production wastewater.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, specifically to a device and method for treating coarse wash water generated during the production of ferric phosphate. Background Technology

[0002] Iron phosphate, a key raw material for lithium-ion battery cathode materials, is synthesized primarily through ammonium, sodium, and iron methods. The production process involves multiple steps, including synthesis, aging and crystallization, and washing, inevitably generating large quantities of complex iron phosphate mother liquor and washing solutions. This wastewater contains high concentrations of sodium (Na). + Fe 3+ Ni 2+ NH4 + PO4 3- and SO4 2- Plasma ion exchange generates a massive amount of water; according to incomplete statistics, producing 1 ton of iron phosphate product produces over 20 tons of wastewater. The direct discharge of large quantities of high-concentration wastewater not only increases the treatment costs for enterprises but also puts pressure on the ecological environment, hindering the sustainable development of the lithium battery industry.

[0003] Currently, the main methods for treating ferric phosphate wastewater include chemical precipitation, membrane separation, and cascade utilization. Chemical precipitation involves adding calcium salts (such as CaCl2) or magnesium salts (such as MgSO4) as precipitants to separate phosphate ions in the wastewater. However, this method only meets low-standard discharge requirements and consumes large amounts of reagents, produces high sludge yields, and incurs high treatment costs. Furthermore, chemical precipitation cannot effectively recover valuable nickel resources from the wastewater, leading to the waste of valuable substances such as nickel sulfate. Membrane separation utilizes membrane technologies such as reverse osmosis (RO) or nanofiltration (NF) for desalination and concentration. While it can improve water quality, membrane modules are susceptible to fouling when faced with high concentrations of pollutants, requiring frequent cleaning, poor operational stability, and shortened lifespan, increasing maintenance costs. In addition, membrane separation has strict requirements for influent water quality, necessitating complex pretreatment; otherwise, membrane pore clogging becomes a significant problem. The cascade utilization method achieves partial reuse by treating wastewater separately according to its quality, but the process is complex, the reuse rate is limited, and valuable resources such as nickel sulfate cannot be systematically recovered, resulting in low overall economic efficiency and resource utilization.

[0004] The English abbreviations, full names, and Chinese names in this instruction manual are as follows:

[0005] RO stands for Reverse Osmosis.

[0006] PLC stands for Programmable Logic Controller.

[0007] NF: its full English name is Nanofiltration, and its Chinese name is nanofiltration.

[0008] SS: its full English name is Suspended Solids, and its Chinese name is suspended solids. Summary of the Invention

[0009] The present invention aims to solve the following common defects existing in chemical precipitation methods, membrane separation methods and cascade utilization methods in the prior art: low treatment efficiency, large consumption of chemicals or energy, and persistently high costs; low resource recovery rate, especially nickel ions and sulfate ions are not effectively concentrated and reused, resulting in resource waste; insufficient operation stability of the device, for example, membrane fouling leads to frequent shutdown for cleaning; the process flow is lengthy, the integration degree is low, and it is difficult to achieve collaborative optimization of wastewater purification and resource recovery.

[0010] To solve the above technical problem, the present invention provides the following technical solutions.

[0011] A device for concentrating and recovering nickel sulfate from crude washing water of iron phosphate comprises a raw liquor caching unit, a pretreatment unit, a fine filtration unit, an anti-scaling protection unit, a high-pressure concentration unit, a resource recovery unit, a reclaimed water unit and a sludge treatment unit, characterized in that the output end of the raw liquor caching unit is connected to the input end of the pretreatment unit, the output end of the pretreatment unit is connected to the input end of the fine filtration unit, the output end of the fine filtration unit is connected to the input end of the anti-scaling protection unit, the output end of the anti-scaling protection unit is connected to the input end of the high-pressure concentration unit, the high-pressure concentration unit is connected to the resource recovery unit and the reclaimed water unit respectively, the sludge discharge ends of the pretreatment unit and the fine filtration unit are both connected to the sludge treatment unit, and the filtrate output end of the sludge treatment unit is connected to the input end of the raw liquor caching unit.

[0012] In a preferred embodiment of the present invention, the raw liquor caching unit comprises a raw liquor caching tank 1 and a raw liquor lifting pump 2, the water inlet of the raw liquor caching tank 1 is connected to the crude washing water discharge port of the iron phosphate production workshop, the water outlet is connected to the input end of the raw liquor lifting pump 2, and the output end of the raw liquor lifting pump 2 is connected to the input end of the pretreatment unit.

[0013] In a preferred embodiment of the present invention, the pretreatment unit comprises an integrated water purifier 3 and an intermediate water tank 4, the water inlet of the integrated water purifier 3 is connected to the output end of the raw liquor lifting pump 2, the water outlet is connected to the water inlet of the intermediate water tank 4 through a pipeline, and the sludge discharge port is connected to the sludge treatment unit; a cyclone reaction zone, a suspension clarification zone, a sludge concentration zone and an inclined tube sedimentation zone are sequentially arranged from bottom to top inside the integrated water purifier 3, and the water outlet of the intermediate water tank 4 is connected to the input end of the fine filtration unit.

[0014] In a preferred embodiment of the present invention, the fine filtration unit includes a heat exchanger 7, a precision membrane filter booster pump 8, a precision membrane filter 9, and a filtered water production tank 10. The inlet of the heat exchanger 7 is connected to the outlet of the intermediate water tank 4, and the outlet is connected to the input end of the precision membrane filter booster pump 8. The output end of the precision membrane filter booster pump 8 is connected to the inlet of the precision membrane filter 9, and the outlet of the precision membrane filter 9 is connected to the inlet of the filtered water production tank 10. The sludge discharge port is connected to the sludge treatment unit. The heat exchanger 7 adopts a shell-and-tube structure and is equipped with cooling circulating water inlet and outlet ports 6. The precision membrane filter 9 has a filtration accuracy of 1μm and uses a ceramic membrane filter assembly inside.

[0015] In a preferred embodiment of the present invention, the scale inhibition protection unit includes a scale inhibitor dosing device 11 and a security filter. The dosing port of the scale inhibitor dosing device 11 is connected to the pipeline between the outlet of the filtered water production tank 10 and the inlet of the security filter. The outlet of the security filter is connected to the input end of the high-pressure concentration unit. The scale inhibitor dosing device 11 includes a scale inhibitor storage tank, a metering pump and a mixer 12. The filtration accuracy of the security filter is 5μm, and the internal filter element is a pleated filter element.

[0016] In a preferred embodiment of the present invention, the high-pressure concentration unit includes a high-pressure pump 13, a high-pressure acid-resistant RO treatment device 14, and an RO concentrate tank 15. The input end of the high-pressure pump 13 is connected to the outlet of the security filter, and the output end is connected to the inlet of the high-pressure acid-resistant RO treatment device 14. The product water outlet of the high-pressure acid-resistant RO treatment device 14 is connected to the recycled water unit, the concentrate outlet is connected to the inlet of the RO concentrate tank 15, and the outlet of the RO concentrate tank 15 is connected to the resource recovery unit. The high-pressure pump 13 is controlled by frequency conversion.

[0017] In a preferred embodiment of the present invention, the resource recovery unit includes a resource recovery booster pump 16 and a resource recovery pipeline. The input end of the resource recovery booster pump 16 is connected to the outlet of the RO concentrate tank 15, and the output end is connected to the raw material recovery pool of the ferric phosphate production workshop through the resource recovery pipeline. The reclaimed water unit includes a reclaimed water tank 17 and a reclaimed water pump 18. The inlet of the reclaimed water tank 17 is connected to the product water outlet of the high-pressure acid-resistant RO treatment device 14, and the outlet is connected to the input end of the reclaimed water pump 18. The output end of the reclaimed water pump 18 is connected to the reclaimed water pipeline network of the ferric phosphate production workshop.

[0018] In a preferred embodiment of the present invention, the sludge treatment unit includes a sludge collection tank 19, a sludge conveying pump 20, and a sludge dewatering device 21. The inlet of the sludge collection tank 19 is connected to the sludge discharge port of the integrated water purifier 3 and the sludge discharge port of the precision membrane filter 9, respectively. The outlet is connected to the input end of the sludge conveying pump 20. The output end of the sludge conveying pump 20 is connected to the input end of the sludge dewatering device 21. The outlet of the sludge dewatering device 21 is connected to the inlet of the raw liquid buffer tank 1. The sludge dewatering device 21 is a plate and frame filter press.

[0019] In a preferred embodiment of the present invention, a control device is further included, which consists of sensors, a controller, and actuators. The sensors include flow sensors, pressure sensors, level sensors, and water quality sensors, which are installed at key locations in each unit. The controller is a PLC programmable logic controller, which is electrically connected to each sensor and actuator. The actuators include frequency converters for each pump body, electric actuators for valves, and metering pumps for scale inhibitor dosing devices.

[0020] In a preferred embodiment of the present invention, the high-pressure acid-resistant RO treatment device 14 includes a membrane module unit, a high-pressure pump unit, a pipeline and valve unit, an electrical control cabinet unit, and auxiliary monitoring components; the membrane module unit includes multiple sets of parallel-arranged membrane housings 141, and the membrane housings 141 are filled with acid-resistant polyamide composite membrane elements; the electrical control cabinet unit integrates a PLC programmable logic controller, a frequency converter, and electrical components such as relays, contactors, and circuit breakers; the auxiliary monitoring components include pressure gauges, thermometers, pressure transmitters, and flow transmitters.

[0021] This invention also provides a method for concentrating and recovering nickel sulfate from coarse ferric phosphate wash water, comprising the following steps: Step 1, preliminary purification of coarse ferric phosphate wash water using multi-stage physical methods to remove suspended solids and minute impurities from the wastewater; Step 2, separation and concentration of nickel sulfate in the wastewater by real-time monitoring of water quality parameters, addition of scale inhibitors, and high-pressure RO concentration treatment; Step 3, reuse of the permeate generated by high-pressure RO treatment in the ferric phosphate production workshop by adjusting water quality and stabilizing transportation.

[0022] In a preferred embodiment of the present invention, step 1 specifically includes: first, the coarse wash water of ferric phosphate is transported to the original solution buffer tank for water quality and quantity conditioning, and then transported to the integrated water purifier for sequential cyclone reaction, suspension clarification, and inclined tube sedimentation to remove large particles and fine suspended solids; then the wastewater enters the heat exchanger to be adjusted to 25-35℃, and then is filtered by a precision membrane filter (filtration accuracy 1μm, internal ceramic membrane filter component) to make the concentration of suspended solids in the effluent ≤5mg / L.

[0023] In a preferred embodiment of the present invention, step 2 specifically includes: first monitoring the pH value (1.0-2.0) and Ni of the filtered wastewater. 2+ Concentration (10000-12000 mg / L), SO4 2- Concentration (30000-35000 mg / L); then add phosphonate acid-resistant scale inhibitor (scale inhibitor and SO4). 2- The mass ratio is 1:5000-1:8000) and the mixture is homogeneous; finally, it is pressurized to 1.5-2.5 MPa by a high-pressure pump and enters a high-pressure acid-resistant RO treatment unit for two-stage concentration, so that the concentrated water Ni 2+ The concentration was increased to 25,000-35,000 mg / L.

[0024] In a preferred embodiment of the present invention, step 3 specifically includes: processing the permeate (Ni) produced by high-pressure RO treatment. 2+ Water with a concentration ≤600mg / L is transported to a recycled water tank, and sodium hydroxide solution is added to adjust the pH value to 6.0-7.0. Then, the recycled water is transported to the ferric phosphate production workshop at a pressure of 0.3-0.5MPa through a frequency-controlled recycled water pump for washing, cooling or liquid preparation processes, with a water resource reuse rate ≥50%.

[0025] In a preferred embodiment of the present invention, step 4 is further included: collecting the sludge generated by the integrated water purifier and the precision membrane filter, first transporting it to a sludge collection tank for natural concentration for 4-6 hours (the concentrated sludge has a water content of 85%-90%); then transporting it to a plate and frame filter press via a sludge transfer pump, and dewatering it for 1.5-2.0 hours under a pressure of 0.6-0.8 MPa, so that the moisture content of the sludge cake is ≤60%; the filtrate generated from dewatering is returned to the original liquid buffer tank for reprocessing, and the sludge cake is transported off-site for disposal after being rendered harmless.

[0026] The device provided by this invention has the following advantages compared with the prior art:

[0027] Through integrated design, the raw solution buffer, pretreatment, fine filtration, scale inhibition and protection, high-pressure concentration, resource recovery, reclaimed water, and sludge treatment units are integrated into one unit, realizing continuous treatment of ferric phosphate coarse wash water. This avoids the process complexity and low efficiency problems caused by the separation of multiple units in existing technologies. Specifically, the integrated water purifier in the pretreatment unit adopts a cyclone reaction, suspension clarification, and inclined tube sedimentation stage structure to effectively remove large suspended solids, reducing the effluent suspended solids concentration to below 5 mg / L. This provides stable feed water conditions for subsequent membrane treatment and reduces the risk of membrane fouling.

[0028] The high-pressure concentration unit uses a high-pressure acid-resistant RO treatment device, combined with the scale inhibitor dosing device of the scale inhibition protection unit, which effectively inhibits scaling on the membrane surface and extends the membrane module cleaning cycle.

[0029] The resource recovery unit and the water reuse unit enable the recycling of nickel sulfate concentrate and production water, and reuse the concentrate in the iron phosphate synthesis reaction, reducing the addition of external reagents and lowering production costs. At the same time, the sludge treatment unit dewaters the sludge to a moisture content of ≤60% using a plate and frame filter press, and returns the filtrate for treatment, avoiding secondary pollution.

[0030] This invention also provides a method for concentrating and recovering nickel sulfate from coarse ferric phosphate wash water, characterized by the following steps: Step 1, the coarse ferric phosphate wash water is transported to the raw liquid buffer unit for water quality and quantity conditioning to balance the influent parameters; Step 2, the conditioned wastewater is transported to the pretreatment unit, where suspended solids are removed through a multi-stage separation process, sludge is collected, and the pretreated effluent is temporarily stored; Step 3, the pretreated effluent is transported to the fine filtration unit, the wastewater temperature is adjusted, and then the effluent is filtered through a high-precision membrane, buffered, and the water quality is monitored; Step 4, a scale inhibitor is added to the filtered effluent and thoroughly mixed, and then impurities are deeply intercepted by a security filter; Step 5, the effluent from the security filter is transported to the high-pressure concentration unit, the high-pressure pump pressure is adjusted in stages, and the membrane modules are operated in sections to recover the concentrated water in stages; Step 6, the concentrated nickel sulfate water is reused in the production workshop, and the high-pressure RO permeate water quality is adjusted before being reused in the production process; Step 7, the sludge generated by each unit is collected, concentrated, and dewatered, and the filtrate is returned to the raw liquid buffer unit for reprocessing.

[0031] In a preferred embodiment of the present invention, the raw liquid buffer unit in step 1 includes a raw liquid buffer tank and a raw liquid booster pump. Step 1 specifically includes: monitoring the water level in the raw liquid buffer tank using a level sensor with a monitoring accuracy of ±5mm; starting the raw liquid booster pump and adjusting the output flow rate using frequency conversion control to stabilize the pipeline pressure at 0.3-0.5MPa; if the pH value of the coarse wash water is lower than 2 or higher than 5, adding 5%-10% sodium hydroxide solution or 5%-10% sulfuric acid solution, and adjusting the pH value to 3-4 after mixing with a mixer; if the suspended solids concentration is higher than 500mg / L, adding a composite flocculant of 50-100mg / L polyaluminum chloride and 1-5mg / L polyacrylamide, and the buffering time in the raw liquid buffer tank is not less than 2 hours.

[0032] In a preferred embodiment of the present invention, the pretreatment unit in step 2 includes an integrated water purifier and an intermediate water tank. Step 2 specifically includes: wastewater entering the integrated water purifier and sequentially passing through a vortex reaction zone, a suspension clarification zone, a sludge thickening zone, and an inclined tube sedimentation zone; the influent flow velocity in the vortex reaction zone is 1.0-1.5 m / s, and the vortex radius is 0.5-1.0 m, removing suspended solids with a particle size ≥10 μm; the residence time in the suspension clarification zone is 30-60 minutes; the cone angle in the sludge thickening zone is 60-90 degrees, and the residence time is... The retention time is 2-4 hours to reduce the sludge moisture content to 95%-99%; the inclined tube sedimentation zone uses honeycomb inclined tubes with an inclination angle of 60 degrees and a length of 1.0-1.5m to ensure that the suspended solids concentration in the effluent is ≤10mg / L; the sludge layer height is monitored by a sludge interface sensor, and sludge is discharged intermittently, with each discharge lasting 1-5 minutes and an interval of 1-2 hours; the pretreated effluent flows into the intermediate water tank, the effective volume of which is 0.5 times the hourly water processing capacity of the integrated water purifier, and the buffer time is not less than 30 minutes.

[0033] In a preferred embodiment of the present invention, the fine filtration unit in step 3 includes a heat exchanger, a precision membrane filter booster pump, a precision membrane filter, and a filtered product water tank. Step 3 specifically includes: wastewater entering the heat exchanger, which is a shell-and-tube structure; adjusting the wastewater temperature to 25-35℃ by regulating the cooling circulating water flow rate, with a heat exchange efficiency ≥85% and a temperature regulation accuracy of ±1℃; starting the precision membrane filter booster pump, and stabilizing the influent flow rate at 10-20 m³ / h using frequency conversion control. 3 Wastewater enters the precision membrane filter at a rate of 1 μm per hour. The precision membrane filter uses a ceramic membrane filter assembly. A pressure sensor monitors the pressure difference across the membrane. When the pressure difference exceeds 0.3 MPa, backwashing is initiated. The backwashing pressure is 0.2-0.3 MPa, the time is 5-10 minutes, and the interval is 2-4 hours, ensuring that the suspended solids concentration in the filtered water is ≤5 mg / L. The filtered water flows into the filtered water tank, whose effective volume is 0.5 times the hourly water volume of the precision membrane filter, and the buffer time is not less than 30 minutes.

[0034] In a preferred embodiment of the present invention, the scale inhibition and protection unit in step 4 includes a scale inhibitor dosing device and a security filter. Step 4 specifically includes: monitoring the sulfate ion concentration, pH value, and temperature of the filtered water using a water quality sensor, monitoring the wastewater flow rate using a flow sensor, adding a phosphonate acid-resistant scale inhibitor based on the monitoring data, and using a metering pump with a dosing accuracy of ±1%; mixing the scale inhibitor and wastewater in a static mixer with a mixing efficiency ≥95%, the mixer having multiple layers of spiral blades that can be adjusted to match the flow rate; the wastewater entering the security filter, which has a filtration accuracy of 5μm and uses pleated filter elements internally, monitoring the pressure difference across the filter using a pressure sensor, and initiating backwashing when the pressure difference exceeds 0.2MPa, with a backwashing pressure of 0.1-0.2MPa and a time of 3-5 minutes, to ensure that the suspended solids concentration in the effluent is ≤1mg / L.

[0035] In a preferred embodiment of the present invention, the high-pressure concentration unit in step 5 includes a high-pressure pump, a high-pressure acid-resistant RO treatment device, and an RO concentrate tank. Step 5 specifically includes: starting the high-pressure pump with a head of 800m, and adjusting the output pressure in stages through frequency conversion control; initially, when the nickel sulfate concentration is low, the pressure is set to 1.5-1.8MPa; when the concentrate nickel sulfate concentration reaches 50g / L, the pressure is set to 1.8-2.0MPa; when the concentration reaches 100g / L, the pressure is set to 2.0-2.2MPa; when the concentration reaches... When the concentration is above 150g / L, the pressure is set to 2.2-2.5MPa; the membrane module unit of the high-pressure acid-resistant RO treatment device is divided into front section, middle section and back section, with the ratio of membrane shells in each section being 1:2:1. In the initial stage, all sections are opened, the back section is closed when the concentration reaches 50g / L, and the middle section is closed when the concentration reaches 100g / L; the concentration of the concentrate in the RO concentrate tank is monitored by a concentration sensor. Low-concentration concentrate is returned to the high-pressure acid-resistant RO treatment device for re-concentration, while medium and high-concentration concentrates are respectively transported to the raw material recovery pool in the production workshop.

[0036] In a preferred embodiment of the present invention, step 6 specifically includes: transporting medium and high concentration nickel sulfate concentrate from the RO concentrate tank to the raw material recovery pool in the ferric phosphate production workshop via a resource recovery booster pump; monitoring the concentrate concentration and pH value in the raw material recovery pool using a water quality sensor; adjusting the concentrate to the process requirements using a stirring device and a dosing device; achieving a nickel sulfate recovery rate ≥90%; the permeate from the high-pressure acid-resistant RO treatment device flows into the recycled water tank; adding sodium hydroxide solution to adjust the pH value to 6.0-7.0; starting the recycled water pump; and using frequency conversion control to transport the recycled water to the workshop at a pressure of 0.3-0.5 MPa; using high-purity permeate for washing and general-purity permeate for cooling; achieving a water resource reuse rate ≥70%.

[0037] In a preferred embodiment of the present invention, the sludge treatment unit in step 7 includes a sludge collection tank, a sludge conveying pump, and a sludge dewatering device. Step 7 specifically includes: sludge generated by the integrated water purifier and precision membrane filter is conveyed to the sludge collection tank; the water level is monitored by a level sensor; the sludge conveying pump is started; and the conveying flow rate is adjusted by frequency conversion control; the stirring device in the sludge collection tank operates continuously, performing stirring operations without interruption; the sludge is conveyed to the sludge dewatering device, which is a plate and frame filter press with a pressing pressure of 1.0-1.5 MPa, a feed pressure of 0.8-1.0 MPa, and a single dewatering time of 1-2 hours, so that the moisture content of the sludge cake is ≤60%; the dewatered filtrate is returned to the original liquid buffer tank through a pipeline; if the suspended solids concentration of the filtrate is higher than 50 mg / L, it is returned to the sludge collection tank for reprocessing; and the sludge cake is transported off-site after being rendered harmless.

[0038] In a preferred embodiment of the present invention, in the membrane module unit of the high-pressure acid-resistant RO treatment device, each membrane shell is filled with an acid-resistant polyamide composite membrane element. The membrane element has a spiral wound structure and consists of a membrane sheet, an inlet water channel partition, a product water channel partition, and connecting materials. When the pressure difference in the membrane module area suddenly increases, the inlet water valve of that area is closed, and the product water in the recycled water tank is used for flushing. The flushing pressure is 0.5-0.8 MPa and the time is 10-15 minutes. If the pressure difference does not recover after flushing, an alarm signal is issued.

[0039] In a preferred embodiment of the present invention, the entire method achieves fully automated control through a control device, which includes sensors, a PLC programmable logic controller, and actuators. The sensors include flow sensors, pressure sensors, level sensors, water quality sensors, and concentration sensors, which are installed at key locations in each unit. The actuators include frequency converters for each pump, electric actuators for valves, and metering pumps for scale inhibitor dosing devices. The PLC programmable logic controller receives sensor signals, automatically adjusts operating parameters, and issues an alarm and initiates emergency adjustments when parameters are abnormal.

[0040] The method provided by this invention has the following advantages over the prior art:

[0041] This invention employs a multi-stage physical purification process to achieve gradient impurity removal from coarse wash water of ferric phosphate: a cyclone reaction first removes over 60% of large suspended particles (≥10μm in diameter, such as unreacted iron salts and phosphate precipitates); suspension clarification and inclined tube sedimentation further retain fine impurities of 5-10μm and ≥1μm; finally, after filtration through a 1μm precision ceramic membrane, the effluent suspended solids (SS) concentration is ≤5mg / L, fully meeting the influent water quality requirements of high-pressure acid-resistant RO treatment devices. Compared to existing technologies with simple pretreatment processes and incomplete impurity removal, this method effectively avoids subsequent RO membrane module clogging due to suspended solids accumulation, extends the membrane cleaning cycle (from 4-6 hours in the existing technology to 8-12 hours), reduces membrane maintenance costs and downtime frequency, and ensures continuous and stable system operation.

[0042] In the nickel sulfate separation and concentration stage, the method of this invention significantly improves resource recovery efficiency through real-time water quality monitoring, scale inhibitor addition, and a two-stage high-pressure RO concentration design: firstly, by monitoring the pH value (1.0-2.0) and Ni... 2+ Concentration (10000-12000 mg / L), SO4 2- Concentration (30000-35000 mg / L) provides data support for scale inhibitor dosage and pressure control; secondly, acid-resistant phosphonate scale inhibitors are selected specifically (based on the ratio of scale inhibitor to SO4). 2-(Added at a mass ratio of 1:5000-1:8000) effectively inhibits calcium carbonate and calcium sulfate scaling on the RO membrane surface, ensuring membrane retention performance; finally, through gradient pressure control of 1.5-2.5 MPa and two-stage RO concentration, the concentrated water Ni 2+ With a concentration increased to 25,000-35,000 mg / L, it can be directly or proportionally recycled to the ferric phosphate synthesis process, replacing fresh nickel sulfate raw materials. Compared to the shortcomings of existing chemical precipitation methods that cannot recover nickel resources and traditional membrane separation methods that have low concentration ratios, this method increases the nickel sulfate recovery rate to over 90%, which can reduce the company's nickel sulfate procurement costs by 30%-40% annually.

[0043] In the water resource utilization stage, the method of this invention maximizes water recycling through water quality fine-tuning, stable transportation, and multi-process reuse design: high-pressure RO permeate (Ni 2+ Water with a concentration ≤600mg / L is adjusted to pH 6.0-7.0 with sodium hydroxide solution and then pumped to the production workshop via a frequency converter-controlled recycled water pump (0.3-0.5MPa stable pressure) for washing, cooling, and liquid preparation processes, achieving a water reuse rate ≥85%. Compared to existing cascade utilization methods with a reuse rate of only 50%-60% and limited reuse processes, this method can reduce fresh water consumption by more than 40% annually, lowering industrial water costs, reducing wastewater discharge, alleviating environmental pressure, and aligning with the green and low-carbon development trend of the lithium battery industry.

[0044] For the sludge generated during pretreatment and fine filtration, the processing flow of this invention is as follows: the sludge is first naturally concentrated in a sludge collection tank for 4-6 hours (moisture content reduced to 85%-90%), then dewatered using a plate and frame filter press at 0.6-0.8 MPa pressure until the sludge cake moisture content is ≤60%. The dewatered filtrate is returned to the original liquid buffer tank for reprocessing, and the sludge cake is transported off-site after being rendered harmless. Compared with the problems of secondary pollution caused by direct discharge of sludge or incomplete dewatering (moisture content ≥80%) in existing technologies, this method achieves sludge reduction (volume reduction of more than 60%) and filtrate resource utilization, with no risk of wastewater or sludge discharge, meeting environmental emission standards and avoiding pollution to soil and water bodies.

[0045] The entire method achieves fully automated control through a PLC programmable logic controller: sensors collect flow rate, pressure, liquid level, and water quality (SS, Ni) data in real time. 2+ The controller automatically adjusts pump frequency, valve operation, and scale inhibitor dosage based on parameters such as concentration and pH value. It also automatically alarms and initiates emergency adjustments (e.g., returning to re-filtration when suspended solids exceed limits, or starting and stopping the pump when the liquid level is abnormal) in case of abnormalities. This not only reduces the workload of operators but also minimizes the risk of equipment damage and substandard treatment results due to unstable operation, thereby improving enterprise production management efficiency. Attached Figure Description

[0046] Figure 1 A schematic diagram of the overall structure of the nickel sulfate concentration and recovery device in the crude washing water of ferric phosphate provided by the present invention;

[0047] Figure 2 This is a schematic diagram of the high-pressure acid-resistant RO treatment device in the nickel sulfate concentration and recovery device for ferric phosphate crude wash water provided by the present invention.

[0048] Figure 3 The flowchart of the method for concentrating and recovering nickel sulfate from crude ferric phosphate washing water provided by the present invention is shown.

[0049] The labels in the attached figures are as follows: 1: Raw material buffer tank; 2: Raw material booster pump; 3: Integrated water purifier; 4: Intermediate water tank; 5: Sludge treatment unit; 6: Cooling circulating water inlet and outlet; 7: Heat exchanger; 8: Precision membrane filter booster pump; 9: Precision membrane filter; 10: Filter product water tank; 11: Antiscalant dosing device; 12: Mixer; 13: High-pressure pump; 14: High-pressure acid-resistant RO treatment device; 15: RO concentrate tank; 16: Resource recovery booster pump; 17: Reclaimed water tank; 18: Reclaimed water pump; 19: Sludge collection tank; 20: Sludge transfer pump; 21: Sludge dewatering device; 141: Membrane housing; 142: High-pressure pump in the high-pressure acid-resistant RO treatment device. Detailed Implementation

[0050] 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.

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0052] like Figure 1 As shown, in the first embodiment of the present invention, a nickel sulfate concentration and recovery device for ferric phosphate coarse wash water is provided. The device includes a raw solution buffer unit, a pretreatment unit, a fine filtration unit, a scale inhibition and protection unit, a high-pressure concentration unit, a resource recovery unit, a reclaimed water unit, and a sludge treatment unit. Each unit is connected in sequence through pipes, valves, and conveying equipment to realize the integrated functions of purifying ferric phosphate coarse wash water, concentrating and recovering nickel sulfate, and reusing water resources.

[0053] The outlet of the raw liquid buffer tank of the raw liquid buffer unit is connected to the input of the raw liquid booster pump via a pipe, and the output of the raw liquid booster pump is connected to the inlet of the integrated water purifier of the pretreatment unit via a pipe. The outlet of the integrated water purifier of the pretreatment unit is connected to the inlet of the intermediate water tank via a pipe, and the outlet of the intermediate water tank is connected to the inlet of the heat exchanger of the fine filtration unit via a pipe. The outlet of the heat exchanger is connected to the input of the precision membrane filter booster pump via a pipe, and the output of the precision membrane filter booster pump is connected to the inlet of the precision membrane filter via a pipe. The outlet of the precision membrane filter is connected to the inlet of the filtered product water tank via a pipe. The outlet of the filtered product water tank of the fine filtration unit is connected to the pipe where the scale inhibitor dosing device is located via a pipe. After the scale inhibitor is added and mixed, it is connected to the inlet of the security filter via a pipe, and the outlet of the security filter is connected to the input of the high-pressure pump of the high-pressure concentration unit via a pipe. The outlet of the scale inhibition and protection unit's security filter is connected to the input of the high-pressure pump via a pipeline. The output of the high-pressure pump is connected to the inlet of the high-pressure acid-resistant RO treatment system via a pipeline. The product water outlet of the high-pressure acid-resistant RO treatment system is connected to the inlet of the recycled water tank of the recycled water unit via a pipeline. The concentrate outlet is connected to the inlet of the RO concentrate tank via a pipeline. The outlet of the RO concentrate tank of the high-pressure concentration unit is connected to the input of the resource recovery booster pump via a pipeline. The output of the resource recovery booster pump is connected to the raw material recovery pool of the ferric phosphate production workshop of the resource recovery unit via a resource recovery pipeline. The product water outlet of the high-pressure acid-resistant RO treatment system of the high-pressure concentration unit is connected to the inlet of the recycled water tank of the recycled water unit via a pipeline. The outlet of the recycled water tank is connected to the input of the recycled water pump via a pipeline. The output of the recycled water pump is connected to the recycled water network of the ferric phosphate production workshop via a pipeline. The sludge discharge port of the integrated water purifier in the pretreatment unit and the sludge discharge port of the precision membrane filter in the fine filtration unit are both connected to the inlet of the sludge collection tank in the sludge treatment unit through pipes. The outlet of the sludge collection tank is connected to the input end of the sludge conveying pump through a pipe. The output end of the sludge conveying pump is connected to the input end of the sludge dewatering system through a pipe. The outlet of the sludge dewatering system is connected to the inlet of the raw liquid buffer tank through a pipe.

[0054] The raw solution buffer unit includes a raw solution buffer tank 1 and a raw solution booster pump 2. The inlet of the raw solution buffer tank 1 is connected to the coarse wash water discharge outlet of the ferric phosphate production workshop through a pipeline, and the outlet is connected to the input end of the raw solution booster pump 2 through a pipeline. The output end of the raw solution booster pump 2 is connected to the input end of the pretreatment unit through a pipeline. This unit is used to buffer the coarse wash water of ferric phosphate discharged from the workshop and stably transport it to the subsequent treatment unit, balance the water quality and quantity of the incoming water, and avoid abnormal operation of subsequent equipment due to fluctuations in the incoming water.

[0055] The pretreatment unit includes an integrated water purifier 3 and an intermediate water tank 4. The inlet of the integrated water purifier 3 is connected to the output of the raw liquid booster pump 2, and its outlet is connected to the inlet of the intermediate water tank 4 via a pipe. The sludge discharge port of the integrated water purifier 3 is connected to the sludge treatment unit 5 via a pipe, and the outlet of the intermediate water tank 4 is connected to the input of the fine filtration unit via a pipe. Preferably, the integrated water purifier 3 integrates a vortex reaction zone, a suspension clarification zone, a sludge concentration zone, and an inclined tube sedimentation zone, with each functional zone arranged sequentially from bottom to top to form a graded treatment structure. The intermediate water tank 4 is used to temporarily store the effluent from the integrated water purifier.

[0056] The fine filtration unit includes a heat exchanger 7, a precision membrane filter booster pump 8, a precision membrane filter 9, and a filtered water production tank 10. The inlet of the heat exchanger 7 is connected to the outlet of the intermediate water tank 4. The outlet is connected to the input end of the precision membrane filter booster pump 8 through a pipe. The output end of the precision membrane filter booster pump 9 is connected to the inlet of the precision membrane filter 9 through a pipe. The outlet of the precision membrane filter 9 is connected to the inlet of the filtered water production tank 10 through a pipe. The sludge discharge port of the precision membrane filter 9 is connected to the sludge treatment unit 5 through a pipe.

[0057] Preferably, the heat exchanger 7 adopts a shell-and-tube structure and includes a cooling circulating water inlet and outlet 6, which is used to adjust the wastewater temperature to a range suitable for subsequent membrane filtration, so as to avoid the filtration performance of the membrane being affected by excessively high or low temperatures; the precision membrane filter has a filtration accuracy of 1μm and uses a ceramic membrane filter component inside, which has the characteristics of acid resistance, fouling resistance and long service life; the filtered water tank 10 is used to collect the effluent from the precision membrane filter.

[0058] The scale inhibition and protection unit includes a scale inhibitor dosing device 11 and a security filter (not shown in the figure). The dosing port of the scale inhibitor dosing device 11 is connected to the pipe between the outlet of the filtered water product tank 10 and the inlet of the security filter via a pipe. The inlet of the security filter is connected to the outlet of the filtered water product tank 10 via a pipe, and the outlet is connected to the input end of the high-pressure concentration unit via a pipe. In a more preferred embodiment, the scale inhibitor dosing device 11 includes a scale inhibitor storage tank, a metering pump, and a mixer 12. The metering pump automatically adjusts the scale inhibitor dosage according to the influent flow rate. The mixer 12 ensures that the scale inhibitor is fully mixed with the wastewater to prevent scaling of the membrane module of the subsequent high-pressure concentration unit. The security filter has a filtration accuracy of 5μm and uses a pleated filter element inside to intercept any small suspended solids and colloids that may remain in the wastewater, protecting the membrane module of the high-pressure pump and the high-pressure concentration unit from damage.

[0059] The high-pressure concentration unit includes a high-pressure pump 13, a high-pressure acid-resistant RO treatment device 14, and an RO concentrate tank 15. The input end of the high-pressure pump 13 is connected to the outlet of the security filter through a pipeline, and the output end is connected to the inlet of the high-pressure acid-resistant RO treatment device 14 through a pipeline. The product water outlet of the high-pressure acid-resistant RO treatment device 14 is connected to the recycled water unit through a pipeline. The concentrate outlet of the high-pressure acid-resistant RO treatment device 14 is connected to the inlet of the RO concentrate tank 14 through a pipeline. The outlet of the RO concentrate tank 14 is connected to the resource recovery unit through a pipeline.

[0060] More preferably, the high-pressure pump 13 adopts frequency conversion control and automatically adjusts the output pressure according to the inlet water pressure requirements of the high-pressure acid-resistant RO treatment device to ensure that the membrane module operates stably under the set pressure.

[0061] More preferably, such as Figure 2 As shown, the high-pressure acid-resistant RO treatment device 14 includes a membrane module unit, a high-pressure pump unit, a pipeline and valve unit, an electrical control cabinet unit, and auxiliary monitoring components.

[0062] The membrane module unit includes multiple sets of parallel-arranged membrane shells 141, each filled with an acid-resistant polyamide composite membrane element. The membrane element has a spiral wound structure, consisting of a membrane sheet, a feed water channel separator, a product water channel separator, and connecting materials. The dense separation layer of the membrane sheet has the characteristic of selectively permeating water molecules, and can efficiently retain Ni. 2+ SO4 2- Plasma and H2SO4, among other substances. Each membrane housing is sealed with an end plate and a sealing ring to prevent high-pressure water leakage and ensure effective separation of permeate and concentrate.

[0063] The high-pressure pump 142 is located in the middle right of the system. It adopts a vertical multistage centrifugal pump structure, and the pump inlet and outlet are connected to the pipeline through flanges.

[0064] The pipelines include inlet pipelines, product water pipelines, concentrate pipelines, flushing pipelines, etc.

[0065] The electrical control cabinet unit comprises two cabinets, upper and lower, located in the middle of the system. It integrates a PLC programmable logic controller for receiving sensor signals and outputting control commands; a frequency converter for adjusting the speed of the high-pressure pump to achieve flow and pressure control; and electrical components such as relays, contactors, and circuit breakers.

[0066] The auxiliary monitoring components include pressure gauges, thermometers, pressure transmitters, and flow transmitters. The flow transmitters convert pressure and flow signals into electrical signals, which are then transmitted to the PLC for automated control.

[0067] After pretreatment, the wastewater passes through a security filter and then enters the inlet of high-pressure pump 142 via the inlet pipe. After being pressurized by the high-pressure pump, the wastewater is transported to the inlet of membrane module 141 via the inlet pipe and connected to the inlets of multiple membrane housings. Under high pressure, the wastewater enters the membrane housing, where water molecules permeate through the membranes to form permeate. This permeate is collected in the membrane element's permeate center pipe and then transported to the recycled water tank via the permeate pipe. The retained concentrate is concentrated inside the membrane housing and then discharged into the RO concentrate tank via the concentrate pipe.

[0068] To maintain system stability, the high-pressure acid-resistant RO treatment unit 14 also includes a flushing pipe: when the membrane module is fouled, flushing water enters the membrane housing through the flushing pipe to flush the membrane element in reverse or forward direction, and the flushing wastewater is discharged through the concentrate pipe and enters the sludge treatment system or the feed buffer tank.

[0069] The electrical control cabinet is connected to the high-pressure pump, electric valves, sensors, etc. via cables to form an electrical control network. The PLC receives sensor signals and sends instructions to the high-pressure pump frequency converter and electric valves to achieve automated operation; at the same time, it can be connected to the factory's central control system through a communication interface to achieve remote monitoring and data transmission.

[0070] The RO concentrate tank 15 is used to collect the concentrate produced by the high-pressure acid-resistant RO treatment device.

[0071] The resource recovery unit includes a resource recovery booster pump 16 and a resource recovery pipeline. The input end of the resource recovery booster pump 16 is connected to the outlet of the RO concentrate tank 15 through a pipeline, and the output end is connected to the raw material recovery pool of the iron phosphate production workshop through the resource recovery pipeline. It is used to transport the concentrated high-concentration nickel sulfate solution to the workshop for reuse, so as to realize the recycling of resources.

[0072] The water recycling unit includes a water recycling tank 17 and a water recycling pump 18. The inlet of the water recycling tank 17 is connected to the product water outlet of the high-pressure acid-resistant RO treatment device 14 through a pipeline, and the outlet is connected to the input end of the water recycling pump 18 through a pipeline. The output end of the water recycling pump 18 is connected to the water recycling network of the iron phosphate production workshop through a pipeline, so as to reuse the purified product water in the washing, cooling and other processes of the production workshop, thereby realizing the recycling of water resources.

[0073] The sludge treatment unit includes a sludge collection tank 19, a sludge transfer pump 20, and a sludge dewatering device 21. The inlet of the sludge collection tank 19 is connected to the sludge discharge port of the integrated water purifier 3 and the sludge discharge port of the precision membrane filter 9 through pipes. The outlet is connected to the input end of the sludge transfer pump 20 through a pipe. The output end of the sludge transfer pump 20 is connected to the input end of the sludge dewatering device 21 through a pipe. The outlet of the sludge dewatering device 21 is connected to the inlet of the raw liquid buffer tank 1 through a pipe. The sludge cake outlet is connected to the sludge transportation device through a pipe.

[0074] The sludge collection tank 19 is used to centrally collect the sludge produced by the pretreatment unit and the fine filtration unit. The sludge conveying pump delivers the sludge quantitatively to the sludge dewatering device. The sludge dewatering device 21 adopts a plate and frame filter press to dewater the sludge to a sludge cake state. The filtrate after dewatering is returned to the original liquid buffer tank for reprocessing. The sludge cake is transported off-site for disposal after being treated to render it harmless, so as to avoid secondary pollution.

[0075] In addition, the nickel sulfate concentration and recovery unit in the coarse ferric phosphate wash water also includes a control device (not shown in the figure). The control device consists of sensors, a controller, and actuators. The sensors include flow sensors, pressure sensors, level sensors, and water quality sensors, which are used to detect indicators such as SS, Ni concentration, and pH value, and are installed at key locations in each unit. The controller adopts a PLC programmable logic controller, which is electrically connected to each sensor and actuator to receive sensor signals and control the operation of the actuators. The actuators include frequency converters for each pump, electric actuators for valves, and metering pumps for scale inhibitor dosing devices, etc., to realize the automated operation and parameter adjustment of the unit.

[0076] The working process of the nickel sulfate concentration and recovery unit in the crude washing water of ferric phosphate is as follows.

[0077] The coarse wash water generated in the ferric phosphate production workshop is first transported through pipelines to the raw material buffer tank. The raw material buffer tank buffers the wastewater, balancing the quality and quantity of the influent, and preventing subsequent treatment units from being affected by sudden changes in influent concentration or flow rate. When the water level in the raw material buffer tank reaches the set threshold, the control device starts the raw material lift pump, which delivers the buffered coarse wash water to the integrated water purifier at a stable flow rate.

[0078] The coarse wash water entering the integrated water purifier first enters the vortex reaction zone. Under the action of centrifugal force, large suspended solids such as unreacted iron salts and phosphate precipitates in the wastewater are separated to the bottom of the separation zone, initially removing large particulate impurities. Subsequently, the wastewater enters the suspension clarification zone. Under the action of gravity, fine suspended solids gradually settle to the bottom of the tank, while the upper clarified liquid continues to flow upward. The settled sludge is concentrated in the sludge thickening zone to reduce the sludge moisture content. The concentrated sludge is discharged through the sludge discharge port at the bottom of the integrated water purifier and enters the sludge collection tank. After the vortex reaction, suspension clarification, and sludge thickening, the wastewater enters the inclined tube sedimentation zone. The inclined tube sedimentation zone uses honeycomb inclined tubes as the sedimentation medium and utilizes the principle of shallow sedimentation to greatly improve the sedimentation efficiency of fine suspended solids, further removing suspended solids in the wastewater and initially purifying the effluent water quality.

[0079] The effluent from the integrated water purifier flows into the intermediate water tank through pipes. The intermediate water tank temporarily stores the pre-treated wastewater to ensure a stable influent flow to the subsequent fine filtration unit. Based on the liquid level signal in the intermediate water tank, the control device starts the heat exchanger and the precision membrane filter booster pump. The wastewater in the intermediate water tank first enters the heat exchanger, which adjusts the wastewater temperature to the optimal filtration temperature range of 25-35℃ to prevent excessively high temperatures from causing membrane module aging or excessively low temperatures from affecting the membrane's permeability. The temperature-adjusted wastewater is then transported to the precision membrane filter via the precision membrane filter booster pump.

[0080] Inside the precision membrane filter, wastewater passes through a ceramic membrane filtration module with a precision of 1μm. The ceramic membrane has a uniform microporous structure and good acid resistance, which can effectively intercept residual suspended solids, colloids and some large molecular organic matter in the wastewater, so that the suspended solids concentration of the effluent is ≤5mg / L, which fully meets the influent water quality requirements of the subsequent high-pressure acid-resistant RO treatment device. A small amount of sludge generated during the operation of the precision membrane filter is discharged through the sludge discharge port and enters the sludge collection tank to avoid sludge accumulation on the membrane surface and causing membrane fouling.

[0081] The effluent from the precision membrane filter flows into the product water tank. Based on the liquid level in the product water tank and the influent flow rate, the control device starts the metering pump of the scale inhibitor dosing device. The scale inhibitor in the scale inhibitor storage tank is quantitatively added to the wastewater pipeline by the metering pump. It is fully mixed with the wastewater through the mixer. The scale inhibitor can inhibit the formation of scale such as calcium carbonate and calcium sulfate on the surface of the RO membrane, extending the cleaning cycle and service life of the RO membrane. The wastewater after adding the scale inhibitor continues to be transported to the security filter through the pipeline. The pleated filter element in the security filter further intercepts any small impurities and colloidal particles that may remain in the wastewater, preventing them from entering the high-pressure pump and RO membrane module, causing equipment wear or membrane fouling.

[0082] Wastewater filtered by a security filter enters a high-pressure pump, which is frequency-controlled. Based on the inlet pressure requirements of the high-pressure acid-resistant RO treatment unit, the pump pressurizes the wastewater to a working pressure of 1.5-2.5 MPa, ensuring that the wastewater can smoothly pass through the RO membrane module and achieve effective separation. The pressurized wastewater then enters the high-pressure acid-resistant RO treatment unit. The acid-resistant polyamide composite membrane module within this unit has selective permeability, allowing water molecules to pass through while efficiently removing Ni from the wastewater. 2+ SO4 2- Plasma and substances such as H2SO4.

[0083] The permeate produced by the high-pressure acid-resistant RO treatment unit flows into the recycled water tank through the permeate outlet. The recycled water tank buffers the purified water. When the water level in the recycled water tank reaches the set value, the control device starts the recycled water pump to transport the purified water to the recycled water pipeline network of the ferric phosphate production workshop for use in production processes such as washing, cooling, and liquid preparation, thus realizing the recycling of water resources. The concentrate produced by the high-pressure acid-resistant RO treatment unit flows into the RO concentrate tank through the concentrate outlet. The RO concentrate tank temporarily stores the concentrate. When the water level in the concentrate tank reaches the set value, the control device starts the resource recovery booster pump to transport the concentrate through the resource recovery pipeline to the raw material recovery pool in the production workshop for reuse in the ferric phosphate synthesis reaction, thus realizing the resource recovery of nickel sulfate and sulfuric acid.

[0084] Throughout the entire process, the sludge generated by the integrated water purifier and the precision membrane filter is collected through pipelines to a sludge collection tank. After sedimentation and concentration, the sludge in the collection tank is then transported to a sludge dewatering device by the control unit. The sludge dewatering device uses a plate and frame filter press to dewater the sludge to a cake state with a moisture content of ≤60% through high-pressure pressing. The filtrate generated during the dewatering process is returned to the original liquid buffer tank through pipelines and re-enters the treatment device for processing to avoid pollution caused by filtrate discharge. After the dewatered cake is rendered harmless, it is transported to a designated location for disposal by a sludge transport device.

[0085] The control device monitors the operating parameters of each unit throughout the process, including the liquid level of each water tank, the flow rate, pressure, temperature, and water quality of wastewater. When any parameter is abnormal, the control device automatically issues an alarm signal and adjusts the operating status of relevant equipment according to a preset program, such as adjusting the pump frequency and closing relevant valves, to ensure stable and safe operation of the device. At the same time, the control device has data recording and remote monitoring functions, which allows operators to keep abreast of the device's operating status and perform maintenance and management.

[0086] In another embodiment of the present invention, a method for concentrating and recovering nickel sulfate from crude ferric phosphate wash water is provided, such as... Figure 3 As shown, the specific steps include:

[0087] Step 1: Buffer the coarse wash water with ferric phosphate and adjust the water quality, flow rate, and pressure to stabilize the influent. This step utilizes the sensors, controllers, and actuators of the stock solution buffer unit and control device to achieve buffering and pressure stabilization of the coarse wash water and pre-treatment conditioning of the water quality, providing stable influent conditions for subsequent staged pretreatment. Step 1 further includes the following steps:

[0088] Step 1-1: Temporarily store the coarse wash water and monitor the water level, flow rate, and various water quality indicators in real time.

[0089] The coarse wash water generated in the ferric phosphate production workshop is piped to a raw material buffer tank, where it is temporarily stored to balance fluctuations in the influent water quality and quantity. The control system uses a level sensor to monitor the water level in the buffer tank in real time, a flow sensor to monitor the influent flow rate of the coarse wash water, and water quality sensors to monitor the suspended solids concentration, pH value, nickel ion concentration, sulfate ion concentration, and temperature parameters in the coarse wash water. Each sensor transmits the monitored signals to a PLC (Programmable Logic Controller) in real time. The PLC analyzes the received parameter signals in real time to determine whether the influent water quality is within a preset stable range. If the water quality parameters exceed the preset range, the PLC issues an early warning signal, providing data support for subsequent targeted proton adjustment steps.

[0090] Preferably, the buffering time of the raw solution in the buffer tank is not less than 2 hours to fully balance fluctuations in water quality and quantity; the monitoring accuracy of the level sensor is ±5mm, and the measurement range of the flow sensor is 0-100m³. 3 The water quality sensor has a pH measurement range of 1-14, a suspended solids concentration measurement accuracy of ±1 mg / L, and a nickel ion concentration measurement accuracy of ±0.1 mg / L, ensuring the accuracy of the monitoring data.

[0091] Steps 1-2: Adjust the frequency of the raw liquid booster pump and the valve to stabilize the water flow and pressure.

[0092] The PLC controller controls the operation of the feedstock booster pump based on the liquid level in the feedstock buffer tank and the rated processing flow rate of the subsequent staged pretreatment steps. The feedstock booster pump uses frequency converter control; the PLC controller adjusts the pump's output flow rate by regulating the frequency converter, ensuring a stable flow of coarse wash water from the feedstock buffer tank to the pretreatment unit. Simultaneously, a pressure sensor monitors the pipeline pressure at the feedstock booster pump's output. When the pipeline pressure exceeds a preset range, the PLC controller automatically adjusts the pump's frequency or controls the opening of the electric valves on the pipeline to ensure the output pressure remains stable between 0.3 and 0.5 MPa.

[0093] To illustrate, when the liquid level in the raw material buffer tank is higher than the set upper limit, the PLC controller increases the frequency of the raw material booster pump to increase the output flow rate; when the liquid level is lower than the set lower limit, the frequency of the raw material booster pump is reduced to decrease the output flow rate; when the pipeline pressure is too high, the opening of the electric valve is appropriately reduced, or the pump frequency is reduced, to avoid the pressure from excessively high pressure impacting subsequent pipelines and equipment; when the pressure is too low, the opening of the electric valve is increased, or the pump frequency is increased, to ensure stable inlet water pressure for subsequent pretreatment units.

[0094] Steps 1-3: Based on the water quality monitoring results, add chemicals to adjust the pH value and suspended solids state.

[0095] The PLC controller determines whether water quality conditioning is needed based on parameters such as pH value and suspended solids concentration of the coarse wash water monitored by water quality sensors. If the pH value of the coarse wash water is lower than 2 or higher than 5, the PLC controller activates the water quality conditioning actuator. This actuator is a dosing device installed on the pipeline between the outlet of the raw solution buffer tank and the raw solution booster pump. The dosing device includes an acid storage tank, an alkali storage tank, a metering pump, and a mixer. The metering pump is electrically connected to the PLC controller.

[0096] When the pH value is too low, the metering pump adds a quantitative amount of alkaline solution into the pipeline according to the instructions of the PLC controller. The alkaline solution is preferably a 5%-10% sodium hydroxide solution. When the pH value is too high, the metering pump adds a quantitative amount of acid solution. The acid solution is preferably a 5%-10% sulfuric acid solution. The reagent is thoroughly mixed with the coarse wash water through a mixer to adjust the pH value to the optimal pretreatment range of 3-4. If the suspended solids concentration of the coarse wash water is higher than 500 mg / L, the PLC controller starts the flocculant dosing device. The flocculant is preferably a composite agent of polyaluminum chloride and polyacrylamide. The dosage concentration of polyaluminum chloride is 50-100 mg / L, and the dosage concentration of polyacrylamide is 1-5 mg / L. It is added quantitatively into the pipeline through the metering pump. After mixing by the mixer, the fine suspended solids in the wastewater form flocs.

[0097] Without limitation, the metering pump has an addition accuracy of ±1%, the mixer has a mixing efficiency of not less than 95%, ensuring that the reagent and wastewater are fully mixed, and the fluctuation range of the water quality parameters after conditioning is controlled within ±5%.

[0098] Step 2: Use a multi-stage separation process to remove suspended solids from the coarse wash water, treat the sludge, and stabilize the effluent.

[0099] This step utilizes the integrated water purifier, intermediate water tank, and related sensors and actuators of the control device in the pretreatment unit to efficiently remove suspended solids, colloids, and some impurities from the coarse wash water through multi-stage separation and regulation, providing high-quality feed water for the subsequent fine filtration step. Step 2 further includes the following steps:

[0100] Step 2-1: Remove impurities of different particle sizes by sequentially passing them through cyclone, clarification, concentration, and inclined tube sedimentation.

[0101] After conditioning in step 1, the coarse wash water is transported to the integrated water purifier through pipelines. The integrated water purifier is equipped with a vortex reaction zone, a suspended clarification zone, a sludge concentration zone and an inclined tube sedimentation zone from bottom to top. The wastewater undergoes four stages of separation treatment in the integrated water purifier.

[0102] First, the wastewater enters the cyclone reaction zone. Under the action of centrifugal force, large suspended particles with a diameter greater than 10μm, such as unreacted iron salts and phosphate precipitates, are separated to the bottom of the separation zone, thus initially removing large particulate impurities. The influent flow rate of the cyclone reaction zone is preferably 1.0-1.5m / s, and the cyclone radius is preferably 0.5-1.0m to ensure that the centrifugal force is sufficient to separate large suspended particles.

[0103] Subsequently, the wastewater enters the suspended clarification zone, where the preferred residence time is 30-60 minutes to ensure sufficient settling of the flocs. The settled sludge then enters the sludge thickening zone, which employs a conical structure with a preferred cone angle of 60-90 degrees. Under gravity, the sludge is thickened, reducing its moisture content. The moisture content of the thickened sludge is controlled between 90% and 95%. The preferred residence time in the sludge thickening zone is 2-4 hours to ensure effective thickening.

[0104] The supernatant from the sludge thickening zone enters the inclined tube sedimentation zone. This zone uses honeycomb inclined tubes as the sedimentation medium, with an optimal inclination angle of 60 degrees and a preferred length of 1.0-1.5m. Utilizing the principle of shallow sedimentation, this significantly improves the settling efficiency of fine suspended solids, further removing suspended solids from the wastewater and reducing the effluent suspended solids concentration to below 10mg / L. In this sub-step, suspended solids sensors from the control device are installed at the outlets of the cyclone reaction zone, the suspended solids clarification zone, and the inclined tube sedimentation zone, respectively, to monitor the effluent suspended solids concentration in each zone in real time. The monitoring signals are transmitted to the PLC controller, which adjusts the influent flow rate of the integrated water purifier based on the monitoring data to ensure stable treatment performance in each separation zone.

[0105] Step 2-2: Monitor the sludge layer height, intermittently discharge and concentrate the sludge produced by the integrated water purifier.

[0106] The sludge generated in the swirl reaction zone, suspension clarification zone, and sludge concentration zone of the integrated water purifier is collected at the bottom of the sludge concentration zone. The sludge interface sensor of the control device is installed in the sludge concentration zone to monitor the height of the sludge layer in real time.

[0107] When the sludge layer height reaches the set upper limit, the PLC controller activates the electric sludge discharge valve at the bottom of the integrated water purifier, transporting the concentrated sludge to the sludge collection tank through pipelines. When the sludge layer height falls below the set lower limit, the PLC controller closes the electric sludge discharge valve, stopping sludge discharge. To avoid carrying away too much supernatant during sludge discharge, intermittent sludge discharge is adopted, with each discharge lasting 1-5 minutes. The discharge interval is adjusted according to the amount of sludge produced, preferably 1-2 hours. Simultaneously, based on the sludge moisture content data monitored by the sludge sensor, if the sludge moisture content is higher than 95%, the PLC controller extends the residence time in the sludge concentration zone to promote sludge coagulation and concentration; if the sludge moisture content is lower than 90%, the discharge interval is shortened to prevent sludge from caking in the concentration zone.

[0108] Steps 2-3: Temporarily store the pretreated effluent and adjust the flow rate, pH value and temperature to suit subsequent treatment.

[0109] After treatment in the inclined tube sedimentation zone, the effluent flows into the intermediate water tank through a pipeline. The level sensor of the control device monitors the water level in the intermediate water tank, the flow sensor monitors the influent flow rate, and the water quality sensor monitors the suspended solids concentration, pH value, and temperature parameters of the effluent.

[0110] Based on monitoring data, the PLC controller adjusts the outlet flow rate of the integrated water purifier to ensure that the water level in the intermediate water tank remains stable within the set range, preventing malfunctions in subsequent fine filtration steps due to fluctuations in the inlet flow rate. If the concentration of suspended solids in the effluent from the intermediate water tank exceeds 10 mg / L, the PLC controller reduces the inlet flow rate of the integrated water purifier, extending the residence time of the wastewater within the purifier, or activates the stirring device in the intermediate water tank to prevent the sedimentation and accumulation of suspended solids. If the pH value deviates from the range of 3-4, the PLC controller activates the fine-tuning dosing device in the intermediate water tank to quantitatively add acid or alkali solution, adjusting the pH value to the set range. If the temperature is above 35℃ or below 20℃, the PLC controller sends a signal to the heat exchanger in the subsequent fine filtration step in advance to prepare for temperature adjustment.

[0111] The effective volume of the intermediate water tank is preferably 0.5 times the hourly water processing capacity of the integrated water purifier, ensuring that the water outlet buffer time is not less than 30 minutes, further stabilizing the water quality.

[0112] Step 3: Adjust the wastewater temperature, filter it through a membrane, buffer it, and monitor the quality of the produced water.

[0113] Using the heat exchanger, precision membrane filter booster pump, precision membrane filter, filtered product water tank, and related components of the fine filtration unit, the pretreated wastewater is temperature-regulated and filtered with high precision to remove residual suspended solids and colloids, meeting the influent requirements of the subsequent high-pressure concentration step. Step 3 further includes the following steps:

[0114] Step 3-1: Adjust the wastewater temperature to a range suitable for subsequent filtration using a heat exchanger.

[0115] The pretreated water from the intermediate water tank is transported to the heat exchanger via pipelines. The heat exchanger adopts a shell-and-tube structure and is equipped with cooling circulating water inlet and outlet. Temperature sensors of the control device are installed at the inlet, outlet, and cooling circulating water inlet and outlet of the heat exchanger, respectively, to monitor the wastewater temperature and cooling circulating water temperature in real time and transmit the monitoring signals to the PLC controller.

[0116] The PLC controller adjusts the flow rate of the cooling circulating water based on the wastewater temperature data to maintain the optimal filtration temperature range of 25-35℃. When the wastewater inlet temperature is higher than 35℃, the PLC controller increases the flow rate of the cooling circulating water to improve heat exchange efficiency and lower the wastewater temperature; when the wastewater inlet temperature is lower than 25℃, the PLC controller decreases the flow rate of the cooling circulating water to reduce heat exchange efficiency and raise the wastewater temperature; if the cooling circulating water temperature is too high and affects the heat exchange effect, the PLC controller activates the auxiliary cooling device of the cooling circulating water to ensure stable heat exchange performance.

[0117] The heat exchanger should preferably have a heat exchange efficiency of no less than 85%, and the temperature regulation accuracy should be controlled within ±1℃ to avoid excessively high temperatures causing aging of the precision membrane components, or excessively low temperatures affecting the water permeability of the membrane.

[0118] Step 3-2: Use a precision membrane filter to intercept residual impurities and backwash regularly to ensure filtration effectiveness.

[0119] Temperature-regulated wastewater is pumped to the precision membrane filter via a booster pump. This booster pump is frequency-controlled; the PLC controller adjusts the pump frequency based on the intermediate water tank level and the inlet pressure of the precision membrane filter, maintaining a stable inlet flow rate of 10-20 m³ / h. 3 / h.

[0120] The precision membrane filter has a filtration accuracy of 1μm and uses a ceramic membrane filter assembly internally. The ceramic membrane has a uniform microporous structure and good acid resistance, which can effectively intercept residual suspended solids, colloids, and some large molecular organic matter in wastewater. The pressure sensors of the control device are installed at the inlet and outlet of the precision membrane filter to monitor the pressure difference across the membrane in real time, while the water quality sensor monitors the suspended solids concentration at the outlet.

[0121] When the pressure difference across the membrane is less than 0.1 MPa, the PLC controller appropriately increases the frequency of the precision membrane filter booster pump to increase the influent flow rate and improve filtration efficiency. When the pressure difference is greater than 0.3 MPa, it indicates that the membrane surface has become fouled to a certain extent. The PLC controller then reduces the booster pump frequency and the influent flow rate, while simultaneously starting the backwashing device of the precision membrane filter. The backwash water is the product water in the filter product water tank. The backwashing pressure is 0.2-0.3 MPa, the backwashing time is 5-10 minutes, and the backwashing interval is adjusted according to the pressure difference, preferably 2-4 hours.

[0122] During the filtration process, if the suspended solids concentration at the outlet is higher than 5 mg / L, the PLC controller will extend the backwash time or increase the number of backwashes to ensure that the suspended solids concentration of the filtered water is ≤5 mg / L, fully meeting the influent water quality requirements of the subsequent high-pressure acid-resistant RO treatment device.

[0123] Step 3-3: Buffer and filter the produced water, and monitor indicators such as water level, pH value and conductivity.

[0124] The effluent from the precision membrane filter flows into the filter product water tank through a pipeline. The level sensor of the control device monitors the water level in the filter product water tank, and the water quality sensor monitors the pH value, conductivity and suspended solids concentration of the product water. Each sensor transmits the monitoring data to the PLC controller in real time.

[0125] When the water level in the product water tank reaches the set upper limit, the PLC controller reduces the frequency of the precision membrane filter booster pump, decreasing the influent flow rate. When the water level falls below the set lower limit, the booster pump frequency is increased, increasing the influent flow rate to ensure a stable water level in the product water tank. If the pH value of the product water deviates from the range of 3-4, the PLC controller activates the fine-tuning dosing device in the product water tank to add a measured amount of acid or alkali solution for adjustment. If the conductivity exceeds the preset range, the PLC controller determines that the membrane module may be damaged and issues an alarm signal to remind the operator to check. The effective volume of the product water tank is preferably 0.5 times the hourly water processing capacity of the precision membrane filter, ensuring a product water buffer time of no less than 30 minutes.

[0126] Step 4: Calculate the dosage of scale inhibitor based on water quality, mix it, and then pass it through a security filter to deeply intercept impurities.

[0127] By utilizing the scale inhibitor dosing device, security filter, and related components of the control device in the scale inhibition protection unit, scale inhibitor dosing and deep interception of wastewater are achieved, preventing scaling and fouling of the membrane module in the subsequent high-pressure concentration step. Step 4 further includes the following steps:

[0128] Step 4-1: Determine and adjust the dosage of scale inhibitor based on water quality and flow data.

[0129] The control device's water quality sensors monitor the sulfate ion concentration, pH value, and temperature of the effluent from the filtered product water tank, while the flow sensor monitors the wastewater flow rate. Each sensor transmits the monitoring data to the PLC controller. Based on the monitoring data and a preset formula for calculating the scale inhibitor dosage, the PLC controller calculates the required scale inhibitor dosage.

[0130] The preferred scale inhibitor is a phosphorus-containing scale inhibitor. Its dosage is positively correlated with the concentration of sulfate ions in the wastewater, positively correlated with temperature, and negatively correlated with pH value.

[0131] Schematic illustration: The formula for calculating the scale inhibitor dosage is based on a linear correlation with wastewater quality parameters, ensuring that the dosage matches the scaling risk. Based on the calculation results, the PLC controller sends control commands to the metering pump of the scale inhibitor dosing device, adjusting the pump's output flow rate to achieve targeted scale inhibitor dosing. The preferred dosing accuracy of the metering pump is ±1%.

[0132] Step 4-2: Use a static mixer to thoroughly mix the scale inhibitor with the wastewater.

[0133] The scale inhibitor is quantitatively added to the pipeline between the outlet of the filter product water tank and the inlet of the security filter via a metering pump. A mixer is installed on the pipeline. The mixer is a static mixer with multiple layers of spiral blades inside.

[0134] When wastewater and scale inhibitor flow through the pipeline, the helical blades of the mixer create strong turbulent mixing, ensuring thorough mixing of the scale inhibitor and wastewater with a mixing efficiency of no less than 95%. A flow sensor in the control device monitors the wastewater flow rate in the pipeline. The PLC controller adjusts the internal blade angle of the mixer based on the flow data. When the flow rate is high, the blade angle is increased to enhance mixing intensity; when the flow rate is low, the blade angle is decreased to reduce flow resistance. Simultaneously, a water quality sensor installed on the mixer outlet pipe monitors the turbidity of the mixed wastewater. If the turbidity exceeds 1 NTU, it indicates insufficient mixing. The PLC controller then increases the output pressure of the metering pump or extends the length of the mixing pipeline to ensure thorough mixing of the scale inhibitor and wastewater, preventing localized excessively high or low scale inhibitor concentrations that could affect the scale inhibition effect.

[0135] Step 4-3: Use a security filter to further intercept impurities and protect downstream high-voltage equipment and membrane modules.

[0136] The wastewater, after being mixed with scale inhibitor, is transported through pipelines to the security filter. The security filter has a filtration accuracy of 5μm and uses pleated filter elements inside, which can further intercept any small suspended solids, colloidal particles and undissolved scale inhibitor crystals that may remain in the wastewater, protecting the subsequent high-pressure pump and high-pressure acid-resistant RO membrane module from damage.

[0137] The pressure sensors of the control device are installed at the inlet and outlet of the safety filter to monitor the pressure difference before and after the filter in real time. When the pressure difference is lower than 0.05MPa, it indicates that the filter element is clean, and the PLC controller maintains the current inlet water flow. When the pressure difference is higher than 0.2MPa, it indicates that the filter element has been blocked, and the PLC controller starts the backwashing device of the safety filter. The backwash water is the product water in the filter product water tank. The backwashing pressure is 0.1-0.2MPa, and the backwashing time is 3-5 minutes. If the pressure difference is still higher than 0.2MPa after backwashing, the PLC controller issues an alarm signal to remind the operator to replace the filter element.

[0138] The water from the security filter is transported to the high-pressure concentration unit through pipelines. A water quality sensor monitors the suspended solids concentration in the water from the security filter to ensure that the suspended solids concentration in the water is ≤1mg / L, thus providing high-quality feed water for the high-pressure concentration step.

[0139] Step 5: Adjust the high-pressure pump pressure in stages, operate the membrane modules in zones, and recover the concentrated wastewater in stages. Utilizing the high-pressure pump, high-pressure acid-resistant RO treatment device, RO concentrate tank, and related components of the control device in the high-pressure concentration unit, high-efficiency concentration of nickel sulfate and long-term operation of the RO membrane modules are achieved through pressure gradient regulation, zoned operation of the membrane modules, and staged recovery of the concentrate. Step 5 further includes the following steps:

[0140] Step 5-1: Dynamically adjust the output pressure of the high-pressure pump according to the concentration of the concentrate.

[0141] The effluent from the security filter is transported to the high-pressure pump through a pipeline. The high-pressure pump is controlled by a frequency converter. The PLC controller sets multiple pressure gradients based on the influent concentration of the high-pressure acid-resistant RO treatment device, the condition of the membrane module, and the concentration target, and controls the output pressure of the high-pressure pump.

[0142] In the initial stage, the nickel sulfate concentration in the wastewater is low. The PLC controller sets the output pressure of the high-pressure pump to 1.5-1.8 MPa to ensure that water molecules can efficiently permeate the RO membrane and improve the water production rate. When the nickel sulfate concentration in the RO concentrate tank reaches 50 g / L, the PLC controller adjusts the output pressure of the high-pressure pump to 1.8-2.0 MPa to increase the pressure difference across the membrane and improve the concentration efficiency. When the nickel sulfate concentration in the concentrate reaches 100 g / L, the PLC controller adjusts the output pressure to 2.0-2.2 MPa to further increase the concentration ratio. When the nickel sulfate concentration in the concentrate reaches above 150 g / L, the PLC controller adjusts the output pressure to 2.2-2.5 MPa to ensure that the nickel sulfate is fully concentrated while avoiding excessive pressure that could damage the membrane module.

[0143] The concentration sensor of the control device is installed in the RO concentrate tank to monitor the nickel sulfate concentration of the concentrate in real time. The monitoring data is transmitted to the PLC controller, which automatically switches the pressure gradient based on the concentration data to achieve dynamic pressure control. Simultaneously, pressure transmitters are installed at the output of the high-pressure pump and the inlet of the RO membrane module to monitor the pipeline pressure in real time. If the pressure exceeds the set range, the PLC controller immediately adjusts the frequency of the high-pressure pump or closes the electric valve.

[0144] Step 5-2: Switch the membrane module operating area according to the concentrate concentration.

[0145] The membrane module unit of the high-pressure acid-resistant RO treatment device includes multiple sets of parallel membrane shells. Each set of membrane shells is filled with acid-resistant polyamide composite membrane elements. The membrane module unit is divided into three regions: the front section, the middle section, and the back section. Each region contains several sets of membrane shells. Each region is connected to the inlet water pipe, the product water pipe, and the concentrate water pipe through electric valves. The PLC controller controls the operating status of each region.

[0146] In the initial stage, when the wastewater concentration is low, the PLC controller opens the electric valves in all areas, allowing the wastewater to enter the membrane housings in all three areas simultaneously, achieving high-flow-rate treatment and improving the permeate production rate. When the nickel sulfate concentration in the RO concentrate tank reaches 50 g / L, the PLC controller closes the inlet valves of the downstream area, opening only the membrane housings in the upstream and midstream areas to reduce the number of membrane modules in operation and improve the concentration efficiency per unit membrane area. When the nickel sulfate concentration in the concentrate reaches 100 g / L, the PLC controller closes the inlet valves of the midstream area, opening only the membrane housings in the upstream area, concentrating pressure and flow for deep concentration to ensure that the concentrate concentration meets the recovery requirements.

[0147] Meanwhile, the flow transmitter and pressure transmitter of the control device monitor the inlet water flow, product water flow, and pressure difference across the membrane in each zone. If the pressure difference across the membrane in a certain zone suddenly increases, it indicates that the membrane module in that zone has become fouled. The PLC controller immediately closes the inlet water valve of that zone and starts the flushing device for that zone. The flushing water is recycled product water from the water tank, the flushing pressure is 0.5-0.8 MPa, and the flushing time is 10-15 minutes. If the pressure difference returns to normal after flushing, the inlet water valve of that zone is reopened; if the pressure difference still does not return to normal, an alarm signal is issued to remind the operator to perform chemical cleaning.

[0148] The preferred ratio of membrane shells in each region is 1:2:1 for the front section: middle section: rear section, to ensure a balance between processing efficiency and membrane module protection at different concentration stages.

[0149] Step 5-3: Collect concentrate according to concentration, and recycle low-concentration concentrate for further concentration.

[0150] The concentrate from the high-pressure acid-resistant RO treatment unit is transported to the RO concentrate tank through pipelines. The concentration sensor of the control unit monitors the nickel sulfate concentration of the concentrate in real time, and the PLC controller divides the concentrate into three levels based on the concentration data.

[0151] For low-concentration concentrate, the PLC controller starts the circulation pump in the RO concentrate tank, which transports the low-concentration concentrate back to the inlet of the high-pressure acid-resistant RO treatment unit through pipelines. After mixing with the effluent from the security filter, it is concentrated again to increase the concentration ratio of nickel sulfate. For medium-concentration concentrate, the PLC controller starts the resource recovery booster pump, which transports the medium-concentration concentrate through the resource recovery pipeline to the raw material recovery pool in the ferric phosphate production workshop for supplementing the auxiliary material for the ferric phosphate synthesis reaction. For high-concentration concentrate, the PLC controller adjusts the frequency of the resource recovery booster pump and controls the flow rate, transporting the high-concentration concentrate to the high-concentration area of ​​the raw material recovery pool, where it is directly used as a raw material for the synthesis reaction, reducing the amount of external nickel sulfate added.

[0152] Meanwhile, the liquid level sensor of the control device monitors the water level of the RO concentrate tank. When the water level reaches the set upper limit, the PLC controller prioritizes the delivery of high-concentration concentrate, followed by medium-concentration concentrate, to ensure the stability of the RO concentrate tank water level. When the water level is lower than the set lower limit, the PLC controller reduces the frequency of the circulation pump to reduce the circulation volume of low-concentration concentrate and avoid insufficient inlet flow of the high-pressure acid-resistant RO treatment device.

[0153] Step 6: Recycle and reuse the high-concentration nickel sulfate concentrate, and reuse the purified water for production as needed.

[0154] By utilizing relevant components of the resource recovery unit and the water reuse unit, the graded recovery and recycling of nickel sulfate concentrate and purified water are achieved. Step 6 further includes the following steps:

[0155] Step 6-1: Transport the qualified nickel sulfate concentrate to the raw material recovery pool in the production workshop.

[0156] The resource recovery booster pump delivers medium and high concentration concentrates from the RO concentrate tank to the raw material recovery pool in the ferric phosphate production workshop. The flow sensor of the control device monitors the delivery flow rate, and the PLC controller adjusts the frequency of the resource recovery booster pump based on the liquid level sensor data of the raw material recovery pool to ensure that the water level in the raw material recovery pool remains stable within the set range.

[0157] Water quality sensors in the raw material recovery tank monitor the nickel sulfate concentration and pH value of the concentrated water. If the concentration or pH value deviates from the production process requirements, the PLC controller starts the stirring device and dosing device in the raw material recovery tank to adjust the concentration and pH, ensuring that the recovered nickel sulfate concentrate meets the process requirements of the iron phosphate synthesis reaction.

[0158] The resource recovery pipeline is equipped with a check valve to prevent the solution in the raw material recovery tank from flowing back into the RO concentrate tank, ensuring the safety of the recovery process. The recovery rate of nickel sulfate is preferably no less than 90%, and the reuse rate of concentrate is no less than 85%, reducing the company's raw material procurement costs.

[0159] Step 6-2: Adjust the quality of the purified water and transport it to the workshop for reuse according to the process requirements.

[0160] The permeate from the high-pressure acid-resistant RO treatment unit is transported to the recycled water tank through pipelines. The water quality sensors of the control unit monitor the conductivity, pH value and suspended solids concentration of the permeate to ensure that the permeate water quality meets the requirements for reuse in production.

[0161] When the water level in the recycled water tank reaches the set upper limit, the PLC controller starts the recycled water pump, which transports the purified permeable water through the recycled water pipeline network to different reuse points in the ferric phosphate production workshop. High-purity permeable water is sent to the washing process for washing ferric phosphate products; general-purity permeable water is sent to the cooling process for equipment cooling; and permeable water with a pH value deviating from the set range is first sent to the adjustment area of ​​the recycled water tank, where the pH value is adjusted by a dosing device before reuse. The flow sensor in the control device monitors the flow rate at each reuse point, and the PLC controller adjusts the frequency of the recycled water pump and the opening of the electric valves according to the needs of each reuse point to ensure a stable water supply.

[0162] The reuse rate of recycled water should preferably be no less than 70%, which will significantly reduce the company's consumption of fresh water.

[0163] Step 7: Collect and process the sludge generated by each unit, and return the filtrate after dewatering for reprocessing.

[0164] By utilizing the sludge collection tank, sludge transfer pump, sludge dewatering device, and control device components of the sludge treatment unit, centralized sludge treatment and filtrate recirculation for reprocessing are achieved, avoiding secondary pollution. Step 7 further includes the following steps:

[0165] Step 7-1: Collect sludge centrally, stir it regularly, and transport it quantitatively to the dewatering device.

[0166] Sludge discharged from the sludge outlets of the integrated water purifier and the precision membrane filter is transported through pipelines to a sludge collection tank. A level sensor in the control unit monitors the water level in the sludge collection tank. When the water level reaches the set upper limit, the PLC controller starts the sludge transfer pump, quantitatively delivering the sludge to the sludge dewatering device. The sludge transfer pump uses frequency conversion control. The PLC controller adjusts the pump frequency and controls the flow rate based on the water level in the sludge collection tank and the processing capacity of the sludge dewatering device, ensuring stable water intake to the sludge dewatering device. A stirring device is installed in the sludge collection tank. The PLC controller periodically starts the stirring device for 10-15 minutes at 1-hour intervals to prevent sludge sedimentation and caking in the collection tank, ensuring smooth sludge transport.

[0167] Step 7-2: Use a plate and frame filter press to pressurize and dewater the sludge, reducing the moisture content of the sludge cake.

[0168] The sludge transfer pump transports the sludge to the sludge dewatering unit, which uses a plate and frame filter press. A PLC controller controls the operation of the plate and frame filter press.

[0169] First, start the pressing device of the filter press to press the plates and frames together at a pressure of 1.0-1.5 MPa. Then, open the feed valve, and the sludge enters the filter chamber between the plates and frames under the pressure of the sludge conveying pump for filtration and dewatering. After the filter chamber is full of sludge, maintain the feed pressure at 0.8-1.0 MPa for 1-2 hours. After dewatering, close the feed valve, start the pressure relief device to release the pressure on the plates and frames, and then start the plate pulling device to pull the plates and frames apart, allowing the sludge cake to fall into the sludge transport device.

[0170] The pressure sensor in the control device monitors the pressing pressure and feed pressure of the filter press. If the pressure is lower than the set value, the PLC controller starts the pressurizing device to supplement the pressure; if the pressure is higher than the set value, the pressure relief device is activated to ensure pressure stability. The moisture content of the sludge cake after dewatering is ≤60%, which meets the requirements for harmless treatment and off-site disposal.

[0171] Step 7-3: Transfer the filtrate produced by dehydration to the original liquid buffer tank for reprocessing.

[0172] The filtrate produced by the sludge dewatering unit is transported to the raw liquid buffer tank via pipeline. Water quality sensors in the control system monitor the suspended solids (SLS) and nickel ion concentrations in the filtrate. If the SLS concentration exceeds 50 mg / L, the PLC controller transfers the filtrate to the sludge collection tank for further dewatering. If the SLS concentration is ≤50 mg / L, it is directly transferred to the raw liquid buffer tank, mixed with newly introduced coarse wash water, and then reprocessed, achieving closed-loop filtrate recovery and preventing nickel ion loss. A flow sensor is installed on the filtrate return pipeline. The PLC controller adjusts the filtrate return flow rate based on the liquid level in the raw liquid buffer tank to ensure the water level remains stable within the set range.

[0173] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0174] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for concentrating and recovering nickel sulfate based on a nickel sulfate concentration and recovery device in ferric phosphate crude wash water, characterized in that, The nickel sulfate concentration and recovery device in the coarse washing water of ferric phosphate includes a raw solution buffer unit, a pretreatment unit, a fine filtration unit, a scale inhibition and protection unit, a high-pressure concentration unit, a resource recovery unit, a reclaimed water unit, and a sludge treatment unit. The output end of the raw liquid buffer unit is connected to the input end of the pretreatment unit, the output end of the pretreatment unit is connected to the input end of the fine filtration unit, the output end of the fine filtration unit is connected to the input end of the scale inhibition and protection unit, the output end of the scale inhibition and protection unit is connected to the input end of the high pressure concentration unit, the high pressure concentration unit is connected to the resource recovery unit and the recycled water unit respectively, the sludge discharge ends of the pretreatment unit and the fine filtration unit are both connected to the sludge treatment unit, and the filtrate output end of the sludge treatment unit is connected to the input end of the raw liquid buffer unit; the raw liquid buffer unit includes a raw liquid buffer tank (1) and a raw liquid lift pump (2), the inlet of the raw liquid buffer tank (1) is connected to the coarse wash water discharge outlet of the iron phosphate production workshop, the outlet is connected to the input end of the raw liquid lift pump (2), and the output end of the raw liquid lift pump (2) is connected to the input end of the pretreatment unit; the pretreatment unit includes an integrated water purifier (3) and an intermediate water tank (4), the inlet of the integrated water purifier (3) is connected to the output end of the raw liquid lift pump (2). The outlet is connected to the inlet of the intermediate water tank (4) through a pipe, and the sludge discharge port is connected to the sludge treatment unit. The integrated water purifier (3) is arranged from bottom to top as a vortex reaction zone, a suspended clarification zone, a sludge concentration zone and an inclined tube sedimentation zone. The outlet of the intermediate water tank (4) is connected to the input end of the fine filtration unit. The fine filtration unit includes a heat exchanger (7), a precision membrane filter lift pump (8), a precision membrane filter (9) and a filter product water tank (10). The inlet of the heat exchanger (7) is connected to the outlet of the intermediate water tank (4), and the outlet is connected to the input end of the precision membrane filter lift pump (8). The output end of the precision membrane filter lift pump (8) is connected to the inlet of the precision membrane filter (9). The outlet of the precision membrane filter (9) is connected to the inlet of the filter product water tank (10), and the sludge discharge port is connected to the sludge treatment unit. The heat exchanger (7) adopts a shell-and-tube structure and is equipped with a cooling circulating water inlet and outlet (6). The precision membrane filter (9) includes a ceramic membrane filter assembly. The high-pressure concentration unit includes a high-pressure acid-resistant RO treatment device (14). In the membrane module unit of the high-pressure acid-resistant RO treatment device (14), the acid-resistant polyamide composite membrane element filled inside each membrane shell (141) is a spiral wound structure, consisting of a membrane sheet, an inlet flow channel mesh, a product water flow channel mesh, and connecting materials. The device also includes a control unit, which consists of sensors, a controller, and an actuator; the control unit is connected to the factory's central control system via a communication interface. The method includes the following steps: Step 1: The coarse wash water of ferric phosphate is transported to the original solution buffer unit for water quality and quantity conditioning to balance the influent parameters; Step 2: The conditioned wastewater is transported to the pretreatment unit, where suspended solids are removed through a multi-stage separation process, sludge is collected, and the pretreated effluent is temporarily stored. Step 3: The pretreated effluent is sent to the fine filtration unit, the wastewater temperature is adjusted and then filtered through a high-precision membrane, the filtered water is buffered and the water quality is monitored. Step 4: Add scale inhibitor to the filtered water and mix thoroughly, then pass it through a security filter to deeply intercept impurities; Step 5: Transport the effluent from the security filter to the high-pressure concentration unit, adjust the pressure of the high-pressure pump in stages and operate the membrane modules in sections, and recover the concentrated water in stages; start the high-pressure pump (13), and adjust the output pressure in stages through frequency conversion control: when the nickel sulfate concentration is low in the initial stage, the pressure is set to 1.5-1.8MPa; when the nickel sulfate concentration of the concentrated water reaches 50g / L, the pressure is set to 1.8-2.0MPa; when the concentration reaches 100g / L, the pressure is set to 2.0-2.2MPa; when the concentration reaches 150g / L or more, the pressure is set to 2.2-2.5MPa; the membrane module unit of the high-pressure acid-resistant RO treatment device (14) is divided into front section, middle section and back section areas, and the area membrane shell (1) 41) The quantity ratio is 1:2:

1. In the initial stage, all areas are opened. When the concentration reaches 50g / L, the downstream section is closed. When the concentration reaches 100g / L, the middle section is closed. When the pressure difference across a certain area of ​​the membrane module unit suddenly increases, the inlet valve of that area is closed. The recycled water in the tank is used for flushing. The flushing pressure is 0.5-0.8MPa and the time is 10-15 minutes. If the pressure difference does not recover after flushing, an alarm signal is issued. The concentration of the RO concentrate tank (15) is monitored by the concentration sensor. The concentrate is divided into three levels: low, medium and high. The low concentration concentrate is returned to the high pressure acid resistant RO treatment device (14) for re-concentration. The medium and high concentration concentrates are respectively sent to the raw material recovery pool in the production workshop. Step 6: The concentrated nickel sulfate solution is reused in the production workshop, and the high-pressure RO permeate water quality is adjusted before being reused in the production process. Step 7: Collect the sludge generated by each unit, and after concentration and dewatering, return the filtrate to the original liquid buffer unit for reprocessing.

2. The method for concentrating and recovering nickel sulfate according to claim 1, characterized in that, Step 1 includes: monitoring the water level of the raw liquid buffer tank (1) through a liquid level sensor, starting the raw liquid booster pump (2), adjusting the output flow rate through frequency conversion control, and stabilizing the pipeline pressure at 0.3-0.5MPa; if the pH value of the coarse wash water is lower than 2 or higher than 5, add 5%-10% sodium hydroxide solution or 5%-10% sulfuric acid solution, mix through a mixer (12) and adjust the pH value to 3-4; if the suspended solids concentration is higher than 500mg / L, add a composite flocculant of 50-100mg / L polyaluminum chloride and 1-5mg / L polyacrylamide, and the buffering time of the raw liquid buffer tank (1) is not less than 2 hours.

3. The method for concentrating and recovering nickel sulfate according to claim 2, characterized in that, Step 2 includes: wastewater enters the integrated water purifier (3) and passes through the vortex reaction zone, the suspension clarification zone, the sludge thickening zone, and the inclined tube sedimentation zone in sequence; the inlet flow velocity of the vortex reaction zone is 1.0-1.5m / s and the vortex radius is 0.5-1.0m to remove suspended solids with a particle size ≥10μm; the wastewater stays in the suspension clarification zone for 30-60 minutes; the cone angle of the sludge thickening zone is 60-90 degrees and the residence time is 2-4 hours to reduce the sludge moisture content to 95%-99%; the inclined tube sedimentation zone uses honeycomb inclined tubes with an inclination angle of 60 degrees and a length of 1.0-1.5m to make the effluent suspended solids concentration ≤10mg / L; the sludge layer height is monitored by the sludge interface sensor, and sludge is discharged intermittently, each time for 1-5 minutes and at intervals of 1-2 hours; the pretreated effluent flows into the intermediate water tank (4), the effective volume of the intermediate water tank (4) is 0.5 times the hourly water treatment capacity of the integrated water purifier (3), and the buffer time is not less than 30 minutes.

4. The method for concentrating and recovering nickel sulfate according to claim 3, characterized in that, Step 3 includes: wastewater entering heat exchanger (7), which is a shell-and-tube structure. The wastewater temperature is adjusted to 25-35℃ by adjusting the cooling circulating water flow rate, with a heat exchange efficiency ≥85% and a temperature adjustment accuracy of ±1℃; the precision membrane filter booster pump (8) is started, and the influent flow rate is controlled by frequency conversion, so that the wastewater enters the precision membrane filter (9); the precision membrane filter (9) has a filtration accuracy of 1μm and uses ceramic membrane filter components inside. The pressure difference before and after the membrane is monitored by a pressure sensor. When the pressure difference is higher than 0.3MPa, backwashing is started. The backwashing pressure is 0.2-0.3MPa and the time is... For 5-10 minutes, with intervals of 2-4 hours, the concentration of suspended solids in the filtered water is ≤5mg / L; the filtered water flows into the filtered water tank (10), the effective volume of the filtered water tank (10) is 0.5 times the water volume processed per hour by the precision membrane filter (9), and the buffer time is not less than 30 minutes; step 4 includes: monitoring the sulfate ion concentration, pH value and temperature of the filtered water through a water quality sensor, monitoring the wastewater flow rate through a flow sensor, adding phosphonate acid-resistant scale inhibitors according to the monitoring data, and the metering pump adding with an accuracy of ±1%; the scale inhibitor and wastewater are mixed through a static mixer (12).

5. The method for concentrating and recovering nickel sulfate according to claim 4, characterized in that, The high-pressure acid-resistant RO treatment device (14) also includes a flushing pipe through which flushing water enters the membrane housing (141) to flush the membrane elements in reverse or forward direction. The device also includes a control device consisting of sensors, a controller, and actuators. The sensors include flow sensors, pressure sensors, level sensors, and water quality sensors, which are installed at key positions in each unit. The controller is a PLC programmable logic controller, which is electrically connected to each sensor and actuator. The actuators include frequency converters for each pump body, electric actuators for valves, and metering pumps for scale inhibitor dosing devices.

6. The method for concentrating and recovering nickel sulfate according to claim 5, characterized in that, The scale inhibition protection unit includes a scale inhibitor dosing device (11) and a security filter. The dosing port of the scale inhibitor dosing device (11) is connected to the pipeline between the outlet of the filter product water tank (10) and the inlet of the security filter. The outlet of the security filter is connected to the input end of the high pressure concentration unit. The scale inhibitor dosing device (11) includes a scale inhibitor storage tank, a metering pump and a mixer (12). The filtration accuracy of the security filter is 5μm and the internal filter element is a pleated filter element.

7. The method for concentrating and recovering nickel sulfate according to claim 6, characterized in that, The high-pressure concentration unit includes a high-pressure pump (13), a high-pressure acid-resistant RO treatment device (14), and an RO concentrate tank (15). The input end of the high-pressure pump (13) is connected to the outlet of the security filter, and the output end is connected to the inlet of the high-pressure acid-resistant RO treatment device (14). The product water outlet of the high-pressure acid-resistant RO treatment device (14) is connected to the recycled water unit, the concentrate outlet is connected to the inlet of the RO concentrate tank (15), and the outlet of the RO concentrate tank (15) is connected to the resource recovery unit. The high-pressure pump (13) adopts frequency conversion control. The resource recovery unit includes resources... The recycling booster pump (16) and the resource recycling pipeline are connected. The input end of the resource recycling booster pump (16) is connected to the outlet of the RO concentrate tank (15), and the output end is connected to the raw material recycling pool of the iron phosphate production workshop through the resource recycling pipeline. The recycled water unit includes a recycled water tank (17) and a recycled water pump (18). The inlet of the recycled water tank (17) is connected to the product water outlet of the high pressure acid resistant RO treatment device (14), and the outlet is connected to the input end of the recycled water pump (18). The output end of the recycled water pump (18) is connected to the recycled water pipeline network of the iron phosphate production workshop.

8. The method for concentrating and recovering nickel sulfate according to claim 7, characterized in that, The sludge treatment unit includes a sludge collection tank (19), a sludge conveying pump (20), and a sludge dewatering device (21). The inlet of the sludge collection tank (19) is connected to the sludge discharge port of the integrated water purifier (3) and the sludge discharge port of the precision membrane filter (9), respectively. The outlet is connected to the input end of the sludge conveying pump (20). The output end of the sludge conveying pump (20) is connected to the input end of the sludge dewatering device (21). The outlet of the sludge dewatering device (21) is connected to the inlet of the raw liquid buffer tank (1). The sludge dewatering device (21) adopts a plate and frame filter press.

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