Method and system for continuously extracting lithium by utilizing waste materials

Abstract

The invention discloses a method and a system for continuously extracting lithium by utilizing waste materials. The method comprises the following steps: step 1, a continuous ball milling step; 2, a continuous sodium removal step; adding bottom water into a sodium removal reaction kettle, transferring the ball-milled slurry into the sodium removal reaction kettle, and starting stirring; heating the slurry in the sodium removal reaction kettle to 25-100 DEG C; lime milk is added and stirred, so that the lime milk reacts with the slurry, and precipitates are obtained after the reaction; 3, continuously extracting lithium; the method comprises the following steps: preparing insoluble solids and reuse water according to a mass ratio of 1: (0.5-10) in a continuous lithium extraction reaction kettle, starting stirring, and adding sulfuric acid; adding lime milk to convert aluminum sulfate into insoluble aluminum hydroxide and calcium sulfate precipitates; 4, a continuous impurity removal step; 5, continuously depositing lithium; adding the impurity-removed lithium sulfate solution and a sodium carbonate solution into a continuous lithium precipitation reaction kettle, and heating to carry out a lithium precipitation reaction so as to precipitate lithium carbonate; and carrying out solid-liquid separation to obtain lithium carbonate and lithium precipitation mother liquor. According to the invention, continuous lithium extraction can be realized, and the whole process is controllable.

Description

Technical Field

[0001] The invention relates to a method and a system for continuously extracting lithium from waste materials. Background Art

[0002] There are three traditional methods for lithium extraction:

[0003] 1. Lithium is extracted from lithium ore (spodumene); spodumene is called spodumene in English, and its composition is LiAl(SiO3)2 or Li2O·Al2O3·4SiO2, with a theoretical lithium content of 3.75% (lithium oxide 8.04%). As a raw material for lithium chemical products, it is widely used in lithium chemical, glass and ceramic industries, and enjoys the reputation of "industrial monosodium glutamate".

[0004] 2. Lithium Extraction from Salt Lakes

[0005] The technology of lithium extraction from salt lakes began to be developed in the 1970s. In the 1990s, foreign companies achieved breakthroughs in the technology of lithium extraction from brine. The production cost of lithium carbonate is much lower than that of lithium extraction from ores. Lithium extraction from brine has become a major development trend in the future.

[0006] The main methods of extracting lithium from salt lakes include precipitation, salt gradient solar pool, nanofiltration and electrodialysis, extraction, adsorption, one lake one method and multiple methods coupling. (See "Discarding Stone into Gold - A Brief Introduction to Lithium Extraction from Salt Lakes", https: / / www.sohu.com / a / 484409571_121124376)

[0007] 3. Lithium battery recycling to extract lithium carbonate

[0008] With the rapid development of new energy vehicles, the demand for lithium has also grown rapidly. China's external dependence on lithium resources has been around 70% for a long time, and it is necessary to vigorously ensure the self-sufficiency rate. How to find a suitable lithium source efficiently and at low cost is also the goal pursued by the industry, and waste aluminum electrolyte is also one of the goals. The electrolytic aluminum industry usually adopts the cryolite-alumina molten salt electrolysis method. The aluminum electrolyte is composed of cryolite (Na3AlF6), alumina (Al2O3) and other salt additives (such as AlF3, CaF2, MgF2, LiF), and the lithium element is embedded in the form of a solid solution. However, the electrolyte system with a high lithium salt content after long-term accumulation will cause the electrolytic cell temperature to be low, the solubility of alumina is poor, the bottom of the electrolytic cell is more precipitated, and the stability of the aluminum electrolytic cell is poor. Therefore, in order to make the electrolytic cell operate normally and stably, the electrolyte level and total amount must be controlled. The electrolytic cell that has been running for a period of time usually needs to precipitate excess electrolyte to control its balance. This part of the precipitated electrolyte is the waste aluminum electrolyte. According to the "National List of Hazardous Wastes" (2021 edition), this type of waste is not classified as hazardous waste.

[0009] The power of new energy vehicles mainly comes from lithium-ion battery packs, so the recycling and treatment of waste lithium-ion batteries has become the primary problem that the lithium battery industry needs to solve.

[0010] At present, the recycling steps of waste lithium-ion batteries are: ① prepare lithium-fluorine slag; ② slurry the lithium-fluorine slag with water, add a leaching agent to dissolve the lithium in the lithium-fluorine slag in water, filter, and obtain a crude lithium solution; ③ adjust the pH value with an alkaline reagent to remove impurities in the crude lithium solution to obtain a refined lithium solution; ④ add carbonate to the refined lithium solution for precipitation to obtain crude lithium carbonate. Lithium carbonate is a key material for synthesizing lithium iron phosphate, and lithium iron phosphate is mainly used in various lithium-ion batteries. Therefore, the recovery and synthesis of lithium carbonate plays a key role in the recycling and reuse of lithium-ion batteries. However, the current recycling method has the following disadvantages: ① the battery disassembly process is poor in safety; ② the process of disassembling the battery to prepare lithium-fluorine slag is easy to introduce metal impurities; ③ the impurity removal process is complicated; ④ the recycling cost is high and the recycling efficiency is low.

[0011] Therefore, it is necessary to design a new method and system for extracting lithium using waste electrolytes. Summary of the invention

[0012] The technical problem to be solved by the present invention is to provide a method and system for continuously extracting lithium from waste materials. The method and system for continuously extracting lithium from waste materials are easy to implement and the process is controllable.

[0013] The technical solution of the invention is as follows:

[0014] A method for continuously extracting lithium from waste materials, comprising a ball milling step and a lithium extraction step;

[0015] Step 1, continuous ball milling step: putting the raw material waste aluminum electrolyte and water into a ball mill at a mass ratio of 1:0.5-10 for ball milling, and the formed ball milling slurry is used for standby;

[0016] The waste aluminum electrolyte contains Na3AlF6;

[0017] Step 2, lithium extraction step;

[0018] The ball-milled slurry is used in a series of reactors to achieve continuous lithium extraction;

[0019] Series connection means that each reactor is sequentially connected to a common reaction liquid overflow tank; both the reactor inflow pipe and the reaction liquid overflow pipe are provided with a first electric control valve; the reaction liquid overflow tank is provided with a plurality of second electric control valves; both the first electric control valve and the second electric control valve are controlled by a controller;

[0020] Step 21: continuous sodium removal step;

[0021] Add bottom water to the sodium removal reactor in the reactor, transfer the ball mill slurry into the sodium removal reactor and start stirring; control the slurry temperature in the sodium removal reactor to 25-100° C.; then add lime milk and stir to make the lime milk react with the slurry to obtain a precipitate after the reaction;

[0022] The molar number of calcium hydroxide added to the lime milk is 0.4 to 2 times the molar number of fluorine in the slurry;

[0023] The precipitates include lithium aluminate (LiAlO2), aluminum hydroxide (Al(OH)3), and calcium fluoride (CaF2);

[0024] The reaction is completed when the mass content of Na in the precipitate after the reaction reaches 0.2 to 17%; the Na here refers to the sodium in the reactants that have not reacted completely.

[0025] The slurry is then separated into solid and liquid, and after the insoluble solid is washed, the remaining insoluble solid enters the next step; the entire lithium extraction process is: solid → dissolve a part of the solid → wash the remaining solid → dissolve the remaining solid into solution → remove impurities from the solution → precipitate into solid → finished lithium carbonate, so this step requires solid-liquid separation.

[0026] Step 22: continuous lithium extraction step;

[0027] In a continuous lithium extraction reactor in a reactor, insoluble solids and water (preferably recycled water) are prepared in a mass ratio of 1:0.5-10, stirring is started, and sulfuric acid is added; the molar number of sulfuric acid added is 0.2-2 times the molar number of Na; lithium in the insoluble solids is leached to obtain a mixed solution containing lithium sulfate, sodium sulfate and aluminum sulfate, and then lime milk is added until the slurry pH is 7-14, and the aluminum sulfate is converted into insoluble aluminum hydroxide and calcium sulfate precipitate;

[0028] The slurry is subjected to solid-liquid separation to form a dilute lithium sulfate solution and a filter residue;

[0029] Step 23: continuous impurity removal step;

[0030] The dilute lithium sulfate solution is pumped into the continuous impurity removal reactor in the reactor, hydrogen peroxide is first added, and the temperature of the slurry is controlled to be 20-100°C; (preferably 30-85°C, such as heating to 80°C), lime milk is added to adjust the pH value of the solution to 8-14, the fluorine in the solution combines with calcium ions to precipitate, and then sodium carbonate is added to remove calcium; barium sulfide is then added to remove heavy metals (such as nickel, zinc, etc.), and the solution is allowed to stand for clarification, and the supernatant is transported to the next step (i.e., lithium precipitation process);

[0031] Wherein: the molar number of hydrogen peroxide added is 0.2 to 2 times the molar number of ferrous ions;

[0032] The molar number of sodium carbonate added is 0.6 to 5 times the molar number of calcium ions

[0033] The molar number of barium sulfide added is 0.6 to 5 times the sum of the molar numbers of nickel and zinc in the solution;

[0034] Step 24: continuous lithium deposition step;

[0035] The impurity-removed lithium sulfate solution and pure alkali solution are added to a continuous lithium precipitation reaction kettle in a reaction kettle, and the temperature is raised to 20-95° C. to perform lithium precipitation reaction, so that lithium carbonate is precipitated (lithium precipitation rate is about 98%); the molar number of sodium carbonate added is 0.6-3 times the molar number of lithium sulfate;

[0036] After solid-liquid separation, lithium carbonate and lithium precipitation mother liquor are obtained.

[0037] Also includes step 3: a continuous drying step;

[0038] After the lithium carbonate is dried in a dryer, it is crushed by a jet mill to finally obtain battery-grade lithium carbonate.

[0039] The mass ratio of the raw material waste aluminum electrolyte to water is 1:3; grind to a particle size median diameter D50 = 1-100 μm. In step 2: the amount of bottom water added is 20% of the volume of the sodium removal reactor; the slurry temperature in the sodium removal reactor is controlled to be 80°C; the stirring reaction time is 4-8 hours;

[0040] The molar number of calcium hydroxide added to the lime milk is 0.5 to 0.8 times the molar number of fluorine in the slurry;

[0041] The reaction is completed when the mass content of Na in the precipitate after the reaction reaches 1.2-5%;

[0042] In step 2:

[0043] Insoluble solid and water are prepared in a mass ratio of 1:1-3;

[0044] The temperature is controlled below 100°C to prevent the slurry from escaping from the reactor due to boiling.

[0045] In step 2: the molar number of hydrogen peroxide added is 0.6 to 0.8 times the molar number of ferrous ions;

[0046] Adjust the solution pH to 9;

[0047] Control the temperature of the slurry to 30-85°C (preferably heated to 80°C);

[0048] The molar number of sodium carbonate added is 1.1 to 1.8 times the molar number of calcium ions;

[0049] The molar number of barium sulfide added is 1.1 to 1.8 times the sum of the molar numbers of nickel and zinc in the solution.

[0050] In step 2: the molar number of sodium carbonate added is 1.1 to 1.8 times the molar number of lithium sulfate.

[0051] In order to realize continuous lithium extraction and provide controllability of the entire process, multiple reactors are connected in series; the series connection means that each reactor is sequentially connected to a common reaction liquid overflow tank; the reactor inflow pipe and the reaction liquid overflow pipe are both provided with a first electric control valve; the reaction liquid overflow tank is provided with multiple second electric control valves; the first electric control valve and the second electric control valve are both controlled by a controller;

[0052] At least two reactors are configured for each step in step 21 to step 24, and at least one reactor is reserved as a backup.

[0053] A system for continuously extracting lithium from waste materials, comprising N cascaded reactors and a reaction liquid overflow tank;

[0054] N≥4; N is an integer;

[0055] The reactor is arranged in one of two ways:

[0056] Mode 1: Each reactor is sequentially mounted on a common reaction liquid overflow tank; multiple reactors are arranged in a row and staggered from high to low; the reaction liquid overflow tank is arranged obliquely; (N reactors are arranged in a staggered manner in height (i.e. arranged in a gradient), and the reaction liquid overflow tank is arranged obliquely in the descending direction of the height of the reactor)

[0057] Mode 2: N reactors are divided into M groups; each group includes at least 2 reactors; and M≥4, M is an integer; each group of reactors is sequentially connected to a common reaction liquid overflow tank, and the reaction liquid overflow tanks of adjacent groups are connected through a connecting pipe with a third electric control valve; M groups of reactors are arranged in a stepped manner; the distance between adjacent groups of reactors is not less than the height of the reactor body;

[0058] A stirring mechanism is provided in the reactor;

[0059] The first reactor has a reaction liquid overflow pipe; the remaining reactors all have a reactor inflow pipe and a reaction liquid overflow pipe; the reactor inflow pipe and the reaction liquid overflow pipe are both provided with a first electric control valve;

[0060] A plurality of second electric-controlled valves are provided on the reaction liquid overflow tank;

[0061] The first electrically controlled valve and the second electrically controlled valve are both controlled by a controller;

[0062] Under the control of the controller, the reaction kettle and the reaction liquid overflow tank are controlled by the aforementioned method to implement continuous lithium extraction.

[0063] N is 8 to 12. Each link corresponds to at least 2 reactors, and at least 2 reactors are reserved for backup.

[0064] Beneficial effects:

[0065] The method and system for continuously extracting lithium from waste materials of the present invention adopt waste aluminum electrolyte as the main raw material, and prepare battery-grade lithium carbonate through wet continuous ball milling, continuous sodium removal, continuous lithium extraction, continuous deep impurity removal, continuous lithium precipitation, continuous drying and packaging and other processes.

[0066] The traditional refining method is to complete all steps in one reactor, which has high requirements for process control and unstable output. Once there are some mistakes in the actual operation, it is not easy to adjust. The feature of the present invention is that it can achieve continuous lithium extraction, such as connecting multiple reactors in series, controlling the solution flow rate, reaction time and the amount of each substance added, so as to achieve full process control. Each step corresponds to multiple reactors, and a spare reactor is also set up, so that each step can be controlled in sections, thereby ensuring the final output and high recovery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a continuous lithium extraction flow chart;

[0068] Figure 2 It is a schematic diagram of cascade of 8 reactors (main cross-sectional view);

[0069] Figure 3 It is a schematic diagram of the structure of the reactor (front cross-sectional view);

[0070] Figure 4 This is the connection view between the reactor and the overflow tank (top view);

[0071] Figure 5 This is the system electrical control block diagram;

[0072] Figure 6 It is a schematic diagram of cascade of 12 reactors (top view);

[0073] Figure 7 This is a stepped layout view of a 4-stage reactor (side view).

[0074] Explanation of reference numerals: 1-reaction kettle, 2-reaction liquid overflow tank, 3-reaction liquid inflow pipe, 4-reaction liquid outflow pipe, 5-first electric control valve, 6-second electric control valve, 7-stirring mechanism, 8-reaction liquid diversion mechanism, 9-feeding pipe, 10-connecting pipe, 11-third electric control valve. DETAILED DESCRIPTION

[0075] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0076] Example 1: Figure 1-4 , a method for continuous lithium extraction from waste materials, the preparation process is as follows:

[0077] 1. Continuous ball milling

[0078] The raw material waste aluminum electrolyte and clean water or recycled water are put into the ball mill at a mass ratio of 1:3. After grinding to a certain particle size (median diameter D50 = 16μm), the slurry is transferred to the transfer barrel.

[0079] 2. Lithium extraction steps

[0080] Step 21: Continuous sodium removal

[0081] Add an appropriate amount of bottom water (accounting for 20% of the volume of the reactor) to the continuous sodium removal reactor, pump the ball mill slurry into the reactor and start stirring (the stirring speed is preferably 100r / min), heat to 80°C, add lime milk, stir and react for 6 hours, and generate sodium hydroxide and insoluble lithium aluminate, aluminum hydroxide and calcium fluoride precipitates. Pump the slurry into the filter press for solid-liquid separation to separate the dilute alkali solution and insoluble solids, and wash the solids with water for standby use. The dilute alkali solution and washing water can be used as recycled water. The reaction process is as follows:

[0082] 2Na3AlF6+6Ca(OH)2=5NaOH+NaAlO2+Al(OH)3↓+6CaF2↓+2H2O

[0083] 2LiF+Ca(OH)2+2NaAlO2=2NaOH+2LiAlO2↓+CaF2↓

[0084] The reaction is completed when the Na content in the precipitate after the reaction reaches 3% by mass.

[0085] Step 22. Continuous lithium extraction

[0086] In a continuous lithium extraction reactor, insoluble solids and recycled water are prepared in a mass ratio of 1:3, stirring is started (the stirring speed is preferably 40-200r / min), and concentrated sulfuric acid at 100°C is slowly added to avoid boiling of the solution.

[0087] The molar number of sulfuric acid added is 0.7 of the molar number of Na, and the lithium in the insoluble solid is leached to obtain a mixed solution containing lithium sulfate, sodium sulfate and aluminum sulfate, etc., and then an appropriate amount of lime milk is added to the slurry pH to 10 to convert the aluminum sulfate into insoluble aluminum hydroxide and calcium sulfate precipitate. The above slurry is pumped into a filter press for solid-liquid separation to obtain a dilute lithium sulfate solution and a filter residue, and the filter residue is washed with water. The dilute lithium sulfate solution is used for subsequent refining and impurity removal, and the washing water is reused for the pulping and batching process before acidification. The filter residue is solids such as calcium sulfate, aluminum hydroxide, and calcium fluoride. After washing, it is sold as a building material additive or transported to landfill. The reaction process is as follows:

[0088] 2NaOH+H2SO4=Na2SO4+2H2O

[0089] 2LiAlO2+4H2SO4=Li2SO4+Al2(SO4)3+4H2O

[0090] 2NaAlO2+4H2SO4=Na2SO4+Al2(SO4)3+4H2O

[0091] Al2(SO4)3+3Ca(OH)2=2Al(OH)3↓+3CaSO4↓

[0092] Step 23. Continuous deep cleaning

[0093] The dilute lithium sulfate solution is pumped into a continuous impurity removal reactor, and a certain amount of hydrogen peroxide is first added (the molar number of hydrogen peroxide added is 0.7 times the molar number of ferrous ions), and then heated to 80°C by steam, and lime milk is added to adjust the pH value of the solution to 9. The fluoride in the solution combines with the calcium ions to precipitate, and then an appropriate amount of sodium carbonate is added (the molar number of sodium carbonate added is 1.5 times the molar number of calcium ions) to remove calcium, and an appropriate amount of barium sulfide is added (the molar number of barium sulfide added is 1.5 times the sum of the molar numbers of nickel and zinc in the solution) to remove heavy metals such as nickel and zinc. The precipitate is allowed to stand and clarified, and the precipitate is washed and filtered and sold as a building material additive or transported to landfill, and the supernatant is transported to the next process to precipitate lithium.

[0094] H2O2+2Fe 2+ +2H + =2Fe 3+ +2H2O

[0095] 3OH - +2Fe 2+ =2Fe(OH)3↓

[0096] 2F - +Ca(OH)2=CaF2↓+2OH -

[0097] Al2(SO4)3+3Ca(OH)2=2Al(OH)3↓+3CaSO4↓

[0098] Ca 2+ +CO3 2- =CaCO3↓

[0099] Step 24. Continuous lithium deposition

[0100] The impurity-free lithium sulfate solution and pure alkali solution are added to the continuous lithium precipitation reactor. The molar number of sodium carbonate added is 1.2 times the molar number of lithium sulfate. The temperature is raised to 85°C for lithium precipitation reaction. Lithium carbonate precipitates due to its low solubility. The lithium precipitation rate is about 98%. The lithium carbonate precipitate is centrifuged while hot to separate lithium carbonate and lithium precipitation mother liquor, and then washed online with pure water. The lithium precipitation mother liquor and washing water are sent for purification and impurity removal.

[0101] Li2SO4+Na2CO3=Li2CO3↓+Na2SO4

[0102] 3. Continuous dry packaging

[0103] After the lithium carbonate is washed, dehydrated and separated by a centrifuge, it is added to a dryer for drying. After drying, it is crushed by a jet mill to finally obtain battery-grade lithium carbonate (in compliance with the industry standard "YS / T 582-2023 Lithium Carbonate"), which is packaged by an automatic packaging machine and sent to the finished product warehouse for storage.

[0104] The lithium recovery rate of Example 1 reaches 98%. Currently, the lithium recovery rates of lithium extraction from ores and salt lakes are generally lower than 80%, which shows that the advantage is obvious.

[0105] Embodiment 2:

[0106] like Figure 1-4 , a method for continuous lithium extraction from waste materials, the preparation process is as follows:

[0107] 1. Continuous ball milling

[0108] The raw material waste aluminum electrolyte and clean water or recycled water are put into the ball mill in a mass ratio of 1:1. After grinding to a certain particle size (median diameter D50 = 60μm), the slurry is transferred to the transfer barrel.

[0109] 2. Lithium extraction steps

[0110] Step 21: Continuous sodium removal

[0111] Add an appropriate amount of bottom water (accounting for 10% of the volume of the reactor) to the continuous sodium removal reactor, pump the ball mill slurry into the reactor and start stirring (the stirring speed is preferably 100r / min), heat to 40°C, add lime milk, stir and react for 2 hours, and generate sodium hydroxide and insoluble lithium aluminate, aluminum hydroxide and calcium fluoride precipitates. Pump the slurry into the filter press for solid-liquid separation to separate the dilute alkali solution and insoluble solids, and wash the solids with water for standby use. The dilute alkali solution and washing water can be used as recycled water. The reaction process is as follows:

[0112] 2Na3AlF6+6Ca(OH)2=5NaOH+NaAlO2+Al(OH)3↓+6CaF2↓+2H2O

[0113] 2LiF+Ca(OH)2+2NaAlO2=2NaOH+2LiAlO2↓+CaF2↓

[0114] The reaction is completed when the Na content in the precipitate after the reaction reaches 3% by mass.

[0115] Step 22. Continuous lithium extraction

[0116] In a continuous lithium extraction reactor, insoluble solids and recycled water are prepared in a mass ratio of 1:1, stirring is started (the stirring speed is preferably 40-200r / min), concentrated sulfuric acid is slowly added, and the temperature is preferably controlled at 80°C to avoid boiling of the solution.

[0117] The molar number of sulfuric acid added is 0.4 times the molar number of Na, and the lithium in the insoluble solid is leached to obtain a mixed solution containing lithium sulfate, sodium sulfate and aluminum sulfate, etc., and then an appropriate amount of lime milk is added to the slurry pH to 8 to convert the aluminum sulfate into insoluble aluminum hydroxide and calcium sulfate precipitate. The above slurry is pumped into a filter press for solid-liquid separation to obtain a dilute lithium sulfate solution and a filter residue, and the filter residue is washed with water. The dilute lithium sulfate solution is used for subsequent refining and impurity removal, and the washing water is reused for the pulping and batching process before acidification. The filter residue is solids such as calcium sulfate, aluminum hydroxide, and calcium fluoride. After washing, it is sold as a building material additive or transported to landfill. The reaction process is as follows:

[0118] 2NaOH+H2SO4=Na2SO4+2H2O

[0119] 2LiAlO2+4H2SO4=Li2SO4+Al2(SO4)3+4H2O

[0120] 2NaAlO2+4H2SO4=Na2SO4+Al2(SO4)3+4H2O

[0121] Al2(SO4)3+3Ca(OH)2=2Al(OH)3↓+3CaSO4↓

[0122] Step 23. Continuous deep cleaning

[0123] The dilute lithium sulfate solution is pumped into a continuous impurity removal reactor, and a certain amount of hydrogen peroxide is first added (the molar number of hydrogen peroxide added is 0.4 times the molar number of ferrous ions), and then heated to 50°C by steam, and lime milk is added to adjust the pH value of the solution to 8. The fluoride in the solution combines with the calcium ions to precipitate, and then an appropriate amount of sodium carbonate is added (the molar number of sodium carbonate added is 0.8 times the molar number of calcium ions) to remove calcium, and an appropriate amount of barium sulfide is added (the molar number of barium sulfide added is 0.9 times the sum of the molar numbers of nickel and zinc in the solution) to remove heavy metals such as nickel and zinc. The precipitate is allowed to stand and clarified, and the precipitate is washed and filtered and sold as a building material additive or transported to landfill, and the supernatant is transported to the next process to precipitate lithium.

[0124] H2O2+2Fe 2+ +2H + =2Fe 3+ +2H2O

[0125] 3OH - +2Fe 2+ =2Fe(OH)3↓

[0126] 2F - +Ca(OH)2=CaF2↓+2OH -

[0127] Al2(SO4)3+3Ca(OH)2=2Al(OH)3↓+3CaSO4↓

[0128] Ca 2+ +CO3 2- =CaCO3↓

[0129] Step 24. Continuous lithium deposition

[0130] The lithium sulfate solution and pure alkali solution after impurities removal are added to the continuous lithium precipitation reactor. The molar number of sodium carbonate added is 0.8 times the molar number of lithium sulfate. The temperature is raised to 60°C for lithium precipitation reaction. Lithium carbonate precipitates due to its low solubility. The lithium precipitation rate is about 90%. The lithium carbonate precipitate is centrifuged while hot to separate lithium carbonate and lithium precipitation mother liquor, and then washed online with pure water. The lithium precipitation mother liquor and washing water are sent for purification and impurity removal.

[0131] Li2SO4+Na2CO3=Li2CO3↓+Na2SO4

[0132] 3. Continuous dry packaging

[0133] After the lithium carbonate is washed, dehydrated and separated by a centrifuge, it is added to a dryer for drying. After drying, it is crushed by a jet mill to finally obtain battery-grade lithium carbonate (in compliance with the industry standard "YS / T 582-2023 Lithium Carbonate"), which is packaged by an automatic packaging machine and sent to the finished product warehouse for storage.

[0134] The lithium recovery rate of Example 2 reaches 91%. Currently, the lithium recovery rates of lithium extraction from ores and salt lakes are generally lower than 80%, which shows that the advantage is obvious.

[0135] Embodiment 3:

[0136] like Figure 1-4 , a method for continuous lithium extraction from waste materials, the preparation process is as follows:

[0137] 1. Continuous ball milling

[0138] The raw material waste aluminum electrolyte and clean water or recycled water are put into the ball mill at a mass ratio of 1:6. After grinding to a certain particle size (median diameter D50 = 5μm), the slurry is transferred to the transfer barrel.

[0139] 2. Lithium extraction steps

[0140] Step 21: Continuous sodium removal

[0141] Add an appropriate amount of bottom water (accounting for 30% of the volume of the reactor) to the continuous sodium removal reactor, pump the ball mill slurry into the reactor and start stirring (the stirring speed is preferably 100r / min), heat to 95°C, add lime milk, stir and react for 8 hours, and generate sodium hydroxide and insoluble lithium aluminate, aluminum hydroxide and calcium fluoride precipitates. Pump the slurry into the filter press for solid-liquid separation to separate the dilute alkali solution and insoluble solids, and wash the solids with water for standby use. The dilute alkali solution and washing water can be used as recycled water. The reaction process is as follows:

[0142] 2Na3AlF6+6Ca(OH)2=5NaOH+NaAlO2+Al(OH)3↓+6CaF2↓+2H2O

[0143] 2LiF+Ca(OH)2+2NaAlO2=2NaOH+2LiAlO2↓+CaF2↓

[0144] The reaction is completed when the Na content in the precipitate after the reaction reaches 3% by mass.

[0145] Step 22. Continuous lithium extraction

[0146] In a continuous lithium extraction reactor, insoluble solids and recycled water are prepared in a mass ratio of 1:8, stirring is started (the stirring speed is preferably 40-200r / min), concentrated sulfuric acid is slowly added, and the temperature is preferably controlled at 95°C to avoid boiling of the solution.

[0147] The molar number of sulfuric acid added is 1.5 times the molar number of Na, and the lithium in the insoluble solid is leached to obtain a mixed solution containing lithium sulfate, sodium sulfate and aluminum sulfate, etc., and then an appropriate amount of lime milk is added to the slurry pH to 13 to convert the aluminum sulfate into insoluble aluminum hydroxide and calcium sulfate precipitate. The above slurry is pumped into a filter press for solid-liquid separation to obtain a dilute lithium sulfate solution and a filter residue, and the filter residue is washed with water. The dilute lithium sulfate solution is used for subsequent refining and impurity removal, and the washing water is reused for the pulping and batching process before acidification. The filter residue is solids such as calcium sulfate, aluminum hydroxide, and calcium fluoride. After washing, it is sold as a building material additive or transported to landfill. The reaction process is as follows:

[0148] 2NaOH+H2SO4=Na2SO4+2H2O

[0149] 2LiAlO2+4H2SO4=Li2SO4+Al2(SO4)3+4H2O

[0150] 2NaAlO2+4H2SO4=Na2SO4+Al2(SO4)3+4H2O

[0151] Al2(SO4)3+3Ca(OH)2=2Al(OH)3↓+3CaSO4↓

[0152] Step 23. Continuous deep cleaning

[0153] The dilute lithium sulfate solution is pumped into a continuous impurity removal reactor, and a certain amount of hydrogen peroxide is first added (the molar number of hydrogen peroxide added is 1.5 times the molar number of ferrous ions), and then heated to 95°C by steam, and lime milk is added to adjust the pH value of the solution to 13. The fluoride in the solution combines with the calcium ions to precipitate, and then an appropriate amount of sodium carbonate is added (the molar number of sodium carbonate added is 4 times the molar number of calcium ions) to remove calcium, and an appropriate amount of barium sulfide is added (the molar number of barium sulfide added is 4.5 times the sum of the molar numbers of nickel and zinc in the solution) to remove heavy metals such as nickel and zinc. The precipitate is allowed to stand and clarified, and the precipitate is washed and filtered and sold as a building material additive or transported to landfill, and the supernatant is transported to the next process to precipitate lithium.

[0154] H2O2+2Fe 2+ +2H + =2Fe 3+ +2H2O

[0155] 3OH - +2Fe 2+ =2Fe(OH)3↓

[0156] 2F - +Ca(OH)2=CaF2↓+2OH -

[0157] Al2(SO4)3+3Ca(OH)2=2Al(OH)3↓+3CaSO4↓

[0158] Ca 2+ +CO3 2- =CaCO3↓

[0159] Step 24. Continuous lithium deposition

[0160] The lithium sulfate solution and pure alkali solution after impurities removal are added to the continuous lithium precipitation reactor. The molar number of sodium carbonate added is 2.2 times the molar number of lithium sulfate. The temperature is raised to 95°C for lithium precipitation reaction. Lithium carbonate precipitates due to its low solubility. The lithium precipitation rate is about 93%. The lithium carbonate precipitate is centrifuged while hot to separate lithium carbonate and lithium precipitation mother liquor, and then washed online with pure water. The lithium precipitation mother liquor and washing water are sent for purification and impurity removal.

[0161] Li2SO4+Na2CO3=Li2CO3↓+Na2SO4

[0162] 3. Continuous dry packaging

[0163] After the lithium carbonate is washed, dehydrated and separated by a centrifuge, it is added to a dryer for drying. After drying, it is crushed by a jet mill to finally obtain battery-grade lithium carbonate (in compliance with the industry standard "YS / T 582-2023 Lithium Carbonate"), which is packaged by an automatic packaging machine and sent to the finished product warehouse for storage.

[0164] The lithium recovery rate of Example 3 reaches 94%. At present, the lithium recovery rates of lithium extraction from ores and salt lakes are generally lower than 80%, which shows that the advantage is obvious.

[0165] Example 1 of the system:

[0166] like Figure 1-4 , a system for continuous lithium extraction from waste materials, comprising N cascaded reactors and reaction liquid overflow tanks; N is 8; each reactor is sequentially connected to a common reaction liquid overflow tank;

[0167] The reactor is provided with a stirring mechanism; the first reactor is provided with a reaction liquid overflow pipe; the remaining reactors are provided with a reactor inflow pipe and a reaction liquid overflow pipe; the reactor inflow pipe and the reaction liquid overflow pipe are both provided with a first electric control valve; the reaction liquid overflow tank is provided with a plurality of second electric control valves;

[0168] The first electrically controlled valve and the second electrically controlled valve are both controlled by a controller; the N reactors are arranged in a staggered manner in height (ie arranged in a gradient), and the reaction liquid overflow tank is arranged in an inclined manner in the descending direction of the height of the reactor.

[0169] Under the control of the controller, the reaction kettle and the reaction liquid overflow tank are controlled by the above method.

[0170] Continuous lithium extraction is carried out. N is 8-12.

[0171] The number of reactors should be 8 to 12 ( Figure 2 In principle, each link corresponds to 2 reactors, and at least 2 reactors are reserved for backup. Each reactor can complete all reaction links. If abnormal situations occur due to material changes, equipment failures, human factors, etc., the subsequent reactors can also complete the remaining reactions.

[0172] Features of the system:

[0173] 1. When more than 8 (including 8) reactors are arranged and used for continuous reaction, any 3 or more of them can complete the reaction and can be switched at any time. The controller can switch which reactor to use through the first electric control valve and the second control valve, and can also control whether the reaction liquid passes through or bypasses a reactor by controlling the second valve.

[0174] 2. The reactors are arranged from high to low to save energy.

[0175] 3. The reactor inlet is arranged at the upper, middle and lower parts of the reactor body. The heavy material inlet is arranged at the upper part, and the light material enters from the lower part, which is beneficial to the uniformity of material reaction.

[0176] 4. Multiple flow guide devices are arranged inside the reactor to facilitate full reaction.

[0177] 5. The overflow port of the reaction liquid is generally arranged in the middle and upper part of the kettle body. Generally, the specific gravity of the qualified liquid in the solid-liquid phase reaction will be smaller than that of the solid phase.

[0178] 6. Each reactor inlet and outlet are equipped with automatically controllable baffles to control flow and opening and closing.

[0179] 7. Angle cuts are set around the bottom of the reactor to prevent material deposition.

[0180] 8. A heating device is installed inside the reactor.

[0181] 9. The reactor is equipped with a stirring device, usually with multiple layers of blades, so that materials with different specific gravities can be fully mixed and reacted.

[0182] Example 2 of the system:

[0183] like Figure 3-6 , which is different from system embodiment 1 in that multiple reactors are arranged in stages (groups), specifically:

[0184] A total of 12 reactors are used, divided into 3 groups; each group includes 3 reactors; each group of reactors (the positions can be aligned or staggered) are sequentially connected to a common reaction liquid overflow tank, and the reaction liquid overflow tanks of adjacent groups are connected through a connecting pipeline with a third electric control valve; 4 groups of reactors are arranged in a stepped manner; the staggered distance between adjacent groups of reactors is not less than the height of the reactor body;

[0185] The system also includes a process control system (the method of the present invention may also include the following control strategies):

[0186] The cascade lithium extraction reactor includes N reactors, and the N reactors are divided into M groups; each group includes at least 2 reactors; M and N are both natural numbers; and M≥4; N≥8; M groups of reactors are arranged in a stepped manner; each group of reactors is connected through a reaction liquid overflow tank; the reaction liquid overflow tanks of the reactors in adjacent groups are communicated through connecting pipes; each reactor is equipped with a field controller for controlling the reactor; the field controller is used to control the on-off of the slurry inflow and outflow channel of the current reactor through the first electric control valve, and the field controller also controls the on-off of the reactor overflow tank through the second electric control valve; the field controller also controls the on-off of the connecting pipeline through the third electric control valve; the control center is connected to multiple field controllers through field bus communication. The field bus is a CAN bus. A temperature sensor, a stirring mechanism and a heating mechanism are provided in the reactor; the temperature sensor is connected to the data acquisition end of the field controller, and the stirring mechanism and the heating mechanism are controlled by the field controller. The field controller adopts a DSP or PLC processor. The control center adopts an industrial computer; the control center is connected to the cloud server through communication. This solution is adopted: for a certain process step, the control center can select 1, 2 or 3 reactors in the corresponding group to participate in the work; therefore, the entire control is flexible and convenient. If the number of layers (i.e., the number of groups) is 5 or 6, four groups (i.e., four layers) can be selected to participate in the process, and the other groups are used as backup.

[0187] Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for continuous lithium extraction from waste materials, characterized in that: It includes a ball milling step and a lithium extraction step; Step 1, continuous ball milling step: putting the raw material waste aluminum electrolyte and water into a ball mill at a mass ratio of 1:0.5-10 for ball milling, and the formed ball milling slurry is used for standby; The waste aluminum electrolyte contains Na3AlF6; Step 2, lithium extraction step; The ball-milled slurry is used in a series of reactors to achieve continuous lithium extraction; Series connection means that each reactor is sequentially connected to a common reaction liquid overflow tank; both the reactor inflow pipe and the reaction liquid overflow pipe are provided with a first electric control valve; the reaction liquid overflow tank is provided with a plurality of second electric control valves; both the first electric control valve and the second electric control valve are controlled by a controller; Step 21: continuous sodium removal step; Add bottom water to the sodium removal reactor in the reactor, transfer the ball mill slurry into the sodium removal reactor and start stirring; control the slurry temperature in the sodium removal reactor to 25-100° C.; then add lime milk and stir to make the lime milk react with the slurry to obtain a precipitate after the reaction; The molar number of calcium hydroxide added to the lime milk is 0.4 to 2 times the molar number of fluorine in the slurry; The precipitates include lithium aluminate (LiAlO2), aluminum hydroxide (Al(OH)3), and calcium fluoride (CaF2); The reaction is completed when the mass content of Na in the precipitate after the reaction reaches 0.2-17%; The slurry is then subjected to solid-liquid separation, the insoluble solids are washed, and the remaining insoluble solids enter the next step; Step 22: continuous lithium extraction step; In a continuous lithium extraction reactor in a reactor, insoluble solids and water are prepared in a mass ratio of 1:0.5-10, stirring is started, and sulfuric acid is added; the molar number of sulfuric acid added is 0.2-2 times the molar number of Na; lithium in the insoluble solids is leached to obtain a mixed solution containing lithium sulfate, sodium sulfate and aluminum sulfate, and then lime milk is added until the slurry pH is 7-14, and the aluminum sulfate is converted into insoluble aluminum hydroxide and calcium sulfate precipitation; The slurry is subjected to solid-liquid separation to form a dilute lithium sulfate solution and a filter residue; Step 23: continuous impurity removal step; The dilute lithium sulfate solution is pumped into the continuous impurity removal reactor in the reactor, hydrogen peroxide is added first, and the temperature of the slurry is controlled to be 20-100°C; lime milk is added to adjust the pH value of the solution to 8-14, and the fluorine in the solution combines with calcium ions to precipitate, and then sodium carbonate is added to remove calcium; barium sulfide is then added to remove heavy metals, and the solution is allowed to stand and clarified, and the supernatant is transported to the next step; Wherein: the molar number of hydrogen peroxide added is 0.2 to 2 times the molar number of ferrous ions; The molar number of sodium carbonate added is 0.6 to 5 times the molar number of calcium ions The molar number of barium sulfide added is 0.6 to 5 times the sum of the molar numbers of nickel and zinc in the solution; Step 24: continuous lithium deposition step; The impurity-removed lithium sulfate solution and pure alkali solution are added to the continuous lithium precipitation reaction kettle in the reaction kettle, and the temperature is raised to 20-95° C. to perform lithium precipitation reaction to precipitate lithium carbonate; the molar number of sodium carbonate added is 0.6-3 times the molar number of lithium sulfate; After solid-liquid separation, lithium carbonate and lithium precipitation mother liquor are obtained.

2. The method for continuous lithium extraction from waste materials according to claim 1, characterized in that: Also includes step 3: a continuous drying step; After the lithium carbonate is dried in a dryer, it is crushed by a jet mill to finally obtain battery-grade lithium carbonate.

3. The method for continuous lithium extraction from waste materials according to claim 1, characterized in that: In step 1: the mass ratio of the raw material waste aluminum electrolyte to water is 1:3; the raw material waste aluminum electrolyte is ground to a particle size median diameter D50 = 1 to 100 μm. In step 2: the amount of bottom water added is 20% of the volume of the sodium removal reactor; the slurry temperature in the sodium removal reactor is controlled to be 80° C.; and the stirring reaction time is 4-8 hours.

4. The method for continuous lithium extraction from waste materials according to claim 3, characterized in that: In step 2: the molar number of calcium hydroxide added to the lime milk is 0.5 to 0.8 times the molar number of fluorine in the slurry; The reaction is completed when the mass content of Na in the precipitate after the reaction reaches 1.2-5%.

5. The method for continuous lithium extraction from waste materials according to claim 4, characterized in that: In step 2: Insoluble solid and water are prepared in a mass ratio of 1:1 to 3; The temperature is controlled below 100℃.

6. The method for continuous lithium extraction from waste materials according to claim 5, characterized in that: In step 2: The molar number of hydrogen peroxide added is 0.6 to 0.8 times the molar number of ferrous ions; Adjust the solution pH to 9; Control the temperature of the slurry to 30-85°C; The molar number of sodium carbonate added is 1.1 to 1.8 times the molar number of calcium ions; The molar number of barium sulfide added is 1.1 to 1.8 times the sum of the molar numbers of nickel and zinc in the solution.

7. The method for continuous lithium extraction from waste materials according to claim 6, characterized in that: In step 2: the molar number of sodium carbonate added is 1.1 to 1.8 times the molar number of lithium sulfate.

8. The method for continuous lithium extraction from waste materials according to claims 1 to 7, characterized in that: In order to realize continuous lithium extraction and provide controllability of the entire process, multiple reactors are connected in series; the series connection means that each reactor is sequentially connected to a common reaction liquid overflow tank; the reactor inflow pipe and the reaction liquid overflow pipe are both provided with a first electric control valve; the reaction liquid overflow tank is provided with multiple second electric control valves; the first electric control valve and the second electric control valve are both controlled by a controller; At least two reactors are configured for each step in step 21 to step 24, and at least one reactor is reserved as a backup.

9. A system for continuous lithium extraction using waste materials, characterized in that: It includes N cascaded reactors and reaction liquid overflow tanks; N≥4; N is an integer; The reactor is arranged in one of two ways: Method 1: Each reactor is sequentially mounted on a common reaction liquid overflow tank; multiple reactors are arranged in a row and staggered from high to low; the reaction liquid overflow tank is arranged obliquely; Mode 2: N reactors are divided into M groups; each group includes at least 2 reactors; and M≥4, M is an integer; each group of reactors is sequentially connected to a common reaction liquid overflow tank, and the reaction liquid overflow tanks of adjacent groups are connected through a connecting pipe with a third electric control valve; M groups of reactors are arranged in a stepped manner; the distance between adjacent groups of reactors is not less than the height of the reactor body; A stirring mechanism is provided in the reactor; The first reactor has a reaction liquid overflow pipe; the remaining reactors all have a reactor inflow pipe and a reaction liquid overflow pipe; the reactor inflow pipe and the reaction liquid overflow pipe are both provided with a first electric control valve; A plurality of second electric-controlled valves are provided on the reaction liquid overflow tank; The first electrically controlled valve and the second electrically controlled valve are both controlled by a controller; Under the control of the controller, the reaction kettle and the reaction liquid overflow tank are controlled by the method described in any one of claims 1 to 8 to implement continuous lithium extraction.

10. The system for continuous lithium extraction from waste materials according to claim 1, characterized in that: N is 8 to 12.

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