Process for extracting lithium from ores

Abstract

The present application provides a kind of ore lithium extraction process, it is related to lithium ore extraction field, comprising the following steps: S1: after transformation, lithium-containing ore is mixed with sulfuric acid, is treated by acidification roasting, and acidified clinker is obtained;S2: after mixing acidified clinker with leaching liquid, it is put into leaching device and leaching reaction is carried out, and leaching slurry is obtained;S3: leaching slurry is treated by impurity removal, and the lithium sulfate solution to be electrolyzed is obtained;S4: the lithium sulfate solution to be electrolyzed enters bipolar membrane electrolysis device, and acid liquor, alkali liquor and salt liquor are obtained by electrolysis;S5: the acid liquor is concentrated, and the water produced by concentration is sent into acid concentration condensate water storage tank after cooling, and the water of acid concentration condensate water storage tank returns to S4;S6: the acid liquor after concentration is reused to S1.The present application classifies recovery according to lithium sulfate concentration and accurately matches use according to quality to condensate water in different sections of acid liquor evaporation concentration.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from ore, specifically a lithium extraction process from ore. Background Technology

[0002] In the field of lithium resource extraction and recycling of waste lithium-ion batteries, acid roasting-water leaching is the mainstream process route for extracting lithium metal ions. In this process, concentrated sulfuric acid is added as an acid roasting agent in the acid roasting stage. After acid roasting and water leaching, lithium minerals will produce an acidic leaching slurry rich in lithium sulfate. After purification and impurity removal, a pure lithium sulfate solution for electrolysis can be obtained from the leaching slurry.

[0003] To achieve the resource recovery of lithium sulfate and the resource production of acid and alkali, existing technologies generally use bipolar membrane electrolysis devices to electrolyze and dissociate pure lithium sulfate solutions. Under the action of bipolar membrane electrolysis, lithium sulfate can be decomposed into dilute sulfuric acid solution, lithium hydroxide alkali solution, and residual salt-containing mother liquor.

[0004] Existing patents, such as CN111235591A, a method for preparing lithium hydroxide monohydrate from spodumene sulfuric acid leaching solution, have the following problems: the electrolytic dilute acid is not concentrated to a suitable acidification roasting concentration; the dilute acid cannot be directly reused for roasting; there is no condensate circulation or salt solution treatment closed loop, resulting in the waste of sulfuric acid discharge. Summary of the Invention

[0005] This invention provides a lithium extraction process from ore to solve the technical problems mentioned in the background section.

[0006] To address the aforementioned technical problems, this invention discloses a lithium extraction process from ore, comprising the following steps: S1: The transformed lithium-containing ore is mixed with sulfuric acid and then acidified and roasted to obtain acidified clinker; S2: The acidified clinker is mixed with the leaching solution and then fed into the leaching device to carry out the leaching reaction, and a leaching slurry is obtained. S3: The leachate slurry is treated to remove impurities, resulting in a lithium sulfate solution to be electrolyzed; S4: The lithium sulfate solution to be electrolyzed enters the bipolar membrane electrolysis device, where it is electrolyzed to obtain acid solution, alkali solution and salt solution; S5: The acid solution is concentrated, and the water produced by concentration is cooled and sent to the acid concentration condensate storage tank. The water in the acid concentration condensate storage tank is returned to S4. S6: The concentrated acid solution is reused in S1.

[0007] Preferably, step S3 includes: S31: The leachate slurry is subjected to countercurrent washing and filtration to achieve solid-liquid separation and obtain filter residue, washing water and acid leaching solution. The separated washing water is returned to S2. S32: Add limestone slurry to the acid leaching solution, adjust the pH value of the acid leaching solution to 5-7, carry out neutralization and impurity removal reaction, and generate a mixture containing gypsum, iron and aluminum slag. S33: The mixture is filtered and washed to separate solid gypsum iron-aluminum slag, neutralizing liquid and washing water. The washing water is returned to S2. S34: The neutralized liquid is subjected to calcium and magnesium precipitation removal treatment, followed by filtration and washing to separate calcium and magnesium slag and primary lithium sulfate purification liquid. S35: The primary lithium sulfate purification solution is subjected to calcium and magnesium removal treatment with chelating resin to obtain a lithium sulfate solution to be electrolyzed.

[0008] Preferably, the leaching solution is water; S34 includes: mixing the neutralizing solution with dilute alkali and carbonization mother liquor, adjusting the pH value of the mixture to 11-12, keeping it at 70-95℃ for 0.5h-2h for filtration, obtaining a primary lithium sulfate purification solution and filter residue after filtration, and obtaining calcium magnesium slag after rinsing the filter residue with water.

[0009] Preferably, the current density is controlled at 150–400 A / m during electrolysis. 2 The electrolysis temperature is 25–35℃, and the cell voltage is 15–30V.

[0010] Preferably, when replenishing water to the salt chamber of the bipolar membrane device, the volumetric flow rate of the replenished water is 10% to 20% of the volumetric flow rate of the lithium sulfate solution in the salt chamber.

[0011] Preferably, storage tank one is used to recover and reuse condensate in the acid chamber; storage tank two is used to recover and reuse condensate in the salt chamber.

[0012] Preferably, condensate with a lithium sulfate concentration of less than or equal to 5 μS / cm is recycled to storage tank one; condensate with a lithium sulfate concentration greater than 5 μS / cm and less than or equal to 10 μS / cm is recycled to storage tank two.

[0013] Preferably, the storage tank has water inlet at the top and water outlet at the bottom.

[0014] Preferably, the lithium sulfate feed concentration is divided into several feed concentration ranges; in S3, the lithium sulfate concentration of the lithium sulfate solution to be electrolyzed is periodically detected; During the process experimentation phase, corresponding electrolysis control parameters and a water replenishment correlation mechanism were determined for each lithium sulfate concentration range. The water replenishment correlation mechanism includes the corresponding rules for lithium sulfate concentration range, lithium sulfate concentration rise rate range, and equivalent total pure water replenishment flow rate.

[0015] Preferably, S4 includes: S41: Based on the lithium sulfate concentration of the lithium sulfate solution to be electrolyzed detected in S3, determine the current lithium sulfate concentration range of the lithium sulfate solution to be electrolyzed. Based on the electrolysis control parameters corresponding to the current lithium sulfate concentration range of the lithium sulfate solution to be electrolyzed, control the bipolar membrane electrolysis device to work for the current target duration. Within the current target duration, detect the lithium sulfate concentration in the salt chamber and detect the pH of the discharge zone of storage tank 2 to determine the current rate of increase of the current lithium sulfate concentration in the salt chamber within the current target duration. S42: Determine the current equivalent total pure water replenishment flow rate based on the current rate of increase of lithium sulfate concentration in the salt chamber within the current target time, the current range of lithium sulfate concentration in the lithium sulfate solution to be electrolyzed, and the corresponding water replenishment correlation mechanism. S43: Control the pure water to be supplied to the bipolar membrane electrolyzer at the current equivalent total pure water supply flow rate and maintain the electrolysis control parameters of S41 to continue electrolysis, and determine the current water supply flow rate of the second storage tank to the salt chamber and the current pure water supply flow rate of the salt chamber based on the pH of the discharge zone of the second storage tank detected within the current target time. S44: Based on S43, determine the current water supply flow rate of the salt chamber from the second storage tank and the current pure water supply flow rate from the salt chamber, and maintain the electrolysis control parameters of S41 to continue electrolysis; and periodically detect the pH of the discharge area of ​​the second storage tank; Based on the pH of the discharge zone of storage tank 2, determine whether to update the latest water supply flow rate of storage tank 2 to the salt chamber and the pure water supply flow rate of the salt chamber. If an update is needed, use the updated water supply flow rate to continue electrolysis. Periodically return to execute S41 once. When the range of lithium sulfate concentration change rate of the lithium sulfate solution to be electrolyzed is determined, execute S42-S44 again in sequence.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention concentrates the acid produced by bipolar membrane electrolysis, and the concentrated sulfuric acid is reused in the acidification and roasting process to replace fresh concentrated sulfuric acid; at the same time, the condensate generated during concentration is recycled and returned to the S2 section of the bipolar membrane electrolysis unit for reuse, avoiding the drawback of acid discharge in the prior art.

[0018] In existing technologies, the salt chamber makeup water is still supplied by an external fresh water source, while the condensate water generated in the acid concentration section is directly discharged as wastewater, resulting in waste of internal water resources and a large consumption of fresh water. This invention recycles and reuses the qualified condensate water produced and graded by the acid concentration section in the original salt chamber makeup water process as an internal circulating water source for salt chamber makeup water, realizing the internal resource utilization of self-produced wastewater.

[0019] This invention classifies and precisely distributes condensate from different stages of acid evaporation and concentration based on conductivity: ① High-purity condensate with conductivity ≤5μS / cm is recycled to a dedicated storage tank and directly reused in the acid electrolysis chamber. The high-purity water stabilizes the acidity in the chamber, prevents impurities from being introduced into the acid, and ensures the purity of the reused sulfuric acid; ② Medium-purity condensate with conductivity 5~10μS / cm is recycled to another storage tank and is specifically used for salt chamber makeup water; this avoids bipolar membrane contamination caused by the reuse of mixed condensate. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0021] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0022] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] The present invention provides the following embodiments: Example 1: This embodiment of the invention provides a lithium extraction process from ore, such as... Figure 1 As shown, it includes the following steps: S1: The transformed lithium-bearing ore (β-spodumene) is mixed with sulfuric acid and then acid-roasted to obtain acid-roasted clinker; ore pretreatment (spodumene as an example): typically, it is roasted at 1050–1100℃ for 30–60 minutes to complete the crystal transformation from α-spodumene to β-spodumene. The above-mentioned process S1, involving the acid-roasting of β-spodumene mixed with sulfuric acid, is existing technology. S2: The acidified clinker is mixed with the leaching solution (the leaching solution is water, including pure water or the washing water described below) and then put into the leaching device to carry out the leaching reaction to obtain the leaching slurry; S3: The leachate slurry is treated to remove impurities, resulting in a lithium sulfate solution to be electrolyzed; S4: The lithium sulfate solution to be electrolyzed enters the bipolar membrane electrolysis device, and electrolysis yields acid solution (dilute acid), alkali solution (dilute alkali) and salt solution (sulfuric acid aqueous solution, lithium hydroxide aqueous solution, soluble alkali metal salt solution). S5: The acid solution is concentrated, and the water produced by concentration is cooled and sent to the acid concentration condensate storage tank. The water in the acid concentration condensate storage tank is returned to S4. S6: The concentrated acid solution is reused in S1.

[0024] A lithium hydroxide aqueous solution is subjected to a carbonization reaction to obtain battery-grade lithium carbonate product and carbonization mother liquor; Step S3 includes: S31: The leachate slurry is subjected to countercurrent washing and filtration to achieve solid-liquid separation and obtain filter residue, washing water and acid leaching solution. The separated washing water is returned to S2. S32: Add limestone slurry to the acid leaching solution, adjust the pH value of the acid leaching solution to 5-7, carry out neutralization and impurity removal reaction, and generate a mixture containing gypsum, iron and aluminum slag. S33: The mixture is filtered and washed to separate solid gypsum iron-aluminum slag, neutralizing liquid and washing water. The washing water is returned to S2. S34: The neutralized liquid is subjected to calcium and magnesium precipitation removal treatment, followed by filtration and washing to separate calcium and magnesium slag and primary lithium sulfate purification liquid. S35: The primary lithium sulfate purification solution is subjected to calcium and magnesium removal treatment with chelating resin to obtain a lithium sulfate solution to be electrolyzed.

[0025] The process involves concentrating the brine solution, and the resulting water can be stored in a brine condensate tank, which can also be returned to S4. This concentration of the brine solution allows for the recovery and enrichment of lithium salt resources. S34 includes: mixing the neutralizing solution with dilute alkali and carbonization mother liquor, adjusting the pH value of the mixture to 11-12, keeping it at 70-95℃ for 0.5h-2h for filtration, obtaining a primary lithium sulfate purification solution and filter residue after filtration, and obtaining calcium magnesium slag after rinsing the filter residue with water. Based on the composition of the impurity removal solution with a pH of 5-7, further removal of calcium and magnesium is required. By adding a very small amount of dilute alkali to adjust the pH to 12, and then adding the carbonization mother liquor, and keeping it at 70-95℃ for 0.5-2 hours, the calcium in the removed solution can be reduced to below 30 mg / L and the magnesium to below 5 mg / L after filtration.

[0026]

[0027]

[0028] Therefore, the optimal impurity removal process is as follows: Mix limestone slurry with acid leaching solution, maintaining a pH of 5–7. After filtration, obtain the impurity-removed solution. Wash the filter residue with water to obtain a mixture of calcium sulfate, iron, and aluminum slag. Return the washing solution to the leaching process. Alternatively, mix the pH 5–7 impurity-removing solution with dilute alkali and carbonization mother liquor, maintaining a pH of 11–12 at 95°C. After filtration, obtain a pH 12 impurity-removing solution. Wash the filter residue with water to obtain calcium magnesium slag. Return the washing solution to the leaching process.

[0029] Optionally, the acid concentration in S5 after concentration is above 70%. The acid concentration of this invention can be achieved using existing concentration methods; Preferably, the current density is controlled at 150–400 A / m during electrolysis. 2 The electrolysis temperature is 25-35℃, and the cell voltage is 15-30V; the feed flow rate of the lithium sulfate solution to be electrolyzed is controlled at 1-3 BV / h.

[0030] Preferably, when replenishing water to the salt chamber of the bipolar membrane device, the volumetric flow rate of the replenished water is 10% to 20% of the volumetric flow rate of the lithium sulfate solution in the salt chamber.

[0031] Preferably, the condensate from different concentration sections of the acid evaporation and concentration device is recycled in stages. Condensate with a conductivity of less than or equal to 5 μS / cm is recycled to storage tank one for reuse in the acid chamber; condensate with a conductivity greater than 5 μS / cm and less than or equal to 10 μS / cm is recycled to storage tank two for reuse in the salt chamber for makeup water; storage tank one has water inlet at the top and water outlet at the bottom.

[0032] The beneficial effects of the above scheme are as follows: This invention concentrates the acid produced by bipolar membrane electrolysis, and the concentrated sulfuric acid is reused in the acidification and roasting process to replace fresh concentrated sulfuric acid; at the same time, the condensate generated during concentration is recycled and returned to the S2 section of the bipolar membrane electrolysis unit for reuse, avoiding the drawback of acid discharge in the prior art.

[0033] In existing technologies, the salt chamber makeup water is still supplied by an external fresh water source, while the condensate water generated in the acid concentration section is directly discharged as wastewater, resulting in waste of internal water resources and a large consumption of fresh water. This invention recycles and reuses the qualified condensate water produced and graded by the acid concentration section in the original salt chamber makeup water process as an internal circulating water source for salt chamber makeup water, realizing the internal resource utilization of self-produced wastewater.

[0034] This invention classifies and precisely distributes condensate from different stages of acid evaporation and concentration based on conductivity: ① High-purity condensate with conductivity ≤5μS / cm is recycled to a dedicated storage tank and directly reused in the acid electrolysis chamber. The high-purity water stabilizes the acidity in the chamber, prevents impurities from being introduced into the acid, and ensures the purity of the reused sulfuric acid; ② Medium-purity condensate with conductivity 5~10μS / cm is recycled to another storage tank and is specifically used for salt chamber makeup water; this avoids bipolar membrane contamination caused by the reuse of mixed condensate.

[0035] In existing technologies, only a low concentration of lithium salt solution can be obtained in the leaching step, necessitating subsequent concentration. Currently, technologies such as MVR are commonly used for evaporation and concentration of the leachate, a step that consumes a large amount of energy, resulting in high operating costs. In this process, the acid leaching step utilizes a combination of bipolar membrane dilute solution, acid leaching wash solution, and neutralization residue wash solution to directly achieve a lithium concentration greater than 32 g / L in the acid leaching solution. While increasing the lithium content, the content of impurity elements in the acid leaching solution does not significantly increase. This method can obtain high-concentration lithium sulfate without a subsequent concentration step.

[0036] S3 uses limestone to adjust the pH of the acid leaching solution to 5-7 for neutralization and impurity removal. Compared with traditional neutralizing agents such as liquid alkali and soda ash, limestone raw material costs are extremely low, which can reduce the raw material costs of the neutralization process. At the same time, the neutralization reaction can efficiently remove free acid in the acid leaching solution and precipitate impurity ions such as iron and aluminum in the form of hydroxides, which are then co-precipitated with the generated gypsum (calcium sulfate) to form gypsum-iron-aluminum slag. This achieves efficient separation of impurities and ensures the purity of the subsequent lithium solution.

[0037] Example 2, based on Example 1, divides the lithium sulfate feed concentration into several feed concentration ranges; in S3, the lithium sulfate concentration of the lithium sulfate solution to be electrolyzed is periodically detected; During the process experimentation phase, corresponding electrolysis control parameters and a water replenishment correlation mechanism were determined for each lithium sulfate concentration range. The water replenishment correlation mechanism includes the corresponding rules for lithium sulfate concentration range, lithium sulfate concentration rise rate range, and equivalent total pure water replenishment flow rate.

[0038] S41: Based on the lithium sulfate concentration of the lithium sulfate solution to be electrolyzed detected in S3, determine the current lithium sulfate concentration range of the lithium sulfate solution to be electrolyzed. Based on the electrolysis control parameters corresponding to the current lithium sulfate concentration range of the lithium sulfate solution to be electrolyzed, control the bipolar membrane electrolysis device to work for the current target duration. Within the current target duration, detect the lithium sulfate concentration in the salt chamber and detect the pH of the discharge zone of storage tank 2 to determine the current rate of increase of the current lithium sulfate concentration in the salt chamber within the current target duration. S42: Determine the current equivalent total pure water replenishment flow rate based on the current rate of increase of lithium sulfate concentration in the salt chamber within the current target time, the current range of lithium sulfate concentration in the lithium sulfate solution to be electrolyzed, and the corresponding water replenishment correlation mechanism. S43: Control the pure water to be supplied to the bipolar membrane electrolyzer at the current equivalent total pure water supply flow rate and maintain the electrolysis control parameters of S41 to continue electrolysis, and determine the current water supply flow rate of the second storage tank to the salt chamber and the current pure water supply flow rate of the salt chamber based on the pH of the discharge zone of the second storage tank detected within the current target time. S44: Based on S43, determine the current water supply flow rate of the salt chamber from the second storage tank and the current pure water supply flow rate from the salt chamber, and maintain the electrolysis control parameters of S41 to continue electrolysis; and periodically detect the pH of the discharge area of ​​the second storage tank; Based on the pH of the discharge zone of storage tank 2, determine whether to update the latest water supply flow rate of storage tank 2 to the salt chamber and the pure water supply flow rate of the salt chamber. If an update is needed, use the updated water supply flow rate to continue electrolysis. Periodically return to execute S41 once. When the range of lithium sulfate concentration change rate of the lithium sulfate solution to be electrolyzed is determined (including the cross-range of lithium sulfate feed concentration range, or the large change within the same lithium sulfate feed concentration range), execute S42-S44 again in sequence.

[0039] It can also record the rate of increase of lithium sulfate concentration in the salt chamber within the current target time period, and assess the impact of raw materials and electrolysis equipment on it (for example, for the same batch of raw materials, the rate of increase of lithium sulfate concentration in the raw materials themselves can be assessed).

[0040] 1) Pre-divide the lithium sulfate feed concentration into ranges and set multiple graded feed concentration ranges. Each concentration range corresponds to a set of matching electrolysis control parameters (electrolysis current density, cell voltage, feed flow rate, salt chamber water replenishment ratio parameters). The concentration range can be electrolyzed successfully under the corresponding electrolysis control parameters. Taking advantage of the positive correlation between the concentration of lithium sulfate solution and the concentration of lithium sulfate, there is no need for complex concentration testing. The lithium sulfate concentration of the lithium sulfate solution to be electrolyzed is only periodically monitored in real time in the S3 purification section. The lithium sulfate feed concentration can be quickly determined, and the real-time concentration is matched to the corresponding preset feed concentration range. The matching electrolysis control parameters corresponding to that range are automatically called.

[0041]

[0042] 2) The water replenishment mechanism is shown in the table below:

[0043] The equivalent total pure water makeup flow rate is the makeup flow rate when only pure water is used for makeup.

[0044] In actual electrolytic production, even under the same lithium sulfate concentration range and even under the same feed lithium sulfate concentration conditions, and even if the feed has undergone deep purification and is not affected by external impurities, it is still affected by the intrinsic factors of the lithium sulfate solution itself (differences in batch raw material dissolution, different residence time of lithium sulfate storage tank before electrolysis, fluctuations in lithium ion association degree, differences in ion hydration state, fluctuations in hydrolysis equilibrium of the solution itself, etc.) and the intrinsic factors of the electrolysis device itself (differences in the degree of bipolar membrane aging and contamination, electrode plate operating conditions, fluctuations in actual operating conditions of the electrode chamber, etc.). The rate of increase of lithium sulfate concentration in the salt chamber (dehydration concentration rate) still has significant substantial differences (e.g., the ratio of the maximum to minimum rate of increase of lithium sulfate concentration under the same lithium sulfate concentration conditions is less than 1.2).

[0045] If we simply follow the existing fixed gradient rule that the higher the concentration of lithium sulfate in the feed, the smaller the water replenishment flow rate, or take the median value for water replenishment within the corresponding lithium sulfate concentration range, or use a uniform fixed water replenishment flow rate for the same lithium sulfate concentration in the feed, none of these methods can adapt to the differences in water loss rate under the above-mentioned operating conditions with the same concentration. This can easily lead to problems such as water shortage and crystallization blockage in the salt chamber, excessive dilution and reduced current efficiency, and cannot meet the actual needs of stable electrolysis operation.

[0046] The pure water mentioned above refers to the water used in the bipolar membrane electrolysis device of this invention, excluding the general makeup water for condensate return.

[0047] 3) The current target duration is the rate detection runtime under the current lithium sulfate concentration range (refer to the division in 1 above) with pure water completely shut off and no water replenishment; the proportion of the maximum allowable safe runtime without water replenishment under the current target duration is less than 2%, which ensures that the runtime without water replenishment is sufficient to stably measure the true effective lithium sulfate concentration increase change due to the original water loss concentration in the salt chamber, while strictly not exceeding the safe range of the device's allowable operation without water replenishment, and will not cause excessive water loss in the salt chamber or failure to meet the operating requirements due to the lack of water replenishment; The target duration is typically 1 to 5 minutes (preferably 2 minutes).

[0048] The calculation method for the rate of increase of lithium sulfate concentration in the salt chamber is as follows: During the target duration of operation with the pure water completely shut off and no water replenishment, the lithium sulfate concentration in the salt chamber at the start and end of the target duration is collected; the lithium sulfate concentration in the salt chamber at the end time is subtracted from the lithium sulfate concentration at the start time to obtain the total increase in lithium sulfate concentration in the salt chamber within the target duration; then, the total increase in lithium sulfate concentration is divided by the target duration to calculate the increase in lithium sulfate concentration in the salt chamber per unit time, which is the current rate of increase of lithium sulfate concentration in the salt chamber within the current target duration.

[0049] 4) Based on the pH value of the discharge zone of Tank 2 detected within the current target time period (the average value of the discharge zone of Tank 2 detected within the current target time period), determine the current makeup water flow rate of Tank 2 to the brine chamber and the current makeup water flow rate of pure water to the brine chamber; specifically: The actual operating pH range of the condensate from storage tank 2 is 5.0–7.0. The closer the condensate pH is to neutral 7.0, the higher the purity and the better the water quality. Correspondingly, the higher the proportion of condensate return water reuse in the total equivalent pure water makeup flow of storage tank 2. Multiple pH ranges and corresponding fixed proportions are defined according to strictly closed intervals: ①6.5≤pH≤7.0 (high-quality neutral condensate): The makeup water flow rate of the second pair of salt chambers in the storage tank accounts for 70% of the current equivalent total pure water makeup water flow rate; ②5.8 < pH < 6.5 (moderately weak acid condensate): The makeup water flow rate of the second pair of salt chambers in the storage tank accounts for 45% of the current equivalent total pure water makeup flow rate; ③ 5.0≤pH≤5.8 (slightly acidic condensate containing impurities): The makeup water flow rate for the second pair of salt chambers in the storage tank accounts for 20% of the current equivalent total pure water makeup water flow rate; Two-way water supply split formula: Fresh pure water supply flow rate to the salt chamber = Current equivalent total pure water supply flow rate - Supply flow rate of condensate return water from storage tank 2 to the salt chamber; Because the condensate discharged from the evaporation and concentration process will be cooled before being stored in storage tank two, it does not correspond to the time of lithium sulfate feeding. Therefore, it is necessary to consider the proportion of condensate returned to the salt chamber based on the actual pH characteristics of the discharge area of ​​storage tank two.

[0050] 5) Based on the pH of the discharge zone of storage tank 2, determine whether to update the latest water supply flow rate of storage tank 2 to the salt chamber and the water supply flow rate of pure water to the salt chamber (update is required for different pH ranges located at 4). When an update is required, water is supplied with the updated water supply flow rate, and electrolysis continues. During the update period, the equivalent total pure water supply flow rate remains constant. The beneficial effects of this embodiment are: 1. Based on Example 1, this embodiment addresses the common problems in existing lithium sulfate bipolar membrane electrolytic concentration processes, such as offline testing of feed concentration, offline estimation of water loss rate, offline fixed gradient water replenishment, offline extensive reuse of condensate, and hysteresis control. This invention is based on online real-time lithium sulfate concentration detection in the S3 section. It divides the lithium sulfate feed concentration into multiple ranges, realizes online real-time identification of feed concentration and online automatic matching of corresponding concentration ranges, replaces traditional offline concentration testing, responds quickly, and realizes online feeding conditions from the source. Pre-tested and calibrated online adaptive electrolysis control parameters (current density, cell voltage, temperature, feed flow rate) for each concentration range can be automatically called online to achieve online adaptive electrolysis control under different feed concentration conditions, ensuring stable and qualified electrolysis across the entire feed range; Establish an online real-time linkage water replenishment correlation mechanism: the lithium sulfate concentration range, the lithium sulfate concentration rise rate range, and the equivalent total pure water replenishment flow rate are all corresponded online, breaking the existing offline static fixed water replenishment underlying logic and laying the core online mechanism foundation for subsequent full-process online adaptive control.

[0051] 2. During the same target time period, collect two online real-time parameters: lithium sulfate concentration in the salt chamber and pH of the condensate from the second discharge tank. Acquire real-time data on the salt chamber water loss characteristics and the quality of the recycled condensate in one go. The system is coupled online with the current feed concentration range and the measured water loss rate in the S41 salt chamber, and matched with an online water replenishment mechanism to dynamically calculate the equivalent total pure water replenishment flow rate. Instead of using offline static fixed water replenishment, it dynamically adjusts the flow rate online in accordance with the real-time water loss rate. The faster the online water loss rate, the higher the total online real-time water replenishment; the slower the online water loss rate, the lower the total online real-time water replenishment. The online real-time adaptation can adapt to significant differences in water loss rate under the same concentration conditions, fundamentally solving the fatal defect that offline fixed water replenishment cannot adapt to fluctuations in online real-time conditions. The system strictly defines the equivalent total pure water replenishment flow rate benchmark online, maintains the independent and stable online water balance logic, and reserves a safe and controllable space for the subsequent refined separation of online condensate reuse, thus completing the progressive implementation from online characteristic detection to real-time decision-making on online total water replenishment.

[0052] 3. The system adopts an online real-time pH water quality classification and online reuse logic in the discharge area of ​​the storage tank: the closer the online real-time pH is to neutral 7.0, the higher the purity of the online condensate water, and the higher the proportion of online condensate water reuse; the more acidic the online real-time pH is, the more impurities there are, the lower the proportion of online condensate water reuse, and the higher the proportion of online fresh pure water replenishment; the system relies entirely on online real-time water quality data for refined water classification. 4. Construct a dual-cycle, layered online adaptive control logic: In the short cycle, the pH of the second tank outlet is continuously monitored online in real time. The water supply ratio of the two channels is only updated online when the online pH changes effectively across the range, avoiding frequent fluctuations and loss of control in the online flow. In the long cycle, the system automatically returns to execute S41 periodically online to re-detect the original water loss rate of the salt chamber and recalibrate the equivalent total pure water supply flow rate online, eliminating long-term operational deviations online. When the feed online changes significantly across the concentration range or within the same range, the system automatically resets and re-executes the entire process of S42-S44 online, providing full-condition online adaptive coverage. The electrolysis control parameters remain stable online throughout the process, and the fully automatic online operation requires no manual intervention. This forms a complete online closed-loop progressive control system: online measurement of water loss rate → online determination of total water supply → online pH water distribution → online adaptive update → online periodic recalibration, achieving precise and reliable online control.

[0053] Example 3, based on Example 1, Optionally, the concentration of the acid obtained by electrolysis is 5% to 20%; in the acid concentration device (the acid is concentrated sequentially through a first concentration section, a middle evaporation section, and a tail evaporation section), the controlled evaporation temperatures of the first concentration section, the middle evaporation section, and the tail evaporation section are 70℃ to 95℃, 95℃ to 110℃, and 140℃ to 165℃, respectively. The controlled evaporation vacuum degrees of the first concentration section, the middle evaporation section, and the tail evaporation section are -0.09MPa to -0.07MPa, -0.07MPa to -0.04MPa, and -0.03MPa to -0.01MPa, respectively.

[0054] S5 includes acid concentration, which includes: S51: Based on the midpoint of the interval of the reference vacuum control parameters of each concentration section corresponding to the dilute acid to be concentrated under the current working condition, the acid vacuum concentration device is controlled to concentrate the dilute acid under the current working condition for the second duration of the concentration operation. The reference vacuum control parameters for the dilute acid to be concentrated under the same operating conditions are located in the same relatively small reference vacuum control parameter range (the ratio of the maximum value to the minimum value of the vacuum control parameter is less than 1.1). During the process experiment, different acid concentrations were tested based on the acid concentration obtained from electrolysis to determine the corresponding vacuum control parameters that meet the requirements for concentration. Acid concentrations that meet the requirements of the vacuum parameter range after aggregation (the ratio of the maximum value to the minimum value of the vacuum control parameter is less than 1.1) were aggregated into the same working condition. For example, the following aggregation: Acid concentration [5wt%, 10wt%], vacuum degree of the first evaporation section -0.09MPa to -0.085MPa, evaporation temperature of the first evaporation section controlled at 70℃ to 78℃; Acid concentration (10wt%, 15wt%), vacuum degree of the first evaporation section -0.085MPa to -0.08MPa, evaporation temperature of the first evaporation section controlled at 78℃ to 85℃; Acid concentration (15wt%, 20wt%), vacuum degree of the first evaporation section -0.08MPa to -0.075MPa, and evaporation temperature of the first evaporation section controlled at 85℃ to 90℃.

[0055] The acid concentration [5wt%, 20wt%] is used in both the middle and tail evaporation sections, following the range of section 1 in Example 3; it is not graded according to acid concentration and is not adapted to different operating conditions. The second duration is a fixed duration node for determining the concentration state, which is obtained by pre-calibration of offline process experiments and is specific to different acid concentration conditions; the value range is 15s to 60s. For all acid concentrations under the same operating condition, the steady-state acid density rise rate of each independent chamber was measured at a fixed node during the second concentration period (during the test, the midpoint of the vacuum control parameter range corresponding to the first section was used for both the middle and final evaporation sections). The arithmetic mean of the first concentration section was independently calculated and used as the unique fixed operating condition reference rate for the corresponding chamber. The reference acid density rise rates for the middle and final evaporation sections were the average acid density rise rates of the chambers in the middle and final evaporation sections during the test for the full concentration, respectively; the reference acid density rise rate was fixed.

[0056] S52: During the second time period, based on the online real-time density detection data of each chamber, calculate the actual rate of increase of acid density in each concentration section (rate unit % / s), and at the same time collect the final density of acid after vacuum concentration at the end of the second time period. S53: When the final density of the acid solution after vacuum concentration determined by S52 meets the preset process requirements (the density of the acid solution with an acid concentration greater than or equal to 70%), the acid vacuum concentration device will continue to be controlled by the control parameters of S51. When the final acid density after vacuum concentration determined by S52 does not meet the preset process requirements, the deviation rate of the acid density rise rate in each concentration section is determined independently. The preset qualified threshold is ±5%. If either the deviation rate is >5% or <-5%, it is judged as an abnormal rate deviation. When there is a concentration section with an abnormal acid density rise rate deviation rate, the current online operation control parameters of the abnormal concentration section are adjusted according to the pre-calibrated target vacuum control parameters matched with the abnormal concentration section until the final acid density after vacuum concentration meets the preset process requirements. Normal concentration sections without abnormalities maintain the original reference parameters. S54: After adjustment in S53, the concentration process continues, and S51-S54 are executed periodically. If the raw material batch has not been changed more than a preset number of times (e.g., 3 times), the adjustment in S53 will be triggered to issue an alarm.

[0057] Actual rate of increase in acid density in the chamber: Obtain the online density of the concentrated section chamber at the start of the second time period and the online density of the concentrated section chamber at the end of the second time period respectively; Subtract the density at the start of the second time period from the density at the end of the second time period to obtain the density change difference, and then divide it by the duration of the second time period to obtain the actual rate of increase in acid density per unit time in the concentrated section chamber; The first concentrated section, the middle evaporation section, and the tail evaporation section are independent of each other and calculated separately.

[0058] At the same time, the density of the material discharged from the tail evaporation section at the end of the second time period was collected as the density of the acid solution after final vacuum concentration.

[0059] The deviation rate of the acid density rise rate in the current concentration section chamber = (actual acid density rise rate in the current concentration section chamber - reference acid density rise rate in the current concentration section chamber) ÷ reference acid density rise rate in the current concentration section chamber. The target vacuum control parameter for the deviation rate of acid density rise in the first concentration section is the vacuum degree, and the single adjustment gradient of the target vacuum control parameter is 1% of the target vacuum control parameter before adjustment. In the concentration section: when the absolute value of the acid density rise rate deviation rate is less than the first preset value (7%), the target vacuum control parameter for the concentration section is the vacuum degree, and the single adjustment gradient of the target vacuum control parameter is 1% of the target vacuum control parameter before adjustment; when the absolute value of the acid density rise rate deviation rate is less than the first preset value, the target vacuum control parameter is the temperature, and the single adjustment gradient of the target vacuum control parameter is 2% of the target vacuum control parameter before adjustment. The target vacuum control parameter for the concentration section with abnormal deviation rate is temperature. The single adjustment gradient of the target vacuum control parameter is 2%. This embodiment can be used in application scenarios where the same working conditions are generally maintained for a relatively long period of time. The beneficial effects of this embodiment are: Based on the long-term fixed baseline parameters under the same operating conditions, the deviation rate of the independent density rise rate of each chamber is used to distinguish between changes in the feeding conditions and fluctuations in the material itself, as well as the long-term deterioration of the equipment's operating status. Only the chambers with abnormal rate deviations are adjusted in a targeted manner, while the baseline parameters of normal chambers remain unchanged throughout the process, without interfering with the long-term steady-state operation.

[0060] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A lithium extraction process from ore, characterized in that: Includes the following steps: S1: The transformed lithium-containing ore is mixed with sulfuric acid and then acidified and roasted to obtain acidified clinker; S2: The acidified clinker is mixed with the leaching solution and then fed into the leaching device to carry out the leaching reaction, and a leaching slurry is obtained. S3: The leachate slurry is treated to remove impurities, resulting in a lithium sulfate solution to be electrolyzed; S4: The lithium sulfate solution to be electrolyzed enters the bipolar membrane electrolysis device, where it is electrolyzed to obtain acid solution, alkali solution and salt solution; S5: The acid solution is concentrated, and the water produced by concentration is cooled and sent to the acid concentration condensate storage tank. The water in the acid concentration condensate storage tank is returned to S4. S6: The concentrated acid solution is reused in S1.

2. The lithium extraction process from ore according to claim 1, characterized in that: Step S3 includes: S31: The leachate slurry is subjected to countercurrent washing and filtration to achieve solid-liquid separation and obtain filter residue, washing water and acid leaching solution. The separated washing water is returned to S2. S32: Add limestone slurry to the acid leaching solution, adjust the pH value of the acid leaching solution to 5-7, carry out neutralization and impurity removal reaction, and generate a mixture containing gypsum, iron and aluminum slag. S33: The mixture is filtered and washed to separate solid gypsum iron-aluminum slag, neutralizing liquid and washing water. The washing water is returned to S2. S34: The neutralized liquid is subjected to calcium and magnesium precipitation removal treatment, followed by filtration and washing to separate calcium and magnesium slag and primary lithium sulfate purification liquid. S35: The primary lithium sulfate purification solution is subjected to calcium and magnesium removal treatment with chelating resin to obtain a lithium sulfate solution to be electrolyzed.

3. The lithium extraction process from ore according to claim 2, characterized in that: The leaching solution is water; S34 includes: mixing the neutralizing solution with dilute alkali and carbonization mother liquor, adjusting the pH of the mixture to 11-12, keeping it at 70-90℃ for 0.5-2 hours for filtration, obtaining a primary lithium sulfate purification solution and filter residue after filtration, and obtaining calcium magnesium slag after rinsing the filter residue with water.

4. The lithium extraction process from ore according to claim 1, characterized in that: The current density is controlled at 150–400 A / m during electrolysis. 2 The electrolysis temperature is 25–35℃, and the cell voltage is 15–30V.

5. The lithium extraction process from ore according to claim 1, characterized in that: When replenishing water to the salt chamber of the bipolar membrane device, the volumetric flow rate of the replenished water is 10% to 20% of the volumetric flow rate of the lithium sulfate solution in the salt chamber.

6. The lithium extraction process from ore according to claim 1, characterized in that: Tank 1 is used to recover and reuse condensate in the acid chamber; Tank 2 is used to recover and reuse condensate in the salt chamber.

7. The lithium extraction process from ore according to claim 6, characterized in that: Condensate with a conductivity of 5 μS / cm or less is recycled to storage tank one; condensate with a conductivity of 5 μS / cm or less than or equal to 10 μS / cm is recycled to storage tank two.

8. The lithium extraction process from ore according to claim 6, characterized in that: The storage tank has water entering from the top and exiting from the bottom.

9. A lithium extraction process from ore according to claim 6, characterized in that: The lithium sulfate feed concentration is divided into several feed concentration ranges; the lithium sulfate concentration of the lithium sulfate solution to be electrolyzed is periodically detected in S3; During the process experimentation phase, corresponding electrolysis control parameters and a water replenishment correlation mechanism were determined for each lithium sulfate concentration range. The water replenishment correlation mechanism includes the corresponding rules for lithium sulfate concentration range, lithium sulfate concentration rise rate range, and equivalent total pure water replenishment flow rate.

10. A lithium extraction process from ore according to claim 9, characterized in that: S4 includes: S41: Based on the lithium sulfate concentration of the lithium sulfate solution to be electrolyzed detected in S3, determine the current lithium sulfate concentration range of the lithium sulfate solution to be electrolyzed. Based on the electrolysis control parameters corresponding to the current lithium sulfate concentration range of the lithium sulfate solution to be electrolyzed, control the bipolar membrane electrolysis device to work for the current target duration. Within the current target duration, detect the lithium sulfate concentration in the salt chamber and detect the pH of the discharge zone of storage tank 2 to determine the current rate of increase of the current lithium sulfate concentration in the salt chamber within the current target duration. S42: Determine the current equivalent total pure water replenishment flow rate based on the current rate of increase of lithium sulfate concentration in the salt chamber within the current target time, the current range of lithium sulfate concentration in the lithium sulfate solution to be electrolyzed, and the corresponding water replenishment correlation mechanism. S43: Control the pure water to be supplied to the bipolar membrane electrolyzer at the current equivalent total pure water supply flow rate and maintain the electrolysis control parameters of S41 to continue electrolysis, and determine the current water supply flow rate of the second storage tank to the salt chamber and the current pure water supply flow rate of the salt chamber based on the pH of the discharge zone of the second storage tank detected within the current target time. S44: Based on S43, determine the current water supply flow rate of the salt chamber from the second storage tank and the current pure water supply flow rate from the salt chamber, and maintain the electrolysis control parameters of S41 to continue electrolysis; and periodically detect the pH of the discharge zone of the second storage tank; Based on the pH of the discharge zone of storage tank 2, determine whether to update the latest water supply flow rate of storage tank 2 to the salt chamber and the pure water supply flow rate of the salt chamber. If an update is needed, use the updated water supply flow rate to continue electrolysis. Periodically return to execute S41 once. When the range of lithium sulfate concentration change rate of the lithium sulfate solution to be electrolyzed is determined, execute S42-S44 again in sequence.

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