A method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate

Abstract

The application discloses a method for producing battery-grade lithium carbonate by refining and purifying crude lithium carbonate, and belongs to the technical field of refining and purifying crude lithium carbonate. The method mainly refines and purifies the crude lithium carbonate through reverse carbonization, composite impurity removal and microwave pyrolysis. The reverse carbonization accelerates the countercurrent conversion of the dissolved lithium carbonate and the mass transfer carbon dioxide, effectively reduces the resistance of the carbon dioxide and the lithium carbonate carbonization reaction, and further significantly improves the conversion efficiency and shortens the reaction period. The double composite impurity removal further effectively controls the content of impurities such as calcium, magnesium, iron and magnetic substances in the carbonization liquid. The microwave pyrolysis process greatly reduces the energy consumption required for pyrolysis, effectively shortens the reaction time and significantly reduces the loss rate of lithium in the pyrolysis reaction process. The refining and purifying process of the application greatly shortens the reaction period on the basis of ensuring the purifying effect, and has good application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of refining and purifying crude lithium carbonate, and particularly relates to a method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate. BACKGROUND

[0002] Lithium has extremely high energy density, electrical conductivity and chemical activity, and is known as "energy metal". As the most basic and important lithium salt, lithium carbonate is widely used in many fields such as lithium batteries, electronics industry, semiconductors, optical materials, medicine, etc. In addition, lithium carbonate can also be used to prepare various high-value-added lithium compounds. Purity is one of the most important indicators for evaluating the quality of lithium carbonate. The quality requirements for lithium carbonate are relatively high in high-tech application fields, and the conventional industrial-grade lithium carbonate contains many inorganic impurities. Therefore, it is necessary to further refine and purify lithium carbonate to produce high-purity lithium carbonate. At present, the methods for refining and purifying crude lithium carbonate include recrystallization, causticization and carbonization, electrolysis, hydrogenation precipitation, hydrogenation decomposition and ion exchange method, etc. However, these methods have one or more defects such as high purity requirement for raw materials, strict control of reaction conditions, long operation period, poor recycling and repeated use, high cost, and the purity of the final product cannot meet the requirements.

[0003] Chinese patent CN201310507395.X discloses a method for preparing battery-grade lithium carbonate or high-purity lithium carbonate from industrial-grade lithium carbonate, which mainly includes the following steps: mixing industrial-grade lithium carbonate and distilled water to form a slurry, introducing carbon dioxide into the slurry for carbonization, removing calcium, magnesium and other impurities by using ion exchange resin, and obtaining battery-grade or high-purity lithium carbonate by pyrolysis after ion exchange. This process can effectively control the impurity content of the product and obtain battery-grade or high-purity lithium carbonate product. However, the conversion efficiency of industrial-grade lithium carbonate carbonization is low, and multiple ion exchange adsorption is required to obtain lithium carbonate with higher purity. The recycling performance of ion exchange resin is limited, and frequent reduction and regeneration undoubtedly increases the cost.

[0004] Therefore, the existing refining and purification process of industrial-grade lithium carbonate still needs to be further researched and improved, and a refining and purification process for crude lithium carbonate with short production period and high product purity needs to be developed. SUMMARY

[0005] In view of the problems of the existing refining and purification process of hydrogenation decomposition combined with ion adsorption, such as high product quality but unsatisfactory process production period and cost, the present application further improves the process and provides a method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate. The method mainly refines and purifies crude lithium carbonate through reverse carbonization, composite impurity removal and microwave pyrolysis. Reverse carbonization can improve the conversion efficiency, composite impurity removal can further ensure the high purity of the product, and microwave pyrolysis can effectively reduce the loss rate of lithium. The refining and purification process of the present application can obtain high-purity battery-grade lithium carbonate product, and has the advantages of short production period and good recycling performance.

[0006] The application specifically adopts the following technical scheme:

[0007] The application provides a method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate, comprising the following steps:

[0008] Step 1: reverse carbonization

[0009] High-purity carbon dioxide is continuously introduced into deionized water per unit volume, and then the crude lithium carbonate is uniformly dissolved in the deionized water within 40-60 min to perform a carbonization reaction, so that the crude lithium carbonate is hydrogenated and precipitated. The filter residue is removed by plate and frame filtration to obtain a lithium bicarbonate carbonization liquid.

[0010] Step 2: composite impurity removal

[0011] EDTA-Li is added to the lithium bicarbonate carbonization liquid obtained in step 1 to perform a complexation reaction, and then the filter residue is removed by plate and frame filtration. The obtained filtrate is subjected to ion exchange resin adsorption to remove impurities to obtain a lithium bicarbonate purification liquid.

[0012] Step 3: microwave pyrolysis

[0013] The lithium bicarbonate purification liquid obtained in step 2 is subjected to a pyrolysis reaction by microwave heating. The lithium carbonate crystals obtained after the reaction are washed and dried to obtain battery-grade lithium carbonate.

[0014] As a preferred, the deionized water in the reverse carbonization step needs to be kept at a constant temperature of 24-28℃, and high-purity carbon dioxide is continuously introduced while being accompanied by low-frequency ultrasonic treatment. The ultrasonic frequency is 30-60 kHz.

[0015] As a preferred, the flow rate of the continuously introduced pure carbon dioxide in the reverse carbonization step is 0.05-0.12 m 3 / h.

[0016] As a preferred, the solid-liquid ratio of the crude lithium carbonate to the deionized water in the reverse carbonization step is 1:(15-19).

[0017] The carbonation reaction process of passing carbon dioxide gas into the lithium carbonate slurry is actually a chemical reaction process based on mixed mass transfer, the carbon dioxide gas is dissolved into the slurry and diffuses and mass transfers therein, and the dissolved lithium carbonate in the slurry flows and reacts; therefore, to improve the hydrogenation conversion efficiency of the crude lithium carbonate to lithium bicarbonate, the key problem is to accelerate the flow conversion of the dissolved lithium carbonate and the mass transferred carbon dioxide. The conventional process only reasonably optimizes the flow of the passed carbon dioxide and the temperature of the carbonation reaction, but this still cannot achieve a high conversion efficiency, resulting in a long production cycle. The inventors found that, on the basis of passing carbon dioxide in advance to make the carbon dioxide slightly excessive at the initial stage of the reaction, supplemented by low-frequency ultrasonic treatment and continuous addition of crude lithium carbonate for stirring, the mass transfer and flow of the carbon dioxide and the lithium carbonate can be significantly improved, thereby effectively accelerating the carbonation reaction rate of the crude lithium carbonate and the carbon dioxide.

[0018] As preferred, the EDTA-Li in the complex impurity removal step is prepared by the reaction of EDTA and LiOH.

[0019] As preferred, the amount of the EDTA-Li added in the complex impurity removal step is 1.2-1.5 times of the total amount of calcium, magnesium and iron ions in the lithium bicarbonate carbonation liquid.

[0020] As preferred, the ion exchange resin in the complex impurity removal step is any one of a phenolic cation exchange resin, a styrene cation exchange resin and an acrylic macroporous adsorption resin.

[0021] For the lithium bicarbonate carbonation liquid obtained by the above carbonation process, the inventors first use EDTA-Li to preliminarily remove the calcium and magnesium ions in the carbonation liquid, which can effectively complex and remove the iron ions therein, and the iron ions can significantly reduce the recycling performance of the subsequent ion exchange resin; on this basis, the carbonation liquid is further removed by the ion exchange resin; the double complex impurity removal can effectively control the content of the impurities such as calcium, magnesium, iron and magnetic substances in the carbonation liquid, and produce high-purity battery-grade lithium carbonate.

[0022] As preferred, the microwave heating in the microwave pyrolysis step needs to be accompanied by continuous air extraction, specifically, the negative pressure is kept at -0.04 to -0.06 MPa.

[0023] As preferred, the temperature of the microwave heating in the microwave pyrolysis step is 35-65℃, and the pyrolysis reaction time is 50-90 min.

[0024] The pyrolysis of the refining process adopts microwave heating, compared with conventional heating, microwave heating is more comprehensive and uniform, avoids the problem of local heating difference, and the control of the temperature of the feed liquid is more simple; the negative pressure microwave pyrolysis process greatly reduces the energy consumption required for pyrolysis, effectively shortens the reaction time and significantly reduces the loss rate of lithium in the pyrolysis reaction process.

[0025] Compared with the prior art, the beneficial effects of the present application are:

[0026] The present application further improves and optimizes the existing hydrogenation decomposition combined with ion adsorption crude lithium carbonate refining purification process: through reverse carbonization, the convection conversion of dissolved lithium carbonate and mass transfer carbon dioxide is accelerated, the resistance of the carbonation reaction of carbon dioxide and lithium carbonate is effectively reduced, thereby significantly improving the conversion efficiency and shortening the reaction period; through double composite impurity removal, the content of impurities such as calcium, magnesium, iron and magnetic substances in the carbonation liquid is further effectively controlled; the microwave pyrolysis process greatly reduces the energy consumption required for pyrolysis, effectively shortens the reaction time and significantly reduces the loss rate of lithium in the pyrolysis reaction process. The refining and purification process of the present application greatly shortens the reaction period on the basis of ensuring the purification effect, and has good application value. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely in combination with examples. If the specific conditions are not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0029] The crude lithium carbonate used in the experiments of the present application is commercially available, and the lithium carbonate content is 89.20%; the high-purity carbon dioxide is commercially available, and the purity is not less than 99.9%; the EDTA-Li is prepared by reacting EDTA with LiOH at 55℃.

[0030] Example 1

[0031] A method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate, comprising:

[0032] 1. Take 1 weight of crude lithium carbonate and 16 volumes of deionized water according to the solid-liquid ratio of 1:16 (g / mL). First, continuously introduce high-purity carbon dioxide into the deionized water (control parameters: keep the deionized water at a constant temperature of 26℃, and the flow rate of the introduced carbon dioxide is 0.08 m 3 / h) while applying low-frequency ultrasound (40 kHz), then uniformly add the crude lithium carbonate within 45 min, continuously carry out the carbonation reaction to hydrogenate and precipitate the crude lithium carbonate, then remove the filter residue by plate and frame filtration to obtain a lithium bicarbonate carbonation liquid. Detect the content of the obtained lithium bicarbonate carbonation liquid, and calculate the conversion efficiency of lithium carbonate after the 45 min carbonation reaction in this step to be 93.6%.

[0033] 2. Continue to add EDTA-Li to the lithium bicarbonate carbonation liquid (add according to the content of calcium, magnesium and iron ions in the obtained carbonation liquid, and the amount of EDTA-Li added is 1.2 times the total amount of the three ions) to carry out complexation reaction, then remove the filter residue by plate and frame filtration again, and obtain a purified lithium bicarbonate liquid after removing impurities by adsorption of the obtained filtrate on a large-pore acrylic resin (flow rate of 1.5 mL / min). After removing impurities, the removal rate of calcium and magnesium ions in the purified liquid is more than 95%, and the removal rate of iron ions is more than 99% compared with the carbonation liquid before removing impurities.

[0034] 3. Heat the purified lithium bicarbonate liquid to 50℃ by microwave, maintain negative pressure of-0.05 MPa by air extraction, and continuously react for 60 min to obtain lithium carbonate crystals, and finally wash, dry and store. The loss rate of lithium is 1.04%.

[0035] The chemical composition of the lithium carbonate sample prepared in this example is detected according to GB / T11064-2013, and the results are as follows.

[0036] Table 1

[0037] Component Test result Unit Test method / instrument Li2O3 99.87 ％ Titration method Moisture 0.06 ％ Oven drying method K 12.23 ppm ICP-OES Ca 7.65 ppm ICP-OES Mg 0.55 ppm ICP-OES Fe 2.40 ppm ICP-OES Si 5.23 ppm ICP-OES Magnetic substance 422.05 ppb ICP-OES Cl - ]] 4.98 ppm UV-visible spectrophotometer

[0038] Example 2

[0039] A method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate, comprising:

[0040] 1. Take 1 weight of crude lithium carbonate and 19 volumes of deionized water according to the solid-liquid ratio of 1:19 (g / mL). First, continuously introduce high-purity carbon dioxide into the deionized water (control parameters: keep the deionized water at a constant temperature of 24℃, and the flow rate of the introduced carbon dioxide is 0.12 m 3(h) while applying low frequency ultrasound (50 kHz), then adding crude lithium carbonate uniformly within 45 min, continuously carrying out carbonization reaction to make crude lithium carbonate hydrogenated and precipitated, then removing filter residue by plate frame filtration to obtain lithium bicarbonate carbonization liquid. Content detection is carried out on the obtained lithium bicarbonate carbonization liquid, and the conversion efficiency of lithium carbonate after 45 min carbonization reaction in this step is calculated as 90.9%.

[0041] 2. EDTA-Li is continuously added to the lithium bicarbonate carbonization liquid (according to the content of calcium, magnesium and iron ions in the obtained carbonization liquid, the amount of EDTA-Li added is 1.5 times the total amount of the three ions) to carry out complexation reaction, and then plate frame filtration is carried out again to remove filter residue, and the obtained filtrate is adsorbed by acrylic macroporous adsorption resin (flow rate 1.5 mL / min) to remove impurities to obtain lithium bicarbonate purification liquid. After impurity removal, the removal rate of calcium and magnesium ions in the purified liquid is more than 95%, and the removal rate of iron ions is more than 99% compared with the carbonization liquid before impurity removal.

[0042] 3. The lithium bicarbonate purification liquid is heated to 60°C by microwave, and the gas is extracted to maintain a negative pressure of-0.06 MPa for 60 min to obtain lithium carbonate crystals, which are finally washed, dried and stored. The loss rate of lithium is 1.48%.

[0043] The chemical composition of the lithium carbonate sample prepared in this example is detected according to GB / T11064-2013, and the results are as follows.

[0044] Table 2

[0045] Component Test result Unit Test method / instrument Li2O3 99.81 ％ Titration method Moisture 0.08 ％ Oven drying method K 13.85 ppm ICP-OES Ca 9.67 ppm ICP-OES Mg 0.68 ppm ICP-OES Fe 2.44 ppm ICP-OES Si 5.30 ppm ICP-OES Magnetic substance 485.33 ppb ICP-OES Cl - ]] 5.06 ppm UV-visible spectrophotometer

[0046] Example 3

[0047] A method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate, comprising:

[0048] 1. Take 1 weight of crude lithium carbonate and 15 volumes of deionized water according to the solid-liquid ratio of 1:15 (g / mL), first continuously pass high-purity carbon dioxide into the deionized water (control parameters: the deionized water is kept at a constant temperature of 28°C, and the flow rate of carbon dioxide is 0.05 m 3 (h) while applying low frequency ultrasound (30 kHz), then adding crude lithium carbonate uniformly within 45 min, continuously carrying out carbonization reaction to make crude lithium carbonate hydrogenated and precipitated, then removing filter residue by plate frame filtration to obtain lithium bicarbonate carbonization liquid. Content detection is carried out on the obtained lithium bicarbonate carbonization liquid, and the conversion efficiency of lithium carbonate after 45 min carbonization reaction in this step is calculated as 92.8%.

[0049] 2. Continue to add EDTA-Li to the lithium bicarbonate carbonation liquid (add according to the content of calcium, magnesium, and iron ions in the obtained carbonation liquid, and the amount of EDTA-Li added is 1.2 times the total amount of the three ions) to carry out complexation reaction. After the reaction is completed, remove the filter residue by plate and frame filtration again. The obtained filtrate is adsorbed by a macroporous acrylic resin to remove impurities (flow rate: 1.5 mL / min) to obtain a lithium bicarbonate purification liquid. After impurity removal, the removal rate of calcium and magnesium ions in the purification liquid is more than 95%, and the removal rate of iron ions is more than 99% compared with the carbonation liquid before impurity removal.

[0050] 3. Heat the lithium bicarbonate purification liquid to 40°C by microwave, maintain negative pressure of -0.04 MPa by air extraction, and continue to react for 50 min to obtain lithium carbonate crystals. Finally, wash, dry, and store. The loss rate of lithium is 1.53%.

[0051] The chemical composition of the lithium carbonate sample prepared in this example was detected according to GB / T11064-2013, and the results are as follows.

[0052] Table 3

[0053] Component Test result Unit Test method / instrument Li2O3 99.84 ％ Titration method Moisture 0.06 ％ Oven drying method K 13.01 ppm ICP-OES Ca 8.59 ppm ICP-OES Mg 0.59 ppm ICP-OES Fe 2.45 ppm ICP-OES Si 5.22 ppm ICP-OES Magnetic substance 467.16 ppb ICP-OES Cl - ]] 5.03 ppm UV-visible spectrophotometer

[0054] Comparative Example 1

[0055] Take 1 weight of crude lithium carbonate and 16 volumes of deionized water according to the solid-liquid ratio of 1:16 (g / mL). First, stir the crude lithium carbonate and deionized water uniformly to obtain a coarse slurry. Heat the coarse slurry to 26°C, and continuously introduce high-purity carbon dioxide (introduction flow rate: 0.08 m 3 / h) into the coarse slurry while applying low-frequency ultrasound (40 kHz) to continuously carry out carbonation reaction. After 45 min, remove the filter residue by plate and frame filtration to obtain a lithium bicarbonate carbonation liquid. Detect the content of the obtained lithium bicarbonate carbonation liquid, and calculate the conversion efficiency of lithium carbonate after 45 min of carbonation reaction to be 75.6%.

[0056] Comparative Example 2

[0057] Take 1 weight of crude lithium carbonate and 16 volumes of deionized water according to the solid-liquid ratio of 1:16 (g / mL). First, continuously introduce high-purity carbon dioxide into the deionized water (control parameters: deionized water is kept at a constant temperature of 26°C, and the introduction flow rate of carbon dioxide is 0.08 m 3 / h). Then, uniformly add the crude lithium carbonate within 45 min, continuously carry out carbonation reaction to hydrogenate and precipitate the crude lithium carbonate, and then remove the filter residue by plate and frame filtration to obtain a lithium bicarbonate carbonation liquid. Detect the content of the obtained lithium bicarbonate carbonation liquid, and calculate the conversion efficiency of lithium carbonate after 45 min of carbonation reaction to be 82.4%.

[0058] Comparative Example 3

[0059] A method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate, which is different from example 1 in that: in step 2, the bicarbonate lithium carbonization liquid is not subjected to complexation reaction by adding EDTA-Li, but is directly treated by acrylic acid-based macroporous adsorption resin. After impurity removal, the removal rate of calcium, magnesium and iron ions in the purified liquid is more than 90% compared with that in the carbonization liquid before impurity removal, but the adsorption resin is difficult to reduce and regenerate.

[0060] The purified liquid is heated to 50℃ by microwave, and the negative pressure of-0.05MPa is maintained for 60min to obtain lithium carbonate crystals, which are finally washed, dried and stored. The loss rate of lithium is 2.66%.

[0061] The chemical composition of the lithium carbonate sample prepared in the present comparative example is detected according to GB / T11064-2013, and the results are as follows.

[0062] Table 4

[0063]

[0064]

[0065] Comparative example 4

[0066] A method for refining and purifying crude lithium carbonate to produce battery-grade lithium carbonate, which is different from example 1 in that: in step 3, the heating mode of the bicarbonate lithium purification liquid is conventional heating. The loss rate of lithium is 7.82%.

[0067] The chemical composition of the lithium carbonate sample prepared in the present comparative example is detected according to GB / T11064-2013, and the results are as follows.

[0068] Table 5

[0069] Component Test result Unit Test method / instrument Li2O3 99.23 ％ Titration method Moisture 0.07 ％ Oven drying method K 13.24 ppm ICP-OES Ca 22.78 ppm ICP-OES Mg 0.74 ppm ICP-OES Fe 2.62 ppm ICP-OES Si 5.37 ppm ICP-OES Magnetic substance 465.07 ppb ICP-OES Cl - ]] 4.94 ppm UV-visible spectrophotometer Component Test result Unit Test method / instrument Titration method Moisture Oven drying method ppm ICP-OES Ca ppm ICP-OES Mg ppm ICP-OES Fe ppm ICP-OES Si ppm ICP-OES Magnetic substance ppb ICP-OES ppm UV-visible spectrophotometer

[0070] From the above experimental results, it can be seen that the process method has excellent refining and purifying effect, can significantly improve the purity of crude lithium carbonate to obtain high-quality battery-grade lithium carbonate; in addition, the conversion efficiency of the process method is obviously improved, the reaction period of carbonization and pyrolysis in the whole process is greatly shortened, effectively overcoming the shortcomings of the existing hydrogenation decomposition combined with ion adsorption process, and has good practicability.

[0071] The above-described embodiments only express several preferred embodiments of the present application, and the description is more specific and detailed, but not for limiting the present application. It should be noted that for those skilled in the art, the present application can also have various changes and modifications, and any modification, equivalent replacement, improvement, etc. made within the concept and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing battery-grade lithium carbonate by refining and purifying crude lithium carbonate, characterized by, The method comprises the following steps: Step 1: reverse carbonation High-purity carbon dioxide is continuously introduced into deionized water, and then the crude lithium carbonate is uniformly dissolved in the deionized water within 40-60 min to carry out a carbonation reaction, so that the crude lithium carbonate is hydrogenated and precipitated. The filter residue is removed by plate and frame filtration to obtain a lithium bicarbonate carbonation solution; In the reversed carbonization step, the deionized water needs to be kept at a constant temperature of 24-28℃, and pure carbon dioxide is introduced while continuously accompanied by low-frequency ultrasonic treatment, with an ultrasonic frequency of 30-60 kHz, and the flow rate of the continuously introduced pure carbon dioxide is 0.05-0.12 m 3 / h. Step 2: complex impurity removal EDTA-Li is added to the lithium bicarbonate carbonation solution obtained in step 1 to carry out a complexation reaction, and then the filter residue is removed by plate and frame filtration. The obtained filtrate is subjected to ion exchange resin adsorption to remove impurities to obtain a lithium bicarbonate purification solution; Step 3: microwave pyrolysis The lithium bicarbonate purification solution obtained in step 2 is subjected to a pyrolysis reaction by microwave heating. The lithium carbonate crystal obtained by washing and drying is the battery-grade lithium carbonate; wherein, the microwave heating in the microwave pyrolysis step needs to be accompanied by continuous air extraction. Specifically, the negative pressure is maintained at -0.04 ~ -0.06 MPa. The microwave heating temperature is 35-65℃, and the pyrolysis reaction time is 50-90 min.

2. The method of purifying crude lithium carbonate to produce battery-grade lithium carbonate according to claim 1, wherein In the reverse carbonation step, the solid-liquid ratio of crude lithium carbonate to deionized water is 1:(15-19).

3. The method of purifying crude lithium carbonate to produce battery-grade lithium carbonate according to claim 1, wherein In the complex impurity removal step, EDTA-Li is prepared by the reaction of EDTA and LiOH.

4. The method of purifying crude lithium carbonate to produce battery-grade lithium carbonate according to claim 1, wherein In the complex impurity removal step, the amount of EDTA-Li added is 1.2-1.5 times the total amount of calcium, magnesium and iron ions in the lithium bicarbonate carbonation solution.

5. The method of purifying crude lithium carbonate to produce battery-grade lithium carbonate according to claim 1, wherein In the complex impurity removal step, the ion exchange resin is any one of a phenolic cation exchange resin, a styrene cation exchange resin, and an acrylic macroporous adsorption resin.

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