Evaporative crystallization method and equipment for battery-grade manganese sulfate

Abstract

The invention discloses an evaporative crystallization method and equipment for battery-grade manganese sulfate, and solves the problems that an MVR-OSLO continuous crystallization system is applied to preparation of battery-grade manganese sulfate and relatively good particle size distribution uniformity is obtained. Comprising the following steps: feeding manganese sulfate feed liquid into a preheater for preheating, and preheating the manganese sulfate feed liquid by the preheater by using steam condensate discharged by a heating chamber of a single-stage MVR-OSLO continuous crystallization system as a heat source; the preheated manganese sulfate feed liquid is fed into a single-stage MVR-OSLO continuous crystallization system for evaporative crystallization, and then crystallized suspension liquid is output from a product outlet of a crystallization chamber of the single-stage MVR-OSLO continuous crystallization system; inputting the crystallized suspension into a cyclone for primary solid-liquid separation, returning fine grains which do not reach the preset grain size to the single-stage MVR-OSLO continuous crystallization system along with separated primary mother liquor for evaporative crystallization again, and outputting qualified grains which reach the preset grain size from residual slurry; and the residual slurry is input into a centrifugal machine to be subjected to secondary solid-liquid separation, and the battery-grade manganese sulfate to be dried is obtained.

Description

Technical Field

[0001] The invention relates to a preparation technology of battery-grade manganese sulfate, and in particular to an evaporation and crystallization method and equipment for battery-grade manganese sulfate. Background Art

[0002] Manganese sulfate is an important chemical raw material, especially battery-grade manganese sulfate, which has important applications in the preparation of positive electrode materials for lithium batteries. Battery-grade manganese sulfate has high quality requirements. Specifically, battery-grade manganese sulfate has specific requirements for the particle size and uniformity of manganese sulfate, so its crystallization process directly affects product quality.

[0003] At present, the industrial preparation of battery-grade manganese sulfate mainly adopts evaporation concentration + intermittent crystallization process. This process controls the particle size and morphology of the crystals by adjusting the process parameters of the crystallization process. Although it can obtain better product quality, it has the disadvantages of large equipment investment, complex process flow and high energy consumption. At the same time, the intermittent operation mode leads to low production efficiency and large fluctuations in product quality between batches. In addition, some manufacturers adopt multi-effect evaporation crystallization or high temperature and high pressure crystallization process. Although the multi-effect evaporation crystallization process can process a large amount of manganese sulfate solution, it has large equipment investment, complex system, and serious scaling, difficult cleaning and maintenance. The high temperature and high pressure crystallization process has high requirements on equipment materials, not only high manufacturing cost, but also safety hazards, and high energy consumption. It can be seen that traditional processes generally have problems such as low energy utilization efficiency, large equipment investment, and complex operation, which are difficult to meet the requirements of modern industry for energy saving, environmental protection, low cost and high efficiency. Therefore, it is of great significance to develop a battery-grade manganese sulfate crystallization process that is energy-saving, efficient, simple to operate, and has stable product quality.

[0004] The MVR-OSLO continuous crystallization system is an existing crystallization technology with the characteristics of low energy consumption and high degree of continuity. The MVR-OSLO continuous crystallization system combines mechanical vapor recompression technology (MVR) with the OSLO type crystallizer (Oslo type crystallizer). Among them, the MVR technology increases the temperature and pressure of secondary steam by mechanically compressing it, making it a heating steam for recycling, with the characteristics of low energy consumption and low operating cost; the OSLO type crystallizer adopts a partition design to separate the crystallization chamber from the heating chamber, which is connected by an external circulation pipeline, which can realize the effective separation of crystallization and heat transfer, which is conducive to crystal growth.

[0005] The grain size obtained by the MVR-OSLO continuous crystallization system is usually between 0.5mm and 1.5mm. Battery-grade manganese sulfate requires a grain size usually between 0.2mm and 0.3mm. In order to obtain battery-grade manganese sulfate with the MVR-OSLO continuous crystallization system, the supersaturation can be increased by increasing the evaporation rate or lowering the operating temperature, increasing the liquid circulation rate to enhance the shear force generated by natural convection to promote secondary nucleation, and at the same time reducing the seed size and increasing the amount of seed added, shortening the residence time of the crystal in the crystallizer, and appropriately increasing the cooling rate. However, the above measures will lead to a widening of the particle size distribution range and a reduction in the uniformity of the particle size, which will have an adverse effect on the quality of battery-grade manganese sulfate products.

[0006] Therefore, in view of the above technical difficulties, it is difficult to apply the MVR-OSLO continuous crystallization system to the preparation of battery-grade manganese sulfate. Summary of the invention

[0007] The purpose of the present invention is to provide a method and device for evaporating and crystallizing battery-grade manganese sulfate, so as to solve the problem of applying the MVR-OSLO continuous crystallization system to prepare battery-grade manganese sulfate and obtaining a better uniformity of particle size distribution.

[0008] In a first aspect, a method for evaporating and crystallizing a battery-grade manganese sulfate is provided, comprising: feeding a manganese sulfate liquid into a preheater for preheating, wherein the preheater uses steam condensed water discharged from a heating chamber of a single-stage MVR-OSLO continuous crystallization system as a heat source to preheat the manganese sulfate liquid; feeding the preheated manganese sulfate liquid into a single-stage MVR-OSLO continuous crystallization system for evaporation and crystallization, and then outputting a crystal suspension from a product outlet of the crystallization chamber of the single-stage MVR-OSLO continuous crystallization system; feeding the crystal suspension into a cyclone for primary solid-liquid separation, so that fine crystals that do not reach a preset grain size are returned to the single-stage MVR-OSLO continuous crystallization system with the separated primary mother liquor for re-evaporation and crystallization, and qualified crystals that reach a preset grain size are output from the residual slurry; feeding the residual slurry into a centrifuge for secondary solid-liquid separation to obtain battery-grade manganese sulfate to be dried, and returning the separated secondary mother liquor to the single-stage MVR-OSLO continuous crystallization system for re-evaporation and crystallization, and then drying the battery-grade manganese sulfate to be dried, and finally obtaining a battery-grade manganese sulfate product.

[0009] In a second aspect, a battery-grade manganese sulfate evaporation and crystallization device is provided, including: a preheater that preheats the manganese sulfate feed liquid using the steam condensate discharged from the heating chamber of a single-stage MVR-OSLO continuous crystallization system as a heat source; a single-stage MVR-OSLO continuous crystallization system that evaporates and crystallizes the preheated manganese sulfate feed liquid, and then outputs a crystal suspension from the product outlet of the crystallization chamber of the single-stage MVR-OSLO continuous crystallization system; a hydrocyclone that performs primary solid-liquid separation on the crystal suspension, enabling fine crystals that do not reach the preset crystal grain size to return to the single-stage MVR-OSLO continuous crystallization system with the separated primary mother liquor for re-evaporation and crystallization, while the qualified crystal grains that reach the preset crystal grain size are output from the surplus slurry; a centrifuge that performs secondary solid-liquid separation on the surplus slurry to obtain battery-grade manganese sulfate to be dried, and the separated secondary mother liquor returns to the single-stage MVR-OSLO continuous crystallization system for re-evaporation and crystallization; the battery-grade manganese sulfate to be dried is dried to obtain a battery-grade manganese sulfate product.

[0010] The battery-grade manganese sulfate evaporation and crystallization method and device of the present invention preheat the manganese sulfate feed liquid using the steam condensate discharged from the heating chamber of a single-stage MVR-OSLO continuous crystallization system, and utilize mechanical vapor recompression technology to achieve steam recycling, significantly reducing energy consumption and operating costs; by using a hydrocyclone to perform primary solid-liquid separation on the crystal suspension and returning the fine crystals that do not reach the preset crystal grain size to the system with the primary mother liquor, combined with the two-stage solid-liquid separation of the hydrocyclone and the centrifuge and the return mechanism of the primary mother liquor and the secondary mother liquor, it not only realizes precise control of the crystal grain size but also ensures product purity and yield; at the same time, the single-stage MVR-OSLO continuous crystallization system has a simple structure, and the partition design of the OSLO-type crystallizer is conducive to the effective separation of crystallization and heat transfer, realizing continuous production, improving production efficiency, reducing equipment investment and maintenance costs, and ensuring the stability of product quality.

[0011] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments. The additional aspects and advantages provided by the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through practice. Description of the Drawings

[0012] The drawings forming a part of this specification are used to assist in the understanding of the present invention. The content provided in the drawings and the related explanations in this specification can be used to explain the present invention, but do not constitute an improper limitation to the present invention.

[0013] Figure 1 It is a schematic structural diagram of a battery-grade manganese sulfate evaporation and crystallization device according to an embodiment of the present invention. Detailed Embodiments

[0014] The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0015] The technical solutions and technical features provided in each section, including the following description, can be combined with each other without conflict. In addition, where possible, these technical solutions, technical features and related combinations can be assigned specific technical themes and protected by relevant patents.

[0016] The embodiments of the present invention involved in the following description are generally only a part of the embodiments rather than all the embodiments. Based on these embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of patent protection.

[0017] The terms "include", "comprises", "have" and any variations thereof in this specification and the corresponding claims and related parts are intended to cover non-exclusive inclusions. Other related terms and units can be reasonably interpreted based on the relevant content provided in this specification.

[0018] Figure 1 This is a schematic diagram of the structure of a battery-grade manganese sulfate evaporation and crystallization device according to an embodiment of the present invention. Figure 1 As shown, the battery-grade manganese sulfate evaporation crystallization equipment includes: a single-stage MVR-OSLO continuous crystallization system, a preheater 1, a cyclone 9, a centrifuge 10, and a disk dryer 11.

[0019] The single-stage MVR-OSLO continuous crystallization system includes a heating chamber 4 , a separation chamber 5 , a crystallization chamber 6 , a circulation pump 7 , a slurry pump 8 , a steam scrubber 15 , and a compressor 14 .

[0020] An external circulation pipeline is provided between the crystallization chamber 6 and the heating chamber 4, and a first inlet is provided on the external circulation pipeline for inputting manganese sulfate liquid.

[0021] A condensate bucket 3 and a condensate pump 2 are provided between the preheater 1 and the heating chamber 4. The steam condensate discharged from the heating chamber 4 enters the condensate bucket 3 and is then supplied to the preheater 1 through the condensate pump 2.

[0022] The preheater 1 uses the steam condensed water discharged from the heating chamber 4 of the single-stage MVR-OSLO continuous crystallization system as a heat source to preheat the manganese sulfate liquid.

[0023] The above-mentioned single-stage MVR-OSLO continuous crystallization system is used to evaporate and crystallize the preheated manganese sulfate liquid, and then output the crystal suspension from the product outlet of the crystallization chamber 6 of the single-stage MVR-OSLO continuous crystallization system.

[0024] The cyclone 9 is used to perform a solid-liquid separation on the crystal suspension, so that the fine crystals that do not reach the preset grain size are returned to the single-stage MVR-OSLO continuous crystallization system with the separated primary mother liquor for re-evaporation and crystallization, and the qualified grains that reach the preset grain size are output from the residual slurry.

[0025] The centrifuge 10 is used to perform secondary solid-liquid separation on the residual slurry to obtain battery-grade manganese sulfate to be dried, and the separated secondary mother liquor is returned to the single-stage MVR-OSLO continuous crystallization system for re-evaporation and crystallization.

[0026] The disk dryer 11 is used to dry the battery-grade manganese sulfate to be dried, and finally a battery-grade manganese sulfate product is obtained from the disk dryer 11.

[0027] Specifically, the preheated manganese sulfate liquid enters the first inlet on the external circulation pipeline, and then enters the separation chamber 5 after heat exchange with water vapor through the heating chamber 4 under the action of the circulation pump 7. The manganese sulfate liquid evaporates water in the separation chamber 5 to obtain smaller crystals. The crystals enter the crystallization chamber 6 under the action of gravity to continue growing. The crystallization chamber 6 allows the crystals to have enough growth time to obtain grains of the required particle size. The water evaporated from the separation chamber 5 is washed by the steam washing tower 15 and then enters the compressor 14. After being heated and pressurized, it returns to the heating chamber 4 to continue heating the solution. The preheater 1 and the compressor 14 recover most of the heat of the system, so the system does not need or only needs a small amount of raw steam to be supplemented, reducing the operating cost.

[0028] The battery-grade manganese sulfate evaporation and crystallization equipment uses the steam condensate discharged from the heating chamber of the single-stage MVR-OSLO continuous crystallization system to preheat the manganese sulfate liquid, and uses mechanical steam recompression technology to achieve steam recycling, which significantly reduces energy consumption and operating costs.

[0029] In addition, the cyclone 9 is used to perform a solid-liquid separation on the crystal suspension and the fine crystals that do not reach the preset grain size are returned to the single-stage MVR-OSLO continuous crystallization system with the primary mother liquor. Combined with the two-stage solid-liquid separation of the cyclone 9 and the centrifuge 10 and the primary mother liquor and secondary mother liquor return mechanism, both the precise control of the grain size is achieved and the product purity and yield are guaranteed.

[0030] At the same time, the single-stage MVR-OSLO continuous crystallization system has a simple structure, and the partition design of the OSLO crystallizer is conducive to the effective separation of crystallization and heat transfer, realizing continuous production, improving production efficiency, reducing equipment investment and maintenance costs, and ensuring the stability of product quality.

[0031] Specifically: the single-stage MVR-OSLO continuous crystallization system is operated under the condition of generating grains with a particle size of 0.2 mm-0.3 mm, and the particle size of the qualified grains output by the cyclone 9 is 0.2 mm-0.3 mm;

[0032] The mass flow rate of the primary mother liquid output by the cyclone 9 is controlled to be 30%-40% of the mass flow rate of the crystal suspension output by the single-stage MVR-OSLO continuous crystallization system;

[0033] The mass flow rate of the residual slurry outputted from the cyclone 9 is controlled to be 60%-70% of the mass flow rate of the crystal suspension outputted from the single-stage MVR-OSLO continuous crystallization system.

[0034] By setting the operating conditions of the single-stage MVR-OSLO continuous crystallization system to generate grains with a particle size of 0.2mm-0.3mm, and controlling the qualified grains output by the cyclone 9 to be within the same particle size range, combined with the design of controlling the mass flow rate of the primary mother liquor output by the cyclone 9 to be 30%-40% of the mass flow rate of the crystallization suspension and the mass flow rate of the residual slurry to be 60%-70%, a reasonable material distribution ratio is formed.

[0035] If the mass flow rate of the primary mother liquor output by the cyclone 9 is greater than 40% of the mass flow rate of the crystallization suspension, it will affect the operating stability of the single-stage MVR-OSLO continuous crystallization system. Specifically, it will increase the load of the OSLO type crystallizer, affect the temperature field of the OSLO type crystallizer, reduce production capacity, and increase energy consumption. As shown in the figure, the mass flow rate of the primary mother liquor output by the cyclone 9 is less than 30% of the mass flow rate of the crystallization suspension, and the grading effect of the cyclone 9 is poor and cannot meet the requirements of qualified grains.

[0036] It is particularly important to emphasize that: by combining the single-stage MVR-OSLO continuous crystallization system and the cyclone 9, a closed-loop control system is formed: the single-stage MVR-OSLO continuous crystallization system operates under specific conditions to generate target grains of 0.2 mm-0.3 mm in diameter, and the cyclone 9 outputs qualified grains (0.2 mm-0.3 mm) into the residual slurry through accurate classification, while returning the unqualified fine grains with the primary mother liquor to the system for continued growth. This closed-loop control method of classification-return ensures that an appropriate amount of crystal circulation is always maintained in the system; and by controlling the mass flow rate of the primary mother liquor at 30%-40% of the crystallization suspension and the residual slurry at 60%-70% in a specific ratio design, it is ensured that a sufficient amount of fine crystals are returned to maintain the stable operation of the system, and the load impact on the OSLO type crystallizer caused by excessive return is avoided, thereby achieving stable growth and uniform distribution of battery-grade manganese sulfate crystals.

[0037] In order to obtain 0.2mm-0.3mm manganese sulfate in the MVR-OSLO continuous crystallization system, the supersaturation can be increased by increasing the evaporation rate or lowering the operating temperature, increasing the liquid circulation rate to strengthen the shear force generated by natural convection to promote secondary nucleation, and at the same time reducing the seed particle size and increasing the seed addition amount, shortening the residence time of the crystal in the crystallizer, and appropriately increasing the cooling rate.

[0038] Specifically, in this embodiment, the MVR-OSLO continuous crystallization system is used to obtain manganese sulfate with a diameter of 0.2 mm to 0.3 mm by controlling the evaporation rate in the OSLO crystallizer to 2 to 3 kg water / m 2 h, the operating temperature is maintained at 60-70℃ (5-10℃ lower than the saturation temperature), and the supersaturation is maintained at 1.1-1.2; the system feed liquid circulation ratio is controlled at 4-6 times, the crystallizer residence time is controlled at 30-40 minutes, the cooling rate is 1-2℃ / min, and the feed liquid concentration is maintained at 45-50wt%, and the return temperature is 65-75℃; 0.05-0.1mm seed crystals are added at the initial stage of crystallization, the addition amount is 3-5% of the product mass, and it is replenished every 2-3 hours.

[0039] In addition, a mother liquor discharge pipe is provided on the flow path of the primary mother liquor and / or the secondary mother liquor returning to the single-stage MVR-OSLO continuous crystallization system, and the mother liquor discharge pipe can discharge part of the primary mother liquor and / or the secondary mother liquor without returning to the single-stage MVR-OSLO continuous crystallization system, so as to prevent the continuous enrichment of impurities.

[0040] Specifically, the amount of mother liquor discharged can be controlled between 5% and 15% of the total mass of the returned mother liquor according to the impurity content in the manganese sulfate liquid and the system operation status, which can effectively prevent impurity enrichment and avoid causing a large amount of material loss. The discharge cycle can be set to 8-12 hours / time to avoid causing system fluctuations.

[0041] The primary mother liquor and the secondary mother liquor can enter the single-stage MVR-OSLO continuous crystallization system through a second inlet disposed on the external circulation pipeline and located between the first inlet and the crystallization chamber for evaporation crystallization.

[0042] By arranging the second inlet of the primary mother liquor and the secondary mother liquor at a position between the first inlet of the manganese sulfate liquid and the crystallization chamber on the external circulation pipeline, the returned mother liquor can be fully mixed with the fresh manganese sulfate liquid before entering the crystallization chamber. After passing through the heating chamber and exchanging heat with water vapor, the concentration of the liquid entering the separation chamber can be guaranteed to be uniform and the temperature is appropriate, thereby providing stable crystallization conditions for the single-stage MVR-OSLO continuous crystallization system and facilitating maintaining a good temperature field in the crystallization chamber.

[0043] In addition, the primary mother liquor and the secondary mother liquor can be respectively input into the mother liquor storage device 12, and then the primary mother liquor and the secondary mother liquor stored in the mother liquor storage device 12 are returned to the single-stage MVR-OSLO continuous crystallization system through the mother liquor pump 13 for re-evaporation and crystallization.

[0044] By first inputting the primary mother liquor separated by the cyclone 9 and the secondary mother liquor separated by the centrifuge 10 into the mother liquor storage device 12 for buffering, and then transporting them back to the single-stage MVR-OSLO continuous crystallization system by the mother liquor pump 13, not only the centralized collection and homogenization of the mother liquor are achieved, but also the mother liquor flow rate returning to the system can be controlled by adjusting the delivery rate of the mother liquor pump 13, so that the system can operate more stably. At the same time, the setting of the mother liquor storage device 12 also facilitates the mother liquor discharge operation, which helps to prevent the continuous enrichment of impurities in the system.

[0045] In this embodiment, a single-stage MVR-OSLO continuous crystallization system is used to prepare a battery-grade manganese sulfate product. The feed of the system is a manganese sulfate solution with a mass concentration of 45-50%, a solution temperature of 25° C., and a feed flow rate of 15 tons / hour.

[0046] First, the manganese sulfate liquid is preheated to 65° C. in the preheater 1 . The preheater 1 uses 85° C. steam condensed water from the heating chamber 4 as a heat source. The condensed water is collected in the condensed water bucket 3 and then transported to the preheater 1 by the condensed water pump 2 .

[0047] The preheated manganese sulfate liquid enters the system through the first inlet arranged on the external circulation pipeline. The primary mother liquor and the secondary mother liquor return to the system through the second inlet arranged between the first inlet and the crystallization chamber 6. Under the action of the circulation pump 7, the mixed liquid passes through the heating chamber 4 and exchanges heat with the secondary steam from the compressor 14, and the temperature rises to 95°C.

[0048] After the liquid enters the separation chamber 5, it flashes under reduced pressure (absolute pressure 0.47 bar), and the temperature drops to 80°C, at which time the crystal nuclei begin to form. The evaporated water vapor is defogged by the washing tower 15 and then enters the compressor 14. After being compressed to 2.5 bar, the temperature rises to 125°C and returns to the heating chamber 4 for recycling.

[0049] The crystals stay in the crystallization chamber 6 for about 30-40 minutes and grow to 0.2mm-0.3mm. The crystal suspension is transported to the cyclone 9 through the slurry pump 8 for a solid-liquid separation. The cyclone 9 separates the crystal suspension into two parts: a primary mother liquor (accounting for 35% of the feed mass) and residual slurry (accounting for 65% of the feed mass). The primary mother liquor carries fine crystals less than 0.2mm back to the system.

[0050] The residual pulp enters the centrifuge 10 for secondary solid-liquid separation to obtain wet manganese sulfate crystals with a moisture content of 8% and secondary mother liquor. The wet crystals are dried by a tray dryer 11 to a moisture content of less than 0.5%, and then the finished product is obtained. The primary mother liquor and the secondary mother liquor first enter the mother liquor storage device 12, and the external discharge amount before returning to the system by the mother liquor pump 13 is 10% of the total mass of the returned mother liquor, and the external discharge is carried out once every 8 hours.

[0051] When the system operates continuously, the production capacity can reach 300 tons per day. More than 90% of the product particle size is distributed in the range of 0.2 mm - 0.3 mm, the product purity is ≥99.7%, and the steam consumption of the system is only 0.05 tons per ton of product.

[0052] The above describes the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of the present invention.

Claims

1. A battery-grade manganese sulfate evaporation and crystallization method, characterized in that: include: The manganese sulfate liquid is sent to a preheater for preheating, wherein the preheater uses steam condensed water discharged from a heating chamber of a single-stage MVR-OSLO continuous crystallization system as a heat source to preheat the manganese sulfate liquid; The preheated manganese sulfate liquid is fed into a single-stage MVR-OSLO continuous crystallization system for evaporation crystallization, and then a crystal suspension is output from a product outlet of a crystallization chamber of the single-stage MVR-OSLO continuous crystallization system; The crystal suspension is input into a cyclone for solid-liquid separation, so that fine crystals that do not reach the preset grain size are returned to the single-stage MVR-OSLO continuous crystallization system with the separated primary mother liquor for re-evaporation and crystallization, and qualified crystals that reach the preset grain size are output from the residual slurry; The residual slurry is input into a centrifuge for secondary solid-liquid separation to obtain battery-grade manganese sulfate to be dried, and the separated secondary mother liquor is returned to the single-stage MVR-OSLO continuous crystallization system for re-evaporation and crystallization, and then the battery-grade manganese sulfate to be dried is dried to finally obtain a battery-grade manganese sulfate product.

2. A battery-grade manganese sulfate evaporation and crystallization method as claimed in claim 1, characterized in that: The single-stage MVR-OSLO continuous crystallization system is operated under the condition of generating grains with a particle size of 0.2 mm-0.3 mm, and the particle size of the qualified grains output by the cyclone is 0.2 mm-0.3 mm; The mass flow rate of the primary mother liquor outputted by the cyclone is controlled to be 30%-40% of the mass flow rate of the crystal suspension outputted by the single-stage MVR-OSLO continuous crystallization system; The mass flow rate of the residual slurry outputted from the cyclone is controlled to be 60%-70% of the mass flow rate of the crystal suspension outputted from the single-stage MVR-OSLO continuous crystallization system.

3. A battery-grade manganese sulfate evaporation and crystallization method as claimed in claim 1, characterized in that: The primary mother liquor and the secondary mother liquor are respectively input into a mother liquor storage device, and then the primary mother liquor and the secondary mother liquor stored in the mother liquor storage device are returned to the single-stage MVR-OSLO continuous crystallization system through a mother liquor pump for re-evaporation and crystallization.

4. A battery-grade manganese sulfate evaporation and crystallization method as claimed in claim 1, characterized in that: The preheated manganese sulfate liquid enters the single-stage MVR-OSLO continuous crystallization system through a first inlet arranged on an external circulation pipeline connected between the crystallization chamber and the heating chamber for evaporation crystallization; The primary mother liquor and the secondary mother liquor enter the single-stage MVR-OSLO continuous crystallization system through a second inlet disposed on the external circulation pipeline and located between the first inlet and the crystallization chamber for evaporation and crystallization.

5. A battery-grade manganese sulfate evaporation and crystallization method as claimed in claim 1, characterized in that: A mother liquor discharge pipe is provided on the flow path of the primary mother liquor and / or the secondary mother liquor returning to the single-stage MVR-OSLO continuous crystallization system, and the mother liquor discharge pipe can discharge part of the primary mother liquor and / or the secondary mother liquor without returning to the single-stage MVR-OSLO continuous crystallization system.

6. A battery-grade manganese sulfate evaporation and crystallization method according to claim 1, characterized in that: The battery grade manganese sulfate to be dried is dried by a disk dryer.

7. Battery-grade manganese sulfate evaporation and crystallization equipment, characterized by: include: A preheater, which uses the steam condensate discharged from the heating chamber of the single-stage MVR-OSLO continuous crystallization system as a heat source to preheat the manganese sulfate liquid; A single-stage MVR-OSLO continuous crystallization system is used to evaporate and crystallize the preheated manganese sulfate solution, and then output the crystal suspension from the product outlet of the crystallization chamber of the single-stage MVR-OSLO continuous crystallization system; A cyclone is used to perform a solid-liquid separation on the crystal suspension, so that the fine crystals that do not reach the preset grain size are returned to the single-stage MVR-OSLO continuous crystallization system with the separated primary mother liquor for re-evaporation and crystallization, and the qualified crystals that reach the preset grain size are output from the residual slurry; A centrifuge is used to perform secondary solid-liquid separation on the residual slurry to obtain battery-grade manganese sulfate to be dried, and the separated secondary mother liquor is returned to the single-stage MVR-OSLO continuous crystallization system for re-evaporation and crystallization; The battery-grade manganese sulfate to be dried is dried to obtain a battery-grade manganese sulfate product.

8. The battery-grade manganese sulfate evaporation and crystallization equipment according to claim 7, characterized in that: The single-stage MVR-OSLO continuous crystallization system is operated under the condition of generating grains with a particle size of 0.2 mm-0.3 mm, and the particle size of the qualified grains output by the cyclone is 0.2 mm-0.3 mm; The mass flow rate of the primary mother liquor outputted by the cyclone is controlled to be 30%-40% of the mass flow rate of the crystal suspension outputted by the single-stage MVR-OSLO continuous crystallization system; The mass flow rate of the residual slurry outputted from the cyclone is controlled to be 60%-70% of the mass flow rate of the crystal suspension outputted from the single-stage MVR-OSLO continuous crystallization system.

9. The battery-grade manganese sulfate evaporation and crystallization equipment according to claim 7, characterized in that: A mother liquor discharge pipe is provided on the flow path of the primary mother liquor and / or the secondary mother liquor returning to the single-stage MVR-OSLO continuous crystallization system, and the mother liquor discharge pipe can discharge part of the primary mother liquor and / or the secondary mother liquor without returning to the single-stage MVR-OSLO continuous crystallization system.

10. The battery-grade manganese sulfate evaporation and crystallization equipment according to claim 7, characterized in that: It also includes a disk dryer for drying the battery-grade manganese sulfate to be dried.

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