Method for extracting lithium from ore by using molten salt method

Abstract

The invention provides a method for extracting lithium from ore by a molten salt method, which comprises the following steps: jointly heating a sodium and potassium mixed salt and an alkaline additive to a molten state, adding lithium-containing ore, jointly heating and roasting, and carrying out water leaching and filtering on clinker to obtain lithium-containing brine. Based on alkaline roasting of the lithium-containing ore, the conventional alkaline lithium extraction method is improved, and the low-temperature fused salt is added into the auxiliary material and is fused in the heating process, so that the contact efficiency of the lithium ore and sodium hydroxide is enhanced, and the leaching rate of lithium is further improved on the premise of reducing the roasting energy consumption; the method has the characteristics of simple process, low roasting temperature, high recovery efficiency and the like, and has certain industrial application value.

Description

Technical Field

[0001] The invention relates to a method for extracting lithium from lithium-containing ores, and in particular to a method for extracting lithium from ores using a molten salt method. Background Art

[0002] The current mainstream electrochemical energy storage battery is lithium battery, which accounts for 92% of the global electrochemical energy storage installed capacity. As the main raw material of lithium batteries, the market demand for lithium resources is growing continuously. It is estimated that by 2025, the global demand for lithium resources will exceed 90×10 4 t (lithium carbonate equivalent), it is imperative to develop lithium extraction technology.

[0003] Lithium resources mainly come from salt lake brine and lithium ore. Lithium ore has a wide distribution range, large resources and relatively mature mining technology. The most commonly used ones are spodumene, lithium mica and lithium aluminum phosphate. At present, for lithium-containing ores, the main methods of lithium extraction are limestone sintering, chlorination roasting, sulfate roasting, alkaline pressure cooking and sulfuric acid method. Among them, limestone sintering, sulfate roasting and chlorination roasting using solid chlorinating agent are all methods of roasting lithium ore and solid auxiliary materials, and then adding water to the clinker to leaching lithium. The limestone sintering method has low requirements for production equipment, but the leaching rate is not high, generally only about 62% to 65%, and is mostly used for lithium mica concentrate with a lithium content of about 4.5%. The chlorination roasting method requires a relatively short roasting time, has a high lithium extraction efficiency and a relatively simple production process, but it is easy to pollute the environment and corrode the roasting equipment. The sulfate sintering method avoids the use of a large amount of sulfuric acid, has a high lithium extraction efficiency and fewer impurities. However, it is easy to produce polluting gas, the cost is also high, and the roasting temperature needs to be strictly controlled. At the same time, the roasting temperature in the above lithium extraction methods is basically high temperature, generally around 850-900°C.

[0004] Patent CN106591564A provides a roasting additive for extracting lithium from lithium ore, which mainly uses active calcium carbonate, sodium sulfate, sodium hydroxide, and calcium oxide as roasting additives, which are evenly mixed with lithium ore and roasted at a temperature of about 920 to 1140°C, and then the lithium is leached out with dilute sulfuric acid or dilute hydrochloric acid. This invention can greatly improve the roasting conversion rate of lithium ore while reducing harmful gas emissions, but the roasting temperature is still high and the production energy consumption is large. It can be seen that it is very necessary to propose a method that can not only ensure the lithium leaching rate, but also reduce the roasting temperature and facilitate lithium leaching.

[0005] Patent CN115198110A provides a method for extracting lithium rubidium and cesium from pegmatite lithium concentrate. The method mainly uses sodium hydroxide and calcium oxide as roasting additives, mixes them evenly with lithium ore, and then roasts them at a temperature of about 500-700°C, and then uses water to leach lithium. From the examples of this patent, it can be found that when the leaching rate of lithium is good, the amount of sodium hydroxide is large. When the amount of sodium hydroxide is small, the leaching efficiency of lithium is poor. For example, iron lithium mica concentrate, NaOH and CaO are mixed evenly in a mass ratio of 1:2.2:0.4 and then roasted at 650°C for 90 minutes. The leaching rate of lithium after water leaching is 78.8%. However, under the same conditions, when the iron lithium mica concentrate, NaOH and CaO are in a mass ratio of 1:1:0.4, the leaching rate of lithium is only 25%.

[0006] It can be seen that how to ensure lithium leaching while reducing the amount of sodium hydroxide is also worthy of attention. Summary of the invention

[0007] The purpose of the present invention is to provide a method for extracting lithium from ore by molten salt method, which uses a mixed salt with a low eutectic point to melt it during the heating process, and adds a liquid medium to the solid-solid reaction of the original roasting process for lithium extraction, thereby enhancing the contact efficiency between lithium ore and sodium hydroxide. It can reduce the energy consumption of roasting, reduce the amount of sodium hydroxide used, reduce the cost of raw materials, and has strong practicality and good comprehensive benefits.

[0008] In order to achieve the above object, the present invention adopts the following technical solution: A method for extracting lithium from lithium ore by molten salt roasting, comprising the following technical steps: (1) placing a sodium and potassium mixed salt and an alkaline additive in a ball mill for crushing and mixing to obtain a mixed material; (2) heating the mixture obtained in step (1) to a molten state; (3) drying and crushing the untreated lithium ore to a certain particle size; (4) adding the crushed lithium ore obtained in step (3) into the molten material in step (2) and mixing and roasting; (5) cooling the roasted clinker obtained in step (4), and adding a leaching solution to leach lithium; (6) filtering the system obtained in step (5), removing the waste residue, and obtaining lithium-containing brine; (7) The lithium-containing brine obtained in step (6) is subjected to treatments such as impurity removal, concentration and crystallization to obtain a lithium carbonate product.

[0009] Furthermore, the sodium and potassium mixed salt used in step (1) is potassium chloride and sodium sulfate, and the mass ratio thereof is 1:(0.8-1.5).

[0010] Furthermore, the alkaline additive used in step (1) is sodium hydroxide, and the mass ratio of sodium hydroxide to the mixed salt of sodium and potassium is 1:(8.2-14.6).

[0011] Furthermore, the heating temperature used in step (2) is 480-600°C.

[0012] Furthermore, the lithium ore used in step (3) is one or more of spodumene, lepidolite, pyroxenite, petalite, and ferrolithium mica, wherein the lithium oxide content is 0.5 to 4.5 wt%.

[0013] Furthermore, after the lithium ore is crushed in step (3), the particle size is ≤75 μm.

[0014] Furthermore, in step (4), the mass ratio of lithium ore to molten material is 1:(8.5-16.5), and the temperature still needs to be maintained at 400-650° C. for mixed roasting, and the mixed roasting time is 1-6 hours.

[0015] Furthermore, the leaching liquid in step (5) is water, the solid-liquid mass ratio is 1:(4.2-16.5), the leaching temperature is 20-100° C., and the leaching time is 0.5-4 h.

[0016] Compared with the prior art, the advantages of the present invention are: (1) The material roasting temperature is reduced. Compared with traditional lithium extraction methods of lepidolite, such as limestone sintering method and sulfate roasting method, the roasting temperature is about 850-900°C, and the roasting energy consumption is relatively high. The present invention uses low-temperature mixed molten salt, which can melt at about 480-600°C to form a liquid medium, thereby enhancing the contact efficiency between sodium hydroxide and lithium ore, thereby ensuring lithium leaching at a lower roasting temperature than the traditional roasting lithium extraction method.

[0017] (2) Reduce the amount of sodium hydroxide used. Compared with other methods of extracting lithium by alkali roasting, this method further saves the amount of sodium hydroxide used and the cost of raw materials by crushing the molten salt and sodium hydroxide together and enhancing the contact efficiency between lithium ore and alkali with the help of molten salt, while ensuring the lithium leaching rate.

[0018] (3) The process is short and easy to realize industrial production. The main process of this method is to make molten salt, crush lithium ore, mix roasting, and add water for leaching. The process is simple and has low requirements on process conditions, which is conducive to industrial production.

[0019] (4) High lithium recovery rate. When lithium mica with a lithium content of about 0.85% was tested according to the method of the invention, it was found that the lithium content in the slag could be reduced to about 0.1% at the lowest, and the lithium leaching rate could reach more than 90%.

[0020] (5) The auxiliary materials required are few in number and easy to obtain. The present invention uses sodium-potassium mixed salt and sodium hydroxide as auxiliary materials, which are all easy to obtain industrial products with low prices and are easy to purchase. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a process flow chart of the present invention.

[0022] Figure 2 This is the XRD analysis diagram of the lithium extraction waste residue obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below through specific implementation methods, but the present invention is not limited thereto. Various changes and substitutions made by those skilled in the art based on the present invention should all fall within the scope of the claims attached to the present invention as long as they do not depart from the spirit of the present invention.

[0024] The embodiment described aims at preparing lithium carbonate, wherein the process is to prepare lithium-containing brine containing impurities, and the brine can be further treated to remove impurities and purify, so as to prepare an industrial-grade lithium carbonate product.

[0025] Example 1 (1) 9 g of potassium chloride, 11 g of sodium sulfate and 6 g of sodium hydroxide were put into a ball mill, crushed and mixed to obtain a mixture, and heated at 530° C. to a molten state.

[0026] (2) Take 2 g of lithium mica with a lithium oxide content of 1.81 wt% and crush it into 200 mesh. Add the crushed lithium mica to the molten material and calcine at 530°C for 300 minutes while maintaining the temperature.

[0027] (3) After cooling, the clinker is taken out and water is added for leaching. The solid-liquid mass ratio is 1:10, the leaching temperature is 80° C., and the leaching time is 120 minutes. After completion, the solid-liquid separation is performed to obtain lithium-containing brine. The lithium leaching rate is measured to be 91.62%.

[0028] The XRD analysis diagram of the lithium extraction waste residue obtained in this embodiment is as follows: Figure 2 As shown, from the XRD analysis diagram, it can be found that the peak of the lithium mica ore has basically disappeared, indicating that the ore has been basically destroyed and the lithium in it has been effectively leached.

[0029] Example 2 (1) 9 g of potassium chloride, 11 g of sodium sulfate and 4 g of sodium hydroxide were put into a ball mill, crushed and mixed to obtain a mixture, and heated at 530° C. to a molten state.

[0030] (2) Take 2 g of lithium mica with a lithium oxide content of 1.81 wt% and crush it into 200 meshes. Add the crushed lithium mica into the molten material, maintain the temperature, and calcine at 530° C. for 260 minutes.

[0031] (3) After cooling, the clinker is taken out and water is added for leaching. The solid-liquid mass ratio is 1:10, the leaching temperature is 80° C., and the leaching time is 150 minutes. After completion, the solid-liquid separation is performed to obtain lithium-containing brine and filter residue. The lithium leaching rate is measured to be 83.67%.

[0032] Example 3 (1) 4.5 g of potassium chloride, 5.5 g of sodium sulfate and 3 g of sodium hydroxide were put into a ball mill, crushed and mixed to obtain a mixture, and heated at 530° C. to a molten state.

[0033] (2) Take 2 g of lithium mica with a lithium oxide content of 1.81 wt% and crush it into 300 meshes. Add the crushed lithium mica into the molten material, maintain the temperature, and calcine at 530° C. for 300 minutes.

[0034] (3) After cooling, the clinker is taken out and water is added for leaching. The solid-liquid mass ratio during leaching is 1:10, the leaching temperature is 80° C., and the leaching time is 120 minutes. After completion, the solid-liquid separation is performed to obtain lithium-containing brine and filter residue. The lithium leaching rate is measured to be 81.76%.

[0035] Comparative Example 1 (1) 2 g of lepidolite with a lithium oxide content of 1.81 wt% was crushed into 200 meshes. The crushed lepidolite was added with 6 g of sodium hydroxide and mixed in a ball mill to obtain a mixture.

[0036] (2) The mixture was placed in a tube furnace and calcined at 530°C for 300 minutes.

[0037] (3) After cooling, the clinker is taken out and water is added for leaching. The solid-liquid mass ratio is 1:10, the leaching temperature is 80° C., and the leaching time is 120 minutes. After completion, the solid-liquid separation is performed to obtain lithium-containing brine. The lithium leaching rate is measured to be 88.14%.

[0038] Comparative Example 2 (1) 2 g of lepidolite with a lithium oxide content of 1.81 wt% was crushed into 200 meshes. 4 g of sodium hydroxide was added to the crushed lepidolite, and the mixture was put into a ball mill to obtain a mixture.

[0039] (2) The mixture was placed in a tube furnace and calcined at 530°C for 260 minutes.

[0040] (3) After cooling, the clinker is taken out and water is added for leaching. The solid-liquid mass ratio is 1:10, the leaching temperature is 80° C., and the leaching time is 150 minutes. After completion, the solid-liquid separation is performed to obtain lithium-containing brine. The lithium leaching rate is measured to be 77.03%.

[0041] Comparative Example 3 (1) 2 g of lepidolite with a lithium oxide content of 1.81 wt% was crushed to 300 mesh. 3 g of sodium hydroxide was added to the crushed lepidolite, and the mixture was put into a ball mill to obtain a mixture.

[0042] (2) The mixture was placed in a tube furnace and calcined at 530°C for 300 minutes.

[0043] (3) After cooling, the clinker is taken out and water is added for leaching. The solid-liquid mass ratio is 1:10, the leaching temperature is 80° C., and the leaching time is 120 minutes. After completion, the solid-liquid separation is performed to obtain lithium-containing brine. The lithium leaching rate is measured to be 69.63%.

[0044] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for extracting lithium from ore by molten salt method, which is characterized by the following steps: (1) placing a sodium and potassium mixed salt and an alkaline additive in a ball mill for crushing and mixing to obtain a mixed material; (2) heating the mixture obtained in step (1) to a molten state; (3) drying and crushing the lithium ore to a certain particle size; (4) adding the crushed lithium ore obtained in step (3) into the molten material in step (2) and mixing and roasting; (5) cooling the roasted clinker obtained in step (4), and adding a leaching solution to leach lithium; (6) filtering the system obtained in step (5), removing the waste residue, and obtaining lithium-containing brine; (7) The lithium-containing brine obtained in step (6) is subjected to impurity removal, concentration and crystallization treatment to obtain a lithium carbonate product.

2. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: The sodium and potassium mixed salt used in step (1) is potassium chloride and sodium sulfate, and the mass ratio thereof is 1:(0.8-1.5).

3. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: The alkaline additive used in step (1) is sodium hydroxide.

4. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: In step (1), the mass ratio of the alkaline additive to the sodium-potassium mixed salt is 1:(8.2-14.6).

5. The method for extracting lithium from lithium ore by molten salt roasting according to claim 1, characterized in that: The heating temperature in step (2) is 480-600°C.

6. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: The lithium ore used in step (3) is one or more of spodumene, lepidolite, pyroxenite, petalite, and ferrolithium mica, wherein the lithium oxide content is 0.5 to 4.5 wt%.

7. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: After the lithium ore is crushed in step (3), the particle size is ≤75 μm.

8. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: In step (4), the mass ratio of lithium ore to molten material is 1:(8.5-16.5).

9. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: In step (4), the mixed calcination temperature is maintained at 400-650° C., and the mixed calcination time is 1-6 hours.

10. The method for extracting lithium from ore by molten salt method according to claim 1, characterized in that: The leaching liquid in step (5) is water, the solid-liquid mass ratio is 1:(4.2-16.5), the leaching temperature is 20-100° C., and the leaching time is 0.5-4 h.

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