Method for producing anhydrous lithium hydroxide and rotary kiln

Abstract

To provide a method for producing high-purity anhydrous lithium hydroxide even when the processing rate of lithium hydroxide per hour is high. [Solution] The present disclosure is a method for producing anhydrous lithium hydroxide using a rotary kiln, comprising: a supply step of supplying lithium hydroxide hydrate to a region between a heating section, which is the part of the furnace core tube covered by a heating device, and one end of the furnace core tube; a lithium hydroxide feeding step of sending the supplied lithium hydroxide hydrate toward the other end of the furnace core tube; a dry gas supply step of sending a dry gas of 100°C or higher to the region between one end of the furnace core tube and the heating section while lithium hydroxide hydrate is being supplied; and a heating step of heating and dehydrating the lithium hydroxide hydrate with a heating device set to more than 450°C and less than or equal to 600°C between the lithium hydroxide feeding step to produce anhydrous lithium hydroxide.

Description

Technical Field

[0001] The present invention relates to a method for producing lithium hydroxide anhydride, and more particularly, to a method for producing lithium hydroxide anhydride from lithium hydroxide hydrate using a rotary kiln, and to a rotary kiln used in this method.

Background Art

[0002] Lithium hydroxide, which has been conventionally used as a raw material for positive electrode materials of lithium-ion batteries and the like, has high hygroscopicity and generally exists as lithium hydroxide hydrate (LiOH·nH₂O). When producing some product using lithium hydroxide as a raw material, it may be advantageous to use lithium hydroxide anhydride that does not generate water as a raw material rather than using lithium hydroxide hydrate that generates a large amount of water during the treatment process. In this case, as a pretreatment, a process of heating lithium hydroxide hydrate to dehydrate it is performed.

[0003] Patent Document 1 describes a method for dehydrating lithium hydroxide hydrate using a rotary kiln, which includes a supply step of supplying to a region between a heating portion, which is a portion covered by a heating device of a hearth tube of the rotary kiln, and one end of the hearth tube, a lithium hydroxide feeding step of feeding the supplied lithium hydroxide hydrate toward the other end side of the hearth tube, a drying gas sending step of sending a drying gas at 100°C or higher to a region between one end in the hearth tube and the heating portion when lithium hydroxide hydrate is being supplied, and a heating step of heating and dehydrating the lithium hydroxide hydrate by a heating device set at 230 to 450°C to produce lithium hydroxide anhydride during the lithium hydroxide feeding step. In this method, there is little adhesion of lithium hydroxide to the hearth tube, and high-purity lithium hydroxide anhydride can be obtained.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the example described in Patent Document 1, by performing the treatment with a supply rate of lithium hydroxide hydrate of 6.8 to 10.2 kg / hr, less lithium hydroxide adhesion to the reactor core tube and high-purity anhydrous lithium hydroxide are obtained. On the other hand, according to the inventors' findings, in the anhydrous treatment of lithium hydroxide using a rotary kiln as described in Patent Document 1, it has been found that the purity of lithium hydroxide tends to decrease when the processing amount exceeds several tens of kg / hr.

[0006] This disclosure has been made in view of the above circumstances, and aims to provide a method for producing lithium anhydrous lithium hydroxide from lithium hydroxide hydrate using a rotary kiln, which can produce high-purity lithium anhydrous lithium hydroxide even when the amount of lithium hydroxide processed per hour is large. [Means for solving the problem]

[0007] The present inventors have diligently conducted research to solve the above-mentioned problems. As a result, they have found that a method for producing lithium anhydride from lithium hydroxide hydrate using a rotary kiln having a furnace core tube and a heating device surrounding at least a portion of the furnace core tube in the axial direction, comprising a supply step of supplying lithium hydroxide hydrate to a region between the heating section, which is the portion of the furnace core tube covered by the heating device, and one end of the furnace core tube; a lithium hydroxide feeding step of sending the supplied lithium hydroxide hydrate toward the other end of the furnace core tube; a drying gas delivery step of sending a drying gas of 100°C or higher to the region between one end of the furnace core tube and the heating section while lithium hydroxide hydrate is being supplied; and a heating step of heating and dehydrating the lithium hydroxide hydrate with a heating device set to more than 450°C and less than or equal to 600°C between the lithium hydroxide feeding step to produce lithium anhydride, can produce high-purity lithium anhydride even when the amount of lithium hydroxide processed per hour is increased, and have completed the technology of this disclosure. Specifically, this disclosure provides the following:

[0008] (1) A method for producing lithium anhydrous lithium hydroxide from lithium hydroxide hydrate using a rotary kiln having a furnace core tube and a heating device surrounding at least a portion of the furnace core tube in the axial direction, A supply step of supplying the lithium hydroxide hydrate to the region between the heating section, which is the part of the furnace core tube covered by the heating device, and one end of the furnace core tube. A lithium hydroxide feeding process in which the supplied lithium hydroxide hydrate is sent toward the other end of the furnace core tube, A drying gas supply step in which, when the lithium hydroxide hydrate is supplied, a drying gas of 100°C or higher is supplied to the region between the one end of the furnace core tube and the heating section, and During the lithium hydroxide feeding process, a heating process is performed in which the lithium hydroxide hydrate is heated and dehydrated by the heating device set to a temperature between 450°C and 600°C to produce anhydrous lithium hydroxide. A method for producing anhydrous lithium hydroxide containing [the specified substance].

[0009] (2) The method for producing anhydrous lithium hydroxide according to (1), wherein the amount of lithium hydroxide hydrate supplied is 2% by volume or more and 25% by volume or less, based on the volume inside the furnace core tube.

[0010] (3) The method for producing anhydrous lithium hydroxide according to (1) or (2), wherein the time during which the lithium hydroxide hydrate is heated in the heating section of the furnace core tube is 15 minutes or more and 4 hours or less.

[0011] (4) A method for producing anhydrous lithium hydroxide according to (1) or (2), wherein an insulating material is provided on the outer surface of the region between the one end of the furnace core tube and the heating section.

[0012] (5) The rotary kiln has an exhaust pipe for discharging the dry gas heated by the heating to the outside of the furnace tube, A method for producing anhydrous lithium hydroxide according to (1) or (2), further comprising an exhaust step of discharging the heated dry gas to the outside of the furnace tube via the exhaust pipe.

[0013] (6) A method for producing anhydrous lithium hydroxide according to (1) or (2), wherein the supply rate of the lithium hydroxide hydrate is 100 kg / hr or more and 4000 kg / hr or less.

[0014] (7) The method for producing anhydrous lithium hydroxide according to (1) or (2), wherein the residence time of the lithium hydroxide hydrate in the rotary kiln is more than 30 minutes.

[0015] (8) A rotary kiln having a furnace core tube and a heating device surrounding a predetermined range in the axial direction of the furnace core tube, used for producing lithium anhydrous lithium hydroxide from lithium hydroxide hydrate, A supply means for supplying the lithium hydroxide hydrate to the region between the heating section, which is the portion of the furnace core tube covered by the heating device, and one end of the furnace core tube. A lithium hydroxide feeding means for sending the supplied lithium hydroxide hydrate toward the other end of the furnace core tube, When the lithium hydroxide hydrate is supplied, drying gas delivery means for delivering a drying gas at 100°C or higher to a region between the one end in the core tube and the heating part, and heating means for heating and dehydrating the lithium hydroxide hydrate by the heating device set at over 450°C and 600°C or lower to produce anhydrous lithium hydroxide while sending the lithium hydroxide toward the other end side of the core tube A rotary kiln having the above.

[0016] (9) The rotary kiln according to (8), wherein a heat insulating material is provided on an outer peripheral surface of a region between the one end in the core tube and the heating part.

[0017] (10) The rotary kiln according to (8) or (9), wherein an exhaust pipe for discharging the dried gas heated in the heating part to the outside of the core tube is provided.

Advantages of the Invention

[0018] According to the present disclosure, there is provided a method capable of producing high-purity anhydrous lithium hydroxide even when the throughput of lithium hydroxide per unit time is large in a method for producing anhydrous lithium hydroxide from lithium hydroxide hydrate using a rotary kiln.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic cross-sectional view showing an example of a rotary kiln that can be used in the method for producing anhydrous lithium hydroxide according to an embodiment of the present disclosure. It is a schematic cross-sectional view showing an example of a rotary kiln that can be used in the method for producing anhydrous lithium hydroxide according to an embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present disclosure will be described. However, the present disclosure is not limited to the description of the embodiments and can be implemented with appropriate modifications.

[0021] A method for producing anhydrous lithium hydroxide according to an embodiment of the present disclosure is a method for producing anhydrous lithium hydroxide from lithium hydroxide hydrate using a rotary kiln having a furnace core tube and a heating device surrounding at least a portion of the furnace core tube in the axial direction, and includes a supply step of supplying lithium hydroxide hydrate to a region between a heating section, which is the portion of the furnace core tube covered by the heating device, and one end of the furnace core tube; a lithium hydroxide feeding step of sending the supplied lithium hydroxide hydrate toward the other end of the furnace core tube; a drying gas delivery step of sending a drying gas of 100°C or higher to the region between one end of the furnace core tube and the heating section while lithium hydroxide hydrate is being supplied; and a heating step of heating and dehydrating the lithium hydroxide hydrate with a heating device set to more than 450°C and less than or equal to 600°C between the lithium hydroxide feeding step to produce anhydrous lithium hydroxide.

[0022] Hereinafter, with reference to the drawings, a method for producing anhydrous lithium hydroxide according to the embodiments of this disclosure will be described in detail, along with the configuration of a rotary kiln that can be used in such a production method.

[0023] Specifically, a rotary kiln that can be used in a method for producing anhydrous lithium hydroxide according to the embodiment of this disclosure has a furnace core tube and a heating device that surrounds a predetermined range in the axial direction of the furnace core tube, and is a rotary kiln used for producing anhydrous lithium hydroxide from lithium hydroxide hydrate. This rotary kiln has a supply means for supplying lithium hydroxide hydrate to a region between a heating section, which is the part of the furnace core tube covered by the heating device, and one end of the furnace core tube; a lithium hydroxide feeding means for sending the supplied lithium hydroxide hydrate toward the other end of the furnace core tube; a drying gas supply means for sending a drying gas of 100°C or higher to the region between one end of the furnace core tube and the heating section when lithium hydroxide hydrate is being supplied; and a heating means for heating and dehydrating the lithium hydroxide hydrate with a heating device set to more than 450°C and less than or equal to 600°C while the lithium hydroxide is being sent toward the other end of the furnace core tube, thereby producing anhydrous lithium hydroxide.

[0024] Figure 1 is a schematic cross-sectional view showing an example of a rotary kiln that can be used in a method for producing anhydrous lithium hydroxide according to the embodiments of this disclosure. As shown in the figure, the rotary kiln 10 has, as a basic configuration, a furnace core tube 12 and a heating device 14 that surrounds a predetermined axial range of the furnace core tube 12. An inlet hood 22 is installed on one end 12a of the furnace core tube 12, and an outlet hood 24 is installed on the other end 12b.

[0025] A feeder 16 is connected to one end 12a of the furnace core tube 12, and the feeder 16 has a hopper 16a and a feed pipe 16b. Lithium hydroxide hydrate supplied to the hopper 16a is supplied via the feed pipe 16b to the region between the heating section 12c and one end 12a of the furnace core tube 12 (feeding process). A screw (not shown) for feeding lithium hydroxide hydrate into the furnace core tube 12 is appropriately installed in the feed pipe 16b.

[0026] The inner diameter of the reactor core tube 12 is not particularly limited, but is preferably, for example, greater than 300 mm, 400 mm or more, 500 mm or more, 600 mm or more, 700 mm or more, 800 mm or more, or 900 mm or more. On the other hand, the inner diameter of the reactor 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.

[0027] When supplying lithium hydroxide hydrate from the supply unit 16 into the furnace core tube 12, a dry gas (nitrogen, decarbonated gas (carbon dioxide content of 0.1 ppm to 100 ppm, preferably 1 ppm or less)), argon, etc.) is introduced along with the lithium hydroxide hydrate via the supply pipe 16b as needed.

[0028] The supply amount (filling rate) of lithium hydroxide hydrate is not particularly limited, but it is preferably 2% or more by volume, 3% or more by volume, 4% or more by volume, or 5% or more by volume, based on the volume of the furnace core tube 12. On the other hand, the supply amount (filling rate) of lithium hydroxide hydrate is preferably 25% or less by volume, 20% or less by volume, 17% or less by volume, 15% or less by volume, or 12% or less by volume. Within this range, stagnation and backflow can be further prevented within the furnace core tube 12, and the dehydration treatment of lithium hydroxide hydrate can be performed.

[0029] The supply rate of lithium hydroxide hydrate 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 supply rate of lithium hydroxide hydrate is preferably 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. With such a supply rate, when lithium hydroxide hydrate is dehydrated under the conditions of this disclosure, it is easier to obtain anhydrous lithium hydroxide of high purity while preventing lithium hydroxide from solidifying and accumulating inside the furnace core tube.

[0030] Lithium hydroxide hydrate is supplied as a powder. Its average particle size is not particularly limited, but may be, for example, 10 μm or more and 1000 μm or less.

[0031] The reactor core tube 12 is configured to rotate around an axis that passes through the center of the reactor's cross-section and extends in the height direction of the reactor core tube 12, and is installed at an incline such that the other end 12b (outlet side) is lower than the one end 12a (inlet side). As a result, lithium hydroxide hydrate is sent from the one end 12a to the other end 12b inside the reactor core tube 12 (lithium hydroxide feeding process).

[0032] The inclination of the reactor core tube 12 at this time (inclination with respect to the horizontal plane) is not particularly limited and can be set according to conditions such as heating time, but for example it may be 0.1 / 100 or more, 0.2 / 100 or more, or 0.3 / 100 or more. On the other hand, the inclination of the reactor core tube 12 may be 3 / 100 or less, 2 / 100 or less, or 1 / 100 or less.

[0033] The rotation speed of the furnace core tube 12 can be set according to conditions such as heating time, but it is preferably between 0.1 rpm and 30 rpm.

[0034] The material used for the furnace core tube 12 is preferably one that has excellent heat resistance and thermal conductivity and is inert to lithium hydroxide. Specifically, nickel, stainless steel, ceramics, etc. are preferred materials for the furnace core tube 12, with nickel being more preferred among them.

[0035] The size of the furnace core tube 12 can be determined according to the processing volume of lithium hydroxide hydrate. The thickness of the furnace core tube 12 may be, for example, 4 mm or more and 12 mm or less. A feed vane or knocker may be placed on one end 12a of the furnace core tube 12 from the heating section 12c to ensure that the lithium hydroxide hydrate is smoothly fed.

[0036] The rotary kiln 10 is provided with a drying gas supply pipe 18 for supplying drying gas into the furnace core tube 12. The drying gas supply pipe 18 is installed so that its outlet 18a is located in the region between one end 12a of the furnace core tube 12 and the heating section 12c. When lithium hydroxide hydrate is supplied into the furnace core tube 12, the drying gas is supplied through the drying gas supply pipe 18 to the region inside the furnace core tube 12 between one end 12a of the furnace core tube and the heating section 12c (drying gas supply process). The drying gas can be supplied continuously or intermittently, but it is preferable to supply it continuously.

[0037] Furthermore, the outlet 18a of the drying gas supply pipe 18 is preferably located at or near the supply point of lithium hydroxide hydrate within the furnace core pipe 12. This ensures that lithium hydroxide does not solidify or accumulate.

[0038] The drying gas used is not particularly limited, but it is preferable to use one that is inert to lithium hydroxide, and it is preferable to use a decarbonated gas (a gas with a carbon dioxide content of typically 0.1 ppm to 100 ppm, preferably 1 ppm or less), such as nitrogen or argon.

[0039] The temperature of the dry gas supplied through the dry gas supply pipe 18 is not particularly limited as long as it is 100°C or higher, but it is preferably 120°C or higher, 150°C or higher, or 170°C or higher. Furthermore, the temperature of the dry gas supplied through the dry gas supply pipe 18 is preferably 460°C or lower, 400°C or lower, 350°C or lower, or 300°C or lower. By maintaining the above temperatures, it is possible to prevent lithium hydroxide from solidifying inside the furnace core tube 12.

[0040] The amount of dry gas supplied is not particularly limited, but for example, 10 m³ 3 / hr or more 3000m 3 / hr or less, 50m 3 / hr or more 2500m 3 / hr or less, 80m 3 / hr more than 2000m 3 It is preferable that it be less than or equal to / hr.

[0041] It is preferable to provide an insulating material 30 on the outer surface of the furnace core tube 12, including the area where the dry gas is discharged (the region between one end 12a of the furnace core tube 12 and the heating section 12c). This prevents a drop in temperature of the furnace core tube 12 and its interior, which are heated by the dry gas.

[0042] The material of the insulation is not particularly limited, but for example, polyurethane foam, glass wool, ceramic fiberboard, etc. can be used.

[0043] At least a portion of the entire axial length of the furnace core tube 12 is surrounded by a heating device 14. The width of the heating device 14 is shorter than the axial length of the furnace core tube 12, and the heating device 14 is positioned in the central part of the furnace core tube 12, spaced apart from one end 12a and the other end 12b. The lithium hydroxide hydrate supplied into the furnace core tube 12 is heated by the heating device 14 during the process of being sent from one end 12a to the other end 12b (heating process).

[0044] The set temperature of the heating furnace 14 is not particularly limited as long as it is between 450°C and 600°C, but it is preferably 460°C or higher, 470°C or higher, 480°C or higher, 490°C or higher, or 500°C or higher. If the temperature is lower than this, it may not be possible to sufficiently dehydrate the lithium hydroxide hydrate when the processing rate (supply rate) of lithium hydroxide per hour is high. On the other hand, the set temperature of the heating furnace 14 may be 590°C or lower, 580°C or lower, or 570°C or lower.

[0045] The heating furnace 14 may be configured as a single temperature-controllable region, or it may be configured as multiple regions divided along the axial direction of the furnace core tube 12, each with independently controllable temperatures. Typically, it has one temperature-controllable region, or two to ten regions. When using a heating furnace with multiple regions, each with independently controllable temperatures, it is sufficient that the average temperature of each region is within the above-mentioned set temperature range, and preferably all regions are within the above-mentioned set temperature range.

[0046] The heating time (heating residence time) for lithium hydroxide hydrate in the heating section 12c region of the furnace core tube 12 depends on various 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. In dewatering treatment using a rotary kiln, if the heating residence time is too short, dewatering may not be sufficient. On the other hand, 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. Note that the heating residence time is the value obtained by dividing the amount of lithium hydroxide in the heating section 12c in terms of anhydrous form (kg) by the discharge rate (kg / hr).

[0047] The rotary kiln 10 is provided with an exhaust pipe 36 for discharging the heated dry gas to the outside of the furnace tube 12, and an exhaust process is performed as needed to discharge the heated dry gas to the outside of the furnace tube 12 via the exhaust pipe 36. It is preferable to provide an insulating material 32 on the outer surface of the region between the heated section 12c and the other end 12b of the furnace tube 12, as shown in the figure. This prevents a drop in temperature inside the furnace tube 12 and prevents the generated anhydrous lithium hydroxide from absorbing moisture.

[0048] During the heating process, the lithium hydroxide hydrate is dehydrated, and after passing the heated area 12c of the furnace core tube 12, the dehydrated lithium hydroxide, i.e., anhydrous lithium hydroxide, is sent to the other end 12b of the furnace core tube 12 and then discharged. The discharged anhydrous lithium hydroxide is collected in a container 38 located below the outlet hood 24 via the discharge pipe 26. While the rotary kiln 10 is in operation, it is preferable to continuously or intermittently supply a dry gas (the same dry gas as described above can be used) with a temperature of 150°C to 300°C (the same dry gas as described above can be used) via a dry gas supply pipe 40 connected to the discharge pipe 26 in order to prevent the produced lithium hydroxide hydrate from absorbing moisture (forming a hydrate). It is preferable to provide an insulating material 34 on the outer surface of the discharge pipe 26 as shown in the figure. This prevents the generated anhydrous lithium hydroxide from absorbing moisture.

[0049] The residence time of lithium hydroxide hydrate in the rotary kiln (the time from when it is supplied from the feeder 16 until it is discharged from the discharge pipe 26) is preferably, for example, 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. In dewatering treatment using a rotary kiln, if the residence time in the rotary kiln is too short, dewatering may not be sufficient. On the other hand, the residence time of 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 in the rotary kiln in anhydrous form (kg) by the discharge rate (kg / hr).

[0050] According to this disclosure, by sending a dry gas at 100°C or higher from one end of the furnace tube to the region between it and the heating section to warm the furnace tube itself, it is possible to prevent the condensation of water vapor in the gas containing water vapor that could flow back, and also to suppress the backflow of the gas itself. As a result, when using a large rotary kiln with a supply rate of lithium hydroxide hydrate of 100 kg / hr or more and 4000 kg / hr or less, even if the lithium hydroxide hydrate is heated by a heating device set to a high temperature of over 450°C, it is possible to prevent the lithium hydroxide from solidifying and accumulating inside the furnace tube. This makes it possible to provide a method for producing anhydrous lithium hydroxide with excellent production efficiency. [Examples]

[0051] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0052] Anhydrous lithium hydroxide was produced using the rotary kiln 10 shown in Figure 1. Specifically, lithium hydroxide hydrate powder (average particle size: 400 μm) was supplied to the hopper 16a near one end 12a of the furnace core tube 12 at the supply rate shown in Table 1. Decarbonated gas at the temperature shown in Table 1 was supplied from the drying gas supply pipe 18 to the region between one end 12a of the furnace core tube 12 and the heating section 12c. The supply of decarbonated gas was carried out continuously from the start to the end of the supply of lithium hydroxide hydrate into the furnace core tube 12.

[0053] Furthermore, the heating furnace 14, which has six independent temperature-controllable zones (zones 1 to 6, arranged in order from one end 12a of the furnace tube), was set to the temperatures shown in Table 1, and the supplied lithium hydroxide hydrate was heated and dehydrated. The anhydrous lithium hydroxide produced in this way was discharged from the other end 12b of the furnace tube 12 and collected in the container 38. During the operation of the rotary kiln, in order to prevent moisture absorption (hydration) of the produced anhydrous lithium hydroxide, a 200°C decarbonated gas was continuously supplied via a drying gas supply pipe 40 connected to the discharge pipe 26.

[0054] The rotary kiln used had an axial length of 16,610 mm for the core tube, a furnace width (length in the axial direction of the core tube) of 12,600 mm (with zones 1-6 each having a width of 2,100 mm), an inner diameter of 1,400 mm, and a core tube volume of 25.569 m³. 3 The furnace core tube had a tilt of 1 / 100, was made of LCNi (low-carbon nickel: nickel content of 99% by mass or more), and had a thickness of 9 mm. The results are shown in Table 1 below.

[0055] The purity of LiOH was measured as follows: 2 g of the prepared lithium hydroxide hydrate was weighed and transferred to a 100 mL volumetric flask. Next, 20 mL of 6N HCl was taken and added to the volumetric flask. Then, pure water was added until the volumetric flask was approximately 50 mL, the flask was capped, and mixed. After standing for 60 minutes, the volume was made up to 100 mL with pure water and stirred. Then, 10 mL was taken using a volumetric pipette and added to a 100 mL beaker. Pure water was added to adjust the total volume to 20 mL, and then 2-3 drops of methyl red indicator were added and stirred to obtain the adjusted solution. 50 mL of 0.1 N NaOH was prepared and added dropwise to the adjusted solution in the beaker at a rate of 20 mL / min. The titration endpoint was defined as the moment when the solution changed color from red to golden yellow. At this time, the amount of 0.1 N NaOH added was recorded.

[0056] The purity was calculated using the following procedure. (1) Calculate the amount of HCl used to dissolve the sample and the amount of NaOH used at the titration endpoint. (2) Calculate the amount of HCl n after neutralizing LiOH, which is the difference between the amount of HCl and the amount of NaOH mentioned above. (3) Calculate the amount of substance of HCl obtained by neutralizing LiOH from the following chemical formula. LiOH + HCl → LiCl + H2O Since the amount of HCl n obtained by neutralizing LiOH is equivalent to the amount of LiOH, if we let w be the mass of LiOH obtained, the purity can be calculated using the following formula. LiOH purity = w ÷ sample (2g)

[0057] [Table 1] [Explanation of symbols]

[0058] 10 Rotary Kiln 12 Furnace tube 14 Furnace 16 Feeding machine 16a Hopper 16b Supply pipe 18 Drying gas supply pipe 22 Entrance Hood 24 Exit Hood 26 Discharge pipe 30, 32, 34 Insulation 36 Exhaust pipe 38 Container

Claims

1. A method for producing lithium anhydrous lithium hydroxide from lithium hydroxide hydrate, using a rotary kiln having a furnace core tube and a heating device surrounding at least a portion of the furnace core tube in the axial direction, A supply step of supplying the lithium hydroxide hydrate to the region between the heating section, which is the part of the furnace core tube covered by the heating device, and one end of the furnace core tube. A lithium hydroxide feeding process in which the supplied lithium hydroxide hydrate is sent toward the other end of the furnace core tube, A drying gas supply step in which, when the lithium hydroxide hydrate is supplied, a drying gas of 100°C or higher is supplied to the region between the one end of the furnace core tube and the heating section, and During the lithium hydroxide feeding process, a heating process is performed in which the lithium hydroxide hydrate is heated and dehydrated by the heating device set to a temperature between 450°C and 600°C to produce anhydrous lithium hydroxide. A method for producing anhydrous lithium hydroxide containing [the specified substance].

2. The amount of lithium hydroxide hydrate supplied is 2% by volume or more and 25% by volume or less, based on the volume inside the furnace core tube. A method for producing anhydrous lithium hydroxide according to claim 1.

3. The time during which the lithium hydroxide hydrate is heated in the heating section of the furnace core tube is 15 minutes or more and 4 hours or less. A method for producing anhydrous lithium hydroxide according to claim 1 or 2.

4. An insulating material is provided on the outer surface of the region between one end of the furnace core tube and the heating section. A method for producing anhydrous lithium hydroxide according to claim 1 or 2.

5. The rotary kiln has an exhaust pipe for discharging the dry gas heated by the heating process to the outside of the furnace tube. The system further includes an exhaust step of discharging the heated dry gas to the outside of the core tube via the exhaust pipe. A method for producing anhydrous lithium hydroxide according to claim 1 or 2.

6. The supply rate of the lithium hydroxide hydrate is 100 kg / hr or more and 4000 kg / hr or less. A method for producing anhydrous lithium hydroxide according to claim 1 or 2.

7. The residence time of the lithium hydroxide hydrate in the rotary kiln is more than 30 minutes. A method for producing anhydrous lithium hydroxide according to claim 1 or 2.

8. A rotary kiln having a furnace core tube and a heating device surrounding a predetermined axial range of the furnace core tube, used for producing lithium anhydrous lithium hydroxide from lithium hydroxide hydrate, A supply means for supplying the lithium hydroxide hydrate to the region between the heating section, which is the portion of the furnace core tube covered by the heating device, and one end of the furnace core tube. A lithium hydroxide feeding means for sending the supplied lithium hydroxide hydrate toward the other end of the furnace core tube, A drying gas supply means for supplying a drying gas at 100°C or higher to the region between the one end of the furnace core tube and the heating section when the lithium hydroxide hydrate is being supplied, and While the lithium hydroxide is being sent toward the other end of the furnace core tube, the heating means heats and dehydrates the lithium hydroxide hydrate using the heating device set to a temperature between 450°C and 600°C to produce anhydrous lithium hydroxide. Rotary kiln.

9. An insulating material is provided on the outer surface of the region between one end of the furnace core tube and the heating section. The rotary kiln according to claim 8.

10. An exhaust pipe is provided for discharging the heated dry gas from the heating section to the outside of the furnace tube. The rotary kiln according to claim 8 or 9.

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