Waste water and waste heat comprehensive utilization device and method in positive electrode material production

Abstract

The invention relates to a comprehensive utilization device and method for waste water and waste heat in production of a positive electrode material. The comprehensive utilization device for the waste water and the waste heat in the production of the positive electrode material comprises a main system and an auxiliary system, the main system comprises a grinding machine, a main spray drying tower and a powder recovery device; the auxiliary system comprises a waste water collecting tank, an auxiliary spray drying area, a waste gas mixing cavity, a heat pump unit, a condensate water collecting box and a control unit. The auxiliary spray drying area is located on the top of the interior of the main spray drying tower. The waste water and waste heat comprehensive utilization device in positive electrode material production is provided with an independent sand mill waste water and spray drying waste water special line treatment system, meanwhile, deep integration of a heat pump system and a spray drying process is introduced, and a feedback control system based on mixed waste gas state real-time monitoring is established; and comprehensive utilization of waste water and preheating generated in the production process of the positive electrode material is realized.

Description

Technical Field

[0001] This invention relates to the field of low-temperature waste heat recovery technology for industrial wastewater and waste gas, and particularly to a device and method for comprehensive utilization of wastewater and waste heat in the production of cathode materials. Background Technology

[0002] With the rapid development of the new energy vehicle industry, lithium iron phosphate (LFP), as a mainstream cathode material, has seen its production capacity continuously expand, leading to increasingly prominent resource consumption and environmental impact during the production process. In the wet production process of LFP, sand mills and spray dryers are key production equipment. Their regular cleaning and maintenance generate specific wastewater containing trace amounts of LFP raw material particles, which have recycling value. Traditional treatment methods often employ flocculation and sedimentation processes to incorporate this wastewater into the overall plant's mixed wastewater system. This approach fails to fully consider the wastewater's low solids content, relatively simple composition, and high reusability, resulting in lengthy treatment processes, high costs, and the inability to directly recover valuable components from the wastewater. Furthermore, the spray drying process consumes significant energy, and the large amount of latent heat of condensation contained in the low-temperature, high-humidity exhaust gas emitted is not effectively utilized, leading to energy waste. Under the background of the carbon neutrality strategy, developing resource-based, low-energy-consumption treatment technologies for this specific wastewater is of great significance.

[0003] Currently, the commonly used solutions in existing technologies can be summarized as a "mixed wastewater evaporation and concentration + simple waste heat utilization" model. This solution attempts to collect various wastewaters from lithium iron phosphate production (including reaction mother liquor, washing wastewater, and sand mill wastewater) and then concentrate them using a multi-effect evaporator. Regarding waste heat utilization, this solution uses the 100-400℃ low-temperature waste heat generated from sintering, drying, and other processes to preheat the mixed wastewater using a conventional heat exchanger before it enters the evaporation system. The concentrated liquid is finally cooled and crystallized to recover some of the solid products.

[0004] However, this scheme has several obvious drawbacks: First, mixing sand mill wastewater with other process wastewater leads to interference between wastewaters of different properties. In particular, the trace amounts of lithium iron phosphate feedstock in the sand mill wastewater are difficult to reuse directly due to dilution and contamination, ultimately forming only low-value mixed salts with limited resource utilization. Second, the scheme's utilization of waste heat is rather crude; there is a lack of effective methods to improve the grade of large amounts of low-temperature waste heat, resulting in its inability to meet the heat requirements of the evaporation process and its subsequent disposal. Finally, the scheme operates with fixed evaporation and crystallization parameters, which cannot adapt to fluctuations in incoming water quality and waste heat supply, leading to poor system stability, unstable product purity, and low overall energy efficiency. These shortcomings limit the practical application of this technology in lithium iron phosphate production. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a device and method for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials described in this invention has an independent dedicated treatment system for wastewater from sand mills and spray drying. At the same time, it introduces a heat pump system and deeply integrates it with the spray drying process, and establishes a feedback control system based on real-time monitoring of the mixed waste gas state, thereby realizing the comprehensive utilization of wastewater and preheating generated during the production of cathode materials.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The device includes a main system and an auxiliary system. Along the wastewater flow direction, the main system includes a grinding mill, a main spray drying tower, and a powder recovery device connected in sequence. Along the wastewater flow direction, the auxiliary system includes a wastewater collection tank, an auxiliary spray drying zone, a waste gas mixing chamber, a heat pump unit, a condensate collection tank, and a control unit connected in sequence. The auxiliary spray drying zone is located at the top inside the main spray drying tower.

[0008] Compared with the prior art, the main technical features of this invention are reflected in the following three aspects:

[0009] First, existing technologies treat sand mill wastewater by mixing it with other process wastewater, while this invention establishes an independent dedicated treatment system for sand mill wastewater and spray drying wastewater. This technology, through specialized collection pipelines, independent spray drying units, and dedicated powder recovery devices, ensures that sand mill and spray drying wastewater are treated independently from generation to reuse. The improvement lies in preventing interference between wastewaters of different properties at the source, ensuring the chemical composition and physical stability of the recovered powder, and enabling the lithium iron phosphate raw material in the wastewater to be directly reused in the batching process in high-purity dry powder form, significantly enhancing the resource recovery value.

[0010] Secondly, existing technologies only utilize medium-to-high temperature waste heat for simple preheating using conventional heat exchangers, while this invention introduces a deep integration of a heat pump system with the spray drying process. This technical feature involves mixing the steam generated from the drying of wastewater from the sand mill with the waste gas from normal material drying, using a heat pump to extract and upgrade the low-temperature heat energy, which is then used to preheat the main intake air for spray drying. The improvement effectively resolves the mismatch between low-grade waste heat and the high-heat requirements of the process, converting the previously unusable 80-120℃ low-temperature waste gas heat energy into high-grade heat energy suitable for drying. This significantly reduces external energy consumption in the spray drying process and achieves tiered and efficient utilization of energy within the process.

[0011] Third, existing technologies operate with fixed parameters, while this invention establishes a feedback control system based on real-time monitoring of the mixed waste gas state. This feature continuously monitors the temperature and humidity of the mixed waste gas, calculates its enthalpy, and dynamically adjusts the wastewater feed flow rate to ensure the heat pump system always operates within its high-efficiency range. The improvement significantly enhances the system's adaptability to upstream operating condition fluctuations, overcomes the energy efficiency decline caused by changes in wastewater feed or main system load fluctuations, ensures the continuous stability of resource recovery and energy-saving effects, and achieves simultaneous optimization of treatment efficiency and energy efficiency.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0013] In some embodiments, the inlet of the wastewater collection tank is connected via pipelines to the outlet of the grinding mill and the outlet of the main spray drying tower, respectively.

[0014] In some embodiments, an atomizer is provided in the auxiliary spray drying zone, and the atomizer is a high-pressure atomizer.

[0015] In some embodiments, the feed line of the atomizer is equipped with a flow meter and a regulating valve for precise control of the wastewater feed rate.

[0016] In some embodiments, the air outlets of the auxiliary spray drying zone and the main spray drying zone are both connected to the inlet of the exhaust gas mixing chamber via insulated pipes.

[0017] In some embodiments, a baffle plate and / or a static mixer are provided inside the exhaust gas mixing chamber.

[0018] This invention optimizes mixing efficiency from a fluid dynamics perspective by setting a guide plate and / or a static mixer in the waste gas mixing chamber to change the flow direction and generate vortices. Ultimately, it forms a mixed waste gas with relatively stable temperature and humidity parameters, with the temperature stable at 65-75℃ and the relative humidity stable at 40-50%. (This uniform mixing is crucial for the stable and efficient operation of the downstream heat pump system. It provides the heat pump evaporator with a heat source with relatively small fluctuations in thermodynamic properties, avoiding the decrease in system efficiency and frequent start-ups and shutdowns of equipment caused by drastic fluctuations in heat source temperature or flow rate.)

[0019] In some embodiments, a temperature sensor and a humidity sensor are installed on the pipe at the outlet of the exhaust gas mixing chamber.

[0020] In some embodiments, the heat pump unit includes an evaporator.

[0021] The evaporator is a key heat exchange device in a heat pump system that absorbs heat from a low-temperature heat source. The low-temperature refrigerant liquid evaporates into a gas here, absorbing heat (evaporation heat absorption).

[0022] In some embodiments, the evaporator is a shell-and-tube structure.

[0023] In some embodiments, the outlet of the exhaust gas mixing chamber is connected to the inlet of the shell side of the evaporator via an induced draft fan.

[0024] In some embodiments, the outlet of the evaporator shell side is connected to the inlet of the condensate collection tank.

[0025] In some embodiments, the outlet of the condensate collection tank is connected to the inlet of the sander via a reuse pipeline.

[0026] In some embodiments, a water quality monitor is installed on the reuse pipeline.

[0027] The water quality monitor in this invention is typically an industrial-grade conductivity meter, which can be expanded to include a pH meter. This instrument continuously monitors the purity of the condensate, and its measurement signal is transmitted to the control unit in real time.

[0028] In some embodiments, the outlet of the evaporator tube side is connected to the inlet of the scroll compressor.

[0029] In some embodiments, the outlet of the scroll compressor is connected to the condenser.

[0030] In some embodiments, the condenser is a shell-and-tube structure, with the refrigerant flowing through the tube side and the preheating medium flowing through the shell side.

[0031] In some embodiments, the preheating medium includes ambient air.

[0032] In some embodiments, the outlet of the condenser shell side is connected to the inlet of the preheater.

[0033] In some embodiments, the outlet of the preheater is connected to the inlet of the drying spray tower.

[0034] In some embodiments, the control unit includes an electrically connected data monitoring mechanism and an actuator.

[0035] In some embodiments, the data monitoring mechanism includes a temperature sensor, a humidity sensor, and a level gauge.

[0036] In some embodiments, the discharge port of the main spray drying tower and the discharge port of the auxiliary spray drying zone are connected to a powder recovery device via an ejector.

[0037] In this invention, the power source of the ejector comes from the significant negative pressure (typically -500Pa to -1500Pa) generated by the high-speed airflow at the inlet of the cyclone separator in the main drying zone.

[0038] In some embodiments, the ejector has a venturi tube structure.

[0039] In some embodiments, the wastewater collection tank includes an anchor agitator and a level gauge, wherein the anchor agitator rotates at a speed of 30 rpm to 60 rpm; and the wastewater collection tank is made of polypropylene.

[0040] The present invention selects an anchor-type agitator that can continuously and gently stir, effectively preventing high-density solid particles from depositing and clumping at the bottom of the tank, while avoiding secondary breakage of particles due to excessive shear force, ensuring uniform and stable wastewater composition, and providing a foundation for subsequent stable and continuous spray drying feed.

[0041] In some embodiments, the reuse piping is made of UPVC or stainless steel.

[0042] In some embodiments, the grinding mill and the spray drying tower are respectively connected to the wastewater collection tank via pipelines made of UPVC material.

[0043] In some embodiments, the high-pressure atomizer includes a nozzle made of tungsten carbide to provide excellent wear resistance. In some embodiments, the high-pressure atomizer maintains a pressure of 1.5 MPa to 3.0 MPa, for example, 1.5 MPa, 1.8 MPa, 2.0 MPa, 2.2 MPa, 2.5 MPa, 2.8 MPa, or 3.0 MPa, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0044] Under this pressure, the wastewater is forced through the tiny orifices of the nozzle and broken into a cluster of cone-shaped atomized droplets with particle sizes mainly between 60μm and 120μm.

[0045] In some embodiments, the evaporation temperature of the refrigerant is 5°C-10°C, for example, it can be 5°C, 6°C, 8°C or 10°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] In some embodiments, the refrigerant is made of environmentally friendly R134a.

[0047] In some embodiments, the heat pump unit is a compression heat pump with variable frequency drive function.

[0048] The heat pump unit is a compression type and is driven by frequency conversion.

[0049] In a second aspect, the present invention provides a method for the comprehensive utilization of wastewater and waste heat in the production of cathode materials as described in the first aspect, wherein the method is carried out in the wastewater and waste heat comprehensive utilization device for the production of cathode materials as described in the first aspect; the cathode material includes any one of lithium iron phosphate, lithium manganese iron phosphate, or polyanionic cathode materials.

[0050] In some embodiments, the method includes the following steps:

[0051] S1: Wastewater collection: The wastewater from the grinding mill and the wastewater from the positive electrode material in the main spray drying tower are transported to the wastewater collection tank, stirred and homogenized to obtain mixed wastewater. When the level gauge in the wastewater collection tank reaches the set high value, a signal is sent to the control unit to start the subsequent steps.

[0052] S2: Spray drying: The mixed wastewater obtained in step S1 is transported to the auxiliary spray drying zone at the top of the main spray drying tower. The mixed wastewater is atomized into droplet groups by the atomizer in the auxiliary spray drying zone. After drying, the recovered powder and water vapor are obtained.

[0053] S3: Waste gas mixing: The water vapor obtained in step S2 and the water vapor generated in the main spray drying tower enter the waste gas mixing chamber to form mixed waste gas;

[0054] S4: Heat Extraction and Enhancement: The mixed waste gas obtained in step S3 is transported to the shell side of the shell-and-tube evaporator by an induced draft fan. The refrigerant flows in the tube side and, after heat exchange, the mixed waste gas releases latent heat and condenses into the first evaporation wastewater. The refrigerant absorbs latent heat and becomes a gaseous working fluid. The gaseous working fluid enters the scroll compressor, which converts it into a high-temperature, high-pressure gas. The high-temperature, high-pressure gas is transported to the shell side of the shell-and-tube condenser to heat the preheating medium in the tube side. The high-temperature, high-pressure gas becomes a low-temperature liquid, and the low-temperature liquid returns to the tube side of the evaporator for the next cycle of heat exchange.

[0055] S5: Heat recovery: The preheated medium obtained in step S4 is fed into the spray drying tower by the main induced draft fan to realize heat recovery;

[0056] S6: Dry powder recycling: The recycled powder obtained in step S2 is conveyed into the powder recycling device through an ejector with a venturi tube structure.

[0057] S7: Condensate Reuse: The first evaporation wastewater obtained in step S4 is injected into the grinding mill through a corrosion-resistant vertical centrifugal pump to achieve condensate reuse.

[0058] This invention constructs a comprehensive resource and energy recovery and utilization device for wastewater from sand mills, spray drying, cleaning, and maintenance processes during the production of cathode materials. The wastewater is collected and then fed into a modified spray drying system for treatment.

[0059] During the drying process, wastewater is converted into solid dry powder and water vapor. A crucial step involves mixing this water vapor with the high-humidity exhaust gas generated from the normal drying of materials in the same drying tower, forming a stable medium-to-low temperature mixed gas source. This mixed exhaust gas is then guided to a heat pump system as its low-temperature heat source; the heat pump system consumes some electrical energy to upgrade the low-grade heat energy in the exhaust gas to high-grade heat energy, which is then used to preheat the main intake air entering the spray drying tower, thereby directly reducing the energy consumption of the main drying process.

[0060] The entire system is dynamically regulated by a control unit to ensure that all components work together in optimal condition. Ultimately, the dried solid powder is reused as a production ingredient, while the clean water generated from the condensation of waste gas is also collected and reused, achieving maximum recycling of materials, energy, and water resources.

[0061] In some embodiments, step S1 involves using a dedicated UPVC pipeline network located at the sand mill and the spray drying drainage point to transport wastewater containing trace amounts of lithium iron phosphate particles (solid content typically between 0.5% and 3%) generated during the cleaning and maintenance process to a 5m³ volumetric water tank via gravity or low pressure. 3 The wastewater is collected in a polypropylene collection tank. This tank is equipped with a low-speed anchor agitator, with the stirring speed controlled between 30 rpm and 60 rpm. This continuous and gentle stirring effectively prevents high-density solid particles from settling and clumping at the bottom of the tank, while also avoiding secondary particle breakage due to excessive shear force. This ensures the wastewater composition is uniform and stable, providing a foundation for subsequent stable and continuous spray drying feed. Furthermore, the collection tank is equipped with a level gauge; when the level reaches a set high value, it sends a signal to the control system, triggering the start of subsequent processes.

[0062] In some embodiments, the droplet group described in step S2 has a particle size of 60μm-120μm, for example, it can be 60μm, 70μm, 80μm, 90μm, 100μm, 110μm or 120μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] In this invention, the droplet size of the droplet group described in S2 is further controlled to be 60μm-120μm. If the particle size is too large, the droplets will not be completely dried within the limited residence time in the tower, resulting in wet powder sticking to the walls. If the particle size is too small, the particles will lack momentum and be easily entrained by the airflow, increasing the load on the downstream powder recovery system. The optimized particle size ensures that the droplets have a large specific surface area, so that after falling into the tower, they can undergo extremely rapid heat and mass exchange with the high-temperature airflow, and the moisture evaporates in a very short time, leaving dry, free-flowing solid particles.

[0064] In some embodiments, the wastewater collected and homogenized in step S2 is pumped by a corrosion-resistant centrifugal pump through stainless steel pipes to an auxiliary system at the top of the spray drying tower. This auxiliary system, independent of the main system for normal material drying, is equipped with a high-pressure atomizer. Its core component is a tungsten carbide nozzle for excellent wear resistance. The atomizer is maintained at an operating pressure of 1.5-3.0 MPa by a high-pressure plunger pump. Under this pressure, the wastewater is forced through the tiny orifices of the nozzle, breaking it into a cluster of cone-shaped atomized droplets with a particle size primarily between 60 and 120 μm. (Excessively large particle size prevents complete drying within the limited residence time in the tower, resulting in wet powder adhering to the walls; excessively small particle size leads to insufficient particle momentum, making them prone to excessive entrainment by the airflow, increasing the load on the downstream powder recovery system. Optimized particle size ensures that the droplets have a large specific surface area, allowing for extremely rapid heat and mass exchange with the high-temperature airflow after falling into the tower, resulting in rapid evaporation of moisture and leaving dry, free-flowing solid particles.) The atomizer's feed line is equipped with a flow meter and a regulating valve to precisely control the wastewater feed rate.

[0065] In some embodiments, the water vapor generated during wastewater drying in step S3, together with a large amount of high-humidity waste gas (typically 100-120°C and 15-25% relative humidity) discharged from the main drying zone at the bottom of the tower after drying normal materials, is introduced into a specially designed stainless steel waste gas mixing chamber through an insulated pipe. The volume of this mixing chamber is calculated to provide sufficient residence time (approximately 2-5 seconds) to allow the two gas streams to mix thoroughly. Inside, a guide vane or static mixer can be installed to optimize mixing efficiency from a fluid dynamics perspective by changing the flow direction and generating vortices, ultimately forming a mixed waste gas with relatively stable temperature and humidity parameters, with the temperature stable at 65-75°C and the relative humidity stable at 40-50%. (This uniform mixing is crucial for the stable and efficient operation of the downstream heat pump system, providing a heat source with relatively stable thermodynamic properties for the heat pump evaporator, avoiding system efficiency degradation and frequent equipment start-ups and shutdowns caused by drastic fluctuations in heat source temperature or flow rate.)

[0066] In some embodiments, the dew point of the mixed exhaust gas in step S4 is 30°C-50°C, for example, it can be 30°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] In some embodiments, the uniformly mixed exhaust gas from step S4 is drawn into the evaporator of the heat pump unit by an induced draft fan. The evaporator typically employs a shell-and-tube structure, with the mixed exhaust gas flowing through the shell side and the refrigerant flowing through the tube side. Here, the exhaust gas transfers its low-temperature heat energy to the environmentally friendly R134a refrigerant circulating within the tubes. The refrigerant absorbs heat at a relatively low evaporation pressure (corresponding to an evaporation temperature of approximately 5-10°C) and evaporates into a low-temperature, low-pressure gas. This process cools the mixed exhaust gas to below its dew point temperature (approximately 30-50°C), where some water vapor condenses and releases latent heat of phase change. This latent heat is also effectively absorbed by the refrigerant, significantly increasing the total heat absorption. Subsequently, the gaseous refrigerant enters a variable-frequency scroll compressor, where it is adiabatically compressed to a higher pressure and temperature (corresponding to a condensation temperature of approximately 80-120°C, higher than the preheating medium outlet temperature, ensuring effective heat transfer), converting electrical energy into the thermodynamic energy of the refrigerant. The high-temperature and high-pressure working fluid then flows into another shell-and-tube condenser. In the tube side of the condenser, the working fluid releases heat to the preheated medium (ambient air) flowing in the shell side and condenses itself into a low-temperature liquid. The high-grade latent heat of condensation released in this process is the core heat energy that the system recovers and improves.

[0068] In some embodiments, the preheating medium in step S5, during its introduction into the spray drying tower, also includes heat provided by an auxiliary heat source. The high-grade heat energy released by the condenser in S5 is specifically used to heat the ambient air passing through the intake preheater. Specifically, the ambient air flows through the shell side of the condenser at a certain mass flow rate under the action of the main induced draft fan of the spray drying system. As the air flows through the condenser, it absorbs the condensation heat released from the working fluid in the condenser tubes, significantly raising its temperature from ambient temperature to a higher temperature (70-90°C). This preheated air is then mixed with supplemental heat provided by any available auxiliary heat source (such as a natural gas direct-fired or electric heater) to reach the final drying temperature (200-350°C), and then enters the spray drying tower as the main intake air. Preheating directly reduces the external energy input required by the auxiliary heat source to heat the air from ambient temperature to the target drying temperature, effectively reducing gas consumption or electricity consumption and achieving significant energy savings.

[0069] In some embodiments, the dried cathode material obtained from the main spray drying tower is also recovered in step S6 of the powder recovery device.

[0070] In some embodiments, in step S6, the solid dry powder produced by wastewater drying in the spray drying tower, with a composition consistent with the main raw material of lithium iron phosphate and a particle size typically between 10-30 μm, is collected by a cleverly designed pneumatic ejector recovery system. This system is connected to a Venturi tube ejector at the powder settling outlet below the auxiliary drying zone. The ejector is powered by the significant negative pressure (typically -500 Pa to -1500 Pa) generated by the high-speed airflow at the inlet of the cyclone separator in the main drying zone.

[0071] The negative pressure is transmitted to the ejector's inlet via a connecting pipe. When the main system is running, a high-speed, low-pressure zone is generated at the ejector throat, creating a powerful suction force that continuously and stably draws in the dry powder produced by the auxiliary system. This powder mixes with the main ejector airflow and then enters the main product airflow duct. This allows for instantaneous and uniform online mixing of the auxiliary system's dry powder with the main product powder obtained from normal material drying within the duct, which is then collected by the subsequent cyclone separator and bag filter. This design eliminates the need for a separate powder conveying fan, rotary valve, conveying pipes, and mechanical mixing equipment, greatly simplifying the process, reducing equipment investment and maintenance costs, and fundamentally avoiding the problems of moisture absorption, contamination, or cross-contamination that may occur during intermediate storage. It also enables the immediate, seamless, and high-quality reuse of byproducts.

[0072] In some embodiments, in step S7, within the heat pump evaporator, the mixed exhaust gas is cooled to below its dew point temperature (typically 50-60°C), where the large amount of water vapor it contains condenses into liquid water. This condensate is collected through a condensate drain at the bottom of the evaporator, via a U-shaped water seal, and then through a pipe to a 2m... 3 The intermediate water tank is made of stainless steel. Because it originates from the phase change condensation of water vapor, and during this process, some soluble impurities remain in the gas phase or are discharged with the uncondensed gas, the water quality of the condensate is usually much better than that of the original wastewater. Its conductivity can be stably maintained below 50 μS / cm, and its pH value is close to neutral.

[0073] Subsequently, the condensate is pumped by a corrosion-resistant, lightweight vertical centrifugal pump into the pure water supply network of the pre-grinding batching process, serving as the pure water required for preparing the grinding slurry. This transforms the wastewater treatment process into a new, high-quality water source, achieving a cascaded recycling of water resources within the plant. The condensate is used for pre-grinding batching, where water quality requirements are second only to the reaction synthesis, while the higher-grade pure water is saved for more critical process steps, effectively reducing the consumption of fresh industrial pure water and subsequent wastewater discharge.

[0074] The core of this system is a specially designed spray drying tower. Internally, through a rational air distribution system and physical partitions, it clearly divides the airflow into two drying zones: a main zone and an auxiliary zone. The auxiliary drying zone is located at the top of the tower, directly in contact with the high-temperature main intake air, and is equipped with the aforementioned dedicated wastewater pressure atomizer and an independent feed control system. A waste gas mixing chamber made of 304 stainless steel is connected to the exhaust ports of both the main and auxiliary drying zones via insulated pipes. A compression heat pump unit with a rated heat capacity selected according to the system scale is connected to the mixing chamber outlet pipe via its evaporator, and forms a complete heat exchange loop with a shell-and-tube preheater installed on the main intake pipe of the spray drying tower via its condenser.

[0075] Powder recovery utilizes the aforementioned non-powered ejector solution, seamlessly integrated with the cyclone separator inlet of the main product collection system via pipeline. The entire system is centrally scheduled and monitored by a control unit centered on a PLC and touchscreen. This unit collects sensor data from key nodes (such as the temperature and humidity of the mixed exhaust gas, the main inlet air temperature, heat pump operating parameters, and liquid level), and outputs commands to precisely control key actuators (such as the frequency of the wastewater feed pump, the speed of the heat pump compressor, and the damper of the main induced draft fan) based on preset control logic and algorithms, thereby ensuring the coordinated, optimized, and stable automatic operation of the entire complex system.

[0076] In terms of system spatial layout and process design, the auxiliary spray drying zone is deliberately located upstream of the hot air in the main spray drying zone. This means that the high-temperature main intake air (200-350℃) that comes out of the intake preheater and is heated to its final temperature by the auxiliary heat source first enters the auxiliary drying zone from the top of the tower, and comes into full contact with the droplet group formed by the atomization of wastewater.

[0077] In this process, the sensible heat of the high-temperature air is rapidly used for the heating and evaporation of the wastewater, significantly reducing its own temperature (from 200℃ to 100℃), while the absolute humidity increases dramatically due to the incorporation of a large amount of water vapor. This pretreated airflow, with its lower temperature and higher humidity, then flows downwards into the main drying zone to dry the normal material slurry entering from the upper part of the tower. This process arrangement essentially constitutes a tiered utilization of thermal energy according to grade: the highest temperature and grade thermal energy is preferentially used for the high-energy-consuming wastewater evaporation (phase change process), and then the lower temperature and correspondingly lower grade thermal energy is used for the deceleration drying stage of the material. This not only improves the overall thermodynamic efficiency of thermal energy utilization and reduces effective energy loss, but also the milder drying conditions (slightly lower inlet temperature and slightly higher medium humidity) help to slow down the excessively rapid evaporation of moisture from the material surface, thereby improving the physical properties of the final lithium iron phosphate product.

[0078] To ensure the stable and efficient operation of the entire collaborative system, a control unit based on an industrial-grade programmable logic controller (PLC) was deployed. This controller continuously receives 4-20mA current signal readings from high-precision resistive temperature sensors and capacitive humidity sensors installed on the exhaust gas mixing chamber outlet pipe via an analog input module.

[0079] The controller's built-in algorithm calculates the enthalpy H (kJ / kg) of the mixed exhaust gas in real time based on the collected temperature T (°C) and relative humidity φ (%), combined with the local atmospheric pressure. Enthalpy is a state parameter that comprehensively reflects the total heat (the sum of sensible and latent heat) contained in the exhaust gas, and it characterizes its quality as a heat source for the heat pump better than temperature or humidity alone. The controller compares the calculated real-time enthalpy with a preset high-efficiency operating range [H1, H2] (300, 360 kJ / kg), which is determined based on the optimal operating condition curve of the selected heat pump unit.

[0080] If the measured enthalpy H consistently exceeds the upper limit H2, it indicates that the heat source quality is too high but the flow rate may be insufficient. The controller will calculate according to a predetermined proportional-integral algorithm and output an increased 4-20mA control signal to the frequency converter of the wastewater feed pump. By increasing the pump speed, the wastewater feed flow rate is increased, thereby increasing the evaporation load, absorbing more heat, and causing the enthalpy of the mixed waste gas to drop. Conversely, if the measured enthalpy H consistently falls below the lower limit H1, the feed pump frequency is reduced to decrease the evaporation load, causing the waste gas enthalpy to rise. This closed-loop control strategy based on key state parameters forms a stable negative feedback loop that can actively sense and adapt to fluctuations in upstream operating conditions (such as wastewater composition and main system load), keeping the heat source conditions of the heat pump always anchored within its highest performance coefficient range. This ensures the efficiency and robustness of the entire energy recovery process and avoids the lag and uncertainty of manual operation.

[0081] Furthermore, the heat pump unit used is preferably a compression heat pump with variable frequency drive, whose operating goal is to maintain the coefficient of performance (COP) within the high-efficiency range of 2.5 to 4.0. The COP is a key indicator for measuring heat pump performance, defined as the ratio of heating capacity to input power. The control unit calculates the instantaneous COP in real time by monitoring temperature and pressure sensors on the heat pump evaporator and condenser, as well as the compressor's input power. If the calculated COP deviates from this high-efficiency range, the control unit will issue a command to adjust the compressor's operating frequency. For example, when the COP is low, it may be due to a low evaporator-side heat source temperature or a high condenser-side load. In this case, appropriately reducing the compressor speed, refrigerant mass flow rate, and compression ratio allows the system to operate at a new operating point that better matches the current external conditions. Although the absolute heating capacity may decrease slightly, the operating efficiency is improved. This adaptive control strategy ensures that the heat pump unit can flexibly respond to disturbances such as wastewater flow fluctuations and ambient temperature changes, always operating as a highly efficient energy-boosting device, thereby consolidating the foundation of the entire energy recovery chain and maximizing energy-saving benefits.

[0082] Furthermore, the ejector design in the powder recovery unit is key to achieving immediate dry powder reuse. Essentially a passive device, it cleverly utilizes the fluid dynamics (negative pressure) inherent in the main system's operation as its power source, requiring no additional moving parts or energy, resulting in an extremely simple and reliable structure. Its internal flow channels are precisely calculated and manufactured to ensure sufficient suction force to overcome powder flow resistance under set operating conditions, while preventing blockages. Its introduction allows the dry powder generated by the auxiliary system to be directly and continuously incorporated into the high-speed flowing gas-solid two-phase flow of the main product, achieving rapid and uniform dispersion and mixing under turbulent conditions. This achieves "reuse upon generation," completely eliminating the need for intermediate buffer silos, mechanical conveying equipment (such as screw conveyors), and independent mixers. This not only reduces initial investment and equipment maintenance costs but also fundamentally eliminates potential material losses, moisture risks, foreign object contamination, or particle agglomeration due to mechanical action caused by intermediate steps, ensuring the chemical quality and physical homogeneity of the reused material, thus meeting the stringent quality requirements of cathode materials.

[0083] Furthermore, the system includes a complete condensate collection and reliable reuse device. This device features a collection tank controlled by a float valve or level sensor, a corrosion-resistant lightweight vertical centrifugal pump, and UPVC or stainless steel piping leading to the water point in the pre-grinding batching process. An online water quality monitor, typically an industrial-grade conductivity meter, is installed on the reuse pipeline and can be expanded with a pH meter. This instrument continuously monitors the purity of the condensate, and its measurement signal is transmitted to the control unit in real time. If the control system detects an abnormal water quality (e.g., conductivity exceeding the preset safety threshold of 100 μS / cm due to increased ion concentration caused by equipment cleaning or accidental contamination), it immediately outputs a signal to automatically shut off the pneumatic or electric valve on the reuse pipeline and simultaneously open the emergency discharge valve to discharge the substandard water to a designated emergency water tank or sewage system, preventing it from affecting the preparation quality of the cathode material slurry and the electrochemical performance of the final battery product. This automated water quality monitoring and emergency switching safety mechanism provides solid support for the stable, reliable, and risk-free reuse of water resources in production processes, enhancing the robustness of the entire system and user confidence.

[0084] The implementation of this system not only achieves the environmental goals of resource recycling and energy conservation, but also brings significant economic benefits. Based on the calculation of lithium iron phosphate cathode material and the production capacity of 10,000 tons of lithium iron phosphate, the total annual economic benefit is RMB 1.78 million to RMB 2.38 million, which includes water-saving and heat-saving benefits, and has both economic and environmental value.

[0085] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0086] Compared with the prior art, the present invention has at least the following beneficial effects:

[0087] (1) This invention constructs a comprehensive resource and energy recovery and utilization device for wastewater from sand milling and spray drying cleaning and maintenance during the production of cathode materials. The device has an independent dedicated treatment system for sand mill wastewater and spray drying wastewater. At the same time, it introduces a heat pump system and deeply integrates it with the spray drying process and establishes a feedback control system based on real-time monitoring of the mixed waste gas state, realizing the comprehensive utilization of wastewater and preheating generated during the production of cathode materials.

[0088] (2) The method for comprehensive utilization of wastewater and waste heat in the production of cathode materials provided by this invention mixes the water vapor with the high-humidity waste gas generated from the normal drying of materials in the same drying tower to form a stable medium-low temperature mixed gas source. The mixed waste gas is then guided to a heat pump system as its low-temperature heat source; the heat pump system consumes part of the electrical energy to upgrade the low-grade heat energy in the waste gas to high-grade heat energy, and uses it to preheat the main intake air entering the spray drying tower, thereby directly reducing the energy consumption of the main drying process. The entire system is dynamically regulated by a control unit to ensure that each link works in the optimal state. Finally, the solid dry powder obtained from drying is recycled for production batching, and the clean water generated after the waste gas is condensed is also collected and reused, realizing the maximum recycling of materials, energy and water resources. Attached Figure Description

[0089] Figure 1 A schematic diagram of the wastewater and waste heat comprehensive utilization device in the production of positive electrode materials provided in Embodiment 1 of the present invention; wherein: 1-grinding machine; 2-wastewater collection tank; 3-spray drying tower; 4-atomizer; 5-powder recovery device; 6-waste gas mixing chamber; 7-temperature / humidity sensor; 8-induced draft fan; 9-evaporator; 10-condensate collection tank; 11-water quality monitor; 12-scroll compressor; 13-condenser; 14-induced draft fan 2;

[0090] Figure 2 This is a flowchart of the comprehensive utilization of wastewater and waste heat in Embodiment 1 of the present invention;

[0091] Figure 3 This is a flowchart of waste heat recovery and utilization in Embodiment 1 of the present invention. Detailed Implementation

[0092] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0093] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0094] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0095] Example 1

[0096] This embodiment provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. A schematic diagram of the device is shown below. Figure 1 As shown;

[0097] use Figure 1 The apparatus shown illustrates a method for the comprehensive utilization of wastewater and waste heat in the production of lithium iron phosphate cathode materials, comprising the following steps, the specific process of which is as follows: Figure 2 As shown:

[0098] S1: Wastewater Collection: Wastewater containing trace amounts of lithium iron phosphate particles (solid content typically between 0.5% and 3%) generated during the cleaning and maintenance of the sand mill 1 and spray drying tower will be transported by gravity or low pressure to a 5m³ tank. 3 The wastewater is collected in a polypropylene wastewater collection tank 2. This tank is equipped with a low-speed anchor agitator, with the agitation speed controlled between 30 rpm and 60 rpm. This continuous and gentle agitation effectively prevents high-density solid particles from settling and agglomerating at the bottom of the tank, while also avoiding secondary particle breakage due to excessive shear force. This ensures the wastewater composition is uniform and stable, providing a foundation for subsequent stable and continuous spray drying feed. Furthermore, the collection tank is equipped with a level gauge; when the level reaches a set high value, it sends a signal to the control system, triggering the start of subsequent processes.

[0099] S2: Spray drying: The mixed wastewater obtained in S1 is transported to the auxiliary spray drying zone at the top of the main spray drying tower. The mixed wastewater passes through the atomizer in the auxiliary spray drying zone. The atomizer 4 is maintained at an operating pressure of 1.5-3.0MPa by a high-pressure plunger pump and atomized into a group of droplets with a particle size of 80μm-100μm. After drying, the recovered powder and water vapor are obtained.

[0100] S3: Waste gas mixing: The water vapor obtained in S2 and the water vapor generated in the main spray drying tower enter the waste gas mixing chamber 6 to form mixed waste gas;

[0101] S4: Heat Extraction and Enhancement: The mixed waste gas obtained in S3 is detected by temperature and humidity sensor 7 and transported to the shell side of shell-and-tube evaporator 9 by induced draft fan 8. The refrigerant flows in the tube side and undergoes heat exchange. The mixed waste gas releases latent heat and condenses into the first evaporation wastewater, which is collected by condensate collection tank 10. The refrigerant absorbs latent heat and becomes a gaseous working fluid. The gaseous working fluid enters scroll compressor 12, which converts the gaseous working fluid into a high-temperature and high-pressure gas. The high-temperature and high-pressure gas is transported to the shell side of shell-and-tube condenser 13 to heat the preheating medium in the tube side. The high-temperature and high-pressure gas becomes a low-temperature liquid and is transported to the tube side of 9 for the next cycle of heat exchange.

[0102] S5: Heat recovery: The preheated medium obtained in S4 is fed into the spray drying tower 3 by the main induced draft fan 14, and the heat provided by the auxiliary heat source is added to realize heat recovery;

[0103] S6: Dry powder recycling: The recovered powder obtained in S2 is conveyed to the powder recycling device 5 through an ejector with a venturi tube structure.

[0104] S7: Condensate Reuse: After the first evaporation wastewater obtained from S4 passes the water quality monitoring instrument 11 test, it is injected into the grinding mill through a corrosion-resistant vertical centrifugal pump to achieve condensate reuse.

[0105] The flowchart for waste heat recovery and utilization is as follows: Figure 3 As shown in the figure, the heat pump system recovers waste heat from low-temperature exhaust gas through a compression thermodynamic cycle and upgrades it into high-grade heat energy that can be used in the drying process. This intuitively demonstrates the core energy recovery and upgrading process of "low-temperature heat source input - compression and upgrading - heat energy reuse".

[0106] Example 2

[0107] This embodiment provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The device is the same as that in Embodiment 1, except that it is used to recover lithium manganese iron phosphate cathode materials. The specific process remains unchanged.

[0108] Example 3

[0109] This embodiment provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The device is the same as that in Embodiment 1, except that it is used to recover polyanion-type sodium-ion battery cathode materials. The specific process remains unchanged.

[0110] Example 4

[0111] This embodiment provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The only difference from Embodiment 1 is that in the method for the comprehensive utilization of wastewater and waste heat in the production of cathode materials, the pressure of the S2 atomizer is 5MPa, while the other steps remain unchanged.

[0112] Example 5

[0113] This embodiment provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The only difference from Embodiment 1 is that in the method for the comprehensive utilization of wastewater and waste heat in the production of cathode materials, S4 does not involve electric heating, while the other steps remain unchanged.

[0114] Comparative Example 1

[0115] This comparative example provides a device for the comprehensive utilization of wastewater and waste heat in the production of cathode materials. The only difference from Example 1 is that this device does not contain a control unit.

[0116] test:

[0117] The wastewater and waste heat utilization devices prepared in the positive electrode material production of the examples and comparative examples were used to comprehensively utilize wastewater and waste heat, and the results are shown in Table 1 below.

[0118] Table 1

[0119]

[0120] The test results show that:

[0121] (1) As can be seen from Examples 1-3, this invention constructs a comprehensive resource and energy recovery and utilization device for wastewater from sand mills and spray drying cleaning and maintenance during the production of cathode materials. This water vapor is mixed with the high-humidity waste gas generated during normal material drying in the same drying tower to form a stable medium-low temperature mixed gas source. This mixed waste gas is then guided to a heat pump system as its low-temperature heat source; the heat pump system consumes some electrical energy to upgrade the low-grade heat energy in the waste gas to high-grade heat energy, which is then used to preheat the main intake air entering the spray drying tower, thereby directly reducing the energy consumption of the main drying process. The entire system is dynamically regulated by a control unit to ensure that each link works in optimal condition. Finally, the dried solid powder obtained is reused for production batching, and the clean water generated after condensation of the waste gas is also collected and reused, achieving maximum recycling of materials, energy, and water resources.

[0122] (2) A comparison of Examples 1 and 4 shows that the present invention maintains a pressure of 1.5MPa-3.0MPa using a further high-pressure atomizer. Under this pressure, wastewater is forced through the tiny orifices of the nozzle, breaking into a group of cone-shaped atomized droplets with particle sizes mainly concentrated between 60μm and 120μm. Excessive pressure results in excessively fine droplet size (<60μm), insufficient momentum, and easy entrainment by the airflow into the subsequent waste gas treatment system, causing powder loss. Fine particles easily form a "mist" suspension in the tower, and some are carried out before being completely dried, increasing the load on the downstream bag filter and even causing blockage.

[0123] (3) By comparing Example 1 and Example 5, it can be seen that by further controlling the process conditions of the compressor in S4 to electrically heat the gaseous working medium and compress and raise the temperature, the present invention can achieve better technical effects such as improving the quality of low-temperature waste heat, efficient recovery of waste heat, reducing the energy consumption of spray drying and stable reuse of condensate. When S4 does not perform electrical heating and compression and raise the temperature, it will be impossible to improve the quality of heat source, the waste heat recovery efficiency of waste gas will be low, the amount of water vapor condensation will be small, and the reuse of condensate and the energy-saving effect of the system will be significantly reduced.

[0124] (4) As can be seen from Example 1 and Comparative Example 1, when no control system is used, all key indicators fluctuate significantly and the average value decreases: During continuous operation testing, due to the normal fluctuations in the solid content of the wastewater (0.5%) and the load of the main tower, the system has no adaptive adjustment capability. When the enthalpy of the exhaust gas is too high, the heat pump evaporation temperature rises, the compressor power consumption increases, but the heating efficiency (COP) decreases, resulting in unstable energy-saving effect. When the enthalpy of the exhaust gas is too low, the heat source is insufficient, the system heating capacity decreases, and in order to maintain the drying temperature, the auxiliary heat source needs to be frequently replenished, increasing energy consumption. The wastewater feed flow rate is fixed, and under the fluctuation of the heat source, the drying effect is sometimes good and sometimes bad, resulting in fluctuations in the recovery rate and powder moisture content. Therefore, dynamic control based on real-time enthalpy feedback is not an optional automation upgrade, but the key to ensuring the continuous, efficient, and stable operation of the entire complex coupled system, and a necessary means to achieve the claimed technical effects (high efficiency, high recovery rate).

[0125] In summary, this invention constructs a comprehensive resource and energy recovery and utilization device for wastewater from sand mills and spray drying cleaning and maintenance processes during cathode material production. This device features independent dedicated treatment systems for sand mill wastewater and spray drying wastewater, while also deeply integrating a heat pump system with the spray drying process and establishing a feedback control system based on real-time monitoring of the mixed waste gas state. This achieves comprehensive utilization of wastewater and preheating generated during cathode material production. The provided method for comprehensive utilization of wastewater and waste heat in cathode material production mixes water vapor with high-humidity waste gas generated from normal material drying in the same drying tower, forming a stable medium-low temperature mixed gas source. This mixed waste gas is then guided to a heat pump system as its low-temperature heat source. The heat pump system, by consuming some electrical energy, upgrades the low-grade heat energy in the waste gas to high-grade heat energy, which is then used to preheat the main intake air entering the spray drying tower, thereby directly reducing the energy consumption of the main drying process. The entire system is dynamically regulated by a control unit to ensure that each link works in an optimal state. Ultimately, the solid powder obtained from drying is reused in production ingredients, while the clean water generated after condensing the waste gas is also collected and reused, achieving maximum recycling of materials, energy, and water resources.

[0126] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A device for comprehensive utilization of wastewater and waste heat in the production of cathode materials, characterized in that, The wastewater and waste heat comprehensive utilization device in the production of cathode materials includes a main system and an auxiliary system; Along the direction of wastewater flow, the main system includes a grinding mill, a main spray drying tower, and a powder recovery device connected in sequence; Along the direction of wastewater flow, the auxiliary system includes a wastewater collection tank, an auxiliary spray drying zone, an exhaust gas mixing chamber, a heat pump unit, a condensate collection tank, and a control unit connected in sequence. The auxiliary spray drying zone is located at the top inside the main spray drying tower.

2. The wastewater and waste heat comprehensive utilization device in the production of positive electrode materials according to claim 1, characterized in that, The inlet of the wastewater collection tank is connected to the outlet of the grinding machine and the outlet of the main spray drying tower via pipelines. And / or, an atomizer is provided in the auxiliary spray drying zone; And / or, the feed line of the atomizer is equipped with a flow meter and a regulating valve; And / or, the air outlets of the auxiliary spray drying zone and the main spray drying zone are both connected to the inlet of the exhaust gas mixing chamber through insulated pipes; And / or, a guide vane and / or a static mixer are provided in the exhaust gas mixing chamber; And / or, a temperature sensor and a humidity sensor are installed on the pipe at the outlet of the exhaust gas mixing chamber; And / or, the heat pump unit includes an evaporator.

3. The wastewater and waste heat comprehensive utilization device in the production of positive electrode materials according to claim 2, characterized in that, The evaporator has a shell-and-tube structure; And / or, the outlet of the exhaust gas mixing chamber is connected to the inlet of the shell side of the evaporator via an induced draft fan; And / or, the outlet of the evaporator shell side is connected to the inlet of the condensate collection tank; And / or, the outlet of the condensate collection tank is connected to the inlet of the grinding machine via a reuse pipeline; And / or, a water quality monitoring instrument is installed on the reuse pipeline; And / or, the outlet of the evaporator tube side is connected to the inlet of the scroll compressor; And / or, the outlet of the scroll compressor is connected to the condenser.

4. The wastewater and waste heat comprehensive utilization device in the production of positive electrode materials according to claim 3, characterized in that, The condenser has a shell-and-tube structure, with the refrigerant flowing through the tube side and the preheating medium flowing through the shell side. And / or, the preheating medium includes ambient air; And / or, the outlet of the condenser shell side is connected to the inlet of the preheater; And / or, the outlet of the preheater is connected to the inlet of the drying spray tower.

5. The wastewater and waste heat comprehensive utilization device in the production of positive electrode materials according to claim 1, characterized in that, The control unit includes an electrically connected data monitoring mechanism and an execution mechanism; the data monitoring mechanism includes a temperature sensor, a humidity sensor, and a level gauge; And / or, the discharge port of the main spray drying tower and the discharge port of the auxiliary spray drying zone are connected to the powder recovery device through an ejector; the ejector has a Venturi tube structure.

6. The wastewater and waste heat comprehensive utilization device in the production of positive electrode materials according to claim 1, characterized in that, The wastewater collection tank includes an anchor-type agitator and a level gauge; And / or, the grinding mill and spray drying tower are respectively connected to the wastewater collection tank via pipelines.

7. The wastewater and waste heat comprehensive utilization device in the production of positive electrode materials according to claim 4, characterized in that, The evaporation temperature of the refrigerant is 5℃-10℃; And / or, the refrigerant is made of environmentally friendly R134a; And / or, the heat pump unit is a compression heat pump with variable frequency drive function.

8. A method for comprehensive utilization of wastewater and waste heat in the production of cathode materials, characterized in that, The method is carried out in the wastewater and waste heat comprehensive utilization device in the production of cathode materials according to any one of claims 1-7; The cathode material includes any one of lithium iron phosphate, lithium manganese iron phosphate, or polyanionic cathode materials.

9. The method according to claim 8, characterized in that, The method includes the following steps: S1: Wastewater collection: The wastewater from the grinding mill and the wastewater from the positive electrode material in the main spray drying tower are transported to the wastewater collection tank, stirred and homogenized to obtain mixed wastewater. When the level gauge in the wastewater collection tank reaches the set high value, the level gauge sends a signal to the control unit to start the subsequent steps. S2: Spray drying: The mixed wastewater obtained in step S1 is transported to the auxiliary spray drying zone at the top of the main spray drying tower. The mixed wastewater is atomized into droplet groups by the atomizer in the auxiliary spray drying zone. After drying, the recovered powder and water vapor are obtained. S3: Waste gas mixing: The water vapor obtained in step S2 and the water vapor generated in the main spray drying tower enter the waste gas mixing chamber to form mixed waste gas; S4: Heat Extraction and Enhancement: The mixed waste gas obtained in step S3 is transported to the shell side of the shell-and-tube evaporator by an induced draft fan. The refrigerant flows in the tube side and undergoes heat exchange. The mixed waste gas releases latent heat and condenses into the first evaporation wastewater. The refrigerant absorbs latent heat and becomes a gaseous working fluid. The gaseous working fluid enters the scroll compressor and is converted into a high-temperature and high-pressure gas. The high-temperature and high-pressure gas is transported to the shell side of the shell-and-tube condenser and exchanges heat with the air passing through the tube side. The heated air is then passed into the spray drying tower by the main induced draft fan. The high-temperature and high-pressure gas is condensed into a low-temperature liquid and returned to the tube side of the evaporator for the next cycle of heat exchange. S5: Heat recovery: The preheated medium obtained in step S4 is fed into the spray drying tower by the main induced draft fan to realize heat recovery; S6: Dry powder recycling: The recycled powder obtained in step S2 is conveyed into the powder recycling device through an ejector with a venturi tube structure. S7: Condensate Reuse: The first evaporation wastewater obtained in step S4 is injected into the grinding mill through a corrosion-resistant vertical centrifugal pump to achieve condensate reuse.

10. The method according to claim 9, characterized in that, The droplet group described in step S2 has a particle size of 60 μm-120 μm; And / or, the dew point of the mixed exhaust gas in step S4 is 30℃-50℃; And / or, during the process of the preheating medium being introduced into the spray drying tower in step S5, heat is also provided by an auxiliary heat source; And / or, in step S6, the powder recovery device also recovers the dried cathode material obtained from the main spray drying tower.

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