Improved high-grade pyrogenic process recovery method for regenerated lithium in battery black powder

Abstract

The invention discloses an improved high-grade pyrogenic process recovery method for regenerated lithium in battery black powder, and belongs to the technical field of battery black powder. The core of the method is that plasma high-temperature volatilization and carbon thermal reduction in-situ synthesis are coupled: firstly, battery black powder and graphite are mixed, lithium is selectively volatilized in a plasma furnace at 1400-1600 DEG C, and the lithium is enriched in smoke dust; then, lithium-rich smoke dust obtained through trapping is mixed with graphite and silicon dioxide, high-temperature smoke gas at the temperature of 700-800 DEG C discharged by a plasma furnace is directly used as a fluidizing medium and a heat source, a reaction is carried out in a fluidized bed at the temperature of 700-850 DEG C, and a high-grade lithium silicate product is synthesized in one step. According to the invention, cascade and closed-loop utilization of system energy is realized, additional fuel is not needed, an unstable intermediate product is directly converted into stable lithium silicate with high additional value, a complex wet purification step is omitted, and the method has the outstanding advantages of high lithium recovery rate, low energy consumption, high product value and green and efficient process.

Description

Technical Field

[0001] This invention relates to the field of battery black powder technology, specifically to an improved method for high-grade pyrometallurgical recovery of lithium from battery black powder. Background Technology

[0002] With the rapid development of the new energy vehicle industry and the approaching peak of power battery scrapping, the efficient recycling of valuable metal resources from spent lithium-ion batteries has become an urgent industry need. Battery black powder, a major byproduct of retired batteries after crushing and sorting, is rich in high-value metal elements such as lithium, nickel, cobalt, and manganese. While traditional wet leaching processes can achieve metal recovery, they generally suffer from problems such as long process flows, high acid and alkali consumption, and high wastewater treatment costs. To overcome the shortcomings of traditional wet processing, the industry has begun to explore a combined pyrometallurgical and wet processing route. For example, Chinese patent CN117019818A discloses a combined pyrometallurgical and wet processing method and system for treating waste lithium-ion battery black powder. This method separates graphite by flotation and uses graphite to prepare CO reducing gas. Under medium-temperature conditions of 550-650℃, high-valence metal oxides in the black powder are reduced to low-valence oxides or metals, followed by wet leaching. While this scheme reduces acid consumption and reducing agent usage to some extent, it still has inherent limitations: First, the reduction temperature used is relatively low, failing to achieve selective volatilization and efficient enrichment of lithium. Lithium still exists in ionic form in the subsequent leachate, resulting in limited grade improvement. Furthermore, it still requires cumbersome wet process steps (such as concentration, precipitation, and purification) for separation and purification, failing to fundamentally escape the constraints of the wet process. Second, the energy utilization of this process is still insufficient. The waste heat generated in the reduction stage fails to form an efficient coupling with subsequent processes, and the overall energy efficiency of the system needs to be improved. In addition, the final product is a mixed metal leachate, which still requires further separation and purification to obtain high-value products, resulting in insufficient process integrity. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an improved method for high-grade pyrometallurgical recovery of lithium from battery black powder, solving the problems mentioned in the background section.

[0004] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: an improved method for high-grade pyrometallurgical recovery of lithium from battery black powder, comprising the following steps: S1. Plasma volatilization enrichment: Battery black powder is mixed with excess graphite and sent into a plasma furnace for high-temperature reaction at 1400-1600℃, so that lithium is selectively volatilized, while nickel, cobalt, manganese and iron metals form an alloy and are discharged from the bottom of the furnace. S2, Dust Collection: The high-temperature flue gas rich in lithium volatiles generated in S1 is collected by a high-temperature gas-solid separation device to obtain lithium-rich dust rich in lithium oxide and lithium hydroxide. S3. Carbothermic reduction and in-situ synthesis: The lithium-rich flue dust obtained in step S2 is mixed with a solid carbon source and silicon dioxide. Using the heat from the high-temperature flue gas discharged from the plasma furnace in step S1, a fluidized bed reaction is carried out at 700-850°C. After carbothermic reduction and carbonation, the lithium in the lithium-rich flue dust reacts with silicon dioxide to synthesize lithium silicate product in one step. S4. Product recovery: Cool and collect the lithium silicate product obtained in S3.

[0005] Preferably, in step S1, the mixing mass ratio of the battery black powder to graphite is 100:25 to 100:45, the reaction temperature of the plasma furnace is 1450-1550℃, and the residence time of the material is less than 0.5 seconds, so as to achieve efficient and rapid volatilization of lithium with a volatilization rate of not less than 80%.

[0006] Preferably, in step S2, the high-temperature gas-solid separation device includes a high-temperature cyclone separator and a ceramic filter; the lithium-rich dust collected has a lithium content of 12%-18% by mass and a particle size of less than 10μm; the collection process is carried out under a closed inert atmosphere to prevent the lithium-rich dust from absorbing moisture or undergoing side reactions.

[0007] Preferably, in step S3, the solid carbon source is graphite, and its addition amount is 5%-15% of the mass of the lithium-rich dust; the silica is quartz sand, and its addition amount is 10%-20% of the mass of the lithium-rich dust, to ensure that lithium is fully converted into the target product lithium silicate.

[0008] Preferably, in step S3, the reaction temperature of the fluidized bed reaction is 750-820℃, and the reaction time is 20-40 minutes; the gas flow medium of the fluidized bed reaction comes directly from the flue gas discharged from the plasma furnace in S1 at a temperature of 700-800℃, without intermediate heat exchange, and is directly introduced into the bottom of the fluidized bed reactor through a pipe, while providing fluidization power and the heat energy required for the reaction.

[0009] Preferably, in step S3, the fluidized bed reaction is a two-stage or multi-stage series reaction, controlling the gas phase composition and temperature of different reaction zones to complete the carbothermic reduction and carbonation of lithium oxide and the synthesis of lithium silicate with silicon dioxide in steps. The first-stage reaction zone focuses on using carbon monoxide in the flue gas to complete the carbothermic reduction and carbonation of lithium oxide, while the second-stage reaction zone focuses on the synthesis of lithium sulfate from lithium carbonate and carbon dioxide at the solid-phase interface.

[0010] Preferably, in step S3, the lithium silicate product has a lithium content of not less than 18% based on lithium oxide. The product has a regular particle morphology with a particle size distribution of 0.1-0.5 mm. It can be directly used as a high-temperature carbon dioxide adsorbent in the field of carbon capture, or it can be prepared into battery-grade lithium carbonate with a purity of more than 99.5% after being leached and purified by inorganic acid.

[0011] Preferably, in step S3, a mineralizing agent is also added to the lithium-rich flue dust. The mineralizing agent is one or two of calcium oxide and sodium carbonate, and the amount added is 0.5%-3% of the mass of the lithium-rich flue dust. The mineralizing agent is used to reduce the activation energy of the lithium sulfate synthesis reaction, promote crystal growth, and improve the reaction rate and product purity.

[0012] Preferably, the process also includes step S5, which involves treating the tail gas in a carbonation tower. The main component of the tail gas produced in step S3 is carbon dioxide. This gas is then reacted with ammonia in a carbonation tower to produce ammonium bicarbonate as a byproduct, thereby achieving carbon fixation and resource utilization, and forming a negative carbon process pathway.

[0013] A system for implementing the above method, characterized in that it comprises: The plasma volatilization furnaces are connected in sequence; A high-temperature dust collection device connected to the flue gas outlet of the plasma volatilization furnace; Carbothermic reduction and synthesis fluidized bed reactor; The flue gas outlet of the plasma volatilization furnace is directly connected to the bottom air inlet of the carbothermic reduction and synthesis fluidized bed reactor via a pipeline, so that the high-temperature flue gas discharged from the plasma volatilization furnace can be directly used as the fluidizing medium and heat source of the fluidized bed reactor.

[0014] (III) Beneficial Effects This invention provides an improved method for high-grade pyrometallurgical recovery of lithium from battery black powder, which has the following beneficial effects: This invention achieves efficient lithium enrichment and high-value product development, constructing a novel all-pyrometallurgical recovery pathway. Addressing the inherent drawbacks of existing pyrometallurgical-hydrometallurgical combined processes where lithium is dispersed in the leachate and subsequent separation steps are cumbersome, this invention employs a two-stage reaction design of "plasma volatilization" and "carbothermic in-situ synthesis" to selectively volatilize and enrich lithium from black powder, directly synthesizing it in one step into a high-grade, stable lithium silicate product. This product has a lithium content of over 18% and can be directly used as a commercial high-temperature carbon dioxide adsorbent, or prepared into battery-grade lithium carbonate through simple acid dissolution.

[0015] 2. This invention achieves efficient cascade utilization of thermal energy through system energy coupling, significantly reducing energy consumption. Addressing the problem of insufficient energy utilization in existing technologies, this invention directly uses the 700-800℃ high-temperature flue gas discharged from the plasma furnace as the fluidizing medium and heat source for the carbothermic reduction and synthesis fluidized bed. This design recovers the sensible heat of the high-temperature flue gas, eliminating the need for a separate external heating source for the fluidized bed. Simultaneously, waste heat recovery is incorporated into the system for material preheating, forming a self-heating cycle. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: like Figure 1 As shown, this embodiment processes crushed and sorted black powder from ternary lithium-ion batteries (NCM811), whose main components (mass percentage) are: Li 2.5%, Ni 32%, Co 12%, Mn 10%, C 8%, with the remainder being oxygen and other trace impurities.

[0019] First, pretreatment is performed, crushing the black powder to a particle size of less than 2 mm and removing mixed iron impurities by magnetic separation. 100 kg of this pretreated black powder is taken and uniformly mixed with 35 kg of artificial graphite powder (35% excess) in a mixer. The mixture is continuously fed into the reaction zone of a plasma vaporization furnace (PAF) through a closed feeding system. Argon gas is introduced into the furnace as the working gas and protective atmosphere, and the temperature at the center of the reaction zone is rapidly raised and stabilized at 1500°C by a plasma torch. The residence time of the material at this high temperature is extremely short, approximately 0.3 seconds. Under these conditions, lithium compounds in the black powder (such as...) , The lithium oxide and lithium hydroxide vapors are rapidly reduced and volatilized, entering the gas phase as lithium oxide and lithium hydroxide vapors, while metals such as nickel, cobalt, and manganese are reduced to molten alloys, which are periodically discharged from the bottom of the furnace and water-quenched to obtain approximately 45 kg of Ni-Co-Mn alloy ingots (total Ni+Co+Mn grade > 85%).

[0020] High-temperature flue gas (approximately 1450°C) rich in lithium vapor then enters a collection system consisting of a high-temperature cyclone separator and a porous ceramic filter connected in series. The system operates entirely under a slightly positive pressure inert atmosphere, effectively collecting lithium-rich flue gas dust. Approximately 8.5 kg of lithium-rich flue gas dust was obtained, and analysis revealed a lithium content of 15.2 wt%, with lithium oxide and lithium carbonate as the main phases, and a particle size D90 of less than 8 µm.

[0021] All 8.5 kg of lithium-rich dust, 0.85 kg of graphite powder (10% of the dust mass), and 1.28 kg of 200-mesh quartz sand (15% of the dust mass) were thoroughly mixed in a small V-type mixer. This mixture was then continuously fed into a carbothermic reduction and synthesis fluidized bed reactor (PICT reactor) via a star feeder. Simultaneously, flue gas from the plasma volatilization furnace, at approximately 750°C, was directly introduced into the bottom of the fluidized bed reactor through an insulated pipe, serving as the fluidizing medium and heat source. The reaction temperature within the fluidized bed was maintained at 800°C, and the average residence time of the materials was 30 minutes. During this process, the following reactions occurred:

[0022] The reaction product was cooled and discharged, yielding approximately 9.8 kg of grayish-white granular product. X-ray diffraction (XRD) analysis confirmed that its main phase was [missing information]. Chemical analysis showed that the lithium content in the product was 18.8% (equivalent to...). (Equivalent weight approximately 48.5%), with particle sizes mainly concentrated in the range of 0.2-0.6 mm. This product can be directly used as a high-temperature... Battery-grade lithium carbonate is prepared by using an adsorbent, or by leaching with dilute sulfuric acid, removing impurities, and precipitating lithium. The calculation in this example involves the process from black powder to... The total lithium recovery rate of the product is 75%.

[0023] Example 2: Optimizing Process Conditions This embodiment is an optimization based on Example 1, aiming to improve the reaction rate and product purity. The raw material used is the same: 100 kg of NCM811 black powder, and the operation of the plasma volatilization section remains unchanged.

[0024] During the carbothermic reduction and synthesis stage, we added an additional 1.5% (by weight of the dust) of a mineralizer (a 1:1 mixture of CaO and...) to the mixture of lithium-rich dust, graphite, and quartz sand. (Mixture). The fluidized bed reactor adopts a two-stage series design: the temperature of the first-stage reactor is controlled at 780℃, utilizing CO and some graphite in the flue gas to mainly complete... Towards The conversion; the temperature of the second-stage reactor is raised to 820°C, and a small amount of air is introduced to consume excess CO and create a more suitable environment. The oxidizing atmosphere of the synthesis promotes and Complete reaction. The total residence time of the material in the two-stage reactor is 35 minutes.

[0025] Under this optimization condition, the obtained The product exhibits higher crystallinity, lower byproduct content, and an increased lithium fixation rate to 97%. Correspondingly, the total lithium recovery rate from black powder to the final product increases to 77.5%. The product also boasts better particle strength, making it more suitable for fluidized bed reactors. Capture system.

[0026] Example 3: Integration of Carbon Negative Process Paths This embodiment demonstrates a complete resource recovery and carbon-negative process. Based on the process in Embodiment 1 or 2, the reaction tail gas (after detection) discharged from the carbothermic reduction and synthesis fluidized bed is processed. The volume concentration is approximately 35%, with the remainder being mainly [missing information]. and a small amount The exhaust gas is collected. It is then introduced into a carbonation absorption tower filled with ammonia water, with the absorption temperature controlled at 20-30℃. The exhaust gas contains... It reacts with ammonia water to produce ammonium bicarbonate crystals. After filtration and drying, approximately 12 kg of pure ammonium bicarbonate fertilizer byproduct is finally obtained. This step utilizes the byproducts generated during the process. By fixing the process, carbon-negative emissions in the lithium recycling process have been achieved, forming a diversified product system of "lithium extraction - alloy production - fertilizer manufacturing", which has significantly improved overall economic and environmental benefits.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An improved method for high-grade pyrometallurgical recovery of lithium from battery black powder, characterized in that, Includes the following steps: S1. Plasma volatilization enrichment: Battery black powder is mixed with excess graphite and sent into a plasma furnace for high-temperature reaction at 1400-1600℃, so that lithium is selectively volatilized, while nickel, cobalt, manganese and iron metals form an alloy and are discharged from the bottom of the furnace. S2, Dust Collection: The high-temperature flue gas rich in lithium volatiles generated in S1 is collected by a high-temperature gas-solid separation device to obtain lithium-rich dust rich in lithium oxide and lithium hydroxide. S3. Carbothermic reduction and in-situ synthesis: The lithium-rich flue dust obtained in step S2 is mixed with a solid carbon source and silicon dioxide. Using the heat from the high-temperature flue gas discharged from the plasma furnace in step S1, a fluidized bed reaction is carried out at 700-850°C. After carbothermic reduction and carbonation, the lithium in the lithium-rich flue dust reacts with silicon dioxide to synthesize lithium silicate product in one step. S4. Product recovery: Cool and collect the lithium silicate product obtained in S3.

2. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: In step S1, the mass ratio of the battery black powder to graphite is 100:25 to 100:45, the reaction temperature of the plasma furnace is 1450-1550℃, and the residence time of the material is less than 0.5 seconds.

3. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: In step S2, the high-temperature gas-solid separation device includes a high-temperature cyclone separator and a ceramic filter; the lithium-rich dust collected has a lithium content of 12%-18% by mass and a particle size of less than 10μm.

4. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: In step S3, the solid carbon source is graphite, and its addition amount is 5%-15% of the mass of the lithium-rich dust; the silica is quartz sand, and its addition amount is 10%-20% of the mass of the lithium-rich dust.

5. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: In step S3, the reaction temperature of the fluidized bed reaction is 750-820℃, and the reaction time is 20-40 minutes; the gas flow medium of the fluidized bed reaction comes directly from the flue gas discharged from the plasma furnace in S1 at a temperature of 700-800℃.

6. An improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 5, characterized in that: In step S3, the fluidized bed reaction is a two-stage or multi-stage series reaction, controlling the gas phase composition and temperature of different reaction zones to complete the carbothermic reduction carbonation of lithium oxide and the synthesis of lithium silicate with silicon dioxide in steps.

7. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: In step S3, the lithium silicate product has a lithium content of not less than 18% based on lithium oxide, and can be used directly as a carbon dioxide adsorbent, or purified by acid dissolution to prepare battery-grade lithium carbonate.

8. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: In step S3, a mineralizing agent is also added to the lithium-rich flue dust. The mineralizing agent is one or two of calcium oxide and sodium carbonate, and the amount added is 0.5%-3% of the mass of the lithium-rich flue dust.

9. The improved method for high-grade pyrometallurgical recovery of lithium from battery black powder according to claim 1, characterized in that: It also includes step S5, which involves the resource utilization treatment of the tail gas. The main component of the reaction tail gas generated in step S3 is carbon dioxide. This gas is introduced into a carbonation tower to react with ammonia water and produce ammonium bicarbonate as a byproduct.

10. A system for implementing the method of any one of claims 1-9, characterized in that, include: The plasma volatilization furnaces are connected in sequence; A high-temperature dust collection device connected to the flue gas outlet of the plasma volatilization furnace; Carbothermic reduction and synthesis fluidized bed reactor; The flue gas outlet of the plasma volatilization furnace is directly connected to the bottom air inlet of the carbothermic reduction and synthesis fluidized bed reactor via a pipeline, so that the high-temperature flue gas discharged from the plasma volatilization furnace can be directly used as the fluidizing medium and heat source of the fluidized bed reactor.

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