JP7176326B2 - Method for producing dried lithium hydroxide - Google Patents

Description

The present invention relates to a method for producing dry lithium hydroxide.

In recent years, along with the rapid expansion of small electronic devices such as mobile phones and laptop computers, the demand for lithium secondary batteries as a chargeable/dischargeable power source has increased rapidly. Composite oxides containing lithium, such as lithium-cobalt composite oxides and lithium-nickel composite oxides, are used as positive electrode active materials for positive electrodes of lithium secondary batteries.

As a method for producing a lithium-containing composite oxide, for example, Patent Document 1 discloses that a lithium salt and a nickel salt are mixed so that the Li/Ni molar ratio is at least 1, and sintered to obtain LiNiO ₂ for a positive electrode material. A positive electrode for a lithium secondary battery, wherein a mixture of a lithium salt and a nickel salt is calcined at 500° C. to 1000° C. for 10 hours or more in air and/or oxygen containing 1% or more ozone. A method of making the material is disclosed.

Furthermore, Patent Document 1 also discloses an example using anhydrous lithium hydroxide as a lithium salt. Specifically, an example is disclosed in which a mixture of nickel hydroxide and anhydrous lithium hydroxide is heated and sintered in an atmosphere-controlled furnace to produce a positive electrode active material for a lithium secondary battery.

By the way, since lithium hydroxide is usually hydrated to form a monohydrate, it is necessary to dehydrate the lithium hydroxide hydrate to make it anhydrous in order to obtain anhydrous lithium hydroxide. .

For example, Patent Document 2 discloses a method for dehydrated lithium hydroxide monohydrate, which is characterized by dehydrating lithium hydroxide monohydrate by heating it to a core tube temperature of 150° C. or higher using a rotary kiln. disclosed.

JP-A-8-180863 JP-A-2006-265023

However, when lithium hydroxide hydrate is dehydrated by heat treatment, it may take a long time for the dehydration treatment. Therefore, there has been a demand for a method for producing dry lithium hydroxide that can produce dry lithium hydroxide.

In view of the problems of the prior art described above, it is an object of one aspect of the present invention to provide a method for producing dry lithium hydroxide that can produce dry lithium hydroxide in a short period of time.

In order to solve the above problems, in one aspect of the present invention,
It has a cylindrical stirring chamber, stirring means arranged at the bottom of the stirring chamber and provided with stirring blades, and heating means for supplying a heat medium to the inside of the side wall of the stirring chamber to heat the inside of the stirring chamber. of a tumbling agitator with heating means,
a drying step of putting lithium hydroxide hydrate into the stirring chamber and heating the lithium hydroxide hydrate with the heating means while stirring the lithium hydroxide hydrate with the stirring means;
During the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber is higher than the height of the lithium hydroxide hydrate put into the stirring chamber, and the side wall and the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber, and the lithium hydroxide water introduced into the stirring chamber. Provided is a method for producing dry lithium hydroxide in which the stirring blades of the stirring means are rotated such that the height difference from the hydrated material is 5% or more of the height of the side wall .

According to one aspect of the present invention, it is possible to provide a method for producing dry lithium hydroxide that can produce dry lithium hydroxide in a short period of time.

Explanatory drawing of the tumbling stirrer with a heating means.

Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. Various modifications and substitutions can be made to.
[Method for producing dry lithium hydroxide]
A configuration example of the method for producing dry lithium hydroxide according to the present embodiment will be described.

In the method for producing dry lithium hydroxide according to the present embodiment, lithium hydroxide hydrate is placed in the stirring chamber of a tumbling stirrer with heating means, and while the lithium hydroxide hydrate is stirred by the stirring means, the heating means It can have a drying step heated by

The tumbling stirrer with heating means includes a cylindrical stirring chamber, a stirring means arranged at the bottom of the stirring chamber and equipped with stirring blades, and a heating medium supplied to the inside of the side wall of the stirring chamber. and a heating means for heating. During the drying process, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber is higher than the height of the lithium hydroxide hydrate introduced into the stirring chamber, and the height of the side wall of the stirring chamber is It is preferable to rotate the stirring blade of the stirring means so as to be positioned in the range of 96% or less of the height.

Here, first, a configuration example of a tumbling stirrer with heating means used in the method for producing dry lithium hydroxide according to the present embodiment will be described with reference to FIG.

FIG. 1 schematically shows a cross-sectional view along a plane parallel to the rotating shaft passing through the rotating shaft of the stirring blade provided at the bottom of the stirring chamber.

The heated tumbling stirrer 10 can have a cylindrical stirring chamber 11, ie the sample chamber.

Note that the stirring chamber 11 does not have to be perfectly cylindrical, and for example, the connecting portion 111 between the bottom surface and the side wall may be configured to have a curved cross section as shown in FIG. can.

The bottom of the stirring chamber 11 can have stirring means 12 with stirring blades 121 . The stirring means 12 has a motor (not shown), and the motor rotates the stirring blade 121 at a desired peripheral speed to stir the lithium hydroxide in the stirring chamber 11 .

A side wall 13 of the stirring chamber 11 has a jacket structure, that is, a hollow structure having a space (gap) (not shown) inside the side wall. A heating means for heating the inside of the stirring chamber 11 is arranged. In addition, it is also possible to form a space inside the bottom surface of the stirring chamber 11 in the same manner, and supply a heating medium to the space so that heating can be performed.

A cover (not shown) can be provided on the upper surface of the stirring chamber 11 during the drying process, so that the stirring material in the stirring chamber 11 does not scatter and the atmosphere in the stirring chamber 11 can be controlled. .

In the method for producing dry lithium hydroxide according to the present embodiment, lithium hydroxide hydrate, which is a raw material for dry lithium hydroxide, can be first put into the stirring chamber 11 when performing the drying step.
The amount of lithium hydroxide hydrate introduced into the stirring chamber 11 is not particularly limited.
However, it is preferable not to add too much lithium hydroxide hydrate so that the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber, which will be described later, during the drying step is within a predetermined range. . For example, lithium hydroxide hydrate is charged so that the height of the lithium hydroxide hydrate charged into the stirring chamber (sample charging height) is 60% or less of the height of the side wall 13 of the stirring chamber 11. It is preferable to add lithium hydroxide hydrate so that the content becomes 50% or less.
Also, from the viewpoint of productivity, lithium hydroxide hydrate is added so that the height of the lithium hydroxide hydrate put into the stirring chamber is 10% or more of the height of the side wall 13 of the stirring chamber 11, for example. It is preferable to add lithium hydroxide hydrate, and it is more preferable to add lithium hydroxide hydrate so that the content becomes 20% or more.

The lithium hydroxide hydrate can be, for example, lithium hydroxide monohydrate, since lithium hydroxide normally hydrates to form lithium hydroxide monohydrate.

Although the powder characteristics of the lithium hydroxide hydrate are not particularly limited, for example, the content of fine powder having a particle size of 100 μm or less is preferably 8% by mass or less. This is because when the content of fine powder having a particle size of 100 μm or less in the lithium hydroxide hydrate is 8% by mass or less, it becomes easier to flow when stirred by the stirring means 12, and the drying time can be shortened. .

Then, in the drying step, the stirring means 12 can rotate the stirring blade 121 to stir the lithium hydroxide monohydrate.

At this time, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber is higher than the height of the lithium hydroxide hydrate introduced into the stirring chamber, and is 96% of the height of the side wall of the stirring chamber. It is preferable to rotate the stirring blades of the stirring means so as to be positioned within the following range.
In this specification, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber is the maximum height of the lithium hydroxide hydrate that is in contact with the side wall of the stirring chamber while being stirred during the drying process. It means the height of the point and can be measured, for example, on the basis of the marks left on the side walls in the stirring chamber after the drying process. The height of the lithium hydroxide hydrate introduced into the stirring chamber is the height of the lithium hydroxide hydrate when the upper surface of the lithium hydroxide hydrate introduced into the stirring chamber is flattened before the drying step. means the height of the top surface of the Also, the height of the side wall of the stirring chamber means the height of the upper end of the side wall that defines the stirring chamber.
The maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber, the height of the lithium hydroxide hydrate charged into the stirring chamber, and the height of the side wall of the stirring chamber are all means the height of each position based on the lowest position of the bottom of the

In the tumbling stirrer with heating means, at least the portion of the side wall 13 is heated by the heating means. Therefore, in order to produce dry lithium hydroxide in a short period of time, it is preferable to stir the lithium hydroxide hydrate and maintain a wide contact area with the side wall 13 in the stirring chamber 11 .

During the drying process, the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber is the height of the lithium hydroxide hydrate charged into the stirring chamber before the drying process, that is, the charging height of the sample. The effect of the present invention can be obtained by increasing the height. During the drying step, the difference between the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber and the height of the charged sample is preferably 5% or more of the height of the side wall of the stirring chamber. More preferably 10% or more.

However, if the maximum reaching height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber is excessively increased, the stirred lithium hydroxide hydrate reaches the lid (not shown). If it is a general powder other than lithium hydroxide hydrate, even if it comes into contact with the cover of the stirring chamber 11, it will drop due to gravity and will be stirred by the stirring means 12 again. On the other hand, when the lithium hydroxide hydrate reaches the lid after being in contact with the side wall 13 and heated, it easily adheres to the lid. For this reason, if the stirred lithium hydroxide hydrate reaches the lid excessively, the lithium hydroxide hydrate from which the moisture has not been sufficiently removed adheres to the lid, causing a decrease in drying efficiency. Become. In addition, it may be difficult to recover the dried lithium hydroxide after the drying step.

Therefore, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber is preferably 96% or less, more preferably 95% or less, of the height of the side wall of the stirring chamber 11. It is more preferable to make it 90% or less.

In the drying process, there is no particular limitation on the peripheral speed when the stirring means 12 for stirring the lithium hydroxide hydrate in the stirring chamber rotates the stirring blades 121 . However, during the drying process, it is preferable that the peripheral speed v (m/s) of the stirring blade 121 of the stirring means 12 and the average particle size D (μm) of the lithium hydroxide hydrate satisfy the following relationship.
For example, when the lithium hydroxide hydrate supplied to the stirring chamber contains 8% by mass or less of fine powder having a particle size of 100 μm or less, it is preferable to satisfy the following formula (1).

0.03×D−7≦v≦0.03×D+1 (1)
Further, when the lithium hydroxide hydrate supplied to the stirring chamber contains more than 8% by mass of fine powder having a particle size of 100 μm or less, it is preferable to satisfy the following formula (2).

0.03×D−11≦v≦0.03×D−7 (2)
This is because the peripheral velocity v (m/s) and the average particle size D (μm) of the lithium hydroxide satisfy the above relationship, so that the drying time can be particularly shortened, which is preferable. .

Although the reason for this is not clear, by setting the peripheral speed v of the stirring blade 121 within the above range, the lithium hydroxide hydrate in the stirring chamber 11 can be appropriately rolled up and scattered. It is considered that the heat from the heating means supplied inside can be sufficiently heated. Also, it is considered that the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber can be set to an appropriate height.

The average particle size D (μm) means the particle size at 50% of the volume integrated value in the particle size distribution determined by the dry laser diffraction/scattering method. Average particle size has a similar meaning herein.

The shape of the stirring blades installed in the stirring chamber 11 is not particularly limited, and various stirring blades can be used. However, it is preferable to use a stirring blade having a shape that facilitates rolling up the lithium hydroxide hydrate so that the side wall in the stirring chamber 11 and the lithium hydroxide hydrate are easily brought into contact with each other. For example, the stirring blades 121 are preferably one or more selected from pitched paddle type, flat paddle type, anchor paddle type, pitched turbine type, flat turbine type, ribbon type, and screw type.

The stirring impeller is preferably for high load or high circulation.

In addition, a baffle plate is arranged on the side wall 13 of the stirring chamber 11 so that the lithium hydroxide hydrate stirred by the stirring blade 121 can easily move upward along the side wall 13 of the stirring chamber 11. can also The baffle plate is preferably arranged along the height direction, for example, on the side wall 13 of the stirring chamber 11 .

In the drying step, as described above, while the lithium hydroxide hydrate in the stirring chamber 11 is being stirred by the stirring means 12, the lithium hydroxide water is heated by the heating means provided on the side wall 13 of the stirring chamber 11. The hydrate can be heated and dried.

As described above, the side wall 13 of the stirring chamber 11 has a jacket structure with a space (not shown) inside, and a heating medium such as steam can be supplied into the gap of the jacket structure for heating.

The temperature of the heat medium supplied to the inner space of the side wall 13 of the stirring chamber 11 is not particularly limited. A range of 200° C. or lower is more preferable.

As described above, when steam is used as a heat medium, the heating temperature in the drying step is preferably 100° C. or higher and 150° C. or lower from the viewpoint of ease of operation and simplification of equipment. Incidentally, the heating temperature is the temperature of the heat medium to be supplied as described above, and the surface temperature of the side wall 13 inside the stirring chamber 11 is generally the same temperature as that of the heat medium. 11 can be rephrased as the temperature of the inner surface.

In the drying step, the water of crystallization of the lithium hydroxide hydrate can be sufficiently removed (dehydrated) by heating and drying within the above temperature range, and the time required for the drying step can be shortened.

The atmosphere in the stirring chamber 11 when drying the lithium hydroxide hydrate is not particularly limited, but any atmosphere selected from an air atmosphere, a nitrogen atmosphere, and a vacuum atmosphere can be preferably used.

When a vacuum atmosphere is used, the vacuum pressure is preferably -70 kPa or less. In this specification, the vacuum pressure is indicated by gauge pressure (relative pressure). This is because drying (dehydration reaction) can be promoted by setting the vacuum pressure to −70 kPa or less. The lower limit of the vacuum pressure is not particularly limited, but since a vacuum pump with high exhaust capacity is required to achieve a high vacuum, it is preferably −90 kPa or more from the viewpoint of cost reduction.

The drying time (heating time) in the drying step is not particularly limited. For example, considering the amount of lithium hydroxide hydrate to be subjected to the drying step, the heating temperature, etc., the lithium hydroxide hydrate can be sufficiently dried. For example, the water content of anhydrous lithium hydroxide is preferably 10 mass. % or less, more preferably 5 mass % or less, and particularly preferably 1 mass % or less.

The drying time can be, for example, 200 minutes or more and 250 minutes or less. The drying time is the time during which the heating medium heated to the above-described heating temperature is supplied to the space inside the side wall 13 of the stirring chamber 11, and the temperature of the surface of the side wall 13 inside the stirring chamber 11 is It can also be rephrased as the time held at the heating temperature described above.

After completion of the drying process, dry lithium hydroxide can be obtained. Hydrated water and adsorbed water are removed from dry lithium hydroxide, and it can be made into anhydrous lithium hydroxide.

Note that if moisture is adsorbed on the dried lithium hydroxide after the drying step, the formation of lithium carbonate is promoted, so it is preferable to keep the dried lithium hydroxide in a dry state after the drying step. In a mass production process on an industrial scale, it is preferable to keep the lithium hydroxide dry by storing it under controlled moisture and carbon dioxide gas partial pressures.
[Method for producing lithium-nickel composite oxide]
Various lithium-containing compounds can be produced using the method for producing dry lithium hydroxide of the present embodiment. Here, one configuration example of a method for producing a lithium-nickel composite oxide will be described.

The composition of the lithium-nickel composite oxide finally obtained by the method for producing the lithium-nickel composite oxide of the present embodiment is not particularly limited, and can be any composition.

However, the general formula: Li _x Ni _(1-yz) M _y N _z O _2+α (wherein M is at least one selected from Co and Mn, N is at least one selected from Al and Ti) 1 type, and 0.95 ≤ x ≤ 1.15, 0.05 ≤ y ≤ 0.35, 0.005 ≤ z ≤ 0.8, −0.2 ≤ α ≤ 0.2). It is preferably a lithium-nickel composite oxide represented by

As the lithium-nickel composite oxide, composite oxides having various compositions have been proposed, but the lithium-nickel composite oxide represented by the above general formula is preferable in that it has excellent battery characteristics. By applying the method for producing a lithium-nickel composite oxide according to No. 1, it is possible to obtain a positive electrode active material that stably has excellent charge-discharge characteristics even in a mass production process on an industrial scale.

Here, the M element in the general formula is Co and / or Mn, and by setting y in the above range, the cycle characteristics while suppressing the decrease in battery capacity when used as a positive electrode material for a lithium secondary battery. can be improved. It is particularly preferable that y is in the range of 0.1 or more and 0.2 or less.

In addition, the N element in the general formula is Al and / or Ti, and by setting z in the above range, thermal stability while suppressing a decrease in battery capacity when used as a positive electrode material for a lithium secondary battery. can be improved. It is particularly preferable that z is in the range of 0.02 or more and 0.05 or less.

The method for producing a lithium-nickel composite oxide according to the present embodiment can have the following steps.

A mixing step to form a mixture of dry lithium hydroxide and a nickel compound.

A firing step of firing the mixture.

Each step will be described below.
(Mixing process)
In the mixing step, a mixture of the dry lithium hydroxide obtained by the method for producing dry lithium hydroxide described above and the nickel compound can be formed.

The nickel compound used at this time is not particularly limited, and nickel compounds that are generally used as raw materials for lithium-nickel composite oxides can be used.

As the nickel compound, it is particularly preferable to use one or more selected from nickel composite hydroxides and nickel composite oxides from the viewpoint of reducing contamination with impurities and controlling particle diameters. Specifically, a nickel composite hydroxide or a nickel composite oxide can be used according to the target composition of the lithium-nickel composite oxide to be prepared. can be used at least one selected from Ni(1 _{-yz) MyNz (} OH) _2+β and Ni _{(1-yz) MyNzO1 + γ} .

Note that y and z in the general formula of the nickel composite hydroxide and nickel composite oxide preferably have the same ranges as in the general formula of the lithium-nickel composite oxide described above. Also, β and γ preferably satisfy the ranges of −0.2≦β≦0.2 and −0.2≦γ≦0.2.

The nickel composite hydroxide may be obtained by a conventional method, and is not particularly limited. can be preferably used. Further, the nickel composite oxide is preferably obtained by oxidative roasting of a compound containing nickel and an additive element, and more preferably, for example, obtained by oxidative roasting of the nickel composite hydroxide.

When nickel composite hydroxide and/or nickel composite oxide is used as a raw material, the average particle size of the secondary particles of these raw materials is not particularly limited, but is preferably in the range of 5 μm or more and 20 μm or less. More preferably, the range is 8 μm or more and 15 μm or less. Since the average particle size of the raw material is inherited by the obtained lithium-nickel composite oxide, by setting the average particle size within the above range, good filling properties and high reactivity with the electrolyte when used in batteries can be achieved. and the battery characteristics can be improved.

The amount of dry lithium hydroxide mixed with the nickel compound is not particularly limited, and can be selected according to the composition of the desired lithium-nickel composite oxide. For example, the mixing ratio can be set according to the composition of the lithium-nickel composite oxide described above. Since the composition hardly changes before and after firing, the amount of dry lithium hydroxide to be mixed with the nickel composite oxide can be easily determined from the composition of the lithium-nickel composite oxide to be obtained.

As a mixing method, a commonly used method can be used, and a general mixer can be used, such as a shaker mixer, Loedige mixer, Julia mixer, V blender, etc., to the extent that the skeleton of the nickel compound is not destroyed. , should be well mixed.
(Baking process)
In the firing step, by firing the mixture obtained in the mixing step, a lithium-nickel composite oxide can be produced.

The atmosphere during firing preferably has an oxygen concentration of 60% by volume or more, more preferably 80% by volume or more, in order to sufficiently supply oxygen. Since the atmosphere during firing can be an oxygen atmosphere, the oxygen concentration can be set to 100% by volume or less.

This is because, in the synthetic reaction of the lithium-nickel composite oxide, water is generated by the chemical reaction shown in the following reaction formula (A), for example. When a large amount of water is produced, if sufficient oxygen is not supplied from the outside, the diffusion of oxygen to the reaction field is insufficient and the reaction of reaction formula (A) does not proceed, resulting in the synthesis of lithium-nickel composite oxide. This is because there is a risk that the positive electrode active material will be degraded in battery performance, such as a decrease in battery capacity, due to a shortage.

2NiO+2LiOH+1/ _2O2 →2LiNiO2 _{+ H2O} (A)
At this time, oxygen is preferably supplied by mixing with nitrogen or an inert gas.

Moreover, the firing temperature is preferably in the range of 700° C. or higher and 780° C. or lower, and more preferably in the range of 700° C. or higher and 750° C. or lower. This is because a lithium-nickel composite oxide having sufficiently grown crystals can be obtained by setting the temperature to 700° C. or higher, and good battery performance can be obtained, which is preferable. Also, by setting the temperature to 780° C. or lower, it is possible to suppress decomposition of the produced lithium-nickel composite oxide.

In the firing step, in the process of raising the temperature to the firing temperature, the temperature range from the melting temperature of lithium hydroxide to the firing temperature, for example, 450 ° C. or higher and 650 ° C. or lower, is temporarily held to sufficiently mix the nickel compound and lithium hydroxide. is preferably reacted with.

Various furnaces that can control the atmosphere can be used for firing, but it is preferable to use an electric furnace that does not generate exhaust gas, and in industrial production, pusher furnaces, roller hearth furnaces, etc. It is preferable to use a furnace capable of continuous firing, such as

Here, the case of producing a lithium-nickel composite oxide has been described as an example, but the dry lithium hydroxide obtained by the method for producing dry lithium hydroxide of the present embodiment can be applied to the production of various lithium compounds. However, it is not limited to such a form.

EXAMPLES Hereinafter, examples of the present invention will be described more specifically in comparison with comparative examples, but the present invention is not limited by these examples.
[Example 1]
A lithium hydroxide hydrate containing fine powder having an average particle size of 620 μm and a particle size of 100 μm or less in an amount of 8.7% by mass was prepared. For lithium hydroxide hydrate, the particle size distribution was measured in a dry manner using a laser diffraction/scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., model: HRA9320 X-100). Then, from the obtained particle size distribution, the content ratio of fine powder having a particle size of 100 μm or less and the average particle size were determined.
(Drying process)
The drying process was carried out according to the following procedure.

The above lithium hydroxide hydrate was placed in a cylindrical stirring chamber 11 of a tumbling stirrer 10 (manufactured by Nippon Coke Kogyo Co., Ltd., model: FM4000) shown in FIG. In addition, four rectangular baffle plates are arranged along the height direction of the side wall 13 at regular intervals on the side wall 13 of the stirring chamber 11 . The sample input amount (sample input height) was 30% of the height of the side wall of the stirring chamber 11 .

Then, a lid portion was set on the top of the stirring chamber 11 to seal the stirring chamber 11, and the atmosphere in the stirring chamber 11 was reduced from the atmospheric pressure to a vacuum atmosphere (-90 kPa).

Next, steam was supplied to the inside of the side wall 13 of the tumbling stirrer 10 with heating means, that is, the inside of the jacket at a gauge pressure of 0.19 MPa (equivalent to 130°C).

At this time, the stirring blade 121 of the stirring means 12 provided at the bottom of the stirring chamber 11 was rotated at a peripheral speed of 10.5 m/s. The stirring blade 121 is a flat paddle type stirring blade for high load.

Then, when the temperature measured at the central portion of the tumbling stirrer 10 with heating means reaches 65°C, the temperature measured at the central portion of the tumbling stirrer 10 with heating means reaches 120°C. The time until drying was defined as drying time, and heating and stirring were continued under the above conditions.

After starting to supply steam into the side wall 13 of the tumbling stirrer 10 with the heating means, the side wall 13 of the tumbling stirrer 10 with the heating means is The temperature measured at the central portion of the stirring chamber 11 away from is stabilized at around 65°C. After that, when the drying (dehydration) is nearing completion, the temperature gradually rises, and the temperature measured at the center of the stirring chamber 11 of the tumbling stirrer 10 with heating means reaches about 120° C., which is close to the temperature of the supplied steam. The temperature is raised to Then, after confirming that the temperature measured at the central part of the stirring chamber 11 of the tumbling stirrer 10 with heating means reached 120° C., the supply of steam was stopped, the heating was stopped, and the mixture was cooled. In addition, while steam is being supplied into the side wall 13 of the tumbling stirrer 10 with heating means, the surface of the side wall 13 inside the stirring chamber 11 and the vicinity of the side wall 13 are at approximately the same temperature as the steam supplied inside the side wall 13. , that is, about 130°C. For this reason, the drying time is the time during which the aforementioned steam is supplied into the side wall 13 of the tumbling stirrer 10 with heating means, and the surface of the side wall 13 inside the stirring chamber 11 is at the temperature of the supplied steam. It can also be rephrased as the time during which it is heated and held.

After the drying process was completed under the above conditions, the maximum height of the lithium hydroxide hydrate in contact with the side wall 13 in the stirring chamber during the drying process was measured from the mark left on the side wall. 70% of the height was confirmed.

The drying time, which is the time required for the drying step, was 220 minutes, and the moisture content of the obtained dry lithium hydroxide, that is, anhydrous lithium hydroxide, was 0.1% by mass. In the following other examples and comparative examples, the water content of the anhydrous lithium hydroxide obtained after the drying process was about 0.1% by mass.

Regarding the evaluation of the drying time, if the time required for the drying process is 225 minutes or less, it is A, if it is longer than 225 minutes and 250 minutes or less, it is B, and if it exceeds 250 minutes, it is C. Shown in Table 1. .
[Example 2]
The drying process was carried out under the same conditions as in Example 1, except that the baffle plate on the side wall of the stirring chamber was removed as the tumbling stirrer with heating means in the drying process.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured and found to be 67% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Example 3]
The drying step was carried out under the same conditions as in Example 2, except that the stirring blades of the stirring means in the drying step were pitched paddle type stirring blades. In addition, the stirring impeller is a high-load impeller.
After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 62% of the height of the side wall of the stirring chamber.
Other evaluation results are shown in Table 1.
[Example 4]
The drying step was carried out under the same conditions as in Example 2, except that the stirring blades of the stirring means were rotated at a peripheral speed of 7.9 m/s in the drying step.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 51% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Example 5]
The drying process was carried out under the same conditions as in Example 2, except that the stirring blades of the stirring means were rotated at a peripheral speed of 7.1 m/s in the drying process.
After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured and found to be 43% of the height of the side wall of the stirring chamber.
Other evaluation results are shown in Table 1.
[Comparative Example 1]
The drying step was carried out under the same conditions as in Example 2, except that the stirring blades of the stirring means were rotated at a peripheral speed of 6.4 m/s in the drying step.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 30% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Comparative Example 2]
The drying process was carried out under the same conditions as in Example 2, except that the stirring blades of the stirring means were rotated at a peripheral speed of 11.8 m/s in the drying process.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 97% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.

After the drying step was completed, when the cover of the stirring chamber of the tumbling stirrer with heating means was opened, it was confirmed that lithium hydroxide was adhered to the cover.
[Example 6]
A lithium hydroxide hydrate containing 7.5% by mass of fine powder having an average particle size of 625 μm and a particle size of 100 μm or less was prepared. For lithium hydroxide hydrate, the particle size distribution was measured in a dry manner using a laser diffraction/scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., model: HRA9320 X-100). Then, from the obtained particle size distribution, the content ratio of fine powder having a particle size of 100 μm or less and the average particle size were determined.

Then, the use of the above lithium hydroxide hydrate, the amount of sample input (sample input height) set to 35% of the height of the side wall of the stirring chamber 11, and the drying process of the stirring means The drying step was carried out under the same conditions as in Example 2, except that the stirring blades were rotated at a peripheral speed of 17.7 m/s.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 82% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Example 7]
The drying process was carried out under the same conditions as in Example 6, except that the stirring blades of the stirring means were rotated at a peripheral speed of 13.3 m/s in the drying process.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 51% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Example 8]
The drying step was carried out under the same conditions as in Example 6, except that the stirring blades of the stirring means were rotated at a peripheral speed of 12.5 m/s in the drying step.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 45% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Example 9]
The drying step was carried out under the same conditions as in Example 6, except that the stirring blades of the stirring means were rotated at a peripheral speed of 11.4 m/s in the drying step.
After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 40% of the height of the side wall of the stirring chamber.
Other evaluation results are shown in Table 1.
[Comparative Example 3]
The drying step was carried out under the same conditions as in Example 6, except that the stirring blades of the stirring means were rotated at a peripheral speed of 10.5 m/s in the drying step.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 35% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.
[Comparative Example 4]
The drying step was carried out under the same conditions as in Example 6, except that the stirring blades of the stirring means were rotated at a peripheral speed of 19.9 m/s in the drying step.

After the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was measured, and it was confirmed to be 97% of the height of the side wall of the stirring chamber.

Other evaluation results are shown in Table 1.

After the drying step was completed, when the cover of the stirring chamber of the tumbling stirrer with heating means was opened, it was confirmed that lithium hydroxide was adhered to the cover.

表１に示した結果によると、実施例１～実施例９の結果から、乾燥工程の間、撹拌室内の側壁と接する水酸化リチウム水和物の最高到達高さを、撹拌室に投入された水酸化リチウム水和物の高さよりも高く、側壁の高さの９６％以下の範囲内とすることで、蓋部への固着を防ぎつつ、乾燥時間を短くできることを確認できた。

According to the results shown in Table 1, from the results of Examples 1 to 9, during the drying process, the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber was put into the stirring chamber. It was confirmed that the drying time can be shortened while preventing sticking to the lid by making the height higher than the height of the lithium hydroxide hydrate and within the range of 96% or less of the height of the side wall.

On the other hand, as is clear from the results of Comparative Examples 1 and 3, the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber during the drying process was , the drying time greatly exceeds 250 minutes, and it has been confirmed that the drying time is long.

Moreover, as is clear from the results of Comparative Examples 2 and 4, when the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step exceeds 96% of the height of the side wall, It was confirmed that the lid part adhered and the drying time exceeded 250 minutes, which was a long time.

Incidentally, as is clear from the comparison between, for example, Example 2 and Example 3, the maximum height of the lithium hydroxide hydrate in contact with the side wall of the stirring chamber during the drying step was reached regardless of the shape of the stirring blade. was within a predetermined range, it was confirmed that the drying time could be shortened.
Furthermore, the drying process was also carried out by changing the stirring blades to the anchor paddle type, pitched turbine type, flat turbine type, ribbon type, and screw type. As a result, when the peripheral speed of the stirring blade was adjusted so that the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber was the same as in the above Examples and Comparative Examples, and the drying process was carried out. , and the drying time, the evaluation results were the same as those of the above Examples and Comparative Examples. That is, regardless of the shape of the stirring blade, it was confirmed that the relationship between the maximum height of lithium hydroxide hydrate in contact with the side wall of the stirring chamber and the drying time was the same as in the above examples and comparative examples. did it.

10 Rolling Stirrer with Heating Means 11 Stirring Chamber 12 Stirring Means 121 Stirring Blade 13 Side Wall

Claims (6)

It has a cylindrical stirring chamber, stirring means arranged at the bottom of the stirring chamber and provided with stirring blades, and heating means for supplying a heat medium to the inside of the side wall of the stirring chamber to heat the inside of the stirring chamber. of a tumbling agitator with heating means,
a drying step of putting lithium hydroxide hydrate into the stirring chamber and heating the lithium hydroxide hydrate with the heating means while stirring the lithium hydroxide hydrate with the stirring means;
During the drying step, the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber is higher than the height of the lithium hydroxide hydrate put into the stirring chamber, and the side wall and the maximum height of the lithium hydroxide hydrate in contact with the side wall in the stirring chamber, and the lithium hydroxide water introduced into the stirring chamber. A method for producing dry lithium hydroxide, wherein the stirring blade of the stirring means is rotated such that the height difference from the hydrated material is 5% or more of the height of the side wall . The dry lithium hydroxide according to claim 1, wherein the stirring blade is one or more selected from pitched paddle type, flat paddle type, anchor paddle type, pitched turbine type, flat turbine type, ribbon type, and screw type. Production method. 3. The method for producing dry lithium hydroxide according to claim 1, wherein a baffle plate is arranged on the side wall of the stirring chamber. In the lithium hydroxide hydrate, the content of fine powder having a particle size of 100 μm or less is 8% by mass or less,
During the drying step, the peripheral speed v (m/s) of the stirring blade of the stirring means satisfies the relationship between the average particle size D (μm) of the lithium hydroxide hydrate and the following formula (1). The method for producing dry lithium hydroxide according to any one of claims 1 to 3, wherein
0.03×D−7≦v≦0.03×D+1 (1) The lithium hydroxide hydrate contains more than 8% by mass of fine powder having a particle size of 100 μm or less,
During the drying step, the peripheral speed v (m/s) of the stirring blade of the stirring means satisfies the relationship between the average particle diameter D (μm) of the lithium hydroxide hydrate and the following formula (2). The method for producing dry lithium hydroxide according to any one of claims 1 to 3, wherein
0.03×D−11≦v≦0.03×D−7 (2) The method for producing dry lithium hydroxide according to any one of claims 1 to 4, wherein the lithium hydroxide hydrate contains 8% by mass or less of fine powder having a particle size of 100 µm or less.

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