Method for extracting lithium sulfate from high-iron spodumene concentrate

Abstract

The invention discloses a method for extracting lithium sulfate from high-iron spodumene concentrate, which comprises the following steps: mixing high-iron spodumene concentrate, sulfate and carbonate, and processing to obtain powder; the mass ratio of the high-iron spodumene concentrate to the sulfate to the carbonate is 1: (0.3-0.8): (0.01-0.5); the powder is subjected to brick pressing forming, a powder green brick is obtained, and the powder green brick is dried and roasted at the temperature of 900-1050 DEG C; cooling and crushing the roasted powder green brick to obtain a roasted particle material; adding water into the roasted particle material, carrying out ball milling, and leaching to obtain a leaching solution and leaching residues; and carrying out purification and concentration treatment on the leachate to obtain the lithium sulfate. By implementing the method, the interference of iron impurities can be eliminated, and the cost is reduced while the lithium recovery rate is improved.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, and in particular to a method for extracting lithium sulfate from high-iron spodumene concentrate. Background Technology

[0002] The main mineral raw materials for lithium production include spodumene, lepidolite, petalite, and phosphogypsum. Lithium can be extracted from high-iron spodumene concentrate after high-temperature roasting and activation. To ensure complete spodumene conversion, roasting temperatures typically exceed 1100℃, resulting in high energy consumption, low lithium conversion rates, and interference from iron impurities. Particularly during roasting, iron may react with lithium to form low-melting-point compounds, reducing lithium extraction efficiency. Iron oxides at high temperatures may also react with other components in spodumene, complicating reaction pathways and affecting process controllability. Furthermore, the presence of iron can affect the physical properties of the ore, reducing its reactivity and thus impacting lithium phase transitions, leaching, and purification processes. Iron, as an impurity in lithium salts, also affects the purity of the final product, requiring additional steps to remove iron impurities in subsequent purification processes, increasing production costs and complexity. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for extracting lithium sulfate from high-iron spodumene concentrate, which eliminates the interference of iron impurities, improves the lithium recovery rate and reduces costs.

[0004] To address the aforementioned problems, this invention discloses a method for extracting lithium sulfate from high-iron spodumene concentrate, comprising the following steps:

[0005] High-iron spodumene concentrate, sulfate, and carbonate are mixed and processed to obtain powder; the mass ratio of high-iron spodumene concentrate, sulfate, and carbonate is 1:(0.3~0.8):(0.01~0.5).

[0006] The powder is pressed into bricks to obtain powder brick blanks, which are then dried and fired at a temperature of 900℃~1050℃.

[0007] The calcined powder brick blanks are cooled and crushed to obtain calcined granular materials.

[0008] The roasted granular material is ball-milled with water and then leached to obtain leachate and leaching residue.

[0009] The leachate is purified and concentrated to obtain lithium sulfate.

[0010] As an improvement to the above technical solution, the process of mixing high-iron spodumene concentrate, sulfate and carbonate to obtain powder includes: mixing high-iron spodumene concentrate, sulfate and carbonate, and preparing slurry by wet ball milling, wherein the residue of the slurry on a 180-220 mesh sieve is 5%-15%.

[0011] The slurry is spray-dried into powder, and the moisture content of the powder is 3% to 8%.

[0012] As an improvement to the above technical solution, the Fe content in the high-iron spodumene concentrate is 12% to 18%.

[0013] As an improvement to the above technical solution, the sulfate is one or more of sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, ferric sulfate, and aluminum sulfate, and the carbonate is one or more of sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, and sodium bicarbonate.

[0014] As an improvement to the above technical solution, the sulfate is sodium sulfate and calcium sulfate, and the carbonate is calcium carbonate;

[0015] The mass ratio of the high-iron spodumene concentrate, sodium sulfate, calcium sulfate and calcium carbonate is 1:(0.15~0.4):(0.2~0.3):(0.05~0.1).

[0016] As an improvement to the above technical solution, the calcination temperature is 960℃~1020℃, and the calcination holding time is 60min~120min.

[0017] As an improvement to the above technical solution, the calcination heating process is as follows:

[0018] Increase the temperature to 200℃ to 500℃ at a rate of 2℃ / min to 5℃ / min, and hold for 5min to 10min;

[0019] Heat to 500℃~800℃ at a rate of 5℃ / min~8℃ / min, and hold for 5min~10min;

[0020] Heat to 800℃~960℃ at a rate of 3℃ / min~5℃ / min, and hold for 5min~10min;

[0021] Heat to 960℃~1020℃ at a rate of 2℃ / min~5℃ / min, and hold for 60min~120min.

[0022] As an improvement to the above technical solution, the residue on a 60-100 mesh sieve of the roasted granular material is 5%-15%.

[0023] As an improvement to the above technical solution, in the step of adding water to the roasted granular material for ball milling, leaching, and obtaining leachate and leachate residue, the leaching temperature is 40℃~70℃, the leaching time is 30min~120min, and the liquid-solid ratio is 1:(1~10).

[0024] As an improvement to the above technical solution, one or more of the following methods—chemical precipitation, ion exchange, and adsorption—are used to purify the leachate.

[0025] Implementing this invention has the following beneficial effects:

[0026] This invention promotes ion replacement reaction, eliminates iron impurities, and lowers roasting temperature through the synergistic effect of high-iron spodumene concentrate, sulfate, and carbonate. It eliminates the need for additional pretreatment of high-iron spodumene concentrate to remove iron impurities, and the process is simple. Combined with subsequent leaching, purification, and concentration, the lithium conversion rate reaches over 84%, providing an industrially feasible path for the cost-effective development of high-iron lithium mines. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0028] This invention provides a method for extracting lithium sulfate from high-iron spodumene concentrate, comprising the following steps:

[0029] S1. Mix high-iron spodumene concentrate, sulfate and carbonate, and process to obtain powder.

[0030] The mass ratio of the high-iron spodumene concentrate, sulfate, and carbonate is 1:(0.3-0.8):(0.01-0.5). Under the action of sulfate and carbonate, the ion replacement reaction is promoted and the roasting temperature is reduced.

[0031] In one implementation, it specifically includes:

[0032] S11. Mix high-iron spodumene concentrate, sulfate and carbonate, and prepare a slurry by wet ball milling.

[0033] S12. The slurry is spray-dried into powder.

[0034] Pretreatment of high-iron spodumene concentrate by ball milling and spray drying before roasting significantly optimizes the subsequent roasting effect. Ball milling ensures molecular-level contact between spodumene, sulfate, and carbonate, preventing insufficient localized reactions. Spray-dried porous microspheres facilitate heat and mass transfer during roasting, increasing the crystal transformation rate from α-spodumene to β-spodumene. Strict control of spodumene fineness and powder moisture content provides a foundation for efficient spodumene roasting. Specifically, the spodumene residue on a 180-220 mesh sieve should be 5%-15%. If the spodumene mesh size is too high, the viscosity will be high, increasing energy consumption for subsequent spray drying. Furthermore, excessively fine particles are prone to sintering and agglomeration, reducing roasting efficiency. Conversely, if the spodumene mesh size is too low, coarser particles will lead to incomplete roasting, reducing lithium recovery. Preferably, the spodumene residue on a 200 mesh sieve should be 5%-15%. Specifically, the moisture content of the powder should be 3% to 8%. If the moisture content is too low, the powder will have poor flowability and generate dust during transportation; if the moisture content is too high, the powder will splash due to moisture vaporization during roasting.

[0035] The cations in sulfate react with the lithium ions in spodumene, generating lithium as lithium sulfate. Carbonates neutralize the acidic environment, reducing equipment corrosion. The oxides obtained from the high-temperature decomposition of carbonates can also react with impurities such as Fe₂O₃ and Al₂O₃, reducing dissolution during leaching and lowering the difficulty of subsequent purification. If the mass ratio of sulfate and carbonate is too low, it is insufficient to completely convert α-spodumene to β-spodumene, resulting in a low lithium conversion rate. If the mass ratio of sulfate and carbonate is too high, excess sulfate may react with aluminum, iron, etc., to form soluble sulfates, increasing the concentration of impurities in the leachate and making purification more difficult.

[0036] Specifically, the sulfate is one or more of sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, ferric sulfate, and aluminum sulfate, and the carbonate is one or more of sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, and sodium bicarbonate.

[0037] In a preferred embodiment, the sulfate is sodium sulfate and calcium sulfate, and the carbonate is calcium carbonate. Sodium sulfate can react with iron to form soluble sodium ferrite, preventing lithium encapsulation. During subsequent leaching, the sodium ferrite can react with Li. + Simultaneous entry into the solution prevents Fe2O3 from encapsulating spodumene particles and causing lithium residue. Sodium sulfate can also form eutectic compounds with SiO2 and Al2O3 in high-iron spodumene concentrate, reducing the liquid-phase sintering and agglomeration of Fe2O3 at high temperatures, maintaining particle porosity, and lowering the calcination temperature. Calcium sulfate can react with iron to form stable calcium-iron oxides in acid, reducing Fe in the leachate. 3+ Concentration, reducing the burden on subsequent purification; the CaO product of high-temperature decomposition of calcium sulfate can react with SiO2 to form porous calcium silicate, promoting lithium diffusion. The CaO product of high-temperature decomposition of calcium carbonate preferentially combines with Fe2O3 to form an inert calcium-iron phase, preventing Fe...3+ With SO4 2- The reaction is carried out in the following manner. Specifically, the mass ratio of the high-iron spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:(0.15-0.4):(0.2-0.3):(0.05-0.1), with exemplary ratios of 1:0.15:0.3:0.05, 1:0.4:0.2:0.05, 1:0.2:0.25:0.08, 1:0.2:0.2:0.05, or 1:0.3:0.2:0.1, but not limited to these. Controlling the mass ratio of the high-iron spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate within the above range can improve reaction efficiency and lithium conversion rate while strictly controlling iron impurities in the high-iron spodumene concentrate, reducing the difficulty of subsequent impurity removal.

[0038] S2. Press the powder into bricks to obtain powder brick blanks, dry the powder brick blanks and fire them at a temperature of 900℃~1050℃.

[0039] Specifically, the powder is pressed into bricks, and the formed powder brick blanks are directly sent to a drying kiln to remove moisture. After exiting the drying kiln, they are sent to a roller kiln for firing. The drying temperature is 80℃~200℃, and the drying time is 2h~5h, which can be adjusted according to the thickness of the powder brick blanks during actual production. The firing temperature is 900℃~1050℃, which consumes less energy compared to conventional high-temperature firing (firing temperature ≥1100℃). In a preferred embodiment, the firing temperature is 960℃~1020℃, and the firing holding time is 60min~120min.

[0040] A better roasting temperature rise procedure is as follows:

[0041] Heat the material to 200℃~500℃ at a rate of 2℃ / min~5℃ / min, and hold for 5min~10min to avoid cracking of the powder brick blank due to steam pressure.

[0042] The temperature is increased to 500℃~800℃ at a rate of 5℃ / min~8℃ / min and held for 5min~10min to achieve the initial transformation to the β phase and quickly pass through the unstable range of α-spodumene (700℃~750℃) to prevent lattice stress cracking.

[0043] The temperature is increased to 800℃~960℃ at a rate of 3℃ / min~5℃ / min, and held for 5min~10min to complete the phase transformation and generate β-spodumene;

[0044] Heating to 960℃~1020℃ at a rate of 2℃ / min~5℃ / min and holding for 60min~120min promotes particle bonding, reduces porosity, and increases density.

[0045] By segmented temperature control and precise heat preservation, energy consumption and product performance are optimized while ensuring complete phase change.

[0046] S3. Cool and crush the calcined powder brick blank to obtain calcined granular material.

[0047] The powdered brick blanks emerge from the kiln intact after firing and can be cooled by natural cooling or water cooling. In one embodiment, the temperature is lowered to room temperature at a rate of 4°C / min to 8°C / min to suppress β-phase reversal and prevent cooling cracks. The cooled material is relatively loose, and the lithium has been largely converted into soluble lithium sulfate. It is then crushed into particles of a certain size using a crushing device for subsequent leaching operations. In one embodiment, the residue on a 60-100 mesh sieve of the calcined granular material is 5% to 15%, and the coarser particles reduce the filtration pressure of the leaching residue. Preferably, the residue on a 100 mesh sieve of the calcined granular material is 5% to 15%.

[0048] S4. The roasted granular material is ball-milled with water and leached to obtain leachate and leachate residue.

[0049] During the leaching process, lithium sulfate dissolves into the solution, while other insoluble substances form leaching residue. In one embodiment, the leaching temperature is 40°C to 70°C, the leaching time is 30 min to 120 min, and the liquid-to-solid ratio is 1:(1 to 10).

[0050] S5. The leachate is purified and concentrated to obtain lithium sulfate.

[0051] After leaching, the leachate and leaching residue are separated using filtration equipment. The leachate contains soluble substances such as lithium sulfate, while the leaching residue mainly consists of insoluble silicates, aluminates, and other impurities. After separation, the leachate can be purified using one or more of the following methods: chemical precipitation, ion exchange, and adsorption, to remove impurity ions such as iron, aluminum, calcium, and magnesium. The purified leachate contains a certain concentration of lithium sulfate. To obtain a high-purity lithium sulfate solution, the solution is concentrated by evaporation to remove water and increase the lithium sulfate concentration.

[0052] The present invention will be further described below with reference to specific embodiments:

[0053] Example 1

[0054] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate, including the following steps:

[0055] S1. Mix high-iron spodumene concentrate, sodium sulfate, calcium sulfate and calcium carbonate, and process to obtain powder.

[0056] The mass ratio of high-iron spodumene concentrate, sodium sulfate, calcium sulfate and calcium carbonate is 1:0.4:0.2:0.1.

[0057] S2. Press the powder into bricks to obtain powder brick blanks. Dry the powder brick blanks and fire them at 1020℃ for 120 minutes. The heating rate is 5℃ / min.

[0058] S3. Crush the calcined powder brick blanks to obtain calcined granular material.

[0059] S4. Add water to the roasted granular material, ball mill it, and leach it to obtain leachate and leach residue.

[0060] S5. The leachate is purified and concentrated to obtain lithium sulfate.

[0061] Example 2

[0062] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate. The difference between this method and Example 1 is that the roasting temperature is 980℃ and the roasting holding time is 90 min. All other aspects are the same as in Example 1.

[0063] Example 3

[0064] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate. The difference between this method and Example 1 is that the roasting temperature is 980℃ and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0065] Example 4

[0066] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of high-iron spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.3:0.2:0.1, the roasting temperature is 1020℃, and the roasting holding time is 90 min. All other aspects are the same as in Example 1.

[0067] Example 5

[0068] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.3:0.2:0.1, the roasting temperature is 980℃, and the roasting holding time is 90 min. All other aspects are the same as in Example 1.

[0069] Example 6

[0070] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of high-iron spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.3:0.2:0.1, the roasting temperature is 960℃, and the roasting holding time is 90 min. All other aspects are the same as in Example 1.

[0071] Example 7

[0072] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of high-iron spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.2:0.2:0.05, the roasting temperature is 1020℃, and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0073] Example 8

[0074] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.2:0.2:0.05, the roasting temperature is 980℃, and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0075] Example 9

[0076] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of high-iron spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.2:0.2:0.05, the roasting temperature is 960℃, and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0077] Example 10

[0078] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.15:0.25:0.05, the roasting temperature is 1020℃, and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0079] Example 11

[0080] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.15:0.25:0.05, the roasting temperature is 980℃, and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0081] Example 12

[0082] This embodiment provides a method for extracting lithium sulfate from spodumene concentrate. The difference between this method and Example 1 is that the mass ratio of spodumene concentrate, sodium sulfate, calcium sulfate, and calcium carbonate is 1:0.15:0.25:0.05, the roasting temperature is 960℃, and the roasting holding time is 60 min. All other aspects are the same as in Example 1.

[0083] Example 13

[0084] This embodiment provides a method for extracting lithium sulfate from high-iron spodumene concentrate, which differs from Example 8 in that the roasting temperature procedure is as follows:

[0085] Heat to 400℃ at a rate of 4℃ / min and hold for 10 min;

[0086] Heat to 800℃ at a rate of 8℃ / min and hold for 10 min;

[0087] Heat to 900℃ at a rate of 5℃ / min and hold for 10 min;

[0088] Heat to 980℃ at a rate of 3℃ / min and hold for 60 min.

[0089] Everything else is the same as in Example 8.

[0090] The lithium conversion rates of Examples 1 to 13 were calculated, and the specific results are as follows:

[0091]

[0092] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for extracting lithium sulfate from high-iron spodumene concentrate, characterized in that, Includes the following steps: High-iron spodumene concentrate, sulfate, and carbonate are mixed and processed to obtain powder; the mass ratio of high-iron spodumene concentrate, sulfate, and carbonate is 1:(0.3~0.8):(0.01~0.5). The powder is pressed into bricks to obtain powder brick blanks, which are then dried and fired at a temperature of 900℃~1050℃. The calcined powder brick blanks are cooled and crushed to obtain calcined granular materials. The roasted granular material is ball-milled with water and then leached to obtain leachate and leaching residue. The leachate is purified and concentrated to obtain lithium sulfate.

2. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, The process of mixing high-iron spodumene concentrate, sulfate, and carbonate to obtain powder includes: High-iron spodumene concentrate, sulfate and carbonate are mixed and pulped by wet ball milling. The residue of the pulp on a 180-220 mesh sieve is 5%-15%. The slurry is spray-dried into powder, and the moisture content of the powder is 3% to 8%.

3. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, The Fe content in the high-iron spodumene concentrate is 12% to 18%.

4. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, The sulfate is one or more of sodium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, ferric sulfate, and aluminum sulfate, and the carbonate is one or more of sodium carbonate, potassium carbonate, calcium carbonate, magnesium carbonate, and sodium bicarbonate.

5. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 4, characterized in that, The sulfate is sodium sulfate and calcium sulfate, and the carbonate is calcium carbonate; The mass ratio of the high-iron spodumene concentrate, sodium sulfate, calcium sulfate and calcium carbonate is 1:(0.15~0.4):(0.2~0.3):(0.05~0.1).

6. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, The calcination temperature is 960℃~1020℃, and the calcination holding time is 60min~120min.

7. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 6, characterized in that, The roasting and heating process is as follows: Increase the temperature to 200℃ to 500℃ at a rate of 2℃ / min to 5℃ / min, and hold for 5min to 10min; Heat to 500℃~800℃ at a rate of 5℃ / min~8℃ / min, and hold for 5min~10min; Heat to 800℃~960℃ at a rate of 3℃ / min~5℃ / min, and hold for 5min~10min; Heat to 960℃~1020℃ at a rate of 2℃ / min~5℃ / min, and hold for 60min~120min.

8. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, The residue on a 60-100 mesh sieve of the roasted granular material is 5%-15%.

9. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, In the step of adding water to the roasted granular material, ball milling, leaching, and obtaining leachate and leaching residue, the leaching temperature is 40℃~70℃, the leaching time is 30min~120min, and the liquid-solid ratio is 1:(1~10).

10. The method for extracting lithium sulfate from high-iron spodumene concentrate as described in claim 1, characterized in that, The leachate is purified by one or more of the following methods: chemical precipitation, ion exchange, and adsorption.

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