Process for producing lithium carbonate through continuous feeding and discharging

Abstract

The invention relates to the technical field of metallurgical processes, in particular to a process for producing lithium carbonate through continuous feeding and discharging. According to the process for producing lithium carbonate through continuous feeding and discharging, multi-kettle parallel batch operation is adopted, continuous feeding, uniform mixing and functional differentiation of the reaction kettles and the feeding kettles are guaranteed, uniform growth of lithium carbonate crystals is promoted by precisely regulating and controlling reaction conditions, and the product quality is favorably controlled. The dynamic sedimentation design of the sedimentation kettle is adopted, stirring, dispersing and standing are performed, and top clear liquid overflow is matched, so that the follow-up separation treatment amount is reduced, and the equipment load is reduced. The material retention time can be adjusted in real time through management and control, the particle size of lithium carbonate is flexibly regulated and controlled, market requirements are met, and the overall production efficiency is improved. In conclusion, the process realizes continuity, high efficiency and quality controllability of lithium carbonate production, and provides reliable technical support for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of metallurgical process technology, and in particular to a process for producing lithium carbonate through continuous feeding and discharging. Background Technology

[0002] The selection of lithium carbonate production processes has always revolved around the characteristics of raw materials, resulting in three major technological systems: ore-based lithium extraction, salt lake-based lithium extraction, and clay-based lithium extraction. Among these, ore-based lithium extraction, using spodumene and lepidolite as core raw materials, has become the mainstream choice for regions like Jiangxi that lack salt lake resources due to its stable raw material supply and lack of climate and geographical limitations. Its process is highly mature, especially the spodumene sulfuric acid process, which can stably produce battery-grade products through steps such as transformation roasting and acid leaching. However, it suffers from high energy consumption and significant solid waste treatment pressure, with a cost per ton exceeding that of the salt lake process by more than 30%.

[0003] Lithium extraction from salt lakes relies on over 70% of the world's lithium reserves, holding a dominant position in regions such as Qinghai and the "Lithium Triangle" in South America. This process offers significant cost advantages, but its effectiveness is heavily constrained by brine type: chloride-type salt lakes can efficiently extract lithium using solvent extraction, while sulfate-type salt lakes, due to their high magnesium-to-lithium ratio, require magnesium removal through precipitation, significantly increasing process complexity. Furthermore, lithium extraction from salt lakes depends on solar evaporation in arid climates, with efficiency dropping by more than 50% in winter, highlighting significant geographical limitations.

[0004] Current lithium carbonate production processes are evolving towards "low cost, low pollution, and high purity." Technological upgrades in lithium extraction from salt lakes focus on treating brine with a high magnesium-to-lithium ratio. The application of new adsorption materials can increase the magnesium-to-lithium separation coefficient to over 1000, and Qinghai Salt Lake has already achieved a breakthrough in production capacity of tens of thousands of tons. Lithium extraction from ore utilizes technologies such as waste heat recovery and waste acid recycling to reduce overall energy consumption by 20%. The comprehensive recovery of potassium, rubidium, and cesium in lithium extraction from lepidolite can increase profit per ton by over 5000 yuan.

[0005] In the future, as the purity requirements for lithium carbonate in power batteries increase, the process will focus more on refined purification, and the integration of new technologies such as membrane separation and electrochemical deposition is expected to further shorten the process. At the same time, low-carbon production is becoming an inevitable trend, and photovoltaic-driven salt lake evaporation and hydrogen-powered ore roasting to replace fossil fuels will drive the industry towards green manufacturing. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a continuous feed-discharge process for producing lithium carbonate, which addresses the shortcomings of the prior art. The process is designed to achieve continuous production of raw materials and products at a controllable flow rate. The process includes reflux during the reaction to control the reaction time of the materials and to control the particle size of lithium carbonate, thereby improving product quality.

[0007] This invention provides a continuous feed-discharge process for producing lithium carbonate, the specific steps of which are as follows:

[0008] S1. Add refined lithium sulfate solution and refined sodium carbonate solution to the feeding vessel, mix well to obtain a mixture;

[0009] S2. Take the mixture prepared in S1 and the purified lithium sulfate solution and add them to the reaction vessel to react fully to obtain the intermediate product;

[0010] S3. Take the intermediate product prepared in S2 and transfer it to the sedimentation tank. After sedimentation and separation, lithium carbonate slurry and lithium precipitation solution are obtained.

[0011] S4. Take a portion of the lithium precipitation solution prepared in S3 and return it to the feeding vessel and the reaction vessel.

[0012] According to the continuous feed-discharge process for producing lithium carbonate provided by the present invention, in S1, the lithium concentration of the refined lithium sulfate solution is 10-25 g / L, and the concentration of the refined sodium carbonate solution is 260-300 g / L; the molar ratio of lithium sulfate in the refined lithium sulfate solution flowing per unit time to sodium carbonate in the refined sodium carbonate solution flowing per unit time is 1:(1-1.1); the flow rate of the refined sodium carbonate solution added to the feeding vessel is 100%; and the refined lithium sulfate solution is added to the feeding vessel at least twice according to the flow rate.

[0013] According to the continuous feed-discharge process for producing lithium carbonate provided by the present invention, the refined lithium sulfate solution and refined sodium carbonate solution in S2 can be fed continuously by convection, and the lithium carbonate slurry and lithium precipitation solution produced in S3 can be discharged continuously. The solid content of the lithium carbonate slurry in S3 is >5%, and the return amount of the lithium precipitation solution in S4 is ≤10% of the total amount of lithium precipitation solution produced.

[0014] According to the continuous feeding and discharging process for producing lithium carbonate provided by the present invention, a stirrer is provided in the feeding vessel, the reaction vessel and the settling vessel, and multiple reflux layers are provided on the peripheral sidewalls of the feeding vessel, the reaction vessel and the settling vessel. The top and bottom of the feeding vessel, the reaction vessel and the settling vessel are respectively provided with a feed inlet and a discharge outlet.

[0015] According to the continuous feeding and discharging process for producing lithium carbonate provided by the present invention, the upper sidewall of the settling tank in S3 is further provided with a first outlet, the first outlet being used to discharge the lithium carbonate precipitate, and the discharge port of the settling tank being used to discharge the lithium carbonate slurry.

[0016] According to the continuous feed-discharge process for producing lithium carbonate provided by the present invention, the multiple reflux layers are connected by connecting pipes, and a heating device is provided in the middle of the connecting pipes. The temperature in the feeding vessel in S1 is 70-80°C, the temperature in the reaction vessel in S2 is 80-90°C, and the temperature in the settling vessel in S3 is 90-95°C.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention provides a continuous feed-discharge process for producing lithium carbonate. It employs multiple reactors operating in parallel in batches to ensure continuous feeding and uniform mixing. The reactor and feeding vessel have distinct functions, and precise control of reaction conditions promotes uniform lithium carbonate crystal growth, facilitating product quality control. The dynamic settling design of the settling vessel, with stirring, dispersion, and subsequent settling, combined with top clear liquid overflow, reduces subsequent separation and processing volume, lowering equipment load. The control system allows for real-time adjustment of material residence time, flexibly controlling lithium carbonate particle size to meet market demands and improving overall production efficiency. In summary, this process achieves continuous, efficient, and quality-controllable lithium carbonate production, providing reliable technical support for large-scale production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 A three-dimensional structural diagram of the equipment used in the continuous feed-discharge process for producing lithium carbonate; Figure 2 A top view of the equipment used in the continuous feed-discharge process for producing lithium carbonate.

[0021] Reference numerals in the attached drawings: 1. Feeding vessel; 2. Reactor; 3. Settling vessel; 301. First outlet; 4. Reaction tank; 401. First reaction tank; 402. Second reaction tank; 5. Pump; 6. Reflux layer; 7. Stirrer; 8. Heating device; 9. Connecting pipe; 10. Discharge valve. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] In the description of the embodiments of the present invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0025] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0026] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0027] This invention provides a continuous feed-discharge process for producing lithium carbonate, comprising the following steps:

[0028] S1. Add refined lithium sulfate solution and refined sodium carbonate solution to the first feeding vessel 1. All raw materials for the reaction are stored in the reaction tank 4. The reaction tank 4 is connected to the feeding vessel 1 and the reaction vessel 2 via a connecting pipe 9, and a pump 5 is installed on the connecting pipe 9. The refined lithium sulfate solution is placed in the first reaction tank 401, and the refined sodium carbonate solution is placed in the second reaction tank 402. The amount of refined lithium sulfate fed into the feeding vessel 1 is controlled within 60-80% of the theoretical total lithium sulfate feed, ensuring a high-alkali, low-lithium state is maintained within the feeding vessel 1. Hot pure water is added to the empty feeding vessel 1, and simultaneously, the reflux mechanism is activated, i.e., a heat source is introduced into the reflux layer 6 located on the outer wall of the first feeding vessel 1. The heating medium can be steam, water, or heat transfer oil, etc., thereby ensuring that the temperature within the first feeding vessel 1 is controlled at 70-80°C. Within ℃, the mixture is stirred and mixed evenly by the stirrer 7 in the first feeding vessel 1 to obtain a mixture. The mixture is then simultaneously passed through the second feeding vessel 1 and the third feeding vessel 1, which are set in parallel with the first feeding vessel 1. Multiple feeding vessels 1 can be set up and arranged in parallel. The product obtained after stirring is fed into the reaction vessel 2. The number of feeding vessels 1 can be determined according to actual needs.

[0029] The batch operation involves staggered feeding and synchronous output. After the first feeding vessel 1 completes the quantitative addition of lithium sulfate solution and sodium carbonate solution, the stirrer 7 is immediately started to mix them evenly. At the same time, a heat source is introduced through the outer wall reflux layer 6 to stabilize the temperature inside the vessel at 70-80 ℃. This temperature range can promote the initial activation of the raw materials and maintain a high-alkali and low-lithium reaction environment.

[0030] Once the amount of material in the feeding vessel 1 reaches more than 80% of the total volume of the vessel, open the discharge valve 10 of the feeding vessel 1 to discharge the mixture in the feeding vessel 1 to the reaction vessel 2; the opening of the discharge valve 10 of the feeding vessel 1 is adjusted according to the total feed flow rate of the lithium sulfate solution and sodium carbonate solution, and the opening of the discharge valve 10 is adjusted to maintain the balance of the amount of material in the feeding vessel 1.

[0031] S2. The mixture prepared in S1 and the remaining theoretical value of 20-40% lithium sulfate solution are fed into reactor 2 and reacted fully. Reactor 2 is also equipped with a stirrer 7 to ensure that the reaction is complete and an intermediate product is obtained. A reflux layer 6 is provided on the side wall of reactor 2. The reflux layer 6 has a hollow structure. A water inlet is opened at the bottom of one side of the reflux layer 6 and a water outlet is opened at the top of the opposite side of the reflux layer 6. By heating the reflux, the reaction temperature in reactor 2 is maintained at a suitable temperature during the reaction process. At the same time, it can also make the mixture react more evenly during the reaction process and prevent it from settling to the bottom.

[0032] The simultaneous addition of lithium sulfate solution to both reactor 2 and feed vessel 1 is essentially a precise control of raw material distribution: approximately 60-80% of the lithium sulfate enters feed vessel 1 for pretreatment, while the remaining 20-40% directly enters reactor 2. The lithium ion concentration in reactor 2 is ultimately controlled to be below 3 g / L, forming a concentration gradient with the mixture transported from feed vessel 1, which is more conducive to crystal growth. Adding the lithium sulfate solution in two steps allows the reaction to proceed in two steps to control the formation of lithium carbonate. At the same time, the stepwise increase in temperature is also to control the degree of reaction.

[0033] S3. The intermediate product prepared in S2 is transferred into the settling tank 3 and separated by sedimentation to obtain lithium slurry and lithium supernatant. The settling tank 3 is equipped with a stirrer 7 to achieve dynamic sedimentation. When the intermediate product enters the settling tank 3, the stirrer 7 runs at a speed of less than 15 revolutions per minute. The material settles naturally under the action of gravity. The denser lithium carbonate particles gradually settle to the bottom of the tank to form lithium slurry, while the upper layer is lithium supernatant containing a small amount of fine powder. The upper side wall of the settling tank 3 is provided with a first outlet 301. The supernatant after sedimentation in the settling tank 3 can be discharged through the first outlet 301, reducing the separation and processing volume and improving production efficiency.

[0034] The design of the first outlet 301 of the settling tank 3 significantly improves separation efficiency: the supernatant overflows directly through this outlet, and the overflow flow rate is controlled by adjusting the opening of the outlet valve. The settling discharge flow rate is controlled at 30-40% of the total feed flow rate, increasing the solid content concentration of the lithium carbonate slurry to more than twice the original concentration, which can reduce the subsequent solid-liquid separation processing volume by more than 50%. At the same time, the bottom outlet of the tank is connected to the separation system, and the thickened slurry after settling is transported to the filtration stage through pipeline, further reducing the load on the separation equipment.

[0035] In this invention, lithium carbonate is prepared according to the above steps. A discharge pump 5 is installed between the connecting pipes 9 of the feeding vessel 1, the reaction vessel 2, and the settling vessel 3. The discharge pump 5 is connected to a mobile terminal via a wireless module. The working efficiency of the discharge pump 5 can be remotely controlled through the mobile terminal, thereby adjusting the residence time of the material in different containers. After the reaction in the settling vessel 3 is completed, the lithium mother liquor overflows from the top, and the thickening material is discharged from the bottom to the separation system for solid-liquid separation.

[0036] The continuous feeding and discharging process for lithium carbonate production provided by this invention allows for the continuous feeding of two raw materials and the discharge mother liquor in the lithium precipitation reaction at a controllable flow rate. The reaction time of the reflux material in the reactor 2 is controlled by adjusting the working state of the discharge pump 5 to control the lithium carbonate particle size and product quality. The overflow clear liquid from the settling zone thickens the production slurry, reduces the amount of separation and processing, and improves production efficiency.

[0037] The feed flow rate of feeding vessel 1 and reaction vessel 2 shall not exceed the maximum capacity of material in a single vessel, even if the material circulation reaction time in each vessel is greater than 1 hour; when feeding vessel 1 and reaction vessel 2 are not discharging material, the return flow rate is a self-circulating full return flow rate, and the discharge flow rate is adjusted by the return flow rate during the discharge stage for balance.

[0038] The entire production process is intelligently controlled through the linkage between the discharge pump 5 and the wireless module: operators can adjust the frequency of each discharge pump 5 in real time via a mobile device, precisely controlling the material circulation reaction time in the feeding vessel 1 and the reaction vessel 2 to be more than 60 minutes. This control capability not only allows for adjustment of lithium carbonate particle size according to market demand, obtaining a more uniform particle size product by controlling the flow residence time, but also reduces the separation load through the overflow of clear liquid in the settling zone, thereby increasing the overall production efficiency by more than two times.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A process for the continuous in-and-out-feed production of lithium carbonate, characterized in that, The method comprises the following steps: S1, taking refined lithium sulfate solution and refined sodium carbonate solution into a feeding kettle (1), mixing uniformly to obtain a mixture; S2, taking the mixture prepared in S1 and refined lithium sulfate solution into a reaction kettle (2) for sufficient reaction to obtain an intermediate product; S3, taking the intermediate product prepared in S2 into a settling kettle (3), and separating by settling to obtain lithium carbonate slurry and lithium precipitation clear liquid; S4, taking part of the lithium precipitation clear liquid prepared in S3 back to the feeding kettle (1) and the reaction kettle (2).

2. The process for the continuous charge-discharge production of lithium carbonate according to claim 1, characterized in that, The lithium concentration of the refined lithium sulfate solution in S1 is 10-25 g / L, and the concentration of the refined sodium carbonate solution is 260-300 g / L; the molar ratio of lithium sulfate in the refined lithium sulfate solution circulated per unit time to sodium carbonate in the refined sodium carbonate solution circulated per unit time is 1:(1-1.1), the circulation amount of the refined sodium carbonate solution added into the feeding kettle (1) is 100%, and the refined lithium sulfate solution is added into the feeding kettle (1) in at least two times according to the circulation amount.

3. The process for the continuous charge-discharge production of lithium carbonate according to claim 1, characterized in that, The refined lithium sulfate solution and the refined sodium carbonate solution in S2 can be completely continuously convection fed, the lithium carbonate slurry and the lithium precipitation clear liquid produced in S3 can be continuously discharged, the solid content of the lithium carbonate slurry in S3 is >5%, and the return amount of the lithium precipitation clear liquid in S4 is ≤10% of the total amount of the lithium precipitation clear liquid produced.

4. The process for the continuous charging and discharging production of lithium carbonate according to claim 1, characterized in that, The feeding kettle (1), the reaction kettle (2) and the settling kettle (3) are all provided with a stirrer (7), the peripheral side wall of the feeding kettle (1), the reaction kettle (2) and the settling kettle (3) is provided with a plurality of reflux layers (6), and the top and the bottom of the feeding kettle (1), the reaction kettle (2) and the settling kettle (3) are respectively provided with a feeding port and a discharging port.

5. The process for the continuous charging and discharging production of lithium carbonate according to claim 4, characterized in that, The upper side wall of the settling kettle (3) in S3 is also provided with a first outlet (301), the first outlet (301) is used for discharging lithium precipitation clear liquid, and the discharging port of the settling kettle (3) is used for discharging lithium precipitation slurry.

6. The process for the continuous charging and discharging production of lithium carbonate according to claim 4, characterized in that, The plurality of reflux layers (6) are communicated through a connecting pipeline (9), the middle of the connecting pipeline (9) is provided with a heating device (8), the temperature in the feeding kettle (1) in S1 is 70-80℃, the temperature in the reaction kettle (2) in S2 is 80-90℃, and the temperature in the settling kettle (3) in S3 is 90-95℃.

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