Wet-process continuous lithium extraction method for zero-carbon spodumene concentrate

Abstract

The invention discloses a zero-carbon spodumene concentrate wet continuous lithium extraction method which comprises the following steps: adding water and fluorite into spodumene concentrate, grinding together to obtain raw slurry, adding inorganic acid and a complexing agent into the slurry, uniformly mixing to obtain raw slurry, adding the raw slurry into a column pressure reactor, reacting to obtain leached slurry, and separating the leached slurry from the leached slurry to obtain the zero-carbon spodumene concentrate. And adding a surface modifier into the leaching slurry, uniformly mixing, and carrying out solid-liquid separation to obtain a lithium-containing solution and leaching residues. The method has the advantages of being short in process, high in leaching efficiency, low in cost and environmentally friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrometallurgy, in particular to a zero-carbon lithium spodumene concentrate wet continuous lithium extraction method. BACKGROUND

[0002] Lithium is the first metal element in the periodic table of chemical elements, and is widely used in lithium batteries, glass and ceramics, and atomic energy industry. Lithium resources are divided into brine type and ore type, among which ore lithium mainly includes spodumene, lepidolite, eucolite and petalite.

[0003] Spodumene is the largest lithium ore resource, and is the main source of lithium extraction from ore. Spodumene (LiAlSi2O6) is a chain silicate mineral, and the theoretical content of Li2O is 8.03%, but due to partial replacement of lithium by sodium and potassium, the content of Li2O is usually 6-7.5%. Spodumene often occurs with quartz and feldspar and other gangue minerals to form pegmatite spodumene ore, and the content of Li2O in the ore is 1-4%, and the content of Li2O in the concentrate obtained by beneficiation can be more than 5%. The key to extracting lithium from spodumene is to destroy the structure of aluminum silicate. Naturally occurring α-spodumene needs to be calcined at 1000℃ to convert to β-roasted spodumene, and then decomposed with acid, which greatly increases energy consumption and environmental pollution. In addition to lithium, aluminum and silicon elements, spodumene ore also contains impurity elements such as calcium, iron and potassium, and separate utilization of these elements is beneficial to maximizing resource efficiency.

[0004] Hydrofluoric acid can destroy the crystal structure of α-spodumene, and the use of a mixture of hydrofluoric acid and sulfuric acid can strengthen the leaching of lithium in α-spodumene. When the ore / HF / H2SO4 ratio is 1:3:2 g:mL:mL, the leaching temperature and time are 100℃ and 3 hours respectively, the leaching rate of lithium is 96%, and the leaching residue contains lithium cryolite (Na3Li2Al2F 12), cryolite (Na3AlF6), calcium fluoride (CaF2), potassium cryolite (K2AlF5), aluminum fluoride (AlF3), and fluorosilicate (Na2SiF6 or KNaSiF6) [Guo H, Yu H, Zhou A, et al. Kinetics of leaching lithium from omspodumene in enhanced acid treatment using HF / H2SO4 as medium [J]. Transactions of Nonferrous Metals Society of China, 2019, 29: 407-415]. But the cost of hydrofluoric acid is high, to reduce the cost, calcium fluoride can be used to replace hydrofluoric acid, the leaching temperature and time are 100℃ and 24 hours respectively, but the lithium leaching rate is less than 5% [Griffith C S, Griffin A C, Roper A. Development of a novel process for the extraction of lithium silicate minerals [M]. The Minerals, Metals & Materials Series, 2018: 2235-2245. technology for the extraction oflithium silicate minerals[M].The Minerals,Metals & Materials Series,2018:2235-2245. https: / / doi.org / 10.1038 / s41598-017-07474- 10.1007 / 978-3-319-95022-8_188]。

[0005] In order to reduce the cost, improve the lithium leaching rate and production efficiency, a new technology for extracting lithium from lithium spodumene concentrate in the whole process is developed, which is a way to realize the sustainable development of lithium resource development. SUMMARY

[0006] In order to solve the problems existing in the prior art, the present application provides a zero-carbon lithium spodumene concentrate wet continuous lithium extraction method, compared with the prior art, the method has the characteristics of short process, high leaching efficiency, low cost and green environmental protection, and has significant economic and social benefits.

[0007] A zero-carbon lithium spodumene concentrate wet continuous lithium extraction method, comprising the following steps in sequence:

[0008] The raw material slurry is obtained by adding water and fluorite to the spodumene concentrate and co-milling, the raw slurry is obtained by adding inorganic acid and complexing agent and mixing uniformly, the leaching slurry is obtained by adding the raw slurry into a column pressure reactor for reaction, and the lithium-containing solution and leaching residue are obtained by mixing the leaching slurry with a surface modifier uniformly and then performing solid-liquid separation; wherein the inorganic acid is one of sulfuric acid and nitric acid; the complexing agent is one of chitosan, ethylenediaminetetraacetic acid and citric acid; the surface modifier is one of polycarboxylic acid, sulfonated melamine formaldehyde resin and naphthalene sulfonate formaldehyde condensate; the column pressure reactor is composed of a pressurized column, a pipeline reaction kettle and a pipeline cooling kettle, and the column pressure reactor uses one of photovoltaic power and wind power as electric energy.

[0009] The water is added in an amount of 300-2000% of the mass of the spodumene concentrate.

[0010] The fluorite is added in an amount of 0.5-5.0% of the mass of the spodumene concentrate.

[0011] The inorganic acid is added in an amount of 200-500% of the mass of the spodumene concentrate.

[0012] The complexing agent is added in an amount of 0.1-2.0% of the mass of the spodumene concentrate.

[0013] The reaction temperature in the pipeline reaction kettle is 180-260 DEG C, and the residence time of the material in the pipeline reaction kettle is 2-8 hours.

[0014] The surface modifier is added in an amount of 0.1-2.0% of the mass of the spodumene concentrate.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] The water and fluorite are added to the spodumene concentrate and co-milled, the mill used is one of a stirring mill and a vibration ball mill, the grinding medium is an alumina ceramic ball, the alumina ceramic ball is toughened by 5-20 wt% of zirconium oxide, has the characteristics of low cost, good toughness, high strength, wear resistance and no reaction with calcium fluoride, and the lining material of the mill is one of alumina, polytetrafluoroethylene and polyurethane, has the characteristic of wear resistance, and all can achieve the purpose of the application. After milling, the particle size of the material is 5-20 microns, the material particles are small, which is beneficial to shorten the reaction time and improve the reaction efficiency.

[0017] The main component of fluorite is calcium fluoride (CaF2), which acts as a catalyst in the reaction system and is easy to react with inorganic acid to generate hydrogen fluoride under high temperature conditions, that is, to release fluoride ions, and the fluoride ions in the solution decompose the crystal structure of alpha spodumene, which is beneficial to the reaction of inorganic acid with spodumene to extract lithium; in a low-temperature and low-acid environment, fluoride ions combine with calcium to crystallize into calcium fluoride and precipitate. The calcium fluoride and fluorosilicic acid produced in the phosphating industry are added in an amount of 0.5-5.0% of the mass of the spodumene concentrate, and all have the same effect.

[0018] The inorganic acid is one of sulfuric acid and nitric acid. The sulfuric acid is a by-product of pyrometallurgical process, which has the characteristics of low cost, and the concentration is 80-98%. The amount of sulfuric acid and nitric acid added in the claim is calculated based on the content of H2SO4 and HNO3.

[0019] The complexing agent is one of tartaric acid, ethylenediaminetetraacetic acid, and citric acid. The complexing agent can easily form a complex with lithium ions, avoiding the generation of lithium ice and improving the extraction rate of lithium by 3-10%.

[0020] The column pressure reactor is composed of a pressurized column, a pipeline reaction kettle, and a pipeline cooling kettle, which are connected through flanges. The electric energy used in the column pressure reactor is green electricity, which is one of photovoltaic and wind power, and both can achieve the purpose.

[0021] The pressurized column is composed of a hollow cylinder, a pressure relief valve, and a feeding valve. The feeding valve is a one-way valve, also known as a check valve or non-return valve, which prevents the reverse flow of slurry. The column height is 10-400 meters, which can be selected according to the design requirements. The pressure is transmitted to the pipeline reaction kettle by using the weight of the slurry and the pressure of the slurry pump. The higher the column, the greater the weight of the slurry, and the simpler the system control. The intelligent control system is used to adjust the pressure of the slurry pump to ensure that the pressure generated by the pressurized column is balanced with the saturated steam pressure in the pipeline reaction kettle, and the temperature of the reaction kettle is stable. The pressure relief valve is the outlet for raw slurry. When the pressure in the pressurized column exceeds the given temperature saturation steam pressure of the reaction kettle, the raw slurry is automatically discharged to the raw slurry pool, ensuring the stability of the pressure in the reaction kettle and the safety of the system, i.e., overpressure protection. The slurry pressure measurement uses one of the isolated diffusion silicon sensitive element and the ceramic capacitor pressure sensitive sensor, both of which can achieve the purpose. The system automatic control of the column pressure reactor uses the DCS control system, which has the characteristics of stable operation. The column body of the pressurized column is vertically arranged, which is beneficial to reduce the floor area.

[0022] The pipeline reaction kettle is a cylindrical hollow pipe with a neck and a flange at one end. One end is sealed and has a cylindrical hole on the upper side and is connected to the flange. The pipeline reaction kettle is equipped with a magnetic stirrer, which has the characteristics of easy sealing. The reaction kettle is equipped with a steam jacket, which is heated by steam generated by a green electricity boiler. The low-temperature steam is circulated back to the boiler. The reaction kettle can also be heated by heat-conducting oil, which can also achieve the purpose. The heat-conducting oil is heated by a green electricity resistance element. The green electricity is one of photovoltaic and wind power, both of which can achieve the purpose.

[0023] The pipeline cooling kettle is a cylindrical hollow pipeline, both ends of the pipeline have a circular necking and flange, the pipeline cooling kettle is provided with a magnetic stirrer, the stirrer has the characteristics of easy sealing. The leaching slurry flow of the discharge port of the pipeline cooling kettle is controlled by an angle valve, that is, an angular stop valve. The angle valve has the characteristics of simple flow path, small dead zone and vortex zone, and small flow resistance, and is suitable for occasions containing suspended solids and granular fluid. The opening degree of the angle valve is automatically controlled by the DCS system to ensure that the discharge amount of the angle valve and the feeding amount of the pressurized column are balanced, and the pressure and temperature in the reaction kettle are stable. The part of the angle valve in contact with the liquid is lined with ceramic material to improve the service life of the angle valve. The material of the ceramic lining is one of alumina and zirconia, which can achieve the purpose. The leaching residue and fluorite in the cooling kettle are cooled and crystallized to obtain coarse crystals, which is beneficial to the subsequent solid-liquid separation of the leaching slurry. The kettle wall of the cooling kettle is provided with a water cooling jacket to cool the leaching slurry and realize heat recovery. The temperature of the slurry discharged from the pipeline cooling kettle is 20-50℃, which avoids the difficulty in recycling water vapor and leads to heat loss.

[0024] The material of the column pressure reactor is one of carbon steel and stainless steel, which can achieve the purpose. The inner wall of the column pressure reactor is lined with polytetrafluoroethylene, which has the characteristics of high temperature resistance, wear resistance and corrosion resistance. The column pressure reactor is a continuous opening type autoclave, which avoids the characteristics of traditional steam pressure kettles that can only be produced intermittently, and can realize continuous production. The material of the stirring paddle of the magnetic stirrer is one of carbon steel and stainless steel, which can achieve the purpose. It is also wrapped with polytetrafluoroethylene for protection to prevent corrosion and prolong the service life. This column pressure reactor can also be used for pressure leaching of sulfide ores, such as zinc sulfide, nickel sulfide ore and lead sulfide ore.

[0025] The surface modifier is one of polycarboxylic acid, sulfonated melamine formaldehyde resin and naphthalene sulfonic acid formaldehyde condensate. The surface modifier is adsorbed on the surface of the leaching residue to squeeze out the adsorbed water on the surface of the leaching residue, reduce the water content of the leaching residue, and increase the recovery rate of lithium ions by 2-5%. The commonly used preparation method of polycarboxylic acid is to gradually add a mixed solution of propionic acid monomer, mercaptopropionic acid chain transfer agent and hydrogen peroxide initiator to the aqueous solution containing methoxy polyethylene glycol to react. The preparation method of sulfonated melamine formaldehyde resin is to sulfonate melamine with sulfuric acid and then condense with formaldehyde. The preparation method of naphthalene sulfonic acid formaldehyde condensate is to carry out sulfonation reaction of naphthalene with concentrated sulfuric acid, then cool and hydrolyze the reaction mixture, and then condense the sulfonated naphthalene with formaldehyde to form a high molecular compound.

[0026] After the reaction, solid-liquid separation is carried out to obtain a lithium-containing solution and leaching residue. The solid-liquid separation is carried out by using a plate and frame filter press, which has the characteristics of simple equipment and low water content of the leaching residue, and the water content is less than 13%. The lithium-containing solution is treated according to the purification method of leaching solution of lepidolite, and aluminum and iron are recovered respectively, and finally lithium carbonate product is obtained.

[0027] The fluorite in the leaching residue is recovered by flotation to obtain a defluorination residue, and the foaming agent in the flotation reagent is No. 2 oil, the depressor is acidified water glass, and one of the collectors is sodium oleate or oleic acid, which can achieve the purpose; the addition amount of different reagents in the flotation reagent is 0.01-0.05% of the mass of the spodumene concentrate, and the recovery rate of fluorite is 60-80%. The gypsum in the defluorination residue is also recovered by flotation to obtain a desulfurization residue, and the gypsum collector is dodecylamine, the foaming agent is No. 2 oil, the addition amount of different reagents in the flotation reagent is 0.01-0.05% of the mass of the spodumene concentrate, and the recovery rate of gypsum is 60-80%. The flotation device used is a flotation column, which has the characteristics of high separation efficiency and low energy consumption.

[0028] The main phase of the desulfurization residue is quartz, which can be used as a slurry admixture for concrete.

[0029] The electricity used in the production process is all green electricity, and the production electricity equipment is a stirrer, a slurry pump, a control valve, a heating device and an automatic control system; the green electricity has the characteristics of not emitting carbon dioxide and zero carbon; the green electricity storage adopts a sodium ion battery, which has the characteristics of stable power and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0030] ​ The structure schematic diagram of the column pressure reactor involved in the application is shown. DETAILED DESCRIPTION

[0031] The application will be further described in detail below in combination with specific embodiments.

[0032] The application discloses a zero-carbon lithium concentrate wet continuous lithium extraction method, which comprises the following steps: adding water and fluorite to spodumene concentrate for common grinding to obtain raw slurry, adding inorganic acid and complexing agent to the slurry and mixing uniformly to obtain green slurry, adding the green slurry into a column pressure reactor for reaction to obtain leaching slurry, adding a surface modifier into the leaching slurry and mixing uniformly, and then performing solid-liquid separation to obtain a lithium-containing solution and leaching residue. The addition amounts of water, fluorite, inorganic acid and complexing agent are shown in Table 1. The reaction temperature and time, the surface modifier and the lithium leaching rate are shown in Table 2.

[0033] Table 1

[0034]

[0035] Table 2

[0036]

[0037]

[0038] It can be concluded from Examples 1-18 that the lithium leaching rate obtained is greater than 96%. The examples of the application can be implemented and the purpose of the application can be achieved, and the application is not limited to these examples.

Claims

1. A wet continuous lithium extraction method for zero-carbon spodumene concentrate, characterized in that: The method comprises the following steps: adding water and fluorite to spodumene concentrate and grinding them together to obtain raw material slurry; adding inorganic acid and complexing agent to the slurry and mixing them evenly to obtain raw material slurry; adding the raw material slurry to a column pressure reactor for reaction to obtain leaching slurry; adding a surface modifier to the leaching slurry and mixing them evenly, and carrying out solid-liquid separation to obtain a lithium-containing solution and leaching residue; wherein the inorganic acid is one of sulfuric acid and nitric acid; the complexing agent is one of chitosan, ethylenediaminetetraacetic acid, and citric acid; the surface modifier is one of polycarboxylic acid, sulfonated melamine formaldehyde resin, and naphthalenesulfonic acid formaldehyde condensate; the column pressure reactor comprises a pressurized column, a pipeline reactor, and a pipeline cooling reactor; and the electric energy used in the column pressure reactor is one of photovoltaic power and wind power.

2. A wet continuous lithium extraction method for zero-carbon spodumene concentrate according to claim 1, characterized in that: The amount of water added is 300-2000% of the mass of the spodumene concentrate.

3. A wet continuous lithium extraction method for zero-carbon spodumene concentrate according to claim 1, characterized in that: The amount of fluorite added is 0.5-5.0% of the mass of the spodumene concentrate.

4. A wet continuous lithium extraction method for zero-carbon spodumene concentrate according to claim 1, characterized in that: The amount of the inorganic acid added is 200-500% of the mass of the spodumene concentrate.

5. A wet continuous lithium extraction method for zero-carbon spodumene concentrate according to claim 1, characterized in that: The added amount of the complexing agent is 0.1-2.0% of the mass of the spodumene concentrate.

6. A wet continuous lithium extraction method for zero-carbon spodumene concentrate according to claim 1, characterized in that: The reaction temperature in the pipeline reactor is 180-260° C., and the material stays in the pipeline reactor for 2-8 hours.

7. A wet continuous lithium extraction method for zero-carbon spodumene concentrate according to claim 1, characterized in that: The added amount of the surface modifier is 0.1-2.0% of the mass of the spodumene concentrate.

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