A preparation method of battery-grade manganese tetraoxide

Abstract

The present invention relates to the technical field of manganese tetraoxide preparation, and specifically discloses a method for preparing battery-grade manganese trioxide, comprising the following steps: 1) crushing pyrolusite and mixing it with water to form a pulp, and absorbing sulfur dioxide gas by means of multi-stage spraying of the pulp to obtain a manganese sulfate reduction solution; 2) mixing the manganese sulfate reduction solution with a buffer to obtain a manganese sulfate pre-solution, and continuously mixing the manganese sulfate pre-solution with an alkali solution, a pH regulator, and an oxidant to carry out a reaction, and introducing air during the reaction to carry out an oxidation reaction; 3) aging the slurry after the reaction in step 2) is completed, filtering the aged slurry to obtain a filter residue, and drying and demagnetizing the filter residue to obtain battery-grade manganese trioxide. The present invention can effectively reduce energy consumption, simplify the production process, and can obtain battery-grade manganese trioxide with high purification, uniform particle size, stable quality, and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of manganese tetraoxide preparation, and particularly relates to a method for preparing battery-grade manganese tetraoxide. Background Art

[0002] Manganese tetraoxide is an important precursor for lithium manganese oxide cathode materials. Battery-grade manganese tetraoxide has relatively high requirements for the contents of potassium, iron, and copper impurities. For example, according to the regulations of manganese tetraoxide for lithium batteries (YBT 4736-2019), the qualified product index requirements are that the potassium content (ω / %) is less than or equal to 0.005, the iron (ω / %) content is less than or equal to 0.005, and the copper (ω / %) content is less than or equal to 0.005. In addition, the requirements for the morphology control, tap density, particle size control, etc. of manganese tetraoxide products are also extremely strict. According to the preparation raw materials, the existing methods for preparing battery-grade manganese tetraoxide in the prior art include: manganese oxide method, manganese ore method, manganese salt method, manganese metal method, etc. Among them, the manganese oxide method is to heat high-valent manganese oxides such as manganese dioxide and manganese sesquioxide to above 950 °C for deoxidation and reduction reaction to obtain manganese tetraoxide. This method has a great influence on the conversion rate and crystal structure of the product manganese tetraoxide by the roasting time and roasting temperature, and can produce products with larger particles and smaller specific surface area, but the high-temperature roasting consumes a large amount of energy, and its practical application is limited under the background of carbon reduction. The manganese ore method starts from the raw material ore end. After the manganese ore is treated through processes such as reduction and acid leaching, a manganese salt solution is obtained, and then the manganese tetraoxide product is prepared according to the manganese salt method. Since the process of obtaining manganese salt from manganese ore is relatively complex, the impurity content is difficult to control, and the production technology requirements are relatively high. However, it starts from the raw material ore end, has low cost and high economic value, and is a research hotspot in the industry.

[0003] The Chinese patent with the publication number CN115140774A discloses a method for preparing manganese tetraoxide. It uses psilomelane as the raw material, and obtains manganese dioxide through high-temperature roasting. Then, manganese dioxide reacts with methane gas to obtain manganese tetraoxide. This method has high preparation efficiency and high product purity, but the roasting energy consumption is relatively large. The Chinese patent with the publication number CN115286041A discloses a roasting manufacturing method for high-purity manganese tetraoxide. It uses manganese salts, manganese metals, etc. as raw materials, and obtains manganese tetraoxide through high-temperature roasting, cooling, and pulverization. The manganese tetraoxide manufactured by this method has low impurity content, but also has relatively large energy consumption, which is not conducive to industrial implementation. The Chinese patent with the publication number CN 101049971 A discloses a method for preparing high-purity manganese tetraoxide using pyrolusite as the raw material. In this method, the raw material manganese ore needs to be acid-leached first and then sulfur dioxide is introduced to obtain a manganese sulfate solution. Then, the manganese sulfate solution after impurity removal and purification is extracted, and air is introduced for oxidation under alkaline conditions to obtain the product high-purity manganese tetraoxide. According to the product analysis results, the specific surface area and impurity content of the manganese tetraoxide prepared by this method do not meet the index requirements in "Manganese Tetraoxide for Lithium Batteries" (YB / T 4736~2019).

[0004] Therefore, the present invention aims to develop a method for preparing battery-grade manganese tetraoxide using pyrolusite as the raw material, with low energy consumption, high economic benefits, and meeting industry standards. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing manganese tetraoxide for batteries with low energy consumption, high purity, and stable quality.

[0006] The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0007] A method for preparing battery-grade manganese tetraoxide includes the following steps:

[0008] 1) Pulverize pyrolusite and mix it with water to form a pulp. The pulp absorbs sulfur dioxide gas by means of multi-stage spraying to obtain a manganese sulfate reduction solution; this step has low energy consumption, does not require high temperature, is conducive to reducing the comprehensive production energy consumption, and produces less waste residue, which is beneficial to environmental protection. At the same time, after process optimization, the produced solution has high purity and few impurities;

[0009] 2) Mix the manganese sulfate reduction solution with a buffer to obtain a manganese sulfate pre-solution, and continue to mix the manganese sulfate pre-solution with an alkali solution, a pH regulator, and an oxidant for reaction, and introduce air during the reaction process; this step is conducive to the dispersion of materials, makes the reaction complete, and forms a product with stable quality.

[0010] 3) Aging the slurry after the reaction in step 2), filtering the aged slurry to obtain a filter residue, and drying and demagnetizing the filter residue to obtain battery-grade manganese tetraoxide.

[0011] Further, in step 1), the pyrolusite is pretreated to have a water content of 5-12%. After the water content is controlled, the pyrolusite has good crushing effect, uniform particle size, and significantly improved pulping and reaction effects.

[0012] In step 1), the particle size of the crushed pyrolusite is 50-500 mesh. Preferably, it is 100-200 mesh.

[0013] In step 1), the liquid-solid ratio for preparing the pulp is 1-10:1. Preferably, it is 3-6:1.

[0014] Further, in step 1), the number of stages of multi-stage spray absorption is 5-15 stages. Further preferably, it is 8-12 stages. The multi-stage spray absorption adopts the form of countercurrent of the pulp and the process gas, and the finally obtained solution is a completely reacted manganese sulfate reduction solution.

[0015] In step 1), the sulfur dioxide gas is sulfur dioxide process gas, preferably processed by sulfur combustion. The volume content of sulfur dioxide in the sulfur dioxide process gas is 10-15%.

[0016] Further, in step 2), the contents of heavy metal impurities such as copper, cobalt, nickel, lead, and iron in the manganese sulfate solution should not be higher than 10 mg / L, and the contents of impurities such as potassium, sodium, calcium, and magnesium should not be higher than 50 mg / L.

[0017] If this condition is not met, impurity removal treatment is carried out before mixing the manganese sulfate reduction solution with the buffer. Before impurity removal, the concentration is adjusted to 50-200 g / L, preferably 80-160 g / L. After adding an impurity remover to the manganese sulfate reduction solution with the adjusted concentration, filtration is carried out, and the filtrate is reserved for use.

[0018] Preferably, the impurity remover includes one or more of sodium sulfide, barium sulfide, sodium hydrosulfide, and ammonium sulfide.

[0019] Preferably, a 3-5 stage impurity removal and purification process technology is adopted.

[0020] Further, in step 2), the mass ratio range of manganese sulfate to the buffer in the manganese sulfate reduction solution is 1-1000:1, preferably 300-500:1.

[0021] Further, in step 2), the volume ratio range of the manganese sulfate pre-solution to the alkali solution is 1-10:1, preferably 2-6:1; the addition rate of the alkali solution is 0.01-1 m 3 / h, preferably 0.1-0.5 m 3 / h.

[0022] In step 2), the volume ratio range of the manganese sulfate pre-liquid to the pH regulator is 10 to 100:1, preferably 30 to 70:1, and the addition rate of the pH regulator is 0.001 to 0.1 m 3 / h, more preferably 0.01 to 0.05 m 3 / h.

[0023] In step 2), the volume ratio range of the manganese sulfate pre-liquid to the oxidant is 100 to 1000:1, preferably 500 to 800:1, and the addition rate of the oxidant is 0.01 to 1 L / h, more preferably 0.1 to 0.5 L / h.

[0024] In step 2), the buffer is one or more of sulfates, nitrates, and chlorides; the pH regulator is one or more of ammonium salt solutions or ammonia water solutions; the oxidant is one or more of oxidants such as hydrogen peroxide, nitric acid, and peroxide aqueous solutions.

[0025] Further, in step 2), the amount of air blown in is 100 to 500 m 3 / h, preferably 150 to 300 m 3 / h.

[0026] Further, in step 2), the reaction pH value is 5 to 11, preferably 8 to 9.

[0027] In step 2), the reaction temperature is 1 to 200 °C, preferably 50 to 150 °C.

[0028] In step 2), the reaction time is 1 to 48 h, preferably 12 to 24 h; stirring is maintained during the reaction, and the stirring speed is 10 to 200 rpm, preferably 50 to 150 rpm.

[0029] Further, in step 3), the aging treatment time is 1 to 10 h, preferably 3 to 6 h. In this step, countercurrent fractional washing is used for filtration and washing, which can reduce the water consumption and increase the concentration of the concentrated brine. At the same time, a demagnetizer with 3000 to 15000 Gauss needs to be selected for demagnetization, which can effectively reduce the content of magnetic abnormal substances, preferably 6000 to 12000 Gauss. At the same time, the waste heat of the tail gas can be used as the heat source for drying pyrolusite.

[0030] Further, in the battery-grade manganese tetraoxide, the manganese content is higher than 70%.

[0031] Beneficial effects: For the method for preparing battery-grade manganese tetraoxide according to the present invention, after pulping pyrolusite and performing multi-stage absorption reaction with sulfur dioxide gas, the whole reaction process is rapid and thorough, without high temperature, low energy consumption, can selectively and efficiently leach manganese dioxide, and the impurity content in the obtained manganese sulfate solution after the reaction is low. After simple impurity removal and passing the detection, it can be used as the precursor solution for the production of manganese tetraoxide, without the operation steps of first forming battery-grade manganese sulfate powder and then dissolving it into the raw material liquid of manganese tetraoxide. The present invention can effectively reduce energy consumption, simplify the production process, use pyrolusite ore as the raw material, and can obtain battery-grade manganese tetraoxide with high purification, uniform particle size, stable quality and low cost. Detailed implementation mode

[0032] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0033] Example 1

[0034] For the method for preparing battery-grade manganese tetraoxide in this example, the manganese content in the pyrolusite raw material is 30%, and the water content is 15%; the preparation includes the following steps:

[0035] 1) Control the water content of pyrolusite at 10% by means of low-temperature drying; crush 2.5t of pyrolusite with 10% water content through a crushing system to make powder, control the particle size of the powder at 50 - 500 mesh, and then mix it with 12.5t of water to make pulp;

[0036] Send 300kg of sulfur to the sulfur combustion furnace for combustion to obtain sulfur dioxide process gas with a volume content of 15%, and introduce the sulfur dioxide process gas into the sulfur dioxide gas absorption tower. The heat is absorbed by the waste heat boiler to generate steam for product drying;

[0037] Absorb the sulfur dioxide process gas with the prepared pulp, adopt the ten-stage spray absorption method, and obtain the manganese sulfate reduction liquid after absorption. The tail gas is further absorbed by the pulp and then discharged up to the standard; ensure the countercurrent form of the pulp and the sulfur dioxide process gas during absorption;

[0038] 2) Transport the obtained 15t of manganese sulfate reduction liquid to the dissolution tank through a pipeline, supplement 10m 3 Condensed water is added to form a manganese sulfate reduction liquid with a concentration of 100g / L; a small amount of sodium sulfide is added to the manganese sulfate reduction liquid with a concentration of 100g / L with excessive impurities, and then it is filtered by a filter press to obtain a manganese sulfate reduction liquid that meets the impurity requirements;

[0039] Mix the manganese sulfate reduction liquid after impurity removal with 4kg of ammonium sulfate for batching to form a manganese sulfate precursor solution;

[0040] The manganese sulfate pre - liquid, sodium hydroxide solution, ammonia water, and hydrogen peroxide are respectively pumped into a reaction kettle at a volume ratio of 500:100:10:1 for a synthesis reaction. The feeding rate of the manganese sulfate pre - liquid is 5m 3 / h, the feeding rate of the alkali solution is 0.5m 3 / h, the feeding rate of the pH regulator is 0.005m 3 / h, and the feeding rate of the oxidant is 0.5L / h;

[0041] The reaction temperature is 90 °C, the pH is 10, the rotation speed is 80 rpm, and at the same time, 200m 3 / h of air is introduced for oxidation. After reacting for 20 h, a slurry is obtained;

[0042] 3) After the reaction is completed, the synthesized slurry is sent to an aging kettle for aging for 5 h to obtain an aged slurry. The aged slurry is separated by three - stage pressure filtration and washing to obtain filter residue. The washing filtrate of the filter residue is concentrated brine. The concentrated brine after washing is evaporated and crystallized. The ammonia in the concentrated brine is recovered and utilized after evaporation, the condensed water is recycled for dissolution and washing, and the crystals obtained by evaporation and crystallization are dried and packaged to obtain about 0.3 t of sulfate by - product;

[0043] The filter residue is dried and demagnetized to obtain 1 t of battery - grade manganese tetraoxide product, which is packaged and stored in the warehouse.

[0044] The relevant indicators of 1 t of battery - grade manganese tetraoxide product are shown in Table 2.

[0045] Example 2

[0046] For the preparation method of battery - grade manganese tetraoxide described in this example, the manganese content in the pyrolusite raw material is 30% and the water content is 18%; the preparation includes the following steps:

[0047] 1) The pyrolusite is dried at a low temperature to control the water content at 10%; 2.5 t of pyrolusite with a water content of 10% is crushed by a crushing system to make powder, and the particle size of the powder is controlled at 50 - 500 mesh, and then mixed with 12.5 t of water to make a slurry;

[0048] 300 kg of sulfur is sent to a sulfur combustion furnace for combustion to obtain sulfur dioxide process gas with a volume content of 15%. The sulfur dioxide process gas is introduced into a sulfur dioxide gas absorption tower, and the heat is absorbed by a waste heat boiler to generate steam for product drying;

[0049] The prepared slurry is used to absorb the sulfur dioxide process gas. The eight - stage spray absorption method is adopted. After absorption, a manganese sulfate reduction liquid is obtained, and the tail gas is further absorbed by the slurry and discharged up to standard; during absorption, the slurry and the sulfur dioxide process gas are in a counter - current form;

[0050] 2) The obtained 15 t of manganese sulfate reduction liquid is transported through a pipeline to a dissolution tank, and 10m3 The condensed water is made into a manganese sulfate reducing solution with a concentration of 100 g / L; a small amount of sodium sulfide is added to the manganese sulfate reducing solution with a concentration of 100 g / L with excessive impurities, and then it is filtered by a filter press to obtain a manganese sulfate reducing solution that meets the impurity requirements.

[0051] The manganese sulfate reducing solution after impurity removal is mixed with 4 kg of ammonium sulfate to form a manganese sulfate pre - solution.

[0052] The manganese sulfate pre - solution, sodium hydroxide solution, ammonia water, and hydrogen peroxide are respectively pumped into a reaction kettle according to a volume ratio of 500:100:10:1 for synthesis reaction. Among them, the feeding rate of the manganese sulfate pre - solution is 5 m 3 / h, the feeding rate of the alkali solution is 0.5 m 3 / h, the feeding rate of the pH regulator is 0.005 m 3 / h, and the feeding rate of the oxidant is 0.5 L / h.

[0053] The reaction temperature is 90 °C, the pH is 10, the rotation speed is 80 rpm, and at the same time, 200 m 3 / h of air is introduced for oxidation. After reacting for 20 h, a slurry is obtained.

[0054] 3) After the reaction is completed, the synthesized slurry is sent to an aging kettle for aging for 5 h to obtain an aged slurry. The aged slurry is separated by 3 - stage filter press washing to obtain filter residue. The washing filtrate of the filter residue is concentrated brine. The concentrated brine after washing is evaporated and crystallized. The ammonia in the concentrated brine is recovered and utilized after evaporation. The condensed water is recycled for dissolution and washing. The crystals obtained by evaporation and crystallization are dried and packaged to obtain about 0.3 t of sulfate by - product.

[0055] The filter residue is dried and demagnetized to obtain 1 t of battery - grade manganese tetraoxide product, which is packaged and stored in the warehouse.

[0056] The relevant indicators of 1 t of battery - grade manganese tetraoxide product are shown in Table 2.

[0057] Example 3

[0058] For the method for preparing battery - grade manganese tetraoxide described in this example, the manganese content in the pyrolusite raw material is 30% and the water content is 17%; the preparation includes the following steps:

[0059] 1) The pyrolusite is dried at a low temperature to control the water content at 10%; 2.5 t of pyrolusite with a water content of 10% is crushed by a crushing system to make powder, and the particle size of the powder is controlled at 50 - 500 meshes, and then it is mixed with 12.5 t of water to make a pulp.

[0060] Send 300 kg of sulfur to the sulfur combustion furnace for combustion to obtain sulfur dioxide process gas with a volume content of 15%. Feed the sulfur dioxide process gas into the sulfur dioxide gas absorption tower. The heat is absorbed by the waste heat boiler to generate steam for product drying.

[0061] Absorb the sulfur dioxide process gas with the prepared pulp by adopting the eight-stage spray absorption method. After absorption, obtain the manganese sulfate reduction liquid. The tail gas is discharged up to standard after secondary absorption by the pulp. Ensure the countercurrent form of the pulp and the sulfur dioxide process gas during absorption.

[0062] 2) Transport the obtained 15 t of manganese sulfate reduction liquid to the dissolution tank through pipelines, and supplement 10 m 3 of condensed water to prepare a manganese sulfate reduction liquid with a concentration of 100 g / L. Add a small amount of sodium sulfide to the manganese sulfate reduction liquid with excessive impurities at a concentration of 100 g / L, and then filter it through a filter press to obtain a manganese sulfate reduction liquid meeting the impurity requirements.

[0063] Mix the purified manganese sulfate reduction liquid with 4 kg of ammonium sulfate for batching to form a manganese sulfate pre-liquid.

[0064] Pump the manganese sulfate pre-liquid, sodium hydroxide solution, ammonia water, and hydrogen peroxide into the reaction kettle according to the volume ratio of 500:100:10:1 respectively for the synthesis reaction. Among them, the feeding rate of the manganese sulfate pre-liquid is 5 m 3 / h, the feeding rate of the alkali liquid is 0.5 m 3 / h, the feeding rate of the pH regulator is 0.005 m 3 / h, and the feeding rate of the oxidant is 0.5 L / h.

[0065] The reaction temperature is 90 °C, the pH is 10, the rotation speed is 80 rpm, and at the same time, blow in 200 m 3 / h of air for oxidation. After reacting for 20 h, obtain the slurry.

[0066] 3) After the reaction is completed, send the synthesis slurry to the aging kettle for aging for 5 h to obtain the aged slurry. The aged slurry is separated by three-stage pressure filtration and washing to obtain the filter residue. The washing filtrate of the filter residue is concentrated brine. Evaporate and crystallize the washed concentrated brine. The ammonia in the concentrated brine is recovered after evaporation and utilized. The condensed water is recycled for dissolution and washing. The crystals obtained by evaporation and crystallization are dried and packaged to obtain about 0.3 t of sulfate by-products.

[0067] The filter residue is dried and demagnetized to obtain 1 t of battery-grade manganese tetraoxide product, which is packaged and stored in the warehouse.

[0068] The relevant indicators of 1 t of battery-grade manganese tetraoxide product are shown in Table 2.

[0069] Control Example 1

[0070] The preparation method of battery-grade manganese tetroxide described in this embodiment uses pyrolusite raw materials with a manganese content of 30% and a water content of 18%. The preparation includes the following steps:

[0071] 1) Control the moisture content of pyrolusite at 10% by means of low-temperature drying; crush 2.5t of pyrolusite with a moisture content of 10% through a crushing system to make powder, control the particle size of the powder at 50 - 500 mesh, and then mix it with 12.5t of water to make pulp;

[0072] Send 300kg of sulfur to the sulfur combustion furnace for combustion to obtain sulfur dioxide process gas with a volume content of 15%. Pass the sulfur dioxide process gas into the sulfur dioxide gas absorption tower. The heat is absorbed by the waste heat boiler to generate steam for product drying;

[0073] Absorb the sulfur dioxide process gas with the prepared pulp by means of three-stage spray absorption. After absorption, obtain manganese sulfate reduction liquid. The tail gas is further absorbed by the pulp twice and then discharged up to standard; ensure the countercurrent form of the pulp and the sulfur dioxide process gas during absorption;

[0074] 2) Transport the obtained 15t of manganese sulfate reduction liquid to the dissolution tank through pipelines, add 500㎏ of manganese sulfate powder to prepare a manganese sulfate reduction liquid with a concentration of 100g / L; add a small amount of sodium sulfide to the manganese sulfate reduction liquid with a concentration of 100g / L with excessive impurities, and then filter it through a filter press to obtain a manganese sulfate reduction liquid that meets the impurity requirements;

[0075] Mix the manganese sulfate reduction liquid after impurity removal with 4kg of ammonium sulfate for batching to form a manganese sulfate pre-liquid;

[0076] Pump the manganese sulfate pre-liquid, sodium hydroxide solution, ammonia water, and hydrogen peroxide into the reaction kettle for synthesis reaction at a volume ratio of 500:100:10:1 respectively. Among them, the feeding speed of the manganese sulfate pre-liquid is 5m 3 / h, the feeding speed of the alkali solution is 0.5m 3 / h, the feeding speed of the pH regulator is 0.005m 3 / h, and the feeding speed of the oxidant is 0.5L / h;

[0077] The reaction temperature is 90℃, the pH is 10, the rotation speed is 80rpm, and at the same time, blow in 200m 3 / h of air for oxidation. After reacting for 20h, obtain slurry;

[0078] 3) After the reaction is completed, send the synthesis slurry to the aging kettle for aging for 5h to obtain the aged slurry. The aged slurry is separated by three-stage pressure filtration and washing to obtain filter residue. The washing filtrate of the filter residue is concentrated brine. Evaporate and crystallize the concentrated brine after washing. The ammonia in the concentrated brine is recovered and utilized after evaporation, the condensed water is recycled for dissolution and washing, and the crystals obtained by evaporation and crystallization are dried and packaged to obtain about 0.3t of sulfate by-products;

[0079] After drying and demagnetization, 1 t of battery-grade manganese tetroxide product is obtained from the filter residue, which is then packed and stored in the warehouse.

[0080] The relevant indexes of 1 t of battery-grade manganese tetroxide product are shown in Table 2.

[0081] In this comparative example, three-stage spray is used to absorb sulfur dioxide. The leaching reaction of manganese dioxide in the manganese ore is incomplete, and there are many insoluble impurities in the manganese sulfate solution, resulting in a large amount of manganese loss, a reduction in output under the same input, and a large amount of manganese sulfate needs to be supplemented to meet the concentration requirement of the qualified solution.

[0082] Comparative Example 2

[0083] For the preparation method of battery-grade manganese tetroxide described in this example, the manganese content in the pyrolusite raw material is 30% and the water content is 15%. The preparation includes the following steps:

[0084] 1) The pyrolusite is dried at low temperature to control the water content at 10%. 2.5 t of pyrolusite with a water content of 10% is crushed through a crushing system to make powder, and the particle size of the powder is controlled at 50 - 500 mesh, and then mixed with 12.5 t of water to make pulp;

[0085] 300 kg of sulfur is sent to the sulfur combustion furnace for combustion to obtain sulfur dioxide process gas with a volume content of 15%. The sulfur dioxide process gas is introduced into the sulfur dioxide gas absorption tower, and the heat is absorbed by the waste heat boiler to generate steam for product drying;

[0086] The prepared pulp is used to absorb the sulfur dioxide process gas. The ten-stage spray absorption method is adopted. After absorption, a manganese sulfate reduction solution is obtained, and the tail gas is further absorbed by the pulp twice and then discharged up to the standard; During absorption, the form of countercurrent flow of the pulp and the sulfur dioxide process gas is ensured;

[0087] 2) The obtained 15 t of manganese sulfate reduction solution is transported to the dissolution tank through a pipeline, and 10 m 3 of condensed water is added to prepare a manganese sulfate reduction solution with a concentration of 100 g / L; A small amount of sodium sulfide is added to the manganese sulfate reduction solution with a concentration of 100 g / L with excessive impurities, and then it is filtered through a filter press to obtain a manganese sulfate reduction solution meeting the impurity requirements;

[0088] The manganese sulfate reduction solution after impurity removal is mixed with 4 kg of ammonium sulfate for batching to form a manganese sulfate pre-solution;

[0089] The manganese sulfate pre-solution, sodium hydroxide solution, and ammonia water are respectively pumped into the reaction kettle according to the volume ratio of 500:100:10 for synthesis reaction, and the addition rate of the manganese sulfate pre-solution is 5 m 3 / h, and the addition rate of the alkali solution is 0.5 m 3 / h, the addition rate of the pH regulator is 0.05 m 3 / h;

[0090] The reaction temperature is 90 °C, the pH is 10, the rotation speed is 80 rpm, and at the same time, 200 m 3 / h of air is introduced for oxidation. After reacting for 20 h, a slurry is obtained;

[0091] 3) After the reaction is completed, the synthesized slurry is sent to an aging kettle for aging for 5 h to obtain an aged slurry. The aged slurry is separated by three-stage pressure filtration and washing to obtain filter residue. The washing filtrate of the filter residue is concentrated brine. The concentrated brine after washing is evaporated and crystallized. The ammonia in the concentrated brine is recovered after evaporation and used again. The condensed water is recycled for dissolution and washing. The crystals obtained by evaporation and crystallization are dried and packaged to obtain about 0.3 t of sulfate by-products;

[0092] The filter residue is dried and demagnetized to obtain 1 t of battery-grade manganese tetroxide product, which is packaged and stored in the warehouse.

[0093] The relevant indexes of 1 t of battery-grade manganese tetroxide product are shown in Table 2.

[0094] In this comparative example, the oxidant input is zero, resulting in incomplete oxidation reaction of the product and poor product morphology finally formed.

[0095] Comparative Example 3

[0096] For the method for preparing battery-grade manganese tetroxide described in this example, the manganese content in the pyrolusite raw material is 30% and the water content is 15%; the preparation includes the following steps:

[0097] 1) The pyrolusite is dried at low temperature to control the water content at 10%; 2.5 t of pyrolusite with a water content of 10% is crushed by a crushing system to make powder, and the particle size of the powder is controlled at 50 - 500 mesh, and then it is mixed with 12.5 t of water to make a slurry;

[0098] 300 kg of sulfur is sent to a sulfur combustion furnace for combustion to obtain sulfur dioxide process gas with a volume content of 15%. The sulfur dioxide process gas is introduced into a sulfur dioxide gas absorption tower, and the heat is absorbed by a waste heat boiler to generate steam for product drying;

[0099] The prepared slurry is used to absorb the sulfur dioxide process gas, and the absorption is carried out by a ten-stage spray absorption method. After the absorption is completed, a manganese sulfate reduction solution is obtained, and the tail gas is further absorbed by the slurry and then discharged up to the standard; during the absorption, the form of countercurrent flow of the slurry and the sulfur dioxide process gas is ensured;

[0100] 2) The obtained 15 t of manganese sulfate reduction solution is transported to a dissolution tank through a pipeline, and 10 m 3The condensed water is made into a manganese sulfate reducing solution with a concentration of 100 g / L; a small amount of sodium sulfide is added to the manganese sulfate reducing solution with a concentration of 100 g / L and excessive impurities, and then it is filtered by a filter press to obtain a manganese sulfate reducing solution that meets the impurity requirements;

[0101] The manganese sulfate reducing solution after impurity removal is mixed with 4 kg of ammonium sulfate to form a manganese sulfate pre - solution;

[0102] The manganese sulfate pre - solution, sodium hydroxide solution, and hydrogen peroxide are respectively pumped into the reaction kettle at a volume ratio of 500:100:1 for synthesis reaction. Among them, the feeding rate of the manganese sulfate pre - solution is 5 m 3 / h, the feeding rate of the alkali solution is 0.5 m 3 / h, and the feeding rate of the oxidant is 0.005 m 3 / h;

[0103] The reaction temperature is 90 °C, the pH is 10, the rotation speed is 80 rpm, and at the same time, 200 m 3 / h of air is introduced for oxidation. After reacting for 20 h, a slurry is obtained;

[0104] 3) After the reaction is completed, the synthesis slurry is sent to the aging kettle for aging for 5 h to obtain an aged slurry. The aged slurry is separated by 3 - stage pressure filtration and washing to obtain filter residue. The washing filtrate of the filter residue is concentrated brine. The concentrated brine after washing is evaporated and crystallized. The ammonia in the concentrated brine is recovered and utilized after evaporation, the condensed water is recycled for dissolution and washing, and the crystals obtained by evaporation and crystallization are dried and packaged to obtain about 0.3 t of sulfate by - product;

[0105] The filter residue is dried and demagnetized to obtain 1 t of battery - grade manganese tetraoxide product, which is packaged and stored in the warehouse.

[0106] The relevant indexes of 1 t of battery - grade manganese tetraoxide product are shown in Table 2.

[0107] In this comparative example, the PH regulator is not added, resulting in an increase in the solution viscosity, a slowdown in the reaction rate, and the presence of impurities such as manganous sulfate in the final product.

[0108] Before the concentration adjustment and impurity removal treatment in Example 1, Example 2, Example 3 and Comparative Example 1, Comparative Example 2, Comparative Example 2, the comparison results of the manganese ion concentration in the manganese sulfate reducing solution are shown in Table 1. It can be seen that when using pyrolusite pulp to absorb sulfur dioxide, the higher the spraying stage, the higher the manganese recovery rate.

[0109] Table 1

[0110] Project Manganese ion concentration in solution g / L Example 1 166.67 Example 2 155.58 Example 3 161.37 Control Example 1 78.86 Control Example 2 166.78 Control Example 3 157.37

[0111] The relevant index parameters of the battery - grade manganese tetraoxide products obtained in Example 1, Example 2, Example 3 and Comparative Example 1, Comparative Example 2, Comparative Example 3 are shown in Table 2.

[0112] Table 2

[0113]

[0114]

[0115] As can be seen from Table 2, the contents of battery-grade manganese tetroxide obtained by using the technology of the present invention are 71.90%, 71.27% and 71.48% respectively in terms of Mn, which are higher than the standards of high-purity types in the industry. The reaction in the whole process is rapid and complete, without the need for high temperature, with low energy consumption. The obtained battery-grade manganese tetroxide product is highly purified, has uniform particle size and stable quality. If the number of spray absorption stages of sulfur dioxide gas and pyrolusite is too small, it will lead to an increase in the loss of manganese and the need to additionally supplement manganese sulfate. Although the product is qualified, the economic benefit is greatly reduced. In addition, if the additive parameters are used improperly, it may lead to an increase in the impurity content of the product and the product quality is not ideal.

[0116] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of battery-grade manganese tetroxide, characterized in that, It includes the following steps: 1) After crushing pyrolusite and mixing it with water to make a pulp, the pulp absorbs sulfur dioxide gas by means of multi-stage spraying to obtain a manganese sulfate reduction solution; The number of stages of multi-stage spraying absorption is 5 to 15 stages, and the sulfur dioxide gas is sulfur dioxide process gas, and the volume content of sulfur dioxide in the sulfur dioxide process gas is 10 to 15%; 2) Mix the manganese sulfate reduction solution with a buffer to obtain a manganese sulfate pre-solution, and continue to mix the manganese sulfate pre-solution with an alkali solution, a pH regulator, and an oxidant to carry out a reaction, and air is introduced during the reaction; the buffer is one or more of sulfates, nitrates, and chlorides; 3) Aging the slurry after the reaction in step 2) is completed, filtering after aging to obtain a filter residue, and drying and demagnetizing the filter residue to obtain battery-grade manganese tetroxide.

2. The preparation method of battery-grade manganese tetraoxide according to claim 1, characterized in that, In step 1), the pyrolusite is pretreated to have a water content of 5 to 12%, the particle size after crushing the pyrolusite is 50 to 500 mesh, and the liquid-solid ratio for preparing the pulp is 1 to 10:

1.

3. The preparation method of battery-grade manganese tetraoxide according to claim 1, characterized in that, In step 2), impurity removal treatment is carried out before mixing the manganese sulfate reduction solution with the buffer. Before impurity removal, the concentration is adjusted to 50 to 200 g / L, an impurity remover is added to the manganese sulfate reduction solution after adjusting the concentration, and then filtered, and the filtrate is taken for standby.

4. The preparation method of battery-grade manganese tetraoxide according to claim 1, characterized in that, In step 2), the mass ratio of manganese sulfate to the buffer in the manganese sulfate reduction solution ranges from 1 to 1000:1, the volume ratio of the manganese sulfate pre-solution to the alkali solution ranges from 1 to 10:1, and the addition rate of the alkali solution is 0.01 to 1 m³ / h; the volume ratio of the manganese sulfate pre-solution to the pH regulator ranges from 10 to 100:1, and the addition rate of the pH regulator is 0.001 to 0.1 m³ / h, the volume ratio of the manganese sulfate pre-solution to the oxidant ranges from 100 to 1000:1, and the addition rate of the oxidant is 0.01 to 1 L / h.

5. The preparation method of battery-grade manganese tetraoxide according to claim 1, characterized in that, In step 2); the pH regulator is one or more of ammonium salt solutions or ammonia water solutions; the oxidant is one or more of hydrogen peroxide, nitric acid, and peroxide aqueous solutions.

6. The preparation method of battery-grade manganese tetraoxide according to claim 1, wherein, In step 2), the amount of air blown in is 100 to 500 m³ / h.

7. The preparation method of battery-grade manganese tetroxide according to claim 1, characterized in that, In step 2), the reaction pH value is 5 to 11, the reaction temperature is 1 to 200 °C, the reaction time is 1 to 48 h, and stirring is maintained during the reaction, and the stirring speed is 10 to 200 rpm.

8. The preparation method of battery-grade manganese tetroxide according to claim 1, characterized in that, In step 3), the aging treatment time is 1 to 10 h.

9. The preparation method of battery-grade manganese tetraoxide according to claim 1, wherein, In the battery-grade manganese tetroxide, the manganese content is higher than 70%.

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