Method for pre-removing impurities before lithium extraction of lepidolite ore

Abstract

The invention relates to the technical field of metallurgical impurity removal, in particular to a method for pre-removing impurities before lithium extraction of lepidolite ore. According to the method for pre-removing impurities before lithium extraction of the lepidolite ore, through primary low-temperature roasting and secondary high-temperature acidizing roasting, aluminum is removed through first-step low-temperature roasting before lithium extraction, the loss of a large amount of lithium caused by difficulty in lithium-aluminum separation due to leaching of a large amount of aluminum after second-step high-temperature acidizing roasting is greatly reduced, the conversion rate of lithium is higher, and the yield of lithium is increased. The intermediate product sodium sulfate can be recycled, so that the energy consumption is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical impurity removal, and in particular to a method for pre-removing impurities before lithium extraction from lepidolite ore. Background Art

[0002] As one of the main minerals for lithium extraction, lithium mica is usually extracted by sulfate roasting, which mainly roasts lithium mica with salt (sulfate, carbonate or their mixed salt) at high temperature to transform or destroy the original crystal structure of lithium mica. The lithium ions in the lithium mica exchange with the alkali metal ions in the added salt to form soluble lithium salts, which are then extracted into the solution through the leaching step. However, during the high-temperature roasting process, heavy metal elements such as beryllium and thallium associated with the lithium mica ore are extracted together and attached to the lithium slag.

[0003] At present, most of the methods for extracting lithium and removing impurities from lepidolite ore are to remove heavy metal elements such as beryllium and thallium after lithium extraction. However, the sulfate roasting method requires a high temperature and consumes a lot of energy. At the same time, the separation of lithium and aluminum during the preparation process of the sulfate roasting method is difficult and easily causes a large loss of lithium. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for pre-removing impurities before lithium extraction from lepidolite ore in view of the deficiencies of the above-mentioned prior art. Through the initial low-temperature roasting and the secondary high-temperature acid roasting, the first low-temperature roasting is used to remove aluminum before lithium extraction, which greatly reduces the large amount of lithium loss caused by the difficulty in lithium-aluminum separation caused by the large amount of aluminum leaching after the second high-temperature acid roasting. The lithium conversion rate is higher, and the intermediate product sodium sulfate can also be recycled, thereby reducing energy consumption.

[0005] The present invention provides a method for pre-removing impurities from lepidolite ore before extracting lithium, comprising the following steps:

[0006] S1, take lepidolite ore and sulfuric acid, through low temperature roasting, obtain the lepidolite primary roasting material after the initial roasting;

[0007] S2, performing three-stage countercurrent washing on the primary calcined lepidolite material prepared in S1 to remove impurities, thereby obtaining a lepidolite ore after the impurities are removed;

[0008] S3, taking the lithium mica ore, sulfuric acid and sodium sulfate prepared in S2 after removing impurities, and subjecting them to high-temperature acidification and roasting to obtain a lithium mica secondary roasting material after secondary roasting;

[0009] S4, leaching and washing the secondary calcined lepidolite material prepared in S3 to obtain a brine leaching solution;

[0010] S5, adding soda ash to the brine leaching solution prepared in S4 to remove impurities, and then evaporating and concentrating to obtain a concentrated solution;

[0011] S6, adding the concentrated solution prepared in S5 to a soda ash solution, stirring and precipitating lithium carbonate to obtain crude lithium carbonate and lithium precipitation mother liquor, and washing with pure water and drying to obtain lithium carbonate;

[0012] S7, the lithium precipitation mother liquor prepared in S6 is subjected to acidification, decarbonization and neutralization, and evaporated and concentrated to obtain sodium sulfate, and the concentrated liquor is returned to S6 for further lithium recovery.

[0013] According to the method for pre-removing impurities from lepidolite before lithium extraction provided by the present invention, the mass ratio of the lepidolite ore to sulfuric acid in S1 is 1:0.1-0.25, the temperature of the low-temperature roasting is 100-150°C, and the time of the low-temperature roasting is 30-120min.

[0014] According to the method for pre-removing impurities from lepidolite before lithium extraction provided by the present invention, the mass ratio of the lepidolite ore, sulfuric acid and sodium sulfate after impurities are removed in S3 is 1:0.2-0.5:0.1, the temperature of the high-temperature acidification and roasting is 250-300°C, and the time of the high-temperature acidification and roasting is 2h.

[0015] According to the method for pre-removing impurities from lepidolite ore before lithium extraction provided by the present invention, the volume ratio of the secondary roasted lepidolite material to water after secondary roasting in S4 is 1:1.5.

[0016] According to the method for pre-removing impurities from lepidolite ore before lithium extraction provided by the present invention, the mass ratio of the brine leachate to soda ash in S5 is 1000:4.

[0017] According to the method for pre-removing impurities from lepidolite ore before lithium extraction provided by the present invention, the volume ratio of the concentrated solution to the soda ash solution in S6 is 1:0.33, and the mass concentration of the soda ash solution is 280 g / L.

[0018] According to the method for pre-removing impurities from lepidolite before lithium extraction provided by the present invention, the stirring speed in S6 is 300 rpm, the stirring temperature is 95° C., and the stirring rate is 300 mL / h.

[0019] According to the method for pre-removing impurities from lepidolite ore before lithium extraction provided by the present invention, the temperature of the pure water in S6 is 95°C, and the drying temperature is 350°C.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The pre-impurity removal method provided by the present invention achieves the purpose of removing the metal impurities beryllium and thallium through step-by-step roasting. The first step is low-temperature roasting to remove aluminum, which greatly reduces the large amount of lithium loss caused by the difficulty in lithium-aluminum separation caused by the large amount of aluminum leaching after the second step of high-temperature acidification roasting, and the lithium conversion rate is higher.

[0022] (2) The sodium sulfate product prepared in the method provided by the present invention can be recycled, and the roasting temperature is relatively low, which greatly reduces the energy consumption of lithium extraction by roasting. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flow chart of the countercurrent washing process in S2. DETAILED DESCRIPTION

[0024] Example 1

[0025] This embodiment provides a method for pre-removing impurities from lepidolite before extracting lithium, and the specific steps are as follows:

[0026] S1, taking lithium mica ore and sulfuric acid in a mass ratio of 1:0.1, respectively, and performing low-temperature roasting at a temperature of 150° C. for 75 min to destroy the lamella structure of lithium mica, and obtaining a primary roasting material of lithium mica after the initial roasting. In this embodiment, the taste of the lithium mica ore is selected to be 1.70%;

[0027] S2, using water as a detergent to perform three-stage countercurrent washing on the primary calcined lepidolite material prepared in S1 to remove impurities, to obtain a calcined lepidolite material after impurities are removed. The countercurrent washing process is as follows: Figure 1 As shown;

[0028] Specifically, clean water is added to the primary calcined material of lepidolite, and then the material is transferred into a separation thickener 1 to obtain an underflow 1 and an overflow 1, wherein the underflow 1 enters a separation thickener 2 to be separated again to obtain an underflow 2 and an overflow 2, the underflow 2 is transferred into a separation thickener 3 to be further separated to obtain an underflow 3 and an overflow 3, the underflow 3 is transferred into a disc filter to obtain a calcined material of lepidolite ore and a filtrate after impurities are removed, the overflow 3 is returned to the separation thickener 3 to be repeatedly separated, and the filtrate and the overflow 2 are returned to the separation thickener 1 to repeat the above operation;

[0029] S3, taking the lithium mica ore after removing impurities prepared in S2, sulfuric acid and sodium sulfate in a mass ratio of 1:0.5:0.1, respectively, and performing high-temperature acidification roasting at a temperature of 275°C for 2h to obtain a lithium mica secondary roasting material after secondary roasting;

[0030] S4, adding water to the secondary roasted lepidolite material prepared in S3 at a volume ratio of 1:1.5, leaching and washing to obtain a brine leachate, wherein the concentration of lithium in the brine leachate is 5.5 g / L;

[0031] S5, adding NaOH to the brine leaching solution prepared in S4 to adjust the pH value to 12, filtering and separating impurity elements such as magnesium, iron, and manganese, then adding soda ash at a liquid-solid mass ratio of 1000:4, stirring at a speed of 300 rpm at room temperature for 30 minutes, then filtering and separating the impurity precipitate and brine, and removing the calcium element, and the obtained brine is evaporated and concentrated to obtain a concentrated solution;

[0032] S6, adding a soda ash solution with a mass concentration of 280 g / L to the concentrated solution prepared in S5 at a liquid-to-solid mass ratio of 1:0.33, stirring and precipitating lithium carbonate at a temperature of 95°C and a rotation speed of 300 rpm, and adding the concentrated solution at a rate of 300 mL / h to obtain crude lithium carbonate and lithium precipitation mother liquor, washing with pure water at a temperature of 95°C, and drying at a temperature of 350°C to obtain lithium carbonate;

[0033] S7. Sulfuric acid is added to the lithium precipitation mother liquor prepared in S6 for decarbonization-neutralization. After adjusting the pH value to 7, the mass concentration of lithium reaches 12 g / L after evaporation and concentration. The precipitated sodium sulfate can be returned to S2 for recycling, and the concentrated solution is returned to S6 for further lithium recovery.

[0034] Example 2

[0035] This embodiment provides a method for pre-removing impurities from lepidolite before extracting lithium, and the specific steps are as follows:

[0036] S1, taking lithium mica ore and sulfuric acid in a mass ratio of 1:0.25, respectively, and performing low-temperature roasting at a temperature of 100° C. for 75 minutes to destroy the sheet structure of lithium mica, and obtain a primary roasted lithium mica material after the initial roasting;

[0037] S2, using water as a detergent to perform three-stage countercurrent washing on the primary calcined lepidolite material prepared in S1 to remove impurities, thereby obtaining a lepidolite calcined material after the impurities are removed;

[0038] S3, taking the lithium mica ore after removing impurities prepared in S2, sulfuric acid and sodium sulfate in a mass ratio of 1:0.4:0.1, respectively, and performing high-temperature acidification roasting at a temperature of 300° C. for 2 hours to obtain a lithium mica secondary roasting material after secondary roasting;

[0039] S4, adding water to the secondary roasted lepidolite material prepared in S3 at a mass ratio of 1:1.5, leaching and washing to obtain a brine leachate, wherein the concentration of lithium in the brine leachate is 5.1 g / L;

[0040] S5, adding NaOH to the brine leaching solution prepared in S4 to adjust the pH to 12, filtering and separating impurity elements such as magnesium, iron, and manganese, then adding soda ash at a liquid-solid mass ratio of 1000:4, stirring at a speed of 300 rpm at room temperature for 30 minutes, then filtering and separating the impurity precipitate and brine, and removing the calcium element, and the obtained brine is evaporated and concentrated to obtain a concentrated solution;

[0041] S6, adding a soda ash solution with a mass concentration of 280 g / L to the concentrated solution prepared in S5 at a liquid-to-solid mass ratio of 1:0.33, stirring and precipitating lithium carbonate at a temperature of 95° C. and a rotation speed of 300 rpm, and adding the concentrated solution at a rate of 300 mL / h to obtain crude lithium carbonate and lithium precipitation mother liquor, washing with pure water at a temperature of 95° C., and drying at a temperature of 350° C. to obtain lithium carbonate;

[0042] S7. Sulfuric acid is added to the lithium precipitation mother liquor prepared in S6 for decarbonization-neutralization. After adjusting the pH value to 7, the mass concentration of lithium reaches 11 g / L after evaporation and concentration. The precipitated sodium sulfate can be returned to S2 for recycling, and the concentrated solution is returned to S6 for further lithium recovery.

[0043] Example 3

[0044] This embodiment provides a method for pre-removing impurities from lepidolite before extracting lithium, and the specific steps are as follows:

[0045] S1, taking lithium mica ore and sulfuric acid in a mass ratio of 1:0.2, respectively, and performing low-temperature roasting at a temperature of 120° C. for 75 minutes to destroy the lamella structure of lithium mica, and obtain a primary roasted lithium mica material after the initial roasting;

[0046] S2, using water as a detergent to perform three-stage countercurrent washing on the primary calcined lepidolite material prepared in S1 to remove impurities, thereby obtaining a lepidolite calcined material after the impurities are removed;

[0047] S3, taking the lithium mica ore after removing impurities prepared in S2, sulfuric acid and sodium sulfate in a mass ratio of 1:0.3:0.1, respectively, and performing high-temperature acidification roasting at a temperature of 270° C. for 2 hours to obtain a lithium mica secondary roasting material after secondary roasting;

[0048] S4, adding water to the secondary roasted lepidolite material prepared in S3 at a mass ratio of 1:1.5, leaching and washing to obtain a brine leachate, wherein the concentration of lithium in the brine leachate is 4.5 g / L;

[0049] S5, adding NaOH to the brine leaching solution prepared in S4 to adjust the pH to 12, filtering and separating impurity elements such as magnesium, iron, and manganese, then adding soda ash at a liquid-solid mass ratio of 1000:4, stirring at a speed of 300 rpm at room temperature for 30 minutes, then filtering and separating the impurity precipitate and brine, and removing the calcium element, and the obtained brine is evaporated and concentrated to obtain a concentrated solution;

[0050] S6, adding 280g / L of soda ash solution to the concentrated solution prepared in S5 at a liquid-to-solid mass ratio of 1:0.33, stirring and precipitating lithium carbonate at a temperature of 95°C and a rotation speed of 300rpm, and adding the concentrated solution at a rate of 300mL / h to obtain crude lithium carbonate and lithium precipitation mother liquor, washing with pure water at a temperature of 95°C, and drying at a temperature of 350°C to obtain lithium carbonate;

[0051] S7. Sulfuric acid is added to the lithium precipitation mother liquor prepared in S6 for decarbonization-neutralization. After adjusting the pH value to 7, the mass concentration of lithium reaches 9.5 g / L after evaporation and concentration. The precipitated sodium sulfate can be returned to S2 for recycling, and the concentrated solution is returned to S6 for further lithium recovery.

[0052] Example 4

[0053] This embodiment provides a method for pre-removing impurities from lepidolite before extracting lithium, and the specific steps are as follows:

[0054] S1, taking lithium mica ore and sulfuric acid in a mass ratio of 1:0.15, respectively, and performing low-temperature roasting at a temperature of 135° C. for 75 minutes to destroy the sheet structure of lithium mica, and obtain a primary roasted lithium mica material after the initial roasting;

[0055] S2, using water as a detergent to perform three-stage countercurrent washing on the primary calcined lepidolite material prepared in S1 to remove impurities, thereby obtaining a lepidolite calcined material after the impurities are removed;

[0056] S3, taking the lithium mica ore after removing impurities prepared in S2, sulfuric acid and sodium sulfate in a mass ratio of 1:0.2:0.1, respectively, and performing high-temperature acidification roasting at a temperature of 250° C. for 2 hours to obtain a lithium mica secondary roasting material after secondary roasting;

[0057] S4, adding water to the secondary roasted lepidolite material prepared in S3 at a mass ratio of 1:1.5, leaching and washing to obtain a brine leachate, wherein the concentration of lithium in the brine leachate is 4 g / L;

[0058] S5, adding NaOH to the brine leaching solution prepared in S4 to adjust the pH to 12, filtering and separating impurity elements such as magnesium, iron, and manganese, then adding soda ash at a liquid-solid mass ratio of 1000:4, stirring at a speed of 300 rpm at room temperature for 30 minutes, then filtering and separating the impurity precipitate and brine, and removing the calcium element, and the obtained brine is evaporated and concentrated to obtain a concentrated solution;

[0059] S6. Add 280 g / L of soda ash solution to the concentrated solution prepared in S5 at a liquid-to-solid mass ratio of 1:0.33, stir and precipitate lithium carbonate at a temperature of 95° C. and a rotation speed of 300 rpm, and add the concentrated solution at a rate of 300 mL / h to obtain crude lithium carbonate, wash with pure water at a temperature of 95° C., and dry at a temperature of 350° C. to obtain lithium carbonate;

[0060] S7. Sulfuric acid is added to the lithium precipitation mother liquor prepared in S6 for decarbonization-neutralization. After adjusting the pH value to 7, the mass concentration of lithium reaches 8 g / L after evaporation and concentration. The precipitated sodium sulfate can be returned to S2 for recycling, and the concentrated solution is returned to S6 for further lithium recovery.

[0061] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for pre-removing impurities from lepidolite ore before extracting lithium, characterized in that: The following steps are involved: S1, take lepidolite ore and sulfuric acid, through low temperature roasting, obtain the lepidolite primary roasting material after the initial roasting; S2, performing three-stage countercurrent washing on the primary calcined lepidolite material prepared in S1 to remove impurities, thereby obtaining a lepidolite ore after the impurities are removed; S3, taking the lithium mica ore, sulfuric acid and sodium sulfate prepared in S2 after removing impurities, and subjecting them to high-temperature acidification and roasting to obtain a lithium mica secondary roasting material after secondary roasting; S4, leaching and washing the secondary calcined lepidolite material prepared in S3 to obtain a brine leachate; S5, adding soda ash to the brine leaching solution prepared in S4 to remove impurities, and then evaporating and concentrating to obtain a concentrated solution; S6, adding the concentrated solution prepared in S5 to a soda ash solution, stirring and precipitating lithium carbonate to obtain crude lithium carbonate and lithium precipitation mother liquor, and washing with pure water and drying to obtain lithium carbonate; S7, the lithium precipitation mother liquor prepared in S6 is subjected to acidification, decarbonization and neutralization, and evaporated and concentrated to obtain sodium sulfate, and the concentrated liquor is returned to S6 for further lithium recovery.

2. The method for pre-removing impurities before extracting lithium from lepidolite ore according to claim 1, characterized in that: The mass ratio of the lepidolite ore to the sulfuric acid in S1 is 1:0.1-0.25, the temperature of the low-temperature roasting is 100-150° C., and the time of the low-temperature roasting is 30-120 min.

3. The method for pre-removing impurities before extracting lithium from lepidolite according to claim 1, characterized in that: The mass ratio of the lithium mica ore, sulfuric acid and sodium sulfate after impurities are removed in S3 is 1:0.2-0.5:0.1, the temperature of the high-temperature acidification roasting is 250-300°C, and the time of the high-temperature acidification roasting is 2h.

4. The method for pre-removing impurities before extracting lithium from lepidolite ore according to claim 1, characterized in that: The volume ratio of the secondary calcined lepidolite material to water after secondary calcination in S4 is 1:1.

5.

5. The method for pre-removing impurities before extracting lithium from lepidolite ore according to claim 1, characterized in that: The mass ratio of the brine extract to soda ash in S5 is 1000:

4.

6. The method for pre-removing impurities from lepidolite ore before extracting lithium according to claim 1, characterized in that: The volume ratio of the concentrated solution to the soda ash solution in S6 is 1:0.33, and the mass concentration of the soda ash solution is 280 g / L.

7. The method for pre-removing impurities from lepidolite ore before extracting lithium according to claim 1, characterized in that: The stirring speed in S6 is 300 rpm, the stirring temperature is 95° C., and the feeding rate of the concentrated liquid is 300 mL / h.

8. The method for pre-removing impurities before extracting lithium from lepidolite ore according to claim 1, characterized in that: The temperature of the pure water in S6 is 95°C, and the drying temperature is 350°C.

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