Crystallization method for separating lithium carbonate from mixed mother liquor of lithium chloride and sodium chloride through reaction

Abstract

The invention discloses a crystallization method for separating lithium carbonate from a mixed mother solution of lithium chloride and sodium chloride through reaction, which comprises the following steps: evaporating and crystallizing a raw material solution for 2-4 hours at the concentration ratio of 4-5 times to obtain a turbid liquid containing sodium chloride crystals; feeding the crystallized turbid liquid into a continuous centrifugal device from the crystallizer, carrying out solid-liquid separation, washing and drying to obtain a sodium chloride product; adding the prepared saturated sodium carbonate solution into the filtered mother solution for reaction crystallization, continuously stirring in the reaction process, and continuously reacting after the operation is finished to completely react lithium chloride, so as to obtain a suspension containing lithium carbonate crystals; and filtering, washing and drying the reacted turbid liquid to obtain a lithium carbonate product. The filtered mother liquor is evaporated and concentrated by 5-8 times to obtain turbid liquid containing sodium chloride crystals, the crystallized turbid liquid enters a continuous centrifugal device from a crystallizer to be subjected to solid-liquid separation, washing and drying to obtain the sodium chloride crystals, and a liquid phase can be continuously subjected to a reaction crystallization step.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical separation, and in particular relates to a crystallization separation method for a mixed solution of lithium chloride and sodium chloride. Background Art

[0002] Lithium-ion batteries have many advantages, such as high energy density, high discharge platform, low self-discharge effect, high charge and discharge efficiency and long cycle life. They are widely used in power batteries, electrochemical energy storage, portable electronic devices and other fields. Nowadays, with the expansion of its production and sales and the expansion of the energy storage market, the number of scrapped lithium-ion batteries has increased dramatically. The indiscriminate disposal of waste batteries has become an environmental problem that needs to be solved urgently, because they contain heavy metals and chemicals, which pollute the soil and water, and endanger the ecology and human health.

[0003] If waste lithium-ion batteries cannot be effectively treated, they will not only pollute and damage the environment, but also lose a large amount of metal resources. In order to protect the environment and realize the comprehensive utilization of resources, it is necessary to reasonably treat and dispose of waste lithium batteries to recover metal elements such as lithium, cobalt, nickel, manganese, and copper ions contained therein. At present, the recycling of waste lithium batteries is mainly concentrated in the recycling and treatment of positive electrode materials, mainly including solid phase method, acid leaching-precipitation method, etc. The solid phase method has the advantages of short process flow, simple process conditions, and less equipment required, but the electrochemical performance of the positive electrode material regenerated by this method is poor and needs to be further improved. In this way, the acid leaching-precipitation method is a better choice. In the process of recovering lithium elements in this process, a mixed solution of lithium chloride and sodium chloride will be produced. How to separate sodium chloride and lithium chloride from the mixed solution has become one of the key steps in the recovery of metal elements in waste lithium iron phosphate batteries. Summary of the invention

[0004] In order to better separate the lithium chloride and sodium chloride mixed solution by crystallization, the present invention separates and purifies industrial-grade sodium chloride and lithium carbonate products by coupling evaporative crystallization and reactive crystallization. The present invention discloses a crystallization separation method, which utilizes the ternary water-salt system NaCl-LiCl-H 2 O phase diagram, and a cyclic coupling process of evaporation concentration-reaction crystallization-evaporation concentration was formulated. Compared with the reported separation process of extraction residue, the separation process of the present invention can obtain industrial-grade sodium chloride and industrial-grade lithium carbonate products. The two products have large particle sizes and uniform particle size distribution, the product purity reaches more than 98.5%, and the process repeatability is good. In addition, this method does not require the use of additional extractants, and the process is green and efficient. The specific technical scheme is as follows:

[0005] A crystallization method for separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride comprises the following steps:

[0006] Step 1, evaporating and crystallizing the raw material solution for 2-4 hours, and concentrating to obtain a suspension containing sodium chloride crystals;

[0007] Step 2: Feed the crystallized suspension from the crystallizer into a continuous centrifugal device for solid-liquid separation. After washing and drying, sodium chloride crystals are obtained.

[0008] Step 3: Add the prepared saturated sodium carbonate solution to the filtered mother liquor for reaction crystallization. Stir continuously during the reaction process and continue the reaction for 2 hours after the stirring ends to completely react lithium chloride, obtaining a suspension containing lithium carbonate crystals.

[0009] Step 4: Filter, wash, and dry the suspension containing lithium carbonate crystals to obtain lithium carbonate.

[0010] Step 5: Evaporate and crystallize the filtered mother liquor for 2 - 4 hours to obtain a suspension containing sodium chloride crystals after concentration.

[0011] Further, the raw material liquid in Step 1 contains approximately 9 - 12% sodium chloride, approximately 9 - 12% lithium chloride, and the concentration multiple is 4 - 5 times.

[0012] Further, the evaporation temperature in Step 1 is 70 - 80°C.

[0013] Further, the drying conditions in Step 2 are vacuum drying at 30 - 40°C for 3 - 5 hours.

[0014] Further, the reaction crystallization time in Step 3 is 3 - 4 hours.

[0015] Further, the drying conditions in Step 4 are vacuum drying at 50 - 60°C for 3 - 5 hours.

[0016] Further, after evaporation in Step 5, the sodium chloride content is approximately 9 - 12%, the lithium chloride content is approximately 9 - 12%, and the concentration multiple is 5 - 8 times.

[0017] This invention is based on the NaCl - LiCl - H 2 O ternary phase diagram. Combining with the specific composition of the mixed solution of lithium chloride and sodium chloride, the optimal crystallization separation principle is studied and successfully applied to the separation and purification of the mixed solution of lithium chloride and sodium chloride, obtaining industrial - grade sodium chloride and lithium carbonate, which is the technical innovation of this invention. That is, first, high - purity sodium chloride is separated and purified by evaporation crystallization, then the mother liquor is concentrated, and then an appropriate amount of sodium carbonate is added to the mother liquor enriched with lithium chloride for reaction crystallization to separate and purify industrial - grade lithium carbonate. Therefore, the separation process of this invention can not only obtain two industrial - grade inorganic salt products, but also maximize the treatment of the mixed solution and reduce resource waste.

[0018] The crystallization separation method of the evaporation concentration-reaction crystallization-evaporation concentration cyclic coupling process described in the present invention can separate a mixed solution of sodium chloride and lithium chloride, prepare industrial-grade sodium chloride and lithium carbonate products. The purity of both products can reach over 98.5%, the primary recovery rate of sodium chloride can reach over 75%, and the primary recovery rate of lithium element can reach over 75%. The crystal particles of both products are large in size and have a uniform particle size distribution. The crystallization separation method of the present invention can separate a mixed solution of sodium chloride and lithium chloride, realize the recycling of inorganic salt resources, and is beneficial to environmental protection and resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic flow chart of the crystallization method for reacting and separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride according to the present invention;

[0020] Figure 2 is a diagram of the lithium carbonate crystals prepared in Example 1; DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be further described below with reference to the accompanying drawings.

[0022] As Figure 1 shown, the crystallization method for reacting and separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride according to the present invention includes the following steps:

[0023] Step 1: Evaporate and crystallize the raw material liquid for 2 - 4 hours to obtain a suspension containing sodium chloride crystals after concentration;

[0024] Step 2: Feed the suspension after crystallization into a continuous centrifugation device for solid-liquid separation, and obtain sodium chloride crystals after washing and drying;

[0025] Step 3: Add the prepared saturated sodium carbonate solution to the filtered mother liquor for reaction crystallization. Continuously stir during the reaction process, and continue to react for 2 hours after the stirring ends to completely react lithium chloride, obtaining a suspension containing lithium carbonate crystals;

[0026] Step 4: Filter, wash, and dry the suspension containing lithium carbonate crystals to obtain lithium carbonate.

[0027] Step 5: Evaporate and crystallize the filtered mother liquor for 2 - 4 hours to obtain a suspension containing sodium chloride crystals after concentration.

[0028] Furthermore, in the raw material liquid of Step 1, the sodium chloride content is about 9 - 12%, the lithium chloride content is about 9 - 12%, and the concentration ratio is 4 - 5 times.

[0029] Example 1

[0030] The sodium chloride content in the raw material liquid is about 9%, and the lithium chloride content is about 9.8%. First, add the raw material liquid to the reaction kettle, evaporate and crystallize at 70 °C for 2 hours, with a concentration ratio of 5 times. Filter and wash the obtained suspension after evaporation, and dry it under vacuum conditions at 40 °C for 3.2 hours to obtain sodium chloride products with a product purity of 98.7% and a primary recovery rate of sodium chloride of 68.3%. Then, add the prepared saturated sodium carbonate solution to the filtered mother liquor for reaction crystallization. Continuously stir during the reaction process, and continue the reaction for 3.4 hours after the operation ends to completely react the lithium chloride, obtaining a suspension containing lithium carbonate crystals. Filter and wash the obtained suspension after the reaction, and dry it under vacuum conditions at 40 °C for 4 hours to obtain lithium carbonate products with a product purity of 98.7% and a primary recovery rate of lithium element of 77.2%.

[0031] The prepared lithium carbonate crystals are as Figure 2 shown.

[0032] Example 2

[0033] The sodium chloride content in the raw material liquid is about 10.2%, and the lithium chloride content is about 12%. First, add the raw material liquid to the reaction kettle, evaporate and crystallize at 75 °C for 2 hours, with a concentration ratio of 4.5 times. Filter and wash the obtained suspension after evaporation, and dry it under vacuum conditions at 35 °C for 3.5 hours to obtain sodium chloride products with a product purity of 98.6% and a primary recovery rate of sodium chloride of 67.9%. Then, add the prepared saturated sodium carbonate solution to the filtered mother liquor for reaction crystallization. Continuously stir during the reaction process, and continue the reaction for 3 hours after the operation ends to completely react the lithium chloride, obtaining a suspension containing lithium carbonate crystals. Filter and wash the obtained suspension after the reaction, and dry it under vacuum conditions at 30 °C for 3.6 hours to obtain lithium carbonate products with a product purity of 98.9% and a primary recovery rate of lithium element of 76.7%.

[0034] Example 3

[0035] The sodium chloride content in the raw material liquid is about 11.6%, and the lithium chloride content is about 9%. First, add the raw material liquid to the reaction kettle, evaporate and crystallize at 80 °C for 2 hours, with a concentration ratio of 4.5 times. Filter and wash the obtained suspension after evaporation, and dry it under vacuum conditions at 30 °C for 3 hours to obtain sodium chloride products with a product purity of 98.9% and a primary recovery rate of sodium chloride of 67.4%. Then, add the prepared saturated sodium carbonate solution to the filtered mother liquor for reaction crystallization. Continuously stir during the reaction process, and continue the reaction for 4 hours after the operation ends to completely react the lithium chloride, obtaining a suspension containing lithium carbonate crystals. Filter and wash the obtained suspension after the reaction, and dry it under vacuum conditions at 40 °C for 5 hours to obtain lithium carbonate products with a product purity of 98.6% and a primary recovery rate of lithium element of 78.4%.

[0036] Example 4

[0037] The content of sodium chloride in the raw material liquid is about 10.4%, and the content of lithium chloride is about 9.8%. First, the raw material liquid is added to a reaction kettle, evaporated and crystallized at 78°C for 2 hours, and the concentration ratio is 4 times. The suspension obtained after evaporation is filtered and washed, and dried under vacuum conditions at 40°C for 5 hours to obtain sodium chloride products with a product purity of 98.5% and a primary recovery rate of sodium chloride of 66.8%. Then, the prepared saturated sodium carbonate solution is added to the filtered mother liquor for reaction crystallization. During the reaction process, continuous stirring is carried out, and the reaction continues for 3.8 hours after the operation ends to completely react lithium chloride to obtain a suspension containing lithium carbonate crystals. The suspension obtained after the reaction is filtered and washed, and dried under vacuum conditions at 50°C for 3 hours to obtain lithium carbonate products with a product purity of 98.7% and a primary recovery rate of lithium element of 77.9%.

[0038] The crystallization separation method of the lithium chloride and sodium chloride mixed solution disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the content herein and appropriately changing links such as raw materials and process parameters. The method and products of the present invention have been described through preferred embodiments. Those skilled in the art can obviously make changes or appropriate modifications and combinations to the methods and products described herein without departing from the content, spirit and scope of the present invention to implement the technology of the present invention. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the spirit, scope and content of the present invention.

Claims

1. A crystallization method for separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride, characterized in that The steps include: Step 1, evaporating and crystallizing the raw material solution for 2-4 hours, and concentrating to obtain a suspension containing sodium chloride crystals; Step 2, the crystallized suspension is passed from the crystallizer into a continuous centrifugal device for solid-liquid separation, and sodium chloride crystals are obtained after washing and drying; Step 3, adding the prepared saturated sodium carbonate solution to the filtered mother liquor for reaction and crystallization, stirring continuously during the reaction, and continuing the reaction for 2 hours after the stirring is completed, so that the lithium chloride reacts completely to obtain a suspension containing lithium carbonate crystals; Step 4, filtering, washing and drying the suspension containing lithium carbonate crystals to obtain lithium carbonate; Step 5: evaporate and crystallize the filtered mother liquor for 2-4 hours, and concentrate to obtain a suspension containing sodium chloride crystals.

2. The crystallization method for separating lithium carbonate by reaction from lithium chloride and sodium chloride mixed mother liquor as claimed in claim 1, characterized in that: The raw material liquid in step 1 contains about 9-12% sodium chloride, about 9-12% lithium chloride, and a concentration ratio of 4-5 times.

3. The crystallization method for separating lithium carbonate by reaction from lithium chloride and sodium chloride mixed mother liquor as claimed in claim 1, characterized in that: The evaporation temperature in step 1 is 70-80°C.

4. The crystallization method for separating lithium carbonate by reaction from a mixed mother liquor of lithium chloride and sodium chloride as claimed in claim 1, characterized in that: The drying condition in step 2 is vacuum drying at 30-40° C. for 3-5 hours.

5. The crystallization method for separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride as claimed in claim 1, characterized in that: In the step 3, the reaction crystallization takes 3-4 hours.

6. The crystallization method for separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride as claimed in claim 1, wherein: The drying condition in step 4 is vacuum drying at 50-60° C. for 3-5 hours.

7. The crystallization method for separating lithium carbonate from a mixed mother liquor of lithium chloride and sodium chloride as claimed in claim 1, characterized in that: After evaporation in step 5, the sodium chloride content is about 9-12%, the lithium chloride content is about 9-12%, and the concentration ratio is 5-8 times.

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