Preparation method of cobalt carbonate for cobalt powder with small apparent density

Abstract

The invention provides a preparation method of cobalt carbonate for cobalt powder with small apparent density, which comprises the following steps: by taking soluble cobalt salt as a raw material and ammonium bicarbonate as a precipitator, adding a soluble cobalt salt solution and an ammonium bicarbonate solution into a reaction kettle under mild reaction conditions to obtain cobalt carbonate slurry, and filtering, washing and drying the slurry to prepare the cobalt carbonate for the cobalt powder with small apparent density. According to the cobalt carbonate prepared by the method, mild reaction conditions are adopted, the motion state of a reaction system is regulated and controlled by controlling the volume ratio relation of a reaction solvent and a reaction kettle, and the mixing degree and mass transfer rate of reactants in a solution can be controlled, so that the growth rate and direction of crystals are influenced, and a hollow loose soft agglomeration structure is obtained; due to the loose structure, large specific surface area, large washing contact area, easiness in washing, good dehydration property, low impurity content, small loose ratio and controllable particle size, the cobalt powder can meet the requirements of preparing cobalt powder; in addition, the method for preparing the cobalt carbonate with the small apparent density is short in reaction time, simple and convenient to operate, controllable in process, simple in post-treatment, low in moisture content and short in drying time, and the production efficiency is effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of material preparation, and in particular relates to a method for preparing cobalt carbonate for Komatsubi cobalt powder. Background Art

[0002] Cobalt and its compounds are widely used in battery materials, alloys, catalysts, binders, magnetic materials and other fields due to their unique physical and chemical properties. Among them, cobalt powder, as a binder, is an important raw material for the production of cemented carbide. With the rapid development of industry, the amount of cobalt used has increased year by year, and the performance requirements of cobalt products have also become higher and higher, becoming a hot topic of research. Cobalt carbonate is the most widely used raw material for preparing cobalt powder in the industry. Cobalt powder is prepared by hydrogen reduction. Studies have shown that the morphology, particle size and particle size distribution of cobalt powder are highly dependent on and inherited from the precursor, so cobalt carbonate powder is required to have a smaller apparent density and a smaller particle size. The particle size, morphology and apparent density of cobalt powder can be controlled by controlling the synthesis of the precursor.

[0003] At present, the main difficulty of using wet coprecipitation synthesis process to prepare cobalt carbonate for Komatsubi cobalt powder is that the cobalt carbonate prepared by the existing technology has a dense structure, poor regularity, high impurity content in the product, poor dehydration, high water content in the product, long drying time, low production efficiency, long and complicated process flow, increased processing costs, high temperature conditions, which easily lead to violent local reactions and uneven morphology, the use of additives to introduce more impurity ions while increasing the cost of impurity removal, high cobalt content in the mother liquor, large cobalt loss, and low product yield, which cannot meet the needs of industrial production. Therefore, it is necessary to design a process that can improve the above technical problems and shortcomings. Summary of the invention

[0004] The invention aims to provide a method for preparing cobalt carbonate for Komatsubi cobalt powder, which has the advantages of short process flow, simple operation, mild reaction conditions and controllable process.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: The method for preparing cobalt carbonate for Komatsubi cobalt powder of the present invention is to use ammonium bicarbonate solution as base liquid, heat it to the target reaction temperature, and then add soluble cobalt salt solution and ammonium bicarbonate solution into a reaction kettle in parallel under stirring to obtain the target cobalt carbonate. Specifically, the method comprises the following steps: S1. Prepare a soluble cobalt salt solution and an ammonium bicarbonate solution with deionized water respectively; The soluble cobalt salt is any one or a mixture of cobalt chloride, cobalt sulfate and cobalt nitrate; the concentration of the soluble cobalt salt solution is 1.69-2.54 mol / L, and the concentration of the ammonium bicarbonate solution is 2.78-3.67 mol / L.

[0006] S2, adding the ammonium bicarbonate solution obtained in step S1 into the reaction kettle as the base liquid, starting stirring, heating when the base liquid temperature reaches 30-35° C., adding the soluble cobalt salt solution and the ammonium bicarbonate solution at the same time, reacting at 30-35° C. for 1-3 hours, controlling the pH value at 7.0-9.0 during the reaction, stopping the liquid addition after the reaction is completed, and aging for 1-2 hours to obtain the cobalt carbonate slurry; The volume of the base liquid added is 1 / 3-2 / 5 of the volume of the reactor, the concentration of the ammonium bicarbonate base liquid is 2.78-3.67 mol / L, the flow rate of the soluble cobalt salt solution is 30-60 L / h, and the flow rate of the ammonium carbonate is 10-30 L / h; the stirring speed is 300-500 r / min.

[0007] S3, filtering, washing and drying the cobalt carbonate slurry in step S2 to obtain cobalt carbonate for Komatsubi cobalt powder. The cobalt carbonate slurry is centrifugally filtered and washed. Due to its loose and porous structure, it is easy to dehydrate and has good fluidity during the filtering and washing process, which is beneficial for later drying. The washing water temperature is 40-60°C, the drying temperature is 80-100°C, and the drying time is 4-8h. In addition, during the washing process, due to its loose and porous structure, the washing water can be fully contacted, the washing water amount is reduced, and the impurity content of the cobalt carbonate after washing is low, which effectively improves the production efficiency.

[0008] The present invention has the following advantages and beneficial effects: 1. The present invention provides a method for preparing cobalt carbonate for Komatsubi cobalt powder. The cobalt carbonate prepared by the method adopts a one-step synthesis method, which has a short process flow, is easy to operate, has good reproducibility, and can be suitable for large-scale production.

[0009] 2. The method provided by the present invention has short reaction time and aging time, and can effectively improve production efficiency. In addition, due to the mild reaction conditions, the obtained cobalt carbonate has good morphology uniformity, stable product quality, and small product bulk ratio and particle size, which has certain advantages for preparing small bulk ratio cobalt powder.

[0010] 3. The present invention provides a method for preparing cobalt carbonate for Komatsubi cobalt powder. No additives are added during the synthesis process, which reduces the risk of introducing more impurity ions and also reduces the cost of impurity removal and raw materials.

[0011] 4. The preparation method of the present invention is conducive to washing due to its loose and porous structure, requiring less washing water, good dehydration performance and low moisture content of the product, easy feeding and high drying efficiency during drying, and simple post-treatment; due to its special structure, the contact area with the washing water during the washing process is large, which is conducive to the removal of impurities. The washed product has low impurity content and high purity, low cobalt content in the mother liquor, and high direct product yield.

[0012] 5. The preparation method of the present invention controls the motion state of the reaction system by controlling the volume ratio of the reaction solvent and the reactor, and can control the mixing degree and mass transfer rate of the reactants in the solution, thereby affecting the rate and direction of crystal growth; at the same time, by controlling the bottom liquid concentration and the liquid inlet rate, the number of seed crystals is accurately controlled, the growth rate and size of the crystal are regulated, and the high selectivity and accuracy of the material deposition crystal surface are further achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a scanning electron microscope (SEM) image of cobalt carbonate used to prepare the Komatsubi cobalt powder in Example 1.

[0014] Figure 2 This is a scanning electron microscope (SEM) image of cobalt carbonate used to prepare the Komatsubi cobalt powder in Example 2.

[0015] Figure 3 The scanning electron microscope (SEM) image of cobalt carbonate prepared for Comparative Example 1.

[0016] Figure 4 This is the diffraction pattern of cobalt carbonate used to prepare the Komatsubi cobalt powder in Example 1. DETAILED DESCRIPTION

[0017] In order to facilitate a better understanding of the present invention, the present invention is described more fully below in conjunction with the examples and drawings. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. After reading the relevant content of the present invention, various modifications of equivalent forms applied by researchers related to this field all belong to the scope defined by the appended claims of this application, and the illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0018] Example 1 In a 400L reactor, 130L of 2.78mol / L ammonium carbonate solution was added to the reactor as the bottom liquid, stirring was started, and the speed was 400r / min. When the temperature of the bottom liquid rose to 30±1°C, the prepared 1.69mol / L cobalt salt solution and 2.78mol / L ammonium bicarbonate solution were added to the reactor at the rates of 60L / h and 30L / h respectively. After 2h of reaction, when the pH value of the reaction process dropped to 7.0, the liquid was stopped, and the cobalt carbonate slurry was aged for 1h to obtain the cobalt carbonate slurry. The cobalt carbonate slurry was filtered and washed in a centrifuge at a speed of 300r / min and a washing water temperature of 40°C. The washed cobalt carbonate was placed in an oven at a temperature of 120°C and dried for 4h to obtain the cobalt carbonate for Komatsubi cobalt powder.

[0019] Example 2 In a 400L reactor, 160L of 3.67mol / L ammonium carbonate solution was added to the reactor as the bottom liquid, stirring was started, and the speed was 300r / min. When the temperature of the bottom liquid rose to 32±1°C, the prepared 2.29mol / L cobalt salt solution and 3.67mol / L ammonium bicarbonate solution were added to the reactor at the rates of 50L / h and 10L / h respectively. After 2h of reaction, when the pH value of the reaction process dropped to 7.0, the liquid was stopped, and the cobalt carbonate slurry was aged for 1h to obtain the cobalt carbonate slurry. The cobalt carbonate slurry was filtered and washed in a centrifuge at a speed of 400r / min and a washing water temperature of 50°C. The washed cobalt carbonate was placed in an oven at a temperature of 100°C and dried for 6h to obtain the cobalt carbonate for Komatsubi cobalt powder.

[0020] Example 3 In a 400L reactor, 160L of 3.67mol / L ammonium carbonate solution was added to the reactor as the bottom liquid, stirring was started, and the speed was 500r / min. When the temperature of the bottom liquid rose to 35±1°C, the prepared soluble cobalt salt solution with a concentration of 1.87mol / L and 3.67mol / L ammonium bicarbonate solution were added to the reactor at the rates of 35L / h and 10L / h respectively. After reacting for 3h, when the pH value of the reaction process dropped to 7.0, the liquid was stopped, and the cobalt carbonate slurry was aged for 2h to obtain the cobalt carbonate slurry. The cobalt carbonate slurry was filtered and washed in a centrifuge at a speed of 400r / min and a washing water temperature of 60°C. The washed cobalt carbonate was placed in an oven at a temperature of 90°C and dried for 8h to obtain the cobalt carbonate for Komatsubi cobalt powder.

[0021] Comparative Example 1 In a 400L reactor, 60L of 1.14mol / L ammonium carbonate solution was added to the reactor as the bottom liquid, stirring was started, and the speed was 650r / min. When the temperature of the bottom liquid rose to 44±1°C, the prepared soluble cobalt salt solution with a concentration of 1.69mol / L and 2.40mol / L ammonium bicarbonate solution were added to the reactor at the rates of 9L / h and 18L / h respectively. After 10h of reaction, when the pH value of the reaction process dropped to 7.0, the liquid was stopped, and the cobalt carbonate slurry was aged for 2h. The cobalt carbonate slurry was filtered and washed in a centrifuge at a speed of 500r / min and a washing water temperature of 60°C. The washed cobalt carbonate was placed in an oven at a temperature of 120°C and dried for 20h to obtain cobalt carbonate.

[0022] Table 1 shows the test results of cobalt carbonate samples of Examples 1-3 and Comparative Example 1, the cobalt content in the process mother liquor, and the moisture content of the cobalt carbonate after washing and dehydration.

[0023] From the results of the bulk density, D50, Na content after washing with cobalt carbonate, cobalt content in the mother liquor and moisture content after washing with cobalt carbonate prepared in Examples 1-3 and Comparative Example 1 in the table, it can be seen that, compared with Examples 1-3, the bulk density and D50 of the cobalt carbonate prepared in the comparative example are increased, the Na content after washing with cobalt carbonate is increased, the impurity content of the cobalt carbonate obtained is high, the cobalt content in the mother liquor is also increased, the cobalt loss rate is high, and the direct yield is reduced, especially the moisture content is significantly increased after washing, indicating that its dehydration is poor, it is not easy to dehydrate, and is not conducive to later drying.

[0024] Figure 1 This is a scanning electron microscope (SEM) image of cobalt carbonate used to prepare the Komatsubi cobalt powder in Example 1. Figure 2 This is a scanning electron microscope (SEM) image of cobalt carbonate used to prepare the Komatsubi cobalt powder in Example 2. Figure 3 The scanning electron microscope (SEM) image of cobalt carbonate obtained in Comparative Example 1. Compared with the comparative example, the cobalt carbonate for cobalt powder obtained in the embodiment is a hollow and loose soft agglomerated structure with large porosity, easy dehydration and easy washing of impurities. The obtained cobalt carbonate has high purity and is conducive to the later preparation of high-quality cobalt powder. However, the cobalt carbonate obtained in the comparative example has serious structural agglomeration and poor dehydration. The impurity elements are wrapped due to the adhesion and agglomeration between particles, which is not conducive to washing. The impurity content of the obtained cobalt carbonate is high, which is not conducive to the later preparation of cobalt powder. Figure 4 This is the diffraction pattern of cobalt carbonate for Komatsubi cobalt powder prepared in Example 1. Compared with the standard card of CoCO3, the main characteristic peaks of cobalt carbonate for cobalt powder prepared match well with the standard card, indicating that cobalt carbonate is obtained.

[0025] In summary, the cobalt carbonate prepared by the method adopts mild reaction conditions, and the motion state of the reaction system is regulated by controlling the volume ratio of the reaction solvent and the reactor, so as to control the mixing degree and mass transfer rate of the reactants in the solution, thereby affecting the rate and direction of crystal growth, and obtaining a hollow loose and soft agglomerated structure. Due to its loose structure, large specific surface area, large washing contact area, easy washing and good dehydration, the product has low impurity content, small loose ratio and controllable particle size, which can meet the requirements for preparing cobalt powder; in addition, the method for preparing small loose ratio cobalt carbonate has short reaction time, simple operation, controllable process, simple post-treatment, low moisture content and short drying time, which effectively improves production efficiency.

Claims

1. A method for preparing cobalt carbonate for Komatsubi cobalt powder, characterized in that: The method comprises the following steps: S1. Prepare a soluble cobalt salt solution and an ammonium bicarbonate solution with deionized water respectively; S2, adding the ammonium bicarbonate solution obtained in step S1 into the reaction kettle as the base liquid, starting stirring, heating when the base liquid temperature reaches 30-35° C., adding the soluble cobalt salt solution and the ammonium bicarbonate solution at the same time, reacting at 30-35° C. for 1-3 hours, controlling the pH value at 7.0-9.0 during the reaction, stopping the liquid addition after the reaction is completed, and aging for 1-2 hours to obtain the cobalt carbonate slurry; S3, filtering, washing and drying the cobalt carbonate slurry in step S2 to obtain cobalt carbonate for Komatsubi cobalt powder.

2. The method for preparing cobalt carbonate for Komatsubi cobalt powder according to claim 1, characterized in that: The soluble cobalt salt in S1 is any one or a mixture of cobalt chloride, cobalt sulfate and cobalt nitrate.

3. The method for preparing cobalt carbonate for Komatsubi cobalt powder according to claim 1, characterized in that: The concentration of the soluble cobalt salt solution in S1 is 1.69-2.54 mol / L, and the concentration of the ammonium bicarbonate solution is 2.78-3.67 mol / L.

4. The method for preparing cobalt carbonate for Komatsubi cobalt powder according to claim 1, characterized in that: The volume of the bottom liquid added in S2 is 1 / 3-2 / 5 of the volume of the reactor, and the concentration of the ammonium bicarbonate bottom liquid is 2.78-3.67 mol / L.

5. The method for preparing cobalt carbonate for Komatsubi cobalt powder according to claim 1, characterized in that: The flow rate of soluble cobalt salt solution in S2 is 30-60 L / h, and the flow rate of ammonium carbonate is 10-30 L / h; the stirring speed is 300-500 r / min.

6. The method for preparing cobalt carbonate for Komatsubi cobalt powder according to claim 1, characterized in that: During washing in S3, the washing water temperature is 40-60°C, the drying temperature is 80-100°C, and the drying time is 4-8h.

7. The method for preparing cobalt carbonate for Komatsubi cobalt powder according to claim 1, characterized in that: The prepared cobalt powder with small loose ratio is made of cobalt carbonate with a hollow spherical soft agglomerate structure. The indicators of cobalt carbonate are: moisture ≤1%, loose ratio <0.3g / cm 3 , Co≥47.5%, cobalt content in mother liquor≤0.15g / L, D50≤1um.

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