A supercritical CO 2 Method for recovering lithium from lithium-containing coal-bearing rocks by fluid treatment

Abstract

The present invention discloses a method for recovering lithium by treating lithium-bearing coal measures rocks with supercritical CO2 fluid, which includes performing grinding and sieving treatment on ore samples; adding industrial soft water with an L / S of 0.5 to 1.5 into a supercritical CO2 fluid extraction device to form an aqueous solution system, adding the ground ore samples and pressure leaching aids into the aqueous solution system for extraction; after the extraction process, performing solid-liquid separation operation to obtain pressure leached lithium solution; reducing the pressure of the pressure leached lithium solution to convert the supercritical CO2 fluid into a gaseous state, and recovering and separating CO2 to obtain concentrated pressure leached lithium solution. Through the solid-liquid separation operation of supercritical CO2 fluid extraction, the present invention can quickly penetrate into the micropores of coal measures rocks, and with the help of additives, can efficiently dissolve lithium elements so as to separate lithium from the rocks.

Description

Technical Field

[0001] The present invention relates to the technical field of recovering lithium from lithium-containing coal-bearing rocks, and in particular to a method of recovering lithium from lithium-containing coal-bearing rocks using supercritical CO 2 A method for recovering lithium from lithium-bearing coal-bearing rocks by fluid disposal. Background Art

[0002] Lithium (Li) is an important strategic metal resource and plays a vital role in the field of new energy technology. At present, the lithium deposits discovered in the world are mainly divided into three categories: brine type, pegmatite type and sedimentary clay type. Although my country's lithium mineral resources are relatively rich, most of the lithium mines are distributed in the Qinghai-Tibet Plateau, with poor development conditions, and most of the lithium extraction technologies for brine-type lithium mines are not yet fully mature. The development and utilization of resources are subject to both environmental and technical constraints.

[0003] For example, patent CN 117867293 A reports a method for leaching lithium from fly ash, in which fly ash is first mixed with concentrated sulfuric acid and roasted to obtain roasted slag, and then the roasted slag is mixed with water and heated and stirred at normal pressure to leach lithium. Patent CN 102923743 A reports a process for comprehensive extraction of aluminum and lithium from fly ash by acid treatment, in which lithium is extracted through desiliconization, magnetic separation, heat treatment with sodium sulfate at 650°C to 1050°C, pressurized acidification roasting with concentrated sulfuric acid, and sulfuric acid leaching. Patent CN 109777960 B reports a method for separating and recovering lithium and aluminum from fly ash, in which fly ash is mixed with sodium carbonate, calcium oxide, calcium chloride, etc. and roasted at 650°C to 900°C, and then lithium is extracted through crushing, inorganic acid cyclic acid leaching, and other steps.

[0004] In summary, the existing lithium extraction methods from lithium-containing coal resources have problems such as complex processes, high costs, and environmental pollution. Therefore, the present invention proposes a method for extracting lithium from lithium-containing coal resources without roasting, low cost, green and environmentally friendly, with simple processes and high efficiency. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is that the calculation accuracy disclosed in the prior art is weak, and the integral is unstable due to the polar convergence of the high-resolution global model. Therefore, a method using supercritical CO 2 A method for recovering lithium from lithium-bearing coal-bearing rocks by fluid disposal.

[0006] To achieve the above object, the present invention provides a method of using supercritical CO 2 The method for recovering lithium from lithium-containing coal-bearing rocks by fluid treatment specifically comprises the following steps:

[0007] The present invention comprises the following steps:

[0008] Step A: grinding and screening the ore sample;

[0009] Step B: In supercritical CO 2 Adding industrial soft water with a L / S ratio of 0.5 to 1.5 into a fluid extraction device to form an aqueous solution system, and adding the ground ore sample and a pressure leaching aid into the aqueous solution system for extraction;

[0010] Step C: After the extraction process, a solid-liquid separation operation is performed to separate and obtain a press-leached lithium solution;

[0011] Step D: reducing the pressure of the lithium leaching solution to make the supercritical CO 2 Fluid is converted into gas, CO is recovered and separated 2 Finally, a concentrated lithium pressure leaching solution is obtained.

[0012] Furthermore, the mesh size of the grinding and screening process is 150-300 meshes.

[0013] Furthermore, the press immersion aid includes one or more of ethanol, acetone, and ethyl acetate, and the addition ratio of the press immersion aid to the ore sample particles is 0.2-2%.

[0014] Furthermore, the extraction condition control parameter is to set CO 2 The flow rate is 40-50mL / min, the temperature is controlled at 50-100℃, the pressure is 15-40MPa, and the extraction time is 0.5-4h. 2 The fluid comes into contact with the lithium more easily and dissolves it, with the lithium primarily going into the liquid.

[0015] Further, the CO separated in step D 2 Return the supercritical CO from step B 2 The fluid extraction device is recycled.

[0016] Furthermore, after the solid-liquid separation operation, preliminary separation slag and pressure leaching lithium solution are obtained, and the preliminary separation slag can be used as auxiliary building materials.

[0017] Using the above scheme, the present invention discloses a method using supercritical CO 2 The method of recovering lithium from lithium-bearing coal-bearing rocks by fluid disposal has the following advantages:

[0018] 1. The present invention firstly crushes the lithium-containing coal-based rock appropriately to increase the 2 The contact surface area, under supercritical conditions, CO 2 It has similar diffusivity to gas and solubility to liquid, and its heat transfer and diffusion properties are better than those of conventional fluids. It can quickly penetrate into the micropores of coal-bearing rocks. With the help of additives, it can efficiently dissolve lithium and separate lithium from rocks.

[0019] 2. The lithium-rich liquid is decompressed to convert supercritical CO 2 Restore to normal gas to achieve separation of lithium, CO 2 Gas recovery and recycling is economical.

[0020] 3. Supercritical CO 2 As a non-toxic, colorless and odorless fluid, it will not produce harmful residues during the entire treatment process, which meets the requirements of green chemistry. The entire process is simple, and no large amount of wastewater and waste residue will be produced during the lithium extraction process, which reduces pollution to the environment and reduces production costs. It has the advantages of simple process and green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a method of using supercritical CO 2 Overall flow chart of the method for recovering lithium from lithium-bearing coal-bearing rocks by fluid disposal; DETAILED DESCRIPTION

[0022] The following describes the embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, which are exemplary descriptions, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0023] Example 1

[0024] A supercritical CO 2 Methods for recovering lithium from lithium-bearing coal-bearing rocks by fluid disposal, see Figure 1 , comprising the following steps:

[0025] Take 1kg of lithium-containing coal rock, the lithium oxide content is 0.08%.

[0026] Step 1: Grinding and Screening

[0027] The lithium-containing coal-based rock is ground and then passed through a 150-mesh sieve to obtain ore sample particles of appropriate particle size.

[0028] Step 2: Supercritical Extraction Stage

[0029] In supercritical CO 2 Add 1L of industrial soft water to the fluid extraction device, place the ground ore sample in it, and add ethanol as an auxiliary agent at a ratio of 0.2%. Set the temperature to 50°C, the pressure to 40.0Mpa, and the CO 2 The flow rate was 40 mL / min and the extraction time was 4 h. With the assistance of the aqueous solution system, lithium was more efficiently dissolved in supercritical CO 2 fluid and enters the liquid portion.

[0030] Step 3: Solid-liquid separation

[0031] After the extraction is completed, solid-liquid separation is carried out to obtain high-pressure lithium leaching solution, and the residue is used for storage, landfill or as building materials in accordance with relevant environmental protection and resource utilization requirements.

[0032] Step 4: Lithium recovery and CO2 gas circulation

[0033] Reduce the pressure to 1Mpa, supercritical CO 2 Fluid turns into gas, CO is recovered 2 The gas is recycled. At the same time, the pressure leaching lithium solution is purified to recover the lithium element. After testing the lithium content of the leaching residue, the lithium recovery rate is calculated to be 73.8%. Part of the water is recycled for the next extraction process, saving resources and reducing production costs.

[0034] Example 2

[0035] Take 1kg of lithium-containing coal rock, the lithium oxide content is 2.5%.

[0036] Step 1: Grinding and Screening

[0037] The lithium-containing coal-based rock is ground and then passed through a 300-mesh sieve to obtain ore sample particles of appropriate particle size.

[0038] Step 2: Supercritical Extraction Stage

[0039] In supercritical CO 2 Add 1.5L of industrial soft water to the fluid extraction device, place the ground ore sample in it, and add ethyl acetate as an auxiliary agent at a ratio of 1.0%. Set the extraction temperature to 100°C, the pressure to 15.1Mpa, and the CO 2 The flow rate was 50 mL per minute and the extraction time was 0.5 hours. With the assistance of the aqueous solution system, lithium was more efficiently dissolved in supercritical CO 2 fluid and enters the liquid portion.

[0040] Step 3: Solid-liquid separation

[0041] After the extraction is completed, solid-liquid separation is carried out to obtain high-pressure lithium leaching solution, and the residue is used for storage, landfill or as building materials in accordance with relevant environmental protection and resource utilization requirements.

[0042] Step 4: Lithium Recovery and CO 2 Gas circulation

[0043] The pressure is reduced to 2.8Mpa, supercritical CO 2 The fluid is converted into gaseous state, CO2 gas is recovered and recycled. At the same time, the pressure leaching lithium solution is purified to recover lithium elements. After testing the lithium oxide content of the leaching residue, the lithium recovery rate is calculated to be 82.5%. Part of the water is recycled for the next extraction process, saving resources and reducing production costs.

[0044] Example 3

[0045] Take 1kg of lithium-containing coal rock, the lithium oxide content is 1.5%.

[0046] Step 1: Grinding and Screening

[0047] The lithium-containing coal-based rock is ground and then passed through a 200-mesh sieve to obtain ore sample particles of appropriate particle size.

[0048] Step 2: Supercritical Extraction Stage

[0049] In supercritical CO 2 Add 0.8L of industrial soft water to the fluid extraction device, place the ground ore sample in it, and add the auxiliary agent propanol at a ratio of 0.8%. Set the extraction temperature to 100℃, CO 2 The flow rate is 40 mL per minute, the pressure is 20.8 MPa, and the extraction time is 3.0 hours. With the assistance of the aqueous solution system, lithium is more efficiently dissolved in supercritical CO 2 fluid and enters the liquid portion.

[0050] Step 3: Solid-liquid separation

[0051] After the extraction is completed, solid-liquid separation is carried out to obtain high-pressure lithium leaching solution, and the residue is used for storage, landfill or as building materials in accordance with relevant environmental protection and resource utilization requirements.

[0052] Step 4: Lithium recovery and CO2 gas circulation

[0053] The pressure is reduced to 1.2Mpa, supercritical CO 2 Fluid turns into gas, CO is recovered 2 The gas is recycled. At the same time, the pressure leaching lithium solution is purified to recover lithium elements. After testing the lithium oxide content of the leaching residue, the lithium recovery rate is calculated to be 76.2%. Part of the water is recycled for the next extraction process, saving resources and reducing production costs.

[0054] The main difference between Comparative Example 1 and Example 1 using the same lithium ore as Example 1 is that no supercritical extraction step is performed;

[0055] Comparative Example 2 uses the same lithium ore as Example 2 and the main difference from Example 4 is that the chemical dissociation and strong acid leaching steps are combined;

[0056] Comparative Example 3 uses the same lithium ore as Example 3. The main difference between this example and Example 4 is that the supercritical extraction is replaced by a filtration step;

[0057] The present invention measures the conversion rate of lithium carbonate in the hydrogenated liquid obtained by the hydrogenation method of Examples 1-3 and Comparative Examples 1-2, and measures the yield and purity of high-purity lithium carbonate obtained by purification of Examples 4-6 and Comparative Examples 1-2.

[0058] Among them, the mass of lithium carbonate is determined by acid-base titration, the conversion rate of lithium carbonate in the hydrogenated solution (%) = (the mass of lithium carbonate in the pressure-leached lithium solution - the mass of lithium carbonate in the concentrated pressure-leached lithium solution) / the mass of lithium carbonate in the pressure-leached lithium solution, the yield of high-purity lithium carbonate (%) = the mass of lithium carbonate in high-purity lithium carbonate / the mass of lithium carbonate in the pressure-leached lithium solution, the purity (%) = the mass of lithium carbonate in high-purity lithium carbonate / the mass of high-purity lithium carbonate. For the convenience of comparison, the applicant organizes the main data involved in the above embodiments and comparative examples into the following table:

[0059]

[0060] Table 2 Corresponding conversion rate, yield and purity in Examples 1-3 and Comparative Examples 1-3

[0061]

[0062]

[0063] Supercritical extraction is usually used to efficiently extract the target component. Omitting this step may result in a decrease in lithium extraction efficiency because other extraction methods may not be able to penetrate and dissolve the target component in the lithium ore as effectively as supercritical extraction. The comparative example replaced supercritical extraction with a filtration step, which is usually used to remove suspended matter or impurities rather than to extract the target component. Therefore, replacing supercritical extraction with a filtration step may result in a significant decrease in lithium extraction efficiency because filtration cannot extract the target component in the lithium ore as effectively as supercritical extraction.

[0064] Through the above multiple implementation plans, it can be proved that the process of the present invention has good stability and repeatability, and can effectively extract lithium metal from lithium-containing coal-bearing rocks.

[0065] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for recovering lithium from lithium-containing coal-based rocks using supercritical CO2 fluid, characterized in that: The following steps are involved: Step A: Grinding and screening the ore sample; Step B: adding industrial soft water with L / S of 0.5-1.5 into a supercritical CO2 fluid extraction device to form an aqueous solution system, and adding the ground ore sample and a pressure leaching aid into the aqueous solution system for extraction; Step C: After the extraction process, a solid-liquid separation operation is performed to separate and obtain a press-leached lithium solution; Step D reduces the pressure of the lithium leaching solution to convert the supercritical CO2 fluid into a gaseous state, and recovers and separates the CO2 to obtain a concentrated lithium leaching solution; The press leaching aid includes one or more of ethanol, acetone, and ethyl acetate, and the addition ratio of the press leaching aid to the ore sample particles is 0.2-2%; The extraction condition control parameters are to set the CO2 flow rate to 40-50mL / min, control the temperature to 50-100°C, the pressure to 15-40MPa, and the extraction time to 0.5-4h.

2. A method for recovering lithium from lithium-containing coal-bearing rocks using supercritical CO2 fluid treatment according to claim 1, characterized in that: The mesh number of the grinding and screening process is 150-300 meshes.

3. A method for recovering lithium from lithium-containing coal-bearing rocks using supercritical CO2 fluid treatment according to claim 1, characterized in that: The CO2 separated in step D is returned to the supercritical CO2 fluid extraction device in step B for recycling.

4. A method for recovering lithium from lithium-containing coal-bearing rocks using supercritical CO2 fluid treatment according to claim 1, characterized in that: After the solid-liquid separation operation, preliminary separation slag and pressure leaching lithium solution are obtained, and the preliminary separation slag can be used as auxiliary building materials.

Images