A method for preparing lithium carbonate by double treatment of spodumene with acid salt

Abstract

The application relates to the field of lithium carbonate preparation, in particular to a method for preparing lithium carbonate by using acid salt double treatment on spodumene. The method comprises the following steps: ball milling and crushing spodumene; spraying 10-20 ml of strong acid on the crushed spodumene according to 100 g of the spodumene, carrying out ripening to obtain ripened spodumene; adding soluble alkali metal sulfate salt or soluble alkali earth metal sulfate salt into the ripened spodumene according to the weight ratio of (2-3):10, uniformly mixing to obtain stabilized spodumene; roasting the stabilized spodumene at a temperature of not less than 1200 DEG C, so that the spodumene is in a glass state; then adding coal powder according to the weight ratio of (3-7):20, fully burning the coal powder to obtain a lithium carbonate crude product; and carrying out settlement, filtration, washing and drying on the lithium carbonate crude product to obtain lithium carbonate. The method can prepare lithium carbonate with high purity by using acid ripening and salt replacement, has low energy consumption, has low requirement on equipment, and makes up for various defects in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium carbonate preparation, more particularly, it relates to a method for preparing lithium carbonate by double treatment of lithium aluminosilicate with acid salt. BACKGROUND

[0002] With the world's energy shortage, the application of electronic devices is more and more widely used in the field of transportation and production, and the demand for lithium ion batteries in various industries is increasing. In lithium ion batteries, lithium carbonate occupies an important position, including but not limited to: lithium carbonate is one of the main raw materials of lithium ion batteries, which can provide lithium ions and is essential for the normal operation of the battery; lithium carbonate has the characteristics of high energy density, which makes lithium ion batteries have higher storage capacity, thereby prolonging the service life of the battery; lithium carbonate can react with compounds such as lithium manganate to prepare the positive material of lithium ion batteries.

[0003] The existing enterprises for preparing lithium carbonate mainly use lithium ore to prepare lithium carbonate. Lithium aluminosilicate, as a kind of lithium ore, has a relatively abundant reserve and a moderate processing difficulty. How to prepare lithium carbonate from lithium aluminosilicate has become a research hotspot of major battery manufacturers.

[0004] The existing methods for preparing lithium carbonate from lithium aluminosilicate mainly include the following methods: lime sintering method, chlorination roasting method, and sulfuric acid method. However, the lime sintering method has high energy consumption and low yield, which easily causes waste of lithium aluminosilicate raw materials; in the chlorination roasting method, the corrosion of the furnace gas is strong, which requires high equipment; the sulfuric acid method has a large amount of solid waste, and the prepared lithium carbonate also has a lot of sodium salt, and the purity needs to be improved; at the same time, sulfuric acid can corrode equipment and react with fluoride to generate hydrogen fluoride, which requires additional tail gas treatment equipment, and has high requirements for equipment.

[0005] Therefore, how to provide a lithium carbonate preparation method with low equipment requirements, low energy consumption, and high product purity has become a problem to be solved. SUMMARY

[0006] In order to optimize the existing technical problems of high energy consumption, high equipment requirements, and low product purity in the preparation of lithium carbonate from lithium aluminosilicate, the present application provides a method for preparing lithium carbonate by double treatment of lithium aluminosilicate with acid salt. By using acid curing and salt replacement, lithium carbonate with high purity can be prepared, and the energy consumption is low, the equipment requirements are low, and the shortcomings of the prior art in preparing lithium carbonate are made up.

[0007] The method for preparing lithium carbonate by double treatment of lithium aluminosilicate with acid salt provided by the present application adopts the following technical scheme:

[0008] A method for preparing lithium carbonate by double treatment of lithium aluminosilicate with acid salt, comprising the following steps:

[0009] (1) ball-milling spodumene, and spraying 10-20 ml of strong acid per 100 g of spodumene to the ball-milled spodumene to obtain cooked spodumene;

[0010] (2) adding 2-3 parts by weight of soluble alkali metal sulfate or soluble alkali earth metal sulfate to 10 parts by weight of the cooked spodumene in a weight ratio of (2-3):10 to obtain stabilized spodumene;

[0011] (3) calcining the stabilized spodumene at a temperature of not less than 1200 ℃ to make the spodumene in a glassy state, and then adding coal powder in a weight ratio of (3-7):20, and obtaining a lithium carbonate crude product after the coal powder is fully combusted;

[0012] (4) obtaining lithium carbonate after the lithium carbonate crude product is subjected to sedimentation, filtration, washing, and drying.

[0013] In one specific implementation, the step (1) is performed at room temperature without calcination.

[0014] In one specific implementation, the specific operation of the step (1) is that the strong acid is sprayed onto the spodumene, followed by stirring at 60-80 r / min for 1-2 h, and then standing for 1-2 h after the stirring is completed.

[0015] In one specific implementation, the strong acid is sulfuric acid or hydrochloric acid.

[0016] In one specific implementation, the soluble alkali metal sulfate includes lithium sulfate, sodium sulfate, or potassium sulfate; and the soluble alkali earth metal sulfate includes magnesium sulfate or calcium sulfate.

[0017] In one specific implementation, in the step (1), the ball-milled spodumene is sieved through an 80-100 mesh sieve.

[0018] In one specific implementation, in the step (3), the calcination temperature is 1250-1300 ℃, and the calcination time is 40-60 min.

[0019] In one specific implementation, the step (3) is performed in a closed environment, and the role of the coal powder includes providing a heat source to make the stabilized spodumene uniformly heated, and making the combustion product of the coal powder, carbon dioxide, as a raw material to combine with lithium to generate lithium carbonate.

[0020] The application has the following beneficial effects: in the maturation process, the method of the application uses acid to mature spodumene, mainly strong acid reacts with silicate in spodumene, causing the decomposition of silicate and the release of silicon. Among them, silicon and aluminum exist in the form of sulfate, accompanied by the release of water. The maturation process separates silicon and aluminum from spodumene to form stable compounds. After silicon and aluminum are separated from spodumene, the remaining mineral structure becomes unstable, and the acid-treated spodumene will enter the glass state at high temperature. At this time, the mineral structure of the glass state makes the lithium therein more easily react with other ions. The added soluble sulfate (such as lithium sulfate, magnesium sulfate) reacts with lithium in the mineral of the glass state to form stable compounds. These stable compounds will not react again during the calcination process, thereby avoiding the generation of harmful glass state products. Finally, the carbon dioxide generated by the combustion of coal powder is combined with lithium to form lithium carbonate, avoiding harmful glass state, and the generated lithium carbonate has high purity, and the process is simple, low in energy consumption, low in equipment requirement, and makes up for the deficiencies in the prior art of using spodumene to prepare lithium carbonate. DETAILED DESCRIPTION

[0021] In the prior art, concentrated sulfuric acid is generally used to treat spodumene, a large amount of acid is used to dissolve spodumene, or calcium carbonate is added for calcination, the calcination temperature is very high, and the equipment will be corroded, and the energy consumption is very high. The application uses a small amount of acid to mature spodumene, aiming to destroy the structure of spodumene and dissolve part of the silicate, rather than dissolve and release lithium, so that lithium is more easily produced into salt, and no harmful glass state appears in the subsequent calcination process. The acid-salt double treatment of spodumene makes the lithium in spodumene form a stable glass state compound; coal powder is then added to reduce energy consumption, and the combustion products of coal powder are combined with lithium carbonate to form lithium carbonate. The advantages are small equipment burden, low energy consumption, and common materials, which can be mass-produced industrially.

[0022] The application will be further described in detail below in combination with examples.

[0023] EMBODIMENT

[0024] EMBODIMENT 1

[0025] The embodiment provides a method for preparing lithium carbonate by double treatment of spodumene with acid and salt, specifically comprising the following steps:

[0026] (1) The spodumene is ground into powder and sieved through an 80-mesh sieve. 10 ml of strong acid is sprayed onto 100 g of the ground spodumene. The spodumene is stirred at 60 r / min for 2 h, and then left to stand for 2 h without heating. The structure of the spodumene is destroyed by the acid, so that no harmful glassy state is formed in the subsequent calcination process. The spodumene is then obtained. The strong acid includes hydrochloric acid and sulfuric acid. In this embodiment, sulfuric acid is preferred. Sulfuric acid has a high boiling point and is not easy to evaporate. The sulfate salt of the product is easy to remove.

[0027] (2) 2 parts by weight of a soluble alkali metal sulfate or a soluble alkali earth metal sulfate is added to 10 parts by weight of the spodumene, and mixed to obtain stabilized spodumene. The soluble alkali metal sulfate can be lithium sulfate, sodium sulfate or potassium sulfate. The soluble alkali earth metal sulfate can be magnesium sulfate or calcium sulfate. In this embodiment, sodium sulfate is used.

[0028] (3) The stabilized spodumene is calcined in a sealed environment at a temperature of 1250°C and a pressure of 150 kPa for 40 min, so that the spodumene is in a glassy state. Coal powder is then added in a weight ratio of 3:20 to the stabilized spodumene. After the coal powder is fully combusted, a lithium carbonate crude product is obtained. The coal powder has two main functions. First, the coal powder is self-ignited at the above calcination temperature, and heat is transferred to the stabilized spodumene, so that the energy consumption is saved, the stability of the spodumene is increased, the calcination time is shortened, and the processing efficiency is improved. Second, carbon dioxide is generated after the coal powder is self-ignited. The carbon dioxide is combined with lithium in the stabilized spodumene to form lithium carbonate.

[0029] (4) The lithium carbonate crude product is subjected to sedimentation, filtration, washing and drying to obtain lithium carbonate with a purity of 96.86% and a yield of 51.95%. The sedimentation is mainly to remove the unburned coal powder. The filtration is to remove the soluble alkali metal sulfate or the soluble alkali earth metal sulfate. The washed and dried lithium carbonate has a high purity. The specific operation is as follows: sedimentation: the lithium carbonate crude product is placed in a sedimentation tank, 40 parts by weight of water is added, and the mixture is stirred at 20 r / min for 10 min, and then left to stand for 3 h; filtration: the solid product after sedimentation is filtered by using a Buchner funnel and a vacuum pump; washing: the filter cake is washed with distilled water, and the amount of water used is 300 ml, and the washing is performed for 3 times; drying: the washed lithium carbonate is placed in a drying oven, the temperature is controlled at 100°C, and the drying is performed for 4 h.

[0030] Example 2

[0031] The method for preparing lithium carbonate by using acid and salt double treatment of spodumene includes the following steps.

[0032] (1) The spodumene is ball-milled and crushed, and then passed through a 80-mesh sieve; 13 ml of strong acid is sprayed on the crushed spodumene per 100 g of spodumene, and then stirred at 60 r / min for 1.25 h, and after the stirring is completed, it is left to stand for 1.25 h, and the maturation is carried out at room temperature; the maturation spodumene is obtained after step (1) is completed; the strong acid in this example is sulfuric acid.

[0033] (2) 2.3 parts by weight of soluble alkali metal sulfate or soluble alkali earth metal sulfate is added to 10 parts by weight of the maturation spodumene according to a weight ratio of 2.3:10, and mixed uniformly to obtain the stabilized spodumene; the soluble alkali metal sulfate in this example is potassium sulfate.

[0034] (3) The stabilized spodumene is calcined in a closed environment, the calcination temperature is controlled at 1260℃, the pressure is 160 kPa, and the calcination time is 45 min, so that the spodumene is in a glassy state; then coal powder is added according to a weight ratio of coal powder: stabilized spodumene = 1:5, and the lithium carbonate crude product is obtained after the coal powder is fully combusted.

[0035] (4) The lithium carbonate crude product is subjected to the steps of settling, filtering, washing and drying as described in Example 1 to obtain lithium carbonate with a purity of 97.96% and a yield of 54.36%.

[0036] Example 3

[0037] This example provides a method for preparing lithium carbonate by double treatment of spodumene with acid salt, which specifically comprises the following steps:

[0038] (1) The spodumene is ball-milled and crushed, and then passed through a 90-mesh sieve; 15 ml of strong acid is sprayed on the crushed spodumene per 100 g of spodumene, and then stirred at 70 r / min for 1.5 h, and after the stirring is completed, it is left to stand for 1.5 h, and the maturation is carried out at room temperature; the maturation spodumene is obtained after step (1) is completed; the strong acid in this example is sulfuric acid.

[0039] (2) 2.5 parts by weight of soluble alkali metal sulfate or soluble alkali earth metal sulfate is added to 10 parts by weight of the maturation spodumene according to a weight ratio of 2.5:10, and mixed uniformly to obtain the stabilized spodumene; the soluble alkali metal sulfate in this example is lithium sulfate, which can also be used as another lithium source.

[0040] (3) The stabilized spodumene is calcined in a closed environment, the calcination temperature is controlled at 1275℃, the pressure is 175 kPa, and the calcination time is 50 min, so that the spodumene is in a glassy state; then coal powder is added according to a weight ratio of coal powder: stabilized spodumene = 1:4, and the lithium carbonate crude product is obtained after the coal powder is fully combusted.

[0041] (4) The crude lithium carbonate is subjected to the steps of settling, filtering, washing and drying as described in Example 1 to obtain lithium carbonate with a purity of 98.86% and a yield of 63.58%.

[0042] Example 4

[0043] The present example provides a method for preparing lithium carbonate by double treatment of spodumene with acid and salt, which specifically comprises the following steps:

[0044] (1) The spodumene is ground into powder and then sieved through a 100-mesh sieve; 18 ml of strong acid is sprayed onto the ground spodumene per 100 g of the spodumene, followed by stirring at 80 r / min for 1.75 h, standing for 1.75 h after completion of stirring, and aging at room temperature; the aged spodumene is obtained after completion of step (1); the strong acid in the present example is sulfuric acid.

[0045] (2) 2.8 parts by weight of a soluble alkali metal sulfate salt or a soluble alkaline earth metal sulfate salt is added to 10 parts by weight of the aged spodumene at a weight ratio of 2.8:10, and the mixture is uniformly mixed to obtain stabilized spodumene; the soluble alkaline earth metal sulfate salt in the present example is magnesium sulfate.

[0046] (3) The stabilized spodumene is calcined in a sealed environment, the calcination temperature is controlled at 1285°C, the pressure is controlled at 180 kPa, and the calcination time is controlled at 55 min, so that the spodumene is in a glassy state; then coal powder is added at a weight ratio of coal powder: stabilized spodumene = 3:10, and the coal powder is fully combusted to obtain a crude lithium carbonate product.

[0047] (4) The crude lithium carbonate is subjected to the steps of settling, filtering, washing and drying as described in Example 1 to obtain lithium carbonate with a purity of 98.86% and a yield of 63.58%.

[0048] Example 5

[0049] The present example provides a method for preparing lithium carbonate by double treatment of spodumene with acid and salt, which specifically comprises the following steps:

[0050] (1) The spodumene is ground into powder and then sieved through a 100-mesh sieve; 20 ml of strong acid is sprayed onto the ground spodumene per 100 g of the spodumene, followed by stirring at 80 r / min for 1 h, standing for 1 h after completion of stirring, and aging at room temperature; the aged spodumene is obtained after completion of step (1); the strong acid in the present example is sulfuric acid.

[0051] (2) 3 parts by weight of a soluble alkali metal sulfate salt or a soluble alkaline earth metal sulfate salt is added to 10 parts by weight of the aged spodumene at a weight ratio of 3:10, and the mixture is uniformly mixed to obtain stabilized spodumene; the soluble alkaline earth metal sulfate salt in the present example is calcium sulfate.

[0052] (3) The stabilized lithium aluminosilicate is calcined in a closed environment, the calcination temperature is controlled at 1300°C, the pressure is 200 kPa, and the calcination time is 60 min, so that the lithium aluminosilicate is in a glassy state; then coal powder is added in a weight ratio of coal powder: stabilized lithium aluminosilicate = 7:20, and the coal powder is fully combusted to obtain a lithium carbonate crude product.

[0053] (4) The lithium carbonate crude product is subjected to the steps of settling, filtering, washing, and drying as described in Example 1 to obtain lithium carbonate with a purity of 97.56% and a yield of 50.83%.

[0054] Comparative Example

[0055] Comparative Example 1

[0056] This comparative example is compared with Example 1, the difference being that the step (1) of this comparative example is: 100 ml of strong acid is sprayed on 100 g of lithium aluminosilicate after being pulverized, so that the sulfuric acid submerges the lithium aluminosilicate to obtain a submerged ripened lithium aluminosilicate. The purity of the lithium carbonate product of Comparative Example 1 is 71.34%, and the yield is 58.57%.

[0057] Comparative Example 2

[0058] This comparative example is compared with Example 1; a method for preparing lithium carbonate using lithium aluminosilicate provided by this comparative example includes the following steps:

[0059] (1) The lithium aluminosilicate is pulverized by ball milling and then passed through an 80-mesh sieve; 10 ml of strong acid is sprayed on 100 g of the pulverized lithium aluminosilicate, followed by stirring at 60 r / min for 2 h, and then standing for 2 h to obtain ripened lithium aluminosilicate;

[0060] (2) 2-3 parts by weight of calcium carbonate is added to 10 parts by weight of the ripened lithium aluminosilicate in a weight ratio of (2-3):10, and the mixture is uniformly mixed to obtain stabilized lithium aluminosilicate;

[0061] (3) The stabilized lithium aluminosilicate is calcined at a temperature of not less than 1200°C, so that the lithium aluminosilicate is in a glassy state, and a lithium carbonate crude product is obtained after cooling;

[0062] (4) The lithium carbonate crude product is subjected to settling, filtering, washing, and drying to obtain lithium carbonate with a purity of 86.54% and a yield of 43.67%.

[0063] Result analysis:

[0064] From the above examples and comparative examples and the corresponding product purity, it can be seen that in examples 1-5, the purity of lithium carbonate obtained in example 3 is the highest, which may be due to: 1. The parameters of example 3 are more optimal, including the addition ratio of each reagent time and the calcination temperature, which are all conducive to the removal of impurities and the generation of lithium carbonate; 2. The soluble alkali metal sulfate in example 3 is lithium sulfate, which can be used as a lithium source to supplement the loss of lithium in spodumene, so the product yield is the highest, which is the best embodiment of the present application.

[0065] From example 1 and comparative example 1, it can be seen that the product purity of comparative example 1 is worse than that of example 1, and the yield is higher than that of example 1, which may be due to the fact that the acid addition amount in comparative example 1 is too much, and the spodumene is over-reacted, although it can lead to more sufficient release of lithium, but it is inevitable to generate other by-products, thereby reducing the purity of lithium carbonate, and sulfuric acid may also introduce impurities by corroding the equipment, leading to a decrease in the purity of lithium carbonate.

[0066] From example 1 and comparative example 2, it can be seen that the product purity and yield of comparative example 2 are worse than those of example 1, which may be due to the fact that in comparative example 2, the sodium sulfate added in step (2) of example 1 is replaced by calcium carbonate, and the step of adding coal powder in step (3) is deleted, which will bring about a significant decrease in the yield and purity of lithium carbonate, and the reasons may be as follows: In the scheme of example 1, sodium sulfate is used to react with spodumene, mainly to utilize the reaction of sodium sulfate with spodumene to generate stable compounds such as lithium sulfate, etc., which will not decompose in the subsequent calcination process, so as to stably generate lithium carbonate. If it is replaced by calcium carbonate, the reaction mechanism of calcium carbonate with spodumene is different from that of sodium sulfate, calcium carbonate and spodumene generate lithium carbonate, and other by-products such as calcium oxide, magnesium carbonate, carbide, etc. may also be generated, leading to a decrease in product yield and purity; secondly, in the reaction of sodium sulfate and spodumene, the sulfate ion is heavier, which is more easily combined with light elements such as lithium, which helps to move the reaction equilibrium to the direction of generating lithium carbonate, while the carbonate ion is lighter, and the reaction equilibrium may not be as favorable as the reaction equilibrium of sodium sulfate and lithium, which may lead to part of the lithium not being converted into lithium carbonate. Since the preliminary stabilization treatment of spodumene by the sulfate salt has been carried out in step (2), the subsequent calcination process is mainly to make the spodumene in a glassy state, so as to be more conducive to the generation of lithium carbonate, and the addition of coal powder is cancelled, which means that there is no additional heat source, and it may be difficult to reach the required calcination temperature only by the reaction of calcium carbonate and spodumene, which may lead to part of the lithium not being completely converted into lithium carbonate, and it can be predicted that the decomposition of calcium carbonate itself under heat will increase the energy consumption.

[0067] In summary, in the maturation process, the method of the present application utilizes acid to mature the spodumene, mainly strong acid reacts with silicate in spodumene, resulting in the decomposition of silicate and the release of silicon. Among them, silicon and aluminum exist in the form of sulfate, accompanied by the release of water. The maturation process separates silicon and aluminum from spodumene to form stable compounds. After silicon and aluminum are separated from spodumene, the remaining mineral structure becomes unstable. At high temperatures, the acid-treated spodumene enters the glassy state. At this time, the mineral structure of the glassy state makes it easier for lithium in it to react with other ions. The added soluble sulfate (such as lithium sulfate, magnesium sulfate) reacts with lithium in the mineral of the glassy state to form stable compounds. These stable compounds will not react again during the calcination process, thereby avoiding the generation of harmful glassy state products. Finally, the carbon dioxide generated by the combustion of coal powder is combined with lithium to generate lithium carbonate, avoiding harmful glassy state, the generated lithium carbonate has high purity, and the process is simple, low in energy consumption, low in requirement for equipment, and makes up for the deficiencies in the prior art of preparing lithium carbonate from spodumene.

[0068] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, as long as the modifications are within the scope of the claims of the present application.

Claims

1. A method for preparing lithium carbonate from spodumene by double treatment with acid salt, characterized in that: The method comprises the following steps: (1) ball-milling and crushing the spodumene; spraying 10-20 ml of strong acid per 100 g of the spodumene, and spraying the strong acid onto the crushed spodumene to perform ripening, thereby obtaining ripened spodumene, wherein the step (1) is performed at room temperature without roasting, and the specific operation of the step (1) ripening is that the strong acid is sprayed onto the spodumene, followed by stirring at 60-80 r / min for 1-2 h, and then standing for 1-2 h; (2) adding 2-3 parts by weight of soluble alkali metal sulfate or magnesium sulfate or calcium sulfate to 10 parts by weight of the ripened spodumene in a weight ratio of (2-3):10, and uniformly mixing to obtain stabilized spodumene; (3) roasting the stabilized spodumene at a temperature of not less than 1200 ℃, so that the spodumene is in a glassy state; then adding coal powder in a weight ratio of (3-7):20, and obtaining a lithium carbonate crude product after the coal powder is fully combusted; (4) obtaining lithium carbonate after the lithium carbonate crude product is subjected to sedimentation, filtration, washing, and drying.

2. The method for preparing lithium carbonate from spodumene by double treatment of acid salt according to claim 1, characterized in that: The strong acid is sulfuric acid or hydrochloric acid.

3. The method for preparing lithium carbonate from spodumene by double treatment of acid salt according to claim 1, characterized in that: The soluble alkali metal sulfate includes lithium sulfate, sodium sulfate, or potassium sulfate.

4. The method for preparing lithium carbonate from spodumene by double treatment of acid salt according to claim 1, characterized in that: In the step (1), the crushed spodumene is sieved through a 80-100 mesh sieve.

5. The method for preparing lithium carbonate from spodumene by double treatment of acid salt according to claim 1, characterized in that: In the step (3), the roasting temperature is 1250-1300 ℃, and the roasting time is 40-60 min.

6. The method for preparing lithium carbonate from spodumene by double treatment of acid salt according to claim 1, characterized in that: The step (3) is performed in a closed environment, and the role of the coal powder includes providing a heat source, making the stabilized spodumene uniformly heated, and using the combustion product of the coal powder, carbon dioxide, as a raw material to combine with lithium to generate lithium carbonate.