Battery key metal element recovery method based on suspension roasting process

Abstract

The invention discloses a battery key metal element recovery method based on a suspension roasting process, and relates to the technical field of battery valuable metal recovery, and the method comprises the following steps: (1) discharging, crushing and disassembling a retired battery to obtain electrode material powder; (2) feeding the powder into a pyrolysis suspension roaster, and heating to remove impurities such as acetylene black conductive agent; (3) feeding an impurity-removed product into a reduction fluidization chamber for reduction suspension roasting, performing coupling reaction on pyrolysis of the positive electrode active layered oxide and combustion of graphite, and decomposing and converting a positive electrode material into Li2O, NiO, CoO and MnO; (4) carrying out water leaching on the reduced suspension roasting product, and enriching and recovering a leaching solution to obtain a lithium-rich pregnant solution; and (5) the lithium extraction leaching residues are subjected to acid leaching and then filtered, filter residues are washed with water, a graphite regeneration material is obtained, and filtrate is a solution rich in nickel, cobalt and manganese metal ions and is used for recycling nickel, cobalt and manganese components. Precise phase conversion and step-by-step leaching efficiency improvement under the suspension roasting system of the retired battery are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery valuable metal recycling, and particularly to a method for recycling key metal elements of batteries based on a suspension roasting process. Background Art

[0002] Lithium-ion power batteries, as an efficient and environmentally friendly electric energy storage carrier, are widely used in large-scale energy storage devices, consumer electronics such as mobile phones, and power batteries. With the booming development of the new energy vehicle and electronic product fields in China, the number of retired power batteries has increased sharply. The disorderly recycling and improper disposal of a large number of retired power batteries have caused serious resource waste and environmental pollution problems. Therefore, the resource recycling of lithium batteries therein has important significance for resource conservation and environmental protection.

[0003] In recent years, many explorations and studies have been carried out in the related fields for the efficient recycling and utilization of key metal elements of retired batteries. Patent CN202110399722.9 discloses a method for recycling the positive electrode powder of used ternary lithium batteries, and proposes to roast the ternary lithium battery positive electrode material and a reducing agent, and perform water leaching treatment on the roasted product, while introducing CO 2 , and obtaining a solution rich in lithium bicarbonate through solid-liquid separation. However, this method has a complex process, a long roasting time (1 - 3 hours), and problems such as low efficiency, poor production continuity, and poor roasting effect.

[0004] From the perspective of strategic resource positioning, lithium-ion batteries contain a large amount of key metal elements such as Co, Ni, Mn, and Li, and the average content is higher than the average content in primary ores, having good recycling prospects. In the process of lithium-ion battery recycling, the general industry is suitable for using the pyrometallurgy - hydrometallurgy process, and among them, the rotary pulverizer - stepwise acid leaching is the most widely applicable process at present. However, the biggest disadvantage of this technology is high energy consumption, high cost, and environmental pollution. Because the rotary pulverizer has poor separation effect and cannot separate the valuable transition metals therein, and the lithium loss rate is relatively high, so stepwise acid leaching needs to separate and enrich the transition metals, which leads to excessive acid consumption and high energy consumption. In view of the above situation, the present invention provides a method for recycling key metal elements of batteries based on a suspension roasting process. Summary of the Invention

[0005] Aiming at the problems existing in the existing technologies for the efficient recycling of retired batteries, the present invention provides a method for recycling key metal elements of batteries based on a suspension roasting process. The present invention recovers valuable metals in retired lithium batteries by means of a combined process of suspension roasting and stepwise leaching, so as to realize the efficient recycling of retired power batteries. The method of the present invention mainly includes operations such as pretreatment, pyrolysis suspension roasting, reduction suspension roasting, water leaching, acid leaching, etc., in order to preferentially extract lithium and achieve the efficient full-component recovery of transition metals from retired batteries. At the same time, a four-stage reverse air system is also set up in the method of the present invention, which can use the high-temperature flue gas generated by high-temperature operations for heating in the previous operations, so as to improve the thermal utilization efficiency of the overall system.

[0006] The present invention realizes the preheating of materials and the removal of organic binders through suspension roasting operations. Then the materials are heated by reduction suspension roasting, in which the pyrolysis of the positive electrode active layered oxide and the combustion of graphite form a coupling reaction. Further, the retired batteries are subjected to reduction suspension roasting, at which time the transition metals exist in the form of elemental substances or low-valent oxides. At the same time, the lattice of the positive electrode material collapses, and the pores of the particles become extremely developed.

[0007] In order to achieve the above object, the present invention provides a method for recycling key metal elements of batteries based on a suspension roasting process, including the following steps:

[0008] The present invention mainly includes operations such as pretreatment, suspension roasting, water leaching, acid leaching, etc., in order to preferentially extract lithium and achieve the efficient full recovery of the reduction of transition metals from retired batteries. At the same time, a four-stage reverse air system is also set up in the method of the present invention, which can use the high-temperature flue gas generated by high-temperature operations for heating in the previous operations, so as to improve the thermal utilization efficiency of the overall system.

[0009] 1. Pretreatment process: Discharge, crush, and disassemble the retired batteries for pretreatment to obtain the powder of the mixed electrode materials of the retired batteries.

[0010] 2. Pyrolysis suspension roasting: Feed the powder of the mixed electrode materials of the retired batteries into a pyrolysis suspension roasting furnace, and control the temperature range at 300°C to 400°C, aiming to remove impurities including acetylene black conductive agent and organic binder PVDF in a suspended state to obtain a deimpurified product.

[0011] 3. Reduction suspension roasting: Feed the deimpurified product into a reduction fluidized chamber for reduction suspension roasting, and stabilize the temperature at 600°C to 850°C. In this stage, mainly through the coupling reaction of the pyrolysis of the positive electrode active layered oxide (LiNi x Co y Mn 1-x-y O 2 ) and the combustion of graphite, the positive electrode material decomposes and transforms into Li 2O, NiO, CoO, and MnO; simultaneously introduce nitrogen into the reduction fluidized bed chamber and adjust the total gas flow rate to make the materials in the reduction fluidized bed chamber in a suspended state, with a residence time of 20 min to 60 min. During the reduction suspension roasting process, part of the newly formed lithium oxide (Li 2 O) in the inner layer is reduced at high temperature to form lithium carbonate (Li 2 CO 3 ) and transfers to the outer layer, obtaining a reduction suspension roasting product with easy water solubility.

[0012] 4. Water leaching: Perform water leaching on the reduction suspension roasting product, select deionized water as the leaching agent, with a leaching time of 100 min to 150 min. After leaching and dissolution, enrich and recover the leaching solution to obtain a lithium-rich precious liquid, with a Li leaching rate reaching over 95%. The lithium extraction leaching residue is used for subsequent recovery of nickel, cobalt, and manganese metals.

[0013] 5. Acid leaching: Redissolve the lithium extraction leaching residue, with the leaching solution being a sulfuric acid solution with a concentration of 1 mol / L to 5 mol / L. After the leaching is completed, filter to obtain a residue phase and a filtrate. Wash the filter residue with water to obtain a regenerated graphite material, and the filtrate is a solution rich in metal ions such as nickel, cobalt, and manganese, which is used for the recovery of components such as nickel, cobalt, and manganese.

[0014] The method for recovering key metal elements of a battery based on a suspension roasting process according to the present invention, wherein:

[0015] In the step 1, the Li grade of the positive electrode active material in the retired battery is 2.5% to 6%, the Co grade is 2.5% to 8%, the Ni grade is 13% to 30%, and the Mn grade is 5% to 15%; the main negative electrode material in the retired battery is graphite, and the C grade is 30% to 50%. In the step 4 and step 5, the number of times of washing the filter residue is not less than 2 times.

[0016] In the step 2, the main purpose of the pyrolysis suspension roasting is to decompose organic impurities through high-temperature pyrolysis, and utilize the efficient heat transfer and mass transfer characteristics in the suspended state to achieve efficient removal of impurities. By precisely controlling the temperature in the range of 300°C to 400°C and heating for 15 min to 30 min, other side reactions caused by too high temperature can be effectively avoided, while ensuring that the organic impurities can be fully pyrolyzed. Achieving relative unity of the phases in the subsequent process is beneficial to the precise control of the subsequent reduction crystal evolution process and the improvement of quality and efficiency in the subsequent leaching process.

[0017] In the step 3, the positive electrode active layered oxide (LiNi x Co y Mn 1-x-y O 2) The pyrolysis of x Co y Mn 1-x-y O 2 forms a coupled reaction with the combustion of graphite, specifically including energy coupling and product coupling. Energy coupling means that the heat released by the combustion of graphite provides additional energy for the pyrolysis of the cathode material, reducing the external energy input required for pyrolysis. Product coupling means that the oxygen generated during the pyrolysis process (such as the oxygen generated by the activation of lattice oxygen caused by the change of the oxidation state of nickel in the high-nickel LiNi

[0018] In step 4, the leaching temperature is controlled at 20°C to 50°C, and the liquid-solid ratio (L / S) is 4 mL / g to 25 mL / g.

[0019] In step 5, the liquid-solid ratio (L / S) is 3 mL / g to 10 mL / g, the system is heated to 50°C to 100°C, and the reaction is carried out for 30 min to 120 min.

[0020] The Li leaching rate in the lithium-rich pregnant solution obtained by the method of the present invention is 95% to 99%, and more than 95% of Ni, more than 95% of Mn, and more than 95% of Co are leached from the water leaching residue.

[0021] In the method of the present invention, in order to improve the thermal efficiency in the whole recycling process of retired ternary lithium batteries, by recovering and reusing the heat in the high-temperature flue gas, the energy consumption is reduced and the economic benefit is improved. A four-time return air system is set up, which is respectively set in the pyrolysis suspension roasting link, the reduction suspension roasting link, the water leaching link, and the acid leaching link.

[0022] In the pyrolysis suspension roasting stage, the retired battery materials are heated to 300°C - 400°C to remove impurities such as the organic binder PVDF. The high-temperature flue gas generated in this stage can be captured and used to preheat the retired battery materials about to enter the pyrolysis suspension roasting furnace. The reduction suspension roasting is carried out at 600°C - 850°C, and a large amount of high-temperature flue gas is generated in this stage. These flue gases can be captured and used to preheat the furnace charge in the pyrolysis suspension roasting stage, or directly used to preheat the deionized water required for the water leaching stage. The water leaching stage itself does not generate a large amount of high-temperature flue gas, but the high-temperature flue gas generated in the previous stage (reduction suspension roasting) can be used to preheat the deionized water required for water leaching, thus saving the energy required for heating water. In the acid leaching stage, the system is heated to 50°C - 100°C. The high-temperature flue gas from the reduction suspension roasting stage can be used in this stage to preheat the sulfuric acid solution required for acid leaching, thereby reducing the energy required for direct heating.

[0023] Compared with the existing comprehensive recycling methods for retired batteries, the features and advantages of the present invention are as follows:

[0024] 1. The present invention realizes the precise phase transformation and stepwise leaching efficiency improvement in the suspension roasting system of retired batteries. The organic binder and other impurities are effectively decomposed to prevent the formation of LiF from affecting subsequent extraction processes such as extraction, and the metal oxides are activated by heat storage to be fully activated, significantly improving the subsequent reduction suspension roasting efficiency.

[0025] 2. The method of the present invention can reduce energy consumption by 30% - 60% compared with the rotary pulverization furnace - stepwise acid leaching process. One reason is that four times of return air are set in the whole process, greatly improving the system heat utilization efficiency. Another reason is that the heat storage process has been realized during the pyrolysis process of the material, which can greatly shorten the time of crystal form distortion at high temperature and significantly reduce energy consumption.

[0026] 3. Compared with the existing methods, the suspension roasting technology adopted in the present invention has a higher heat and mass transfer efficiency compared with rotary kiln roasting. The gas contacts the mineral particles more fully and the reaction is more complete. And the negative electrode material graphite is used as a reducing agent for in-situ roasting reduction, which can reduce the use of fossil energy. Compared with the traditional rotary pulverization furnace roasting that requires a large amount of coke and semi-coke to be added into the furnace, the method of the present invention is more low-carbon and clean, and has a high reduction efficiency.

[0027] 4. Compared with the existing methods, the stepwise leaching method is used to efficiently recover nickel, cobalt, and manganese in retired batteries, with a high recovery efficiency, very little residue of key metal elements, the whole recovery process is simple and easy to operate, and the washing liquid of the leaching residue contains a small amount of cobalt, manganese, and nickel. It has strong adaptability to different types of retired ternary lithium batteries, and the equipment is easy to be scaled up and industrialized. Description of the Drawings

[0028] Figure 1Process flow diagram of the recovery method of key metal elements of the battery based on the suspension roasting process of the present invention. Detailed implementation manners

[0029] The following combines examples and drawings to clearly and completely describe the technical solutions in the implementation of the present invention. It should be noted that the described examples of the present invention are only used for further explanation and illustration, rather than limiting its application scope. Based on the present invention, all other examples obtained by those skilled in the art without creative work belong to the protection scope of the present invention. The process flows of the following Examples 1-4 are as Figure 1 shown.

[0030] Example 1

[0031] In this Example 1, the retired ternary lithium battery comes from a certain technology company in Guangdong. Its Li grade is 3.59%, Co grade is 4.59%, Mn grade is 9.58%, Ni grade is 17.15%, C grade is 40.20%, and C mainly exists in the form of graphite.

[0032] 1. Pretreatment process: Perform pretreatment work such as discharging, crushing, and disassembling on the retired battery to obtain the mixed electrode material powder of the retired battery.

[0033] 2. Pyrolysis suspension roasting: Feed the mixed electrode material powder of the retired battery into the pyrolysis suspension roasting furnace, control the temperature at 300 °C, and heat for 30 min. Mainly remove impurities such as acetylene black conductive agent and organic binder PVDF in the suspended state to obtain a deimpurified product. This stage is mainly to remove impurities such as acetylene black conductive agent and organic binder PVDF in the mixed electrode material powder, realize the relative unity of the subsequent process phases, and is conducive to the precise control of the subsequent reduction crystal evolution process and the higher purity in the subsequent leaching process.

[0034] 3. Reduction suspension roasting: Feed the deimpurified product into the reduction fluidized chamber for reduction suspension roasting, and the temperature is stabilized at 750 °C. This stage is mainly to couple the pyrolysis of the positive electrode active layered oxide (LiNi x Co y Mn 1-x-y O 2 ) and the combustion of graphite, so that the positive electrode material decomposes and transforms into Li 2 O, NiO, CoO and MnO; and introduce nitrogen into the reduction fluidized chamber, and adjust the total gas flow rate to make the materials in the reduction fluidized chamber in a suspended state, and the residence time is 60 min. During the reduction suspension roasting process, part of the inner-layer newly formed lithium oxide (Li 2 O) is reduced at high temperature to form lithium carbonate and transfers to the outer layer to obtain a reduction suspension roasting product with easy water solubility.

[0035] 4. Water leaching: The reduced suspension roasting product is subjected to water leaching. Deionized water is selected as the leaching agent, the leaching time is 120 min, the leaching temperature is controlled at 20 °C, the liquid-solid ratio is determined to be 20 mL / g. After leaching and dissolution, the leaching solution is enriched and recovered to obtain a lithium-rich precious liquid, and the Li leaching rate reaches 97%. The lithium leaching residue is used for subsequent recovery of nickel, cobalt, and manganese metals.

[0036] 5. Acid leaching: The lithium leaching residue is redissolved. The leaching solution is a sulfuric acid solution with a concentration of 2 mol / L. The liquid-solid ratio L / S is determined to be 5 mL / g. Then the system is heated to 60 °C. After reacting for 60 min, filtration is carried out to obtain a slag phase and a filtrate. The filter residue is washed with water to obtain a graphite regeneration material, and the filtrate is rich in metal ions such as nickel, cobalt, and manganese. The leaching rate of Ni in the acid leaching solution is 96.6%, the leaching rate of Mn is 99.5%, and the leaching rate of Co is 99.2%.

[0037] Example 2

[0038] In this Example 2, the retired ternary lithium battery comes from a certain technology company in Hunan. Its Li grade is 3.87%, Co grade is 3.16%, Mn grade is 5.22%, Ni grade is 22.47%, C grade is 35.36%, and C mainly exists in the form of graphite.

[0039] 1. Pretreatment process: The retired battery is subjected to pretreatment work such as discharging, crushing, and disassembling to obtain the mixed electrode material powder of the retired battery.

[0040] 2. Pyrolysis suspension roasting: The mixed electrode material powder of the retired battery is fed into the pyrolysis suspension roasting furnace. The temperature is controlled at 350 °C and heated for 20 min. Mainly impurities such as acetylene black conductive agent and organic binder PVDF are removed in the suspended state to obtain a product after impurity removal. This stage is mainly to remove impurities such as acetylene black conductive agent and organic binder PVDF in the mixed electrode material powder, realize the relative unity of the phase in the subsequent process, and is conducive to the precise control of the subsequent reduction crystal evolution process and the higher purity in the subsequent leaching process.

[0041] 3. Reduction suspension roasting: The product after impurity removal is fed into the reduction fluidized chamber for reduction suspension roasting. The temperature is stabilized at 800 °C. This stage is mainly to couple the pyrolysis of the positive electrode active layered oxide (LiNi x Co y Mn 1-x-y O 2 ) with the combustion of graphite, so that the positive electrode material decomposes and transforms into Li 2 O, NiO, CoO, and MnO; and nitrogen is introduced into the reduction fluidized chamber, and the total gas flow rate is adjusted to make the materials in the reduction fluidized chamber in a suspended state, and the residence time is 45 min. During the reduction suspension roasting process, part of the newly formed lithium oxide (Li 2O) Lithium carbonate is generated by high-temperature reduction and transferred to the outer layer to obtain a reduction suspension roasting product with easy water solubility.

[0042] 4. Water leaching: The reduction suspension roasting product is subjected to water leaching treatment. Deionized water is selected as the leaching agent, the leaching time is 150 min, the leaching temperature is controlled at 30 °C, the liquid-solid ratio is determined to be 15 mL / g, and the leaching solution is enriched and recovered after leaching and dissolution to obtain a lithium-rich precious liquid, with the Li leaching rate reaching 95%. The lithium leaching residue is used for subsequent recovery of nickel, cobalt, and manganese metals.

[0043] 5. Acid leaching: The lithium leaching residue is redissolved, the leaching solution is a sulfuric acid solution with a concentration of 3 mol / L, the liquid-solid ratio L / S is determined to be 7 mL / g, and then the system is heated to 65 °C. After reacting for 70 min, filtration is carried out to obtain a slag phase and a filtrate. The filter residue is washed with water to obtain a regenerated graphite material, and the filtrate is rich in metal ions such as nickel, cobalt, and manganese. The leaching rate of Ni in the acid leaching solution is 95.8%, the leaching rate of Mn is 99.2%, and the leaching rate of Co is 99.3%.

[0044] Example 3

[0045] In this Example 3, the retired ternary lithium battery comes from a certain technology company, with its Li grade of 4.56%, Co grade of 3.25%, Mn grade of 4.59%, Ni grade of 22.23%, C grade of 38.09%, and C mainly occurring in the form of graphite.

[0046] 1. Pretreatment process: The retired battery is subjected to pretreatment work such as discharging, crushing, and disassembling to obtain a powder of the retired battery mixed electrode material.

[0047] 2. Pyrolysis suspension roasting: The powder of the retired battery mixed electrode material is fed into a pyrolysis suspension roasting furnace, the temperature is controlled at 350 °C, and it is heated for 25 min. Mainly, impurities such as acetylene black conductive agent and organic binder PVDF are removed in the suspended state to obtain a product after impurity removal. This stage is mainly to remove impurities such as acetylene black conductive agent and organic binder PVDF in the mixed electrode material powder, achieve relative unity of the phases in the subsequent process, facilitate precise control of the subsequent reduction crystal evolution process, and ensure higher purity in the subsequent leaching process.

[0048] 3. Reduction suspension roasting: The product after impurity removal is fed into a reduction fluidized chamber for reduction suspension roasting, and the temperature is stabilized at 800 °C. In this stage, the pyrolysis of the positive electrode active layered oxide (LiNi x Co y Mn 1-x-y O 2 ) and the combustion of graphite form a coupled reaction, causing the positive electrode material to decompose and transform into Li 2O, NiO, CoO, and MnO; nitrogen gas is introduced into the reduction fluidized chamber, and the total gas flow rate is adjusted to make the materials in the reduction fluidized chamber in a suspended state, with a residence time of 45 minutes. During the reduction suspension roasting process, part of the newly formed lithium oxide (Li 2 O) in the inner layer is reduced at high temperature to form lithium carbonate and transferred to the outer layer, obtaining a reduction suspension roasting product with easy water solubility.

[0049] 4. Water leaching: The reduction suspension roasting product is subjected to water leaching treatment. Deionized water is selected as the leaching agent, the leaching time is 150 minutes, the leaching temperature is controlled at 30 °C, the liquid-solid ratio is determined to be 15 mL / g, and after leaching and dissolution, the leaching solution is enriched and recovered to obtain a lithium-rich precious liquid, with a Li leaching rate reaching 95%. The lithium extraction leaching residue is used for subsequent recovery of nickel, cobalt, and manganese metals.

[0050] 5. Acid leaching: The lithium extraction leaching residue is redissolved, the leaching solution is a sulfuric acid solution with a concentration of 3 mol / L, the liquid-solid ratio L / S is determined to be 7 mL / g, and then the system is heated to 65 °C. After reacting for 70 minutes, filtration is carried out to obtain a slag phase and a filtrate. The filter residue is washed with water to obtain a graphite regenerated material, and the filtrate is rich in metal ions such as nickel, cobalt, and manganese. The leaching rate of Ni in the acid leaching solution is 95.9%, the leaching rate of Mn is 99.2%, and the leaching rate of Co is 99.3%.

[0051] Example 4

[0052] In this Example 4, the retired ternary lithium battery comes from a certain technology company, with a Li grade of 3.89%, a Co grade of 3.21%, a Mn grade of 5.17%, a Ni grade of 20.67%, and a C grade of 38.61%. C mainly exists in the form of graphite.

[0053] 1. Pretreatment process: The retired battery is subjected to pretreatment work such as discharging, crushing, and disassembling to obtain a retired battery mixed electrode material powder.

[0054] 2. Pyrolysis suspension roasting: The retired battery mixed electrode material powder is fed into a pyrolysis suspension roasting furnace, the temperature is controlled at 400 °C, and it is heated for 15 minutes. Mainly, impurities such as acetylene black conductive agent and organic binder PVDF are removed in a suspended state to obtain a deimpurified product. This stage is mainly to remove impurities such as acetylene black conductive agent and organic binder PVDF in the mixed electrode material powder, achieve relative unity of the phases in the subsequent process, facilitate precise control of the subsequent reduction crystal evolution process, and ensure higher purity in the subsequent leaching process.

[0055] 3. Reduction suspension roasting: The deimpurified product is fed into a reduction fluidized chamber for reduction suspension roasting, and the temperature is stabilized at 700 °C. This stage is mainly to reduce the positive electrode active layered oxide (LiNi x Co y Mn 1-x-y O2 ) The pyrolysis and the combustion of graphite form a coupled reaction, which decomposes the cathode material and transforms it into Li 2 O, NiO, CoO, and MnO; nitrogen is introduced into the reduction fluidized bed chamber, and the total gas flow rate is adjusted to make the materials in the reduction fluidized bed chamber in a suspended state, with a residence time of 50 min. During the reduction suspension roasting process, part of the newly formed lithium oxide (Li 2 O) is reduced at high temperature to form lithium carbonate and transferred to the outer layer, obtaining a reduction suspension roasting product with good water solubility.

[0056] 4. Water leaching: The reduction suspension roasting product is subjected to water leaching treatment. Deionized water is selected as the leaching agent, the leaching time is 100 min, the leaching temperature is controlled at 25 °C, the liquid-solid ratio is determined to be 15 mL / g. After leaching and dissolution, the leaching solution is enriched and recovered to obtain a lithium-rich precious liquid, and the lithium leaching rate reaches 96%. The leaching residue for lithium extraction is used for subsequent recovery of nickel, cobalt, and manganese metals.

[0057] 5. Acid leaching: The leaching residue for lithium extraction is redissolved. The leaching solution is a sulfuric acid solution with a concentration of 2 mol / L. The liquid-solid ratio L / S is determined to be 10 mL / g. Then the system is heated to 50 °C. After reacting for 50 min, filtration is carried out to obtain the slag phase and the filtrate. The filter residue is washed with water to obtain the regenerated graphite material, and the filtrate is rich in metal ions such as nickel, cobalt, and manganese. The leaching rate of Ni in the acid leaching solution is 96.8%, the leaching rate of Mn is 99.6%, and the leaching rate of Co is 99.4%.

[0058] Comparative Example 1

[0059] Same as Example 1, the difference is that in this Comparative Example 1, pyrolysis suspension roasting is not carried out, and the mixed electrode material powder is directly fed into the reduction fluidized bed chamber. Finally, the leaching rate of the lithium-rich precious liquid is only 89.45%. Compared with Example 1, the reduction suspension roasting time in this Comparative Example 1 is increased by 15 min. This is because the organic binder is not pyrolyzed in advance, and the direct mineral phase transformation of the cathode material requires a heat storage process, resulting in a significant increase in the phase transformation time.

[0060] Comparative Example 2

[0061] Same as Example 2, the difference is that in this Comparative Example 2, reduction suspension roasting is carried out in the reduction fluidized bed chamber, the stable temperature is 550 °C, and the reduction suspension roasting time is increased by 30 min. Compared with Example 2, although the roasting time is extended, due to the lower temperature, the reaction rate slows down, resulting in incomplete decomposition of some oxides. The overall reaction efficiency and leaching rate are affected. The leaching rate of the lithium-rich precious liquid is only 91.01%. Due to the incomplete decomposition of the oxides, the leaching rates of Ni, Co, and Mn also decrease significantly, especially the leaching rates of Co and Mn, which are as low as 89.65% and 90.22%, respectively. The overall recovery effect is not as good as that of Example 2.

[0062] Comparative Example 3

[0063] Same as Example 3. The difference is that the residence time in the reduction fluidized chamber in this Comparative Example 3 is 10 min, resulting in incomplete reaction, partial incomplete decomposition of the cathode material, affecting the formation of metal oxides, and further affecting the subsequent leaching efficiency of metal elements. The leaching rate of lithium-rich pregnant solution is only 85.88%. Due to incomplete decomposition of the oxide, the leaching rates of Ni, Co, and Mn also decrease significantly, down to 87.40%, 86.67%, and 87.51% respectively.

[0064] Comparative Example 4

[0065] Same as Example 4. The difference is that in this Comparative Example 4, pyrolysis suspension roasting is not carried out, and the mixed electrode material powder is directly fed into the reduction fluidized chamber, and finally the leaching rate of the lithium-rich pregnant solution obtained is only 89.69%. Compared with Example 4, the reduction suspension roasting time in this Comparative Example 4 increases by 15 min. This is because the organic binder is not pyrolyzed in advance, and the direct mineral phase transformation of the cathode material requires a heat storage process, resulting in a significant increase in the phase transformation time.

Claims

1. A method for recovering key metal elements of batteries based on a suspension roasting process, characterized in that: The following steps are involved: (1) Pretreatment process: Discharging, crushing and disassembling the retired batteries to obtain the retired battery mixed electrode material powder; (2) Pyrolysis suspension roasting: The retired battery mixed electrode material powder is fed into a pyrolysis suspension roasting furnace, and the temperature is controlled in the range of 300°C to 400°C to remove impurities including acetylene black conductive agent and organic binder PVDF in a suspended state to obtain a decontaminated product; (3) Reduction suspension roasting: The impurity-removed product is fed into a reduction fluidized chamber for reduction suspension roasting, and the temperature is stabilized at 600°C to 850°C. The positive electrode material is decomposed and converted into Li2O, NiO, CoO and MnO through the pyrolysis of the positive electrode active layered oxide and the combustion of graphite. (4) Water leaching: The reduction suspension roasting product is subjected to water leaching treatment, deionized water is selected as the leaching agent, and the leaching time is 100 min to 150 min. After leaching and dissolution, the leaching liquid is enriched and recovered to obtain lithium-rich precious liquid; (5) Acid leaching: The lithium leaching residue is redissolved, and the leaching solution is a sulfuric acid solution with a concentration of 1 mol / L to 5 mol / L. After the leaching is completed, the residue phase and the filtrate are filtered out. The filtered residue is washed with water to obtain graphite regeneration material. The filtrate is a solution rich in nickel, cobalt, and manganese metal ions, which is used for the recovery of nickel, cobalt, and manganese components.

2. The method for recovering key metal elements of batteries based on a suspension roasting process according to claim 1, characterized in that: In the step (1), the retired battery contains positive electrode active materials of Li with a grade of 2.5% to 6%, Co with a grade of 2.5% to 8%, Ni with a grade of 13% to 30%, and Mn with a grade of 5% to 15%. The main negative electrode material in the retired battery is graphite, with a C grade of 30% to 50%.

3. The method for recovering key metal elements of batteries based on a suspension roasting process according to claim 1, characterized in that: In the step (2), the temperature is controlled within the range of 300° C. to 400° C., and the heating time is 15 min to 30 min.

4. The method for recovering key metal elements of batteries based on a suspension roasting process according to claim 1, characterized in that: In the step (3), nitrogen is introduced into the reduction fluidizing chamber at the same time, and the total gas flow rate is adjusted so that the material in the reduction fluidizing chamber is in a suspended state, and the residence time is 20 minutes to 60 minutes.

5. The method for recovering key metal elements of batteries based on suspension roasting process according to claim 1, characterized in that: In the step (4), the leaching temperature is controlled at 20°C to 50°C, and the liquid-to-solid ratio is 4mL / g to 25mL / g.

6. The method for recovering key metal elements of batteries based on a suspension roasting process according to claim 1, characterized in that: In the step (5), the liquid-to-solid ratio is 3 mL / g to 10 mL / g, the system is heated to 50° C. to 100° C., and the reaction is carried out for 30 min to 120 min.

7. The method for recovering key metal elements of batteries based on suspension roasting process according to claim 1, characterized in that: The Li leaching rate in the lithium-rich precious liquid obtained in step (4) is 95% to 99%, and more than 95% of Ni, more than 95% of Mn and more than 95% of Co are leached from the water leaching residue.

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