Method for recovering lithium

Abstract

The invention relates to a method for concentrating lithium in metallurgical soot, in which a metallurgical charge is smelted to obtain a melt pool comprising a slag phase and optionally an alloy phase, and lithium is fumed from the molten slag by adding a halogen intermediate which is produced from a lithium halide fumed from the molten slag. Thus, the halide is effectively reused in the process, while the lithium is recovered and separated.

Description

Technical Field

[0001] Global lithium consumption has more than doubled in the past decade. This growth is primarily due to the use of lithium in rechargeable lithium-ion batteries. In applications where weight or volume is critical, lithium-ion batteries have become the preferred source of power whenever high energy or power is required. This growth is likely to continue in the coming years: by the end of the 2020s, the annual capacity of lithium-ion batteries to be introduced into the global market is expected to reach hundreds of gigawatt-hours. Background Technology

[0002] Currently used battery chemistry types are diverse, but they are all based on the oxidation and reduction of lithium. Widely used cathode compounds include lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel manganese cobalt oxide (NMC), lithium iron phosphate (LFP), and lithium nickel cobalt aluminum oxide (NCA). At the anode, lithium-graphite intercalation compounds are typical, while lithium metal or lithium titanate (LTO) are also under development. In addition, lithium is also used in the electrolyte in the form of LiPF6. Currently, lithium consumption in lithium-ion batteries accounts for approximately half of total lithium production.

[0003] Lithium is also used in other products, such as lithium primary batteries, as well as lithium-containing glass, ceramics, polymers, casting powders, alloys, greases and pharmaceuticals.

[0004] As can be clearly seen from the above, various types of production waste and end-of-life products contain significant amounts of lithium. If effective methods are developed, the recovery of this lithium could offer a promising industrial prospect.

[0005] To date, lithium recovery from non-battery-related materials has been limited to the reprocessing of certain production wastes, such as in the glass and ceramics industries. Therefore, future focus is expected to be on lithium recovery from lithium-ion batteries.

[0006] Lithium-ion batteries involve complex compounds that often contain particularly valuable metals such as nickel and cobalt. Therefore, research in battery recycling has historically focused on the recovery of these metals, rather than lithium. Several hydrometallurgical methods are described in the literature, employing multiple extraction and purification steps to recover nickel and cobalt from powder derived from lithium-ion battery waste. Lithium is typically diluted in the residual leaching solution from the final step of the hydrometallurgical process. This stream usually flows directly into wastewater treatment facilities without any attempt to recover lithium. However, in rare cases, lithium is still recovered through precipitation; this step typically provides only low recovery yields unless combined with energy-intensive crystallization and evaporation steps.

[0007] As an alternative to a purely hydrometallurgical method, a hybrid approach that includes a first step in pyrometallurgy can be chosen. Pyrometallurgy has well-known advantages in terms of robustness and flexibility in feed composition, allowing specific elements to be easily concentrated in a particular metallurgical phase. Therefore, from a lithium recovery perspective, a variety of lithium-containing wastes can be envisioned, including primary batteries, rechargeable batteries, glass, ceramics, polymers, and casting powders.

[0008] In the context of lithium-ion battery recycling, lithium recovery through pyrometallurgy has been recognized in the "Valorisation of battery recycling slags" (Proceedings of the second international slagvalorisation). The following is described in Symposium (pp. 365-373, April 20, 2011). Lithium is one of the most easily oxidized elements, and it is therefore assumed that it will enter the slag. Subsequently, a hydrometallurgical method for recovering lithium from the slag is described. However, this is a complex task because the lithium in the slag is diluted, resulting in a level of lithium in the diluted leachate that is almost unusable.

[0009] This invention addresses the dilution problem by concentrating lithium in the flue dust generated during smelting operations. Compared to slag, the amount of these flue dusts formed is much smaller, thus providing a more attractive starting product for hydrometallurgical methods. Furthermore, the concentrated lithium flue dust is readily leached, facilitating the purification process. This is achieved by adding a suitable halide source to the smelting furnace.

[0010] It should be noted that the formation and fuming of lithium (in the form of LiCl) using CaCl2 as a chloride source has been described in the context of lithium recovery from spodumene. In fact, a method has been described in which finely crushed spodumene is mixed with powdered CaCl2, and then the mixture is calcined at high temperature in the solid phase.

[0011] This chlorination-calcination method is disclosed in US 2,561,439 and US 2,627,452.

[0012] US 2,561,439 teaches a vacuum chlorination-calcination method for forming granules of pulverized spodumene together with CaCl2. LiCl is gradually formed, which is then condensed and recovered.

[0013] US 2,627,452 teaches the initial thermal conversion of α-spodumene to β-spodumene, followed by the addition of CaCl2 and a second heat treatment in a rotary kiln, in which LiCl is formed and volatilized.

[0014] This chlorination-roasting method is also applicable to lithium-containing slag obtained from reduction smelting methods used to recover metals from spent lithium batteries. This chlorination-roasting method is illustrated in CN 107964593 A, in which the solidified lithium-containing slag is first pulverized and then mixed with a metal chloride (such as CaCl2). The mixture is then roasted to capture the gradually forming LiCl. However, this multi-step method, involving slag production through smelting, slag solidification, slag pulverization, mixing of the slag with finely powdered CaCl2, roasting of the mixture, and LiCl capture, is both expensive and energy-intensive.

[0015] WO 2020 / 104164 fully utilizes the fact that a liquid phase is obtained during smelting to allow for the combined recovery of valuable metals (such as iron, copper, cobalt, and nickel) in alloy phase form and lithium in flue dust form in a single operation. This method offers significant efficiency advantages because it eliminates the need to separate the slag, mix it with a chloride source, and then heat it for LiCl fuming.

[0016] On the other hand, this method generates a large amount of waste, especially chloride-containing waste in the form of salt discharge, and also increases slag production. This not only generates waste but also negatively impacts the yields of nickel and cobalt. Furthermore, it requires a large amount of reagents. The aim is to solve these problems using the method of this invention. Summary of the Invention

[0017] Therefore, the present invention relates to a method for concentrating lithium in metallurgical fumes, the method comprising the following steps:

[0018] - Provide metallurgical melting furnaces;

[0019] - Preparation of metallurgical furnace charge containing lithium-containing materials, and flux;

[0020] - The metallurgical charge and the flux are smelted in the furnace to obtain a molten pool comprising a slag phase and an optional alloy phase; and,

[0021] - Optionally, the alloy phase and the slag phase can be separated;

[0022] - By adding a first halogen intermediate, most of the lithium is fumed from the molten slag in the form of lithium halide;

[0023] - The lithium halide, which is fumed from the molten slag, will be converted into different lithium compounds and second halogen intermediates;

[0024] - The second halogen intermediate in the fuming step is reused as the first halogen intermediate;

[0025] The halogens are selected from Cl, Br and I.

[0026] The first halogen intermediate and the second halogen intermediate do not need to have the same chemical form, as further outlined below. However, it is crucial that the halides be advantageously reused in the fuming step of the method.

[0027] To address the problems raised above, and to further simplify the method described, it would be beneficial to use a gaseous halogen intermediate.

[0028] Therefore, another solution to the problem is a method for concentrating lithium in metallurgical fumes, the method comprising the following steps:

[0029] - Provide metallurgical melting furnaces;

[0030] - Preparation of metallurgical furnace charge containing lithium-containing materials, and flux;

[0031] - The metallurgical charge and the flux are smelted in the furnace to obtain a molten pool comprising a slag phase and an optional alloy phase; and,

[0032] - Optionally, the alloy phase and the slag phase can be separated;

[0033] - By adding a halogen intermediate, most of the lithium is fumed from the molten slag in the form of lithium halide; wherein the halogen intermediate is a gaseous halogen or a gaseous halogen compound, particularly a compound selected from halogens or hydrogen halides, and more specifically, the halogen intermediate is selected from chlorine, bromine, iodine, hydrogen chloride, hydrogen bromide, hydrogen iodide, and mixtures thereof. The most straightforward choice is chlorine, hydrogen chloride, or mixtures thereof.

[0034] It is evident that a combination of the two solutions described above can also be advantageous, resulting in a method for concentrating lithium in metallurgical fumes, the method comprising the following steps:

[0035] - Provide metallurgical melting furnaces;

[0036] - Preparation of metallurgical furnace charge containing lithium-containing materials, and flux;

[0037] - The metallurgical charge and the flux are smelted in the furnace to obtain a molten pool comprising a slag phase and an optional alloy phase; and,

[0038] - Optionally, the alloy phase and the slag phase can be separated;

[0039] - By adding a halogen intermediate, most of the lithium is fumed from the molten slag in the form of lithium halide; wherein

[0040] - The halogen intermediate includes gaseous halogens or gaseous halogen compounds, especially compounds selected from halogens or hydrogen halides; and

[0041] - The method includes at least one additional step of producing a halogen intermediate from the molten slag by fumigating lithium halide from the molten slag, the molten slag being reacted under conditions sufficient to produce the halogen intermediate and the lithium product, wherein the halogen is selected from Cl, Br and I.

[0042] More specifically, in the method, the gaseous halogen or the gaseous hydrogen halide is selected from chlorine, bromine, iodine, hydrogen chloride, hydrogen bromide, hydrogen iodide, and mixtures thereof, with chlorine, hydrogen chloride, or mixtures thereof being the most straightforward choice.

[0043] The addition of the halogen intermediate (more specifically, chloride) causes LiCl to be fumed, and this can be done during or after the smelting of the metallurgical charge. The slag and the alloy are formed during smelting. The molten slag can also be fumed before or after the separation of the molten slag from the alloy (e.g., by slag tapping).

[0044] In one embodiment, the halogen intermediate may be included as part of the metallurgical furnace charge, for example, as part of the flux fed into the furnace, or added separately to the liquid slag during or after smelting. If the halogen intermediate comprises a gaseous halogen or a gaseous halogen compound, it is advantageous to add the halogen intermediate separately to the liquid slag during or after smelting.

[0045] The halogen intermediate may be an alkali metal halide, an alkaline earth metal halide, a hydrogen halide, a halogen itself, or a combination thereof. More specifically, the halogen intermediate may include calcium chloride and / or magnesium chloride, and more specifically, the halogen intermediate may consist of calcium chloride, magnesium chloride, or a combination thereof.

[0046] In another embodiment, the halogen intermediate may include a gaseous halogen or a hydrogen halide, more specifically, the halogen intermediate may consist of a halogen or a hydrogen halide. Specifically, the halogen intermediate may include chlorine or hydrogen chloride, more specifically, the halogen intermediate may consist of chlorine or hydrogen chloride. The halogen may be combined with hydrogen, especially in the absence of hydrogen halide.

[0047]

[0048] After fumigation, lithium halides are collected, for example, by combining the fumigation with a solvent, such as by passing the fumigation through a solvent or by spraying water into the fumigation, thereby transferring the lithium halides into a solution of a solvent or solvent mixture (especially water as the solvent).

[0049] Other possible devices are common gas purification devices, such as using a scrubber to purify lithium dust.

[0050] The term "majority of lithium" means that at least 50% of the lithium by weight enters the process.

[0051] In this process, the metallurgical furnace charge may contain transition metals. The most concerning transition metals are iron, copper, nickel, and cobalt. Depending on the smelting and fuming conditions, in addition to lithium halides, the flue dust may also contain one or more transition metals. These metals can be removed from lithium halides using steps that are typically accomplished by conventional means, such as maintaining the pH of the solvent in a scrubber, for example. Transition metals can also be removed from lithium halides by lithium crystallization or solvent extraction, or by precipitation or solvent extraction of the transition metals.

[0052] This process is particularly suitable for concentrating lithium present in materials that also contain nickel and / or cobalt. A sufficiently low pO2 is then maintained to reduce at least one of the nickel and cobalt to its metallic state, thereby allowing these elements to enter the alloy phase. pO2 represents the partial pressure of oxygen. "Mostly" means at least 50% by weight of the metal entering the process.

[0053] Technicians know how to alter the redox potential by adjusting the ratio between an oxidizing agent (such as air or O2) and a reducing agent. Typical reducing agents are natural gas or coal, but can also be metallic fractions present in metallurgical furnace charges (such as aluminum, elemental carbon, and plastics). However, hydrogen is the most preferred. Carbon can also be used. The redox potential can be determined by monitoring the yield of metals (such as nickel and cobalt) entering the alloy.

[0054] It is believed that easily oxidized lithium enters the slag in measured quantities. The lithium then reacts with added chlorides to form LiCl, which is released as part of the flue gas.

[0055] Therefore, this process is particularly suitable for processing lithium-containing materials, including lithium batteries, their waste, or their production waste.

[0056] The stoichiometry of chloride is determined based on the following reaction:

[0057]

[0058] These two reactions are for the cases of CaCl2 or MgCl2, respectively.

[0059] Other halides, as well as halogens or hydrogen halides, react similarly with lithium-containing materials.

[0060]

[0061] This can be improved by using reducing agents (such as hydrogen (H2) or carbon (C)):

[0062]

[0063] In another implementation, hydrogen halides (such as HCl) can be used alone or in combination with halogens (such as chlorine). In this case, hydrogen is not required, thus avoiding the difficulties of handling such highly volatile and flammable gases. Using an H2 / Cl2 burner to generate heat and HCl can be a suitable method.

[0064] Since lithium is commonly used in batteries, especially rechargeable batteries, lithium-containing materials include lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel manganese cobalt oxide (NMC), lithium iron phosphate (LFP), and lithium nickel cobalt aluminum oxide (NCA), or other lithium-containing battery materials. At the anode, lithium-graphite intercalation compounds are typical, and lithium metal or lithium titanate (LTO) are also under development. In addition, lithium is used in the electrolyte in the form of LiPF6. Lithium is also used in other products, such as lithium primary batteries, as well as lithium-containing glasses, ceramics, polymers, casting powders, alloys, greases, slags, and pharmaceuticals, which can also be found in lithium-containing materials. As can be seen from the above, lithium-containing materials can also contain, for example, nickel and / or cobalt.

[0065] In one specific implementation, lithium-containing materials include lithium batteries, their waste, or their production waste.

[0066] In one embodiment, the halogen intermediate is added in an amount corresponding to a stoichiometric excess of lithium relative to the flue gas. This stoichiometric excess of the halogen intermediate helps these reactions to be as close as possible to the quantitative yield. Therefore, the amount of halide added should preferably be at least stoichiometric with respect to lithium in the flue gas. More preferably, a stoichiometric excess of greater than 10% is used.

[0067] When very high yields are desired, the amount of halogen intermediate added should preferably be at least stoichiometric with respect to lithium in the slag. More preferably, a stoichiometric excess of greater than 10% is used. This typically ensures a lithium fuming yield greater than 80%, or even greater than 90%.

[0068] Suitable halogen intermediates are, for example, MgCl2, and more preferably CaCl2. These chlorides have high boiling points, 1412°C and 1935°C respectively at atmospheric pressure, which ensures that they react well with lithium oxides in the slag at the operating temperatures of the smelting furnace. Another readily available option is halogens, hydrogen halides, or mixtures thereof, especially chlorine, hydrogen chloride and / or bromine, hydrogen bromide and / or iodine and hydrogen iodide.

[0069] Lithium halides (especially lithium chloride) entering the flue gas can be separated and collected from the flue gas using common unit operations such as scrubbers, bag filters, electrostatic precipitators, and cyclone separators.

[0070] The process described herein includes at least one step in which a halogen intermediate for fumigating lithium halides from molten slag is produced from lithium halides fumigated from molten slag, the molten slag being reacted under conditions sufficient to produce a halogen intermediate and a lithium product.

[0071] The technical advantage of this step, which produces halogen intermediates for fuming lithium halides from molten slag, is that the halogens in lithium halides can be used for fuming in the form of halogen intermediates, thereby reducing salt load, waste, and the need for adding expensive reagents.

[0072] In one embodiment, the steps for generating the halogen intermediate include a water electrolysis step and a conversion reaction.

[0073] The water electrolysis step may include electrolyzing an aqueous solution containing lithium halides under conditions sufficient to obtain lithium hydroxide and halogen intermediates (including hydrogen chloride, chlorine, or mixtures thereof).

[0074] More specifically, water electrolysis is the electrolysis of alkali metal halides to obtain alkali metal hydroxides and halogen intermediates.

[0075] Optionally, alkali metal hydroxides can be converted into alkali metal carbonates by reacting with carbon dioxide.

[0076] The conversion reaction may be (a) the reaction of the lithium halide with an alkali metal hydroxide to produce an alkali metal halide and lithium hydroxide, or (b) the reaction of the lithium halide with an alkali metal carbonate to obtain lithium carbonate and an alkali metal halide.

[0077] In one implementation, the step of generating the halogen intermediate includes molten salt electrolysis.

[0078] Molten salt electrolysis involves electrolyzing a salt melt containing lithium halides under conditions sufficient to obtain lithium metal and halogen intermediates (especially chlorine).

[0079] Since electrolysis typically produces halogen gases, more precisely dihalogen gases such as chlorine (Cl2), these halogen gases can be combined with hydrogen to obtain hydrogen halides, such as hydrogen chloride (HCl) or other hydrogen halides, such as hydrogen bromide (HBr) or hydrogen iodide (HI).

[0080] Both halogens, alone or in combination, and hydrogen halide gases are suitable as halogen intermediates. For example, chlorine or hydrogen chloride, as well as mixtures of chlorine and hydrogen chloride, can be used as halogen intermediates.

[0081] Therefore, as an alternative to using gaseous compounds as halogen intermediates, hydrogen halides can react with alkali metal or alkaline earth metal carbonates, bicarbonates, oxides, or hydroxides to form alkali metal or alkaline earth metal halides suitable as halogen intermediates, such as calcium chloride, magnesium chloride, sodium chloride, potassium chloride, or other halides. Aluminum chloride can also be used as a halogen intermediate.

[0082] Other alkali metal or alkaline earth metal carbonates, oxides, bicarbonates, or hydroxides of barium, strontium, rubidium, and cesium are also suitable, but are generally not economically feasible. Where appropriate, ammonium hydroxide or ammonium carbonate may be used instead of alkali metal hydroxides or carbonates.

[0083] One implementation for converting lithium halides into lithium products and halogen intermediates is a reaction sequence similar to the Solvay process.

[0084] In this sequence, a concentrated solution of lithium halide reacts with ammonia and carbon dioxide. This causes lithium carbonate to precipitate, which is then separated from the resulting ammonium halide solution.

[0085]

[0086] Another option is to first react ammonia and carbon dioxide to produce ammonium carbonate, and then react lithium halide with the resulting ammonium carbonate.

[0087]

[0088] Ammonium halides can be used as halogen intermediates or reacted with calcium oxide to regenerate ammonia, calcium halides, and water to produce calcium halides as halogen intermediates.

[0089]

[0090] In this sequence, carbon dioxide is introduced into the concentrated lithium halide solution along with ammonia. This causes bicarbonate to precipitate out, which is then separated from the resulting ammonium chloride solution. The lithium halide reacts with carbon dioxide, ammonia, and water to form lithium bicarbonate and ammonium chloride (“saltium”).

[0091] Separate steps:

[0092] Carbon dioxide reacts with water to form carbonic acid

[0093]

[0094] Carbonic acid then reacts with ammonia to form ammonium bicarbonate.

[0095]

[0096] Ammonium bicarbonate then reacts with lithium halides to form metastable lithium bicarbonate and ammonium halides. When lithium chloride is used, ammonium chloride will be formed.

[0097]

[0098] Heating lithium bicarbonate to approximately 95°C releases water and carbon dioxide, producing lithium carbonate as a lithium product. This can be achieved through calcination. Lithium carbonate can be obtained directly from the reaction temperature of ammonium bicarbonate with lithium halides.

[0099]

[0100] In another embodiment, lithium halide reacts with ammonium carbonate to directly form lithium carbonate.

[0101]

[0102] Ammonium carbonate can be prepared by reacting carbon dioxide and ammonia in an aqueous solution:

[0103]

[0104] In subsequent steps, the ammonia is recovered, similar to the Solvay process, and is reused to react with carbonic acid to form ammonium bicarbonate, thus allowing it to be reused.

[0105]

[0106] Ammonium chloride can be used as a halogen intermediate or reacted with calcium oxide to form ammonia, calcium chloride and water, producing calcium chloride as a halogen intermediate. Detailed Implementation

[0107] Example 1: Fuming with CaCl2

[0108] End-of-life batteries with a composition conforming to Table 1 are shredded for easier handling and metering.

[0109] A molten pool was then prepared in a 2 L alumina crucible, in which 400 g of starting slag was heated and melted in an induction furnace at 1500°C. This starting slag was a product of the previous operation and was used to provide the liquid pool for adding batteries. The composition of the slag is given in Table 2.

[0110] Once the slag has melted, the battery can be added along with limestone and sand flux. The addition is carried out gradually over a 2-hour period. During this time, O2 is blown over the pool at a rate of 160 liters / hour to burn off the metallic Al and carbon present in the battery.

[0111] After the final addition of battery waste, CO was blown through the cell at a rate of 60 liters / hour for 30 minutes to obtain a homogeneous cell and determine the final reduction level. Samples of the alloy and slag were collected. The mass balance of slag and alloy is shown in Table 2. Yields were calculated based solely on the alloy and slag phases, thus discarding (minor) losses or carryover into the gas phase.

[0112] Table 1: Composition of Storage Batteries

[0113]

[0114] Table 2: Detailed material balance of smelting operations prior to chloride addition

[0115]

[0116]

[0117]

[0118] While the temperature remained at 1500°C, argon gas was blown into the liquid pool at a rate of 60 liters per hour to ensure the slag was mixed. This experiment clearly demonstrates that without the addition of chlorides, Li remains in the slag.

[0119] Each experiment began with the lithium-containing slag as shown in Table 2 above, and four different experiments were conducted, differing only in the total amount of CaCl2 added. These four amounts represent 0%, 60%, 100%, and 120% of the chloride required for a stoichiometric reaction with the Li present in the slag, respectively. CaCl2 was added gradually in 12 increments over the initial few hours, each 5 minutes apart. Prior to testing, the CaCl2 was dried at 150°C to remove excess moisture. After the final CaCl2 addition, the slag was allowed to react for another 30 minutes while argon gas continued to be purged.

[0120] Slag samples were collected before the addition of CaCl2, after the last addition, and 30 minutes after the last addition. The results are shown in Table 3, which also shows the total yield of Li entering the flue dust.

[0121] With a substoichiometric addition of 60%, all CaCl2 reacts with Li in the slag to form volatile LiCl. However, 100% stoichiometry of CaCl2 is insufficient for quantitative lithium vaporization. A superstoichiometric addition of 120% (equivalent to a 20% excess) achieves a 96% lithium yield.

[0122] The flue dust samples all showed a lithium concentration of 15%, which is equivalent to a LiCl content of more than 90%. The remainder was mainly CaCl2 due to mechanical carryover.

[0123] Table 3: Changes in Li content in slag over time and stoichiometry (CaCl2)

[0124]

[0125] Similar to the four experiments with CaCl2, two experiments were conducted using MgCl2. The results are shown in Table 4. The lithium yield was significantly lower, but still satisfactory, especially when using 200% stoichiometry.

[0126] Table 4: Changes in Li content in slag over time and stoichiometry (MgCl2)

[0127]

[0128] NaCl was also tested as a chlorinating agent, yielding a 26% yield when using 100% stoichiometry. Superstoichiometric addition of 250% NaCl yielded satisfactory yields of 50% or higher, as shown in Table 5.

[0129] Table 5: Changes in Li content in slag over time and stoichiometry (NaCl)

[0130]

[0131] By converting the Cl2 and H2 gases generated during electrolysis into HCl, and then reacting the HCl with CaO, MgO, and NaOH respectively, halogen intermediates such as CaCl2, MgCl2, and NaCl can be obtained.

[0132] Example 2: Fuming with Cl2

[0133] A new experiment was conducted starting with the lithium-containing slag from Table 2 above, in which 1 kg of slag was maintained at 1450°C while Cl2 gas was blown into the liquid slag through an Al2O3 tube submerged from the top. The Cl2 gas was generated during the electrolysis process. The gas was continuously blown for 120 minutes, so that after 120 minutes, 1.6 times the stoichiometric amount of Cl was added compared to the Li in the slag.

[0134] Slag samples were collected before the addition of Cl2 and at different times during the experiment. The results are shown in Table 6, which also shows the total yield of Li entering the flue dust.

[0135] Table 6: Changes in Li content in slag over time and stoichiometry (Cl2)

[0136]

[0137] The flue dust samples all showed a lithium concentration of 15%, which is equivalent to a LiCl content of more than 90%.

[0138] Example 3: Fumigation with HCl

[0139] End-of-life batteries with a composition conforming to Table 7 are shredded for easier handling and metering.

[0140] A molten pool was then prepared in a 2 L alumina crucible, in which 400 g of starting slag was heated and melted in an induction furnace at 1500°C. This starting slag was a product of the previous operation and was used to provide the liquid pool for adding batteries. The composition of the slag is given in Table 8.

[0141] Once the slag has melted, the battery can be added along with limestone and sand flux. The addition is carried out gradually over a 2-hour period. During this time, O2 is blown over the pool at a rate of 220 liters / hour to burn off the metallic Al and carbon present in the battery.

[0142] After the final addition of battery waste, CO was blown through the cell at a rate of 60 liters / hour for 30 minutes to obtain a homogeneous cell and determine the final reduction level. Samples of the alloy and slag were collected. The mass balance of slag and alloy is shown in Table 8. Yields were calculated based solely on the alloy and slag phases, thus discarding (minor) losses or carryover into the gas phase.

[0143] Table 7: Composition of Storage Batteries

[0144]

[0145] Table 8: Detailed material balance of smelting operations prior to chloride addition

[0146]

[0147]

[0148]

[0149] While the temperature remained at 1500°C, argon gas was blown into the liquid pool at a rate of 60 liters per hour to ensure the slag was mixed. This experiment clearly demonstrates that without the addition of chlorides, Li remains in the slag.

[0150] A new experiment was conducted starting with the lithium-containing slag from Table 8 above, in which 1 kg of slag was maintained at 1450°C while HCl gas was blown into the liquid slag through an Al₂O₃ tube submerged from the top. HCl gas was obtained by reacting Cl₂ gas and H₂ gas from the electrolysis process. The gas was continuously blown for 120 minutes, so that after 120 minutes, 1.6 times the stoichiometric amount of Cl was added compared to the Li in the slag.

[0151] Slag samples were collected before the addition of HCl and at different times during the experiment. The results are shown in Table 9, which also shows the total yield of Li entering the flue dust.

[0152] Table 9: Changes in Li content (HCl) in slag over time and stoichiometry

[0153]

[0154] Example 4: Electrolysis of LiCl solution

[0155] The electrolysis apparatus includes a membrane electrolyzer with an effective membrane area of ​​100 cm². A stainless steel mesh cathode and an IrO₂-MMO anode are used.

[0156] The Nafion cation exchange membrane is placed between the anode and cathode chambers. Two bottles are connected to the anode and cathode chambers respectively, and a peristaltic pump is used to continuously circulate the electrolytes (anolyte and catholyte) within the chambers at a flow rate of 200 mL / min. The anode electrolyte consists of 1 L of 5 M LiCl solution. The catholyte consists of 300 mL of 0.1 M LiOH solution.

[0157] A small amount of LiOH was initially added to the cathode electrolyte to ensure minimum electrolyte conductivity. The electrolyzer was then connected to a power source, and a current of 2.5 A was applied, equivalent to 250 A / m. 2 The current density.

[0158] The electrolysis process was carried out at room temperature (21°C) for 28 hours. Table 10 lists the volumes of anolyte and catholyte, as well as the amount and concentration of Li, before and after the experiment.

[0159] During the experiment, Li was transferred from the anolyte chamber to the catholyte chamber and converted into LiOH. In addition to Li, some water was also transferred from the anolyte to the catholyte, which explains the decrease in the volume of the anolyte and the increase in the volume of the catholyte.

[0160] The cathode electrolyte LiOH concentration reached 4.6 M, equivalent to a current efficiency of 72% for Li. During the experiment, gas analysis confirmed the formation of Cl₂ and H₂ gases, which were repeatedly used in the fuming reaction.

[0161] Table 10 – LiCl Electrolysis Experiment (250 A / m) 2 (21°C, 28 hours)

[0162]

Claims

1. A method for concentrating lithium in metallurgical fumes, the method comprising the following steps: - Provide metallurgical melting furnaces; - Preparation of metallurgical furnace charge containing lithium-containing materials, and flux; - The metallurgical charge and the flux are smelted in the furnace to obtain a molten pool containing a slag phase and an optional alloy phase; as well as, - Optionally, the alloy phase and the slag phase can be separated; - By adding a first halogen intermediate, most of the lithium is fumed from the molten slag in the form of lithium halide; - The lithium halide, which is fumed from the molten slag, will be converted into different lithium compounds and second halogen intermediates; - In the fuming step, the second halogen intermediate is reused as the first halogen intermediate; The halogens are selected from Cl, Br and I.

2. The method of claim 1, wherein the first halogen intermediate is added to the method as part of the metallurgical charge or as part of the flux, or is added to the liquid slag during or after smelting.

3. The method according to claim 1 or 2, wherein the first halogen intermediate is added in an amount corresponding to a stoichiometric excess of lithium relative to the flue dust.

4. The method according to claim 3, wherein the stoichiometric excess of the first halogen intermediate is at least 10%.

5. The method according to any one of claims 1 to 4, wherein the first halogen intermediate is chlorine (Cl2), hydrogen chloride (HCl), alkali metal chloride, alkaline earth metal chloride, or a combination thereof, and more specifically, the first halogen intermediate may include CaCl2, AlCl3, MgCl2, or a combination thereof.

6. The method according to any one of claims 1 to 5, wherein the lithium-containing material further comprises nickel and / or cobalt, and wherein a sufficiently low pO2 is maintained to reduce a large portion of at least one of the nickel and cobalt to the alloy phase.

7. The method according to any one of claims 1 to 6, wherein hydrogen, carbon, or a combination thereof are added.

8. The method according to any one of claims 1 to 7, wherein the step of generating the second halogen intermediate comprises a water electrolysis step and a conversion reaction.

9. The method according to claim 8, wherein the conversion reaction is (a) the reaction of the lithium halide with an alkali metal hydroxide to obtain an alkali metal halide and lithium hydroxide, or (b) the reaction of the lithium halide with an alkali metal carbonate to obtain lithium carbonate and an alkali metal halide.

10. The method according to any one of claims 8 to 9, wherein the water electrolysis is the electrolysis of an alkali metal halide to obtain an alkali metal hydroxide and the second halogen intermediate.

11. The method of claim 8, wherein the water electrolysis step comprises electrolyzing an aqueous solution containing the lithium halide under conditions sufficient to obtain lithium hydroxide and the second halogen intermediate, wherein the second halogen intermediate comprises hydrogen chloride, chlorine, or a mixture thereof.

12. The method according to any one of claims 1 to 7, wherein the step of generating the second halogen intermediate comprises a molten salt electrolysis step.

13. The method of claim 12, wherein the molten salt electrolysis comprises electrolyzing a salt melt containing the lithium halide under conditions sufficient to obtain lithium metal and the second halogen intermediate, in particular chlorine.

14. The method according to any one of the preceding claims, wherein the first halogen intermediate used in the fuming step is chlorine (Cl2), hydrogen chloride (HCl), or a combination thereof, optionally in the presence of hydrogen; and The step of generating the second halogen intermediate includes: - The lithium halide is converted using an alkali metal carbonate to obtain lithium carbonate and an alkali metal halide, and in - Under conditions sufficient to obtain an alkali metal hydroxide and the second halogen intermediate, particularly chlorine, the alkali metal halide is subjected to an electrolytic step; and in optional subsequent steps, - The alkali metal hydroxide is reacted with carbon dioxide under conditions sufficient to yield an alkali metal carbonate.

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