Production equipment and method for producing lithium iron manganese phosphate positive electrode material precursor

Abstract

The application discloses a production device and a production method of a lithium manganese iron phosphate positive electrode material precursor, relates to the technical field of lithium manganese iron phosphate synthesis, and comprises the following: an iron dissolution reaction kettle for generating an iron salt solution; a manganese dissolution reaction kettle for mixing the iron salt solution, a manganese source and a reducing agent to generate a manganese iron salt solution; a liquid preparation kettle for mixing the manganese iron salt solution and an additive to generate a mixed solution, wherein the additive is a phosphorus source and a lithium source, or the additive is phosphoric acid; a synthesis furnace for generating the lithium manganese iron phosphate positive electrode material precursor; in the application, the iron source is used to generate the iron salt solution with hydrochloric acid, the iron salt solution is used to generate the manganese iron salt mixed solution with the manganese source, then the reducing agent is added to generate the mixed solution in which manganese is kept as divalent and iron is kept as divalent, and finally the additive is added to prepare the manganese iron phosphorus mixed solution or the manganese iron lithium phosphorus mixed solution, so that the manganese iron is uniformly distributed, and the lithium manganese iron phosphate positive electrode material precursor powder with stable product quality and good product quality can be generated in the synthesis furnace.

Description

Technical Field

[0001] This invention relates to the field of lithium manganese iron phosphate synthesis technology, and in particular to a production equipment and method for a lithium manganese iron phosphate cathode material precursor. Background Technology

[0002] Previous methods for synthesizing lithium manganese iron phosphate (LFP) were mainly divided into solid-phase and liquid-phase methods. The solid-phase method uses a mixture of manganese, iron, phosphorus, and lithium sources for sintering. It has advantages such as simple process, few required equipment, easy production, and low cost, and has been widely used in the preparation of LFP cathode materials. However, due to the difficulty in solving the problem of uneven distribution of manganese and iron elements, it affects the ion transport rate, rate performance, specific capacity, and cycle performance of the material, making it difficult for its comprehensive electrochemical performance to meet the requirements of practical applications, thus restricting the commercial application of LFP materials. Improved solid-phase methods are used to prepare manganese iron precursors, such as ferrous manganese oxalate, ferrous manganese carbonate, ferrous manganese phosphate, and ferrous manganese pyrophosphate. However, the uneven distribution of manganese and iron still exists, and it is impossible to prepare precursors with stable quality. Liquid-phase methods mainly refer to the sol-gel method and the hydrothermal method. In the sol-gel method, phosphorus source, manganese source (manganese nitrate), iron source (ferric nitrate), and lithium source are dissolved evenly in a certain proportion, and then crystallized to obtain a liquid slurry. After preheating, a honeycomb gel is formed, which is then crushed, rolled, sintered, and ground to obtain the finished lithium manganese iron phosphate. However, the sol-gel method has two problems: First, when the sol-gel method crystallizes from the solution to form a slurry, the crystallization of manganese and iron elements is not synchronized, resulting in uneven mixing of the two elements and the appearance of impurities in the solid solution of the cathode material, causing manganese to dissolve. Second, the nitrate ions in the raw materials lead to environmental pressure in the treatment of nitrogen oxide tail gas and also increase production costs. The hydrothermal method uses ferrous sulfate, manganese sulfate, phosphoric acid, and lithium hydroxide in a high-temperature and high-pressure hydrothermal reactor to generate lithium iron manganese phosphate, lithium sulfate, and water. The primary particle size of lithium manganese iron phosphate produced by this method is relatively uniform, but there is also the problem of uneven distribution due to the asynchronous crystallization of manganese and iron. Moreover, the hydrothermal method has expensive equipment and high production costs, making it unsuitable for large-scale commercial promotion.

[0003] Therefore, there is an urgent need for production equipment that can produce lithium manganese iron phosphate cathode material precursors with uniform manganese iron distribution. Summary of the Invention

[0004] The purpose of this invention is to provide a production equipment and method for lithium manganese iron phosphate cathode material precursors. The method utilizes an iron source, a manganese source, hydrochloric acid, a reducing agent, and additives to prepare a mixed solution in which both manganese and iron maintain a +2 valence. This facilitates the generation of lithium manganese iron phosphate cathode material precursors with uniform manganese and iron distribution, stable product quality, and good product quality in the synthesis furnace.

[0005] To achieve the above objectives, the present invention provides the following solution: The present invention provides a production apparatus for a lithium manganese iron phosphate cathode material precursor, comprising: an iron dissolving reactor for generating an iron salt solution; a manganese dissolving reactor for mixing the iron salt solution, a manganese source, and a reducing agent to generate a manganese iron salt solution, wherein the inlet of the manganese dissolving reactor is connected to the outlet of the iron dissolving reactor; a mixing vessel for mixing the manganese iron salt solution with additives to generate a mixed solution, wherein the inlet of the mixing vessel is connected to the outlet of the manganese dissolving reactor, wherein the additives are a phosphorus source and a lithium source, or the additives are phosphoric acid; and a synthesis furnace for generating the lithium manganese iron phosphate cathode material precursor, wherein the inlet of the synthesis furnace is connected to the outlet of the mixing vessel.

[0006] Preferably, the production equipment for the lithium manganese iron phosphate cathode material precursor further includes a purification device, which is located between the iron dissolution reactor and the synthesis furnace, and the purification device is a solid-liquid separator.

[0007] Preferably, the production equipment for the lithium manganese iron phosphate cathode material precursor further includes a pre-concentrator, which includes a Venturi structure and a gas-liquid separation structure. The inlet of the Venturi structure is connected to the liquid preparation vessel, the outlet is connected to the inlet of the gas-liquid separation structure, the negative pressure suction port is connected to the high-temperature flue gas channel of the synthesis furnace, and the liquid outlet of the gas-liquid separation structure is connected to the synthesis furnace.

[0008] Preferably, the gas outlet of the gas-liquid separation structure is connected to a hydrochloric acid storage tank for storing hydrochloric acid via an absorption tower, and the hydrochloric acid storage tank is connected to the hydrochloric acid inlet of the iron dissolving reactor.

[0009] Preferably, the liquid preparation vessel is connected to the top of the inner cavity of the synthesis furnace through an atomizing device, and the atomizing device is connected to the liquid preparation vessel, the demineralized water supply pipeline, and the high-pressure protective gas supply pipeline through valves.

[0010] Preferably, the synthesis furnace includes a furnace body and a burner for ejecting hot gas flow, the burner being disposed on the furnace body.

[0011] Preferably, the production equipment for the lithium manganese iron phosphate cathode material precursor further includes a solution preparation tank, the inlet of which is connected to the solution preparation vessel, and the outlet of which is connected to the synthesis furnace. The solution preparation tank is provided with an inlet for supplying the additive.

[0012] Preferably, the bottom of the synthesis furnace is provided with a cooler for cooling the precursor powder of lithium manganese iron phosphate cathode material, and the inlet of the cooler is connected to the outlet of the synthesis furnace.

[0013] Preferably, the production equipment for the lithium manganese iron phosphate cathode material precursor further includes a processing unit for processing the lithium manganese iron phosphate cathode material precursor powder. The processing unit includes a crusher, a demagnetizer, a screening machine, a silo, and a packaging machine arranged in sequence. The feed inlet of the crusher is connected to the discharge outlet of the cooler.

[0014] The present invention also provides a method for producing lithium manganese iron phosphate cathode material precursor using the above-mentioned production equipment, comprising the following steps:

[0015] S1: Hydrochloric acid is added to the iron dissolving reactor through the hydrochloric acid inlet, and an iron source is added to the iron dissolving reactor through the iron source inlet. The iron source reacts with the hydrochloric acid to generate an iron salt solution, which is then transferred to the manganese dissolving reactor.

[0016] S2: Add manganese source into manganese dissolution reactor through manganese source inlet to generate manganese iron salt solution;

[0017] S3: Add reducing agent into the manganese dissolution reactor through the reducing agent inlet to keep manganese and iron in the manganese iron salt solution at +2 oxidation state;

[0018] S4: Transfer the manganese iron salt solution to the mixing tank, add the additive into the mixing tank through the additive inlet, and prepare a manganese iron phosphorus mixture or a manganese iron lithium phosphorus mixture.

[0019] S5: A mixture of manganese iron phosphorus or manganese iron lithium phosphorus is fed into a synthesis furnace for heating, and the reaction produces ferrous manganese pyrophosphate powder or lithium manganese iron phosphate powder. The ferrous manganese pyrophosphate powder or lithium manganese iron phosphate powder is a precursor powder for lithium manganese iron phosphate cathode material.

[0020] The present invention achieves the following main technical effects compared to the prior art:

[0021] First, an iron salt solution is generated using an iron source and hydrochloric acid. Then, a manganese-iron salt mixture is generated using the iron salt solution and a manganese source. Next, a reducing agent is added to generate a mixture in which both manganese and iron maintain a +2 valence. Finally, additives are added to prepare a manganese-iron-phosphorus mixture or a manganese-iron-lithium-phosphorus mixture. This achieves uniform distribution of manganese and iron, which is beneficial for generating stable and high-quality lithium manganese-iron-phosphorus cathode material precursor powder in the synthesis furnace.

[0022] Other solutions of the present invention achieve the following technical effects compared with the prior art:

[0023] The pre-concentrator can utilize the heat from the high-temperature flue gas of the synthesis furnace to preheat the manganese-iron-phosphorus mixture or the manganese-iron-lithium-phosphorus mixture. At the same time, the separated acid gas is transported to the absorption tower, and the hydrochloric acid recovered from the acid gas in the absorption tower can be supplied to the iron dissolution reactor for use.

[0024] The liquid preparation and storage tank not only provides a place to test whether the manganese iron phosphorus mixture or manganese iron lithium phosphorus mixture is qualified before it enters the synthesis furnace, but also serves as a device for receiving and storing the manganese iron phosphorus mixture or manganese iron lithium phosphorus mixture. It can continuously supply the manganese iron phosphorus mixture or manganese iron lithium phosphorus mixture into the synthesis furnace, realizing the continuous production of precursor powder of lithium manganese iron phosphate cathode material. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a system diagram of the production equipment for the lithium manganese iron phosphate cathode material precursor in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the pre-concentrator in an embodiment of the present invention;

[0028] The components include: 1. Iron dissolving reactor; 2. Manganese dissolving reactor; 3. Liquid preparation vessel; 4. Impurity removal device; 5. Liquid preparation storage tank; 6. Pre-concentrator; 7. Atomizing device; 8. Synthesis furnace; 9. Cooler; 10. Crusher; 11. Demagnetizer; 12. Screening machine; 13. Silo; 14. Packaging machine; 15. Absorption tower; 16. Venturi structure; 17. Gas-liquid separation structure; 18. Circulating pump; 19. Feed pump; 20. Hydrochloric acid storage tank. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The purpose of this invention is to provide a production equipment and method for lithium manganese iron phosphate cathode material precursors to solve the problems existing in the prior art. By using iron source, manganese source, hydrochloric acid, reducing agent and additives to prepare a mixed solution in which manganese and iron retain a +2 valence, it is beneficial to generate lithium manganese iron phosphate cathode material precursors with uniform manganese and iron distribution, stable product quality and good product quality in the synthesis furnace.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Please refer to the following: Figure 1 , Figure 2 As shown, a production apparatus for a lithium manganese iron phosphate cathode material precursor is provided, comprising an iron dissolution reactor 1 for generating an iron salt solution, a manganese dissolution reactor 2 for mixing the iron salt solution, a manganese source, and a reducing agent to generate a manganese iron salt solution, a mixing vessel 3 for mixing the manganese iron salt solution with additives to generate a mixed solution, and a synthesis furnace 8 for generating the lithium manganese iron phosphate cathode material precursor. The iron dissolution reactor 1 is provided with a hydrochloric acid inlet and an iron source inlet; the inlet of the manganese dissolution reactor 2 is connected to the outlet of the iron dissolution reactor 1, and the manganese dissolution reactor 2 is also provided with a manganese source inlet and a reducing agent inlet; the inlet of the mixing vessel 3 is connected to the outlet of the manganese dissolution reactor 2, and the mixing vessel 3 is also connected to the outlet of the manganese dissolution reactor 2. The equipment is equipped with an additive inlet, which is a phosphorus source and a lithium source. In this case, the mixing tank 3 is equipped with a phosphorus source inlet and a lithium source inlet, or the additive is phosphoric acid, in which case the mixing tank 3 is equipped with a phosphoric acid inlet. The inlet of the synthesis furnace 8 is connected to the outlet of the mixing tank 3. When using this equipment, an iron source and hydrochloric acid are first used to generate an iron salt solution, and then the iron salt solution and a manganese source are used to generate a manganese-iron salt mixture. Then, a reducing agent is added to generate a mixture in which manganese and iron are both kept at +2 valence. Finally, additives are added to prepare a manganese-iron-phosphorus mixture or a manganese-iron-lithium-phosphorus mixture, which achieves uniform distribution of manganese and iron. This is beneficial for generating stable and high-quality manganese-iron-lithium phosphate cathode material precursor powder in the synthesis furnace 8.

[0033] In this embodiment, the iron source is at least one of Fe, FeO, Fe2O3, Fe3O4, FeCO3, FeC2O4, FeOOH, FeCl2, and FeCl3; the manganese source is at least one of Mn, MnO, MnCO3, MnC2O4, and MnCl2; the reducing agent is at least one of citric acid, oxalic acid, tartaric acid, formic acid, and hydroxylamine hydrochloride; the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium phosphate, and lithium dihydrogen phosphate; and the phosphorus source is at least one of phosphoric acid, iron phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium phosphate, and lithium dihydrogen phosphate.

[0034] The number of iron dissolving reactor 1 and manganese dissolving reactor 2 shall be at least one. If a production capacity of 10,000 tons / year is to be provided, the total capacity of iron dissolving reactor 1 and manganese dissolving reactor 2 shall be at least 90 cubic meters. The materials of iron dissolving reactor 1 and manganese dissolving reactor 2 shall be FRP or other acid corrosion resistant materials, and shall have a certain heat resistance, be able to withstand high temperatures of 80 to 120°C, and have a certain thermal insulation effect, with a thermal conductivity of less than 10 kJ / (m·h·K).

[0035] The iron dissolving reactor 1 and the manganese dissolving reactor 2 can be equipped with high liquid level alarm and ultra-high liquid level alarm functions through a liquid level sensor in conjunction with an alarm device. The high liquid level and ultra-high liquid level settings can be selected according to actual needs. The iron dissolving reactor 1 and the manganese dissolving reactor 2 can be equipped with high temperature alarm and ultra-high temperature alarm functions through a temperature sensor in conjunction with an alarm device. The high temperature and ultra-high temperature settings can be selected according to actual needs. The iron dissolving reactor 1 and the manganese dissolving reactor 2 can be equipped with high flow rate alarm and ultra-high flow rate alarm functions (for hydrochloric acid and additives) through a flow rate sensor in conjunction with an alarm device. The high flow rate and ultra-high flow rate settings can be selected according to actual needs.

[0036] The production equipment for the precursor of lithium manganese iron phosphate cathode material also includes a purification device 4. The purification device 4 is set between the iron dissolution reactor 1 and the synthesis furnace 8. In this embodiment, it is specifically set between the liquid preparation vessel 3 and the synthesis furnace 8. The purification device 4 is a solid-liquid separator, such as a filter press, centrifuge, or filter. The purification device 4 removes impurities from the manganese iron phosphate mixture or manganese iron lithium phosphate mixture output from the liquid preparation vessel 3, removing undissolved raw materials and other metal particles (such as Cu, SiO2, etc.). The filtered residue after purification is collected and transported. The purified manganese iron phosphate mixture or manganese iron lithium phosphate mixture continues to be transported.

[0037] Multiple impurity removal devices 4 are provided and exist in parallel. When one impurity removal device 4 fails, other impurity removal devices 4 can be started to work, ensuring the continuity of work.

[0038] The production equipment for the lithium manganese iron phosphate cathode material precursor in this embodiment also includes a pre-concentrator 6. The pre-concentrator 6 includes a Venturi structure 16 and a gas-liquid separation structure 17. The inlet of the Venturi structure 16 is connected to the liquid preparation vessel 3, the outlet is connected to the inlet of the gas-liquid separation structure 17, the negative pressure suction port is connected to the high-temperature flue gas channel of the synthesis furnace 8, and the liquid outlet of the gas-liquid separation structure 17 is connected to the synthesis furnace 8. The heat of the high-temperature flue gas of the synthesis furnace 8 can be used to preheat and concentrate the manganese iron phosphate mixture or the manganese iron lithium phosphate mixture (concentration is completed by evaporation of water after preheating), thereby improving the reaction efficiency of the manganese iron phosphate mixture or the manganese iron lithium phosphate mixture in the synthesis furnace 8.

[0039] In this embodiment, the pre-concentrator 6 is located between the impurity removal device 4 and the synthesis furnace 8.

[0040] A circulating pump 18 can be set to provide power for the manganese-iron-phosphorus mixture or the manganese-iron-lithium-phosphorus mixture. The inlet of the circulating pump 18 is connected to the outlet of the gas-liquid separation structure 17 and the outlet of the impurity removal device 4. The outlet of the circulating pump 18 is connected to the inlet of the synthesis furnace 8 and the venturi structure 16. A feed pump 19 is provided on the connecting pipeline between the circulating pump 18 and the synthesis furnace 8.

[0041] The Venturi structure 16 and the gas-liquid separation structure 17 can be integrated or separated. Both are made of acid-resistant materials. The Venturi structure 16 can withstand a high temperature of 600°C and an internal negative pressure of nearly one atmosphere. In this embodiment, the diameter of the throat portion of the Venturi structure 16 is 150mm to 500mm, and the height of the Venturi structure 16 is 3000mm to 5000mm. The diameter of the gas-liquid separation structure 17 is 750mm to 1250mm, and the height of the gas-liquid separation structure 17 is 2000mm to 3000mm.

[0042] The outlet of the gas-liquid separation structure 17 is connected to the hydrochloric acid storage tank 20 for storing hydrochloric acid through the absorption tower 15. The hydrochloric acid storage tank 20 is connected to the hydrochloric acid inlet of the iron dissolving reactor 1, so that the HCl acid gas separated by the gas-liquid separation structure 17 is transported to the absorption tower 15. The absorption tower 15 recovers the hydrochloric acid in the acid gas and can supply it to the iron dissolving reactor 1 for use. In this embodiment, the absorption tower 15 recovers more than 80% of the HCl in the acid gas discharged from the gas-liquid separation structure 17 to generate regenerated hydrochloric acid with a concentration of 10% to 25%. The waste gas after acid recovery is sent to the waste gas treatment system for treatment before being discharged.

[0043] To improve the reaction effect of the manganese-iron-phosphorus mixture or manganese-iron-lithium-phosphorus mixture in the synthesis furnace 8, the mixing tank 3 is connected to the top of the inner cavity of the synthesis furnace 8 through an atomizing device 7. The atomizing device 7 is connected to the mixing tank 3, the demineralized water supply pipeline, and the high-pressure protective gas supply pipeline through valves. The atomizing device 7 can be adapted to different modes in the synthesis furnace 8 by opening and closing the valves. In the acid mist production mode of the synthesis furnace 8, the atomizing device 7 receives the manganese-iron-phosphorus mixture or manganese-iron-lithium-phosphorus mixture and the high-pressure protective gas (nitrogen or argon). The high-pressure protective gas provides the atomization driving force for the manganese-iron-phosphorus mixture or manganese-iron-lithium-phosphorus mixture, and at the same time forms a protective atmosphere to prevent ferrous ion oxidation. In this embodiment, the atomizing device 7 atomizes the manganese-iron-phosphorus mixture or manganese-iron-lithium-phosphorus mixture with a flow rate of 2000 L / h to 14000 L / h, and the high-pressure protective gas flow rate is 200 to 2800 m³ / h. 3 The pressure must be greater than 0.3 MPa, and the average particle size of the mist droplets must be 10 μm to 100 μm for acid mist production. In the water mist oven drying mode and water mist hot stop mode of the synthesis furnace 8, the atomizing device 7 receives demineralized water and sprays it on the top of the inner cavity of the synthesis furnace 8 to avoid overheating of the furnace top and protect the synthesis furnace 8 body. In this embodiment, the atomizing device 7 atomizes demineralized water with a flow rate of 2000 L / h to 14000 L / h for water mist oven drying mode and water mist hot stop mode, and the demineralized water pressure is greater than 1 standard atmosphere.

[0044] In this embodiment, the atomizing device 7 is located between the pre-concentrator 6 and the synthesis furnace 8.

[0045] The atomizing device 7 also includes a shutdown mode and a test gun mode. In the shutdown mode, the spray gun is in the test gun position outside the synthesis furnace 8, and the atomizing device 7 does not provide atomization function. In the test gun mode, the spray gun is in the test gun position outside the synthesis furnace 8, and the atomizing device 7 provides water mist function to test the atomization effect. The atomizing device 7 can be detached from the synthesis furnace 8. After the atomizing device is detached by a pneumatic or electric machine, it can enter the shutdown mode and the test gun mode.

[0046] The atomizing device 7 is equipped with multiple spray guns, with at least one nozzle at the end of each spray gun. The nozzles must be made of acid-resistant hard materials, such as stainless steel, titanium alloy, or niobium. The nozzles are evenly distributed to improve the uniformity of the spray.

[0047] The synthesis furnace 8 includes a furnace body and burners for ejecting hot gas flow. The burners are connected to fire channels for supplying fuel gas and air. The burners are mounted on the furnace body. Specifically, multiple evenly distributed burners can be installed on the inner wall of the furnace body to improve heating uniformity and efficiency. In this embodiment, the furnace body is composed of at least four layers of materials bonded together, consisting of an outer insulation layer, a middle metal furnace body, an inner insulation layer, and an inner refractory layer from the outside to the inside. The refractory layer is generally made of acid-resistant and high-temperature-resistant refractory materials. The furnace chamber diameter of the synthesis furnace 8 is 6000mm to 15000mm, and the furnace body height is 15000mm to 40000mm. The highest temperature inside the furnace chamber of the synthesis furnace 8 is 1100℃, and the reaction temperature is 550℃ to 750℃. The time from the start of the synthesis reaction to the falling of the atomized droplets to the bottom of the furnace in the synthesis furnace 8 is 10 to 60 seconds. The production efficiency of the synthesis furnace 8 is 1t / h to 7t / h.

[0048] In this embodiment, the synthesis furnace 8 includes multiple operating modes, namely, minor repair mode, major repair mode, cold stop standby mode, heating mode, water mist furnace drying mode, acid mist production mode, water mist hot stop mode, and cooling mode. The state and function of the synthesis furnace 8 under different modes are as follows:

[0049] The minor repair mode is a maintenance state in which no scaffolding is erected inside the synthesis furnace 8. In the minor repair mode, the synthesis furnace 8 is in a shutdown state, and the relevant energy required for the maintenance work is isolated and tagged as appropriate.

[0050] The overhaul mode is a maintenance state that requires scaffolding to be erected inside the synthesis furnace 8. In the overhaul mode, the synthesis furnace 8 is completely shut down, and all energy related to the synthesis furnace 8 has been isolated and tagged.

[0051] The cold stop standby mode is the shutdown phase when the synthesis furnace 8 is at room temperature. In the cold stop standby mode, all energy related to the synthesis furnace 8 has been released from isolation and can be ignited and heated at any time.

[0052] The heating mode is the stage where the synthesis furnace 8 heats up to 450℃ after ignition. In the heating mode, the function of the synthesis furnace 8 is to use the heat energy generated by the combustion of gas and hot air to slowly heat up the entire synthesis furnace 8 to enter the water mist furnace drying mode. In the heating mode, the air-fuel ratio (volume ratio of combustion air to gas) is between 7 and 20. The atomizing device 7 is still in the off mode, but preparations should be made to switch to the water mist furnace drying mode. In the heating mode, several temperature platforms should be set between 100℃ and 420℃. A temperature platform refers to a temperature that remains constant for a period of time. The overall temperature change curve is stepped. The tread of the step is the temperature platform. The setting of temperature platforms can protect the various materials of the synthesis furnace 8 and prevent the problem of excessive temperature gradient of the furnace wall material due to excessive heating. At the same time, it can keep the various materials in a basically synchronous heating state.

[0053] The water mist oven drying mode is the stage from when the temperature of synthesis furnace 8 is 450℃ until the start of acid mist production mode. In this mode, the function of synthesis furnace 8 is to completely evaporate the liquid water inside the furnace and consume all remaining oxygen, creating an oxygen-free environment to prevent ferrous ion oxidation. This prepares all conditions for synthesis furnace 8 to enter the acid mist production mode. In water mist oven drying mode, the air-fuel ratio is between 7 and 15. A suitable air-fuel ratio ensures that the oxygen in the combustion air is consumed to less than 1% in the combustion chamber. In water mist oven drying mode, atomizing device 7 needs to be activated to operate in normal water mist mode to protect synthesis furnace 8.

[0054] The acid mist production mode is the stage in which the synthesis furnace 8 formally produces the precursor of lithium manganese iron phosphate cathode material. In the acid mist production mode, the function of the synthesis furnace 8, together with the atomizing device 7, is to provide various conditions required for the atomization high-temperature synthesis reaction. The atomization high-temperature synthesis reaction refers to the reaction process in which a solution of a certain ratio is atomized, dried at high temperature, and then subjected to one or more of a series of chemical reactions such as precipitation reaction, condensation reaction, combination reaction, and decomposition reaction to form the target solid powder. It is divided into two stages: atomization and high-temperature synthesis. The synthesis furnace 8 causes the atomized manganese iron phosphate mixture or manganese iron lithium phosphate mixture to undergo a high-temperature synthesis reaction in a high-temperature environment to generate lithium manganese iron phosphate cathode material precursor powder. The generated lithium manganese iron phosphate cathode material precursor powder is collected at the bottom of the furnace. In the acid mist production mode, the air-fuel ratio is between 7 and 15. The appropriate air-fuel ratio ensures that the oxygen in the combustion air is consumed to less than 1% in the fire channel, avoiding a large amount of oxygen being carried into the synthesis furnace 8 and causing ferrous ion oxidation. In the acid mist production mode, the atomizing device 7 operates in acid mist mode.

[0055] The water mist hot stop mode is the stage when the synthesis furnace 8 is about to switch back to the acid mist production mode after pausing production, or the stage before completely stopping production and entering the cooling mode. During this stage, the temperature of the synthesis furnace 8 is greater than or equal to 450℃. In the water mist hot stop mode, the function of the synthesis furnace 8 is to keep the synthesis furnace 8 in a hot stop state. It can switch back to the acid mist production mode as needed. The gas flow rate is basically the same as in the acid mist production mode, and the air-fuel ratio is between 7 and 15. The appropriate air-fuel ratio ensures that the oxygen in the combustion air is completely consumed in the fire channel. In the water mist hot stop mode, the atomizing device 7 still operates. The atomizing device 7 operates in the normal water mist mode to protect the synthesis furnace 8.

[0056] The cooling mode is the stage where the synthesis furnace 8 cools down from 450°C to room temperature. During the cooling mode, the atomizing device 7 operates in shutdown mode and stops supplying gas.

[0057] The production equipment for lithium manganese iron phosphate cathode material precursor also includes a solution preparation tank 5. The inlet of the solution preparation tank 5 is connected to the solution preparation vessel 3, and the outlet is connected to the synthesis furnace 8. The solution preparation tank 5 is equipped with an inlet for adding additives. The composition of the additives is the same as that of the additives added in the solution preparation vessel 3. The solution preparation tank 5 not only provides a place to test whether the manganese iron phosphate mixture or the manganese iron lithium phosphate mixture is qualified before it enters the synthesis furnace 8, but also serves as a device for receiving and storing the manganese iron phosphate mixture or the manganese iron lithium phosphate mixture. It can continuously supply the manganese iron phosphate mixture or the manganese iron lithium phosphate mixture into the synthesis furnace 8, realizing the continuous production of lithium manganese iron phosphate cathode material precursor.

[0058] The number of liquid preparation storage tanks 5 shall be at least one. If a production capacity of 10,000 tons / year is required, the total capacity of all liquid preparation storage tanks 5 shall be at least 60 cubic meters. The liquid preparation storage tanks 5 shall be made of PPH or other acid corrosion resistant materials, with an operating temperature of up to 100℃, and shall have the characteristics of wear resistance, high temperature resistance and non-toxicity.

[0059] In this embodiment, the liquid preparation tank 5 is located between the impurity removal device 4 and the pre-concentrator 6.

[0060] A cooler 9 is provided at the bottom of the synthesis furnace 8 to cool the lithium manganese iron phosphate cathode material precursor powder. The inlet of the cooler 9 is connected to the outlet of the synthesis furnace 8, and the outlet of the synthesis furnace 8 is located at the bottom of the furnace. A valve is provided between the inlet of the cooler 9 and the outlet of the synthesis furnace 8. By opening the valve, the lithium manganese iron phosphate cathode material precursor powder is transferred to the cooler 9 for cooling. In this embodiment, the cooler 9 can cool the lithium manganese iron phosphate cathode material precursor powder at about 400°C to about 80°C.

[0061] In this embodiment, after the cooler 9 cools the lithium manganese iron phosphate cathode material precursor powder, a processing unit is also provided to process the lithium manganese iron phosphate cathode material precursor powder. The processing unit includes a crusher 10, a demagnetizer 11, a screening machine 12, a hopper 13, and a packaging machine 14 arranged in sequence. The feed inlet of the crusher 10 is connected to the discharge outlet of the cooler 9. The function of the crusher 10 is to crush the lithium manganese iron phosphate cathode material precursor powder to improve its particle size uniformity. The demagnetizer 11 is used to remove the crushed lithium manganese iron phosphate. Magnetic substances in the cathode material precursor powder; sieving machine 12 is used to sieve the demagnetized lithium manganese iron phosphate cathode material precursor powder to select lithium manganese iron phosphate cathode material precursor powder with qualified particle size; silo 13 is used to store qualified lithium manganese iron phosphate cathode material precursor powder after sieving; packaging machine 14 is used to package, heat seal and wrap the qualified lithium manganese iron phosphate cathode material precursor powder; the lithium manganese iron phosphate cathode material precursor powder packaged by packaging machine 14 is transferred to the finished product warehouse by transfer equipment.

[0062] In this embodiment, the packaged lithium manganese iron phosphate cathode material precursor product has an average particle size of 1–20 μm and a loose packing density of 0.2–0.4 g / cm³. 3 The tap density is 0.4–0.8 g / cm³. 3 The carbon content is less than 0.2%.

[0063] In this embodiment, the precursor powder for the lithium manganese iron phosphate cathode material is either manganese ferrous pyrophosphate powder or lithium manganese iron phosphate powder.

[0064] The present invention also provides a method for producing lithium manganese iron phosphate cathode material precursor using the above-mentioned production equipment, comprising the following steps:

[0065] S1: Hydrochloric acid is added into the iron dissolving reactor 1 through the hydrochloric acid inlet, and an iron source is added into the iron dissolving reactor 1 through the iron source inlet. The iron source reacts with the hydrochloric acid to generate an iron salt solution, which is then transferred to the manganese dissolving reactor 2.

[0066] S2: Add manganese source into manganese dissolution reactor 2 through manganese source inlet, and react to generate manganese iron salt solution;

[0067] S3: Add reducing agent into manganese dissolution reactor 2 through reducing agent inlet to keep manganese and iron in manganese iron salt solution at +2 oxidation state;

[0068] S4: Transfer the manganese iron salt solution to the mixing tank 3, and add additives into the mixing tank 3 through the additive inlet to prepare a manganese iron phosphorus mixture or a manganese iron lithium phosphorus mixture.

[0069] S5: The manganese iron phosphorus mixture or manganese iron lithium phosphorus mixture transferred from the mixing tank 3 is purified by the impurity removal device 4 and then enters the mixing storage tank 5 for testing to determine whether the mixture is qualified. If the mixture is unqualified, additives are added and the mixture is re-proportioned. The qualified manganese iron phosphorus mixture or manganese iron lithium phosphorus mixture enters the pre-concentrator 6 for preheating and concentration. The preheated and concentrated manganese iron phosphorus mixture or manganese iron lithium phosphorus mixture is fed into the synthesis furnace 8 for heating and reaction to generate manganese iron lithium cathode material precursor powder.

[0070] S6: The precursor powder of lithium manganese iron phosphate cathode material is processed sequentially through cooler 9, crusher 10, demagnetizer 11, screening machine 12, silo 13 and packaging machine 14, and then transferred to finished product warehouse.

[0071] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0072] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0073] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A production equipment for a lithium manganese iron phosphate cathode material precursor, characterized in that, include: Iron dissolution reactor used to generate iron salt solutions; A manganese dissolving reactor is used to mix an iron salt solution, a manganese source, and a reducing agent to generate a manganese-iron salt solution. The inlet of the manganese dissolving reactor is connected to the outlet of the iron dissolving reactor. A reducing agent is added to generate a mixed solution in which manganese and iron retain a +2 valence. A mixing vessel for mixing manganese iron salt solution with additives to generate a mixed solution, wherein the inlet of the mixing vessel is connected to the outlet of the manganese dissolution reaction vessel, and the additive is a phosphorus source and a lithium source, or the additive is phosphoric acid; A synthesis furnace for producing lithium manganese iron phosphate cathode material precursors, wherein the feed inlet of the synthesis furnace is connected to the discharge outlet of the liquid preparation vessel; A pre-concentrator, comprising a Venturi structure and a gas-liquid separation structure, wherein the inlet of the Venturi structure is connected to the liquid preparation vessel, the outlet is connected to the inlet of the gas-liquid separation structure, the negative pressure suction port is connected to the high-temperature flue gas channel of the synthesis furnace, and the liquid outlet of the gas-liquid separation structure is connected to the synthesis furnace. The liquid preparation vessel is connected to the top of the inner cavity of the synthesis furnace via an atomizing device, which is detachably mounted on the synthesis furnace; the gas outlet of the gas-liquid separation structure is connected to a hydrochloric acid storage tank for storing hydrochloric acid via an absorption tower, and the hydrochloric acid storage tank is connected to the hydrochloric acid inlet of the iron dissolution reactor.

2. The production equipment for the lithium manganese iron phosphate cathode material precursor according to claim 1, characterized in that, The production equipment for the lithium manganese iron phosphate cathode material precursor also includes a purification device, which is located between the iron dissolution reactor and the synthesis furnace. The purification device is a solid-liquid separator.

3. The production equipment for the lithium manganese iron phosphate cathode material precursor according to claim 1, characterized in that, The atomizing device is connected to the liquid preparation vessel, the demineralized water supply pipeline, and the high-pressure protective gas supply pipeline via valves.

4. The production equipment for the lithium manganese iron phosphate cathode material precursor according to claim 3, characterized in that, The synthesis furnace includes a furnace body and burners for ejecting hot gas streams, the burners being disposed on the furnace body.

5. The production equipment for the lithium manganese iron phosphate cathode material precursor according to claim 1, characterized in that, The production equipment for the lithium manganese iron phosphate cathode material precursor also includes a solution preparation tank. The inlet of the solution preparation tank is connected to the solution preparation vessel, and the outlet is connected to the synthesis furnace. The solution preparation tank is provided with an inlet for supplying the additive.

6. The production equipment for the lithium manganese iron phosphate cathode material precursor according to claim 1, characterized in that, The bottom of the synthesis furnace is equipped with a cooler for cooling the precursor powder of lithium manganese iron phosphate cathode material, and the inlet of the cooler is connected to the outlet of the synthesis furnace.

7. The production equipment for the lithium manganese iron phosphate cathode material precursor according to claim 6, characterized in that, The production equipment for the lithium manganese iron phosphate cathode material precursor also includes a processing unit for processing the lithium manganese iron phosphate cathode material precursor powder. The processing unit includes a crusher, a demagnetizer, a screening machine, a silo, and a packaging machine arranged in sequence. The feed inlet of the crusher is connected to the discharge outlet of the cooler.

8. A method for producing a precursor of lithium manganese iron phosphate cathode material, characterized in that, The production equipment for the lithium manganese iron phosphate cathode material precursor as described in any one of claims 1-7 includes the following steps: S1: Hydrochloric acid is added to the iron dissolving reactor through the hydrochloric acid inlet, and an iron source is added to the iron dissolving reactor through the iron source inlet. The iron source reacts with the hydrochloric acid to generate an iron salt solution, which is then transferred to the manganese dissolving reactor. S2: Add manganese source into manganese dissolution reactor through manganese source inlet to generate manganese iron salt solution; S3: Add a reducing agent into the manganese dissolution reactor through the reducing agent inlet to keep the manganese and iron salt solutions in a +2 oxidation state. The reducing agent is at least one of citric acid, oxalic acid, tartaric acid, formic acid, and hydroxylamine hydrochloride. S4: Transfer the manganese iron salt solution to the mixing tank, add the additive into the mixing tank through the additive inlet, and prepare a manganese iron phosphorus mixture or a manganese iron lithium phosphorus mixture. S5: A mixture of manganese iron phosphorus or manganese iron lithium phosphorus is fed into a synthesis furnace for heating, and the reaction produces ferrous manganese pyrophosphate powder or lithium manganese iron phosphate powder. The ferrous manganese pyrophosphate powder or lithium manganese iron phosphate powder is a precursor powder for lithium manganese iron phosphate cathode material.

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