Device and process for producing and preparing manganese slurry from battery-grade manganous-manganic oxide

Abstract

The invention discloses a process for producing and preparing manganese slurry from battery-grade manganous-manganic oxide, which comprises the following steps: S1, preparing pure water, adding a certain amount of alkali liquor into the pure water, and regulating the pH value of the water to be weakly alkaline; s2, wet grinding: adding manganese sheets and the alkali liquor prepared in the step S1 into a vertical ball mill for wet grinding, and adjusting the rotating speed of the grinding machine through frequency conversion to avoid continuous high-rotating-speed grinding; and S3, slurry discharging: after wet milling of the vertical ball mill is completed, low-temperature pure water is introduced, and the manganese slurry is diluted while the temperature of the manganese slurry is reduced. According to the device and the process for producing and preparing the manganese slurry from the battery-grade manganous-manganic oxide, a certain amount of alkali liquor is added into wet-milled pure water to regulate and control the pH value of water to be alkalescent so as to slow down the hydrolysis rate of metal manganese, the property that the chemical property of manganese is relatively stable under the alkaline condition is utilized, and nitrogen is matched to separate oxygen, so that the manganese slurry is prepared. The manganese slurry is not easy to oxidize in the wet grinding process, does not deteriorate, is normal in color, and does not affect the quality of a manganous-manganic oxide product.

Description

Technical Field

[0001] The present invention relates to the technical field of a method for producing battery-grade manganese manganese tetroxide, in particular to a device and a process for producing manganese slurry from battery-grade manganese manganese tetroxide. Background Art

[0002] In recent years, with the development of green industries such as new energy vehicles, lithium manganate (LiMn2O4) has attracted more and more attention as a positive electrode material for power lithium-ion batteries. Studies have shown that compared with manganese dioxide (MnO2), lithium manganate prepared from spherical manganese tetraoxide (Mn3O4) has better performance. The more mature preparation method of manganese tetraoxide is the metal manganese powder suspension oxidation method, which uses electrolytic manganese metal sheets as raw materials. The metal manganese sheets are first crushed into a suspension, and air is used as an oxidant to prepare manganese tetraoxide at a certain temperature and additive concentration.

[0003] At present, the mature processes for producing manganese tetraoxide on the market all use dry grinding of metallic manganese flakes to prepare manganese powder, and the manganese powder and pure water are slurried in a certain proportion to prepare manganese slurry. Some companies have also tried to wet-grind manganese flakes to directly slurry and prepare battery-grade manganese tetraoxide, but they all ended in failure. There is currently no mature process for wet grinding of manganese flakes to prepare manganese tetraoxide, but there are many disadvantages in dry grinding of manganese flakes. In terms of safety, the manganese powder in the dry grinding process of manganese flakes is explosive dust and is highly dangerous. There have been cases of explosions in manganese powder sites in China. The dry grinding process of manganese flakes places high requirements on dry grinding process control, equipment, monitoring systems, and working environment. The use of wet grinding process can effectively reduce safety risks and comply with the concept of safe production. In terms of the environment, manganese powder in the dry grinding process is prone to generate dust in the production and transportation links, which pollutes the environment more, and strict requirements are placed on dust removal facilities.

[0004] The wet grinding process has less dust and the pipeline transportation link is closed, which is not easy to pollute the surrounding environment and equipment facilities, and is in line with the company's clean production concept. In terms of cost, the manganese powder in the dry grinding process is explosive, and the factory building requirement is Class A, which requires independent planning and high construction cost. It has higher requirements for the material of the equipment and mill. The service life of the same material is relatively short, and the investment in equipment and facilities for processes such as manganese powder screening, demagnetization, transportation, and weighing, as well as safety facilities in explosion-related sites, is greater than that of the wet grinding process. The wet grinding pulping process is shorter than the dry grinding process and is easier to control. It can be used in the same workshop as the synthesis reactor, reducing the transportation distance and reducing costs. However, wet grinding also has disadvantages. There are dead corners in the grinder and it cannot be completely emptied. There is a phenomenon of sinking and blockage during transportation. In addition, if the slurry cooling effect is not good in summer, the material is prone to high temperature. After hydrolysis, manganese powder is easily oxidized by air under high temperature conditions, affecting product quality. This is also the reason why many companies fail to prepare battery-grade manganese tetraoxide through wet grinding. Summary of the Invention

[0005] The object of the present invention is to provide a device and process for producing manganese slurry from battery-grade manganese manganese tetroxide to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions: A process for producing battery-grade manganese manganese tetroxide and preparing manganese slurry, comprising the following steps: S1, preparing pure water by adding a certain amount of alkali solution to the pure water to adjust the pH value of the water to be weakly alkaline; S2, wet grinding, adding manganese flakes and the alkali solution prepared in S1 into a vertical ball mill for wet grinding, and adjusting the grinding machine speed by frequency conversion to avoid continuous high-speed grinding; S3, slurry discharge, after the vertical ball mill is wet-milled, low-temperature pure water is introduced to reduce the temperature of the manganese slurry and dilute the manganese slurry; S4, circulating slurry discharge, the manganese slurry discharged from the vertical ball mill is divided into two paths, one path is circulated by a circulating pump to promote the discharge of manganese slurry, and the other path is introduced into the reactor; S5, vertical ball mill configuration, nitrogen is introduced into the vertical ball mill, and an induced draft fan is connected to the top to exhaust the gas. A small amount of nitrogen is introduced for protection during the grinding process, and the hydrogen in the mill is exhausted through the induced draft fan; S6, cleaning the vertical ball mill. After the manganese slurry is drained, rinse it with pure water at least twice to ensure that it is clean. All the water used for cleaning is discharged into the reactor; S7, aging and solid-liquid separation, after the manganese slurry is generated by precipitation reaction, the manganese and the mother liquor are separated by centrifugal separation equipment, and the mother liquor is refluxed to prepare an ammonium salt solution for catalytic oxidation; S8, washing and wastewater recovery, the manganese separated in S7 is washed, and the wastewater is recycled and reused in the washing process or wet grinding, and the manganese is dried and packaged into products.

[0007] As a further solution of the present invention: adjusting the pH of pure water: first use 8 mol / L alkali solution to adjust the pH of pure water to between 7.0-8.0.

[0008] As a further solution of the present invention: weak alkaline pure water with adjusted pH value is added to the vertical ball mill, the frequency of the grinder is adjusted to 15 Hz, a small amount of nitrogen is introduced into the grinder, and manganese flakes are evenly added at a feeding rate of 15-25 kg / min. The single amount of manganese flakes added is 375-500 kg. After the feeding is completed, the timing is started, and the speed frequency of the grinder is adjusted to 40 Hz. After grinding for 20 minutes, the speed frequency is adjusted to 20 Hz, after grinding for 25 minutes, the speed frequency is adjusted to 40 Hz, after grinding for 45 minutes, the speed frequency is adjusted to 20 Hz, after grinding for 50 minutes, the speed frequency is adjusted to 40 Hz, after grinding for 60 minutes, 80 L of 15-20 ° C cold pure water is added, and after grinding for 70 minutes, 80 L of 15-20 ° C cold pure water is added to reduce the temperature of the manganese slurry and dilute the manganese slurry. When the grinding is completed for 75 minutes, the mill discharge valve is opened and the mill is not stopped.

[0009] As a further solution of the present invention: the manganese slurry enters the manganese slurry buffer tank through the filter screen and starts circulating discharge. The manganese slurry is divided into two paths. Part of the manganese slurry is circulated back and enters the dead corner of the mill from the top to flush the dead corner of the mill. Part of the manganese slurry is transported to the manganese slurry reactor until all the primary manganese slurry with a solid content of 50% (the mass ratio of manganese powder to water is 1:1) is discharged into the manganese slurry reactor. At this time, the manganese slurry temperature is required to be lower than 50°C.

[0010] As a further solution of the present invention: before the manganese slurry is injected into the reactor, the reactor agitator is first turned on with a stirring frequency of 40 Hz, 80 L of pure water is first added, and then all the primary manganese slurry is injected into the reactor to prevent the manganese slurry from sinking to the bottom and not being able to be stirred, and then 200 L of pure water is used to recirculate and rinse the grinder tank. After the grinder is operated at 40 Hz for 5 minutes, the cleaning water is discharged and transported to the reactor. Finally, 85 L of pure water is injected into the grinder, and the grinder is operated at 40 Hz for 5 minutes. The cleaned pure water is still transported to the manganese slurry reaction tank, the pH value in the reactor is measured, and appropriate alkali solution is added to adjust the pH value again within the range of 7.0-8.0 to inhibit the hydrolysis and oxidation of metallic manganese. At this time, the solid content of the finished manganese slurry in the manganese slurry reaction tank is 33% (that is, the mass ratio of manganese powder to water is 1:2), and the manganese slurry temperature is lower than 40°C, which is convenient for peristaltic pump transportation and feeding.

[0011] A device for producing manganese slurry from battery-grade manganese manganese tetroxide comprises a vertical ball mill, a reactor, a mixing tank A and a mixing tank B. The vertical ball mill is provided with a nitrogen input pipeline, an induced draft fan exhaust pipeline, a manganese flake addition pipeline, a weakly alkaline pure water addition pipeline and a manganese slurry output pipeline. The weakly alkaline pure water addition pipeline is connected to the mixing tank A, which is connected to a pure water pipeline and an alkaline solution pipeline. The manganese slurry output pipeline is connected to the input end of the reactor.

[0012] As a further solution of the present invention: the manganese slurry output pipeline is also connected to a circulation pipeline, the other end of the circulation pipeline is connected to the weak alkaline pure water addition pipeline, and a circulation pump is provided on the circulation pipeline.

[0013] As a further solution of the present invention: the reactor is provided with a dosing pipeline, a gas exhaust pipeline, a material discharge pipeline and a compressed air input pipeline, and the dosing pipeline is connected to the mixing tank b.

[0014] As a further solution of the present invention: the mixing tank b is connected to the pure water tank and the ammonium chloride tank.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The device and process for producing manganese slurry from battery-grade trimanganese tetraoxide slows down the hydrolysis rate of metallic manganese by adding a certain amount of alkali solution to wet-grinding pure water to adjust the pH value of the water to a weak alkaline state. The device utilizes the relatively stable chemical properties of manganese under alkaline conditions, and uses nitrogen to separate oxygen. This prevents the manganese slurry from being easily oxidized during the wet-grinding process, prevents the manganese slurry from deteriorating, maintains its normal color, and does not affect the quality of the trimanganese tetraoxide product.

[0016] 2. The device and process for preparing manganese slurry from battery-grade manganese manganese tetroxide discharge the solid material in the vertical ball mill through non-stop unloading, circulating discharge and pure water cleaning. The final solid content of the manganese slurry is 33%, which not only prevents the solid material from oxidizing in the vertical ball mill and affecting the product quality, but also improves the fluidity of the manganese slurry and maintains smooth material transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A process flow chart for preparing manganese slurry for producing battery-grade manganese tetraoxide; Figure 2 The present invention is a schematic structural diagram of a device for producing manganese slurry for battery-grade manganese tetraoxide.

[0018] In the figure: 1. Vertical ball mill; 2. Reactor; 3. Feeding line; 4. Pure water line; 5. Alkali solution line; 6. Mixing tank a; 7. Circulation line; 8. Gas exhaust line; 9. Compressed air input line; 10. Dosing line; 11. Mixing tank b; 12. Pure water tank; 13. Ammonium chloride tank. DETAILED DESCRIPTION

[0019] See also Figures 1-2 In an embodiment of the present invention, a process for producing battery-grade manganese manganese tetroxide to prepare manganese slurry comprises the following steps: S1, preparing pure water by adding a certain amount of alkali solution to the pure water to adjust the pH value of the water to be weakly alkaline; S2, wet grinding, adding manganese flakes and the alkali solution prepared in S1 into a vertical ball mill for wet grinding, and adjusting the grinding machine speed by frequency conversion to avoid continuous high-speed grinding; S3, slurry discharge, after the vertical ball mill is wet-milled, low-temperature pure water is introduced to reduce the temperature of the manganese slurry and dilute the manganese slurry; S4, circulating slurry discharge, the manganese slurry discharged from the vertical ball mill is divided into two paths, one path is circulated by a circulating pump to promote the discharge of manganese slurry, and the other path is introduced into the reactor; S5, vertical ball mill configuration, nitrogen is introduced into the vertical ball mill, and an induced draft fan is connected to the top to exhaust the gas. A small amount of nitrogen is introduced for protection during the grinding process, and the hydrogen in the mill is exhausted through the induced draft fan; S6, cleaning the vertical ball mill. After the manganese slurry is drained, rinse it with pure water at least twice to ensure that it is clean. All the water used for cleaning is discharged into the reactor; S7, aging and solid-liquid separation, after the manganese slurry is generated by precipitation reaction, the manganese and the mother liquor are separated by centrifugal separation equipment, and the mother liquor is refluxed to prepare an ammonium salt solution for catalytic oxidation; S8, washing and wastewater recovery, the manganese separated in S7 is washed, and the wastewater is recycled and reused in the washing process or wet grinding, and the manganese is dried and packaged into products.

[0020] In a preferred embodiment, the pH of pure water is adjusted by first adjusting the pH of pure water to between 7.0 and 8.0 with 8 mol / L alkali solution; This patent first adds a certain amount of alkali solution to the wet-grinding pure water to adjust the pH value of the water to a weak alkaline value to slow down the hydrolysis rate of metallic manganese. Because manganese is an active metal, but under alkaline conditions, its chemical properties are relatively stable. Elemental manganese itself does not directly react with alkali. However, the pH of the aqueous solution cannot be too high, as this will affect the pH control of the catalytic oxidation reaction of battery-grade manganese tetraoxide in the preparation of manganese slurry.

[0021] In a preferred embodiment, weakly alkaline pure water with adjusted pH value is added to the vertical ball mill, the grinding frequency is adjusted to 15 Hz, a small amount of nitrogen is introduced into the grinder, and manganese flakes are evenly added at a feeding rate of 15-25 kg / min. The single amount of manganese flakes added is 375-500 kg. After the feeding is completed, the timing is started, and the grinding speed frequency is adjusted to 40 Hz. After grinding for 20 minutes, the speed frequency is adjusted to 20 Hz. After grinding for 25 minutes, the speed frequency is adjusted to 40 Hz. After grinding for 45 minutes, the speed frequency is adjusted to 20 Hz. After grinding for 50 minutes, the speed frequency is adjusted to 40 Hz. After grinding for 60 minutes, 80 L of 15-20 ° C cold pure water is added. After grinding for 70 minutes, 80 L of 15-20 ° C cold pure water is added to reduce the temperature of the manganese slurry and dilute the manganese slurry. When the grinding is completed for 75 minutes, the discharge valve of the mill is opened without stopping the mill. The grinding process of the vertical ball mill is regulated and controlled, and the speed of the grinder is adjusted by frequency conversion to avoid continuous high-speed grinding, so that the manganese powder in the manganese slurry prepared by grinding can not only meet certain particle size requirements, but also have a more uniform particle size distribution, and the manganese slurry will not be high in temperature.

[0022] In a preferred embodiment, the manganese slurry enters the manganese slurry buffer tank through a filter screen and starts circulating discharge. The manganese slurry is divided into two paths. Part of the manganese slurry is circulated back and enters the dead corner of the mill from the top to flush the mill. Part of the manganese slurry is transported to the manganese slurry reactor until all the primary manganese slurry with a solid content of 50% (the mass ratio of manganese powder to water is 1:1) is discharged into the manganese slurry reactor. At this time, the manganese slurry temperature is required to be lower than 50°C. Before discharging, a certain amount of low-temperature pure water is added to the grinder to reduce the temperature of the manganese slurry and dilute the manganese slurry to avoid the difficulty of discharging the viscous manganese slurry. The above two measures are used to achieve efficient grinding of manganese flakes, and the discharge temperature of the prepared manganese slurry is lower than 50°C. The discharging process is not easy to oxidize, ensuring that the solid content of the manganese slurry is 50%, which is convenient for transportation of the manganese slurry.

[0023] In a preferred embodiment, before the manganese slurry is injected into the reactor, the reactor agitator is first turned on with a stirring frequency of 40 Hz, 80 L of pure water is added first, and then all the primary manganese slurry is injected into the reactor to prevent the manganese slurry from sinking and not being stirred. Then, 200 L of pure water is recycled to rinse the grinder tank. After the grinder is operated at 40 Hz for 5 minutes, the cleaning water is discharged and transported to the reactor. Finally, 85 L of pure water is injected into the grinder, and the grinder is operated at 40 Hz for 5 minutes. The cleaned pure water is still transported to the manganese slurry reaction tank, the pH value in the reactor is measured, and an appropriate alkali solution is added to adjust the pH value again within the range of 7.0-8.0 to inhibit the hydrolysis and oxidation of metallic manganese. At this time, the solid content of the finished manganese slurry in the manganese slurry reaction tank is 33% (ie, the mass ratio of manganese powder to water is 1:2), and the manganese slurry temperature is lower than 40 ° C, which is convenient for peristaltic pump transportation and feeding; When discharging manganese slurry, circular discharging is used, that is, the manganese slurry coming out of the grinder is divided into two paths. After leaving the mill, part of the manganese slurry is circulated back to the grinder through the pipeline to flush the dead corners in the grinder and empty the manganese slurry in the mill as much as possible. Part of the manganese slurry is transported to the reactor through the pipeline and circulated until all the manganese slurry is emptied. After all the manganese slurry is emptied, pure water is added to the mill to rinse twice. All the water used to clean the mill is transported to the reactor, and the transportation pipeline is also cleaned, so that the manganese slurry emptying rate in the mill is ≥98%, and there is less manganese slurry remaining in the pipeline, which avoids the residual manganese slurry from being oxidized for a long time and affecting the quality of the next batch of manganese slurry. At the same time, the manganese slurry is diluted so that the solid content of the manganese slurry in the final reaction tank reaches 33%, which is convenient for feeding into the reactor through the peristaltic pump. The patented manganese slurry prepared by the innovation of the wet grinding process is used to prepare battery-grade manganese tetroxide. The manganese tetroxide product meets the industry standard requirements. The finished product is used to prepare lithium manganate batteries with qualified battery performance.

[0024] A device for producing manganese slurry from battery-grade manganese manganese tetroxide comprises a vertical ball mill 1, a reactor 2, a mixing tank a6, and a mixing tank b11. The vertical ball mill 1 is provided with a nitrogen input pipeline, an induced draft fan exhaust pipeline, a manganese flake addition pipeline, a weakly alkaline pure water addition pipeline, and a manganese slurry output pipeline. The weakly alkaline pure water addition pipeline is connected to the mixing tank a6, and the mixing tank a6 is connected to a pure water pipeline 4 and an alkali liquid pipeline 5. The manganese slurry output pipeline is connected to the input end of the reactor 2. The nitrogen input pipeline is connected to a nitrogen generator, and the alkali liquid pipeline 5 is connected to the alkali liquid tank. All pipelines are provided with valve control pipelines.

[0025] In a preferred embodiment, the manganese slurry output pipeline is also connected to a circulation pipeline 7, the other end of the circulation pipeline 7 is connected to the weak alkaline pure water addition pipeline, and a circulation pump is provided on the circulation pipeline 7, which can be a peristaltic pump.

[0026] In a preferred embodiment, the reactor 2 is provided with a dosing line 10, a gas venting line 8, a blanking line 3 and a compressed air input line 9, the dosing line 10 is connected to a mixing tank b11, and metallic manganese reacts with water and an ammonium salt in the presence of air or oxygen to generate trimanganese tetraoxide. The wet catalytic oxidation of metallic manganese powder involves preparing a suspension of manganese powder, bubbling air (or oxygen) to oxidize the metallic manganese powder therein using an ammonia salt as a catalyst, and during the reaction, the catalyst forms a complex with manganese, and the complex is unstable to generate a manganese hydroxide precipitate, which is oxidized by oxygen to obtain trimanganese tetraoxide. During the reaction, the amount of the ammonium salt is substantially unchanged, and the reaction is carried out by the action of the ammonium salt. The ammonium salt can be regarded as a catalyst, and therefore the reaction can be regarded as a catalytic oxidation process.

[0027] In a preferred embodiment, the mixing tank b11 is connected to the pure water tank 12 and the ammonium chloride tank 13 .

[0028] Process Principle (1) Process principle of preparing battery-grade manganese oxide by wet grinding of manganese metal sheets The main chemical reaction equations involved in the wet grinding of manganese metal flakes to prepare battery-grade manganese oxide are as follows: Mn+2NH4++2H2O=Mn2++2NH4OH+H2↑ Mn2++2NH4OH=Mn(OH)2↓+2NH4+ 6Mn(OH)2+O2=2Mn3O4+6H2O Manganese metal reacts with water and ammonium salt in the presence of air or oxygen to generate manganese trimanganese tetroxide. In the wet catalytic oxidation of manganese metal powder, the manganese powder is made into a suspension, and air (or oxygen) is bubbled into it using an ammonia salt as a catalyst to oxidize the manganese metal powder. During the reaction, the catalyst forms a complex with manganese, and the complex is unstable to generate manganese hydroxide precipitate. The manganese hydroxide is oxidized by oxygen to obtain manganese trimanganese tetroxide. During the reaction, the amount of ammonium salt remains basically unchanged. The reaction is enabled by the action of the ammonium salt. The ammonium salt can be regarded as a catalyst, and therefore the reaction can be regarded as a catalytic oxidation process.

[0029] (2) The main chemical reaction equations involved in the wet grinding of manganese metal flakes to prepare manganese slurry are as follows: Manganese powder hydrolysis reaction equation: Mn+2H2O=Mn(OH)2↓+H2↑ Manganese hydroxide is easily oxidized in air or oxygen to form brown manganese hydroxide, the formula is: 2Mn(OH)2+O2=2MnO(OH)2 Manganese hydroxide will generate manganese dioxide after further dehydration, the formula is: MnO(OH)2= MnO2+H2O Manganese metal flakes are very susceptible to hydrolysis in weakly acidic aqueous solutions to produce manganese hydroxide precipitates. Manganese hydroxide precipitates are very susceptible to oxidation upon contact with air to produce brown manganese metahydroxide. Manganese metahydroxide is further dehydrated to produce manganese dioxide, which forms an oxide protective film on the surface of manganese powder, causing the manganese slurry to deteriorate. When the manganese slurry is put into the catalytic oxidation synthesis reactor, it no longer reacts with the ammonium salt solution, resulting in the presence of unreacted manganese powder and manganese dioxide in the prepared manganese tetroxide, affecting the product purity. Manganese flakes are relatively chemically stable in weakly alkaline aqueous solutions and hydrolyze slowly. Weakly alkaline solutions also have a certain inhibitory effect on the hydrolysis rate of manganese flakes. Therefore, the project mainly involves adding a small amount of alkali solution to the water to adjust the pH value of the pure water to within the range of 7.0-8.0. At the same time, nitrogen protection is used to isolate the air, and cold water is used to lower the manganese slurry discharge temperature, thereby preventing high-temperature oxidation of the manganese slurry during the discharge process. In addition, the circulating discharge reduces the residual manganese slurry in the mill, improves the manganese slurry emptying rate and pipeline residue, and reduces the oxidation and deterioration of the manganese slurry, thereby ensuring the quality of the prepared manganese slurry and not affecting the quality of the manganese tetraoxide product.

[0030] Process Description The battery-grade manganese oxide process uses electrolytic manganese flakes as raw materials. The manganese flakes are first wet-ground to form a manganese slurry of a certain particle size. Air is then used as an oxidant in a catalytic oxidation reactor to react in an ammonium salt solution at a certain temperature and concentration to prepare battery-grade manganese oxide. This patent mainly innovates the first step of the manganese flake wet grinding process to ensure that the manganese slurry does not oxidize and deteriorate, meets certain particle size requirements, and has a relatively uniform particle size distribution.

[0031] Method for inhibiting the hydrolysis of manganese powder: Manganese powder is easily hydrolyzed in weakly acidic water to produce manganese hydroxide precipitate and release hydrogen at the same time. Manganese hydroxide is easily oxidized into manganese oxide when in contact with air. Manganese oxide wraps the manganese powder particles and the color of the manganese powder turns brown-yellow. In the process of suspended oxidation of metallic manganese powder to prepare manganese tetraoxide, manganese oxide is not easy to react with ammonium salt solution to produce manganese hydroxide, and is thus oxidized to manganese tetraoxide, which will cause incomplete reaction of manganese powder and the appearance of unqualified products such as high manganese content in manganese tetraoxide. In this project, a certain amount of alkali solution is added to the pure water for wet grinding to adjust the pH value of the water to weak alkalinity to inhibit the hydrolysis rate of metallic manganese. Because metallic manganese is relatively stable in weakly alkaline aqueous solution, the hydrolysis rate is the slowest. At the same time, a small amount of nitrogen is introduced into the mill for protection during the grinding process to isolate the air from reacting with the manganese hydroxide produced by hydrolysis to produce manganese oxide. In addition, nitrogen can dilute the produced hydrogen, and the hydrogen in the grinder is discharged through the induced draft fan to reduce the risk of hydrogen explosion.

[0032] Frequency conversion control of cold water cooling method: When grinding manganese flakes in a vertical ball mill, the amount of water added should not be too much. Too much water will form a water film to lubricate the manganese powder, making it difficult to grind the manganese powder into fine powder, which will result in a longer grinding time. In addition, high-speed stirring at the same frequency will cause the manganese slurry to become high temperature, water evaporation, and viscous manganese slurry. Discharging will be difficult, the discharging time is too long, and the manganese slurry is exposed to air for too long, resulting in severe oxidation of the manganese slurry. At the same time, high temperature accelerates the hydrolysis of manganese powder to produce hydrogen, which will cause the manganese slurry to explode. The patent has been adjusted through multiple processes and finally uses frequency conversion to adjust the grinding machine speed to avoid continuous high-speed grinding and control the grinding water manganese Mass ratio, thereby speeding up the grinding speed. The manganese powder in the prepared manganese slurry can not only meet certain particle size requirements (300 meshes), but also has a more uniform particle size distribution. The manganese slurry will not be high temperature. Before discharging, a certain amount of low-temperature (20°C) pure water is added to the grinder to reduce the temperature of the manganese slurry and dilute the manganese slurry to avoid the difficulty of discharging the viscous manganese slurry. The cold water cooling method is controlled by frequency conversion, and the manganese water mass ratio is controlled at the same time to achieve efficient grinding of manganese sheets. The discharge temperature of the prepared manganese slurry is lower than 50°C, and the discharging process is not easy to oxidize, ensuring that the solid content in the manganese slurry is 50%, which is convenient for manganese slurry transportation.

[0033] Circular discharging and efficient emptying method: The disadvantage of the vertical ball mill is that the manganese slurry cannot be completely emptied. The pilot production line of manganese oxide belongs to intermittent production. The manganese slurry cannot be emptied. If it is left for a long time, the residual manganese slurry will oxidize, affecting the quality of the next batch of manganese slurry. The project uses circular discharging for manganese slurry, that is, the manganese slurry coming out of the vertical ball mill is divided into two paths. Part of the manganese slurry is returned to the grinder through a pipeline after leaving the mill to flush the dead corners in the grinder, and the manganese slurry in the mill is emptied as much as possible. Part of the manganese slurry is transported to the manganese slurry reaction tank through a pipeline, and the circulated discharge is carried out until all the manganese slurry is emptied. After all the manganese slurry is emptied, pure water is added to the mill to rinse it twice. The water used to clean the mill is all transported to the reaction tank, and the transportation pipeline is also cleaned, so as to achieve a manganese slurry emptying rate of ≥98% in the mill, and there is less residual manganese slurry in the pipeline, which avoids the residual manganese slurry from oxidizing for a long time and affecting the quality of the next batch of manganese slurry. At the same time, the manganese slurry is diluted so that the solid content of the manganese slurry in the final reaction tank reaches 33%, which is convenient for feeding into the reactor through a peristaltic pump.

[0034] Manganese metal powder wet grinding solution This patent uses a 1000L vertical ball mill to wet-grind metallic manganese flakes to prepare manganese slurry. During wet grinding, manganese flakes and pure water are added in a mass ratio of 5:3. The 300-mesh screening rate of the ground manganese powder particles reaches more than 98%.

[0035] The specific process operation plan is as follows: Adjust the pH value of pure water: first use 8mol / L alkali solution to adjust the pH value of pure water to between 7.0-8.0. Before grinding, run the ball mill at 30Hz for 10 minutes, then drain all the maintenance pure water in the mill (the mill does not stop), and then add 225L of weak alkaline pure water with adjusted pH value to the ball mill, adjust the frequency of the grinder to 15Hz, introduce a small amount of nitrogen into the grinder, and evenly add manganese flakes at a feeding rate of 15-25kg / min. The amount of manganese flakes added at a time is 375-500kg. Start timing after the feeding is completed, adjust the speed frequency of the grinder to 40Hz, grind for 20min, adjust the speed frequency to 20Hz, grind for 25min, adjust the speed frequency to 40Hz, grind for 45min, and adjust the speed frequency to 20Hz. After 50 minutes, the speed frequency is adjusted to 40Hz. After grinding for 60 minutes, 80L of cold pure water at 15-20℃ is added. After grinding for 70 minutes, 80L of cold pure water at 15-20℃ is added to reduce the temperature of the manganese slurry and dilute the manganese slurry. When grinding for 75 minutes, the mill discharge valve is opened (the mill does not stop), and the manganese slurry enters the manganese slurry buffer tank through the filter screen and starts circulating discharge. The manganese slurry is divided into two paths. Part of the manganese slurry is circulated back and enters from the top of the mill to flush the dead corners of the mill. Part of the manganese slurry is transported to the manganese slurry reaction tank until all the primary manganese slurry with a solid content of 50% (the mass ratio of manganese powder to water is 1:1) is discharged into the manganese slurry reaction tank. At this time, the manganese slurry temperature is required to be lower than 50℃.

[0036] Before the manganese slurry is injected into the reaction tank, the agitator of the manganese slurry reaction tank is first turned on with a stirring frequency of 40Hz. 80L of pure water is first added, and then all the primary manganese slurry is injected into the manganese slurry reaction tank to prevent the manganese slurry from sinking to the bottom and not being able to be stirred. Then 200L of pure water is used to recirculate and rinse the grinder tank. After the grinder runs at 40Hz for 5 minutes, the cleaning water is discharged and transported to the manganese slurry reaction tank. Finally, 85L of pure water is injected into the grinder, and the grinder runs at 40Hz for 5 minutes. The cleaning pure water is still transported to the manganese slurry reaction tank. The pH value in the manganese slurry reaction tank is measured, and appropriate alkali solution is added to adjust the pH value again within the range of 7.0-8.0 to inhibit the hydrolysis and oxidation of metallic manganese. At this time, the solid content of the finished manganese slurry in the manganese slurry reaction tank is 33% (that is, the mass ratio of manganese powder to water is 1:2), and the manganese slurry temperature is lower than 40°C, which is convenient for peristaltic pump transportation and feeding.

[0037] Patent achievements (1) Achieved the technology of preparing battery-grade manganese oxide by wet grinding of manganese metal sheets; (2) The discharge temperature of manganese slurry during wet grinding of manganese flakes is ≤50℃, which is not easy to oxidize, the manganese slurry does not deteriorate, the color of the manganese slurry is normal, and the quality of manganese tetraoxide products is not affected; (3) The manganese slurry emptying rate of the vertical ball mill is ≥98%, the final manganese slurry solid content is 33%, and the peristaltic pump conveys the material smoothly without clogging; (4) Manganese tetraoxide products comply with the industry standard for manganese tetraoxide for lithium batteries (YB / T 4736-2019); (5) Battery-grade manganese dioxide products are sent out to prepare lithium manganate batteries, and the products are qualified in testing and meet market demand.

[0038] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0039] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A process for producing battery-grade manganese manganese tetroxide to prepare manganese slurry, characterized in that: The following steps are included: S1, preparing pure water by adding a certain amount of alkali solution to the pure water to adjust the pH value of the water to be weakly alkaline; S2, wet grinding, adding manganese flakes and the alkali solution prepared in S1 into a vertical ball mill for wet grinding, and adjusting the grinding machine speed by frequency conversion to avoid continuous high-speed grinding; S3, slurry discharge, after the vertical ball mill is wet-milled, low-temperature pure water is introduced to reduce the temperature of the manganese slurry and dilute the manganese slurry; S4, circulating slurry discharge, the manganese slurry discharged from the vertical ball mill is divided into two paths, one path is circulated by a circulating pump to promote the discharge of manganese slurry, and the other path is introduced into the reactor; S5, vertical ball mill configuration, nitrogen is introduced into the vertical ball mill, and an induced draft fan is connected to the top to exhaust the gas. A small amount of nitrogen is introduced for protection during the grinding process, and the hydrogen in the mill is exhausted through the induced draft fan; S6, cleaning the vertical ball mill. After the manganese slurry is drained, rinse it with pure water at least twice to ensure that it is clean. All the water used for cleaning is discharged into the reactor; S7, aging and solid-liquid separation, after the manganese slurry is generated by precipitation reaction, the manganese and the mother liquor are separated by centrifugal separation equipment, and the mother liquor is refluxed to prepare an ammonium salt solution for catalytic oxidation; S8, washing and wastewater recovery, the manganese separated in S7 is washed, and the wastewater is recycled and reused in the washing process or wet grinding, and the manganese is dried and packaged into products.

2. The process for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 1, characterized in that: Adjust the pH of pure water: first use 8mol / L alkali solution to adjust the pH of pure water to between 7.0-8.

0.

3. The process for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 1, characterized in that: Add weakly alkaline pure water with adjusted pH value to the vertical ball mill, adjust the grinding machine frequency to 15Hz, introduce a small amount of nitrogen into the grinder, and evenly add manganese flakes at a feeding rate of 15-25kg / min. The single manganese flake addition amount is 375-500kg. Start timing after the feeding is completed, adjust the grinding machine speed frequency to 40Hz, grind for 20 minutes, adjust the speed frequency to 20Hz, grind for 25 minutes, adjust the speed frequency to 40Hz, grind for 45 minutes, adjust the speed frequency to 20Hz, grind for 50 minutes, and add 80L of 15-20℃ cold pure water after grinding for 60 minutes. Add 80L of 15-20℃ cold pure water after grinding for 70 minutes to reduce the temperature of the manganese slurry and dilute the manganese slurry. Open the mill discharge valve when grinding for 75 minutes, and the mill does not stop.

4. The process for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 1, characterized in that: The manganese slurry passes through the filter and enters the manganese slurry buffer tank, where it begins to circulate and discharge. The manganese slurry is divided into two routes. One part of the manganese slurry circulates back and enters from the top of the mill to flush the dead corners of the mill, while the other part of the manganese slurry is transported to the manganese slurry reactor until all the primary manganese slurry with a solid content of 50% (the mass ratio of manganese powder to water is 1:1) is discharged into the manganese slurry reactor. At this time, the temperature of the manganese slurry is required to be lower than 50°C.

5. A process for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 1 or 4, characterized in that: Before the manganese slurry is injected into the reactor, the reactor agitator is first turned on with a stirring frequency of 40Hz. 80L of pure water is first added, and then all the primary manganese slurry is injected into the reactor to prevent the manganese slurry from sinking to the bottom and being unable to be stirred. Then 200L of pure water is used to recirculate and rinse the grinder tank. After the grinder runs at 40Hz for 5 minutes, the cleaning water is discharged and transported to the reactor. Finally, 85L of pure water is injected into the grinder, and the grinder runs at 40Hz for 5 minutes. The cleaning pure water is still transported to the manganese slurry reaction tank. The pH value in the reactor is measured, and appropriate alkali solution is added to adjust the pH value again within the range of 7.0-8.0 to inhibit the hydrolysis and oxidation of metallic manganese. At this time, the solid content of the finished manganese slurry in the manganese slurry reaction tank is 33% (that is, the mass ratio of manganese powder to water is 1:2), and the manganese slurry temperature is lower than 40°C, which is convenient for peristaltic pump transportation and feeding.

6. A device for producing battery-grade manganese manganese tetroxide to prepare manganese slurry, characterized in that: The device for producing battery-grade manganese tetraoxide according to claims 1-5 comprises a vertical ball mill (1), a reactor (2), a mixing tank a (6) and a mixing tank b (11), wherein the vertical ball mill (1) is provided with a nitrogen input pipeline, an induced draft fan exhaust pipeline, a manganese flake addition pipeline, a weak alkaline pure water addition pipeline and a manganese slurry output pipeline, the weak alkaline pure water addition pipeline is connected to the mixing tank a (6), the mixing tank a (6) is connected to a pure water pipeline (4) and an alkaline solution pipeline (5), and the manganese slurry output pipeline is connected to the input end of the reactor (2).

7. The device for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 6, characterized in that: The manganese slurry output pipeline is also connected to a circulation pipeline (7), the other end of the circulation pipeline (7) is connected to a weak alkaline pure water addition pipeline, and a circulation pump is provided on the circulation pipeline (7).

8. The device for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 6, characterized in that: The reactor (2) is provided with a dosing pipeline (10), a gas exhaust pipeline (8), a material discharge pipeline (3) and a compressed air input pipeline (9), and the dosing pipeline (10) is connected to the mixing tank b (11).

9. The device for producing battery-grade manganese manganese tetroxide and preparing manganese slurry according to claim 6, characterized in that: The mixing tank b (11) is connected to the pure water tank (12) and the ammonium chloride tank (13).

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