Method for extracting lithium metal element mineral from coal

Abstract

The application discloses a kind of coal lithium metal element mineral extraction methods, belong to coal resource comprehensive utilization technical field;Method includes: raw coal washing, physical pre-enrichment, low-temperature synergistic activation, gradient acid leaching, leaching liquid purification, lithium product is precipitated.The lithium is enriched in coal gangue by raw coal gravity separation, and is pre-enriched after crushing and grinding screening + floating sinking;400 DEG C low-temperature calcination + composite additive intercalation activation is used, and lithium is released by destroying mineral lattice;Gradient hydrochloric acid step leaching, inhibit impurity dissolution;Complex impurity removal + solvent extraction purifies lithium, and high-purity lithium carbonate is obtained by carbonization precipitation.The lithium leaching rate of the application is greater than or equal to 94.32%, the comprehensive recovery rate is greater than or equal to 90%, the activation temperature is reduced by 33%, the energy consumption is reduced by 40%, the impurity dissolution rate is reduced by 30-50%, the process is green and efficient, suitable for various coal lithium resources, realizes coal gangue high-value resource, and guarantees national lithium resource security.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of coal-associated mineral resources, specifically to a method for extracting lithium metal from coal. Background Technology

[0002] Lithium, as a new energy metal, is widely used in power batteries, energy storage batteries, aerospace, new materials, and other fields, and is a strategic key metal for the country. my country's dependence on imported lithium resources exceeds 70%, and traditional lithium mining is limited by factors such as geographical environment and ecological protection, making it urgent to explore new lithium resource supply channels.

[0003] The average lithium content in Chinese coal reaches 31.8 μg / g, far exceeding the world average (12 μg / g). In some coal-bearing areas of North and South China, lithium content exceeds 120 μg / g (industrial grade). Super-large coal-series lithium resources have been discovered in the Zhungeer Coalfield, Ningwu Coalfield, and Pingshuo Mining Area. Coal gangue, a major byproduct of coal washing, is emitted at an annual rate of 600-800 million tons. Lithium is mainly concentrated in coal gangue, making it a highly promising alternative source of lithium resources.

[0004] Existing coal-based lithium extraction technologies have the following drawbacks: 1. Extremely low direct leaching rate: Lithium in coal gangue is mainly found in the crystal lattice of aluminosilicate minerals such as kaolinite and boehmite. The direct acid leaching lithium leaching rate is <25%, resulting in poor resource utilization. 2. High energy consumption in activation process: Conventional roasting activation temperature ≥600℃, time ≥1h, high energy consumption, high cost, difficult to industrialize; 3. Poor process selectivity: During the leaching process, a large amount of impurities such as aluminum, iron, and silicon are dissolved, making lithium separation and purification difficult and resulting in low product purity; 4. Lack of synergistic enrichment: The entire process of washing, classifying, activating and leaching is not optimized, resulting in low lithium enrichment factor and an overall recovery efficiency of less than 60%.

[0005] In published patents and literature, most of the processes used are high-temperature roasting-strong acid leaching. For example, the method in CN105692659A includes a one-step process of alkali dissolution, filtration and washing, adsorption, desorption, concentration and carbonation precipitation. It uses sodium carbonate roasting to extract lithium at a temperature of 900℃, which is energy-intensive. Existing technologies have not achieved the integration of low-temperature activation, efficient leaching, impurity suppression and synergistic enrichment, which seriously restricts the industrial application of coal-based lithium resources.

[0006] Therefore, developing a low-temperature activation, high leaching rate, low impurity dissolution, green and efficient method for extracting lithium metal elements from coal is of great significance for realizing the high-value utilization of coal gangue resources and ensuring national lithium resource security. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a method for extracting lithium metal from coal. Addressing the shortcomings of existing technologies, such as low leaching rate, high energy consumption, numerous impurities, and complex processes, this invention provides a method for extracting lithium metal from coal that achieves low-temperature activation, efficient leaching, impurity suppression, and synergistic enrichment, with a lithium leaching rate ≥94% and a comprehensive recovery rate ≥90%. The process is green and low-cost, suitable for industrial application.

[0008] To achieve the above objectives, the present invention provides a method for extracting lithium metal from coal, comprising the following steps: Raw coal washing and classification: Raw coal is separated by jigging or heavy medium shallow trough to obtain clean coal, middlings, coal slime and coal gangue, with lithium being directionally enriched into coal gangue; Physical pre-enrichment: Coal gangue is crushed, ground, screened, and classified by flotation and sedimentation to obtain lithium pre-enriched material; Low-temperature synergistic activation: The pre-enriched material is activated by a two-step method of low-temperature oxidation roasting and auxiliary agent intercalation activation to obtain activated material; Gradient acid leaching for lithium extraction: The activated material is leached with hydrochloric acid of varying concentrations and in stages with controlled temperature to suppress the dissolution of impurities and extract lithium efficiently; Leachate purification: Lithium is purified by complexation to remove impurities and by extraction to enrich and purify it, resulting in high-purity lithium solution; Lithium precipitation product: High-purity lithium liquid is carbonized and precipitated to obtain lithium carbonate product.

[0009] Step 1: Raw coal washing and grading Sorting process: jigging or heavy medium shallow trough sorting, sorting density 1.5~2.0g / cm³, sorting particle size ≤100mm; sorting effect: lithium migrates and enriches in coal gangue, coal gangue lithium content 400~450μg / g, ash content ≥65%.

[0010] Step 2: Physical pre-enrichment Crushing and grinding: Coal gangue is crushed to ≤5mm and wet-ground to 200~325 mesh; Screening and grading: The screening process controls the particle size to +0.125mm and the lithium enrichment factor to 1.06; Float-sink fractionation: The density of the heavy liquid was 2.2~2.4 g / cm³, and a high-density component of +2.4 g / cm³ was obtained, with a lithium enrichment factor of 1.16. Pre-enriched material: lithium content 460~510μg / g, yield 40~45%.

[0011] Step 3: Low-temperature synergistic activation Low-temperature oxidation calcination: calcination temperature 380~420℃, time 15~25min, air atmosphere, air flow rate 0.5~1.0L / min; Intercalation activation with additives: An intercalation additive is added to the calcined product, the intercalation time is 10-15 minutes, and the amount of additive is 3-5% of the material mass; Activation mechanism: Kaolinite is transformed into active metakaolinite, boehmite undergoes dehydroxylation and decomposition, lithium is released from the mineral lattice, and the activity of the activated material is increased by 3 to 5 times.

[0012] The intercalation aid is a composite aid of dimethyl sulfoxide and ammonium chloride, with a mass ratio of 1:0.5~1.

[0013] Step 4: Gradient acid leaching for lithium extraction Leaching system: hydrochloric acid solution, using gradient concentration combined with stepwise temperature control; First-stage leaching: hydrochloric acid concentration 0.5~1.0mol / L, temperature 30~40℃, time 30~60min, to dissolve easily soluble impurities; Two-stage leaching: hydrochloric acid concentration 2.0~2.5mol / L, temperature 55~65℃, time 240~300min, liquid-solid ratio 8~12:1, stirring speed 200~300r / min; Leaching effect: Lithium leaching rate was 94.32-96.5%, while aluminum and iron leaching rates decreased by 30-40% and 4-50%, respectively.

[0014] Step 5: Purification of leachate Complexation and impurity removal: Add a complexing agent at a dosage of 1-3% of the leachate volume, adjust the pH to 3.0-4.0, remove iron, aluminum, and silicon impurities, with a removal rate ≥95%; Solvent extraction: organic phase tributyl phosphate-sulfonated kerosene, volume ratio 1:2~3, phase ratio 1:3~5, extraction time 5~10 min, lithium extraction rate ≥99%; Back-extraction: Back-extract with 2~3 mol / L hydrochloric acid to obtain a high-purity lithium solution with a lithium concentration of 5~8 g / L.

[0015] The complexing agent is a composite complexing agent of citric acid and oxalic acid, with a mass ratio of 1:1 to 1.5.

[0016] Step 6: Lithium precipitation products Carbonization precipitation: Heat high-purity lithium liquid to 60~80℃, introduce CO2 at a flow rate of 0.3~0.5L / min, adjust pH to 7.0~8.0, and precipitate for 60~90min; Filtration and washing: The crude lithium carbonate is obtained by filtration and washed with deionized water 2-3 times; Drying and calcination: Dry at 100~120℃ and calcine at 300~400℃ for 30~60 min to obtain a product with Li2CO3 purity ≥99.5%.

[0017] In summary, this invention provides a method for extracting lithium metal from coal, achieving the following beneficial effects: 1. Extremely high leaching rate: Lithium leaching rate ≥94.32%, comprehensive recovery rate ≥90%, far exceeding direct leaching (<25%); Low temperature and low energy consumption: Activation temperature 400℃, 33% lower than the traditional 600℃, time shortened by 60%, and energy consumption reduced by 40%; Significant impurity suppression: Aluminum and iron leaching rates reduced by 30~50%, purification process simplified, product purity ≥99.5%; 2. High efficiency in synergistic enrichment: The entire process of washing, classifying, activating and leaching is optimized, with a lithium enrichment factor of ≥1.27; Green and environmentally friendly: Acid can be recycled, waste residue can be used to make building materials, there is no secondary pollution, and the resource utilization rate of coal gangue is ≥95%; Strong process adaptability: Applicable to various coal-based lithium resources such as Zhungeer, Pingshuo, and Ningwu, suitable for industrial continuous production. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow for the method of extracting lithium metal element from coal according to the present invention; Figure 2 This is a table of optimized key process parameters for the method of extracting lithium metal from coal in this invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments.

[0020] like Figures 1 to 2 As shown: Example 1

[0021] This invention employs a method for extracting lithium metal from coal, the steps of which are as follows: Raw coal washing and grading: Inner Mongolia Zhungeer raw coal, heavy medium shallow trough separation, density 1.8g / cm³, yielded coal gangue with a lithium content of 437.43μg / g; Physical pre-enrichment: Coal gangue was crushed and ground to 200 mesh, sieved to +0.125mm, with a float / sink ratio of 2.4g / cm³, and the lithium content of the pre-enriched material was 505.58μg / g; Low-temperature synergistic activation: calcination at 400℃ for 20 min, addition of 4% dimethyl sulfoxide-ammonium chloride composite additive (1:0.8), intercalation for 12 min; Gradient acid leaching for lithium extraction: First stage: 0.8 mol / L hydrochloric acid, 35℃, 45 min; Second stage: 2.0 mol / L hydrochloric acid, 60℃, 240 min, liquid-solid ratio 10:1; Leachate purification: 2% citric acid-oxalic acid complexing agent, pH 3.5, to remove impurities; tributyl phosphate-sulfonated kerosene extraction, back-extraction to obtain high-purity lithium solution; Lithium precipitation product: CO2 was passed through at 70℃, pH 7.5, precipitation was carried out for 60 min, washed, dried and calcined to obtain lithium carbonate product. Example 2

[0022] Raw coal washing and grading: Inner Mongolia Zhungeer raw coal, heavy medium shallow trough separation, density 1.8g / cm³, yielded coal gangue with a lithium content of 437.43μg / g; Physical pre-enrichment: Coal gangue was crushed and ground to 200 mesh, sieved to +0.125mm, with a float / sink ratio of 2.4g / cm³, and the lithium content of the pre-enriched material was 505.58μg / g; Low-temperature synergistic activation: calcination at 380℃ for 20 min, addition of 3% dimethyl sulfoxide-ammonium chloride composite additive (1:0.8), intercalation for 12 min; Gradient acid leaching for lithium extraction: First stage: 0.8 mol / L hydrochloric acid, 35℃, 45 min; Second stage: 2.2 mol / L hydrochloric acid, 60℃, 240 min, liquid-solid ratio 10:1; Leachate purification: 2% citric acid-oxalic acid complexing agent, pH 3.5, to remove impurities; tributyl phosphate-sulfonated kerosene extraction, back-extraction to obtain high-purity lithium solution; Lithium precipitation product: CO2 was passed through at 70℃, pH 7.5, precipitation was carried out for 60 min, washed, dried and calcined to obtain lithium carbonate product.

[0023] The difference between Example 2 and Example 1 is that the calcination temperature is 380℃, the intercalation aid is 3%, and the concentration of the second-stage hydrochloric acid is 2.2mol / L. Example 3

[0024] Raw coal washing and grading: Inner Mongolia Zhungeer raw coal, heavy medium shallow trough separation, density 1.8g / cm³, yielded coal gangue with a lithium content of 437.43μg / g; Physical pre-enrichment: Coal gangue was crushed and ground to 200 mesh, sieved to +0.125mm, with a float / sink ratio of 2.4g / cm³, and the lithium content of the pre-enriched material was 505.58μg / g; Low-temperature synergistic activation: calcination at 420℃ for 20 min, addition of 5% dimethyl sulfoxide-ammonium chloride composite additive (1:0.8), intercalation for 12 min; Gradient acid leaching for lithium extraction: First stage: 0.8 mol / L hydrochloric acid, 35℃, 45 min; Second stage: 2.0 mol / L hydrochloric acid, 65℃, 240 min, liquid-solid ratio 10:1; Leachate purification: 2% citric acid-oxalic acid complexing agent, pH 3.5, to remove impurities; tributyl phosphate-sulfonated kerosene extraction, back-extraction to obtain high-purity lithium solution; Lithium precipitation product: CO2 was passed through at 70℃, pH 7.5, precipitation was carried out for 60 min, washed, dried and calcined to obtain lithium carbonate product.

[0025] The difference between Example 3 and Example 1 is: calcination temperature 420℃, intercalation agent 5%, and two-stage leaching temperature 65℃.

[0026] Comparison of the technical solution of Example 1 with the extraction results of lithium metal element minerals from coal in existing technologies: 1. Existing technology uses direct acid leaching: coal gangue is directly leached with 2.0 mol / L hydrochloric acid at 60°C for 240 min. Result: Lithium leaching rate is 22.3%, which is far lower than that of this invention.

[0027] 2. Traditional high-temperature calcination: calcination at 600℃ for 60 min, without intercalation activation, the rest is the same as in Example 1. Results: lithium leaching rate 82.5%, energy consumption 40% higher, impurity dissolution rate 50% higher.

[0028] The principle of the technical solution of this invention is as follows: Gravity separation-oriented enrichment: Lithium is present in aluminosilicate minerals and has a high density. During gravity separation, it migrates directionally to coal gangue, achieving preliminary enrichment. Physical classification enhancement: The lithium content of the +0.125mm and +2.4g / cm³ components is the highest, and pre-enrichment is achieved by combining sieving with flotation and sedimentation. Low-temperature synergistic activation: Low-temperature calcination at 400℃ removes organic matter, kaolinite is converted to metakaolinite; intercalation aids expand the interlayer spacing, break Si-O and Al-O bonds, and release lithium lattice; Gradient leaching for impurity control: low concentration at low temperature for impurity removal, high concentration at high temperature for lithium extraction, reducing impurity leaching and improving lithium selectivity; Complexation extraction purification: impurities are chelated by a complex complexing agent, lithium is efficiently enriched by solvent extraction, and high-purity lithium carbonate is obtained by carbonization precipitation.

[0029] The embodiments described in this invention are for illustrative purposes only and do not constitute a limitation on the scope of the claims. Other substantially equivalent substitutions that can be conceived by those skilled in the art are all within the scope of protection of this invention.

Claims

1. A method for extracting lithium metal from coal, characterized in that, Includes the following steps: Step 1: Raw coal washing and classification: Raw coal is separated by jigging or heavy medium shallow trough separation, and lithium is directionally enriched into coal gangue; Step 2: Physical pre-enrichment: Coal gangue is crushed, ground, screened and classified by flotation and sedimentation to obtain lithium pre-enriched material; Step 3: Low-temperature synergistic activation: The pre-enriched material is activated by low-temperature oxidation roasting and intercalation with additives to obtain activated material; Step 4: Gradient acid leaching for lithium extraction: The activated material is leached stepwise with hydrochloric acid of varying concentrations at controlled temperatures to obtain a lithium-containing leachate; Step 5: Leachate purification: The lithium-containing leachate is purified by complexation to remove impurities and solvent extraction to obtain high-purity lithium solution; Step 6: Lithium precipitation product: High-purity lithium liquid is carbonized and precipitated to obtain lithium carbonate product.

2. The method for extracting lithium metal from coal according to claim 1, characterized in that, In step 1, the sorting density is 1.5~2.0 g / cm³, the coal gangue lime content is ≥65%, and the lithium content is 400~450 μg / g.

3. The method for extracting lithium metal from coal according to claim 1, characterized in that, In step 2, the grinding particle size is 200~325 mesh, the sieve size is +0.125mm, the floating density is 2.2~2.4g / cm³, and the high-density component with +2.4g / cm³ is separated.

4. The method for extracting lithium metal from coal according to claim 1, characterized in that, In step 3, the low-temperature oxidation calcination temperature is 380~420℃, the time is 15~25min, and the atmosphere is air; the intercalation aid is a dimethyl sulfoxide or ammonium chloride composite aid, and the dosage is 3~5%.

5. The method for extracting lithium metal from coal according to claim 1, characterized in that, In step 4, gradient acid leaching is performed: the first stage uses hydrochloric acid with a concentration of 0.5~1.0 mol / L and a temperature of 30~40℃; the second stage uses hydrochloric acid with a concentration of 2.0~2.5 mol / L, a temperature of 55~65℃, a time of 240~300 min, and a liquid-to-solid ratio of 8~12:

1.

6. The method for extracting lithium metal from coal according to claim 1, characterized in that, In step 5, the complexing agent is a combination of citric acid and oxalic acid, with a dosage of 1-3% and a pH of 3.0-4.0; the extraction organic phase is tributyl phosphate-sulfonated kerosene, with a volume ratio of 1:2-3.

7. The method for extracting lithium metal from coal according to claim 1, characterized in that, In step 6, the carbonization precipitation temperature is 60~80℃, CO2 is introduced, pH is 7.0~8.0, and the product is dried and calcined to obtain Li2CO3 with a purity ≥99.5%.

8. The method for extracting lithium metal from coal according to claim 1, characterized in that, Lithium leaching rate ≥94.32%, overall recovery rate ≥90%.

9. The method for extracting lithium metal from coal according to claim 4, characterized in that, The mass ratio of the composite additives is 1:0.5~1.

10. The method for extracting lithium metal from coal according to claim 1, characterized in that, With a purity of ≥99.5%, it is suitable for power battery applications.

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