A method for preparing lithium carbonate from lithium-containing chemical solid waste

Abstract

The present invention is to provide a method for preparing lithium carbonate from lithium-containing chemical solid waste, which belongs to the technical field of solid waste recycling. The present invention prepares lithium carbonate from lithium-containing chemical solid waste, the main chemical components of which are Al2O3≥27.79%, SiO2≥22.59, CaO≥19.89, SO3≥9.58, Fe2O3≥4.63, K2O≥3.69, MgO≥2.31, NaO≥0.83, Li2O≥0.45, Cl ‑ ≥0.22, loss on ignition ≥8.26, extract lithium element and make lithium carbonate. The present invention adopts industrial smelting pyrometallurgy-high temperature calcination, has a short process flow, is easy to operate, and the prepared lithium carbonate meets the requirements of Li2CO3-0 in industrial-grade lithium carbonate GB / T11075-2003. The byproduct potassium sulfate produced in the process can be recycled and reused, and the resource utilization rate of solid waste is high. At the same time, if potassium sulfate is not used in the recovery process of the present invention, it also meets the agricultural potassium sulfate standard and can generate other added value.

Description

Technical field:

[0001] The invention relates to the application field of comprehensive recovery and utilization of valuable metals in chemical solid waste, and specifically to a method for preparing lithium carbonate from lithium-containing chemical solid waste. Background technology:

[0002] In recent years, the national economy has developed by leaps and bounds. In the industrial field, industrial production will inevitably produce a large amount of solid waste, which is piled up like a mountain, seriously affecting people's survival and living environment. Now the development of new materials and new energy industries is in full swing, especially chemical solid waste containing lithium elements has also become a kind of available resource. At present, most of the lithium ions recovered in my country are waste lithium batteries, which are mainly recycled by hydrometallurgical methods. Generally, the waste lithium ion batteries are discharged, crushed, sorted and other pre-treatment steps, and then the waste is leached by an acid solution + reducing agent method. After the leachate is treated with impurities, the nickel, cobalt and manganese elements are first recovered by extraction, and finally the lithium element is recovered. At present, there is no method for extracting lithium ions from chemical solid waste containing lithium ions to prepare lithium carbonate, or there is no industrialized, low-cost and efficient method for extracting lithium ions from chemical solid waste containing lithium ions.

[0003] For example, Chinese patent publication number CN114634192A discloses a method and device for recycling black powder from waste lithium-ion batteries, which uses black powder from waste lithium-ion batteries to recover lithium. Specifically, the black powder is added to a solvent and stirred to form a slurry, and then oxygen, sulfur dioxide, and a first inorganic acid solution are added to the slurry for reaction. The slurry after the reaction is filtered to obtain iron phosphate and a first solution; wherein, the first recyclable material includes lithium ions; a soluble carbonate is added to the first solution for reaction, and lithium carbonate is obtained by filtering, and the remainder is a second solution. On the one hand, this invention cannot produce high-quality cathode material precursors, and solvent extraction must be used to separate the leached metals; on the other hand, the lithium concentration contained in the raffinate obtained is low.

[0004] For example, the Chinese patent publication number CN114574705A discloses a method for leaching and separating lithium and valuable metals from waste lithium-ion batteries. The specific steps are as follows: the ternary powder waste containing positive and negative electrodes is evenly mixed with sulfuric acid and deionized water by ball milling, and after two-stage calcination, lithium is directly leached with water or alkali, and valuable metals are extracted by acid leaching. On the one hand, the invention still uses waste lithium batteries as raw materials to prepare lithium carbonate; on the other hand, it does not provide a detailed and feasible solution from an industrial perspective to economically and efficiently extract lithium elements and prepare lithium carbonate.

[0005] The present invention aims at chemical solid waste after industrial production, and adopts an industrial smelting pyrometallurgy-high temperature calcination method to recover lithium ions. The process flow is short and easy to operate. The prepared lithium carbonate meets the requirements of Li2CO3-0 in industrial-grade lithium carbonate GB / T11075-2003. The byproduct potassium sulfate produced in the process can be recycled and utilized, and the resource utilization rate of solid waste is high. At the same time, if the potassium sulfate is not used in the recovery process of the present invention, it also meets the agricultural potassium sulfate standard and can generate other added value. Summary of the invention:

[0006] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0007] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments, and the embodiments described are only some embodiments of the present invention, not all embodiments.

[0008] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0009] The present invention is to provide a method for preparing lithium carbonate from lithium-containing chemical solid waste, wherein the main chemical components of the lithium-containing chemical solid waste are Al2O3≥27.79%, SiO2≥22.59, CaO≥19.89, SO3≥9.58, Fe2O3≥4.63, K2O≥3.69, MgO≥2.31, NaO≥0.83, Li2O≥0.45, Cl - ≥0.22, loss on ignition ≥8.26;

[0010] The following process steps are adopted:

[0011] 1) Mixing ingredients: mixing the lithium-containing chemical solid waste crushed to 60-100 mesh and the calcined additive to obtain a mixture;

[0012] 2) Calcination crystal phase transformation: the mixed material obtained in step 1) is placed in a rotary kiln and calcined at 1000-1050° C. for 2-4 hours to obtain calcined clinker;

[0013] 3) Ball milling leaching: the calcined clinker obtained in step 2) and a lithium ion solution with a concentration of less than 5 g / L are placed in a ball mill in a certain proportion, and ball milled for 2-3 hours at room temperature to obtain a mixed slurry;

[0014] 4) Filtration separation: placing the mixed slurry obtained in step 3) in a belt filter, washing it several times after leaching, and stopping washing when the lithium ion mass concentration in the filter residue is less than or equal to 0.06wt%, to obtain filtrate A;

[0015] 5) filtrate impurity removal: add 35% potassium hydroxide solution to the filtrate A obtained in step 4) until the pH value is above 12, filter to remove metal ions, and obtain a purified filtrate;

[0016] 6) Freezing precipitation and impurity removal: The purified filtrate obtained in step 5) is evaporated, concentrated and crystallized until potassium sulfate crystals are precipitated, then cooled to -5-5°C and frozen for 2 hours, and then centrifuged to separate potassium sulfate to obtain a lithium-rich solution;

[0017] 7) Lithium precipitation: With the lithium-rich solution in step 5) as the base solution, potassium carbonate solution is added dropwise while stirring, and after the addition is completed, the mixture is reacted at 95-100° C. for 2-3 hours, and then centrifuged to obtain a lithium carbonate product.

[0018] The ignition loss is obtained by calcining at 1050°.

[0019] Step 1) The calcination additive components are potassium sulfate and ferric sulfate, and the mass ratio of potassium sulfate and ferric sulfate to lithium-containing chemical solid waste is lithium-containing solid waste: potassium sulfate: ferric sulfate = 70:25:5.

[0020] The certain proportion in step 3) means that after the calcined clinker is mixed with the lithium ion solution with a concentration lower than 5 g / L, the liquid-to-solid mass ratio in the ball mill is 1:1.

[0021] In step 4), the mass concentration of filtrate A is controlled to be greater than or equal to 5 g / L. If the mass concentration of filtrate A is lower than 5 g / L, filtrate A is subjected to step 3) again to increase the mass concentration of filtrate A.

[0022] The potassium sulfate separated by centrifugation in step 6) is dried and recycled as a calcination additive.

[0023] In step 7), the mass concentration of potassium carbonate is 270-280 g / L, and after the lithium-rich solution is dripped with potassium carbonate, the molar ratio of carbonate ions to lithium ions is controlled. It is 8-9:4.

[0024] The solution after centrifugal separation in step 7) is acidified and neutralized with sulfuric acid until the pH value is 6-7, and then added back into filtrate A to carry out step 5) to enrich lithium element.

[0025] The amount of lithium contained in the lithium-containing chemical solid waste generally refers to lithium-containing chemical solid waste with Li2O≥0.45 but less than 1. After adopting the above-mentioned process method of the present invention, lithium elements with high economic value can be extracted to the maximum extent from lithium-containing chemical solid waste with Li2O≥0.45, thereby realizing the recycling of industrial solid waste materials and being environmentally friendly.

[0026] The present invention has the following beneficial effects:

[0027] 1. It fills the gap in extracting lithium from lithium-containing industrial solid waste materials and greatly improves the recycling of industrial solid waste materials.

[0028] 2. Compared with the traditional hydrometallurgy used to extract lithium, the smelting fire method-high temperature calcination method is adopted, and the freezing method is used to precipitate other metal ions to increase the lithium content.

[0029] 3. The actual ratio of carbonate ions to lithium ions is slightly higher than the theoretical value, which improves the purification rate of lithium elements without wasting potassium sulfate raw materials.

[0030] 4. Potassium sulfate and other materials precipitated during the preparation of lithium carbonate can be repeatedly used in industrial production, which is conducive to saving resources. Description of the drawings:

[0031] Figure 1 The present invention is a process flow chart of a method for preparing lithium carbonate from lithium-containing chemical solid waste described in an embodiment of the present invention. Specific implementation method:

[0032] The present invention is further described below with reference to specific examples; the raw materials used in the present invention can be obtained from the market unless otherwise specified, and the following unspecified parts are all measured by mass ratio, mass or weight.

[0033] The present invention is to provide a method for preparing lithium carbonate from lithium-containing chemical solid waste, wherein the main chemical components of the lithium-containing chemical solid waste are Al2O3≥27.79%, SiO2≥22.59, CaO≥19.89, SO3≥9.58, Fe2O3≥4.63, K2O≥3.69, MgO≥2.31, NaO≥0.83, Li2O≥0.45, Cl - ≥0.22, loss on ignition ≥8.26; wherein the loss on ignition is obtained by calcining at 1050°.

[0034] The following process steps are adopted:

[0035] 1) Mixing ingredients: mixing lithium-containing chemical solid waste crushed to 60-100 mesh and calcination additive to obtain a mixture; the calcination additive components are potassium sulfate and ferric sulfate, and the mass ratio of potassium sulfate and ferric sulfate to the lithium-containing chemical solid waste is lithium-containing solid waste: potassium sulfate: ferric sulfate = 70:25:5;

[0036] 2) Calcination crystal phase transformation: the mixed material obtained in step 1) is placed in a rotary kiln and calcined at 1000-1050° C. for 2-4 hours to obtain calcined clinker;

[0037] 3) ball milling leaching: the calcined clinker obtained in step 2) and the lithium ion solution with a concentration of less than 5 g / L are placed in a ball mill in a certain proportion, and ball milled for 2-3 hours at room temperature to obtain a mixed slurry; the certain proportion means that after the calcined clinker and the lithium ion solution with a concentration of less than 5 g / L are mixed, the liquid-to-solid mass ratio in the ball mill is 1:1;

[0038] 4) Filtration separation: placing the mixed slurry obtained in step 3) in a belt filter, washing it several times after leaching, and stopping washing when the mass concentration of lithium ions in the filter residue is less than or equal to 0.06wt%, to obtain filtrate A; controlling the mass concentration of the filtrate A in step 4) to be greater than or equal to 5g / L, and if the mass concentration of the filtrate A is lower than 5g / L, re-performing step 3) on the filtrate A to increase the mass concentration of the filtrate A;

[0039] 5) filtrate impurity removal: add 35% potassium hydroxide solution to the filtrate A obtained in step 4) until the pH value is above 12, filter to remove metal ions, and obtain a purified filtrate;

[0040] 6) Freezing precipitation and impurity removal: The purified filtrate obtained in step 5) is evaporated, concentrated and crystallized until potassium sulfate crystals are precipitated, then cooled to -5-5°C and frozen for 2 hours, and then centrifuged to separate potassium sulfate to obtain a lithium-rich solution; the potassium sulfate separated by centrifugation is dried and recycled as a calcination additive;

[0041] 7) Lithium precipitation: With the lithium-rich solution in step 5) as the base solution, potassium carbonate solution is added dropwise while stirring, reacted at 95-100°C for 2-3h, and then centrifuged to obtain lithium carbonate product. The mass concentration of potassium carbonate is 270-280g / L, and after the lithium-rich solution is added with potassium carbonate, the molar ratio of carbonate ions to lithium ions is controlled. The solution after centrifugation is acidified and neutralized with sulfuric acid until the pH value is 6-7, and then added back into the filtrate A to carry out step 5) to enrich the lithium element.

[0042] Embodiment 1:

[0043] The present invention is to provide a method for preparing lithium carbonate from lithium-containing chemical solid waste. Unless otherwise specified, all raw materials used in the present invention can be obtained from the market. The following unspecified parts are all based on mass ratio, mass or weight. The following is an implementation method of the embodiment as follows:

[0044] The main chemical components of lithium-containing chemical solid waste are Al2O3 (27.79%), SiO2 (22.59%), CaO (19.89%), SO3 (9.58%), Fe2O3 (4.63%), K2O (3.69%), MgO (2.31%), NaO (0.83%), Li2O (0.45%), and Cl - is 0.22, and the loss on ignition is 8.26; wherein the loss on ignition is obtained by calcining at 1050°,

[0045] 1) Mixing ingredients: mixing lithium-containing chemical solid waste crushed to 80 mesh and a calcination additive to obtain a mixture; the calcination additive comprises potassium sulfate and ferric sulfate, and the mass ratio of the potassium sulfate and the lithium-containing chemical solid waste is lithium-containing solid waste: potassium sulfate: ferric sulfate = 700:250:50;

[0046] 2) Calcination crystal phase transformation: the mixture obtained in step 1) is placed in a rotary kiln and calcined at 1050° C. for 3 h to obtain 200 g of calcined clinker;

[0047] 3) Ball milling leaching: The calcined clinker obtained in step 2) and a lithium ion solution with a concentration lower than 5 g / L are placed in a ball mill in a certain proportion, and ball milled for 3 hours at room temperature to obtain a mixed slurry; the certain proportion means that after the calcined clinker and the lithium ion solution with a concentration lower than 5 g / L are mixed, the liquid-to-solid mass ratio in the ball mill is 1:1.

[0048] 4) Filtration separation: the mixed slurry obtained in step 3) is placed in a belt filter, and after one leaching, it is washed twice to obtain a lithium solution with a lithium ion mass concentration of 5.55 g / L, wherein 167 ml of filtrate A and 128 g of filter residue B are obtained, 88 ml of washing water are obtained, and the lithium ion mass concentration of filter residue B is 0.05 wt%;

[0049] 5) filtrate impurity removal: add 35% potassium hydroxide solution to the filtrate A obtained in step 4) until the pH value is 12, filter to remove metal ions, and obtain a purified filtrate;

[0050] 6) Freezing precipitation and impurity removal: The purified filtrate obtained in step 5) is evaporated, concentrated and crystallized until potassium sulfate crystals are precipitated, then cooled to -5°C and frozen for 2 hours, and then the potassium sulfate is centrifuged to obtain 1536 ml of lithium-rich solution with a lithium ion concentration of 17.25 g / L; the potassium sulfate separated by centrifugation is dried and recycled as a calcination additive.

[0051] Step 6) Chemical composition analysis results of lithium-rich solution (Li, SO4, K, Na units are g / L, others are ppm)

[0052]

[0053] 7) Lithium precipitation: With the lithium-rich solution in step 5) as the base liquid, potassium carbonate solution is added dropwise while stirring, wherein the mass concentration of potassium carbonate is 275g / L and the amount added is 217ml. After the addition, the reaction is carried out at 95°C for 2h, and then centrifuged to obtain a lithium carbonate product. The solution after centrifugation is acidified and neutralized with sulfuric acid until the pH is 7, and then it can be re-added to the filtrate A to carry out step 5) to enrich the lithium element.

[0054] According to this embodiment, the chemical composition analysis results of the prepared lithium carbonate are Li, SO4, K, Na in g / L, and other components in ppm.

[0055]

[0056] Comparative Example 1:

[0057] The present invention is to provide a method for preparing lithium carbonate from lithium-containing chemical solid waste. The embodiment is the same as embodiment 1 or the above embodiment except for the following description. In this embodiment, the crystallization is not precipitated by freezing method.

[0058] The main chemical components of lithium-containing chemical solid waste are Al2O3 (27.79%), SiO2 (22.59%), CaO (19.89%), SO3 (9.58%), Fe2O3 (4.63%), K2O (3.69%), MgO (2.31%), NaO (0.83%), Li2O (0.45%), and Cl - is 0.22, and the loss on ignition is 8.26; wherein the loss on ignition is obtained by calcining at 1050°,

[0059] 1) Mixing ingredients: mixing lithium-containing chemical solid waste crushed to 80 mesh and a calcination additive to obtain a mixture; the calcination additive comprises potassium sulfate and ferric sulfate, and the mass ratio of the potassium sulfate and the lithium-containing chemical solid waste is lithium-containing solid waste: potassium sulfate: ferric sulfate = 700:250:50;

[0060] 2) Calcination crystal phase transformation: the mixture obtained in step 1) is placed in a rotary kiln and calcined at 1050° C. for 3 h to obtain 200 g of calcined clinker;

[0061] 3) ball milling leaching: placing the calcined clinker obtained in step 2) and a lithium ion solution with a concentration of less than 5 g / L in a ball mill according to a certain ratio, and ball milling for 3 hours at room temperature to obtain a mixed slurry; the certain ratio means that after the calcined clinker and the lithium ion solution with a concentration of less than 5 g / L are mixed, the liquid-to-solid mass ratio in the ball mill is 1:1;

[0062] 4) Filtration separation: the mixed slurry obtained in step 3) is placed in a belt filter, and after one leaching, it is washed twice to obtain a lithium solution with a lithium ion mass concentration of 5.55 g / L, wherein 167 ml of filtrate A and 128 g of filter residue B are obtained, 88 ml of washing water are obtained, and the lithium ion mass concentration of filter residue B is 0.05 wt%;

[0063] 5) filtrate impurity removal: add 35% potassium hydroxide solution to the filtrate A obtained in step 4) until the pH value is 12, filter to remove metal ions, and obtain a purified filtrate;

[0064] 6) Freezing precipitation and impurity removal: The purified filtrate obtained in step 5) is evaporated, concentrated and crystallized until potassium sulfate crystals are precipitated, then cooled to room temperature, and then centrifuged to separate potassium sulfate to obtain 1536 ml of lithium-rich solution with a lithium ion concentration of 17.25 g / L; the potassium sulfate separated by centrifugation is dried and recycled as a calcination additive;

[0065] Step 6) Chemical composition analysis results of lithium-rich solution (Li, SO4, K, Na units are g / L, others are ppm)

[0066]

[0067] 7) Lithium precipitation: With the lithium-rich solution in step 5) as the base liquid, potassium carbonate solution is added dropwise while stirring, wherein the mass concentration of potassium carbonate is 275g / L and the amount added is 217ml. After the addition, the reaction is carried out at 95°C for 2h, and then centrifuged to obtain a lithium carbonate product. The solution after centrifugation is acidified and neutralized with sulfuric acid until the pH is 7, and then it can be re-added to the filtrate A to carry out step 5) to enrich the lithium element.

[0068] According to this embodiment, the chemical composition analysis results of the prepared lithium carbonate are Li, SO4, K, Na in g / L, and other components in ppm.

[0069]

[0070] Comparative Example 2:

[0071] The present invention is to provide a method for preparing lithium carbonate from lithium-containing chemical solid waste. The embodiment is the same as embodiment 1 or the above embodiment except for the following description. This embodiment is an embodiment for adjusting the molar ratio of carbonate ions to lithium ions in step 7), as follows:

[0072] The main chemical components of lithium-containing chemical solid waste are Al2O3 (27.79%), SiO2 (22.59%), CaO (19.89%), SO3 (9.58%), Fe2O3 (4.63%), K2O (3.69%), MgO (2.31%), NaO (0.83%), Li2O (0.45%), and Cl - is 0.22, and the loss on ignition is 8.26; wherein the loss on ignition is obtained by calcining at 1050°,

[0073] 1) Mixing ingredients: mixing lithium-containing chemical solid waste crushed to 80 mesh and a calcination additive to obtain a mixture; the calcination additive comprises potassium sulfate and ferric sulfate, and the mass ratio of the potassium sulfate and the lithium-containing chemical solid waste is lithium-containing solid waste: potassium sulfate: ferric sulfate = 700:250:50;

[0074] 2) Calcination crystal phase transformation: the mixture obtained in step 1) is placed in a rotary kiln and calcined at 1050° C. for 3 h to obtain 200 g of calcined clinker;

[0075] 3) Ball milling leaching: The calcined clinker obtained in step 2) and a lithium ion solution with a concentration lower than 5 g / L are placed in a ball mill in a certain proportion, and ball milled for 3 hours at room temperature to obtain a mixed slurry; the certain proportion means that after the calcined clinker and the lithium ion solution with a concentration lower than 5 g / L are mixed, the liquid-to-solid mass ratio in the ball mill is 1:1.

[0076] 4) Filtration separation: the mixed slurry obtained in step 3) is placed in a belt filter, and after one leaching, it is washed twice to obtain a lithium solution with a lithium ion mass concentration of 5.55 g / L, wherein 167 ml of filtrate A and 128 g of filter residue B are obtained, 88 ml of washing water are obtained, and the lithium ion mass concentration of filter residue B is 0.05 wt%;

[0077] 5) filtrate impurity removal: add 35% potassium hydroxide solution to the filtrate A obtained in step 4) until the pH value is 12, filter to remove metal ions, and obtain a purified filtrate;

[0078] 6) Freezing precipitation and impurity removal: The purified filtrate obtained in step 5) is evaporated, concentrated and crystallized until potassium sulfate crystals are precipitated, then cooled to -5°C and frozen for 2 hours, and then the potassium sulfate is centrifuged to obtain 1536 ml of lithium-rich solution with a lithium ion concentration of 17.25 g / L; the potassium sulfate separated by centrifugation is dried and recycled as a calcination additive.

[0079] Step 6) Chemical composition analysis results of lithium-rich solution (Li, SO4, K, Na units are g / L, others are ppm)

[0080]

[0081] 7) Lithium precipitation: With the lithium-rich solution in step 5) as the base liquid, potassium carbonate solution is added dropwise while stirring, wherein the mass concentration of potassium carbonate is 275g / L and the amount added is 144ml. After the addition, the mixture is reacted at 95°C for 2h, and then centrifuged to obtain a lithium carbonate product. The solution after centrifugation is acidified and neutralized with sulfuric acid until the pH is 7, and then it can be re-added to the filtrate A to carry out step 5) to enrich the lithium element.

[0082] According to this embodiment, the chemical composition analysis results of the prepared lithium carbonate are Li, SO4, K, Na in g / L, and other components in ppm.

[0083]

[0084] The above embodiments are some preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A method for preparing lithium carbonate from lithium-containing chemical solid waste, wherein the main chemical components of the lithium-containing chemical solid waste are Al2O3≥27.79%, SiO2≥22.59, CaO≥19.89, SO3≥9.58, Fe2O3≥4.63, K2O≥3.69, MgO≥2.31, NaO≥0.83, Li2O≥0.45, Cl - ≥0.22, loss on ignition ≥8.26; It is characterized in that The following process steps are adopted: 1) Mixing ingredients: mixing lithium-containing chemical solid waste crushed to 60-100 mesh and calcination additive to obtain a mixture; the calcination additive components are potassium sulfate and ferric sulfate, and the mass ratio of potassium sulfate and ferric sulfate to the lithium-containing chemical solid waste is lithium-containing solid waste: potassium sulfate: ferric sulfate = 70:25:5; 2) Calcination crystal phase transformation: the mixed material obtained in step 1) is placed in a rotary kiln and calcined at 1000-1050° C. for 2-4 hours to obtain calcined clinker; 3) Ball milling leaching: the calcined clinker obtained in step 2) and a lithium ion solution with a concentration of less than 5 g / L are placed in a ball mill in a certain proportion, and ball milled for 2-3 hours at room temperature to obtain a mixed slurry; 4) Filtration separation: placing the mixed slurry obtained in step 3) in a belt filter, washing it several times after leaching, and stopping washing when the lithium ion mass concentration in the filter residue is less than or equal to 0.06wt%, to obtain filtrate A; 5) filtrate impurity removal: add 35% potassium hydroxide solution to the filtrate A obtained in step 4) until the pH value is above 12, filter to remove metal ions, and obtain a purified filtrate; 6) Freezing precipitation and impurity removal: The purified filtrate obtained in step 5) is evaporated, concentrated and crystallized until potassium sulfate crystals are precipitated, then cooled to -5-5°C and frozen for 2 hours, and then centrifuged to separate potassium sulfate to obtain a lithium-rich solution; 7) Lithium precipitation: With the lithium-rich solution in step 5) as the base solution, potassium carbonate solution is added dropwise while stirring, and after the addition is completed, the mixture is reacted at 95-100° C. for 2-3 hours, and then centrifuged to obtain a lithium carbonate product.

2. A method for preparing lithium carbonate from lithium-containing chemical solid waste according to claim 1, characterized in that The certain proportion in step 3) means that after the calcined clinker is mixed with the lithium ion solution with a concentration lower than 5 g / L, the liquid-to-solid mass ratio in the ball mill is 1:

1.

3. A method for preparing lithium carbonate from lithium-containing chemical solid waste according to claim 1, characterized in that In step 4), the mass concentration of filtrate A is controlled to be greater than or equal to 5 g / L. If the mass concentration of filtrate A is lower than 5 g / L, filtrate A is subjected to step 3) again to increase the mass concentration of filtrate A.

4. A method for preparing lithium carbonate from lithium-containing chemical solid waste according to claim 1, characterized in that The potassium sulfate separated by centrifugation in step 6) is dried and recycled as a calcination additive.

5. A method for preparing lithium carbonate from lithium-containing chemical solid waste according to claim 1, characterized in that In step 7), the mass concentration of potassium carbonate is 270-280 g / L, and after the lithium-rich solution is dripped with potassium carbonate, the molar ratio of carbonate ions to lithium ions is controlled. It is 8-9:

4.

6. A method for preparing lithium carbonate from lithium-containing chemical solid waste according to claim 1, characterized in that The solution after centrifugal separation in step 7) is acidified and neutralized with sulfuric acid until the pH value is 6-7, and then added back into filtrate A to carry out step 5) to enrich lithium element.

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