Apparatus for concentrating fine particle slurry, and apparatus and method for producing fine particle powder

Abstract

To provide an apparatus capable of stably concentrating fine particle slurry even in a high concentration region.SOLUTION: An apparatus for concentrating fine particle slurry includes: a slurry tank 30 for storing fine particle slurry; a cleaning liquid supplying device 38 for supplying cleaning liquid to the slurry tank 30; a stirring type crossflow filtration device 6 for concentrating the fine particle slurry; a first flow channel 56 for supplying the fine particle slurry stored in the slurry tank 30 to the stirring type crossflow filtration device 6; a second flow channel 72 for returning the concentrated slurry discharged from the stirring type crossflow filtration device 6 to the slurry tank 30; a density sensor 66 for generating a signal according to the density of the concentrated slurry discharged from the stirring type crossflow filtration device 6; and a control device 67 for controlling the amount of the cleaning liquid supplied by the cleaning liquid supply device 38 on the basis of the density sensor 66.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus for concentrating a fine particle slurry, and an apparatus and method for producing a fine particle powder, and more particularly to an apparatus and method suitable for producing a precursor of a positive electrode active material for a secondary battery, for example. [Background technology]

[0002] In the production of fine particle powders, for example, in the production of secondary battery positive electrode active material precursors, it has become desirable in recent years to make the particle size of the fine particles as small as possible in order to improve the performance of the final product, and a production method is generally used which includes a step of obtaining a stock slurry containing a precipitate component mainly composed of a transition metal hydroxide by contacting a solution containing a transition metal element with an alkali, a step of concentrating the precipitate component in the slurry to obtain a concentrated slurry, and a step of drying the concentrated slurry to obtain a fine particle powder.

[0003] However, in this type of manufacturing method for fine particle powder, when fine particles are obtained by adjusting the conditions of the manufacturing process of the raw slurry, the filtration resistance of the cake layer formed during filtration with a filter in the filtration and washing process becomes very large, making it difficult to apply cake filtration methods such as commonly used filter presses (pressure filtration).

[0004] In addition, with the filter press method, it is difficult to achieve a uniform cake thickness throughout the entire filter chamber. When attempting to employ a displacement washing method in which washing water is passed through a cake layer of non-uniform thickness, the washing water tends to concentrate and pass through areas where the cake is thin, while the washing water is less likely to pass through areas where the cake is thick. As a result, unevenness is unavoidable with each washing, making it difficult to wash the entire cake layer uniformly.

[0005] In view of this, there have been proposed methods disclosed in Patent Document 1 or Patent Document 2. The methods of Patent Documents 1 and 2 include a step of contacting a solution containing a transition metal element with an alkali to obtain a stock slurry containing a precipitate component mainly composed of a transition metal hydroxide, concentrating the precipitate component in the slurry by cross-flow filtration, and drying the concentrated slurry by a hot air drying method in which hot air is blown onto the concentrated slurry.

[0006] The cross-flow filtration is a method of filtering the raw slurry while flowing it parallel to the inner wall of the filter. The shear force of the slurry flowing parallel to the inner wall of the filter prevents solids from accumulating as a cake layer on the filter surface, which has the advantage that clogging is unlikely to occur even when the raw slurry contains fine particles. The cross-flow filtration method can be implemented using hollow fiber membranes, tubular membranes, spiral membrane modules, rotary filters equipped with stirring blades that stir the filter surface, and the like. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-87039 A [Patent Document 2] JP 2012-99470 A Summary of the Invention [Problem to be solved by the invention]

[0008] In the methods of Patent Documents 1 and 2, it is preferable to carry out a concentration operation so that the slurry in the system is as concentrated as possible, taking into consideration the filtration and washing operations. However, if it is concentrated too much, the fluidity of the slurry circulating in the system becomes poor, making it impossible to transport it using a pump or the like, resulting in a clogging problem. Therefore, Patent Document 1 proposes a method of controlling the concentration state of the slurry circulating in the system by monitoring the current value and torque of the motor that drives the rotating blades of a rotary crossflow filtration device. However, there is no linear relationship between the viscosity of the slurry circulating in the system and the current value and torque of the motor that drives the rotating blades, and especially when the slurry is highly concentrated, the current value and torque can suddenly change unstably due to a slight difference in concentration, making it difficult to stably control the high concentration state with the current value and torque of the motor. [Means for solving the problem]

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a concentrating device for fine particle slurry, which is capable of stably concentrating fine particle slurry even in a high concentration range, and a manufacturing device and manufacturing method for fine particle powder.

[0010] The apparatus for concentrating a fine particle slurry according to a first aspect of the present invention is characterized by comprising a slurry tank for storing the fine particle slurry, a cleaning liquid supplying device for supplying a cleaning liquid to the slurry tank, an agitated cross-flow filtration device for concentrating the fine particle slurry, a first flow path for supplying the fine particle slurry stored in the slurry tank to the agitated cross-flow filtration device, a second flow path for returning the concentrated slurry discharged from the agitated cross-flow filtration device to the slurry tank, a density sensor for generating a signal corresponding to the density of the concentrated slurry discharged from the agitated cross-flow filtration device, and a control device for controlling the amount of the cleaning liquid supplied to the slurry tank by the cleaning liquid supplying device based on the output of the density sensor.

[0011] According to the device for concentrating fine particle slurry of the first aspect, the fine particle slurry stored in the slurry tank is supplied to the stirring cross-flow filtration device through the first flow path to be concentrated, while the concentrated slurry discharged from the stirring cross-flow filtration device is returned to the slurry tank through the second flow path as necessary. During this process, the density of the concentrated slurry discharged from the stirring cross-flow filtration device is measured by the density sensor, and the amount of cleaning liquid supplied to the slurry tank by the cleaning liquid supply device is controlled based on the output of the density sensor. Therefore, compared to a means for monitoring the stirring torque of the slurry, the use of the density sensor makes it possible to correctly grasp the viscosity change of the slurry even in a high concentration range, and to manage the viscosity with high accuracy, thereby making it possible to stably concentrate the fine particle slurry even in a high concentration range while suppressing blockage of the flow path.

[0012] A microparticle slurry concentrating apparatus according to aspect 2 of the present invention is the apparatus according to aspect 1, further comprising a conductivity sensor that generates a signal corresponding to the conductivity of the filtrate discharged from the stirred cross-flow filtration apparatus, and the control device switches or instructs the timing of switching from the initial concentration step (A) to the dilution and washing step (B) below, or from the final concentration step (C) to the discharge step (D) below based on the output of the density sensor, while switching or instructing the timing of switching from the dilution and washing step (B) to the final concentration step (C) below based on the output of the density sensor and the output of the conductivity sensor. (A) an initial concentration step of supplying the fine particle slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating mother liquor in the fine particle slurry and obtaining an initial concentrated slurry; (B) a dilution and washing step of supplying a washing liquid to the slurry tank by the washing liquid supply device, supplying the initially concentrated slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby diluting and washing the initially concentrated slurry to obtain a washing slurry; (C) a final concentration step of stopping the supply of the cleaning liquid to the slurry tank by the cleaning liquid supply device, supplying the cleaning slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating the cleaning liquid from the cleaning slurry and obtaining a final concentrated slurry; and (D) discharging the final concentrated slurry from the agitated cross-flow filtration apparatus.

[0013] According to the microparticle slurry concentrating device of aspect 2, the slurry can be stably concentrated even in a high concentration range by switching between an initial concentration step (A) for obtaining an initial concentrated slurry, a dilution and washing step (B) for diluting and washing the initial concentrated slurry to obtain a washed slurry, a final concentration step (C) for concentrating the washed slurry to obtain a final concentrated slurry, and a discharge step (D) for discharging the final concentrated slurry, based on the output of the density sensor, or based on the output of the density sensor and the output of the conductivity sensor.

[0014] A third aspect of the present invention relates to an apparatus for concentrating a fine particle slurry according to the first aspect, and further includes a second density sensor for generating a signal corresponding to the density of the filtrate discharged from the stirring type cross-flow filtration device, The device for concentrating a microparticle slurry as described in claim 1, characterized in that the control device switches, or instructs the timing of switching, from the initial concentration process (A) to the dilution and washing process (B), from the dilution and washing process (B) to the final concentration process (C), or from the final concentration process (C) to the discharge process (D), based on outputs from the density sensor and the second density sensor. (A) an initial concentration step of supplying the fine particle slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating mother liquor in the fine particle slurry and obtaining an initial concentrated slurry; (B) a dilution and washing step of supplying a washing liquid to the slurry tank by the washing liquid supply device, supplying the initially concentrated slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby diluting and washing the initially concentrated slurry to obtain a washing slurry; (C) a final concentration step of stopping the supply of the cleaning liquid to the slurry tank by the cleaning liquid supply device, supplying the cleaning slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating the cleaning liquid from the cleaning slurry and obtaining a final concentrated slurry; and (D) discharging the final concentrated slurry from the agitated cross-flow filtration apparatus.

[0015] According to the microparticle slurry concentrating device of aspect 3, the slurry can be stably concentrated even in a high concentration range by switching between an initial concentration step (A) for obtaining an initial concentrated slurry, a dilution and washing step (B) for diluting and washing the initial concentrated slurry to obtain a washed slurry, a final concentration step (C) for concentrating the washed slurry to obtain a concentrated slurry, and a discharge step (D) for discharging the final concentrated slurry, based on the outputs of the density sensor and the second density sensor.

[0016] The microparticle slurry concentrating apparatus of aspect 4 of the present invention is characterized in that in aspect 2 or 3, the control device performs feedback control in the dilution cleaning process based on the output of the density sensor, by reducing or stopping the supply of the cleaning liquid by the cleaning liquid supply device if the density of the concentrated slurry is lower than the lower limit of the target density range, and increasing or starting the supply of the cleaning liquid by the cleaning liquid supply device if the density of the concentrated slurry is higher than the upper limit of the target density range.

[0017] According to the device for concentrating a fine particle slurry of the fourth aspect, the supply amount of the cleaning liquid is feedback-controlled based on the output of the density sensor, whereby the density of the concentrated slurry discharged from the stirring type cross-flow filtration device can be kept within a constant range, and the slurry can be stably concentrated even in a high concentration range.

[0018] The microparticle slurry concentrating apparatus of aspect 5 of the present invention is characterized in that in aspect 2 or 4, the control device, in the initial concentration step (A), compares the output of the density sensor with a slurry density corresponding to a predetermined value within a solids concentration range of 35 to 65 wt% of the concentrated slurry, and switches to the dilution washing step (B) when the density sensor reaches a slurry density corresponding to the predetermined value, or indicates the timing for switching to the dilution washing step (B).

[0019] According to the microparticle slurry concentrating device of aspect 5, the control device makes it possible to switch to the dilution and washing process (B) in the initial concentration step (A) when the solids concentration of the concentrated slurry reaches a predetermined value within the range of 35 to 65 wt% based on the output of the density sensor, thereby enabling a smooth transition from the initial concentration step (A) to the dilution and washing process (B) at an appropriate time and improving the washing efficiency.

[0020] A microparticle slurry concentrating apparatus according to aspect 6 of the present invention is characterized in that in aspect 3, the control device switches to the dilution and washing process (B) when the solids concentration of the concentrated slurry reaches a predetermined value within the range of 35 to 65 wt% based on the outputs of the density sensor and the second density sensor in the initial concentration process (A), or indicates the timing for switching to the dilution and washing process (B).

[0021] According to the microparticle slurry concentrating device of aspect 6, the control device enables the initial concentration step (A) to be switched to the dilution and washing step (B) when the solids concentration of the concentrated slurry reaches a predetermined value within the range of 35 to 65 wt% based on the outputs of the density sensor and the second density sensor, thereby enabling a smooth transition from the initial concentration step (A) to the dilution and washing step (B) at an appropriate time and improving the washing efficiency.

[0022] The microparticle slurry concentrating apparatus of aspect 7 of the present invention is characterized in that in any of aspects 2, 4 and 5, the control device, in the final concentration step, compares the output of the density sensor with a slurry density corresponding to a predetermined value within the range of a solids concentration of the concentrated slurry of 50 to 65 wt%, and transitions to the discharge step (D) when the density sensor reaches a slurry density corresponding to the predetermined value.

[0023] According to the device for concentrating fine particle slurry of the seventh aspect, in the final concentration step (C), the control device stops returning the concentrated slurry to the slurry tank and transitions to the discharge step (D) when the solid content of the concentrated slurry reaches a predetermined value within a range of 50 to 65 wt% based on the output of the density sensor, and the transition from the final concentration step (C) to the discharge step (D) can be smoothly performed at an appropriate timing. In addition, the amount of water removed in the drying step after the discharge step (D) can be reduced as much as possible, and the energy cost required for drying can also be suppressed.

[0024] The microparticle slurry concentrating apparatus of aspect 8 of the present invention is characterized in that in any of aspects 3, 4 and 6, the control device transitions to the discharge step (D) when, in the final concentration step (C), the solids concentration of the concentrated slurry reaches a predetermined value within the range of 50 to 65 wt% based on the output of the density sensor and the second density sensor.

[0025] According to the device for concentrating fine particle slurry of the eighth aspect, in the final concentration step (C), the control device stops returning the concentrated slurry to the slurry tank and transitions to the discharge step (D) when the solid content of the concentrated slurry reaches a predetermined value within a range of 50 to 65 wt% based on the outputs of the density sensor and the second density sensor, and the transition from the final concentration step (C) to the discharge step (D) can be smoothly performed at an appropriate timing. In addition, the amount of water removed in the drying step after the discharge step (D) can be reduced as much as possible, and the energy cost required for drying can also be suppressed.

[0026] A microparticle slurry concentrating device according to aspect 9 of the present invention is characterized in that, in any one of aspects 1 to 8, the density sensor is a vibrating in-line density sensor having a vibrator in contact with the concentrated slurry and a controller that vibrates the vibrator and measures its resonant frequency. Furthermore, in any one of aspects 3, 6, and 8, the second density sensor may be a vibrating in-line density sensor having a vibrator in contact with the concentrated slurry and a controller that vibrates the vibrator and measures its resonant frequency.

[0027] According to the device for concentrating a particulate slurry of the ninth aspect, the vibrator in contact with the concentrated slurry is vibrated by a vibration type density sensor, and the resonant frequency is measured as a function of the density of the concentrated slurry, so that the density of the concentrated slurry can be measured with high accuracy without delay even if the concentrated slurry is highly concentrated and highly viscous, and thus the particulate slurry can be stably concentrated even in a high concentration range while preventing clogging by the concentrated slurry. The same applies when the second density sensor is a vibration type in-line density sensor.

[0028] A microparticle slurry concentrating apparatus according to aspect 10 of the present invention is characterized in that in any one of aspects 1 to 9, the stirred cross-flow filtration apparatus has a slurry chamber and a filtrate chamber separated by a filter, an agitator arranged along the filter in the slurry chamber, and a drive unit that moves the agitator along the filter to prevent the deposition of microparticles on the surface of the filter, and concentrates the microparticle slurry passing through the slurry chamber.

[0029] According to the microparticle slurry concentrating apparatus of aspect 10, the agitation cross-flow filtration apparatus having the above-mentioned configuration makes it possible to produce concentrated slurry in a high concentration range, and while preventing clogging of the high concentration slurry, it is possible to increase production efficiency in the initial concentration process, dilution washing process, final concentration process, and drying process, and also reduce energy costs.

[0030] An apparatus for concentrating a fine particle slurry according to an eleventh aspect of the present invention is characterized in that, in any one of the first to tenth aspects, the fine particles are a precursor of a positive electrode material for a secondary battery.

[0031] According to the microparticle slurry concentrating device of embodiment 11, even when the average particle diameter of the microparticles is extremely small, for example, 7 μm or less, the microparticle slurry can be stably concentrated even in a high concentration range, and a positive electrode material precursor for secondary batteries having a small average particle diameter can be stably obtained.

[0032] A manufacturing apparatus for fine particle powder according to a twelfth aspect of the present invention comprises a fine particle slurry concentrating apparatus according to any one of aspects 1 to 11, and an agitating heat transfer drying apparatus for drying the concentrated slurry supplied from the fine particle slurry concentrating apparatus, the agitating heat transfer drying apparatus comprising a casing having an inlet formed at one end and an outlet formed at the other end, a plurality of rotating shafts arranged within the casing such that they can rotate about their axes and the axes are parallel to each other, agitating blades fixed to each of the rotating shafts at intervals in the axial direction and such that the agitating blades of each rotating shaft overlap partially when viewed in the axial direction, and a heating mechanism for heating the agitating blades, and characterized in that, by rotating the rotating shaft, the heated agitating blades heat the concentrated slurry supplied from the inlet and transport it to the outlet hole, during which the concentrated slurry is dried and converted into fine particle powder.

[0033] According to the fine particle powder manufacturing device of the embodiment 12, even when the average particle diameter of the fine particles is extremely small, for example, 7 μm or less, the fine particle slurry can be stably concentrated even in a high concentration range, and fine particle powder with a small average particle diameter can be stably manufactured. In addition, the stirring heat transfer drying device evaporates moisture by conductive heat transfer by contacting the slurry with the heated stirring blade while rotating, so that it is also possible to reduce energy costs.

[0034] A method for producing fine particle powder according to aspect 13 of the present invention includes a dilution, washing and filtration process in which a washing liquid is added to a slurry containing fine particles having a particle size of 7 μm or less and a mother liquor, and the resulting slurry is filtered using an agitation cross-flow filtration device to obtain a washing slurry; a concentration process in which the washing slurry is concentrated using the agitation cross-flow filtration device to obtain a concentrated slurry; and a drying process in which the concentrated slurry is heated and dried to obtain fine particle powder, wherein the dilution, washing and filtration process measures the density of the washing slurry with a density sensor, and if the density of the washing slurry measured by the density sensor is lower than the lower limit of a target range, the supply amount of the washing liquid in the dilution, washing and filtration process is reduced or the supply is stopped, and if the density of the washing slurry measured by the density sensor is higher than the upper limit of the target range, the supply amount of the washing liquid in the dilution, washing and filtration process is increased or the supply is started, thereby performing feedback control.

[0035] According to the method for producing fine particle powder of aspect 13, even though the average particle size of the fine particles is extremely small at 7 μm or less, the use of a density sensor makes it possible to accurately grasp the change in viscosity of the slurry even in high concentration ranges, compared to means such as monitoring the stirring torque of the slurry, and it is possible to stably concentrate the slurry even in high concentration ranges while suppressing clogging, making it possible to stably produce fine particle powder with a small average particle size. Effect of the Invention

[0036] As described above, according to the microparticle slurry concentrating device, microparticle powder manufacturing device and manufacturing method of each aspect of the present invention, the density sensor accurately detects the viscosity change of the slurry even in a high concentration range, and the control device controls the amount of cleaning liquid supplied to the slurry tank by the cleaning liquid supply device, so that it is possible to stably concentrate the microparticle slurry even in a high concentration range while suppressing blockage of the filter and the associated flow paths. [Brief description of the drawings]

[0037] [Figure 1] 1 is a block diagram showing a manufacturing apparatus for fine particle powder according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a block diagram showing a particulate slurry production apparatus according to the embodiment. [Diagram 3] FIG. 4 is a cross-sectional view showing the stirring type cross-flow filtration device, a density sensor, a conductivity sensor, and a second density sensor in the embodiment. [Figure 4] FIG. 2 is a side cross-sectional view showing the drying device in the embodiment. [Diagram 5] FIG. 2 is a plan view showing the drying device in the embodiment with the top plate removed. [Figure 6] FIG. 2 is a front cross-sectional view showing the drying device in the embodiment. [Figure 7] 4 is a flowchart showing an example of process switching control in the first embodiment. [Figure 8] 10 is a flowchart showing an example of process switching control in the second embodiment. [Figure 9] 4 is a graph showing the operation of the control device in the embodiment. [Figure 10] 10 is a graph showing another example of the operation of the control device in the embodiment. [Figure 11] 10 is a graph showing another example of the operation of the control device in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Hereinafter, a manufacturing apparatus 1 for fine-particle powder according to one embodiment of the present invention will be described in detail. The manufacturing apparatus 1 for fine-particle powder according to this embodiment includes a fine-particle slurry manufacturing apparatus 2 for manufacturing a fine-particle slurry containing fine particles having a particle diameter of 7 μm or less by reacting a plurality of raw materials in a mother liquor in which a swirling flow is generated in a crystallizer 10, a slurry tank 30 for washing the fine-particle slurry obtained in the fine-particle slurry manufacturing apparatus 2 by adding a washing liquid according to the processing stage while stirring the fine-particle slurry, an agitation type cross-flow filtration apparatus 6 for concentrating the fine-particle slurry or washing slurry sent from the slurry tank 30 by removing a part of the mother liquor and the washing liquid, and a drying apparatus 8 for transferring the concentrated slurry after the final concentration is completed in the agitation type cross-flow filtration apparatus 6 while mixing it with the wet powder previously held in a casing 92 by a heated agitation blade and drying it by conductive heat transfer.

[0039] [Crystallizer] As shown in FIG. 2, the crystallizer 10 has a long and thin cylindrical reaction vessel 116, the upstream side of which is cylindrical, and the downstream side of which is a coaxial and conical tapered section 116A that narrows toward the downstream side. Inside the reaction vessel 116, a cylindrical outer tube 110 is coaxially arranged so as to reach the tapered section 116A from the upstream end, and the upstream end of the outer tube 110 opens to the upstream end of the reaction vessel 116. A first inner tube 112 and a second inner tube 114 are inserted into the outer tube 110, the first inner tube 112 protruding from the downstream end of the outer tube 110, and the second inner tube 114 protruding from the downstream end of the outer tube 110 longer than the first inner tube 112. A first raw material 12A is supplied into the reaction vessel 116 from the first inner tube 112, and a second raw material 12B is supplied from the second inner tube 114. If necessary, the mother liquor 12C can be supplied into the reaction vessel 116 through gaps between the outer tube 110 and each of the first inner tube 112 and the second inner tube 114.

[0040] An inlet 115 is formed on the outer periphery of the upstream end of the reaction vessel 116, and by blowing the reaction liquid from this inlet 115 at high speed, a swirling flow is generated in the reaction vessel 116, and the rotation speed increases as the inner diameter narrows at the tapered portion 116A, and the vortex is discharged from the discharge hole 14. The outer tube 110, the first inner tube 112, and the second inner tube 114 are located at the center of the swirling flow, and the first raw material 12A from the first inner tube 112 and the second raw material 12B from the second inner tube 114 are mixed while being vigorously stirred in the central region R of the swirling flow in the tapered portion 116A. In this mixing process, the first raw material 12A and the second raw material 12B are mixed and reacted at high speed, and the reaction product is generated as fine particles with a very small particle size, and flows out from the discharge hole 14 together with the reaction liquid.

[0041] A conduit 16 is connected to the discharge hole 14, and the reaction liquid containing the fine particles is supplied to the reservoir 18 through the conduit 16. A flow rate control valve 118 is provided upstream of the conduit 16 connected to the discharge hole 14, and is opened and closed by a drive unit 120 to adjust the outflow rate of the reaction liquid from the discharge hole 14. The drive unit 120 is controlled manually or automatically according to the indicated value of a pressure gauge 122 that measures the inflow pressure from the inlet 115. When the value of the pressure gauge 122 is high, the opening of the flow rate control valve 118 is increased to promote the outflow of the reaction liquid, and when the value of the pressure gauge 122 is low, the opening of the flow rate control valve 118 is decreased to suppress the outflow of the reaction liquid. This allows the crystallization of the fine particles in the reaction vessel 116 to be performed appropriately.

[0042] A stirring blade 128 rotated by a motor 126 is disposed in the reservoir 18 to stir the reaction liquid uniformly and prevent the fine particles from settling. A conduit 20 is connected to the lower end of the reservoir 18, and the slurry containing the fine particles flowing out from the lower end of the reservoir 18 is pressurized by a pump 22, passes through a temperature regulator 124, passes through a conduit 24 and a pressure gauge 122, and is blown into the reaction vessel 116 from an inlet 115. The temperature regulator 124 serves to appropriately adjust the temperature of the reaction liquid in the reaction vessel 116.

[0043] In this embodiment, the types of the first raw material 12A and the second raw material 12B are not limited, but may be any that reacts with the first raw material 12A and the second raw material 12B to precipitate a compound with low solubility. As an example, when producing a secondary battery positive electrode material precursor, a solution containing a transition metal element such as nickel salt is used as the first raw material 12A, and an alkaline solution is used as the second raw material 12B, and the first raw material 12A and the second raw material 12B are reacted in the crystallizer 10 to obtain fine particles mainly composed of transition metal hydroxide. More specifically, the first raw material 12A may be an aqueous solution of nickel sulfate, cobalt sulfate, or manganese sulfate, and the second raw material 12B may be an aqueous solution of sodium hydroxide or ammonia water.

[0044] The particle size of the fine particles in the fine particle slurry produced by the crystallizer 10 is preferably 7 μm or less, more preferably 1 μm or more and 5 μm or less, and even more preferably 1 μm or more and 3 μm or less. In this specification, the particle size of the fine particles in the fine particle slurry is measured by laser diffraction and scattering methods. In addition, the particle size in this specification means the average particle size at 50% of the integrated value in the particle size distribution measured by the above-mentioned measurement method. According to the crystallizer 10 using a swirling flow, the growth of crystal grains can be suppressed after the crystal grains are generated, and it is easy to produce a slurry containing fine particles of such a fine particle size. If the particle size of the fine particles is 7 μm or less, for example, when producing a secondary battery positive electrode material precursor, it is possible to improve the performance by improving the homogeneity of the secondary battery positive electrode material. In other applications, the particle size of the fine particles is as small as possible and is uniform, so that the performance of the final product can be improved. However, in the present invention, fine particles with an average particle size larger than 7 μm may be targeted as necessary.

[0045] The reservoir 18 stores the fine particle slurry containing fine particles generated in the crystallizer 10. A wave-breaking partition plate 130 is disposed in a portion of the reservoir 18 near the liquid level, and a fine particle slurry outlet 26 is formed on the side wall of the reservoir 18 facing the partition plate 130, to which a conduit 28 leading to a slurry tank 30 is connected. A take-out valve 132 and a pump 134 are provided in the conduit 28, and the fine particle slurry is transferred from the reservoir 18 to the slurry tank 30 at an appropriate timing and flow rate. Note that a portion of the fine particle slurry stored in the reservoir 18 may be withdrawn and concentrated, and the concentrated slurry may then be returned to the reservoir 18. By performing the concentration operation, crystallization can be performed in a state where the slurry is highly concentrated.

[0046] The solid content concentration in the particulate slurry transferred from outlet 26 to slurry tank 30 is not limited, but is preferably 5 wt% to 40 wt%, more preferably 10 wt% to 40 wt%, and even more preferably 15 wt% to 40 wt% when producing a positive electrode material precursor for a secondary battery. This concentration range allows stable production of particulates, and provides a good load balance in the subsequent slurry tank 30, agitation cross-flow filtration device 6, and drying device 8, making it possible to increase the total processing efficiency and energy efficiency without overdoing each process and impairing stability.

[0047] [Slurry tank] As shown in FIG. 1, the slurry tank 30 has the function of temporarily storing the fine particle slurry sent from the reservoir 18 and sending it to the agitation type cross-flow filtration device 6, or adding a cleaning liquid to an initially concentrated slurry obtained by initially concentrating the fine particle slurry to wash it, and sending it to the agitation type cross-flow filtration device 6 as a washed slurry.

[0048] The slurry tank 30 is cylindrical with a bottom, and the inner bottom surface is formed in a hemispherical shape. A semicircular anchor-shaped impeller 34 is arranged along the inner bottom surface of the slurry tank 30 with a small constant gap between it and the inner bottom surface, and is rotated coaxially with the slurry tank 30 by a motor 36. A cleaning liquid source 38 is provided for supplying clean cleaning liquid to the slurry tank 30, and a first port of a three-way valve 42 is connected via a conduit 40. A second port of the three-way valve 42 is connected to the slurry tank 30 via an on-off valve 44, and a third port of the three-way valve 42 is connected to a pump 48 and a cleaning liquid tank 50 via a conduit 46.

[0049] The amount of the gap between the outer periphery of the anchor-shaped agitating blade 34 and the inner bottom surface of the slurry tank 30 is not limited, but in order to prevent fine particles from accumulating and adhering to the inner bottom surface of the slurry tank 30, it is preferable that the gap is, for example, about 0.5 to 3.0 cm. In addition, the length of the semicircular outer periphery of the anchor-shaped agitating blade 34 is preferably long enough to face the entire inner bottom surface of the anchor-shaped agitating blade 34. The rotational peripheral speed of the motor 36 at the outer periphery of the anchor-shaped agitating blade 34 is not limited, but is preferably about 0.1 to 3.0 m / sec. Within this range, it is highly effective in preventing fine particles from accumulating and adhering to the inner bottom surface of the slurry tank 30.

[0050] When concentrating the slurry in each process, the slurry is circulated between the slurry tank 30 and the agitation type cross-flow filtration device 6 while the filtrate is extracted from the agitation type cross-flow filtration device 6. This gradually concentrates the slurry, but when it reaches a high concentration, the viscosity of the slurry also increases, and with a normal paddle-type agitator, only the slurry liquid near the agitator can be circulated, making it impossible to keep the entire inside of the slurry tank 30 uniform, and fine particles settle in the slurry tank 30, forming a hard, compressed solid layer at the bottom of the slurry tank 30, making it impossible to extract the slurry. The anchor-type agitator 34 can solve this problem.

[0051] Furthermore, although each process in this apparatus can be operated batchwise, if the downstream drying device 8 is operated continuously, a buffer means for holding the slurry in each process for a relatively long time is required. Therefore, by applying the slurry tank 30 equipped with the anchor-shaped stirring blades 34 as described above, it is possible to uniformly circulate the entire slurry in the slurry tank 30, and it is possible to prevent accumulation and adhesion of fine particles.

[0052] In particular, when producing a cathode material precursor for secondary batteries, the fine particles are metal compounds with a large specific gravity, and therefore if the slurry tank 30 is not stirred uniformly, the solid matter will quickly settle to the bottom of the tank, become hard and compacted, and become impossible to extract. Furthermore, since the highly concentrated slurry has a large specific gravity and an extremely high viscosity, a typical paddle-type stirring blade can only cause convection in the slurry near the stirring blade, making it difficult to maintain a dispersed state by causing uniform convection throughout the entire slurry tank 30.

[0053] The cleaning solution tank 50 is a container for storing a fraction of the filtrate discharged from the agitation type cross-flow filtration device 6 that contains relatively few impurities. The conductivity of the filtrate can be used as an index for grasping the tendency of impurities to be contained. When the conductivity is high, the filtrate contains a large amount of electrolyte as an impurity, and the electrolyte adversely affects, for example, a positive electrode material precursor for a secondary battery. For example, when the detected conductivity is higher than a preset threshold value, the three-way valve 42 and the on-off valve 44 are operated to select either the clean cleaning solution from the cleaning solution source 38 or the clean cleaning solution recovered from the agitation type cross-flow filtration device 6 in the cleaning solution tank 50 and supply it to the slurry tank 30.

[0054] A discharge hole 52 is formed at the bottom lower end of the slurry tank 30, and slurry in various states (fine particle slurry, initial concentrated slurry, washing slurry, or final concentrated slurry) extracted from the slurry tank 30 is sent to a conduit 56 via a pump 54, and the slurry in various states can be transported to the stirred cross-flow filtration device 6 through the conduit 56 (first flow path).

[0055] [Agitation type cross-flow filtration device] As shown in FIG. 3, the agitation cross-flow filtration device 6 has a cylindrical casing 60 arranged almost horizontally. A rotating shaft 140 is arranged along the center line of the casing 60 and rotated by a motor 62. A plurality of disk-shaped agitation blades 142 are fixed to the rotating shaft 140 at regular intervals in the axial direction. The outer diameter of the agitation blades 142 is smaller than the inner diameter of the casing 60. A ring-shaped filter 146 of a certain thickness is fixed coaxially with the casing 60 on the inner peripheral surface of the casing 60 between adjacent agitation blades 142, and a disk-shaped filtrate chamber 148 is formed inside each filter 146. The number of agitation blades 142 and filters 146 is determined by the processing capacity required for the agitation cross-flow filtration device 6. A gap of a certain thickness is formed between the inner surface of the casing 60, the agitation blade 142, and the filter 146, and this gap serves as a slurry chamber 150.

[0056] An inlet 144 is formed at the upstream end of the casing 60, and slurry in various states supplied from the inlet 144 is transported downstream while meandering through a slurry chamber 150 while being squeezed between the rotating agitator blade 142 and a fixed filter 146. The slurry chamber 150 is pressurized by the liquid sending pressure of the pump 54, and during this transport process, the slurry is pressed against the filter 146 while being agitated by the rotation of the agitator blade 142, and the mother liquor and washing liquid in the slurry pass through the filter 146 and enter the filtrate chamber 148. The material of the filter 146 may be any material that does not allow fine particles in the slurry to pass through but allows the filtrate to pass through, and has sufficient mechanical strength.

[0057] Filtrate discharge valves 154 are attached to the casing 60, each communicating with the filtrate chambers 148, and the outlets of the filtrate discharge valves 154 are connected together to a conduit 156. The filtrate that enters the filtrate chambers 148 flows out through the filtrate discharge valves 154 to the conduit 156. As shown in Fig. 1, this conduit 156 is connected to a first port of a three-way valve 74, and a second port of the three-way valve 74 is connected to a drainage path 80 via a conduit 78. The third port of the three-way valve 74 is connected to the cleaning liquid tank 50 via the conduit 76.

[0058] [Conductivity sensor] As shown in Fig. 1, a conductivity sensor 71 is installed in the conduit 156 which is the filtrate outlet of the agitation type crossflow filtration device 6. The conductivity sensor 71 continuously measures the conductivity of the filtrate discharged from the agitation type crossflow filtration device 6 and transmits it to the control device 67. The control device 67 receives the output of the conductivity sensor 71 and detects the progress of the dilution washing process from the output result and the conductivity of the filtrate stored in advance, and determines the completion timing of the dilution washing process. Specifically, it determines that the dilution washing process has been completed when the output result falls below a threshold value set in the control device.

[0059] [Second density sensor] Instead of or in addition to the conductivity sensor 71, a sensor for measuring other physical properties may be provided and the timing of completion of the dilution cleaning process may be determined using the output of the sensor. For example, as described in Modification 2 of the first embodiment, the second embodiment, and Modifications 1 and 2 of the second embodiment, a second density sensor 73 may be provided in the conduit 156 serving as the filtrate outlet of the agitation type crossflow filtration device 6 to measure the density of the filtrate. The second density sensor 73 continuously measures the density of the filtrate discharged from the agitation type crossflow filtration device 6 and transmits the measured value to the control device 67. The control device 67, which receives the output of the second density sensor 73, may detect the progress of the dilution cleaning process from the density of the filtrate and determine the timing of completion of the dilution cleaning process.

[0060] During the initial concentration by the agitation type cross-flow filtration device 6 and for a while after the start of cleaning, the filtrate that enters the filtrate chamber 148 contains a lot of impurities, but as the filtration time passes, the filtrate contains less impurities, so the conductivity detected by the conductivity sensor 71 decreases. Therefore, when the conductivity reaches a predetermined threshold value, the control device 67 switches the three-way valve 74 so that the filtrate that was flowing to the drain 80 is stored in the cleaning liquid tank 50. The relatively clean filtrate stored in the cleaning liquid tank 50 is used as a cleaning liquid by operating the pump 48 in the next dilution cleaning process through the conduit 46, the three-way valve 42, and the on-off valve 44 to be supplied to the slurry tank 30 as a cleaning liquid in the initial stage of the dilution cleaning process. This reduces the amount of cleaning liquid used in the cleaning liquid source 38, which helps reduce the cost of producing fine particle powder. Furthermore, the amount of filtrate and cleaning waste liquid that is discarded outside the fine particle powder production device 1 can be reduced, reducing the burden on the environment.

[0061] The downstream part of the casing 60 is a conical tapered part 152 narrowing downstream, and a discharge port 64 is formed at the tip of the tapered part 152. Slurries in various states are transported downstream while snaking through the slurry chamber 150, and moisture is removed. The slurry is circulated between the slurry tank 30 and the agitation type cross-flow filtration device 6, and filtered and concentrated in the agitation type cross-flow filtration device 6. The concentrated slurry, which has become highly viscous, is discharged from the discharge port 64.

[0062] The solid content concentration of the concentrated slurry discharged from the outlet 64 of the agitation type cross-flow filtration device 6 is different from one another in the initial concentration step, the dilution washing step, and the final concentration step, and is not necessarily limited. As a preferred example, when producing a secondary battery positive electrode material precursor, the solid content concentration of the initial concentrated slurry at the completion of the initial concentration step is preferably 35 wt% or more and 65 wt% or less, more preferably 45 wt% or more and 65 wt% or less. The solid content concentration of the washed slurry at the completion of the dilution washing step is preferably 35 wt% or more and 60 wt% or less, more preferably 35 wt% or more and 45 wt% or less. The solid content concentration of the concentrated slurry at the completion of the final concentration step is preferably 50 wt% to 65 wt%, more preferably 60 wt% or more and 65 wt% or less.

[0063] In each process, when the concentration is within the above-mentioned range, the transportation of the concentrated slurry within the casing 60 of the agitation type crossflow filtration device 6 does not become difficult, and it is possible to effectively reduce the amount of impurities in the final concentrated slurry while limiting the consumption of the washing liquid. Therefore, the load balance of the agitation type crossflow filtration device 6 and the drying device 8 is good, and it is possible to improve the total processing efficiency and energy efficiency without overloading each process.

[0064] [Density sensor] As shown in Figs. 1 and 3, the outlet 64 of the casing 60 is connected to a first port of a three-way valve 70 (a path switching device) via a conduit 63 and a flow rate control valve 68, and a density sensor 66 is installed in a part of the conduit 63, and the output of the density sensor 66 is connected to a control device 67. As the density sensor 66, a vibration type in-line density sensor having an oscillator 66A that contacts the concentrated slurry to be measured and a controller (not shown) that vibrates the oscillator 66A and measures its resonance frequency can be used, although it is not limited thereto. The oscillator 66A of the density sensor 66 is airtightly inserted into the conduit 63 leading from the outlet 64 to the flow rate control valve 68, and is adapted to contact the concentrated slurry flowing in the conduit 63. As a result, when the oscillator 66A vibrates, the higher the density of the concentrated slurry that contacts the oscillator 66A, the lower the resonance frequency of the oscillator 66A, so that it is possible to measure the density of the concentrated slurry with high accuracy by measuring the resonance frequency. In the present invention, a density sensor other than a vibration type or an in-line type may be used, and any sensor that can measure some physical property of the slurry and indirectly estimate the density of the slurry based on the physical property may be used as the density sensor. The second density sensor 73 may be the same as the density sensor 66.

[0065] The following formula 1 is the solids concentration c (wt%) in the slurry and the density ρ slurry (g / cm 3 ) and the true density ρ of the particles in the slurry solid (g / cm 3 ) and the density of the liquid in the slurry, ρ liquid (g / cm 3 ) is shown. To set the solids concentration c (wt%) in the slurry to, for example, 50 wt%, substitute c = 50 and set the density ρ of the slurry so that Equation 1 is satisfied. slurry (g / cm 3 ) and the true density ρ of the particles in the slurry solid (g / cm 3 ) and the density of the liquid in the slurry, ρ liquid (g / cm 3 ) can be adjusted accordingly.

[0066] Slurry density ρslurry (g / cm 3 ) is the density in a slurry state in which the liquid (mother liquor + washing liquid), the fine particles, and impurities are mixed, and can be measured by the density sensor 66. The true density ρ of the fine particles in the slurry solid (g / cm 3 The density ρ of the liquid in the slurry is a value determined by the type of microparticles to be produced (substance type, particle form, shape, particle size) and can be calculated in advance. liquid (g / cm 3 ) is the density in a state including the medium (mainly water), the electrolyte solutes and non-electrolyte solutes dissolved in the medium, and the ultrafine particles that have passed through the filter of the agitation type cross-flow filtration device 6 and are dispersed in the medium. In the first embodiment, the amount of electrolyte solutes is measured as conductivity by the conductivity sensor 71, and ρ liquid (g / cm 3 ) can be approximately estimated, but in the second embodiment in which the second density sensor 73 is provided, the density ρ liquid (g / cm 3 ) can be directly measured. liquid (g / cm 3 In the second embodiment, the density ρ of the liquid is detected by the second density sensor 73, unlike the first embodiment in which the density ρ of the liquid is detected indirectly. liquid (g / cm 3 ) can be directly measured, making it possible to grasp and control the solids concentration c (wt%) in the slurry more accurately.

[0067]

number

[0068] A second port of the three-way valve 70 is connected to the slurry tank 30 via a conduit 72 (second flow path). A third port of the three-way valve 70 is connected to a slurry tank 82 for storing concentrated slurry, which is provided upstream of the drying device 8. The three-way valve 70 is switched under control of the control device 67, or can be switched manually upon receiving an instruction from the control device 67. By operating the three-way valve 70, the slurry in various states discharged from the discharge port 64 of the agitation type crossflow filtration device 6 can be returned to the slurry tank 30 for circulation, or supplied to the slurry tank 82, which serves as a buffer for the drying device 8.

[0069] The concentrated slurry discharged from the discharge port 64 of the agitation type crossflow filtration device 6 has its density measured by a density sensor 66, and the output signal of the density sensor 66 is transmitted to a control device 67. The density sensor 66 has two main purposes. The first is to measure the timing at which the concentrated slurry discharged from the agitation type crossflow filtration device 6 is sufficiently dewatered and reaches a predetermined density, and to grasp at least one of the completion timing of the initial concentration step (A) and the completion timing of the final concentration step (C) and use this to control the transition to the next step.

[0070] In addition, when determining the timing of completion of the dilution washing process (B), it is preferable to satisfy either one of the following conditions: (1) the conductivity of the filtrate decreases to a predetermined threshold based on the output of the conductivity sensor 71 and the density of the concentrated slurry increases to a predetermined threshold based on the output of the density sensor 66, or (2) the conductivity of the filtrate decreases to a predetermined threshold based on the output of the conductivity sensor 71 (the output of the density sensor 66 is not involved in the determination criterion).

[0071] The second purpose of measuring the slurry density using the density sensor 66 is to improve the washing effect of the slurry in the dilution washing step. Specifically, a lower limit and an upper limit are set for the density value corresponding to the output signal of the density sensor 66, and the supply of washing liquid from the washing liquid source 38 to the slurry tank 30 is increased (or resumed after a temporary stop) when the upper limit is reached, and the supply of washing liquid from the washing liquid source 38 is reduced (or temporarily stopped) when the lower limit is reached, thereby maintaining the solids concentration of the concentrated slurry discharged from the agitation type crossflow filtration device 6 within a certain range and adjusting the degree of washing until the conductivity of the filtrate discharged from the agitation type crossflow filtration device 6 is sufficiently reduced.

[0072] [Control device] The control device 67 may be realized by hardware such as a computer including a circuit unit executing a software program. The hardware may be, for example, a central processing unit (CPU), a large scale integration (LSI), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a graphics processing unit (GPU). The program is stored in a storage device having a storage medium, and the storage medium may be, for example, a hard disk drive (HDD), a flash memory, a read only memory (ROM), or a digital versatile disc (DVD). The program may be a differential program that realizes part of the functions of the control device 67. The control device 67 may have output devices such as a display and a speaker, and may be configured to generate images or sounds through these devices and instruct an operator to switch between the various parts instead of directly controlling the various parts of the device.

[0073] [Process switching control of the first embodiment] A specific example of the switching control of the initial concentration step (A), the dilution cleaning step (B), the final concentration step (C) and the discharge step (D) by the control device 67 in the first embodiment will be described with reference to the flowchart of FIG.

[0074] In the initial concentration step (A), the amount of impurities dissolved in the filtrate is relatively large, and the density of the filtrate is high. On the other hand, in the final concentration step (C) after the dilution and washing step (B), the amount of impurities dissolved in the filtrate is small, and the density of the filtrate is lower than that of the filtrate in the initial concentration step (A). Thus, the density (g / cm) of the filtrate in each step is 3 ) are different, so even if the slurry concentration (wt%) is the same, the slurry density (g / cm 3 ) are different. Therefore, the slurry density (g / cm3) of the filtrate at the end of each process corresponds to the desired density. 3 It is preferable that the control device 67 stores these values ​​in advance as threshold values ​​A, B, and C for each process, and performs control to grasp the completion timing of each process.

[0075] When the program is started, the control device 67 of the first embodiment sets the initial concentration step (A) in step S1. The pump 41 is stopped to stop the supply of the cleaning liquid from the cleaning liquid source 38 to the slurry tank 30. The particulate slurry stored in the slurry tank 30 is continuously supplied to the agitation type cross-flow filtration device 6 through a conduit 56 (first flow path) by a pump 54, which is a slurry supply device. The flow paths between the agitation type cross-flow filtration device 6 and the slurry tank 30 are connected through a conduit 72 (second flow path) by a three-way valve 70, which is a flow path switching device, and the slurry discharged from the agitation type cross-flow filtration device 6 is continuously returned to the slurry tank 30. After the setting is completed, the process proceeds to step S2, where the density sensor 66 intermittently or continuously measures the density of the slurry discharged from the agitation type cross-flow filtration device 6, and a density D corresponding to the output signal is calculated. S The determination is repeated to see whether or not the threshold value A is exceeded. If the threshold value A is not exceeded, the process is repeated from step S1.

[0076] The density D corresponding to the output signal SIf it exceeds the threshold value A, proceed to step S3 and set the dilution washing process (B). Since the filtrate density varies for each process, set the threshold value B according to the filtrate density suitable for the end of the dilution washing process (B). Operate pump 41 or pump 48 to start supplying the cleaning liquid from the cleaning liquid source 38 or the cleaning liquid tank 50 to the slurry tank 30. The particulate slurry stored in the slurry tank 30 is continuously supplied to the stirred cross-flow filtration device 6 through the conduit 56 by the pump 54, and the slurry discharged from the stirred cross-flow filtration device 6 through the conduit 72 is continuously returned to the slurry tank 30 by the three-way valve 70.

[0077] After the setting is completed, proceed to step S4, and the density D of the slurry discharged from the stirred cross-flow filtration device 6 is measured by the density sensor 66 S either intermittently or continuously, and the conductivity C of the filtrate is measured by the conductivity sensor 71 R (S / m) either intermittently or continuously. Then, "the conductivity C corresponding to the output signal of the conductivity sensor 71 R is lower than the preset conductivity threshold value D (S / m), and the density D corresponding to the signal of the density sensor 66 S exceeds the threshold value B (C R <D? and D S >B?)」 Determine whether the condition is satisfied repeatedly. If the condition is not satisfied, repeat from step S3.

[0078] [Process switching control of Modification 1 of the First Embodiment] As Modification 1 of the First Embodiment, the determination condition in S4 of FIG. 7 is that "the conductivity C corresponding to the output signal of the conductivity sensor 71 R is lower than the threshold value D (C R <D?)」 may be sufficient. In this case, it will not be determined whether the concentration in the dilution washing process (B) is sufficient, but the same effects as in the First Embodiment can be obtained in other respects. This is because even if the concentration in the dilution washing process (B) is insufficient, it can be concentrated in the subsequent final concentration process (C).

[0079] [Process switching control of Modification 2 of the First Embodiment] As a second modification of the first embodiment, instead of the conductivity sensor 71, a second density sensor 73 is provided, and the determination condition in S4 of FIG. 7 is changed to "the density D of the filtrate corresponding to the output signal of the second density sensor 73 R is lower than the preset threshold value E of the filtrate density, and the density D S corresponding to the signal of the density sensor 66 exceeds the threshold value B (D R < E? and D S > B?)", or whether the condition "the density D of the filtrate corresponding to the output signal of the second density sensor 73 R is lower than the preset threshold value E of the filtrate density (D R < E?)" is satisfied. The threshold value E is the density of the filtrate that is appropriate at the stage when the dilution washing step (B) should be completed. In this case, when the density of the filtrate detected by the second density sensor 73 becomes smaller than the threshold value E, it is determined that the impurities in the filtrate (in this case, electrolyte solutes, non-electrolyte solutes, and ultrafine particles dispersed in the filtrate after passing through the filter) have decreased and sufficient washing has been performed. In other respects, the same effects as those of the first embodiment can be obtained. The difference from the first embodiment is that the impurity concentration can be determined including not only electrolyte solutes but also non-electrolyte solutes and ultrafine particles.

[0080] In the first embodiment, whether "the density D S exceeds the threshold value B and the conductivity C R is lower than the threshold value D" is satisfied, in the first modification of the first embodiment, whether "the conductivity C R is lower than the threshold value D" is satisfied, or in the second modification of the first embodiment, whether "the density D of the filtrate corresponding to the output signal of the second density sensor 73 R is lower than the threshold value E, and the density D S corresponding to the signal of the density sensor 66 exceeds the threshold value B" or "the density D of the filtrate corresponding to the output signal of the second density sensor 73 R is lower than the threshold value E" is satisfied, the process proceeds to step S5 in FIG. 7, and the setting of the final concentration step (C) is performed.

[0081] The threshold value C is determined according to the filtrate density pre-stored in the control device 67 at the stage when the final concentration step (C) should be terminated, and is pre-stored in the control device 67. The pump 41 is stopped to stop the supply of cleaning liquid from the cleaning liquid source 38 to the slurry tank 30. The fine particle slurry stored in the slurry tank 30 is continuously supplied to the agitation type cross-flow filtration device 6 through the conduit 56 by the pump 54. The slurry discharged from the agitation type cross-flow filtration device 6 is continuously returned to the slurry tank 30 by the three-way valve 70. After the settings are completed, the process proceeds to step S6, where the density sensor 66 detects the density D of the slurry discharged from the agitation type cross-flow filtration device 6. S is measured intermittently or continuously, and the density D corresponding to the output signal is S The determination is repeated to see whether or not the condition exceeds the threshold C. If the condition is not satisfied, the process is repeated from step S5.

[0082] Density D S exceeds the threshold C, the discharge step (D) is set. The slurry stored in the slurry tank 30 is continuously supplied to the stirring type cross-flow filtration device 6 through the conduit 56 by the pump 54. The three-way valve 70 is switched to set the slurry discharged from the stirring type cross-flow filtration device 6 to be continuously supplied to the slurry tank 82 communicating with the drying device 8. In this way, the concentrated slurry is stored in the slurry tank 82.

[0083] [Process switching control of the second embodiment] In the process switching control of the second embodiment, instead of the conductivity sensor 71 used in the first embodiment, a second density sensor 73 is provided in the conduit 156 which is the filtrate outlet of the stirring type crossflow filtration device 6. This point is similar to the second modification of the first embodiment, but the control flow is different. In the second embodiment, as shown in FIG. 8, the density D R (g / cm 3 ) is measured in real time by the second density sensor 73, and the target value N A , N B , N C (wt%) and the density ρ of the microparticles to be produced solid(g / cm 3 ) using Equation 1, the slurry density (g / cm 3 ) thresholds A, B, C (g / cm 3 ) are calculated for each judgment cycle, and the threshold values ​​A, B, and C (g / cm 3 ) and the slurry density at the time of judgment D S (g / cm 3 ) to compare.

[0084] As shown in Fig. 8, when the program is started, the control device 67 of the second embodiment sets the initial concentration step (A) in step S1. The contents are the same as step S1 of the first embodiment, so the explanation will be used here. After the settings are completed, the process proceeds to step S2, where the density sensor 66 detects the density D of the slurry discharged from the agitation cross-flow filtration device 6. S (g / cm 3 ) is measured intermittently or continuously, and the density ρ of the filtrate discharged from the agitation type cross-flow filtration device 6 is measured by the second density sensor 73. liquid (g / cm 3 ) is measured intermittently or continuously. Furthermore, the true density ρ solid (g / cm 3 ), the real-time density ρ of the filtrate measured by the second density sensor 73 liquid (g / cm 3 ), and the target value N A By inputting (wt%), the slurry density ρ slurry (g / cm 3 ) is calculated.

[0085] Next, proceed to step S3, and determine the threshold value A of the slurry density (g / cm 3 ) and the slurry density D measured in real time by the density sensor 66 S (g / cm 3 ) and the slurry density D S does not exceed the threshold A, the process returns to step S1, the settings in step S1 are maintained, and the real-time density ρ of the filtrate is calculated in step S2. liquid (g / cm 3) The threshold value A is recalculated based on the newly calculated threshold value A in step S3 and the slurry density D measured in real time by the density sensor 66. S (g / cm 3 ) is repeatedly compared. Eventually, the slurry density D S If exceeds threshold A, proceed to step S4.

[0086] In step S4, the dilution and washing process (B) is set. The contents are the same as those in step S3 of the first embodiment, so the description will be used here. After the settings are complete, the process proceeds to step S5, where the density sensor 66 detects the density D of the slurry discharged from the agitation cross-flow filtration device 6. S (g / cm 3 ) is measured intermittently or continuously, and the density ρ of the filtrate discharged from the agitation type cross-flow filtration device 6 is measured by the second density sensor 73. liquid (g / cm 3 ) is measured intermittently or continuously. Furthermore, the true density ρ solid (g / cm 3 ), the real-time density ρ of the filtrate measured by the second density sensor 73 liquid (g / cm 3 ), and the target value N of the solids concentration in the dilution and washing process (B) B By inputting (wt%), the slurry density ρ slurry (g / cm 3 ) is calculated.

[0087] Next, proceed to step S6, and determine the threshold value B (g / cm 3 ) and the slurry density D measured in real time by the density sensor 66 S (g / cm 3 ) and the slurry density D S exceeds the threshold B and the real-time density of the filtrate ρ liquid (g / cm 3 ) is smaller than a preset filtrate density threshold value F. If the condition is not met, the process returns to step S4, the settings of step S4 are maintained, and the real-time filtrate density ρ liquid (g / cm 3) and recalculate the threshold value B based on the newly calculated threshold value B in step S5 and the slurry density D measured in real time by the density sensor 66. S (g / cm 3 ) and real-time filtrate density ρ liquid (g / cm 3 It is determined whether the density of the filtrate is smaller than a preset threshold value F. When the determination condition is met, the process proceeds to step S7.

[0088] In step S7, the final concentration step (C) is set. The details are the same as those in step S5 of the first embodiment, so the description will be used here. After the settings are complete, the process proceeds to step S8, where the density sensor 66 detects the density D of the slurry discharged from the agitation cross-flow filtration device 6. S (g / cm 3 ) is measured intermittently or continuously, and the density ρ of the filtrate discharged from the agitation type cross-flow filtration device 6 is measured by the second density sensor 73. liquid (g / cm 3 ) is measured intermittently or continuously. Furthermore, the true density ρ solid (g / cm 3 ), the real-time density ρ of the filtrate measured by the second density sensor 73 liquid (g / cm 3 ), and the target solids concentration in the final concentration step (C) N C By inputting (wt%), the slurry density ρ slurry (g / cm 3 ) is calculated.

[0089] Next, proceed to step S9, and determine the slurry density threshold C (g / cm 3 ) and the slurry density D measured in real time by the density sensor 66 S (g / cm 3 ) and the slurry density D S It is determined whether or not the density of the filtrate exceeds the threshold value C. If the condition is not met, the process returns to step S7, the setting of step S7 is maintained, and the real-time density of the filtrate ρ liquid (g / cm 3) and recalculate the threshold value C based on the slurry density D measured in real time by the density sensor 66. S (g / cm 3 ) exceeds the newly calculated threshold C in step S8. When the determination condition is met, the process proceeds to step S10.

[0090] In step S10, the discharge step (D) is set. The pump 54 continuously supplies the slurry stored in the slurry tank 30 to the stirring cross-flow filtration device 6 through the conduit 56. The three-way valve 70 is switched to set the slurry discharged from the stirring cross-flow filtration device 6 to be continuously supplied to the slurry tank 82 communicating with the drying device 8. In this way, the concentrated slurry is stored in the slurry tank 82.

[0091] According to the process switching control of the second embodiment, the density D of the filtrate is R (g / cm 3 ) is measured in real time by the second density sensor 73, and the target value N A , N B , N C (wt%) and the density ρ of the microparticles to be produced solid (g / cm 3 ) using Equation 1, the slurry density (g / cm 3 ) thresholds A, B, C (g / cm 3 ) are calculated for each judgment cycle, and the threshold values ​​A, B, and C (g / cm 3 ) and the slurry density at the time of judgment D S (g / cm 3 ) is compared, so the density of the filtrate D in real time is displayed for each judgment. R (g / cm 3 ) based on the slurry density thresholds A, B, and C (g / cm 3 ) can be corrected, and the target solids concentration N A , N B , N C This has the advantage that more precise control can be performed based on the weight percent.

[0092] [Process Switching Control of Modification Example 1 of the Second Embodiment] As a modification example 1 of the second embodiment, the conductivity sensor 71 is used in combination with the second density sensor 73. In addition to the flow chart of FIG. 8, when the conductivity of the filtrate is equal to or less than the threshold value in step S6 (condition (C R <D?) can also be added as a determination condition. That is, the determination condition in S6 of FIG. 8 can be “Ds > B? and D R <F? and C R <D?”. Thereby, the concentration of the electrolyte solute, which has a great influence on the quality of the final product, can be monitored doubly, and the management quality of the electrolyte impurities can be improved.

[0093] [Process Switching Control of Modification Example 2 of the Second Embodiment] As a modification example 2 of the second embodiment, in S6 of FIG. 8, instead of the density D R of the filtrate, the conductivity C R of the filtrate is intermittently or continuously measured by the conductivity sensor 71, and the measured conductivity C R is compared with the conductivity threshold D. That is, the determination condition in S6 of FIG. 8 can be “Ds > B? and C R <D?”. The threshold value D is the conductivity that is appropriate at the stage when the dilution washing step (B) should be completed and is set in advance.

[0094] [Process Switching Control of Modification Example 3 of the Second Embodiment] As a modification example 3 of the second embodiment, the slurry concentration can be used instead of the slurry density as the threshold value used in each process. In this case, in each process (A) to (C), the slurry density D S (g / cm 3 ) measured in real time by the density sensor and the second density sensor 73 using Equation 1, the density D R (g / cm 3 ) of the filtrate, and the true density ρ solid (g / cm 3 ) of the fine particles to be manufactured, the slurry concentrations C A , C B , C C(wt%) is calculated continuously or at predetermined intervals, and these calculation results are compared with the solid content concentrations W that are threshold values in each of the steps (A) to (C) stored in advance in the control device 67. A W B W C (wt%) and compared.

[0095] In the initial concentration step (A), the control device 67 compares the calculated slurry concentration C A with the preset threshold value W of the solid content concentration A and, when the slurry concentration C A exceeds the threshold value W A , determines to switch to the dilution washing step. That is, the determination condition for the initial concentration step (A) is "C A >W A ?"

[0096] In the dilution washing step (B), the slurry concentration C B is compared with the threshold value W of the solid content concentration B and, when the slurry concentration C B exceeds the threshold value W B and it is determined that at least one of the density or conductivity of the filtrate is lower than the threshold value of the density or conductivity of the filtrate stored in the control device 67, it is determined to switch to the final concentration step. That is, the determination condition for the dilution washing step (B) is, "C B >W B ? and D R <F?", or "C B >W B ? and C R <D?", or, "C B >W B ? and D R <F? and C R <D?". For the threshold values F and D, the previous explanations are incorporated.

[0097] In the final concentration step (C), the calculated slurry concentration C C is compared with the threshold value W C and, when the slurry concentration C C exceeds the threshold value W cWhen the concentration exceeds the threshold value, the final concentration step (C) is judged to be completed. C >W C ?"

[0098] In this way, in the third modification of the second embodiment, the slurry density Ds and the density D of the filtrate measured in real time are R By calculating the slurry concentration from the above and comparing and judging it with the threshold value, precise control that reflects the properties of the slurry and filtrate can be performed. By using the slurry concentration as the threshold value, the operator can easily change the threshold setting.

[0099] In the third variant of the second embodiment, in the dilution washing process (B), it is preferable to calculate the current slurry concentration from the density sensor 66 and the second density sensor 73 and the true density of the microparticles to be produced, and to control the increase / decrease in the supply flow rate of the washing water, or the supply / stop, so that the current slurry concentration falls within a preset range between upper and lower limits of the slurry concentration in the dilution washing process.

[0100] Next, a specific example of control by the control device 67 for enhancing the washing effect of the slurry in the dilution washing step (B) will be described. The following control is performed until the electrical conductivity of the filtrate discharged from the stirring type cross-flow filtration device 6 is sufficiently reduced, and when the electrical conductivity has been sufficiently reduced, the process proceeds to step S5 in Fig. 7 in the first embodiment (and modified examples 1 and 2), and to step S7 in Fig. 8 in the second embodiment.

[0101] 9 to 11 show specific examples of cleaning liquid volume control by the control device 67 that can be implemented in each of the above-described embodiments. In the control example of Fig. 9, when the density of the slurry in the dilution washing process (B) is within the target density range D2 to D3, the flow rate of the washing liquid is constant at a reference flow rate F2. When the density of the concentrated slurry falls below the lower limit D2 of the target density range and becomes, for example, D1, the flow rate F1 is calculated by subtracting a value proportional to the value of D2-D1 from the reference value F2. When the density of the concentrated slurry rises above the upper limit D3 of the target density range and becomes, for example, D4, the flow rate F3 is calculated by adding a value proportional to the value of D4-D3 to the reference value F2.

[0102] In the control example of FIG. 10, the flow rate of the cleaning liquid is increased linearly to F1, F2, F3, and F4 as the density increases to D1, D2, D3, and D4, including the case where the density of the concentrated slurry is within the target density range D2 to D3.

[0103] In the control example of FIG. 11, when the density of the concentrated slurry is within the target density range D2 to D3, the flow rate of the cleaning liquid is constant at a reference flow rate F2. When the density of the concentrated slurry falls below the lower limit value D2 of the target density range (for example, D1), the flow rate F1 lower than the reference value F2 is fixed. When the density of the concentrated slurry rises above the upper limit value D3 of the target density range, for example to D4, the flow rate F3 higher than the reference value F2 is fixed. Even with this simplified control, it is possible to maintain the density of the concentrated slurry within the target density range D2 to D3.

[0104] In addition, the supply flow rate of the cleaning water may be kept constant, and the supply of the cleaning water may be stopped when the slurry density falls below a set lower threshold, while the supply of the cleaning water may be started when the slurry density exceeds a set upper threshold.

[0105] In either case, a certain time T is required from when the washing slurry is introduced into the agitation type crossflow filtration device 6 by the pump 54 until filtration is completed, until the increase in the washing liquid flow rate by the pump 41 is reflected in the density of the concentrated slurry discharged from the agitation type crossflow filtration device 6. Therefore, each of the above controls may be performed intermittently at regular intervals of time T' that are longer than time T, and the same washing liquid flow rate may be maintained during the lapse of time T'. Further, a control method that takes into consideration the "dead time" from when the flow rate of the cleaning liquid is increased by the pump 41 until the increase is reflected in the density of the concentrated slurry discharged from the agitation type cross-flow filtration device 6, for example, a Smith predictor may be incorporated in the control device 67 to perform more advanced feedback control.

[0106] The control method by the control device 67 is not limited to the examples shown in Figs. 7 to 11 and may be appropriately changed as necessary. For example, it is possible to perform switching control only at one of the timings of the completion of the initial concentration step (A), the completion of the dilution cleaning step (B), and the completion of the final concentration step (C), or to perform switching control only at two of these timings. Other switching may be performed at the discretion of an operator without relying on the control device 67.

[0107] Returning to FIG. 1, the rest of the device will be explained. The slurry tank 82 performs a buffer function for adjusting the supply amount of concentrated slurry to the drying device 8. The slurry tank 82 is cylindrical with a bottom, and the inner bottom surface is formed in a hemispherical shape. A semicircular anchor-shaped stirring blade 84 is arranged along the inner bottom surface of the slurry tank 82 with a small constant gap between it and the inner bottom surface, and is rotated by a motor 86. The rotation speed of the motor 86 is adjusted so that the concentrated slurry does not settle and solidify in the slurry tank 82. A discharge port 88 is formed at the lower end of the bottom of the slurry tank 82, and the highly viscous concentrated slurry extracted from the slurry tank 82 is sent to a conduit 94 via a pump 90 and sent to the drying device 8.

[0108] The amount of the gap between the outer periphery of the anchor-shaped agitating blade 84 and the inner bottom surface of the slurry tank 82 is not limited, but in order to prevent the accumulation and adhesion of fine particles to the inner bottom surface of the slurry tank 82, similar to the anchor-shaped agitating blade 34 described above, it is preferable that the length of the semicircular outer periphery of the anchor-shaped agitating blade 84 is a length that can face the entire inner bottom surface of the slurry tank 82. Furthermore, the rotational peripheral speed of the anchor-shaped agitating blade 84 at the outer periphery by the motor 86 is not limited, but is preferably about 0.1 to 3.0 m / sec. Within such a range, the effect of preventing the accumulation and adhesion of fine particles to the inner bottom surface of the slurry tank 82 is obtained. In particular, when a secondary battery positive electrode material precursor is produced, this is an important effect because the fine particles are metal compounds and have a large specific gravity.

[0109] [Drying equipment] 4 to 6 are a side cross-sectional view, a plan view with the top plate removed, and a front cross-sectional view showing an agitation heat transfer device as the drying device 8. The drying device 8 has a rectangular parallelepiped casing 92, which has a gutter-shaped inner wall 194, an outer wall 198 covering the outer peripheral surface of the inner wall 194, and a rectangular top plate 196 closing the upper end of the inner wall 194. An airtight gap of a certain thickness is formed between the inner wall 194 and the outer wall 198, which serves as a heat medium passage 199, and the outer wall 198 is formed with a heat medium inlet 200 and a heat medium outlet (not shown) communicating with the heat medium passage 199. The inside of the casing 92 can be heated uniformly by supplying high-temperature steam or heat medium oil from the heat medium inlet 200 to the heat medium outlet.

[0110] An inlet 96 is formed at the upper end of the upstream side of the casing 92, and a conduit 94 is connected to it. A gas inlet 174 is formed at the upper surface of the upstream side of the casing 92, and a gas outlet 175 is formed at the upper surface of the downstream side. Room temperature or heated air or the like is blown in through the gas inlet 174, and the moist air or the like is discharged from the gas outlet 175 together with the water vapor generated in the casing 92 as the mother liquor and the cleaning liquid evaporate, thereby allowing the water vapor generated in the casing 92 to be discharged outside the apparatus, thereby making it possible to maintain an appropriate humidity level. Meanwhile, an outlet 98 is formed at the lower surface of the downstream end of the casing 92, and the fine particle powder dried in the casing 92 is discharged from there.

[0111] Two hollow rotating shafts 176 are arranged symmetrically along the longitudinal direction within the casing 92, and both ends or one end are rotatably supported by bearings. Hollow agitating blades 178 are fixed to each hollow rotating shaft 176 at regular intervals in the axial direction, and in the region between the two hollow rotating shafts 176, the hollow agitating blade 178 of one hollow rotating shaft 176 is located midway between the hollow agitating blades 178 of the other hollow rotating shaft 176.

[0112] As shown in Fig. 6, each hollow agitating blade 178 is fan-shaped with a central angle of less than 180°, and a pair of hollow agitating blades 178 are fixed at positions that are 180° rotationally symmetrical about the hollow rotating shaft 176. A notch 190 of a certain width is formed between the pair of hollow agitating blades 178 so that the mixture of concentrated slurry and wet powder can pass in the axial direction. The inside of the hollow agitating blade 178 is hollow and communicates with the internal space of the hollow rotating shaft 176, so that the heat medium supplied to the hollow rotating shaft 176 also enters the inside of the hollow agitating blade 178 and heats the hollow agitating blade 178.

[0113] The wet powder is a dried product of the concentrated slurry that is previously stored in the casing 92, and is not completely dry but moist. By mixing the previously stored wet powder with the concentrated slurry, abnormal adhesion that may impede the function of the drying device 8 can be avoided, and the transportation within the casing 92 by the hollow agitating blade 178 can be facilitated.

[0114] As shown in Figures 4 and 5, the pair of hollow agitating blades 178 are inclined in opposite directions with respect to the hollow rotating shaft 176, and the locus of the agitating blades 178 swings in the axial direction within a certain angle range every time the hollow rotating shaft 176 rotates 180°, as shown by the solid and dotted lines in the figures. This swinging prevents the concentrated slurry and the wet powder held in the casing 92 from adhering to the hollow agitating blades 178 between the axially adjacent agitating blades 178, while mixing the concentrated slurry and the wet powder. The agitating blades 178 also have a twist along a virtual spiral plane around the hollow rotating shaft 176, and also function to gradually transport the mixture of the concentrated slurry and the wet powder held in the casing 92 from the upstream side to the downstream side of the casing 92 as the hollow rotating shaft 176 rotates.

[0115] The hollow agitator blade 178 and the hollow rotating shaft 176 are made of a metal with high thermal conductivity, and a heat medium inlet hole 184 and a heat medium outlet hole 182 are formed at the upstream end of the hollow rotating shaft 176. A heat medium such as high-temperature steam or heat medium oil is continuously supplied from a heat medium source (not shown) to the heat medium outlet hole 182 from the heat medium inlet hole 184, and the heat medium is distributed over the entire length of the hollow rotating shaft 176. The heat medium also penetrates into the hollow agitator blade 178, and the entire hollow rotating shaft 176 and the hollow agitator blade 178 are heated to a temperature higher than the boiling point of the mother liquor and washing liquid contained in the concentrated slurry and the wet powder. Therefore, every time the mixture of the concentrated slurry and the wet powder touches the hollow rotating shaft 176 and the hollow agitator blade 178, it is heated by conduction heat transfer, and the mother liquor and washing liquid contained in the mixture evaporate, eventually becoming fine powder. A rotating mechanism 180 is provided at one end of the hollow rotating shaft 176, and the hollow rotating shaft 176 is simultaneously rotated in the reverse direction by a motor (not shown), and the mixture of the concentrated slurry and the wet powder held in the casing 92 is transported in the transport direction T from the upstream to the downstream of the casing 92 by the hollow stirring blade 178 while being heated by conductive heat transfer. In addition, the positional relationship between the heat medium inlet hole 184 and the heat medium outlet hole 182 shown in Fig. 4 may be interchanged. That is, the heat medium outlet hole 182 may be provided radially inside the heat medium inlet hole 184.

[0116] The fine powder discharged from the discharge port 98 of the drying device 8 is stored in a storage container 102 through a discharge path 100 as shown in FIG. 1. The number of hollow rotating shafts 176 is not limited to two, and may be two or more. Therefore, it can be said that it is sufficient to have a plurality of hollow rotating shafts 176. In the case of a plurality of hollow rotating shafts 176, they may be parallel to each other.

[0117] The method for producing fine-particle powder using the fine-particle powder production apparatus 1 described above is carried out as follows. [Microparticle slurry manufacturing process] First, in the initial state, the crystallizer 10 and the reservoir 18 are filled with mother liquor. The motor 126 rotates the stirring blade 128, and the pump 22 is operated to blow the mother liquor in the reservoir 18 into the reaction vessel 116 from the inlet 115, generating a swirling flow in the reaction vessel 116. The first raw material 12A is supplied from the first inner tube 112, and the second raw material 12B is supplied from the second inner tube 114. The two are vigorously mixed in the central region R in the tapered portion 116A, and fine particles are generated by the reaction of the first raw material 12A and the second raw material 12B. The mother liquor containing the fine particles is returned to the reservoir 18 through the conduit 16, and a fine particle slurry is generated in the reservoir 18 as the mother liquor circulates repeatedly. The pressure of the mother liquor introduced from the inlet 115 is measured by a pressure gauge 122, and the flow rate of the microparticle slurry flowing out from the discharge hole 14 is appropriately adjusted by a flow control valve 118, thereby adjusting the solids concentration of the microparticle slurry in the reservoir 18 to an appropriate range.

[0118] [Initial concentration process] When the solids concentration of the particulate slurry in the reservoir 18 reaches an appropriate range, an initial concentration step (A) is started to concentrate the particulate slurry and convert it into an initially concentrated slurry. The initial concentration step is, so to speak, a step of dehydrating the particulate slurry before washing. In the initial concentration step, the three-way valve 70 is controlled to set a circulation path so that the slurry discharged from the agitation type cross-flow filtration device 6 returns to the slurry tank 30 through the conduit 72. In addition, in the initial concentration step, the supply of the washing liquid is stopped (step S1 in FIG. 7, step S1 in FIG. 8).

[0119] The discharge valve 132 is opened, and the fine particle slurry in the reservoir 18 is discharged from the discharge port 26 through the conduit 28, and transferred to the slurry tank 30 by the pump 134. In the slurry tank 30, the anchor-shaped agitator blade 34 is rotated by the motor 36 to prevent the fine particles in the fine particle slurry from settling, and the pump 54 is operated to supply the fine particle slurry from the discharge hole 52 to the agitation type crossflow filtration device 6. As shown in Figure 3, the fine particle slurry is continuously introduced from the inlet 144 of the agitation type crossflow filtration device 6 into the slurry chamber 150 in the casing 60.

[0120] In the slurry chamber 150, the interior is pressurized by the discharge pressure of the pump 54, and the stirring blade 142 is continuously rotated by the motor 62. The fine particle slurry is pressed against the side of the filter 146 while being stirred by the stirring blade 142, and the mother liquor in the fine particle slurry is filtered by the filter 146 and flows into the filtrate chamber 148. As the fine particle slurry advances downstream in the casing 60, the mother liquor in the fine particle slurry decreases, and the slurry is discharged from the discharge port 64 as a somewhat concentrated slurry. The discharged slurry is returned to the slurry tank 30 via the three-way valve 70 and the conduit 72.

[0121] The filtrate that has flowed into the filtrate chamber 148 is collected in a conduit 156 via a filtrate discharge valve 154. In the initial state, the conduit 156 is connected to the conduit 78 by the three-way valve 74, and the initial filtrate containing a large amount of impurities is discarded in a drain 80. This process is repeated while measuring the density of the slurry with the density sensor 66 until the density of the fine particle slurry reaches a predetermined value and an initial concentrated slurry having the above-mentioned solid concentration is obtained (step S2 in FIG. 7, step S3 in FIG. 8).

[0122] [Dilution and washing process] When an initially concentrated slurry of a predetermined concentration is obtained in the slurry tank 30, the initial concentration step is ended, and a dilution washing step (B) is started in which the initially concentrated slurry is diluted with a washing liquid for washing (step S3 in FIG. 7, step S4 in FIG. 8). In the dilution washing step, the three-way valve 70 maintains a circulation path in which the slurry discharged from the agitation type cross-flow filtration device 6 returns to the slurry tank 30 through the conduit 72. Even in this state, the filtrate collected in the conduit 156 via the filtrate discharge valve 154 is discharged to the drain 80 through the three-way valve 74 and the conduit 78 as filtrate with a large amount of impurities.

[0123] Also, while controlling the density with the density sensor 66 and the level of the slurry tank 30, the on-off valve 44 is opened, the conduit 46 is connected to the slurry tank 30 with the three-way valve 42, and the pump 48 is operated to first supply the cleaning liquid from the cleaning liquid tank 50 to the slurry tank 30. The cleaning liquid tank 50 stores relatively clean cleaning liquid obtained during the previous production of fine particle powder. This is because, immediately after the start of the dilution and cleaning process (first stage), the initial concentrated slurry contains a large amount of impurities, so that even a cleaning liquid with a low level of cleanliness can provide a sufficient cleaning effect. As a result, the initial concentrated slurry circulates between the slurry tank 30 and the agitation type crossflow filtration device 6, while cleaning in the slurry tank 30 and filtration by the agitation type crossflow filtration device 6 are continued.

[0124] As the cleaning liquid from the cleaning liquid tank 50 is continuously supplied to the slurry tank 30 and the cleaning of the initial concentrated slurry proceeds, impurities (electrolyte components, non-electrolyte components, ultrafine particles) in the filtrate discharged from the agitation type cross-flow filtration device 6 are reduced, so that the conductivity (or density) of the filtrate indicated by the conductivity sensor 71 (or the second density sensor 73) installed in the conduit 156 decreases. When the conductivity or density reaches a target value (a target value for switching from the cleaning liquid in the cleaning liquid tank 50 to the clean cleaning liquid in the cleaning liquid source 38) (or when the amount of liquid in the cleaning liquid tank 50 has sufficiently decreased), the pump 48 is stopped automatically or manually by the control device 67 to stop the supply of the reused cleaning liquid from the cleaning liquid tank 50, and then the three-way valve 42 is automatically or manually operated by the control device 67 to start the supply of the clean cleaning liquid from the cleaning liquid source 38 to the slurry tank 30.

[0125] As the cleaning and filtration of the initially concentrated slurry proceeds using clean cleaning liquid from the cleaning liquid source 38, impurities in the filtrate discharged from the agitation type cross-flow filtration device 6 are further reduced, and the conductivity (or density) of the filtrate indicated by the conductivity sensor 71 (or the second density sensor 73) installed in the conduit 156 decreases. When the conductivity or density reaches the next target value (a target value indicating completion of cleaning) and the density of the fine particle slurry becomes a predetermined value (step S4 in FIG. 7, step S6 in FIG. 8), the cleaning liquid source 38 is stopped, and the three-way valve 42 and the on-off valve 44 are automatically controlled by the control device 67 or manually operated to stop the supply of the cleaning liquid.

[0126] [Final concentration process] After the supply of the washing liquid is stopped and the dilution washing step is completed, a final concentration step is performed to finally concentrate the washing slurry (step S5 in FIG. 7, step S7 in FIG. 8). In the final concentration step, the washing slurry is supplied to the agitation type cross-flow filtration device 6, and separated into a concentrated washing slurry and a filtrate. The concentrated washing slurry is returned to the slurry tank 30. In this way, the washing slurry is continuously filtered (dehydrated) by the agitation type cross-flow filtration device 6 while circulating between the slurry tank 30 and the agitation type cross-flow filtration device 6. Therefore, the slurry in the slurry tank 30 is gradually concentrated (step S6 in FIG. 7, step S9 in FIG. 8).

[0127] When the conductivity of the filtrate measured by the conductivity sensor 71 provided in the conduit 156 eventually falls below a predetermined target value, it is determined that the filtrate has become clean enough to be used for primary washing in the slurry tank 30, and the three-way valve 74 is switched automatically or manually by the control device 67, and the filtrate from the conduit 156 is stored in the washing liquid tank 50 through the conduit 76. When the filtrate becomes sufficiently clean, storage in the washing liquid tank 50 may start from the latter stage of the dilution washing step as well as from the final concentration step.

[0128] The density of the concentrated slurry discharged from the discharge port 64 of the agitation type cross-flow filtration device 6 is continuously or intermittently measured by the density sensor 66. When the density of the concentrated slurry measured by the density sensor 66 is higher than the target range, the rotation speed of the pump 41 is increased or the pump 41 is started to increase the amount of cleaning liquid from the cleaning liquid source 38 to the slurry tank 30, thereby diluting the slurry in the slurry tank 30. Conversely, when the density of the concentrated slurry measured by the density sensor 66 is lower than the target range, the rotation speed of the pump 41 is decreased or the pump 41 is stopped to reduce or stop the amount of cleaning liquid from the cleaning liquid source 38 to the slurry tank 30, thereby suppressing dilution of the slurry in the slurry tank 30. In this way, feedback control is performed so that the solid concentration in the concentrated slurry falls within a certain range (FIGS. 9 to 11).

[0129] The concentrated slurry, whose solid content has been adjusted to fall within a certain range, is sent to the slurry tank 82 via the flow control valve 68 and the three-way valve 70 (step S7 in FIG. 7, step S10 in FIG. 8). The concentrated slurry stored in the slurry tank 82 is continuously stirred by the anchor-shaped stirring blade 84 to prevent settling.

[0130] [Drying process] The drying process is a process of drying the concentrated slurry to a fine powder state. In the drying process, the concentrated slurry in the slurry tank 82 is sent to the drying device 8 by the pump 90, and is introduced into the casing 92 from the inlet 96 through the conduit 94. In the casing 92, two hollow rotating shafts 176 are continuously rotating, and the hollow agitating blades 178 are heated by high-temperature steam or heat transfer oil supplied to the heat transfer medium inlet 184. As the hollow agitating blades 178 rotate, the concentrated slurry and the wet powder held in the casing 92 are mixed, and the mixture is sent in the transfer direction T. In the process, the mixture is heated by conduction heat transfer in the heated hollow agitating blades 178 while preventing the mixture from adhering to the hollow agitating blades 178 between the adjacent hollow agitating blades 178 due to the oscillation of the hollow agitating blades 178, and the drying process of the mixture progresses. Room temperature or heated air or the like is blown in from gas inlet 174 and moist air or the like is discharged from gas outlet 175, thereby discharging water vapor generated within casing 92 to the outside of the apparatus, thereby maintaining an appropriate humidity level within the apparatus. When the mixture reaches the downstream side of casing 92, it becomes fine particle powder, which is successively discharged from outlet 98. The fine particle powder discharged from outlet 98 is stored in storage container 102 through discharge path 100.

[0131] [Effects of this embodiment] According to the concentrating device for fine particle slurry, the manufacturing method for fine particle powder, and the manufacturing device 1 for manufacturing fine particle powder according to the above-mentioned embodiments, the density of the concentrated slurry after filtration by the stirring cross-flow filtration device 6 is measured by the density sensor 66, and the rotation speed of the pump 41 is adjusted by the control device 67, and the supply amount of the cleaning liquid to the slurry tank 30 is feedback-controlled. Therefore, even if the processing material has extremely small average particle diameter of fine particles, for example, 7 μm or less, the concentration of the concentrated slurry can be stably controlled even in a high concentration range of, for example, 35 wt % to 65 wt %, and fine particle powder can be stably manufactured while preventing clogging by the concentrated slurry.

[0132] In addition, by controlling or instructing the timing using the control device 67, the initial concentration step (A) for obtaining an initial concentrated slurry, the dilution and washing step (B) for diluting and washing the initial concentrated slurry to obtain a washed slurry, and the final concentration step (C) for concentrating the washed slurry to obtain a concentrated slurry can be appropriately switched between, thereby enabling the slurry to be stably concentrated even in a high concentration range.

[0133] Furthermore, according to this embodiment, when the solids concentration of the washing slurry is adjusted to 30 wt % or more and 60 wt % or less, and the solids concentration of the concentrated slurry generated by the stirred cross-flow filtration device 6 is adjusted to 35 wt % or more and 65 wt % or less, it is possible to prevent clogging due to high-concentration slurry, optimize production efficiency in the filtration and drying processes, and reduce energy costs.

[0134] Furthermore, when a vibrating in-line density sensor is used as the density sensor 66, and the vibrator 66A in contact with the concentrated slurry is vibrated to measure the resonant frequency as a function of the density of the concentrated slurry, the density of the concentrated slurry can be measured with high accuracy and without delay even if the concentrated slurry is highly concentrated and viscous. This makes it possible to stably produce fine particle powder while preventing blockage due to the concentrated slurry.

[0135] In addition, since the stirring cross-flow filtration device 6 is used, it is possible to produce a concentrated slurry in a higher concentration range even when the average particle size of the fine particles is extremely small, for example, 7 μm or less. This makes it possible to prevent clogging due to a high-concentration slurry, while improving the production efficiency in the filtration and drying processes and reducing energy costs.

[0136] Furthermore, when the microparticles are a precursor of a positive electrode material for a secondary battery, it is possible to produce a precursor of a positive electrode material for a secondary battery while preventing blockage at the concentrated slurry stage, improving production efficiency in the filtration and drying processes, and reducing energy costs.

[0137] In the drying device 8, the hollow agitating blades 178 of the hollow rotating shafts 176 are fixed to each other at intervals in the axial direction and so as to overlap partially when viewed in the axial direction, so that as the hollow agitating blades 178 rotate, the heated hollow agitating blades 178 heat and transport the concentrated slurry, during which the concentrated slurry is dried and converted into fine powder. Therefore, compared to the method using hot air, the moisture can be evaporated more efficiently, and the excellent effect of reducing energy costs and increasing production efficiency is achieved.

[0138] It should be noted that the present invention is not limited to the above-described embodiment, and additions, deletions, and replacements with well-known techniques of constituent elements are possible within the scope of the claims. [Industrial Applicability]

[0139] As described above, according to the device for concentrating fine particle slurry, the device and method for producing fine particle powder of the present invention, the viscosity change of the slurry is correctly grasped even in a high concentration range by the density sensor, and the amount of cleaning liquid supplied to the slurry tank by the cleaning liquid supply device is controlled by the control device, so that even when the average particle size of the fine particles is small, it is possible to stably concentrate the fine particle slurry even in a high concentration range while suppressing clogging of the filter and the associated flow paths. Therefore, the present invention is industrially applicable. [Explanation of symbols]

[0140] 1. Fine particle powder manufacturing equipment 2. Fine particle slurry manufacturing equipment 6. Agitated cross-flow filtration equipment 8 Drying equipment 10 Crystallization equipment 12A 1st raw material 12B 2nd raw material 12C Mother liquor 14 Discharge hole 16 Conduit 18 Reservoir 20 Conduit 22 Pump 24 Conduit 26 Outlet 28 Conduit 30 Slurry tank 34 Anchor-shaped mixing blade 36 Motor 38 cleaning fluid source 40 conduit 41 Pump F1~F4 Cleaning fluid flow rate 42 Three-way valve 44 On-off valve 46 Conduit 48 Pump 50 cleaning solution tank 52 drain hole 54 Pump 56 Conduit (first flow path) 60 Casing 62 Motor 64 Outlet 66 Density sensor 67 Control device 68 Flow control valve D1~D4 Density of concentrated slurry 70 Three-way valve 71 Conductivity sensor 72 conduit (second flow path) 73 second density sensor 74 Three-way valve 76 Conduit 78 Conduit 80 Drain 82 Slurry tank 84 Anchor-shaped mixing blade 86 Motor 88 Exhaust port 90 Pump 92 Casing 94 Conduit 96 Inlet 98 Discharge port 100 Export path 102 Storage container 110 Outer tube 112 1st inner pipe 114 2nd inner pipe 115 inlet 116 reaction vessel 116A Tapered section 118 Flow control valve 120 Drive unit 122 Pressure gauge 124 Temperature Controller 126 Motor 128 Agitator blade 130 Partition plate 132 Extraction valve 134 Pump 140 Rotating shaft 142 Mixing blade 144 Inlet 146 Filter 148 Filtrate chamber 150 Slurry chamber 152 Tapered section 154 Filtrate discharge valve 156 Conduit 174 Gas inlet 176 hollow rotating shaft 178 hollow stirring blade 180 Rotation mechanism 182 Heat transfer medium discharge hole 184 Heat transfer medium inlet hole 190 Notch 194 Inner wall T Transfer direction 196 Top plate 198 Outer wall 199 Heat transfer medium flow path 200 Heat transfer medium inlet

Claims

1. a slurry tank for storing the particulate slurry; a cleaning liquid supplying device for supplying a cleaning liquid to the slurry tank; a stirring cross-flow filtration device for concentrating the particulate slurry; a first flow path for supplying the particulate slurry stored in the slurry tank to the agitation type cross-flow filtration device; a second flow path for returning the concentrated slurry discharged from the agitation cross-flow filtration device to the slurry tank; a density sensor that generates a signal corresponding to the density of the concentrated slurry discharged from the agitated cross-flow filtration device; a control device for controlling an amount of said cleaning liquid supplied to said slurry tank by said cleaning liquid supply device based on an output of said density sensor.

2. a conductivity sensor that generates a signal corresponding to the conductivity of the filtrate discharged from the stirred cross-flow filtration device; The device for concentrating a microparticle slurry as described in claim 1, characterized in that the control device switches from the initial concentration process to the dilution washing process, or from the final concentration process to the discharge process, or indicates the timing of the switching based on the output of the density sensor, while switching from the dilution washing process to the final concentration process, or indicates the timing of the switching, based on the output of the density sensor and the output of the conductivity sensor. an initial concentration step of supplying the fine particle slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating mother liquor in the fine particle slurry and obtaining an initial concentrated slurry; a dilution and washing step of supplying a washing liquid to the slurry tank by the washing liquid supply device, supplying the initially concentrated slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby diluting and washing the initially concentrated slurry to obtain a washing slurry; a final concentration step of stopping the supply of the cleaning liquid to the slurry tank by the cleaning liquid supply device, supplying the cleaning slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating the cleaning liquid from the cleaning slurry and obtaining a final concentrated slurry; and Discharging the final concentrated slurry from the agitated cross-flow filtration apparatus.

3. a second density sensor for generating a signal corresponding to the density of the filtrate discharged from the stirred cross-flow filtration device; The device for concentrating a fine particle slurry as described in claim 1, characterized in that the control device switches from the initial concentration process to the dilution washing process, from the dilution washing process to the final concentration process, or from the final concentration process to the discharge process, or indicates the timing of switching, based on outputs from the density sensor and the second density sensor. an initial concentration step of supplying the fine particle slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating mother liquor in the fine particle slurry and obtaining an initial concentrated slurry; a dilution and washing step of supplying a washing liquid to the slurry tank by the washing liquid supply device, supplying the initially concentrated slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby diluting and washing the initially concentrated slurry to obtain a washing slurry; a final concentration step of stopping the supply of the cleaning liquid to the slurry tank by the cleaning liquid supply device, supplying the cleaning slurry stored in the slurry tank to the agitation type cross-flow filtration device through the first flow path, and returning the concentrated slurry discharged from the agitation type cross-flow filtration device to the slurry tank through the second flow path, thereby separating the cleaning liquid from the cleaning slurry and obtaining a final concentrated slurry; and Discharging the final concentrated slurry from the agitated cross-flow filtration apparatus.

4. The control device for concentrating microparticle slurry as described in claim 2 or 3, characterized in that in the dilution cleaning process, based on the output of the density sensor, if the density of the concentrated slurry is lower than the lower limit of the target density range, the control device reduces the amount of the cleaning liquid supplied by the cleaning liquid supply device or stops the supply, and if the density of the concentrated slurry is higher than the upper limit of the target density range, the control device increases the amount of the cleaning liquid supplied by the cleaning liquid supply device or starts the supply, thereby performing feedback control.

5. The control device for concentrating fine particle slurry as described in claim 2, characterized in that, in the initial concentration process, the control device compares the output of the density sensor with a slurry density corresponding to a predetermined value within the range of a solid content concentration of the concentrated slurry of 35 to 65 wt%, and switches to the dilution cleaning process when the density sensor reaches a slurry density corresponding to the predetermined value, or indicates the timing for switching to the dilution cleaning process.

6. The control device for concentrating fine particle slurry as described in claim 3, characterized in that in the initial concentration process, based on the outputs of the density sensor and the second density sensor, switches to the dilution and washing process when the solid concentration of the concentrated slurry reaches a predetermined value within the range of 35 to 65 wt%, or indicates the timing for switching to the dilution and washing process.

7. 3. The apparatus for concentrating a fine particle slurry according to claim 2, wherein the control device compares the output of the density sensor with a slurry density corresponding to a predetermined value within a range of a solid content concentration of the concentrated slurry of 50 to 65 wt % in the final concentration step, and transitions to the discharge step when the density sensor reaches a slurry density corresponding to the predetermined value.

8. The device for concentrating fine particle slurry as described in claim 3, characterized in that in the final concentration process, the control device transitions to the discharge process when the solid concentration of the concentrated slurry reaches a predetermined value within the range of 50 to 65 wt% based on the output of the density sensor and the second density sensor.

9. The device for concentrating a microparticle slurry according to any one of claims 1 to 3, characterized in that the density sensor is a vibrating in-line density sensor having a vibrator in contact with the concentrated slurry and a controller that vibrates the vibrator and measures its resonant frequency.

10. The stirring type cross-flow filtration device has a slurry chamber and a filtrate chamber separated by a filter, an agitator arranged along the filter in the slurry chamber, and a drive unit that moves the agitator along the filter to prevent fine particles from accumulating on the surface of the filter, and is characterized in that it concentrates the fine particle slurry passing through the slurry chamber.

11. 4. The device for concentrating a microparticle slurry according to claim 1, wherein the microparticles in the microparticle slurry are a precursor of a positive electrode material for a secondary battery.

12. A concentrating device for a fine particle slurry according to any one of claims 1 to 3, The device further includes a stirring and heat transfer drying device for drying the concentrated slurry supplied from the device for concentrating the fine particle slurry, The stirring heat transfer drying device is a casing having an inlet at one end and an outlet at the other end; A plurality of rotating shafts are arranged in the casing so as to be rotatable about axes and the axes are parallel to each other; Agitating blades are fixed to each of the rotating shafts at intervals in the axial direction and such that the agitating blades of each rotating shaft overlap each other when viewed in the axial direction; A heating mechanism for heating the stirring blades is provided, This device for producing fine particle powder is characterized in that by rotating the rotating shaft, the heated stirring blade heats the concentrated slurry supplied from the inlet and transports it to the outlet hole, during which the concentrated slurry is dried and converted into fine particle powder.

13. a dilution washing filtration step of adding a washing liquid to a slurry containing fine particles having a particle size of 7 μm or less and a mother liquor, and filtering the resulting slurry using an agitation cross-flow filtration device to obtain a washing slurry; A concentrating step of concentrating the washed slurry by the agitation type cross-flow filtration apparatus to obtain a concentrated slurry; A drying step of heating and drying the concentrated slurry to obtain a fine particle powder, In the dilution, washing and filtering step, the density of the washing slurry is measured by a density sensor, and if the density of the washing slurry measured by the density sensor is lower than a lower limit of a target range, the supply amount of the washing liquid in the dilution, washing and filtering step is reduced or the supply is stopped, and if the density of the washing slurry measured by the density sensor is higher than an upper limit of the target range, the supply amount of the washing liquid in the dilution, washing and filtering step is increased or the supply is started, thereby performing feedback control.

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