Method for preparing high-purity manganese sulfate from low-grade manganese carbonate

Abstract

The invention belongs to the technical field of new energy materials, and discloses a method for preparing high-purity manganese sulfate from low-grade manganese carbonate, the low-grade manganese carbonate ore in the bronze kernel area is directly used for sulfuric acid leaching, through reasonable stirring speed, reasonable material ratio and reasonable feeding mode, the reaction speed is increased, meanwhile, the leaching rate of manganese is increased, and the high-purity manganese sulfate is obtained. By controlling the proper pH, reducing the content of impurities in the solution, not needing other additives, being simple in process and high in efficiency, the problem of utilization of low-grade manganese carbonate ore is solved, then a rough manganese sulfate solution is obtained through solid-liquid separation, a high-purity manganese sulfate product is obtained through multi-stage impurity removal and evaporative crystallization drying, the cost is reduced, and the method is suitable for industrial production. And the efficiency and the market competitiveness are improved.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals and new material processing, and is a method for preparing high-purity manganese sulfate from low-grade manganese carbonate. Background Art

[0002] Low-grade manganese carbonate refers to manganese carbonate ore containing a relatively low content of manganese (Mn). Its main component is divalent manganese carbonate (MnCO3). Usually, the manganese grade in this type of ore is lower than the standard requirements for economic mining and direct utilization. In the earth's crust, manganese carbonate ore exists in the form of rhodochrosite, but when its manganese content is lower than a certain threshold, it is called low-grade manganese carbonate ore.

[0003] High-purity manganese sulfate is an inorganic compound with extremely high purity. Its chemical formula is usually expressed as MnSO4·xH2O, where x represents the degree of hydration. Usually, industrial high-purity manganese sulfate is monohydrate manganese sulfate (MnSO4·H2O). As an important industrial chemical and battery material, high-purity manganese sulfate has low impurity content, especially strict control of other elements such as potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), and iron (Fe). In terms of physical properties, high-purity manganese sulfate usually appears as white to light red fine crystals or powder, odorless, non-flammable, but decomposition reactions will occur at high temperatures. A molten material is formed at 700°C, and decomposition begins above 850°C. High-purity manganese sulfate is mainly used in the preparation of lithium battery positive electrode materials, as well as in the pharmaceutical, electronics and other industries. It is also a key material in the supply chain of new energy industries and high-tech industries. The preparation of high-purity manganese sulfate involves the cross-application of multiple aspects such as the extraction of mineral resources, chemical reaction engineering, hydrometallurgical technology, purification technology, and environmental protection technology.

[0004] The process of preparing high-purity manganese sulfate from manganese carbonate is a deep processing technology based on manganese ore resources, which is mainly used to meet the growing demand for high-purity manganese sulfate in the new energy battery materials and specialty chemicals industries. With the strengthening of environmental protection policies and the rapid development of the battery industry, especially the manufacture of lithium-ion battery positive electrode materials (such as lithium manganese oxide, nickel-cobalt-manganese ternary materials), the purity requirements for high-purity manganese sulfate are constantly increasing.

[0005] Globally, manganese ore resources are abundant but the grades vary greatly. Some resources exist in the form of manganese carbonate, which has a relatively low grade. In order to effectively utilize this part of resources, it is crucial to develop and optimize the process of extracting high-purity manganese sulfate from low-grade manganese carbonate.

[0006] Traditional methods for producing manganese sulfate: two-ore one-step method, using manganese dioxide ore powder and pyrite, under the action of sulfuric acid, to produce manganese sulfate through redox reaction. One method is to roast manganese dioxide with a reducing substance, reduce tetravalent manganese to divalent manganese, and then react with sulfuric acid to produce manganese sulfate. Another method is to use manganese carbonate to directly add sulfuric acid to produce manganese sulfate.

[0007] Utilization of manganese carbonate ore: At present, manganese carbonate is mostly used to produce electrolytic manganese metal and other manganese compounds, such as manganese dioxide, manganese tetraoxide, etc. after preparing crude manganese sulfate solution.

[0008] Method for preparing manganese sulfate from manganese carbonate: The traditional method is also to directly prepare crude manganese sulfate by reacting with sulfuric acid, and then obtain high-purity manganese sulfate through precipitation, purification and crystallization. For example, manganese carbonate ore is first leached with sulfuric acid to obtain a manganese sulfate solution, and then impurities, including calcium and magnesium ions, heavy metal ions, etc., are removed through a series of chemical reactions and physical processes, and finally a manganese sulfate product is obtained by evaporation and crystallization. However, these methods require the introduction of substances such as barium sulfate and ammonium bicarbonate to participate in the reaction, or the addition of other additives. The process is complicated, the by-product treatment cost is high, and the product impurities are high. For example, CN201710978652.6 is a short-process preparation method for fluorine-free and sulfur-free high-purity manganese sulfate monohydrate powder, CN201811497203.0 is a method for preparing high-purity manganese sulfate from lean rhodochrosite, and CN201610815585.1 is a method for preparing high-purity manganese phosphate from low-grade rhodochrosite leachate. In the early steps, there is also a process of directly adding acid to rhodochrosite to prepare crude manganese sulfate solution, in which sodium phosphate plays a very important role.

[0009] There are also process methods that use additives in the leaching step to obtain high-purity manganese sulfate in one go, such as CN201710978652.6, a short-process preparation method for fluorine-free and sulfur-free high-purity manganese sulfate monohydrate powder.

[0010] In summary, the use of additives in the leaching process in the prior art will introduce other impurities, requiring more impurity removal steps in the later stage, and the process operation is complicated and the by-product treatment is complicated. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention provides a method for preparing high-purity manganese sulfate from low-grade manganese carbonate. Low-grade manganese carbonate ore in Tongren area is directly used for sulfuric acid leaching. A reasonable stirring speed, a reasonable material ratio and a reasonable feeding method are used to increase the reaction speed and the leaching rate of manganese. The impurity content in the solution is reduced by controlling a suitable pH value. No other additives are needed. The process is simple and efficient. The problem of utilizing low-grade manganese carbonate ore is solved. Then, a crude manganese sulfate solution is obtained through solid-liquid separation, and then a high-purity manganese sulfate product is obtained through multi-stage impurity removal and evaporation, crystallization and drying. The cost is reduced and the efficiency and market competitiveness are improved.

[0012] The present invention adopts the following technical solutions:

[0013] A method for preparing high-purity manganese sulfate from low-grade manganese carbonate comprises the following steps:

[0014] 1) Add slag washing water into the reactor, the concentration of manganese sulfate in the slag washing water is 70-150g / L, and the mass ratio of the slag washing water to the manganese carbonate ore is about 2.5:1, then start stirring and adjust the stirring speed to 30-50r / min;

[0015] 2) Slowly adding 98.3% concentrated sulfuric acid into the reactor, with the molar ratio of manganese carbonate to sulfuric acid being less than 0.4:1, and controlling the final pH to be 1.5-2;

[0016] 3) Start steam heating and control the temperature between 80-85° C. During the reaction, measure the pH frequently. If the pH is too high, continue to add acid for reaction. If the pH has reached the requirement, continue the reaction for 2 hours until the pH is stable. The final pH is controlled between 1.5-2 to obtain a crude manganese sulfate solution;

[0017] 4) removing impurities by ammonia sulfidation and acidification, specifically: reacting a crude manganese sulfate solution with ammonia water and hydrogen sulfide to generate manganese sulfide, separating impurities from manganese, with a large amount of impurities in the liquid phase and manganese in the solid phase, thereby achieving an impurity removal effect, filtering the slurry after the reaction through a filter press, and obtaining a solid manganese sulfide, adding sulfuric acid to the manganese sulfide to react to generate a manganese sulfate solution, controlling the endpoint pH to leave some impurities in the solid phase, and filtering again with a filter press to obtain a clear refined manganese sulfate solution;

[0018] 5) evaporating, crystallizing and drying the manganese sulfate solution, specifically: heating the refined manganese sulfate solution in an enamel kettle for evaporation and concentration, the heating method is steam jacket heating, when the manganese sulfate solution is concentrated to a white milky state, the manganese sulfate slurry is dehydrated, and the dehydrated material is dried in an airflow drying device to obtain a high-purity manganese sulfate product.

[0019] "There are no idle stones in Guizhou, and there are many treasures in your place". Tongren is an important manganese resource-rich area in China, with a total proven reserves of 753 million tons of manganese carbonate ore, accounting for about 37% of the country, ranking first, including 4 world-class super-large manganese deposits. Tongren, Guizhou is located in China's "Manganese Triangle" area, with rich manganese ore reserves, mainly in the form of rhodochrosite. Taking Songtao manganese ore as an example, the manganese mass fraction of the mineral is about 15%, which is a low-grade medium-iron acidic rhodochrosite; the chemical composition and phase composition of the ore are relatively complex, among which the manganese element mainly exists in the form of manganese carbonate, and a small amount of manganese dioxide; calcium and magnesium elements mainly exist in the form of dolomite, and a small amount exists in the form of silicate.

[0020] The present invention improves the reaction speed by reasonable stirring speed, reasonable material ratio, and reasonable feeding method; reduces the impurity content in the solution by controlling the appropriate pH, and does not need to use other additives. Wherein, the mass ratio of the amount of slag washing water added in step 1) to the manganese carbonate ore is about 2.5:1; the mass ratio of sulfuric acid in step 2) is 2.75:1. Since the manganese content of manganese ore is about 15%, the molar ratio of manganese carbonate to sulfuric acid is about 0.4:1, but at the same time, the manganese ore contains a large amount of impurities that react with acid, so the acid needs to be excessive to improve the manganese leaching rate, but at the same time, the final pH needs to be controlled to prevent excessive reaction of impurities.

[0021] The impurity content is mainly affected by the mineral powder raw materials and the concentration of manganese sulfate. It is normal within a certain range. For example, calcium within 800ppm is normal.

[0022] After the reaction is completed, the leaching rate of manganese reaches more than 95%. The slurry in the reactor is filtered using a filter press to obtain a clear crude manganese sulfate solution with a concentration between 190-270 g / L.

[0023] Preferably, the slag washing water in step 1) is recycled, the filter residue obtained in step 3) is slurried with pure water and filtered again, and the filtrate obtained is the slag washing water. The slag washing water is repeatedly slurried until the concentration drops to 70g / L, and the obtained slag washing water is put into the reactor.

[0024] The leaching rate of manganese reaches more than 95%. The filtered residue is slurried with pure water and filtered again. The filtrate obtained is the slag washing water. The slag washing water can be repeatedly slurried until the concentration drops to 70g / L. The obtained slag washing water is recycled into the reactor. The concentration of the slag washing water is 70-150g / L. The process of step 1) is performed again to achieve the purpose of fully recovering manganese, improving the yield, increasing the leaching concentration, and reducing the use of water resources.

[0025] Preferably, in step 1), the stirring speed is adjusted by a frequency converter, the frequency converter is adjusted to 40 Hz, and the stirring speed is about 40 r / min.

[0026] The method for preparing manganese sulfate solution by two-ore method includes using manganese dioxide ore powder and pyrite ore powder, and preparing manganese sulfate solution through heating reaction, impurity removal, neutralization, filter pressing and other steps. This process has the advantages of small consumption of sulfuric acid, low production cost, high manganese content in the product, high manganese recovery rate, etc., and is suitable for further deep processing of high-purity manganese products.

[0027] Compared with the two-ore method, the reaction time of the present invention is faster. The two-ore method takes about 7 hours to complete the reaction, while it only takes 5 hours to prepare manganese sulfate by adding acid to manganese carbonate, thereby reducing the equipment operation time and the power consumption.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] The invention uses low-grade manganese carbonate ore in Tongren area to directly carry out sulfuric acid leaching, and the low-grade manganese carbonate directly reacts with sulfuric acid to prepare manganese sulfate solution without using other additives. The process is simple and efficient, and the problem of utilizing the low-grade manganese carbonate ore is solved at the same time.

[0030] Through reasonable stirring speed, reasonable material ratio, and reasonable feeding method, the reaction speed is increased while the manganese leaching rate is increased, which provides a good method for saving costs and efficiently utilizing low-grade manganese ore.

[0031] By controlling the appropriate pH, the impurity content in the solution is reduced, and no other additives are needed. The process is simple and efficient, and the problem of low-grade manganese carbonate ore utilization is solved.

[0032] The process of the present invention has high economic benefits, reduces equipment operating time, reduces electricity consumption, can increase the added value of products, and bring more profits to enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a schematic flow chart of the process for preparing high-purity manganese sulfate from low-grade manganese carbonate. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] The present invention will be further described below in conjunction with specific embodiments.

[0036] In the embodiment, the reactor is 100m 3 Brick lined iron tank, normal pressure.

[0037] Example 1

[0038] A method for preparing high-purity manganese sulfate from low-grade manganese carbonate comprises the following steps:

[0039] 1) Feeding: First add 70m3 of 3 Slag washing water, the concentration of slag washing water is measured to be 98g / L, and then the manganese carbonate powder is transferred to the feeding tank by a crane, a total of 28T, the mass ratio of slag washing water added to manganese carbonate ore is about: 2.5:1, and then start stirring, and adjust the stirring speed to 30r / min;

[0040] 2) Adding acid: Before adding acid, check whether the acid pipe is leaking, turn on the ventilation fan, and then open the corresponding valve. Since there is acid mist during the acid addition process, the operator must wear an acid-proof mask and use 98.3% concentrated sulfuric acid. The acid addition flow rate is controlled at 1.0-1.5m 3 / h, after 3 hours, 3.75 cubic meters of acid was added, and the pH value was 1.8 when tested with precision pH test paper;

[0041] 3) Start steam heating and control the temperature between 80-85° C. Measure pH frequently during the reaction. If the pH is too high, continue to add acid for reaction. If the pH has reached the requirement, continue the reaction for 2 hours until the pH is stable and the final pH is 1.55 to obtain a crude manganese sulfate solution;

[0042] Crude manganese sulfate solution data:

[0043]

[0044] 4) removing impurities by ammonia sulfidation and acidification, specifically: reacting a crude manganese sulfate solution with ammonia water and hydrogen sulfide to generate manganese sulfide, separating impurities from manganese, with a large amount of impurities in the liquid phase and manganese in the solid phase, thereby achieving an impurity removal effect, filtering the slurry after the reaction through a filter press, and obtaining a solid manganese sulfide, adding sulfuric acid to the manganese sulfide to react to generate a manganese sulfate solution, controlling the endpoint pH to leave some impurities in the solid phase, and filtering again with a filter press to obtain a clear refined manganese sulfate solution;

[0045] 5) evaporating, crystallizing and drying the manganese sulfate solution, specifically: heating the refined manganese sulfate solution in an enamel kettle for evaporation and concentration, the heating method is steam jacket heating, when the manganese sulfate solution is concentrated to a white milky state, the manganese sulfate slurry is dehydrated, and the dehydrated material is dried in an airflow drying device to obtain a high-purity manganese sulfate product.

[0046] Example 2

[0047] A method for preparing high-purity manganese sulfate from low-grade manganese carbonate comprises the following steps:

[0048] 1) Feeding: First add 70m3 of 3Slag washing water, the concentration of slag washing water is measured to be 95g / L, and then the manganese carbonate powder is transferred to the feeding tank by a crane, a total of 28T, the mass ratio of slag washing water added to manganese carbonate ore is about: 2.5:1, and then start stirring, and adjust the stirring speed to 50r / min;

[0049] 2) Adding acid: Before adding acid, check whether the acid pipe is leaking, turn on the ventilation fan, and then open the corresponding valve. Since there is acid mist during the acid addition process, the operator must wear an acid-proof mask and use 98.3% concentrated sulfuric acid. The acid addition flow rate is controlled at 1.0-1.5m 3 / h, after 3 hours, 5.25 cubic meters of acid was added, and the pH value was 1.5 when tested with precision pH test paper;

[0050] 3) Start steam heating and control the temperature between 80-85° C. Measure pH frequently during the reaction. If the pH is too high, continue to add acid for reaction. If the pH has reached the requirement, continue the reaction for 2 hours until the pH is stable and the final pH is 1.56, to obtain a crude manganese sulfate solution;

[0051] Crude manganese sulfate solution data:

[0052]

[0053]

[0054] 4) removing impurities by ammonia sulfidation and acidification, specifically: reacting a crude manganese sulfate solution with ammonia water and hydrogen sulfide to generate manganese sulfide, separating impurities from manganese, with a large amount of impurities in the liquid phase and manganese in the solid phase, thereby achieving an impurity removal effect, filtering the slurry after the reaction through a filter press, and obtaining a solid manganese sulfide, adding sulfuric acid to the manganese sulfide to react to generate a manganese sulfate solution, controlling the endpoint pH to leave some impurities in the solid phase, and filtering again with a filter press to obtain a clear refined manganese sulfate solution;

[0055] 5) evaporating, crystallizing and drying the manganese sulfate solution, specifically: heating the refined manganese sulfate solution in an enamel kettle for evaporation and concentration, the heating method is steam jacket heating, when the manganese sulfate solution is concentrated to a white milky state, the manganese sulfate slurry is dehydrated, and the dehydrated material is dried in an airflow drying device to obtain a high-purity manganese sulfate product.

[0056] Example 3

[0057] A method for preparing high-purity manganese sulfate from low-grade manganese carbonate comprises the following steps:

[0058] 1) Feeding: First add 75m3 of 3Slag washing water, the concentration of slag washing water is measured to be 139g / L, and then the manganese carbonate powder is transferred to the feeding tank by a crane, a total of 28T, the mass ratio of slag washing water added to manganese carbonate ore is about: 2.5:1, and then the stirring is turned on and the stirring speed is adjusted to 40r / min;

[0059] 2) Adding acid: Before adding acid, check whether the acid pipe is leaking, turn on the ventilation fan, and then open the corresponding valve. Since there is acid mist during the acid addition process, the operator must wear an acid-proof mask and use 98.3% concentrated sulfuric acid. The acid addition flow rate is controlled at 1.0-1.5m 3 / h, after 3 hours, 5.50 cubic meters of acid was added, and the pH value was 1.6 when tested with precision pH test paper;

[0060] 3) Start steam heating and control the temperature between 80-85° C. Measure pH frequently during the reaction. If the pH is too high, continue to add acid for reaction. If the pH has reached the requirement, continue the reaction for 2 hours until the pH is stable and the final pH is 1.92 to obtain a crude manganese sulfate solution;

[0061] Crude manganese sulfate solution data:

[0062]

[0063]

[0064] 4) removing impurities by ammonia sulfidation and acidification, specifically: reacting a crude manganese sulfate solution with ammonia water and hydrogen sulfide to generate manganese sulfide, separating impurities from manganese, with a large amount of impurities in the liquid phase and manganese in the solid phase, thereby achieving an impurity removal effect, filtering the slurry after the reaction through a filter press, and obtaining a solid manganese sulfide, adding sulfuric acid to the manganese sulfide to react to generate a manganese sulfate solution, controlling the endpoint pH to leave some impurities in the solid phase, and filtering again with a filter press to obtain a clear refined manganese sulfate solution;

[0065] 5) evaporating, crystallizing and drying the manganese sulfate solution, specifically: heating the refined manganese sulfate solution in an enamel kettle for evaporation and concentration, the heating method is steam jacket heating, when the manganese sulfate solution is concentrated to a white milky state, the manganese sulfate slurry is dehydrated, and the dehydrated material is dried in an airflow drying device to obtain a high-purity manganese sulfate product.

[0066] Example 4

[0067] A method for preparing high-purity manganese sulfate from low-grade manganese carbonate comprises the following steps:

[0068] 1) Feeding: First add 75m3 of 3Slag washing water, the concentration of slag washing water is measured to be 70g / L, and then the manganese carbonate powder is transferred to the feeding tank by a crane, a total of 28T, the mass ratio of slag washing water added to manganese carbonate ore is about: 2.5:1, and then start stirring, and adjust the stirring speed to 40r / min;

[0069] 2) Adding acid: Before adding acid, check whether the acid pipe is leaking, turn on the ventilation fan, and then open the corresponding valve. Since there is acid mist during the acid addition process, the operator must wear an acid-proof mask and use 98.3% concentrated sulfuric acid. The acid addition flow rate is controlled at 1.0-1.5m 3 / h, after 3 hours, a total of 5.92 cubic meters of acid was added, and the pH value detected by precision pH test paper was 2.0;

[0070] 3) Start steam heating and control the temperature between 80-85° C. Measure pH frequently during the reaction. If the pH is too high, continue to add acid for reaction. If the pH has reached the requirement, continue the reaction for 2 hours until the pH is stable and the final pH is 1.85 to obtain a crude manganese sulfate solution;

[0071] Crude manganese sulfate solution data:

[0072] Data item Crude manganese sulfate K (ug / mL) 145 Na (ug / mL) 378 Ca (ug / mL) 606 Mg (ug / mL) 7833 Cu (ug / mL) 2.0 Co (ug / mL) 8.7 Ni (ug / mL) 16 Pb (ug / mL) 13 Ti (ug / mL) 12.2 Al (ug / mL) 447 Zn (ug / mL) 22 Cd (ug / mL) 0.6 Si (ug / mL) 89 Fe (ug / mL) 6523 pH 1.85 Concentration (g / L) 228.52

[0073] 4) removing impurities by ammonia sulfidation and acidification, specifically: reacting a crude manganese sulfate solution with ammonia water and hydrogen sulfide to generate manganese sulfide, separating impurities from manganese, with a large amount of impurities in the liquid phase and manganese in the solid phase, thereby achieving an impurity removal effect, filtering the slurry after the reaction through a filter press, and obtaining a solid manganese sulfide, adding sulfuric acid to the manganese sulfide to react to generate a manganese sulfate solution, controlling the endpoint pH to leave some impurities in the solid phase, and filtering again with a filter press to obtain a clear refined manganese sulfate solution;

[0074] 5) evaporating, crystallizing and drying the manganese sulfate solution, specifically: heating the refined manganese sulfate solution in an enamel kettle for evaporation and concentration, the heating method is steam jacket heating, when the manganese sulfate solution is concentrated to a white milky state, the manganese sulfate slurry is dehydrated, and the dehydrated material is dried in an airflow drying device to obtain a high-purity manganese sulfate product.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high-purity manganese sulfate from low-grade manganese carbonate, characterized in that: The following steps are involved: 1) Add slag washing water into the reactor, the concentration of manganese sulfate in the slag washing water is 70-150g / L, and the mass ratio of the slag washing water to the manganese carbonate ore is about 2.5:1, then start stirring and adjust the stirring speed to 30-50r / min; 2) Slowly add 98.3% concentrated sulfuric acid into the reactor, with the molar ratio of manganese carbonate to sulfuric acid being less than 0.4:1, and control the final pH to be 1.5-2; 3) Start steam heating and control the temperature between 80-85° C. During the reaction, measure the pH frequently. If the pH is too high, continue to add acid for reaction. If the pH has reached the requirement, continue the reaction for 2 hours until the pH is stable. The final pH is controlled between 1.5-2 to obtain a crude manganese sulfate solution; 4) removing impurities by ammonia sulfidation and acidification, specifically: reacting a crude manganese sulfate solution with ammonia water and hydrogen sulfide to generate manganese sulfide, separating impurities from manganese, with a large amount of impurities in the liquid phase and manganese in the solid phase, thereby achieving an impurity removal effect, filtering the slurry after the reaction through a filter press, and obtaining a solid manganese sulfide, adding sulfuric acid to the manganese sulfide to react to generate a manganese sulfate solution, controlling the endpoint pH to leave some impurities in the solid phase, and filtering again with a filter press to obtain a clear refined manganese sulfate solution; 5) evaporating, crystallizing and drying the manganese sulfate solution, specifically: heating the refined manganese sulfate solution in an enamel kettle for evaporation and concentration, the heating method is steam jacket heating, when the manganese sulfate solution is concentrated to a white milky state, the manganese sulfate slurry is dehydrated, and the dehydrated material is dried in an airflow drying device to obtain a high-purity manganese sulfate product.

2. A method for preparing high-purity manganese sulfate from low-grade manganese carbonate as claimed in claim 1, characterized in that: The slag washing water in step 1) is recycled, and the filter residue obtained in step 3) is slurried with pure water and filtered again, and the filtrate obtained is the slag washing water, and the slag washing water is repeatedly slurried until the concentration reaches more than 70g / L, but not higher than 150g / L. The obtained slag washing water is put into the reactor.

3. A method for preparing high-purity manganese sulfate from low-grade manganese carbonate as claimed in claim 1, characterized in that: In step 1), the stirring speed is adjusted by a frequency converter, the frequency converter is adjusted to 40 Hz, and the stirring speed is about 40 r / min.

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