Environment-friendly preparation device and process for battery-grade iron phosphate

Abstract

The invention discloses a green and environment-friendly preparation device and process for battery grade iron phosphate, the green and environment-friendly preparation device comprises a reaction system, a separation and purification system and a drying and forming system, the reaction system comprises a plurality of reaction kettles, and the reaction kettles are arranged in a multi-stage series connection mode; the reaction system, the separation and purification system and the drying and forming system are arranged, the reaction kettles connected in series are adopted for reaction, complete reaction is guaranteed, the microwave heating assembly and the dispersion module are arranged in the reaction kettles, and real-time accurate regulation and control of temperature, pressure and pH value are achieved; the reaction time is shortened by 50%, the particle size controllability is remarkably improved, purified gas of a gas circulation module is recycled to a reaction system, the membrane separation-electrodialysis-evaporative crystallization process is integrated, full-process resource utilization is achieved, meanwhile, cooperative utilization of waste battery black powder and industrial solid waste is achieved, and a closed-loop industrial chain is constructed.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy material preparation, and in particular to a green and environmentally friendly preparation device and process for battery-grade iron phosphate. Background Art

[0002] As the core raw material for lithium iron phosphate (LiFePO4) batteries, the purity, particle size distribution, and morphology of iron phosphate (FePO4) directly impact battery performance. Traditional preparation methods (such as high-temperature solid-phase methods and co-precipitation) suffer from high energy consumption, difficult wastewater treatment, and residual metal impurities, making them difficult to meet the material consistency and environmental requirements of power batteries. Therefore, the development of low-energy, zero-emission FePO4 preparation technology has become a key industry need.

[0003] To this end, a green and environmentally friendly preparation device and process for battery-grade iron phosphate are proposed. Summary of the Invention

[0004] The object of the present invention is to provide a green and environmentally friendly preparation device and process for battery-grade iron phosphate to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a green and environmentally friendly preparation device for battery-grade iron phosphate, comprising a reaction system, a separation and purification system, and a drying and molding system, wherein the reaction system comprises a reactor, wherein the number of the reactors is multiple and the reactors are arranged in multi-stage series, and a dispersion module and a heating assembly are provided inside the reactor;

[0006] The separation and purification system includes a centrifugal-membrane filtration coupling device and an electrolytic purification unit;

[0007] The drying and molding system includes a vacuum low-temperature drying chamber and an airflow crushing and classifying machine;

[0008] The dispersion module includes an array ultrasonic probe arranged at the bottom of the reactor, and the heating component includes microwave transmitters arranged around the reactor.

[0009] According to the above technical solution, sensors are provided inside the reactor, and the sensors include a pH electrode, a pressure sensor and a liquid level gauge.

[0010] According to the above technical solution, the reaction system also includes a gas circulation module, which includes a condensation recovery unit arranged at the top of the reactor, the condensation recovery unit is connected to an adsorption purification unit, the adsorption purification unit is connected to a gas recycling unit, and the gas recycling unit is connected to the bottom of the reactor.

[0011] According to the above technical solution, the centrifuge-membrane filtration coupling device consists of a high-speed centrifuge and a nanofiltration membrane assembly.

[0012] According to the above technical solution, the electrolytic purification unit is composed of a bipolar membrane electrodialysis cell.

[0013] According to the above technical solution, environmental protection and resource utilization equipment is also included, and the environmental protection and resource utilization equipment includes a waste liquid treatment system and waste heat recovery equipment. The waste liquid treatment system is composed of a membrane separation unit and an evaporation crystallizer. The waste heat recovery equipment is a plate heat exchanger, and the waste heat recovery equipment is arranged at the condensate outlet of the reactor and the exhaust port of the vacuum low-temperature drying chamber.

[0014] A green and environmentally friendly preparation process for battery-grade iron phosphate, comprising the following steps:

[0015] Step 1: Raw material pretreatment

[0016] Iron source: Use waste lithium iron phosphate battery black powder as raw material, purified by acid leaching-oxidation precipitation method;

[0017] Phosphorus source: Using industrial by-product phosphogypsum as raw material, high-purity phosphoric acid is produced through ammonium carbonate conversion method;

[0018] Step 2: Synthesis reaction

[0019] Mix the iron source solution and the phosphorus source solution at n(Fe):n(P)=1:1.05, add a crystal form control agent, and adjust the pH to 1.8-2.2;

[0020] Hydrothermal reaction is carried out at 160-180°C and 2-4 MPa for 4-6 hours to generate a FePO4·2H2O precursor with a sphericity of ≥95%;

[0021] Step 3: Post-processing

[0022] Aging-washing: Use deionized water for countercurrent rinsing, combined with online conductivity monitoring, and the washing water is treated with ion exchange resin and then recycled.

[0023] Calcination: Under a nitrogen atmosphere, the temperature was raised to 550°C at a rate of 5°C / min and kept at that temperature for 2 h to obtain battery-grade anhydrous iron phosphate.

[0024] Compared with the existing technology, the beneficial effects achieved by the present invention are: the present invention is equipped with a reaction system, a separation and purification system, and a drying and forming system, and adopts a multi-stage series reactor reaction to ensure complete reaction. A microwave heating component and a dispersion module are installed inside to achieve real-time and precise control of temperature, pressure and pH value, shortening the reaction time by 50%, and significantly improving the controllability of particle size. The gas circulation module purifies the gas and reuses it in the reaction system. The membrane separation-electrodialysis-evaporation crystallization process is integrated to realize full-process resource utilization, while realizing the coordinated utilization of waste battery black powder and industrial solid waste, and building a closed-loop industrial chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 It is a process structure diagram of the present invention;

[0027] In the figure: 1-reactor, 2-dispersion module, 3-centrifugation-membrane filtration coupling device, 301-high-speed centrifuge, 302-nanofiltration membrane assembly, 4-electrolytic purification unit, 5-vacuum low-temperature drying chamber, 6-air flow crushing classifier, 7-microwave transmitter, 8-pH electrode, 9-pressure sensor, 10-liquid level gauge, 11-condensation recovery unit, 12-adsorption purification unit, 13-gas recycling unit, 14-waste liquid treatment system, 1401-membrane separation unit, 1402-evaporation crystallizer, 15-waste heat recovery equipment. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] See also Figure 1 The present invention provides a technical solution: a green and environmentally friendly preparation device for battery-grade iron phosphate, including a reaction system, a separation and purification system and a drying and molding system, such as Figure 1 As shown, the reaction system includes a reactor 1, and the number of reactors 1 is multiple. The reactor 1 adopts a multi-stage series arrangement, a titanium alloy lining, acid and alkali corrosion resistance, and a three-layer nested design. The outer layer is an insulating jacket (heat transfer oil or cooling water is introduced), the middle layer is a 316L stainless steel shell, and the inner layer is a titanium alloy lining (thickness ≥5mm), acid and alkali corrosion resistance.

[0030] Each reactor has a volume of 500L, and there are three stages in series. The reactors are connected by pipes with shut-off valves and flow meters to ensure that the materials react step by step. The built-in ultrasonic assisted dispersion module and microwave heating component can achieve real-time and precise control of temperature, pressure, and pH value. The dispersion module 2 and heating component are set inside the reactor 1 to achieve equipment heating and rapid dispersion of materials.

[0031] The separation and purification system includes a centrifugal-membrane filtration coupling device 3 and an electrolytic purification unit 4. The centrifugal-membrane filtration coupling device 3 first removes large particle impurities through a high-speed centrifuge, and then uses a nanofiltration membrane to separate trace metal ions. The membrane flux recovery rate is ≥95%. The electrolytic purification unit 4 uses bipolar membrane electrodialysis technology to convert the impure phosphate solution into high-purity phosphoric acid, achieving the removal of impure metal ions (such as Mn 2+ 、Zn 2+ )’s directional migration and enrichment recovery;

[0032] The drying and molding system includes a vacuum low-temperature drying chamber 5 and an airflow crushing and classifying machine 6. The operating temperature of the vacuum low-temperature drying chamber 5 is ≤80°C. It is also equipped with an infrared radiation heating module, which shortens the drying time to 1 / 3 of the traditional process and effectively avoids material agglomeration. The chamber body is a double-layer stainless steel structure (inner layer 316L, outer layer carbon steel), and the interlayer is vacuumed (limit vacuum 10Pa), with a built-in infrared radiation heating plate (power density 1.5kW / m 2 A stirring paddle is installed inside the chamber to prevent material agglomeration. Temperature is monitored in real time via a thermocouple array. The airflow classifier 6 utilizes a disc-type airflow pulverizer with six nozzles and a classifying wheel within the pulverizing chamber. A nitrogen protection system, including a nitrogen storage tank and an oxygen content analyzer, ensures oxygen content is ≤50ppm. Ultrafine grinding under nitrogen protection, combined with online particle size monitoring, ensures a concentrated product particle size distribution.

[0033] The dispersion module 2 includes an array ultrasonic probe arranged at the bottom of the reactor 1, and 6 sets of annular array ultrasonic probes (frequency 20kHz, power density 0.5W / cm 2 ), pulse excitation is achieved through a frequency conversion controller to avoid local overheating. The heating component includes microwave transmitters 7 arranged around the reactor 1, and 6 microwave transmitters (frequency 2.45GHz, power adjustable range 500-1500W) are embedded around the reactor wall to achieve temperature closed-loop control in conjunction with an infrared thermometer;

[0034] Specifically, the reactor 1 is provided with sensors including a pH electrode 8, a pressure sensor 9 and a liquid level gauge 10. Each reactor is provided with a pH electrode 8 (accuracy ±0.01), a pressure sensor 9 (range 0-5 MPa), and a liquid level gauge 10 (ultrasonic type). Data is collected in real time by a PLC system.

[0035] Specifically, the reaction system also includes a gas circulation module, which includes a condensation recovery unit 11 arranged on the top of the reactor 1. The condensation recovery unit 11 uses a shell and tube heat exchanger with a heat exchange area of ​​2m 2 , the cooling medium adopts ethylene glycol-water mixture (temperature -10°C), the condensation recovery unit 11 is connected to the adsorption purification unit 12, the adsorption purification unit 12 is an activated carbon-molecular sieve composite adsorption tower, the tail gas enters the activated carbon-molecular sieve composite adsorption tower (filling volume 50kg, tower diameter 300mm) after condensation, the adsorption tower adopts a double-column parallel design, one for use and one for standby, to ensure continuous operation, the adsorption purification unit 12 is connected to the gas recycling unit 13, the gas recycling unit 13 is connected to the bottom of the reactor 1, the purified gas is returned to the bottom of the reactor 1 through a compressor (pressure 0.3MPa), and the gas flow is accurately controlled by a mass flowmeter;

[0036] Specifically, the centrifuge-membrane filtration coupling device 3 consists of a high-speed centrifuge 301 and a nanofiltration membrane assembly 302. The high-speed centrifuge 301 is arranged below the discharge port of the reactor 1 and adopts a scraper centrifuge (drum diameter 600 mm, speed 12000 rpm) equipped with a variable frequency drive, which can achieve stepless speed regulation of 0-12000 rpm.

[0037] The liquid outlet of the high-speed centrifuge 301 is connected to the nanofiltration membrane assembly through a pipeline, and the solid phase outlet is connected to the waste residue collection tank;

[0038] Nanofiltration membrane assembly 302 uses polyamide composite membrane (molecular weight cut-off 300Da), membrane area 10m 2 , operating pressure 1.5MPa, using cross-flow filtration mode (flow rate 3m / s), membrane flux stable at 15L / (m 2 h)

[0039] Specifically, the electrolytic purification unit 4 is composed of a bipolar membrane electrodialysis cell, the cell body is made of polypropylene, and has 100 pairs of bipolar membranes (membrane area 0.5m 2 / pair), the cathode and anode chambers were filled with titanium-based ruthenium-iridium coated electrodes (electrode spacing 5mm), and the current density was controlled at 50A / m 2 , voltage range 20-50V, powered by DC power supply, conductivity online monitoring (end point ≤ 10μS / cm);

[0040] Specifically, it also includes environmental protection and resource utilization equipment, which includes a waste liquid treatment system 14 and a waste heat recovery device 15. The waste liquid treatment system 14 consists of a membrane separation unit 1401 and an evaporation crystallizer 1402. The membrane separation unit 1401 is used for nanofiltration concentrate to enter the reverse osmosis membrane assembly, and the fresh water is reused to the front-end process. The concentrated liquid enters the electrodialysis unit. The evaporation crystallizer 1402 adopts MVR mechanical vapor recompression technology with an evaporation temperature of 80°C and a steam compression ratio of 1:8. It can produce ammonium sulfate crystals as a by-product, thereby achieving green environmental protection. The waste heat recovery device 15 is a plate heat exchanger, which is arranged at the condensate outlet of the reactor 1 and the exhaust port of the vacuum low-temperature drying chamber 5;

[0041] When the present invention is working, the iron source solution and the phosphorus source solution are mixed in proportion and then injected into the reactor 1 for reaction. The dispersion module 2 and the microwave heating component work to accelerate the reaction and generate a precursor. The condensation recovery unit 11, the adsorption purification unit 12 and the gas recycling unit 13 realize gas circulation recovery. After the reaction is completed, it enters the centrifugal-membrane filtration coupling device for purification, and is further purified by the electrolytic purification unit 4. Finally, it enters the vacuum low-temperature drying chamber 5 for drying, and is crushed and classified in the air flow crushing and classifying machine 6. The nanofiltration concentrate generated by the centrifugal-membrane filtration coupling device 3 enters the membrane separation unit 1401, the fresh water is reused to the previous process, and the concentrated liquid enters the evaporation crystallizer 1402.

[0042] A green and environmentally friendly preparation process for battery-grade iron phosphate, comprising the following steps:

[0043] Step 1: Raw material pretreatment

[0044] Iron source: Use waste lithium iron phosphate battery black powder (LiFePO4 content ≥ 85%) as raw material, purified by acid leaching-oxidation precipitation method;

[0045] Phosphorus source: Using industrial by-product phosphogypsum (CaSO4·2H2O) as raw material, high-purity phosphoric acid is produced through ammonium carbonate conversion method;

[0046] Step 2: Synthesis reaction

[0047] The iron source solution and the phosphorus source solution were mixed at n(Fe):n(P)=1:1.05, a crystal form control agent (citric acid / gluconic acid composite system) was added, and the pH was adjusted to 1.8-2.2;

[0048] Hydrothermal reaction is carried out at 160-180°C and 2-4 MPa for 4-6 hours to generate a FePO4·2H2O precursor with a sphericity of ≥95%;

[0049] Step 3: Post-processing

[0050] Aging-washing: Use deionized water for countercurrent rinsing, combined with online conductivity monitoring, and the washing water is treated with ion exchange resin and then recycled.

[0051] Calcination: Under a nitrogen atmosphere, the temperature was raised to 550°C at a rate of 5°C / min and kept at that temperature for 2 h to obtain battery-grade anhydrous iron phosphate.

[0052] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0053] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A green and environmentally friendly preparation device for battery-grade iron phosphate, comprising a reaction system, a separation and purification system, and a drying and molding system, characterized in that: The reaction system comprises a reactor (1), wherein the number of the reactors (1) is multiple and the reactors (1) are arranged in multi-stage series, and a dispersion module (2) and a heating component are arranged inside the reactor (1); The separation and purification system includes a centrifugal-membrane filtration coupling device (3) and an electrolytic purification unit (4); The drying and molding system includes a vacuum low-temperature drying chamber (5) and an air flow crushing and classifying machine (6); The dispersion module (2) includes an array-type ultrasonic probe arranged at the bottom of the reactor (1), and the heating component includes a microwave transmitter (7) arranged around the reactor (1).

2. The green and environmentally friendly preparation device for battery-grade iron phosphate according to claim 1, characterized in that: Sensors are provided inside the reactor (1), and the sensors include a pH electrode (8), a pressure sensor (9), and a liquid level meter (10).

3. The green and environmentally friendly preparation device for battery-grade iron phosphate according to claim 2, characterized in that: The reaction system further comprises a gas circulation module, wherein the gas circulation module comprises a condensation recovery unit (11) arranged at the top of the reactor (1), the condensation recovery unit (11) is connected to an adsorption purification unit (12), the adsorption purification unit (12) is connected to a gas recycling unit (13), and the gas recycling unit (13) is connected to the bottom of the reactor (1).

4. The green and environmentally friendly preparation device for battery-grade iron phosphate according to claim 3, characterized in that: The centrifugation-membrane filtration coupling device (3) consists of a high-speed centrifuge (301) and a nanofiltration membrane assembly (302).

5. The green and environmentally friendly preparation device for battery-grade iron phosphate according to claim 4, characterized in that: The electrolytic purification unit (4) is composed of a bipolar membrane electrodialysis cell.

6. The green and environmentally friendly preparation device for battery-grade iron phosphate according to claim 5, characterized in that: The invention also includes environmental protection and resource utilization equipment, which includes a waste liquid treatment system (14) and a waste heat recovery device (15). The waste liquid treatment system (14) is composed of a membrane separation unit (1401) and an evaporation crystallizer (1402). The waste heat recovery device (15) is a plate heat exchanger. The waste heat recovery device (15) is arranged at the condensate outlet of the reactor (1) and the exhaust port of the vacuum low-temperature drying chamber (5).

7. A green and environmentally friendly preparation process for battery-grade iron phosphate, characterized by: The following steps are involved: Step 1: Raw material pretreatment Iron source: Use waste lithium iron phosphate battery black powder as raw material, purified by acid leaching-oxidation precipitation method; Phosphorus source: Using industrial by-product phosphogypsum as raw material, high-purity phosphoric acid is produced through ammonium carbonate conversion method; Step 2: Synthesis reaction Mix the iron source solution and the phosphorus source solution at n(Fe):n(P)=1:1.05, add a crystal form control agent, and adjust the pH to 1.8-2.2; Hydrothermal reaction is carried out at 160-180°C and 2-4 MPa for 4-6 hours to generate a FePO4·2H2O precursor with a sphericity of ≥95%; Step 3: Post-processing Aging-washing: Use deionized water for countercurrent rinsing, combined with online conductivity monitoring, and the washing water is treated with ion exchange resin and then recycled. Calcination: Under a nitrogen atmosphere, the temperature was raised to 550°C at a rate of 5°C / min and kept at that temperature for 2 h to obtain battery-grade anhydrous iron phosphate.

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