Method for producing lithium hydroxyde andydride and rotary kiln

Abstract

This invention provides a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln, comprising: a supply step wherein the lithium hydroxide hydrate is supplied to an area between: a heating section, a portion of the furnace core tube covered by heating apparatus; and one end of furnace core tube; a lithium hydroxide feed step wherein the lithium hydroxide hydrate that has been supplied is fed toward the other end of furnace core tube; a drying gas delivery step wherein 100oC or higher drying gas is delivered to the area between one end of furnace core tube and heating section, when the lithium hydroxide hydrate has been supplied; and a heating step wherein, during the lithium hydroxide feed step, the lithium hydroxide hydrate is heated and dehydrated by heating apparatus under temperature higher than 450oC and no more than 600oC.

Description

METHOD FOR PRODUCING LITHIUM HYDROXYDE ANDYDRIDE AND ROTARY KILN

[0001] The present invention relates to a method for producing lithium hydroxide anhydride, and in particular to a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln, as well as a rotary kiln for use in the method.Background

[0002] Lithium hydroxide, which has been conventionally used as raw material such as for the positive electrode material in lithium ion batteries, is highly hygroscopic and usually occurs in the form of lithium hydroxide hydrate (LiOH ・ nH2O). For some products that are produced using lithium hydroxide as the raw material, it is sometimes more advantageous to use lithium hydroxide anhydride, which is not associated with the production of any water, as the raw material rather than using lithium hydroxide hydrate, which is associated with the production of large amounts of water over the course of treatment, as the raw material. In such cases, a treatment in which lithium hydroxide hydrate is heated and converted into an anhydride is carried out as a pretreatment.

[0003] JP2018-70424A discloses a method for making lithium hydroxide hydrate into an anhydride using a rotary kiln, said method comprising: a supply step in which the lithium hydroxide hydrate is supplied to an area between a heating section, which is a portion of the rotary kiln furnace core tube that is covered by the heating apparatus, and one end of the furnace core tube; a lithium hydroxide feed step in which lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; a drying gas delivery step in which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and a heating step in which, while the lithium hydroxide is fed, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to 230oC to 450oC, to produce lithium hydroxide anhydride. This method allows lithium hydroxide anhydride of high purity to be obtained, with minimal lithium hydroxide adhesion on the furnace core tube.

[0004] In the examples in JP2018-70424A, the treatment is carried out at a lithium hydroxide hydrate feed rate of 6.8 to 10.2 kg / hr, to allow lithium hydroxide anhydride of high purity to be obtained, with minimal lithium hydroxide adhesion on the furnace core tube. On the other hand, findings by the present inventors revealed that, in the treatment for making lithium hydroxide anhydrous using the rotary kiln disclosed in JP2018-70424A, the purity of the lithium hydroxide tends to decrease at a treatment rate greater than around several dozens kg / hr.SUMMARY OF THE INVENTION

[0005] In light of the circumstances noted above, an object of the present disclosure is to provide a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln, which allows lithium hydroxide anhydride of high purity to be produced even when large amounts of lithium hydroxide are produced per hour.

[0006] The inventors of the present invention engaged in extensive research to solve the problem noted above. As a result, the technology of the present disclosure was perfected upon the discovery that lithium hydroxide anhydride of high purity can be produced, even when large amounts of lithium hydroxide are produced per hour, by a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln that has a furnace core tube, and a heating apparatus surrounding at least a portion of the furnace core tube in the axial direction, the method comprising: a supply step in which the lithium hydroxide hydrate is supplied to an area between: a heating section, which is a portion of the furnace core tube that is covered by the heating apparatus; and one end of the furnace core tube; a lithium hydroxide feed step in which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; a drying gas delivery step in which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and a heating step in which, during the lithium hydroxide feed step, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride. Specifically, the present disclosure provides the following.

[0007] (1) A method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln that has a furnace core tube, and a heating apparatus surrounding at least a portion of the furnace core tube in the axial direction, the method comprising: a supply step in which the lithium hydroxide hydrate is supplied to an area between: a heating section, which is a portion of the furnace core tube that is covered by the heating apparatus; and one end of the furnace core tube; a lithium hydroxide feed step in which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; a drying gas delivery step in which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and a heating step in which, during the lithium hydroxide feed step, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride. (2) The method for producing lithium hydroxide anhydride according to (1), wherein the amount of the lithium hydroxide hydrate supplied is 2 vol% to 25 vol% based on the volume of the furnace core tube. (3) The method for producing lithium hydroxide anhydride according to (1) or (2), wherein the lithium hydroxide hydrate is heated in the heating section of the furnace core tube for 15 minutes to 4 hours. (4) The method for producing lithium hydroxide anhydride according to (1) or (2), wherein a heat-insulating material is provided on the outer peripheral surface in the area between the one end of the furnace core tube and the heating section. (5) The method for producing lithium hydroxide anhydride according to (1) or (2), wherein the rotary kiln has an exhaust pipe for expelling the drying gas, that has been heated via the above heating, to the outside of the furnace core tube, and the method furthermore comprises an exhaust step in which the heated drying gas is expelled through the exhaust pipe to the outside of the furnace core tube. (6) The method for producing lithium hydroxide anhydride according to (1) or (2), wherein the lithium hydroxide hydrate is fed at a rate of 100 kg / hr to 4000 kg / hr. (7) The method for producing lithium hydroxide anhydride according to (1) or (2), wherein the residence time of the lithium hydroxide hydrate inside the rotary kiln is more than 30 minutes. (8) A rotary kiln that has: a furnace core tube; and a heating apparatus surrounding a predetermined range in the axial direction of the furnace core tube; and that is used to produce lithium hydroxide anhydride from lithium hydroxide hydrate, the rotary kiln comprising: supply means by which the lithium hydroxide hydrate is supplied to an area between: a heating section, which is a portion of the furnace core tube that is covered by the heating apparatus; and one end of the furnace core tube; lithium hydroxide feed means by which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; drying gas delivery means by which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and heating means by which, when the lithium hydroxide is fed toward the other end of the furnace core tube, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride. (9) The rotary kiln according to (8), wherein a heat-insulating material is provided on the outer peripheral surface in the area between the one end of the furnace core tube and the heating section. (10) The rotary kiln according to (8) or (9), wherein an exhaust pipe is provided for expelling the heated drying gas to the outside of the furnace core tube in the heating section.

[0008] The present disclosure makes it possible to provide a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln, which allows lithium hydroxide anhydride of high purity to be produced even when large amounts of lithium hydroxide are produced per hour.

[0009] FIG. 1 is a schematic cross-sectional view illustrating an example of a rotary kiln that can be used in an embodiment of the method for producing lithium hydroxide anhydride of the present disclosure. The figure is a schematic cross-sectional view illustrating an example of a rotary kiln that can be used in an embodiment of the method for producing lithium hydroxide anhydride of the present disclosure.

[0010] Embodiments of the present disclosure are described below, but the present disclosure is not limited in any way by the description of the embodiments and can be carried out with additional modifications, as appropriate.

[0011] The method for producing lithium hydroxide anhydride according to an embodiment of the present disclosure is a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln having a furnace core tube and a heating apparatus surrounding at least a portion of the furnace core tube in the axial direction, the method comprising: a supply step in which the lithium hydroxide hydrate is supplied to an area between: a heating section, which is a portion of the furnace core tube that is covered by the heating apparatus; and one end of the furnace core tube; a lithium hydroxide feed step in which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; a drying gas delivery step in which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and a heating step in which, during the lithium hydroxide feed step, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride.

[0012] The method for producing lithium hydroxide anhydride according to an embodiment of the present disclosure is described in detail below with reference to the drawing, together with the configuration of a rotary kiln that can be used in such a production method.

[0013] Specifically, the rotary kiln that can be used in the method for producing lithium hydroxide anhydride according to an embodiment of the present disclosure is: a rotary kiln that has a furnace core tube and a heating apparatus surrounding a predetermined range in the axial direction of the furnace core tube, and the is used to produce lithium hydroxide anhydride from lithium hydroxide hydrate. The rotary kiln comprises: supply means by which the lithium hydroxide hydrate is supplied to an area between a heating section, which is a portion of the rotary kiln furnace core tube that is covered by the heating apparatus, and one end of the furnace core tube; lithium hydroxide feed means by which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; drying gas delivery means by which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and heating means by which, while the lithium hydroxide is fed to the other end of the furnace core tube, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride.

[0014] FIG. 1 is a schematic cross-sectional view illustrating an example of a rotary kiln that can be used in an embodiment of the method for producing lithium hydroxide anhydride of the present disclosure. As shown in the figure, the rotary kiln 10 has, as a basic structure: a furnace core tube 12; and a heating apparatus 14 surrounding a predetermined range in the axial direction of the furnace core tube 12. An inlet hood 22 is installed at one end 12a of the furnace core tube 12, and an outlet hood 24 is installed at the other end 12b of the furnace core tube 12.

[0015] A feeder 16 is connected to the one end 12a of the furnace core tube 12, and the feeder 16 has a hopper 16a and a feed tube 16b. The lithium hydroxide hydrate that is supplied to the hopper 16a is supplied via the feed tube 16b to an area between a heating section 12c and the one end 12a of the furnace core tube 12 (supply step). A screw (not shown) for feeding the lithium hydroxide hydrate into the furnace core tube 12 may be provided as appropriate inside the feed tube 16b.

[0016] The inside diameter of the furnace core tube 12 is not particularly limited, but is preferably, for example, more than 300 mm, 400 mm or more, 500 mm or more, 600 mm or more, 700 mm or more, 800 mm or more, and 900 mm or more. On the other hand, the inner diameter of the furnace core tube 12 may be 2500 mm or less, 2400 mm or less, 2300 mm or less, 2200 mm or less, 2100 mm or less, or 2000 mm or less.

[0017] When lithium hydroxide hydrate is supplied from the feeder 16 into the furnace core tube 12, a drying gas (such as nitrogen, decarbonated gas (carbon dioxide content of 0.1 ppm to 100 ppm, and preferably no more than 1 ppm), or argon) may be fed, as needed, together with the lithium hydroxide hydrate via the feed tube 16b.

[0018] The amount of lithium hydroxide hydrate supplied (filling rate) is not particularly limited, but is preferably 2% by volume or more, 3% by volume or more, 4% by volume or more, or 5% by volume or more based, on the volume of the furnace core tube 12. On the other hand, the amount of lithium hydroxide hydrate supplied (filling rate) is preferably 25% by volume or less, 20% by volume or less, 17% by volume or less, 15% by volume or less, or 12% by volume or less. An amount within this range will allow the amount that is supplied to be prevented from becoming retained in, or flowing back into, the core furnace tube 12, and will allow the lithium hydroxide hydrate to be processed into an anhydride.

[0019] The rate at which the lithium hydroxide hydrate is supplied is not particularly limited, but is preferably 100 kg / hr or more, 200 kg / hr or more, 300 kg / hr or more, or 400 kg / hr or more. On the other hand, the lithium hydroxide hydrate is preferably supplied at a rate of 4000 kg / hr or less, 3500 kg / hr or less, 3000 kg / hr or less, 2500 kg / hr or less, 2000 kg / hr or less, 1700 kg / hr or less, 1500 kg / hr or less, 1400 kg / hr or less, or 1300 kg / hr or less. A supply rate such as this during the process in which the lithium hydroxide hydrate is made into an anhydride under the conditions of the present disclosure will ensure that lithium hydroxide anhydride of high purity is readily obtained while the lithium hydroxide is prevented from adhering to, and accumulating inside, the furnace core tube.

[0020] Lithium hydroxide hydrate is supplied in the form of a powder. The average particle diameter thereof is not particularly limited but may be 10 μm to 1000 μm, for example.

[0021] The furnace core tube 12 is rotatably constructed about an axis of rotation extending in the height-wise direction of the furnace core tube 12 through the center of the cross section of the furnace, and is disposed at in incline such that the other end 12b (outlet side) is lower than the one end 12a (inlet side). The lithium hydroxide hydrate inside the core furnace tube 12 is thus fed from the one end 12a to the other end 12b (lithium hydroxide feed step).

[0022] The incline (incline relative to the horizontal plane) of the furnace core tube 12 at this time is not particularly limited and can be set in accordance with conditions such as the heating time, but may be, for example, 0.1 / 100 or more, 0.2 / 100 or more, or 0.3 / 100 or more. On the other hand, the incline of the furnace core tube 12 may be up to 3 / 100, up to 2 / 100, or up to 1 / 100.

[0023] The rotating speed of the furnace core tube 12 can be set according to conditions such as the heating time, but is preferably 0.1 rpm to 30 rpm, for example.

[0024] A material that has exceptional heat resistance and thermal conductivity and that is inert to lithium hydroxide is preferably used as the material of the furnace core tube 12. Specifically, a material such as nickel, stainless steel, or a ceramic is preferably used as the material of the furnace core tube 12, among which nickel is more preferably used. The size of the furnace core tube 12 may be set depending on the amount of lithium hydroxide hydrate that is being treated. The tube thickness of the furnace core tube 12 may be 4 mm to 12 mm, for example. Feed blades or a knocker may be disposed at the one end 12a beyond the heating section 12c of the furnace core tube 12 to ensure that the lithium hydroxide hydrate is smoothly fed.

[0025] The rotary kiln 10 is provided with a drying gas feed tube 18 for feeding a drying gas into the furnace core tube 12. The drying gas feed tube 18 is disposed such that the outlet port 18a thereof is located in the area between the one end 12a of the furnace core tube 12 and the heating section 12c. When the lithium hydroxide hydrate has been supplied into the furnace core tube 12, the drying gas is delivered via the drying gas feed tube 18 to the area between the one end 12a of the furnace core tube and the heating section 12c inside the furnace core tube 12 (drying gas delivery step). The drying gas can be delivered continuously or intermittently, but is preferably delivered continuously.

[0026] The delivery outlet 18a of the drying gas feed tube 18 is also preferably at and around where the lithium hydroxide hydrate is supplied inside the furnace core tube 12. This can ensure that lithium hydroxide adhesion and retention are prevented.

[0027] The drying gas that is used is not particularly limited, but one that is inert to lithium hydroxide is preferably used, where a decarbonated gas (a gas having a carbon dioxide content of usually 0.1 ppm to 100 ppm, and preferably no more than 1 ppm), nitrogen, or argon is preferably used.

[0028] The temperature of the drying gas fed via the drying gas feed tube 18 is not particularly limited, provided that it is at least 100oC, but is preferably at least 120oC, at least 150oC, or at least 170oC. The temperature of the drying gas fed via the drying gas feed tube 18 is also preferably no more than 460oC, no more than 400oC, no more than 350oC, or no more than 300oC. Temperatures such as the above can ensure that lithium hydroxide is prevent from adhering inside the furnace core tube 12.

[0029] The amount in which the drying gas is supplied is not particularly limited, but is preferably 10 m3 / hr to 3000 m3 / hr, 50 m3 / hr to 2500 m3 / hr, or 80 m3 / hr to 2000 m3 / hr.

[0030] A heat-insulating material 30 is preferably provided on the outer peripheral surface of the furnace core tube 12 including where the drying gas is supplied (area between the one end 12a of the furnace core tube 12 and the heating section 12c). This will make it possible to prevent decreases in the temperature of the furnace core tube 12 and its interior caused by the drying gas.

[0031] The heat-insulating material is not particularly limited, but polyurethane foam, glass wool, and ceramic fiber board can be used, for example.

[0032] At least a portion of the furnace core tube 12 in the entire axial direction is surrounded by the heating apparatus 14. The heating apparatus 14 is not as wide as the length of the furnace core tube 12 in the axial direction, and the heating apparatus 14 is disposed in the central portion at intervals from the one end 12a and the other end 12b of the furnace core tube 12. The lithium hydroxide hydrate that has been supplied into the furnace core tube 12 is heated by the heating apparatus 14 during the process of being transported from the one end 12a to the other end 12b (heating step).

[0033] The temperature of the heating furnace 14 is not particularly limited, provided that it is >450°C to ≦600°C, but is preferably 460°C or higher, 470°C or higher, 480°C or higher, 490°C or higher, or 500°C or higher. At a temperature lower than this, it may not be possible to sufficiently dehydrate the lithium hydroxide hydrate when lithium hydroxide is processed in greater amounts per hour (feed rate). On the other hand, the temperature setting of the heating furnace 14 may be 590oC or lower, 580oC or lower, or 570oC or lower.

[0034] The heating furnace 14 may, in its entirety, be configured as a single temperature-controllable area, or may be configured as a plurality of areas divided in the axial direction of the furnace core tube 12, in each of which the temperature can be independently controlled. The furnace usually has a single (one) or a plurality of 2 to 10 temperature-controllable areas. When a heating furnace in which the temperature can be controlled independently in a plurality of areas is used, the areas should be set to temperatures that are, on average, within the temperature setting ranges noted above, and the temperature is preferably set within the temperature setting ranges noted above in all areas.

[0035] The time for which the lithium hydroxide hydrate is heated (heating residence time) in the area of the heating section 12c of the furnace core tube 12 will depend on conditions such as the set temperature but is preferably 15 minutes or more, 20 minutes or more, 30 minutes or more, 40 minutes or more, 50 minutes or more, or 1 hour or more, for example. During the dehydration process using the rotary kiln, the material may not be dehydrated enough if the heating residence time is too short. Meanwhile, the heating residence time is preferably 10 hours or less, 9 hours or less, 8 hours or less, 7 hours or less, 6 hours or less, 5 hours or less, 4 hours or less, 3 hours or less, or 2 hours or less. The heating residence time refers to the value obtained by dividing the amount of lithium hydroxide, as calculated on an anhydride basis, in the heating section 12c divided by the discharge speed (kg / hr).

[0036] The rotary kiln 10 is provided with an exhaust pipe 36 for discharging the heated dry gas to the outside of the furnace core tube 12, and an exhaust step is carried out, as needed, to expel the heated drying gas via the exhaust pipe 36 to the outside of the furnace core tube 12. A heat-insulating material 32 is preferably provided on the outer peripheral surface in the area between the heating section 12c and the other end 12b of the furnace core tube 12. This will allow decreases in temperature inside the furnace core tube 12 to be prevented to prevent the resulting lithium hydroxide anhydride from absorbing moisture.

[0037] When lithium hydroxide hydrate has been dehydrated in the heating step and passes through the area in the heating section 12c of the furnace core tube 12, the dehydrated lithium hydroxide, specifically, the lithium hydroxide anhydride, is delivered to the other end 12b of the furnace core tube 12 and then discharged. The discharged lithium hydroxide anhydride is stored, via a discharge pipe 26, in a container 38 provided under the outlet hood 24. During the operation of the rotary kiln 10, 150oC to 300oC drying gas (the same drying gas as noted above can be used) is preferably supplied continuously or intermittently through a drying gas feed tube 40 connected to the discharge pipe 26 in order to prevent the resulting lithium hydroxide hydrate from absorbing moisture (becoming hydrated). As shown in the figure, a heat-insulating material 34 is preferably provided on the outer peripheral surface of the discharge pipe 26. This will allow the resulting lithium hydroxide anhydride to be prevented from absorbing moisture.

[0038] The residence time of the lithium hydroxide hydrate in the rotary kiln (the time until discharged through the exhaust pipe 26 after being supplied through the feeder 16) is preferably 20 minutes or more, 30 minutes or more, more than 30 minutes, 40 minutes or more, 50 minutes or more, or 1 hour or more, for example. During the dehydration process using the rotary kiln, the material may not be dehydrated enough if the heating residence time in the rotary kiln is too short. On the other hand, the residence time of the lithium hydroxide hydrate in the rotary kiln is preferably 10 hours or less, 9 hours or less, 8 hours or less, 7 hours or less, 6 hours or less, 5 hours or less, 4 hours or less, 3 hours or less, or 2 hours or less. The residence time refers to the value obtained by dividing the amount of lithium hydroxide, as calculated on an anhydride basis, in the rotary kiln divided by the discharge speed (kg / hr).

[0039] According to the present disclosure, 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section to warm up the furnace core tube itself, thereby making it possible to prevent condensation of the water vapor of water vapor-containing gas which can potentially flow back, and to prevent gas backflow itself. Thus, in cases involving the use of a large rotary kiln in which the lithium hydroxide hydrate feed rate is 100 kg / hr to 4000 kg / hr, the lithium hydroxide can be prevented from adhering to, or accumulating in, the furnace core tube, even when the lithium hydroxide hydrate is heated by a heating apparatus set to a temperature above 450oC. This allows an exceptionally efficient method for producing lithium hydroxide anhydride to be provided.Examples

[0040] The present disclosure is explained in greater detail using the following examples but is not limited to these examples.

[0041] Lithium hydroxide anhydride was produced using the rotary kiln 10 shown in Fig. 1. Specifically, lithium hydroxide hydrate powder (average particle size: 400 μm) was supplied in the amounts shown in Table 1 to the hopper 16a near the one end 12a inside the furnace core tube 12. Decarbonated gas having the temperatures shown in Table 1 was delivered through the drying gas feed tube 18 to the area between the one end 12a of the furnace core tube 12 and the heating section 12c. The decarbonated gas was delivered continuously, from start to finish, into the furnace core tube 12.

[0042] A heating furnace 14 having six independent temperature-controllable areas (zones 1 through 6 (arranged, in order, from the one end 12a of the furnace core tube)) was set to the temperatures shown in Table 1, and the lithium hydroxide hydrate that had been supplied was heated and dehydrated. The resulting lithium hydroxide anhydride was discharged from the other end 12b of the furnace core tube 12 and stored in a container 38. During the operation of the rotary kiln, 200oC decarbonated gas was continued to be supplied through a drying gas feed tube 40 connected to the discharge pipe 26 in order to prevent the resulting lithium hydroxide hydrate from absorbing moisture (becoming hydrated).

[0043] The axial length of the furnace core tube of the rotary kiln that was used was 16610 mm, the heating furnace width (length in the axial direction of the furnace core tube) was 12600 mm (the width of zones 1 through 6 was 2100 mm each), the inner diameter of the furnace core tube was 1400 mm, the furnace core tube volume was 25.569 m3, the furnace core tube incline was 1 / 100, the material of the furnace core tube was LCNi (low-carbon nickel: nickel content 99% by weight or more), and the furnace core tube thickness was 9 mm. The results are shown in Table 1 below.

[0044] The purity of LiOH was determined in the following manner. 2 g of the resulting lithium hydroxide hydrate was weighed out, and the total amount was transferred to a 100 mL volumetric flask. 20 mL of 6N HCl was then aliquoted and added to the volumetric flask. Pure water was furthermore added into the volumetric flask to bring the total volume to about 50 mL, the flask was capped, and the contents were mixed. The contents were allowed to stand for 60 minutes, were then brought to a volume of 100 mL using pure water, and were stirred. 10 mL was then aliquoted using a volumetric pipette and added to a 100 mL beaker, more pure water was added to adjust the total amount to 20 mL, 2 or 3 drops of methyl red indicator were then added, and the contents were stirred to obtain an adjusted liquid. 50 mL of 0.1N NaOH was prepared and was added dropwise at a rate of 20 mL / min into the adjusted liquid in the beaker, and the time at which the solution changed from red to bright yellow was considered to be the titration end point. The amount of 0.1N NaOH that had been added dropwise was recorded at that time.

[0045] The purity was calculated by the following procedure. (1) Calculation of amount of HCl material used to dissolve sample and amount of NaOH material at titration end point (2) Calculation of amount of HCl material n used to neutralize LiOH (difference between above amount of HCl material and amount of NaOH substance) (3) Calculation of amount of HCl material used to neutralize LiOH based on following chemical formula 　　LiOH + HCl → LiCl + H2O　 As the amount of HCl material n used to neutralize LiOH is equal to the amount of LiOH material, the purity is calculated using the following equation, where w is the weight of the LiOH being calculated. 　LiOH purity = w ÷ sample (2 g)

[0046]

[0047] 10: Rotary kiln 　12: Furnace core tube 　14: Heating furnace 　16: Feeder 　16a: Hopper 　16b: Feed tube 　18: Drying gas feed tube 　22: Inlet hood 　24: Outlet hood 　26: Discharge pipe 　30, 32, 34: Heat-insulating material 　36: Exhaust pipe 　38: Container

Claims

1. A method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln that has a furnace core tube, and a heating apparatus surrounding at least a portion of the furnace core tube in the axial direction, the method comprising: a supply step in which the lithium hydroxide hydrate is supplied to an area between: a heating section, which is a portion of the furnace core tube that is covered by the heating apparatus; and one end of the furnace core tube; a lithium hydroxide feed step in which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; a drying gas delivery step in which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and a heating step in which, during the lithium hydroxide feed step, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride.

2. The method for producing lithium hydroxide anhydride according to Claim 1, wherein the amount of the lithium hydroxide hydrate supplied is 2% by volume to 25% by volume based on the volume of the furnace core tube.

3. The method for producing lithium hydroxide anhydride according to Claim 1 or 2, wherein the lithium hydroxide hydrate is heated in the heating section of the furnace core tube for 15 minutes to 4 hours.

4. The method for producing lithium hydroxide anhydride according to Claim 1 or 2, wherein a heat-insulating material is provided on the outer peripheral surface in the area between the one end of the furnace core tube and the heating section.

5. The method for producing lithium hydroxide anhydride according to Claim 1 or 2, wherein the rotary kiln has an exhaust pipe for expelling the drying gas, that has been heated via the above heating, to the outside of the furnace core tube, and the method furthermore comprises an exhaust step in which the heated drying gas is expelled through the exhaust pipe to the outside of the furnace core tube.

6. The method for producing lithium hydroxide anhydride according to Claim 1 or 2, wherein the lithium hydroxide hydrate is fed at a rate of 100 kg / hr to 4000 kg / hr.

7. The method for producing lithium hydroxide anhydride according to Claim 1 or 2, wherein the residence time of the lithium hydroxide hydrate inside the rotary kiln is more than 30 minutes.

8. A rotary kiln that has: a furnace core tube; and a heating apparatus surrounding a predetermined range in the axial direction of the furnace core tube; and that is used to produce lithium hydroxide anhydride from lithium hydroxide hydrate, the rotary kiln comprising: supply means by which the lithium hydroxide hydrate is supplied to an area between: a heating section, which is a portion of the furnace core tube that is covered by the heating apparatus; and one end of the furnace core tube; lithium hydroxide feed means by which the lithium hydroxide hydrate that has been supplied is fed toward the other end of the furnace core tube; drying gas delivery means by which a 100oC or higher drying gas is delivered to the area between the one end of the furnace core tube and the heating section, when the lithium hydroxide hydrate has been supplied; and heating means by which, when the lithium hydroxide is fed toward the other end of the furnace core tube, the lithium hydroxide hydrate is heated and dehydrated by the heating apparatus, which has been set to >450oC to ≦600oC, to produce lithium hydroxide anhydride.

9. The rotary kiln according to Claim 8, wherein a heat-insulating material is provided on the outer peripheral surface in the area between the one end of the furnace core tube and the heating section.

10. The rotary kiln according to Claim 8 or 9, wherein an exhaust pipe is provided for expelling the heated drying gas to the outside of the furnace core tube in the heating section.

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