Method for recovering lithium or method for recovering metal from neutralization residue

Abstract

To provide a method for recovering lithium capable of recovering lithium with high purity from a treatment liquid in which lithium and an inorganic salt are dissolved, and a method for recovering metal from neutralization residue produced in a filtration step involving solid-liquid separation from the neutralization residue.SOLUTION: A method for recovering lithium includes a carbonation step S9, in which carbon dioxide gas is mixed into and / or a water-soluble carbonate is added to a treatment liquid in which lithium and an inorganic salt are at least dissolved, and a simultaneous dropwise addition step S10, in which hydrofluoric acid is added to precipitate lithium fluoride crystals, and a drying step S11, which involves washing the precipitate containing the lithium fluoride crystals and performing solid-liquid separation from the treatment liquid by filtration. The drying step involves setting the steam pressure to 0.26 MPa or higher, the jet outlet flow velocity to 200 to 650 m / s, the hot air pressure to 5 to 20 kPa, and the hot air temperature to 250°C to 600°C, in order to have a final product adjusted to have optimal moisture content, particle size, specific surface area, bulk density, hygroscopicity, and porosity.

Description

[Technical field]

[0001] The present invention relates to a lithium recovery method for recovering lithium from a treatment liquid in which at least lithium is dissolved, or a metal recovery method from a neutralization residue, and in particular to a lithium recovery method used when recovering lithium from waste lithium ion secondary batteries of EVs, etc. [Background technology]

[0002] In recent years, with the accelerated shift to electric vehicles, there has been an increasing need to recover lithium from used lithium-ion secondary batteries in light of legal regulations, including the recycling of specific important substances such as lithium. The positive electrodes of these lithium-ion secondary batteries use lithium transition metal oxides, such as lithium cobalt oxide and lithium nickel oxide, as the positive electrode active material, and valuable metals such as cobalt and nickel are recovered from waste lithium-ion secondary batteries.

[0003] Meanwhile, methods for recovering lithium from waste lithium-ion secondary batteries have conventionally been limited to recovery from crushed powder of lithium-ion secondary batteries that have been roasted. However, in recent years, the raw material price of lithium has soared, and the demand for lithium-ion secondary batteries is increasing. In addition, waste is expected to increase in the future. Therefore, efficient recovery of lithium is extremely beneficial from the perspective of effective use of resources and achieving a sustainable society. As a method for efficiently recovering lithium, a recovery method has been proposed in which lithium carbonate is reacted with a dropwise addition of hydrofluoric acid solution to precipitate lithium fluoride crystals, which are then washed, filtered, and dried.

[0004] For example, when solid content is dried by a conventional method after solid-liquid separation by filtration, it is difficult to obtain high-purity lithium carbonate having a large primary particle size and a regular shape, and there is a problem that the recovered lithium carbonate cannot be used as it is as a raw material for the positive electrode material of lithium-ion secondary batteries (see Patent Document 1). In addition, in an example in which the solid content was dried by a conventional method after solid-liquid separation, the average particle size was 12.2 μm and the specific surface area was 1.3 m. 2 / g, and there is room for improvement in terms of the particle surface that comes into contact with the electrolyte (see Example 1 in Patent Document 2). In addition, by making the dried product after solid-liquid separation porous, the reaction formula LiF (solid) + HF (gas) → LiHF 2 It was found that the synthesis reaction proceeded smoothly according to the solid state, but no solution for making the material porous was shown (Patent Document 3). After drying, the moisture and oxygen in the lithium fluoride react with phosphorus pentafluoride, and the product is phosphorus oxyfluoride (POF 3 These substances may decompose into hydrogen fluoride (HF) and hydrogen fluoride (HF) and become mixed into the electrolyte of the lithium-ion secondary battery. These are undesirable because they inhibit the battery reaction. Furthermore, if these substances are incorporated into the battery, the battery may expand, causing serious problems (Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 62-252315 [Patent Document 2] Patent Publication No. 2022-095988 [Patent Document 3] Japanese Patent Application Publication No. 01-072901 [Patent Document 4] JP 2008-156190 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to Patent Document 1, Li 2 CO 3 +CO 2 +H 2 O→2LiHCO 3The lithium hydrogen carbonate aqueous solution obtained by the carbonation step performed by the above-mentioned procedure is subjected to precision filtration to remove insoluble matters, and then the filtrate is heated to precipitate lithium carbonate by a gradual decomposition reaction of lithium hydrogen carbonate. The filtrate is then subjected to solid-liquid separation by a conventional method, and the solid matter is dried to obtain high-purity lithium carbonate having a large primary particle size and a regular shape. The average particle size is desirably 10 to 100 μm, preferably 30 to 80 μm. If the average particle size is less than 10 μm, the content of impurities increases and the particles tend to become cohesive, whereas if the average particle size exceeds 100 μm, it is difficult to obtain particles having a uniform columnar shape.

[0007] According to Patent Document 2, in the present embodiment, after washing with an aqueous lithium carbonate solution, the slurry containing the powder is filtered, and the obtained powder is dried, the following problems are described with respect to the drying temperature, moisture content, average particle size, and specific surface area (paragraphs 0026-0027, 0042-0043). [Drying temperature] If the temperature is less than 80° C., the drying of the powder after washing will be slow, resulting in a gradient of lithium concentration between the powder surface and the interior of the powder, which may degrade the battery characteristics of the resulting positive electrode active material. On the other hand, if the temperature exceeds 350°C, the crystal structure near the powder surface may collapse, and the battery characteristics of the resulting positive electrode active material may deteriorate. This is thought to be because the crystal structure near the surface of the powder after washing is very close to the stoichiometric ratio, or is in a state close to the charged state with some lithium desorbed, making it prone to collapse. Furthermore, if the powder is dried in an atmosphere containing carbon and sulfur compounds or in a vacuum, the carbon and sulfur contents in the powder will change, and the desired effect will not be obtained. [Moisture percentage] It is preferable to dry the powder so that the moisture content after drying is 0.2% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less. [Average particle size] The average particle size of the positive electrode active material of the present embodiment is not particularly limited, but for example, by making it 3 μm or more and 25 μm or less, it is possible to increase the battery capacity per volume of the positive electrode active material, and to obtain a secondary battery that is highly safe and has good cycle characteristics. [Specific surface area] The specific surface area of ​​the positive electrode active material of this embodiment is not particularly limited, but is, for example, 1.0 m 2 / g or more 7.0m 2 / g or less, and there is sufficient particle surface area that can come into contact with the electrolyte. 2 If the specific surface area is less than 7.0 m / g, the particle surface area that can come into contact with the electrolyte is reduced, and sufficient charge / discharge capacity may not be obtained. 2 If it exceeds 1 / g, the particle surface area in contact with the electrolyte may become too large, resulting in reduced safety.

[0008] According to Patent Document 3, as a result of extensive investigations into a method for producing a lithium fluoride complex salt, in which lithium fluoride is reacted with a fluoride gas in a process called a solid-gas reaction, it was discovered that the reaction formula LiF (solid) + HF (gas) → LiHF can be achieved by desorbing hydrofluoric acid from acidic lithium fluoride and making the lithium fluoride porous. 2 It is described that the synthesis reaction proceeds smoothly according to (solid), and that a high-purity lithium fluoride complex salt that does not contain impurities such as moisture can be rapidly produced, but no method for making it porous is shown.

[0009] According to Patent Document 4, in a general method for producing lithium fluoride by directly reacting lithium carbonate with hydrofluoric acid, since the solubility of lithium carbonate and lithium fluoride in water and dilute hydrofluoric acid is extremely low, very fine particles are precipitated simultaneously with the reaction, and further, since the reaction is very fast and intense, particles that are obtained are aggregated to about 10 μm, and the following problems are described regarding the oxygen component, moisture, bulk density, hygroscopicity, and angle of repose (paragraphs 0005, 0006, 0007, 0015, 0018, and 0040). [Oxygen component] When the above-mentioned aggregation occurs, unreacted lithium carbonate is taken into the particles, and no matter how high the temperature and / or vacuum is used for drying, the oxygen component derived from the unreacted lithium carbonate cannot be reduced. When used as an electrolyte for lithium-ion secondary batteries, the water and oxygen components in the raw material react with phosphorus pentafluoride, and the product is phosphorus oxyfluoride (POF 3 These substances can decompose into hydrogen fluoride (HF) and hydrogen fluoride (HF) and become mixed into the product. These are undesirable because they inhibit the battery reaction. Furthermore, if these substances are incorporated into the battery, the battery may expand, causing serious problems. [moisture] The document states that lithium fluoride separated from the synthesis system in an aqueous solution has a very high water content, and it is extremely difficult to reduce the water content to 1000 ppm by weight or less using conventional drying methods, and that some ingenuity, such as increasing the drying temperature, is necessary. [Bulk density] Bulk density is 0.75g / cm 3 It is described that it is necessary to suppress hygroscopicity by obtaining the above lithium fluoride. [Hygroscopicity] Lithium fluoride is in powder form with a large specific surface area and is highly hygroscopic, so there was an issue that even after drying, it would easily absorb moisture from the air during storage. [Angle of repose] The angle of repose is an important factor when designing hoppers and silos for powders. Powders with a large angle of repose have poor fluidity and are prone to bridging in the hopper. In other words, unless the inclination of the bottom of the hopper or silo is made larger than the angle of repose of the powder inside, the powder inside cannot be discharged completely.

[0010] The present invention has been made to solve the above-mentioned problems, and provides a lithium recovery method capable of recovering high-quality lithium as a raw material for secondary batteries by precipitating lithium fluoride crystals from a treatment liquid containing dissolved lithium and inorganic salts, washing and filtering the crystals, and then performing steam jet injection drying having a structure for injecting superheated steam. [Means for solving the problem]

[0011] The lithium recovery method of the present invention is characterized by comprising a carbonation step of mixing carbon dioxide gas and / or adding a water-soluble carbonate to a liquid to be treated in which at least lithium and an inorganic salt are dissolved, a step of separating and filtering a precipitate containing lithium carbonate crystals precipitated by the carbonation step from the liquid to be treated, and a steam jet injection type drying device having a structure for injecting superheated steam, which can efficiently dry the treated material by both kinetic energy for disintegrating and pulverizing the treated material by supersonic shock waves and thermal energy for heat exchange while swirling with a high-temperature air flow, and provides an optimal oxygen component, drying temperature, moisture, particle size, specific surface area, bulk density, hygroscopicity, and drying method for making the material porous.

[0012] The present invention also provides a method for recovering metals from lithium neutralization residue, which comprises a leaching step of leaching battery slag obtained by roasting lithium ion secondary battery waste into an acidic solution, and a neutralization step of increasing the pH of the leaching solution obtained in the leaching step to neutralize the solution and obtain a lithium dissolving solution and a neutralization residue, in which the precipitate formed in the pH adjustment step is separated into solid and liquid by filtration and efficiently dried by a steam jet injection type drying device.

[0013] In order to solve the above-mentioned problems, the means adopted in the present invention are a steam flow adjusting unit to which high-temperature, high-pressure steam is supplied and which adjusts the steam flow, a steam injection nozzle attached downstream of the steam flow adjusting unit and which injects steam, a high-temperature gas supply unit which supplies high-temperature gas, and a steam jet drying apparatus attached to the steam injection nozzle and which mixes the steam injected from the steam injection nozzle with the high-temperature gas supplied from the high-temperature gas supply unit to inject a mixed gas.

[0014] The present invention employs a steam jet drying apparatus having a diffuser structure for injecting a mixed gas obtained by mixing steam injected from a steam injection nozzle with high-temperature gas supplied from a high-temperature gas supply section, in which the steam injected from the steam injection nozzle is superheated steam heated to 150 to 450°C.

[0015] In addition, in the conventional method (Patent Application No. 10-29358), the negative pressure of the steam jet was used to take in high-temperature air, so the energy of the ejector was consumed both in drawing in the high-temperature air and in resisting the blowing of the air into the drying chamber. As a result, only an amount of high-temperature air equivalent to the amount of steam from the steam injection nozzle could be drawn in at the diffuser outlet, resulting in a low throughput and a high dew point temperature for the mixed air. The solution provided by the present invention is to supply high-temperature air so as to achieve a positive pressure of 0 kPa or more and 20 kPa or less near the air intake port of the ejector, thereby increasing the amount of high-temperature air supplied and relatively decreasing the steam weight ratio of the mixed gas of the steam amount and the high-temperature air amount mixed in the ejector. As a result, the humidity of the exhaust gas after crushing and drying the processed material is significantly reduced, and the amount of heat exchanged by the amount of high-temperature air blown in is dramatically increased, making it possible to significantly increase the processing volume.

[0016] By supplying heated superheated steam to the treatment tank and adjusting the mixing ratio of the superheated steam and high-temperature gas, a mixed gas with a low oxygen concentration can be supplied to the treatment tank, and the oxygen concentration can be significantly reduced to below 1%. As a method for further reducing the oxygen concentration and creating an oxygen-free state, for example, flammable gases such as hydrogen, methane gas, and organic solvents blown into the inside can be burned on a platinum catalyst. In addition, high-temperature gas can be deliberately mixed with inert gas using, for example, a high-speed burner with a low excess air ratio, and hydrogen is then supplied to it and burned. By simultaneously heating the gas and deoxygenating it, the oxygen concentration can be easily reduced to nearly 0%, which has the excellent effect of safely treating materials that should not be oxidized.

[0017] The drying chamber may further include a drying tank into which a fixed amount of material is supplied and which crushes and swirls the material with a mixed gas jetted from an injection port. The drying tank is preferably formed in a cylindrical shape, and the mixed gas is jetted into the drying chamber in a circumferential tangential direction.

[0018] In this way, by injecting the mixed gas into the cylindrical drying tank in the circumferential tangential direction and opening it to the atmosphere, a stable air flow can be formed in the drying chamber, and the air flow can be further accelerated by volume expansion. This allows the material to be crushed and the crushed material to be dried efficiently in a deoxidized state.

[0019] It is preferable that a plurality of the injection ports are provided, so that the amount of the deoxygenated mixed gas injected into the drying chamber can be further increased.

[0020] The dried products produced in the drying process that have irregular or inappropriate moisture content, particle size, specific surface area, or porosity are stored and then fed back to the steam jet injection type dryer hopper by installing a transfer device, where they are mixed with newly-entered wet sludge and the supply and drying process is repeated the required number of times to obtain appropriate and uniform drying quality and to produce high-quality dried products without any waste. Effect of the Invention

[0021] In a drying device using a steam jet dryer, saturated steam is heated to superheated steam, which is forced to collide with the material to be treated, and the material is crushed and pulverized by supersonic shock waves, maximizing the evaporation surface area.The crushed material is then swirled with a high-temperature air flow and heat exchanged to dry it at high temperature and humidity, so the material can be dried efficiently, and the optimum moisture, particle size, specific surface area, bulk density, hygroscopicity, porosity, and angle of repose can be achieved by controlling the steam temperature, steam pressure, hot air temperature, hot air pressure, hot air / steam weight ratio, material supply amount, swirling residence time, and exhaust induced pressure.

[0022] For example, by having an average particle size of 3 μm or more and 25 μm or less, it is possible to increase the battery capacity per volume of the positive electrode active material, and to obtain a secondary battery that is highly safe and has good cycle characteristics. 2 / g~7.0m 2 / g, the particle surface area that can come into contact with the electrolyte is increased, sufficient charge / discharge capacity can be obtained, and safety can be ensured.

[0023] The object of the present invention is to solve the above-mentioned problems that the prior art has not solved, and to provide a finished product with a moisture content of 0.5%, an average particle size of 25 μm, and a specific surface area of ​​7 m 2 / g, moisture absorption 4.1%, angle of repose less than 50 degrees and bulk density 0.75g / cm 3 In the case of the above-mentioned dried product, it is possible to manufacture a high-quality and excellent raw material for secondary batteries.

[0024] In addition, the conventional drying method has a problem that it is difficult to provide a crushing function, for example. In order to provide a crushing function, a secondary mechanical crushing is generally performed separately, and the crushing and drying process is performed by combining collisions of solid objects with a blower, which creates an issue of running costs. In addition, when the final moisture content is required to be reduced to the limit, a secondary drying process is required in which a vacuum or reduced pressure state is created as a secondary process and the crushing and drying process is performed in that state, which causes a problem of a significant increase in the amount of capital investment.

[0025] A steam jet dryer is an effective pulverizing and drying device for solving these problems. This steam jet dryer crushes the material to be treated by shock waves (kinetic energy) by forcibly colliding supersonic air flow with the material to be treated, maximizing the evaporation surface area. Then, the material is swirled with hot air (thermal energy) and heat exchanged, so that the material can be efficiently pulverized and dried. The high-temperature mixed gas can be injected into the treatment tank at a sufficiently high pulverizing pressure, and although the maximum pressure was about 0.1 kPa in the past, it is now possible to use 5 kPa or 20 kPa, and the crushing force can be increased by 50 to 200 times compared to the past.

[0026] This steam jet dryer has the following configuration: As shown in Fig. 3, the material to be treated is supplied from a raw material inlet in the drying tank by, for example, a screw conveyor, a transport pump, etc. The supplied material is pulverized by a supersonic superheated steam jet generated by an ejector, and undergoes heat exchange while swirling along the inner wall of the drying tank, and is centrifuged, passes through the dried product and exhaust exhaust passage, and enters a separator (cyclone / bag filter), where the dried product is separated from the air and is discharged.

[0027] On the other hand, the high-temperature gas is heated by Joule heat generated by passing an electric current through various resistance wires, so it is supplied from an electric furnace that is free of unburned components such as SOX, NOX, COX, etc., and allows for safe, clean, and highly accurate temperature control, or the high-temperature combustion gas supplied by a combustion burner using natural gas, etc. is supplied to the hot air furnace body at a positive pressure of 5 to 20 kPa by a high-pressure blower in the hot air generator, cooled to 250 to 600°C, and sprayed toward the material to be treated as a mixed gas with superheated steam. It then passes through a drying treatment tank in a swirling motion, and the dried product and air are separated by a separator for exhaust treatment.

[0028] According to the present invention, low-oxygen, clean, high-temperature gas and air can be simultaneously injected into a treatment tank while maintaining the steam injection pressure from the steam injection nozzle, and the raw materials introduced through the raw material supply port can be effectively crushed and stirred by the injection pressure. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a flow diagram illustrating the steps of a lithium recovery method according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a flow diagram showing an outline of a drying step used in the lithium recovery method of FIG. 1. [Diagram 3] FIG. 3 is a schematic diagram showing the configuration of a drying device used in the lithium recovery method of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 shows the procedure of each step of the lithium recovery method of this embodiment, Fig. 2 shows the drying step for carrying out the lithium recovery, and Fig. 3 shows a schematic configuration of a drying device for carrying out the lithium recovery method. The method for recovering lithium and the method for recovering metals from a neutralization residue according to the present embodiment can be suitably used for drying treatment after filtration. In the following, an example will be described in which lithium is recovered from waste lithium-ion secondary batteries and used again as a raw material for lithium-ion secondary batteries, and metals are recovered from a neutralization residue generated in a filtration process for solid-liquid separation following the neutralization process.

[0031] As shown in FIG. 1, the method for recovering lithium from used lithium ion secondary batteries according to the present embodiment includes the following steps: - A process S2 of roasting and melting the waste lithium ion secondary battery S1; - A process for obtaining dry slag by a crushing and screening process S3; - a leaching step S4 of leaching with an inorganic acid to elute lithium; - a neutralization step S5 after the leaching step S4 by adding an alkali to adjust the pH; a carbonation step S10 in which carbon dioxide gas is mixed with the liquid to be treated after the neutralization step S5 and / or a water-soluble carbonate is added; - A simultaneous dripping step S14 of dripping hydrofluoric acid (HF) into the lithium carbonate aqueous solution precipitated by the carbonation step S10. - The lithium fluoride precipitated by the simultaneous dropping step S14 is filtered S7, repulped S15, and dried S8. The dried lithium fluoride is reacted in two steps with high-purity phosphorus pentafluoride (PF5) and anhydrous hydrogen fluoride (HF) to produce the electrolyte raw material lithium hexafluorophosphate (LiPF 6 ) and S17, which is manufactured. The lithium recovery method of the present embodiment further comprises: The positive electrode active material S13 is produced by washing the slurry obtained by reacting the lithium carbonate aqueous solution precipitated in step S10 with the lithium nickel composite oxide S-11 in step S12, filtering the slurry in step S7, and drying the slurry in step S8. The lithium recovery method of the present embodiment further comprises: a filtration and drying step S7 for separating the insoluble neutralization residue S6 from the lithium-containing solution obtained by the neutralization step S5; - Drying step S8 followed by metal recovery step S9.

[0032] As shown in FIG. 1, the drying process for recovering lithium from waste lithium-ion secondary batteries of the present embodiment includes the following steps: - Steam boiler unit U2 supplying saturated steam; - a superheater device U3 for heating the saturated steam to superheated steam; - a hot air generator U4 for generating high temperature and high pressure gas; a storage hopper U6 for supplying a fixed amount of lithium fluoride; - A crushing and separation treatment tank U7 in which the powder is crushed by a high-speed superheated steam jet and heat exchange occurs while swirling along the inner wall of the drying treatment tank. - A multi-cyclone device U8 and a bag filter device U9 that separate the dried product from the air; - A dry powder transfer device U10 and an exhaust induction blower U11 for the dry powder discharged from the separation devices U8 and U9.

[0033] This steam jet drying apparatus is configured as shown in FIG. A steam flow adjusting unit 2 that adjusts the flow of high-temperature, high-pressure steam supplied from the outside is disposed in the steam jet drying apparatus 1. That is, a steam pipe 3 for introducing high-temperature, high-pressure steam from the outside, a pressure reducing valve 4 for reducing the pressure of the steam, a flow rate adjusting valve 5 for adjusting the flow rate of the steam, a flowmeter 6 for measuring the flow rate of the steam, a pressure gauge 7 for measuring the steam pressure, and a steam pipe 8 for supplying the adjusted steam to a steam injection nozzle 10 in an ejector 15 are disposed.

[0034] In addition, a hot air generator 20 for supplying high-temperature air is connected to the drying device 1. The heating energy of the hot air generator 20 can be selected from electricity, natural gas, or the like. As an example, when natural gas is selected, there are provided a fuel gas supply pipe 21 for introducing fuel gas from outside, a fuel flow control valve 22 for adjusting the flow rate of the introduced air, a carrier air introduction pipe 23, a thermometer 27 for measuring the temperature of the high-temperature air, a pressure gauge 28 for measuring the pressure of this high-temperature air, and an oxygen concentration meter 29 for measuring the oxygen concentration of the high-temperature air.

[0035] The material to be treated is supplied from the raw material inlet 41 in the drying tank 35 by, for example, a screw conveyor, a conveying pump, etc. The supplied material to be treated is pulverized by high-speed air generated by the ejector 10, and undergoes heat exchange and centrifugation while entrained and swirling along the inner wall of the drying tank 35. The material enters the separator (cyclone / bag filter) through the dried product and exhaust gas exhaust passage, where the dried product and air are separated, and the dried product is discharged. The drying chamber 35 is connected to a dried product and exhaust gas exhaust passage 44, and a thermometer 45 for measuring the temperature of the exhaust gas and a pressure gauge 46 for measuring the pressure of the exhaust gas are disposed. The separator 50 is provided at its bottom with a dried product outlet 51. The separator is connected in this order to an exhaust pipe 52 for discharging the exhaust gas to the outside, a flow rate control valve 53 for adjusting the flow rate of the exhaust gas, and a blower 54 for discharging the exhaust gas to the outside.

[0036] The above-mentioned steam injection nozzle 10 is attached downstream of the steam flow adjustment unit 2 and is set so that the steam supplied from the steam flow adjustment unit 2 becomes a subsonic to supersonic steam flow from its injection port, and is injected into the treatment tank 15.

[0037] A throat is provided downstream of the nozzle 11 of the steam injection nozzle 10, and a diffuser is formed downstream of the throat. The mixed gas of steam injected from the steam injection nozzle 10 and high-temperature air supplied from the high-temperature air supply unit (hot air generator) 20 reaches its maximum speed in the throat, and is decelerated and pressurized by the diffuser to the required flow velocity, and the flow velocity at the nozzle outlet after being injected from the nozzle is adjusted to 200 to 650 m per second.

[0038] For materials that require a large pulverizing force, sufficient pulverization effect can be achieved by increasing the steam pressure to make the mixed gas flow at a supersonic speed or faster. That is, the flow speed of the mixed gas at the nozzle of the ejector 15 is directly proportional to the steam pressure, and if it is set to 0.26 MPa or higher, a shock wave will be generated, and if the steam pressure is increased, it will become supersonic and can exceed 350 m / s. On the other hand, the discharge air pressure supplied to the ejector 15 from the high-temperature air supply unit (hot air generator) 20 is supplied as a positive pressure of 5 kpa to 20 kpa.

[0039] As shown in Fig. 4, the nozzle of the ejector 15 opening into the inside of the drying chamber 35 is formed in a Laval nozzle shape that accelerates the gas flow to a supersonic speed. The drying chamber 35 is provided with a raw material inlet 41 and a dried product and exhaust gas outlet 44. A scraper that serves as a scraping mechanism rotated by a rotor may be provided inside the drying chamber 35, and the treated material is stirred and dried by this scraper.

[0040] In this manner, by spraying the mixture of steam and high-temperature air at an angle as close as possible to the circumferential tangent direction of the drying chamber 35, which is formed in a short cylindrical shape, the airflow within the drying chamber 35 can be further accelerated, and the material to be treated can be efficiently pulverized and the pulverized material can be stirred and dried.

[0041] Superheated steam, which is obtained by reheating saturated steam, can also be used. The oxygen content of superheated steam can be reduced to 1% or less, and the oxygen content of the gas mixture with the steam injected from the ejector can be significantly reduced. This superheated steam can be generated by reheating the steam exhausted from the drying chamber using a heat exchanger or the like, which is also advantageous in terms of cost.

[0042] The steam jet drying apparatus described above is merely one example, and various modifications are possible based on the gist of the present invention, and are not to be excluded from the scope of the present invention. [Industrial Applicability]

[0043] Lithium and valuable metals can be efficiently recovered from raw materials such as used EV storage batteries using the treatment liquid in which lithium and inorganic salts are dissolved, promoting the reuse of valuable resources. [Explanation of symbols]

[0044] Figure 1. Representative process diagram for lithium recovery method S-1 Discarded lithium-ion secondary batteries S-2 Roasting process (reduction and melting) S-3 Crushing and screening process (dry slag) S-4 Leaching process (pH adjustment) S-5 Neutralization process (Li solution) S-6 Neutralization residue S-7 Filtration process S-8 Drying process S-9 Metal recovery process S-10 Carbonation process (Li 2 CO 3 aqueous solution) S-11 Lithium nickel composite oxide S-12 Slurry washing process S-13 Cathode active material S-14 HF simultaneous dropping reaction process S-15 Repulp washing process S-16 PF 5 / HF Two-step reaction process S-17 Raw material for electrolyte (high purity LiPF 6 ) Figure 2. Flow diagram showing the outline of the drying process U-1 containing lithium raw material U-2 Steam Boiler Unit U-3 Superheater Device U-4 High pressure hot air generator U-5 Steam Ejector U-6 Storage Hopper U-7 Crushing and separation treatment tank U-8 Multi-cyclone device U-9 Bag filter device U-10 Dry powder transfer device U-11 Exhaust Induction Blower Figure 3: Schematic diagram showing the configuration of the drying device 1 Steam jet drying device 2. Steam flow regulator 3. Steam Pipe 4 Pressure Reducing Valve 5. Flow Control Valve 6 Flow meter 7. Pressure Gauge 8 Steam Pipe 10 Steam injection nozzle 15 Ejector 24 Flow control valve 25 Hot air generator 27 Thermometer 28 Pressure Gauge 29 Oxygen concentration meter 35 Drying room 41 Raw material inlet 42 Flow control valve 43 Raw material supply conduit 44 Dry goods and exhaust ducts 45 Thermometer 46 Pressure Gauge 50 separator 51 Dry product outlet 53 Flow control valve 54 Exhaust Induction Blower

Claims

1. A lithium recovery method comprising: a carbonation step of mixing carbon dioxide gas and / or adding a water-soluble carbonate to a liquid to be treated in which at least lithium and an inorganic salt are dissolved; a filtration step of performing solid-liquid separation of a precipitate containing lithium carbonate crystals precipitated by the carbonation step from the liquid to be treated; and a steam jet injection type drying step having a structure for mixing steam injected from a steam injection nozzle and high-temperature gas supplied from a high-temperature gas supply unit to inject superheated steam.

2. and a steam jet injection type drying step according to claim 1, characterized in that the steam jet is an injection nozzle that injects the superheated steam at subsonic to supersonic speed from a short distance toward a gas injection port provided near a treatment object supply port of the treatment tank, and the flow velocity of the superheated steam at the outlet is 200 to 650 m per second.

3. 2. The lithium recovery method according to claim 1, further comprising a steam jet drying step, characterized in that the high-temperature gas is a high-temperature gas, and the high-temperature gas supply unit dilutes and cools combustion air generated by a combustion burner or by a heating method using Joule heat generated by passing an electric current through various resistance wires to 250°C to 600°C using a carrier air high-pressure blower system, and adjusts the rotation speed of the carrier air blower to a discharge air pressure of 5 KPa to 20 kPa using an inverter or the like.

4. A method for recovering metals from a neutralization residue produced in the filtration step, further comprising: an acid dissolution step of leaching the dry slag with an inorganic acid to dissolve lithium before the carbonation step; and a neutralization step of adding an alkali to the lithium-containing liquid obtained in the acid dissolution step to adjust the pH, the method comprising: a filtration step of performing solid-liquid separation from a neutralization residue to obtain a precipitate precipitated in the pH adjustment step; and the steam jet injection type drying step according to any one of claims 1 to 3.

5. 2. The method for recovering lithium according to claim 1, wherein the high-temperature gas is a heated inert gas or superheated steam, and the pulverization and drying process is carried out in a low or deoxidized space having an oxygen concentration of 1% or less.

6. The method for recovering lithium according to claim 1, further comprising a transport device for feeding back to the hopper of the drying device the dried product having an inappropriate moisture content, particle size, specific surface area, and porosity produced in the drying process, and mixing and conditioning the dried product with newly-entered wet material to be treated, and repeating the supply and drying processes again.

7. 2. The method for recovering lithium according to claim 1, characterized in that the high-temperature gas is supplied so as to achieve a positive pressure of 0 kPa or more and 20 kPa or less in the vicinity of the air inlet of the ejector in the drying process, thereby relatively reducing the steam ratio of the mixed gas of steam and the high-temperature gas.

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