Process for the recovery of valuable metals

Abstract

The application provides a valuable metal recovery method, which comprises the following steps: a roasting process, wherein battery recyclates are roasted with a lithium extraction agent under the protection of an inert gas to obtain a roasting product; a first leaching and separation process, wherein the roasting product is subjected to the first leaching and separation to obtain a lithium-containing leaching solution and a leaching residue; a calcining process, wherein the leaching residue and a slagging agent are mixed and calcined to obtain a calcined product; and a matte-making smelting process, wherein the calcined product, ice nickel, oxygen pressure residue and a matte-making agent are mixed and subjected to the matte-making smelting to obtain a nickel-containing matte. The valuable metal recovery method provided in the embodiments of the application has the advantages of simple process flow, high recovery rate, less pollutants and low valuable metal recovery cost, and is environment-friendly.

Description

Technical Field

[0001] This application relates to the field of valuable metal recycling technology, and more particularly to a method for recycling valuable metals. Background Technology

[0002] Valuable metals generally refer to metals that have recycling value among the raw materials for refining metals, such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li). These valuable metals can be used as materials for battery manufacturing, giving batteries characteristics such as high energy density and high cycle performance, and are therefore widely used in electric vehicles, electronic devices, aerospace and other fields.

[0003] Currently, valuable metals in batteries can be recovered from nickel intermediates (such as nickel matte) or from the batteries themselves. However, in related technologies, the process of recovering valuable metals is complex, has a low recovery rate, and easily generates a large amount of pollutants, resulting in high recycling costs and being environmentally unfriendly. Summary of the Invention

[0004] This application provides a method for recycling valuable metals, which has a simple process flow, high recovery rate, and is environmentally friendly.

[0005] This application provides a method for recycling valuable metals, the method comprising:

[0006] The roasting process involves roasting the battery recyclables and lithium extraction agent under a protective atmosphere to obtain the roasted product.

[0007] The first leaching and separation process involves leaching and separating the roasted product to obtain a lithium-containing leachate and leaching residue.

[0008] In the calcination process, the leaching residue and slag-forming agent are mixed and then calcined to obtain the calcined product.

[0009] The matte smelting process involves mixing calcined products, nickel matte, oxygen pressure slag, and matte-making agents, and then smelting the mixture to obtain nickel-containing matte.

[0010] The recycling method provided in this application, through a roasting process and a first leaching separation process, can enrich a large amount of valuable lithium metal in the battery recyclables in the leachate, thereby improving the lithium recovery rate. The leaching residue obtained from the first leaching separation process undergoes a calcination process to form slag, pre-removing some impurities, such as Ca and Mg, which are then incorporated into the slag-forming agent. This helps to shorten the matte smelting time. The calcined product, nickel matte, oxygen pressure slag, and matte-forming agent obtained through the calcination process are mixed and then smelted to form matte. This process separates valuable metals such as nickel from other impurities in the calcined product, nickel matte, and oxygen pressure slag. In other words, valuable metals such as nickel enter the sulfur phase to obtain matte containing nickel and other valuable metals. This allows for the simultaneous recovery of valuable metals such as nickel from the calcined product, nickel matte, and oxygen pressure slag, simplifying the process of recovering valuable metals from battery recyclables, nickel matte, and oxygen pressure slag, and increasing the recovery rate of valuable metals such as nickel. Furthermore, the large amount of oxygen contained in nickel matte, oxygen pressure slag, and calcined product reduces the amount of oxygen required from external sources during the sulfur formation process. This further reduces the cost of valuable metal recovery while also mitigating the safety risks associated with introducing large amounts of external oxygen and the requirements for fire protection and recovery equipment in the plant. Furthermore, impurities such as iron and manganese in the calcination products, nickel matte, and oxygen-pressed slag will enter the slag phase. This slag phase can be directly used as a byproduct in fields such as construction, thus reducing the amount of impurity removal in subsequent production lines. This helps to reduce the demand for impurity removal equipment and the floor space required for recycling plants, thereby further reducing the cost of recovering valuable metals from battery recyclables, nickel matte, and oxygen-pressed slag. In addition, the above-mentioned processes generate few pollutants, making the method for recovering valuable metals environmentally friendly. Therefore, the recycling method provided in this application embodiment has a simple process flow, high recovery rate, and generates few pollutants, resulting in low cost of recovering valuable metals and environmental friendliness.

[0011] In some embodiments of this application, the lithium extraction agent in the roasting process includes one or more of a reducing agent, sulfate, or concentrated sulfuric acid.

[0012] In some embodiments of this application, the reducing agent includes one or more of activated carbon, hydrogen, lignite, anthracite, and carbon monoxide.

[0013] In some embodiments of this application, the sulfate includes one or more of ammonium sulfate and sodium sulfite.

[0014] In some embodiments of this application, the mass ratio of battery recyclables to lithium extraction agent is 20:(1-30).

[0015] In some embodiments of this application, the calcination temperature is 300℃-1000℃, the heating rate is 2℃ / min-10℃ / min, and the calcination time is 0.5h-5h.

[0016] In some embodiments of this application, the first leaching separation step includes:

[0017] In the first leaching step, the roasted product and the first leaching agent are mixed and subjected to a first leaching treatment to dissolve the lithium in the roasted product into the solution to obtain a lithium-containing first leaching slurry.

[0018] In the first separation process, the first leaching slurry is subjected to solid-liquid separation treatment to obtain lithium-containing leaching solution and leaching residue.

[0019] In some embodiments of this application, in the first leaching step, the pH of the first leaching treatment is between 3 and 7.

[0020] In some embodiments of this application, in the first leaching process, the temperature of the first leaching treatment is between 30°C and 90°C, and the time of the first leaching treatment is between 0.5h and 4h.

[0021] In some embodiments of this application, the mass ratio of leaching residue to slag-forming agent in the calcination process is (2-20):1.

[0022] In some embodiments of this application, the calcination temperature is 600-1000℃ and the calcination time is 2h-8h.

[0023] In some embodiments of this application, the slag-forming agent includes one or more of silica, diatomaceous earth, bentonite, calcium oxide, and alumina.

[0024] In some embodiments of this application, in the matte smelting process, the mass ratio of calcined product, nickel matte, oxygen pressure slag, and matte-making agent is 10:(1-30):(1-25):(0.01-30).

[0025] In some embodiments of this application, the matte smelting temperature is 1000℃-1500℃, and the matte smelting time is 1h-10h.

[0026] In some embodiments of this application, the matte-forming agent includes sulfur-containing elements and / or sulfur-containing compounds.

[0027] In some embodiments of this application, after the first leaching separation step, a drying step is further included to dry the leaching residue, nickel matte, and oxygen pressure residue respectively.

[0028] In some embodiments of this application, the drying temperature is 100℃-300℃, the drying time is 0.5h-4h, and air and / or oxygen are introduced during the drying process.

[0029] In some embodiments of this application, the method for recycling valuable metals further includes:

[0030] In the first pulping process, matte is mixed with a solvent and then subjected to a first pulping treatment to obtain a first pulping solution;

[0031] In the second leaching and separation process, the first slurry and the second leaching agent are mixed and then subjected to a second leaching treatment to dissolve the nickel in the first slurry into the solution to obtain a nickel-containing second leaching slurry. The second leaching slurry is then subjected to solid-liquid separation treatment to obtain a second filtrate and a second filter residue.

[0032] In the extraction process, the second filtrate and the extractant are mixed and then extracted to obtain the extract and the raffinate.

[0033] In some embodiments of this application, in the first pulping process, matte is ground, and the ground matte is mixed with solvent at a solid-liquid ratio of 1g:(2-15)mL to undergo the first pulping process to obtain the first pulping liquid.

[0034] In some embodiments of this application, the particle size of the ground matte is less than or equal to 48µm.

[0035] In some embodiments of this application, the temperature of the first pulping treatment is 30°C-90°C, and the time of the first pulping treatment is 0.5h-5h.

[0036] In some embodiments of this application, in the second leaching separation step, the second leaching agent includes concentrated sulfuric acid, wherein the amount of concentrated sulfuric acid added is 1 to 1.6 times the theoretical amount required to leach all the nickel from the first slurry.

[0037] In some embodiments of this application, the temperature of the second leaching treatment is 50°C-100°C, and the time of the second leaching treatment is 2h-8h.

[0038] In some embodiments of this application, the method for recycling valuable metals further includes:

[0039] In the third leaching and separation process, the second filter residue and the third leaching agent are mixed and then subjected to a third leaching treatment to obtain a third leaching slurry. The third leaching slurry is then subjected to solid-liquid separation treatment to obtain a third filtrate and a third filter residue.

[0040] In the second pulping process, the third filter residue and solvent are mixed and then subjected to a second pulping treatment to obtain the second pulping liquid.

[0041] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching to obtain the fourth leaching slurry. The fourth leaching slurry is then subjected to solid-liquid separation to obtain the fourth filtrate and the fourth filter residue.

[0042] In some embodiments of this application, in the third leaching separation step, the third leaching agent includes concentrated sulfuric acid, wherein the amount of concentrated sulfuric acid added is 1 to 1.3 times the theoretical amount required to leach all the nickel from the second filter residue.

[0043] In some embodiments of this application, in the third leaching separation process, the temperature of the third leaching treatment is 40℃-100℃, and the time of the third leaching treatment is 0.5h-4h.

[0044] In some embodiments of this application, in the second pulping process, the third filter residue and solvent are mixed at a solid-liquid ratio of 1g:(3-15)mL.

[0045] In some embodiments of this application, in the fourth leaching separation process, the oxygen partial pressure of oxygen pressure leaching is 0.6 MPa-1.2 MPa.

[0046] In some embodiments of this application, in the fourth leaching separation process, the oxygen pressure leaching temperature is 150℃-220℃ and the oxygen pressure leaching time is 2h-8h. Attached Figure Description

[0047] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 A flowchart illustrating a method for recycling valuable metals provided in some embodiments of this application;

[0049] Figure 2 A flowchart illustrating a method for recycling valuable metals provided in some embodiments of this application;

[0050] Figure 3 A flowchart illustrating a method for recycling valuable metals provided in some embodiments of this application;

[0051] Figure 4 A flowchart illustrating a method for recycling valuable metals provided in some embodiments of this application;

[0052] Figure 5 A flowchart illustrating a method for recycling valuable metals provided in some embodiments of this application. Detailed Implementation

[0053] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0055] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0056] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0057] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0058] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0059] In this application, battery recyclables refer to a mixture containing major battery components such as the positive electrode, recovered from a battery. The battery can be a nickel-sulfur secondary battery, a nickel-metal hydride secondary battery, a lithium-ion secondary battery, etc. In some examples, the positive electrode of a lithium-ion secondary battery includes a positive electrode current collector and a positive electrode active material. The positive electrode current collector can be a metal foil such as aluminum, copper, or nickel, and the positive electrode active material can include valuable metals such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li). In some specific examples, battery recyclables can be a mixture containing valuable metals such as Ni, Co, Mn, and Li, as well as carbon powder, obtained through processes such as dismantling, crushing, screening, pyrolysis, and sorting.

[0060] Lithium extraction agents are compounds that can convert lithium metal in battery recycling into compounds that are easily soluble in water or weakly acidic solutions.

[0061] Nickel matte refers to a mixture containing metal sulfides such as nickel, for example, Ni3S2. In some cases, nickel matte can be an intermediate product in the nickel smelting process, such as low-grade nickel matte and high-grade nickel matte. Low-grade nickel matte typically contains less than 40% nickel, while high-grade nickel matte typically contains more than 60% nickel.

[0062] Oxygen-pressed slag refers to slag containing elements such as nickel, iron, and oxygen. In some examples, oxygen-pressed slag can be slag produced through an oxygen-pressing process, with its main component being iron oxide and a total nickel and cobalt content of approximately 2%-15%. The oxygen-pressing process typically utilizes oxygen or air (oxygen in the air) as an oxidant, which is thoroughly mixed with the slurry under stirring to undergo an oxidation reaction with low-valence minerals such as reduced sulfide minerals, leaching the target metal into the solution and achieving efficient extraction of the target metal from the ore.

[0063] Please see Figure 1 As shown, this application provides a method for recycling valuable metals, the method comprising:

[0064] S100, calcination process: The battery recyclables and lithium extraction agent are calcined under a protective atmosphere to obtain the calcined product.

[0065] S200, First leaching separation process, the roasted product is subjected to first leaching separation to obtain lithium-containing leachate and leaching residue.

[0066] S400, calcination process: The leaching residue and slag-forming agent are mixed and then calcined to obtain the calcined product;

[0067] S500, the matte smelting process, involves mixing the calcined product, nickel matte, oxygen pressure slag, and matte-making agent, and then smelting the mixture to obtain nickel-containing matte.

[0068] The recycling method provided in this application, through a roasting process and a first leaching separation process, can enrich a large amount of valuable lithium metal in the battery recyclables in the leachate, thereby improving the lithium recovery rate. The leaching residue obtained from the first leaching separation process undergoes a calcination process to form slag, pre-removing some impurities, such as Ca and Mg, which are then incorporated into the slag-forming agent. This helps to shorten the matte smelting time. The calcined product, nickel matte, oxygen pressure slag, and matte-forming agent obtained through the calcination process are mixed and then smelted to form matte. This process separates the valuable nickel metal from other impurities in the calcined product, nickel matte, and oxygen pressure slag, allowing the valuable nickel metal to enter the sulfur phase and form nickel-containing matte. This allows for the simultaneous recovery of valuable metals such as nickel from the calcined product, nickel matte, and oxygen pressure slag, simplifying the process of recovering valuable metals from battery recyclables, nickel matte, and oxygen pressure slag, and increasing the recovery rate of valuable nickel metal. Furthermore, the large amount of oxygen contained in nickel matte, oxygen pressure slag, and calcined product reduces the amount of oxygen required from external sources during the sulfur formation process. This further reduces the cost of valuable metal recovery while also mitigating the safety risks associated with introducing large amounts of external oxygen and the requirements for fire protection and recovery equipment in the plant. Furthermore, impurities such as iron and manganese in the calcination products, nickel matte, and oxygen-pressed slag will enter the slag phase. This slag phase can be directly used as a byproduct in fields such as construction, thus reducing the amount of impurity removal in subsequent production lines. This helps to reduce the demand for impurity removal equipment and the floor space required for recycling plants, thereby further reducing the cost of recovering valuable metals from battery recyclables, nickel matte, and oxygen-pressed slag. In addition, the above-mentioned processes generate few pollutants, making the method for recovering valuable metals environmentally friendly. Therefore, the recycling method provided in this application embodiment has a simple process flow, high recovery rate, and generates few pollutants, resulting in low cost of recovering valuable metals and environmental friendliness.

[0069] In embodiments of this application, the lithium extraction agent used in the roasting process can convert lithium metal in battery recyclables into compounds that are easily soluble in water or weakly acidic solutions. In some embodiments, the lithium extraction agent may include one or more of a reducing agent, sulfate, or concentrated sulfuric acid. The reducing agent primarily undergoes a reduction reaction during roasting to form carbonate or bicarbonate ions. These carbonate and bicarbonate ions can then react with lithium ions in the battery recyclables to form soluble lithium carbonate or lithium bicarbonate, thereby facilitating lithium leaching and recovery. Exemplarily, the reducing agent may include one or more of activated carbon, hydrogen, lignite, anthracite, and carbon monoxide. The activated carbon may include coconut shell powdered activated carbon and / or wood-based activated carbon. These reducing agents offer high cost-effectiveness, helping to reduce lithium extraction costs while also facilitating the conversion of lithium ions in battery recyclables into soluble lithium carbonate or lithium bicarbonate, thus improving lithium recovery rates.

[0070] Concentrated sulfuric acid and sulfates primarily react with lithium ions in battery recyclables during the roasting process to form soluble lithium sulfate, facilitating lithium leaching and recovery. For example, sulfates may include one or more of ammonium sulfate and sodium sulfite.

[0071] In this embodiment, a suitable mass ratio of lithium extraction agent to battery recyclables can also help improve the lithium recovery rate. In some embodiments, the mass ratio of battery recyclables to lithium extraction agent is 20:(1-30). When the mass ratio of lithium extraction agent to battery recyclables is within the aforementioned suitable range, both the utilization rate of the lithium extraction agent and the lithium recovery rate can be increased.

[0072] In other embodiments, the mass ratio of battery recyclables to lithium extraction agent may also be 20:(3-28), 20:(5-24), 20:(8-21), etc.

[0073] Furthermore, in the S100 calcination process, calcination parameters within a suitable range can also facilitate the thermodynamic reaction of lithium ions forming soluble salts. In some embodiments of this application, the calcination temperature is 300℃-1000℃, the heating rate is 2℃ / min-10℃ / min, and the calcination time is 0.5h-5h.

[0074] Furthermore, calcination is carried out under a protective atmosphere, which facilitates the oxidation of carbon in the battery recyclables, thereby helping to form soluble lithium carbonate or lithium bicarbonate with lithium ions, thus improving the lithium recovery rate. In this embodiment, the gas used for the protective atmosphere can be any protective gas well known in the art, such as an inert gas or nitrogen, wherein the inert gas can include helium (He), neon (Ne), argon (Ar), etc.

[0075] Please see Figure 2As shown, in some embodiments, the first leaching separation step of S200 includes:

[0076] S210, First leaching step: Mix the roasted product with a first leaching agent and perform a first leaching treatment to dissolve the lithium in the roasted product into the solution to form a first leaching slurry;

[0077] S220, First separation process, solid-liquid separation treatment is performed on the first leaching slurry to obtain lithium-containing leaching solution and leaching residue.

[0078] In the above embodiments, the first leaching step S210 uses a solvent to mix and slurry the roasted product, which provides a good leaching environment. The addition of the first leaching agent causes the lithium in the roasted product to dissolve into the solution to form the first leaching slurry. Then, in the first separation step S220, the first leaching slurry is subjected to solid-liquid separation treatment to obtain a lithium-containing leaching solution and leaching residue.

[0079] In some embodiments, the solvent used in the first leaching step of S210 can be water, an acidic washing solution generated during the recovery of valuable metals, or a mixed solvent formed by water and acidic washing solution. The use of acidic washing solution as a solvent facilitates the reuse of waste liquid and achieves a pre-leaching effect, thereby reducing the amount of the first leaching agent required.

[0080] In some embodiments, in the first leaching step of S210, the liquid-to-solid ratio of the solvent to the calcined product is (1-10) mL:1g. When the liquid-to-solid ratio of the solvent to the calcined product is within the above range, it can facilitate the leaching of lithium while also ensuring that the solvent content in the leaching residue obtained from subsequent separation is within a reasonable range, thereby facilitating the subsequent reaction of the leaching residue.

[0081] In this embodiment, the liquid-to-solid ratio typically refers to the ratio of the volume of the solvent to the mass of the calcined product.

[0082] In some embodiments, in the first leaching step of S210, the pH of the first leaching treatment is between 3 and 7. When the pH of the first leaching treatment is within the above range, lithium can easily exist in an ionic state in the aqueous solution, thereby reducing the cost of lithium recovery and thus helping to reduce the cost of recovering valuable metals.

[0083] In the above embodiments, the addition of the first leaching agent can make the pH of the first leaching treatment in the range of 3-7, and the first leaching agent can be any compound that can make the pH of the first leaching treatment in the above range, such as concentrated sulfuric acid.

[0084] Furthermore, in the first leaching step of S210, the temperature of the first leaching treatment is between 30°C and 90°C, and the time of the first leaching treatment is between 0.5 h and 4 h. A temperature within the above range is conducive to the occurrence of leaching reaction kinetics. A time within the above range helps to improve the leaching reaction efficiency.

[0085] In the first separation process of S220, the solid-liquid separation process can be any method well known in the art for separating solids and liquids, such as centrifugation, tilting, filtration, etc.

[0086] Furthermore, the leaching residue obtained from the above solid-liquid separation process is mixed with a slagging agent and then calcined to induce a slagging reaction. This allows some impurities (such as Ca and Mg) in the leaching residue to enter the slagging agent, thus pre-removing some impurities from the leaching residue. Leaching residue with reduced impurity content requires less time for matte smelting, thereby improving the efficiency of matte smelting. In addition, the calcination process can also remove some carbon from the leaching residue, reducing its impact on subsequent sulfur formation reactions.

[0087] In some embodiments, during the calcination process of S400, the mass ratio of leaching residue to slag-forming agent is (2-20):1. When the mass ratio of leaching residue to slag-forming agent is within the above range, it can help improve the efficiency of the slag-forming reaction to increase the nickel recovery rate, while also further reducing the cost of recovering valuable metals.

[0088] In some embodiments, the slagging agent includes one or more of silica, diatomaceous earth, bentonite, calcium oxide, and alumina. It is understood that the slagging agent can be any one of silica, diatomaceous earth, bentonite, calcium oxide, and alumina, or a mixture of any two of silica, diatomaceous earth, bentonite, calcium oxide, and alumina. When the slagging agent includes a mixture, the components in the mixture synergistically promote the entry of impurities in the leaching residue into the slag phase, thereby reducing impurities in the sulfur phase and improving the recovery rate of valuable metals.

[0089] In some specific embodiments, the calcination process can react magnesium and some iron in the leaching residue with a slagging agent to form a slagging agent, allowing them to enter the slag phase. The following slagging reactions may occur:

[0090] 10Fe2O3 + FeS = 7Fe3O4 + SO2;

[0091] 3Fe3O4 + FeS + 5SiO2 = 5(2FeO ·SiO2) + SO2;

[0092] FeO + SiO2 = 2FeO·SiO2;

[0093] CaO + SiO2 = CaO·SiO2;

[0094] MgO + SiO2 = MgO·SiO2;

[0095] 2Mn3O4 + S = 6MnO + SO2;

[0096] MnO + SiO2 = MnO·SiO2.

[0097] In this embodiment, the matte smelting process of S500 mixes calcined products, nickel matte, oxygen-pressed slag, and a sulfur-forming agent before smelting. This allows impurities in the calcined products, nickel matte, and oxygen-pressed slag to enter the slag phase, and also allows nickel in these products to enter the sulfur phase. This simultaneously achieves the recovery of valuable nickel from battery recyclables, nickel matte, and oxygen-pressed slag, resulting in a high valuable metal recovery rate. Furthermore, the oxygen element contained in the oxygen-pressed slag reduces the amount of oxygen introduced during the matte smelting process. This fully utilizes the oxygen-pressed slag to further reduce the cost of valuable metal recovery while also mitigating the safety risks associated with introducing large amounts of external oxygen, as well as the requirements for fire protection and recovery equipment in the plant.

[0098] In some embodiments, the matte-forming agent comprises elemental sulfur and / or sulfur-containing compounds. The appropriate combination of elemental sulfur and sulfur-containing compounds with calcined products, nickel matte, and oxygen-pressed slag, through matte-forming smelting, can enrich valuable nickel in the sulfur phase within the calcined products, nickel matte, and oxygen-pressed slag, thereby contributing to improved recovery rates of valuable metals from these materials.

[0099] In these embodiments, the sulfur-containing compound can be one or more of sulfur or sulfide minerals.

[0100] In some embodiments, during the matte-making smelting process of S400, the mass ratio of calcined product, nickel matte, oxygen-pressed slag, and matte-making agent is 10:(1-30):(1-25):(0.01-30). When the mass ratio of calcined product, nickel matte, oxygen-pressed slag, and matte-making agent is within the above range, it can help the valuable metal nickel in the calcined product, nickel matte, and oxygen-pressed slag enter the sulfur phase to form nickel-containing matte, thereby further improving the recovery rate of valuable metals.

[0101] In some embodiments, the matte melting temperature is between 1000℃ and 1500℃, and the melting time is between 1 hour and 10 hours. When the matte melting temperature and time are within the above ranges, it not only facilitates the thermodynamic chemical reaction but also improves the efficiency of the reaction. The reactions that may occur during matte melting are as follows:

[0102] Decomposition reactions of high-valent sulfides:

[0103] Fe7S8 = 7FeS + 1 / 2S2;

[0104] 2CuFeS2 = Cu2S + 2FeS + 1 / 2S2;

[0105] (Ni, Fe)9S8 = (x / 3)Ni3S2+ (9-x)FeS + (x / 6-1 / 2)S2;

[0106] FeS2 = FeS + 1 / 2S2;

[0107] Oxidation reactions of low-valent sulfides:

[0108] 2FeS + 3O2 = 2FeO + 2SO2;

[0109] Ni3S2 + 7 / 2O2 = 3NiO + 2SO2;

[0110] 3FeS + 3NiO = Ni3S2 + 3FeO + 1 / 2S2;

[0111] 3NiS = Ni3S2+ S;

[0112] Co3S2 + 7 / 2O2 = 3CoO + 2SO2;

[0113] 3FeS + 3CoO = Co3S2 + 3FeO + 1 / 2S2;

[0114] 3CoS = Co3S2 + S;

[0115] The main chemical reactions occurring in battery recycling are as follows:

[0116] NiO + S = NiS + 1 / 2O2;

[0117] CoO + S = CoS + 1 / 2 O2;

[0118] Ni + S = NiS;

[0119] Co + S = CoS;

[0120] MnO + SiO2 = MnO·SiO2.

[0121] Through the above reaction, valuable nickel in the calcined products, matte, and oxygen-pressed slag can enter the sulfur phase to form matte, while manganese enters the slag phase, which can further remove impurities in the nickel phase, thereby further improving the recovery rate of valuable nickel.

[0122] In the above embodiments, the battery can be a ternary battery, that is, the battery contains valuable metals such as Ni, Co, and Mn. The above recycling method can recycle and reuse valuable metals such as Ni and Co.

[0123] Please see Figure 3 As shown, in some embodiments, after the first leaching separation step in S200, the method for recovering valuable metals further includes:

[0124] S300, the drying process, is used to dry the leaching residue, nickel matte and oxygen pressure slag respectively.

[0125] In the above embodiments, the drying process of drying the leaching residue, nickel matte, and oxygen pressure slag can remove some of the moisture from the leaching residue, nickel matte, and oxygen pressure slag.

[0126] In some embodiments, the drying temperature is 100°C-300°C, and the drying time is 0.5h-4h. The drying parameters of the above drying process can further reduce the water content in the leaching residue, nickel matte, and oxygen pressure slag, and reduce the adverse effects of water on the chemical reactions in the subsequent matte smelting process, such as the formation of water vapor carrying away some of the sulfiding agent.

[0127] In the above embodiments, introducing air and / or oxygen during the drying process can help accelerate the drying of leaching residue, nickel matte, and oxygen pressure residue.

[0128] Please see Figure 4 As shown, after the matte smelting process, the nickel-containing matte obtained can be sold directly as a commodity, or it can be further processed to separate nickel from other metallic elements and prepare raw materials for battery production. Therefore, this application also provides a method for further processing nickel-containing matte, including:

[0129] S600, First pulping process: After mixing matte with solvent, the first pulping treatment is carried out to obtain the first pulping liquid.

[0130] S700, Second leaching separation process: The first slurry and the second leaching agent are mixed and then subjected to a second leaching treatment to dissolve the nickel in the first slurry into the solution to obtain a second leaching slurry containing nickel. The second leaching slurry is subjected to solid-liquid separation treatment to obtain a second filtrate and a second filter residue.

[0131] S800: The second filtrate and the extractant are mixed and then extracted to obtain the extract and the raffinate.

[0132] In the above embodiments, the first slurrying step can uniformly disperse matte in a solvent to form a first slurry, so as to facilitate the rapid completion of the leaching reaction in the subsequent second leaching separation step. The second leaching separation step can leach nickel and, after solid-liquid separation treatment, separate the second filtrate containing nickel from the second filter residue containing other impurities. Then, the second filtrate is mixed with an extractant and subjected to extraction treatment, extracting some impurities into the extract, while nickel is enriched in the raffinate, thereby achieving the separation of nickel from other metallic impurities.

[0133] In some embodiments, water can be used as the solvent in the first pulping step of S600, which can help reduce the cost of recycling valuable metals.

[0134] In some embodiments, matte is ground, and the ground matte is mixed with solvent at a solid-liquid ratio of 1 g:(2-15) mL for a first slurry treatment to obtain a first slurry. Grinding the matte reduces its particle size, facilitating its uniform dispersion in the solvent. Furthermore, grinding provides the matte particles with a larger reaction surface area, thus aiding in subsequent matte leaching reactions. Moreover, mixing the ground matte with solvent at the aforementioned solid-liquid ratio further enhances the dispersion of the matte, facilitating nickel leaching.

[0135] In this embodiment, the solid-liquid ratio typically refers to the ratio of the mass of the ground matte to the volume of the solvent.

[0136] In some embodiments, the particle size of the ground matte is less than or equal to 48 µm. This allows the matte to have a suitable particle size, which can further improve its dispersion effect. Moreover, the particle size of the ground matte is within the above-mentioned range, which allows it to have a suitable reaction area, which is beneficial to nickel leaching.

[0137] In the above embodiments, the ground matte can be screened through a sieve with an appropriate mesh size to ensure that the particle size of the ground matte meets the requirements, while large particles that do not pass through the sieve can be further ground to achieve the corresponding required particle size. For example, a sieve with a mesh size greater than or equal to 300 is used to screen out matte with a particle size less than or equal to 48µm.

[0138] In some embodiments, the temperature of the first pulping treatment is 30°C-90°C, and the time of the first pulping treatment is 0.5h-5h. When the temperature and time of the first pulping treatment are within the above range, it is beneficial to the thermal motion of molecules and helps to uniformly disperse the ground matte in the solvent, which can help to shorten the time of the subsequent leaching reaction.

[0139] In some embodiments, in the second leaching separation step of S700, the second leaching agent may include concentrated sulfuric acid, the amount of which is 1 to 1.6 times the theoretical amount required to leach all the nickel from the first slurry. By rationally combining the leaching agents, the nickel leaching rate can be improved while reducing leaching costs.

[0140] In some embodiments, the temperature of the second leaching treatment is between 50°C and 100°C, and the duration of the second leaching treatment is between 2 hours and 8 hours. When the temperature and time of the second leaching treatment are within the above ranges, it is beneficial to the thermal motion of molecules and helps to improve the leaching efficiency.

[0141] In addition, in some embodiments, the extractant in the extraction process of S800 may include one or more of di(2-ethylhexyl) phosphate (P204), 2-ethylhexyl phosphoric acid (P507), and di(2,4,4-trimethylpentyl)phosphonic acid (C272). The specific type of extractant can be selected according to the impurities in the solution.

[0142] In the above embodiments, after the second filtrate is extracted, the resulting raffinate contains nickel sulfate. The extract can also be used to extract impurities from the extractant through a back-extraction solution (a mixed sulfate system formed by impurities such as Fe, Zn, Ca, Mg, and Cd). After separation, the extractant can be recovered, thereby further reducing the cost of recovering valuable metals.

[0143] Furthermore, the second filter residue produced in the second leaching separation process of S700 can be further processed to recover some of the valuable nickel contained in the filter residue and to form byproducts such as oxygen pressure slag. Please refer to [link to relevant documentation]. Figure 5 As shown, in some embodiments, the method for recycling valuable metals further includes:

[0144] S900, the third leaching separation process, the second filter residue and the third leaching agent are mixed and then subjected to the third leaching treatment to obtain the third leaching slurry. The third leaching slurry is then subjected to solid-liquid separation treatment to obtain the third filtrate and the third filter residue.

[0145] S1000, Second pulping process: The third filter residue and solvent are mixed and then subjected to a second pulping treatment to obtain the second pulping liquid;

[0146] S2000, the fourth leaching separation process, introduces oxygen into the second slurry for oxygen pressure leaching treatment to obtain the fourth leaching slurry, and performs solid-liquid separation treatment on the fourth leaching slurry to obtain the fourth filtrate and the fourth filter residue.

[0147] In the above embodiments, nickel in the second filter residue can be further recovered to further improve the recovery rate of valuable metals.

[0148] In some embodiments, in the third leaching separation step of S900, the third leaching agent includes concentrated sulfuric acid, and the amount added is 1 to 1.3 times the theoretical amount required to leach all the nickel in the second filter residue. By properly combining the leaching agents, the nickel leaching rate can be improved while reducing leaching costs.

[0149] In some embodiments, the temperature of the third leaching treatment is 40°C-100°C, and the time of the third leaching treatment is 0.5h-4h.

[0150] In some embodiments, in the second slurrying step of S1000, the solvent can be water, and the third filter residue and solvent are subjected to a second slurrying treatment at a solid-liquid ratio of 1g:(3-15)ml. This facilitates the dispersion of the filter residue, promotes subsequent leaching reactions, and reduces the disruption of the water system balance in the system.

[0151] In some embodiments, in the second pulping step of S1000, the temperature of the second pulping treatment is 30°C-90°C, and the time of the second pulping treatment is 0.5h-5h. When the temperature and time of the second pulping treatment are within the above range, it is beneficial to the thermal motion of molecules and helps the filter residue to be uniformly dispersed in the third solvent, which helps to shorten the time of the subsequent leaching reaction.

[0152] In some embodiments, the oxygen partial pressure in oxygen pressure leaching is 0.6 MPa to 1.2 MPa. When the oxygen partial pressure in oxygen pressure leaching is within the above range, it can facilitate the oxygen pressure leaching reaction while reducing the safety risks associated with oxygen.

[0153] In some embodiments, the oxygen pressure leaching temperature is 150°C-220°C, and the oxygen pressure leaching time is 2h-8h. This can help remove alloy phases from the material and reduce the safety risks arising from the reaction of alloys with concentrated sulfuric acid during the oxygen pressure reaction.

[0154] In some specific embodiments, the method for recycling valuable metals may include:

[0155] In the roasting process, the battery recyclables and lithium extraction agent are mixed evenly and then roasted under a protective gas to obtain the roasted product.

[0156] In the first leaching step, the roasted product and the first leaching agent are mixed and subjected to a first leaching treatment to dissolve the lithium in the roasted product into the solution to form a first leaching slurry.

[0157] In the first separation process, the first leaching slurry is subjected to solid-liquid separation treatment to obtain lithium-containing leaching solution and leaching residue. The lithium-containing leaching solution can be used as a lithium source for producing positive electrode active materials in lithium-ion secondary batteries.

[0158] In the drying process, the leaching residue, nickel matte, and oxygen pressure residue are dried separately.

[0159] The calcination process involves mixing the leaching residue and the slagging agent and then calcining them to obtain the calcined product.

[0160] The matte smelting process involves mixing calcined products, nickel matte, oxygen pressure slag, and matte-forming agent, and then smelting the mixture to obtain nickel-containing matte, which can be used as a material for producing ternary precursors.

[0161] In the first pulping process, matte is mixed with a solvent and then subjected to a first pulping treatment to obtain a first pulping liquid.

[0162] In the second leaching and separation process, the first slurry and the second leaching agent are mixed and then subjected to a second leaching treatment to dissolve the nickel in the first slurry into the solution to obtain a second leaching slurry containing nickel. The second leaching slurry is then subjected to solid-liquid separation treatment to obtain a second filtrate and a second filter residue.

[0163] In the extraction process, the second filtrate and the extractant are mixed and then extracted to obtain an extract and a raffinate containing nickel. The raffinate can be used as a ternary precursor material.

[0164] In the third leaching and separation process, the second filter residue and the third leaching agent are mixed and subjected to a third leaching treatment to obtain a third leaching slurry. The third leaching slurry is then subjected to solid-liquid separation treatment to obtain a third filtrate and a third filter residue. The third filtrate can be recycled, for example, it can be added back to the leaching and separation process.

[0165] In the second pulping process, the third filter residue and solvent are mixed and then subjected to a second pulping treatment to obtain the second pulping liquid.

[0166] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching to obtain a fourth leaching slurry. The fourth leaching slurry is then subjected to solid-liquid separation to obtain a fourth filtrate containing nickel and a fourth filter residue. The fourth filtrate can be used as a ternary precursor material, while the fourth filter residue can be directly applied to building materials.

[0167] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents and raw materials used in the embodiments are commercially available or synthesized by conventional methods, as are the instruments used in the embodiments.

[0168] Example 1

[0169] This embodiment provides a method for recycling valuable metals, including the following steps:

[0170] In the roasting process, 200g of battery recycled material (the mass fraction of each component in the battery recycled material is shown in Table 1) and 10g of coconut shell powdered activated carbon were mixed evenly and placed into a crucible. The mixture was roasted at 400℃ for 0.5h under inert gas protection to obtain the roasted product. The heating rate was 2℃ / min.

[0171] In the first leaching and separation process, the roasted product was added to pure water at a liquid-to-solid ratio of 5 ml: 1 g. Concentrated sulfuric acid was added to adjust the initial solution pH to 4 ± 0.1. The mixture was stirred at 40°C for 2 hours. During the process, the pH was monitored in real time and acid was added in a timely manner to ensure that the pH of the system was maintained at 4 ± 0.1 for the first leaching treatment. After leaching, the lithium-containing leachate and leaching residue were obtained by filtration. The leaching rate of Li in the leachate was 96.18%, the leaching rate of Ni was 4.98%, the leaching rate of Co was 0.44%, and the leaching rate of Mn was 0.5%.

[0172] In the drying process, the leaching residue, low-grade nickel matte, and oxygen pressure slag are dried separately. Air is introduced during the drying process, the drying temperature is 100℃, the drying time is 4 hours, and the moisture content of the dried material is 0.5%.

[0173] In the calcination process, the dried leaching residue is mixed with a slagging agent at a mass ratio of 8:1 and then calcined. The slagging agent consists of silica and bentonite. The calcination temperature is 850℃ and the calcination time is 6 hours.

[0174] In the matte smelting process, calcined products, nickel matte, oxygen pressure slag, and sulfur are mixed in a mass ratio of 10:20:2:10 and then smelted. The smelting temperature is 1450℃ and the smelting time is 1.5h, resulting in matte containing nickel and cobalt. The composition of low-grade nickel matte and oxygen pressure slag is shown in Table 1. The calculated Ni recovery rate is 99.23% and the Co recovery rate is 99.85%.

[0175] The method for recycling valuable metals provided in this embodiment also includes:

[0176] In the first pulping process, the obtained matte is ball-milled and then sieved through a 300-mesh sieve. The sieved matte is then mixed with water at a solid-liquid ratio of 1g:9mL for the first pulping process to obtain the first pulping liquid. The temperature of the first pulping process is 30℃ and the time of the first pulping process is 2h.

[0177] In the second leaching and separation process, concentrated sulfuric acid is added to the first slurry for a second leaching treatment. The amount of sulfuric acid added is 1.1 times the theoretical amount. The temperature of the second leaching treatment is 70°C, and the time of the second leaching treatment is 4 hours. After the second leaching treatment, the mixture is filtered to obtain the second filtrate and the second filter residue.

[0178] In the extraction process, the second filtrate and P507 extractant are mixed and extracted to obtain an extract and a raffinate, wherein the raffinate is a solution of nickel sulfate and cobalt sulfate.

[0179] In the third leaching and separation process, concentrated sulfuric acid is added to the second filter residue for a third leaching treatment. The amount of sulfuric acid added is 1.1 times the theoretical amount. The temperature of the third leaching treatment is 80℃, and the time of the third leaching treatment is 2 hours. After the third leaching treatment, the residue is filtered to obtain the third filtrate and the third filter residue. The third filtrate contains nickel sulfate and cobalt sulfate.

[0180] In the second pulping process, the third filter residue and water are subjected to a second pulping treatment at a solid-liquid ratio of 1g:10mL to obtain the second pulping liquid.

[0181] The fourth leaching and separation process involves introducing oxygen into the second slurry for oxygen pressure leaching. The leaching temperature is 185℃, the oxygen partial pressure is 0.8 MPa, and the leaching time is 6 hours. After leaching, the solution is filtered. The resulting fourth filtrate contains nickel sulfate and cobalt sulfate, while the fourth filter residue contains metals such as calcium (Ca). This filtrate can be sold directly as a byproduct of building materials production.

[0182] See Table 1 for the composition of each raw material in the embodiments of this application.

[0183] Table 1. Components of battery recyclables, low-nickel matte, and oxygen-pressed slag in the examples.

[0184]

[0185] It should be noted that the battery recyclables, low-grade nickel matte, and oxygen-pressed slag used in the embodiments of this application are merely exemplary and should not be construed as limiting the ideas of this application, namely, the recycling of valuable metals such as lithium, nickel, and cobalt from battery recyclables, low-grade nickel matte, and oxygen-pressed slag.

[0186] Example 2

[0187] This embodiment is similar to Embodiment 1 in that it uses battery recycled materials, low-grade nickel matte, and oxygen-pressed slag. The difference lies in other process parameters, specifically including the following steps:

[0188] In the roasting process, 200g of battery recycled material and 30g of wood-based activated carbon are mixed evenly and placed into a crucible. The mixture is then roasted at 800℃ for 2 hours under inert gas protection to obtain the roasted product. The heating rate is 10℃ / min.

[0189] In the first leaching and separation process, the roasted product was added to pure water at a liquid-to-solid ratio of 2 ml: 1 g. Concentrated sulfuric acid was added to adjust the initial solution pH to 6.5 ± 0.1. The mixture was stirred at 60°C for 2 hours. During the process, the pH was monitored in real time and acid was added in a timely manner to ensure that the pH of the system was maintained at 6.5 ± 0.1 for the first leaching treatment. After leaching, the lithium-containing leachate and leaching residue were obtained by filtration. The leaching rate of Li in the leachate was 97.36%, the leaching rate of Ni was 3.49%, the leaching rate of Co was 0.72%, and the leaching rate of Mn was 0.81%.

[0190] In the drying process, the leaching residue, low-grade nickel matte, and oxygen pressure slag are dried separately. Air is introduced during the drying process, the drying temperature is 150℃, the drying time is 2 hours, and the moisture content of the dried material is 0.25%.

[0191] In the calcination process, the dried leaching residue is mixed with a slagging agent at a mass ratio of 10:1 and then calcined. The slagging agent consists of silicon dioxide, bentonite, and calcium oxide. The calcination temperature is 800℃ and the calcination time is 2 hours.

[0192] In the matte smelting process, the calcined product, low-grade nickel matte, oxygen pressure slag, and liquid sulfur are mixed in a mass ratio of 2:3:2:4 and then smelted. The smelting temperature is 1300℃ and the smelting time is 2 hours, resulting in matte containing nickel and cobalt. The calculated Ni recovery rate is 99.12% and the Co recovery rate is 99.29%.

[0193] The method for recycling valuable metals provided in this embodiment also includes:

[0194] In the first pulping process, the obtained matte is ball-milled and then sieved through a 300-mesh sieve. The sieved matte is then mixed with water at a solid-liquid ratio of 1g:6mL for the first pulping process to obtain the first pulping liquid. The temperature of the first pulping process is 60℃ and the time of the first pulping process is 1.5h.

[0195] In the second leaching and separation process, concentrated sulfuric acid is added to the first slurry for a second leaching treatment. The amount of sulfuric acid added is 1.2 times the theoretical amount. The temperature of the second leaching treatment is 70°C, and the time of the second leaching treatment is 6 hours. After the second leaching treatment, the mixture is filtered to obtain the second filtrate and the second filter residue.

[0196] In the extraction process, the second filtrate and P507 extractant are mixed and extracted to obtain an extract and a raffinate, wherein the raffinate is a solution of nickel sulfate and cobalt sulfate.

[0197] In the third leaching and separation process, concentrated sulfuric acid is added to the second filter residue for a third leaching treatment. The amount of sulfuric acid added is 1.2 times the theoretical amount. The temperature of the third leaching treatment is 60℃, and the time of the third leaching treatment is h. After the third leaching treatment, the residue is filtered to obtain the third filtrate and the third filter residue. The third filtrate contains nickel sulfate and cobalt sulfate.

[0198] In the second pulping process, the third filter residue and water are subjected to a second pulping treatment at a solid-liquid ratio of 1g:8mL to obtain the second pulping liquid.

[0199] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching. The oxygen pressure leaching temperature is 185℃, the oxygen partial pressure is 0.85MPa, and the oxygen pressure leaching time is 4h. After the oxygen pressure leaching is completed, pressure filtration is performed to obtain a fourth filtrate containing nickel sulfate and cobalt sulfate, and a fourth filter residue containing metals such as Ca.

[0200] Example 3

[0201] This embodiment is similar to Embodiment 1 in that it uses battery recycled materials, low-grade nickel matte, and oxygen-pressed slag. The difference lies in other process parameters, specifically including the following steps:

[0202] In the roasting process, 200g of battery recycled material, 180g of ammonium sulfate and concentrated sulfuric acid were mixed evenly and placed into a crucible. The mixture was roasted at 750℃ for 2 hours under inert gas protection to obtain the roasted product. The heating rate was 5℃ / min.

[0203] In the first leaching and separation process, the roasted product was added to pure water at a liquid-to-solid ratio of 2 ml:1 g. Concentrated sulfuric acid was added to adjust the initial solution pH to 6.5±0.1. The mixture was stirred at 60°C for 2 hours. During the process, the pH was monitored in real time and acid was added in a timely manner to ensure that the pH of the system was maintained at 6.5±0.1 for the first leaching treatment. After leaching, the lithium-containing leachate and leaching residue were obtained by filtration. The leaching rate of Li in the leachate was 99.28%, the leaching rate of Ni was 3.86%, the leaching rate of Co was 1.2%, and the leaching rate of Mn was 0.36%.

[0204] In the drying process, the leaching residue, low-grade nickel matte, and oxygen pressure slag are dried separately. Air is introduced during the drying process, the drying temperature is 200℃, the drying time is 1.5h, and the moisture content of the dried material is 0.15%.

[0205] In the calcination process, the dried leaching residue is mixed with a slagging agent at a mass ratio of 12:1 and then calcined. The slagging agent is a mixture of silicon dioxide and calcium oxide. The calcination temperature is 900℃ and the calcination time is 3 hours.

[0206] In the matte smelting process, the calcined product, low-grade nickel matte, oxygen pressure slag, and liquid sulfur are mixed in a mass ratio of 10:2:2:5 and then smelted. The smelting temperature is 1250℃ and the smelting time is 2 hours, resulting in matte containing nickel and cobalt. The calculated Ni recovery rate is 99.14% and the Co recovery rate is 98.99%.

[0207] The method for recycling valuable metals provided in this embodiment also includes:

[0208] In the first pulping process, the obtained matte is ball-milled and then sieved through a 300-mesh sieve. The sieved matte is then mixed with water at a solid-liquid ratio of 1g:7mL for the first pulping process to obtain the first pulping liquid. The temperature of the first pulping process is 70℃ and the time of the first pulping process is 2h.

[0209] In the second leaching and separation process, concentrated sulfuric acid is added to the first slurry for a second leaching treatment. The amount of sulfuric acid added is 1.15 times the theoretical amount. The temperature of the second leaching treatment is 60°C, and the time of the second leaching treatment is 5 hours. After the second leaching treatment, the mixture is filtered to obtain the second filtrate and the second filter residue.

[0210] In the extraction process, the second filtrate and P507 extractant are mixed and extracted to obtain an extract and a raffinate, wherein the raffinate is a solution of nickel sulfate and cobalt sulfate.

[0211] In the third leaching and separation process, concentrated sulfuric acid is added to the second filter residue for a third leaching treatment. The amount of sulfuric acid added is 1.3 times the theoretical amount. The temperature of the third leaching treatment is 60℃, and the time of the third leaching treatment is h. After the third leaching treatment, the residue is filtered to obtain the third filtrate and the third filter residue. The third filtrate contains nickel sulfate and cobalt sulfate.

[0212] In the second pulping process, the third filter residue and water are subjected to a second pulping treatment at a solid-liquid ratio of 1g:12mL to obtain the second pulping liquid.

[0213] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching treatment. The oxygen pressure leaching temperature is 185℃, the oxygen partial pressure is 1MPa, and the oxygen pressure leaching time is 3h. After the oxygen pressure leaching is completed, pressure filtration is performed to obtain a fourth filtrate containing nickel sulfate and cobalt sulfate, and a fourth filter residue containing metals such as Ca.

[0214] Example 4

[0215] This embodiment is similar to Embodiment 1 in that it uses battery recycled materials, low-grade nickel matte, and oxygen-pressed slag. The difference lies in other process parameters, specifically including the following steps:

[0216] In the roasting process, 200g of battery recycled material and 300g of concentrated sulfuric acid were mixed evenly and placed into a crucible. The mixture was roasted at 1000℃ for 5 hours under inert gas protection to obtain the roasted product. The heating rate was 8℃ / min.

[0217] In the first leaching and separation process, the roasted product was added to pure water at a liquid-to-solid ratio of 10 ml: 1 g. Concentrated sulfuric acid was added to adjust the initial solution pH to 7±0.1. The mixture was stirred at 90°C for 4 hours. During the process, the pH was monitored in real time and acid was added in a timely manner to ensure that the pH of the system was maintained at 7±0.1 for the first leaching treatment. After leaching, the lithium-containing leachate and leaching residue were obtained by filtration. The leaching rate of Li in the leachate was 99.89%, the leaching rate of Ni was 4.50%, the leaching rate of Co was 2.1%, and the leaching rate of Mn was 1.34%.

[0218] In the drying process, the leaching residue, low-grade nickel matte, and oxygen pressure slag are dried separately. Oxygen is introduced during the drying process, the drying temperature is 300℃, the drying time is 0.5h, and the moisture content of the dried material is 0.05%.

[0219] In the calcination process, the dried leaching residue is mixed with a slagging agent at a mass ratio of 20:1 and then calcined. The slagging agent is a mixture of silicon dioxide, calcium oxide, and aluminum oxide. The calcination temperature is 1000℃ and the calcination time is 8 hours.

[0220] In the matte smelting process, the calcined product, low-grade nickel matte, oxygen pressure slag, and sulfide ore are mixed in a mass ratio of 10:10:7:6 and then smelted. The smelting temperature is 1500℃ and the smelting time is 5 hours, resulting in matte containing nickel and cobalt. The calculated Ni recovery rate is 98.22% and the Co recovery rate is 98.89%.

[0221] The method for recycling valuable metals provided in this embodiment also includes:

[0222] In the first pulping process, the obtained matte is ball-milled and then sieved through a 300-mesh sieve. The sieved matte is then mixed with water at a solid-liquid ratio of 1g:15mL for the first pulping process to obtain the first pulping liquid. The temperature of the first pulping process is 90℃ and the time of the first pulping process is 5h.

[0223] In the second leaching and separation process, concentrated sulfuric acid is added to the first slurry for a second leaching treatment. The amount of sulfuric acid added is 1.6 times the theoretical amount. The temperature of the second leaching treatment is 100℃ and the time is 4 hours. After the second leaching treatment, the mixture is filtered to obtain the second filtrate and the second filter residue.

[0224] In the extraction process, the second filtrate and P507 extractant are mixed and extracted to obtain an extract and a raffinate, wherein the raffinate is a solution of nickel sulfate and cobalt sulfate.

[0225] In the third leaching and separation process, concentrated sulfuric acid is added to the second filter residue for a third leaching treatment. The amount of sulfuric acid added is 1.3 times the theoretical amount. The temperature of the third leaching treatment is 100℃, and the time of the third leaching treatment is h. After the third leaching treatment, the residue is filtered to obtain the third filtrate and the third filter residue. The third filtrate contains nickel sulfate and cobalt sulfate.

[0226] In the second pulping process, the third filter residue and water are subjected to a second pulping treatment at a solid-liquid ratio of 1g:15mL to obtain the second pulping liquid.

[0227] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching treatment. The oxygen pressure leaching temperature is 220℃, the oxygen partial pressure is 1MPa, and the oxygen pressure leaching time is 8h. After the oxygen pressure leaching is completed, pressure filtration is performed to obtain a fourth filtrate containing nickel sulfate and cobalt sulfate, and a fourth filter residue containing metals such as Ca.

[0228] Example 5

[0229] This embodiment is similar to Embodiment 1 in that it uses battery recycled materials, low-grade nickel matte, and oxygen-pressed slag. The difference lies in other process parameters, specifically including the following steps:

[0230] In the roasting process, 200g of battery recycled material and 200g of concentrated sulfuric acid were mixed evenly and placed into a crucible. The mixture was roasted at 750℃ for 2 hours under inert gas protection to obtain the roasted product. The heating rate was 7℃ / min.

[0231] In the first leaching and separation process, the roasted product was added to pure water at a liquid-to-solid ratio of 5 ml: 1 g. Concentrated sulfuric acid was added to adjust the initial solution pH to 6.5 ± 0.1. The mixture was stirred at 80°C for 2 hours. During the process, the pH was monitored in real time and acid was added in a timely manner to ensure that the pH of the system was maintained at 6.5 ± 0.1 for the first leaching treatment. After leaching, the lithium-containing leachate and leaching residue were obtained by filtration. The leaching rate of Li in the leachate was 99.78%, the leaching rate of Ni was 2.50%, the leaching rate of Co was 1.69%, and the leaching rate of Mn was 0.65%.

[0232] In the drying process, the leaching residue, low-grade nickel matte, and oxygen pressure slag are dried separately. Compressed air is introduced during the drying process, the drying temperature is 200℃, the drying time is 2 hours, and the moisture content of the dried material is 0.1%.

[0233] In the calcination process, the dried leaching residue is mixed with a slagging agent at a mass ratio of 5:1 and then calcined. The slagging agent is a mixture of silicon dioxide, calcium oxide, and bentonite. The calcination temperature is 750℃ and the calcination time is 3 hours.

[0234] In the matte smelting process, the calcined product, low-grade nickel matte, oxygen pressure slag, and sulfide ore are mixed in a mass ratio of 10:20:20:25 and then smelted. The matte smelting temperature is 1250℃ and the smelting time is 3 hours, resulting in matte containing nickel and cobalt. The calculated Ni recovery rate is 99.85% and the Co recovery rate is 99.56%.

[0235] The method for recycling valuable metals provided in this embodiment also includes:

[0236] In the first pulping process, the obtained matte is ball-milled and then sieved through a 300-mesh sieve. The sieved matte is then mixed with water at a solid-liquid ratio of 1g:5mL for the first pulping process to obtain the first pulping liquid. The temperature of the first pulping process is 90℃ and the time of the first pulping process is 2h.

[0237] In the second leaching and separation process, concentrated sulfuric acid is added to the first slurry for a second leaching treatment. The amount of sulfuric acid added is 1.2 times the theoretical amount. The temperature of the second leaching treatment is 80℃, and the time of the second leaching treatment is 8 hours. After the second leaching treatment, the mixture is filtered to obtain the second filtrate and the second filter residue.

[0238] In the extraction process, the second filtrate and P507 extractant are mixed and extracted to obtain an extract and a raffinate, wherein the raffinate is a solution of nickel sulfate and cobalt sulfate.

[0239] In the third leaching and separation process, concentrated sulfuric acid is added to the second filter residue for a third leaching treatment. The amount of sulfuric acid added is 1.2 times the theoretical amount. The temperature of the third leaching treatment is 80℃, and the time of the third leaching treatment is h. After the third leaching treatment, the residue is filtered to obtain the third filtrate and the third filter residue. The third filtrate contains nickel sulfate and cobalt sulfate.

[0240] In the second pulping process, the third filter residue and water are subjected to a second pulping treatment at a solid-liquid ratio of 1g:5mL to obtain the second pulping liquid.

[0241] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching treatment. The oxygen pressure leaching temperature is 200℃, the oxygen partial pressure is 0.9MPa, and the oxygen pressure leaching time is 8h. After the oxygen pressure leaching is completed, pressure filtration is performed to obtain a fourth filtrate containing nickel sulfate and cobalt sulfate, and a fourth filter residue containing metals such as Ca.

[0242] Example 6

[0243] This embodiment is similar to Embodiment 1 in that it uses battery recycled materials, low-grade nickel matte, and oxygen-pressed slag. The difference lies in other process parameters, specifically including the following steps:

[0244] In the roasting process, 200g of battery recycled material and 300g of concentrated sulfuric acid were mixed evenly and placed into a crucible. The mixture was roasted at 600℃ for 2 hours under inert gas protection to obtain the roasted product. The heating rate was 6℃ / min.

[0245] In the first leaching and separation process, the roasted product was added to pure water at a liquid-to-solid ratio of 5 ml: 1 g. Concentrated sulfuric acid was added to adjust the initial solution pH to 5 ± 0.1. The mixture was stirred at 80°C for 1 hour. During the process, the pH was monitored in real time and acid was added in a timely manner to ensure that the pH of the system was maintained at 5 ± 0.1 for the first leaching treatment. After leaching, the lithium-containing leachate and leaching residue were obtained by filtration. The leaching rate of Li in the leachate was 99.18%, the leaching rate of Ni was 3.50%, the leaching rate of Co was 3.25%, and the leaching rate of Mn was 4.78%.

[0246] In the drying process, the leaching residue, low-grade nickel matte, and oxygen pressure slag are dried separately. Oxygen is introduced during the drying process, the drying temperature is 150℃, the drying time is 3 hours, and the moisture content of the dried material is 0.13%.

[0247] In the calcination process, the dried leaching residue is mixed with a slagging agent at a mass ratio of 7:1 and then calcined. The slagging agent is a mixture of silicon dioxide, aluminum oxide, calcium oxide, and bentonite. The calcination temperature is 750℃ and the calcination time is 3 hours.

[0248] In the matte smelting process, the calcined product, low-grade nickel matte, oxygen pressure slag, and liquid sulfur are mixed in a mass ratio of 10:30:25:30 and then smelted. The smelting temperature is 1250℃ and the smelting time is 8 hours, resulting in matte containing nickel and cobalt. The calculated Ni recovery rate is 98.23% and the Co recovery rate is 98.65%.

[0249] The method for recycling valuable metals provided in this embodiment also includes:

[0250] In the first pulping process, the obtained matte is ball-milled and then sieved through a 300-mesh sieve. The sieved matte is then mixed with water at a solid-liquid ratio of 1g:10mL for the first pulping process to obtain the first pulping liquid. The temperature of the first pulping process is 60℃ and the time of the first pulping process is 2h.

[0251] In the second leaching and separation process, concentrated sulfuric acid is added to the first slurry for a second leaching treatment. The amount of sulfuric acid added is 1.2 times the theoretical amount. The temperature of the second leaching treatment is 80℃, and the time of the second leaching treatment is 2 hours. After the second leaching treatment, the mixture is filtered to obtain the second filtrate and the second filter residue.

[0252] In the extraction process, the second filtrate and P507 extractant are mixed and extracted to obtain an extract and a raffinate, wherein the raffinate is a solution of nickel sulfate and cobalt sulfate.

[0253] In the third leaching and separation process, concentrated sulfuric acid is added to the second filter residue for a third leaching treatment. The amount of sulfuric acid added is 1.2 times the theoretical amount. The temperature of the third leaching treatment is 80℃, and the time of the third leaching treatment is h. After the third leaching treatment, the residue is filtered to obtain the third filtrate and the third filter residue. The third filtrate contains nickel sulfate and cobalt sulfate.

[0254] In the second pulping process, the third filter residue and water are subjected to a second pulping treatment at a solid-liquid ratio of 1g:7mL to obtain the second pulping liquid.

[0255] In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching. The oxygen pressure leaching temperature is 200℃, the oxygen partial pressure is 1.2MPa, and the oxygen pressure leaching time is 8h. After the oxygen pressure leaching is completed, pressure filtration is performed to obtain a fourth filtrate containing nickel sulfate and cobalt sulfate, and a fourth filter residue containing metals such as Ca.

[0256] Comparative Example 1

[0257] Based on Example 1, oxygen was additionally introduced only during the matte smelting process, with an oxygen flow rate of 50 Nm³. 3 / h, nickel yield is 98.02%, and Co yield is 98.67%.

[0258] Comparative Example 2

[0259] Based on Example 1, only the matte smelting process was changed. No oxygen pressure slag was added during this process, and the nickel yield was 97.28% and the Co yield was 97.99%.

[0260] Comparative Example 3

[0261] Based on Example 1, only the matte smelting process was changed. In this process, oxygen pressure slag was not added and additional oxygen was introduced at a flow rate of 50 Nm. 3 / h, nickel yield is 98.12%, and Co yield is 98.93%.

[0262] Test section

[0263] (1) Leaching rate test of valuable metals

[0264] Take 5 mL of the leachate and dilute it with 45 mL of concentrated sulfuric acid to obtain the test sample solution;

[0265] Take 10 mL of sample solution and place it in an inductively coupled plasma optical emission spectrometer (ICP) for testing. The concentration of each valuable metal in the sample solution is obtained from the test. Based on this concentration, the concentration of valuable metals in the leachate is calculated. Then, the leaching rate of the valuable metals (e.g., Li, Ni, Co, Mn, etc.) is calculated using the following formula:

[0266] Leaching rate = (Leaching volume * Concentration of valuable metals in leachate) / (Mass of battery recycled material * Mass content of valuable metals in battery recycled material).

[0267] (2) Recovery rate test of valuable metals

[0268] Valuable metals in sulfur phase substances are leached with strong acid to obtain leachate;

[0269] Take 5 mL of the leachate and dilute it with 45 mL of concentrated sulfuric acid to obtain the test sample solution;

[0270] Take 10 mL of sample solution and place it in an ICP test. The concentration of each valuable metal in the sample solution is obtained from the test. The total amount of valuable metals in the leachate is calculated based on the concentration. Then, the recovery rate of valuable metals (e.g., Ni, Co) is calculated using the following formula:

[0271] The mass fraction of Ni / Co in matte = (Ni / Co concentration in matte leachate * leachate volume) / mass of matte (Note: The matte leachate is obtained by completely dissolving the matte in concentrated sulfuric acid.)

[0272] Ni / Co recovery rate = (mass of matte material * mass fraction of Ni / Co in matte) / ((mass content of Ni / Co in low-grade nickel matte * mass of low-grade nickel matte) + (mass content of Ni / Co in oxygen-pressed slag * mass of oxygen-pressed slag) + (mass content of Ni / Co in lithium-extracted battery recyclables * mass of lithium-extracted battery recyclables)).

[0273] Table 2. Recovery rates of valuable metals in each example and comparative example.

[0274]

[0275] Referring to Table 2, it can be seen from Examples 1-6 that, using the recycling method provided in this application, the lithium recovery rate in battery recyclables can reach over 92%, which is significantly higher than the traditional wet lithium extraction rate of only about 85%. At the same time, the recovery rates of nickel and cobalt are also over 92%, which can achieve the purpose of recovering valuable metals such as lithium, nickel, and cobalt from battery recyclables, nickel matte, and oxygen pressure slag. Moreover, the recovery rate of valuable metals is high and the recycling cost is low.

[0276] Comparing the experimental data of Comparative Example 1 with those of Example 1, it was found that although additional oxygen was introduced during the matte smelting process in Comparative Example 1, the recovery rate of nickel and cobalt was not improved. Therefore, it can be concluded that no additional oxygen is needed during the matte smelting process.

[0277] Comparing the experimental data of Comparative Example 2 with those of Example 1, it was found that the recovery rate of nickel and cobalt in Comparative Example 2 was significantly lower because no oxygen pressure slag was added during the matte smelting process. Furthermore, comparing the experimental data of Comparative Example 3 with those of Example 1, it was found that even without adding oxygen pressure slag during the matte smelting process in Comparative Example 3, and with additional oxygen introduced, the recovery rate of nickel and cobalt in Comparative Example 3 was still lower than that in Example 1. Therefore, it is evident that by adding oxygen pressure slag in the matte smelting process, it is not necessary to add additional oxygen. This improves the utilization value of the oxygen pressure slag, reduces the cost of valuable metal recovery, increases the recovery rate of valuable metals such as nickel and cobalt, and reduces the safety risks associated with introducing large amounts of external oxygen, as well as the requirements for fire protection and recovery equipment in the plant.

[0278] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0279] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for recycling valuable metals, characterized in that, The recycling method includes: In the roasting process, the battery recyclables and lithium extraction agent are roasted under a protective atmosphere to obtain the roasted product. In the first leaching and separation process, the roasted product is subjected to a first leaching and separation process to obtain a lithium-containing leachate and a leaching residue. In the calcination process, the leaching residue and slag-forming agent are mixed and then calcined to obtain the calcined product. The matte smelting process involves mixing the calcined product, nickel matte, oxygen pressure slag, and matte-forming agent, and then smelting the mixture to obtain nickel-containing matte.

2. The recycling method according to claim 1, characterized in that, In the roasting process, the lithium extraction agent includes one or more of a reducing agent, sulfate, or concentrated sulfuric acid.

3. The recycling method according to claim 2, characterized in that, The reducing agent includes one or more of activated carbon, hydrogen, lignite, anthracite, and carbon monoxide.

4. The recycling method according to claim 2, characterized in that, The sulfate includes one or more of ammonium sulfate and sodium sulfite.

5. The recycling method according to claim 1 or 2, characterized in that, The mass ratio of the battery recycled material to the lithium extraction agent is 20:(1-30).

6. The recycling method according to claim 1 or 2, characterized in that, The calcination temperature is 300℃-1000℃, the heating rate is 2℃ / min-10℃ / min, and the calcination time is 0.5h-5h.

7. The recycling method according to claim 1, characterized in that, The first leaching and separation process includes: In the first leaching step, the roasted product and the first leaching agent are mixed and subjected to a first leaching treatment to dissolve the lithium in the roasted product into the solution to obtain a first leaching slurry containing lithium. In the first separation process, the first leaching slurry is subjected to solid-liquid separation treatment to obtain the lithium-containing leaching solution and the leaching residue.

8. The recycling method according to claim 7, characterized in that, In the first leaching process, the pH of the first leaching treatment is between 3 and 7.

9. The recycling method according to claim 7, characterized in that, In the first leaching process, the temperature of the first leaching treatment is between 30°C and 90°C, and the time of the first leaching treatment is between 0.5h and 4h.

10. The recycling method according to claim 1, characterized in that, In the calcination process, the mass ratio of the leaching residue to the slagging agent is (2-20):

1.

11. The recycling method according to claim 1 or 10, characterized in that, The calcination temperature is 600℃-1000℃, and the calcination time is 2h-8h.

12. The recycling method according to claim 1 or 10, characterized in that, The slag-forming agent includes one or more of silicon dioxide, diatomaceous earth, bentonite, calcium oxide, and aluminum oxide.

13. The recycling method according to claim 1, characterized in that, In the matte smelting process, the mass ratio of the calcined product, the nickel matte, the oxygen pressure slag, and the matte-making agent is 10:(1-30):(1-25):(0.01-30).

14. The recycling method according to claim 1 or 13, characterized in that, The matte-forming agent includes sulfur-containing elements and / or sulfur-containing compounds.

15. The recycling method according to claim 1 or 13, characterized in that, The temperature for matte smelting is 1000℃-1500℃, and the smelting time is 1h-10h.

16. The recycling method according to claim 1, characterized in that, After the first leaching and separation process, the process further includes a drying process to dry the leaching residue, nickel matte, and oxygen pressure residue respectively.

17. The recycling method according to claim 16, characterized in that, The drying temperature is 100℃-300℃, the drying time is 0.5h-4h, and air and / or oxygen are introduced during the drying process.

18. The recycling method according to claim 1, characterized in that, Also includes: In the first pulping step, the matte is mixed with a solvent and then subjected to a first pulping treatment to obtain a first pulping liquid; In the second leaching and separation process, the first slurry and the second leaching agent are mixed and subjected to a second leaching treatment to dissolve the nickel in the first slurry into the solution to obtain a second leaching slurry containing nickel. The second leaching slurry is then subjected to solid-liquid separation treatment to obtain a second filtrate and a second filter residue. In the extraction process, the second filtrate and the extractant are mixed and then extracted to obtain the extract and the raffinate.

19. The recycling method according to claim 18, characterized in that, In the first pulping process, the matte is ground, and the ground matte is mixed with the solvent at a solid-liquid ratio of 1g:(2-15)mL to carry out the first pulping process to obtain the first pulping liquid.

20. The recycling method according to claim 19, characterized in that, The particle size of the ground matte is less than or equal to 48µm.

21. The recycling method according to claim 18 or 19, characterized in that, The temperature of the first pulping treatment is 30℃-90℃, and the time of the first pulping treatment is 0.5h-5h.

22. The recycling method according to claim 18, characterized in that, In the second leaching and separation process, the second leaching agent includes concentrated sulfuric acid, wherein the amount of concentrated sulfuric acid added is 1 to 1.6 times the theoretical amount required to leach all the nickel from the first slurry.

23. The recycling method according to claim 18, characterized in that, The temperature of the second leaching treatment is 50℃-100℃, and the time of the second leaching treatment is 2h-8h.

24. The recycling method according to claim 18, characterized in that, Also includes: In the third leaching and separation process, the second filter residue and the third leaching agent are mixed and subjected to a third leaching treatment to obtain a third leaching slurry. The third leaching slurry is then subjected to solid-liquid separation treatment to obtain a third filtrate and a third filter residue. In the second pulping process, the third filter residue and the solvent are mixed and then subjected to a second pulping treatment to obtain a second pulping liquid. In the fourth leaching and separation process, oxygen is introduced into the second slurry for oxygen pressure leaching to obtain a fourth leaching slurry. The fourth leaching slurry is then subjected to solid-liquid separation to obtain a fourth filtrate and a fourth filter residue.

25. The recycling method according to claim 24, characterized in that, In the third leaching and separation process, the third leaching agent includes concentrated sulfuric acid, wherein the amount of concentrated sulfuric acid added is 1 to 1.3 times the theoretical amount required to leach all the nickel from the second filter residue.

26. The recycling method according to claim 24, characterized in that, In the third leaching separation process, the temperature of the third leaching treatment is 40℃-100℃, and the time of the third leaching treatment is 0.5h-4h.

27. The recycling method according to claim 24, characterized in that, In the second pulping process, the third filter residue and the solvent are mixed at a solid-liquid ratio of 1g:(3-15)ml.

28. The recycling method according to claim 24, characterized in that, In the fourth leaching and separation process, the oxygen partial pressure of the oxygen pressure leaching is 0.6 MPa-1.2 MPa.

29. The recycling method according to claim 24, characterized in that, In the fourth leaching and separation process, the oxygen pressure leaching temperature is 150℃-220℃, and the oxygen pressure leaching time is 2h-8h.

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