Method for preparing high-purity black powder from waste lithium battery at low temperature and waste gas treatment process

Abstract

The present application relates to the technical field of waste lithium battery recycling, and discloses a method for preparing high-purity black powder from waste lithium batteries through low-temperature disassembly and a waste gas treatment process, wherein aluminum, organic matter and black powder are separated through step-by-step treatment to obtain high-purity battery black powder; fluorine and phosphorus are preferentially removed at low temperature, strong alkali is not used to avoid the competitive reaction of hydroxyl ions with carbonates and carbon dioxide, and subsequent equipment corrosion is prevented. First-stage water washing simultaneously realizes water-soluble organic matter absorption, phosphorus pentafluoride decomposition, phosphoric acid absorption and pH reduction to inhibit hydrogen fluoride absorption, and no aluminum ions are generated to form aluminum phosphate precipitates, so that a packed tower can be used; second-stage aluminum salt solution absorbs hydrogen fluoride under acidic conditions to form a dissolved fluorine-aluminum complex, which is not affected by carbon dioxide, and a packed tower can be used. The fluorine-aluminum complex solution can be processed into cryolite to realize fluorine resource recycling and avoid environmental risks.

Description

Technical Field

[0001] This invention relates to the field of waste lithium battery recycling technology, and in particular to a method for preparing high-purity black powder from waste lithium batteries at low temperature and a waste gas treatment process. Background Technology

[0002] In the dismantling and recycling of waste lithium batteries, black powder is an important recycled product. During the dismantling process, the higher the drying temperature, the more thoroughly the organic matter in the electrolyte volatilizes, and the lower the residual organic matter content in the resulting black powder. However, the higher the drying temperature, the easier it is for the aluminum foil to pulverize, and it is easy to break into aluminum powder with the same particle size as the black powder during the subsequent grinding process, making it difficult to effectively separate from the black powder.

[0003] Among existing dismantling technologies, high-temperature dismantling yields black powder with low organic matter content but high aluminum content; while low-temperature dismantling yields black powder with low aluminum content but high organic matter content. Low-temperature dismantling technology can condense and recover the electrolyte, achieving resource utilization. It eliminates the need for large-scale organic waste gas purification equipment, has low waste gas emissions, and significant low-carbon benefits, making it the development direction of green dismantling technology. However, existing technologies make it difficult to simultaneously obtain high-quality black powder products with low aluminum and low organic matter content through a single dismantling process. Summary of the Invention

[0004] The purpose of this invention is to provide a method and waste gas treatment process for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries, which solves the problem that existing dismantling technologies are unable to obtain black powder with low aluminum and low organic matter content at the same time.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries, comprising the following steps: After waste lithium batteries are crushed, a mixture containing electrolyte and solids is obtained. The mixture is then dried under vacuum to vaporize the low-boiling-point electrolyte carbonate organic matter, thus achieving primary separation of the electrolyte and solid materials. A dried solid material is subjected to screening, grinding, air separation, and magnetic separation processes to separate and recover black powder, copper powder, aluminum powder, steel shell, and plastic, resulting in black powder with low aluminum content. The black powder is dried twice at a temperature of 250-350℃ to remove high-boiling-point carbonate organic matter, and the volatile organic gases are mixed with low-temperature evaporated gases. The organic vapor in the electrolyte is cooled down, causing the organic matter to re-condense into liquid organic matter, thus realizing the recovery of organic matter in the electrolyte.

[0006] The vacuum drying temperature is <120℃. Low-temperature drying avoids embrittlement of the aluminum foil, maintains its toughness, and makes it less likely to break into powder with the same particle size as the black powder during subsequent grinding, thereby achieving effective separation of aluminum and black powder.

[0007] The resulting black powder is subjected to secondary drying at a temperature of 250-350℃ to remove high-boiling-point carbonate organic matter, thereby further reducing the amount of residual organic matter in the black powder.

[0008] The process involves a step-by-step drying process to remove low-boiling-point and high-boiling-point organic matter separately. First, vacuum drying at <120℃ is used to remove the low-boiling-point electrolyte, and then secondary drying at 250-350℃ is used to remove the high-boiling-point carbonate organic matter, thus avoiding the problem of aluminum foil pulverization caused by using a single high-temperature drying method.

[0009] Secondly, the waste gas treatment process for the low-temperature dismantling of waste lithium batteries to prepare high-purity black powder, used in the method for preparing high-purity black powder from low-temperature dismantling of waste lithium batteries as described in the first aspect, includes the following steps: First-grade detergent uses water, and water-soluble organic matter is absorbed by the water. Phosphorus pentafluoride decomposes into hydrogen fluoride and phosphoric acid when it comes into contact with water. The absorption of phosphoric acid leads to a decrease in pH, which inhibits the absorption of hydrogen fluoride. The secondary stage uses aluminum sulfate solution to absorb hydrogen fluoride, forming a fluorine-aluminum mixed solution with strong complexing ability, which deeply removes fluorides from the waste gas; The organic waste gas after the aforementioned fluorine and phosphorus removal is added to a thermal oxidation incinerator for incineration to remove organic matter, resulting in purified high-temperature flue gas. The absorbent obtained from the first-stage washing process is mixed with calcium salt to neutralize phosphorus and produce calcium phosphate, which is then separated from the solution to obtain organic waste liquid. The organic waste liquid obtained above after phosphorus removal is subjected to indirect heat exchange with the high-temperature flue gas obtained from the thermal oxidation incinerator, so that the organic matter in the solution is re-evaporated into organic waste gas and returned to the thermal oxidation incinerator for high-temperature incineration removal. The solution used to remove organic matter is returned to the primary washing stage for recycling. The solution obtained from the aforementioned secondary absorption is processed into aluminum fluoride or cryolite to achieve the recovery of fluorine resources.

[0010] This invention discloses a method for preparing high-purity battery black powder from the low-temperature dismantling of waste lithium batteries. Through distributed processing, it achieves the separation of aluminum and organic matter from the black powder, resulting in high-purity battery black powder. It achieves efficient and resource-efficient waste gas purification: under low-temperature conditions, fluorine and phosphorus are preferentially removed, but strong alkalis cannot be used to avoid competitive reactions between hydroxide ions and carbonates and carbon dioxide, reducing the removal efficiency of hydrogen fluoride. Low-temperature preferential removal of fluorine and phosphorus prevents corrosion of equipment related to subsequent organic matter combustion and heat exchange processes. The first stage uses water washing to achieve four objectives: absorption of water-soluble organic matter; decomposition of phosphorus pentafluoride; absorption of phosphoric acid (leading to pH reduction); and pH reduction inhibiting hydrogen fluoride absorption. Furthermore, the absence of aluminum ions prevents the formation of aluminum phosphate precipitate, allowing the use of packed towers with better gas-liquid contact and improved reaction efficiency. The second stage uses aluminum salt solution absorption to obtain a fluorine-aluminum complex, achieving good absorption even under acidic conditions, without considering the influence of carbon dioxide on the absorption process. The fluorine-aluminum complex is in a dissolved state, without solid formation, allowing the use of packed towers with better gas-liquid contact and improved reaction efficiency. The resulting fluorine-aluminum complex solution can be further processed into cryolite, realizing the resource recovery of highly toxic fluorine and avoiding environmental risks. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0012] Figure 1 This is a flowchart of the method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries provided by the present invention.

[0013] Figure 2 This is a flowchart of the waste gas treatment process for preparing high-purity black powder from the low-temperature dismantling of waste lithium batteries provided by the present invention. Detailed Implementation

[0014] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0015] Please see Figure 1 In a first aspect, the present invention provides a method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries, comprising the following steps: After the S1 waste lithium battery is crushed, a mixture containing electrolyte and solids is obtained. The mixture is then dried under vacuum to vaporize the low-boiling-point electrolyte carbonate organic matter, thus achieving primary separation of the electrolyte and solid materials. The vacuum drying temperature is <120℃. Low-temperature drying avoids embrittlement of the aluminum foil, maintains its toughness, and makes it less likely to break into powder with the same particle size as the black powder during subsequent grinding, thereby achieving effective separation of aluminum and black powder.

[0016] S2 involves a process of screening, grinding, air separation, and magnetic separation of a dried solid material to separate and recycle black powder, copper powder, aluminum powder, steel shell, and plastic, resulting in black powder with low aluminum content. The obtained black powder is dried a second time at a temperature of 250-350℃ to remove high-boiling-point carbonate organic matter and further reduce the amount of residual organic matter in the black powder.

[0017] The low-boiling-point and high-boiling-point organic matter is removed separately by step-by-step drying. First, vacuum drying at <120℃ is used to remove the low-boiling-point electrolyte, and then secondary drying at 250-350℃ is used to remove the high-boiling-point carbonate organic matter, thus avoiding the problem of aluminum foil pulverization caused by using a single high-temperature drying.

[0018] S3 involves secondary drying of the black powder at a temperature of 250-350℃ to remove high-boiling-point carbonate organic matter, and mixing the volatile organic gases with the low-temperature evaporated gases. S4 cools down the organic vapor in the electrolyte, causing the organic matter to re-condense into liquid organic matter, thus achieving the recovery of organic matter from the electrolyte.

[0019] Specifically, after waste lithium batteries are crushed, a mixture containing electrolyte and solids is obtained. This mixture is then vacuum-dried (<120℃) to vaporize the low-boiling-point electrolyte, achieving primary separation between the electrolyte and solids. The dried solids undergo sieving, grinding, air separation, and magnetic separation to separate and recycle black powder, copper powder, aluminum powder, steel casing, and plastics (diaphragm, outer sheath, insulating gaskets). This yields black powder with a low aluminum content. The obtained black powder is then subjected to secondary drying at 250~350℃ to remove high-boiling-point carbonate organic matter; the volatilized organic gases are mixed with low-temperature evaporated gases. The resulting electrolyte organic vapors are cooled, causing the organic matter to recondense into liquid organic matter, thus achieving electrolyte recovery.

[0020] Please see Figure 2 Secondly, the waste gas treatment process for the low-temperature dismantling of waste lithium batteries to prepare high-purity black powder, used in the method for preparing high-purity black powder from low-temperature dismantling of waste lithium batteries as described in the first aspect, includes the following steps: S101 Grade 1 detergent uses water. Water-soluble organic matter is absorbed by the water. Phosphorus pentafluoride decomposes into hydrogen fluoride and phosphoric acid when it comes into contact with water. The absorption of phosphoric acid leads to a decrease in pH, which inhibits the absorption of hydrogen fluoride. S102 secondary stage uses aluminum sulfate solution to absorb hydrogen fluoride, forming a fluorine-aluminum mixed solution with strong complexing ability, which deeply removes fluorides from the waste gas; S103 adds the organic waste gas after the aforementioned fluorine and phosphorus removal to a thermal oxidation incinerator for incineration to remove organic matter, thereby obtaining purified high-temperature flue gas; S104 Adds calcium salt to the absorbent obtained from the first-stage washing to neutralize phosphorus and produce calcium phosphate, which is then separated from the solution to obtain organic waste liquid; S105 The organic waste liquid obtained after phosphorus removal is subjected to indirect heat exchange with the high-temperature flue gas obtained from the thermal oxidation incinerator, so that the organic matter in the solution is re-evaporated into organic waste gas and returned to the thermal oxidation incinerator for high-temperature incineration removal. The solution from which S106 removes organic matter is returned to the primary washing stage for recycling. The solution obtained from the aforementioned secondary absorption in S107 is used to produce aluminum fluoride or cryolite, thereby realizing the recovery of fluorine resources.

[0021] Specifically, in step (1), the primary washing solution uses water, and water-soluble organic matter (lipids, alcohols) is absorbed by the water. Phosphorus pentafluoride decomposes into hydrogen fluoride and phosphoric acid upon contact with water. Phosphoric acid is absorbed, the pH decreases, and the absorption of hydrogen fluoride is inhibited. In step (2), the secondary process uses aluminum sulfate solution to absorb hydrogen fluoride, forming a fluorine-aluminum mixed solution with strong complexing ability. This deeply removes fluorides from the waste gas. In step (3), the organic waste gas after fluoride and phosphorus removal in step (2) is added to the TO furnace for incineration to remove organic matter, resulting in purified high-temperature flue gas. In step (4), calcium salt is added to the absorbent obtained in step (1) to neutralize phosphorus, producing calcium phosphate, which is separated from the solution to obtain organic waste liquid. In step (5), the organic waste liquid obtained in step (4) after phosphorus removal is exchanged with the high-temperature flue gas obtained in step (3) through a wall-type heat exchange, causing the organic matter in the solution to evaporate again into organic waste gas, which is then returned to step (3) for high-temperature incineration removal. Step (6): The solution from which organic matter has been removed is returned to step (1) for recycling. Step (7): The solution obtained in step (2) is made into aluminum fluoride or cryolite to realize the recovery of fluorine resources.

[0022] Beneficial effects: 1. Through distribution processing, the separation of aluminum and organic matter from black powder was achieved, resulting in high-purity battery black powder.

[0023] 2. Achieved efficient and resource-efficient waste gas purification: (1) Under low temperature conditions, fluorine and phosphorus are preferentially removed, but strong bases cannot be used to avoid the competitive reaction of hydroxide ions with carbonates and carbon dioxide, which would reduce the removal efficiency of hydrogen fluoride.

[0024] (2) Low-temperature priority removal of fluorine and phosphorus can prevent corrosion of equipment related to subsequent organic matter TO combustion and heat exchange processes.

[0025] (3) The first stage uses water washing to achieve four objectives: absorption of water-soluble organic matter, decomposition of phosphorus pentafluoride, absorption of phosphoric acid (leading to a decrease in pH), and inhibition of hydrogen fluoride absorption by pH reduction. Moreover, the absence of aluminum ions prevents the formation of aluminum phosphate precipitate, allowing the use of packed towers with better gas-liquid contact and resulting in better reaction performance.

[0026] (4) The secondary absorption is performed using aluminum salt solution to obtain a fluorine-aluminum complex. Good absorption can be achieved even under acidic conditions, and the influence of carbon dioxide on the absorption process does not need to be considered. The fluorine-aluminum complex is in a dissolved state and no solid is formed, so a packed tower with better gas-liquid contact can be used, resulting in a better reaction effect.

[0027] (5) The fluorine-aluminum complex solution obtained from absorption can be further processed into cryolite, realizing the resource recovery of highly toxic fluorine elements and avoiding environmental risks.

[0028] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries, characterized in that, Includes the following steps: After waste lithium batteries are crushed, a mixture containing electrolyte and solids is obtained. The mixture is then dried under vacuum to vaporize the low-boiling-point electrolyte carbonate organic matter, thus achieving primary separation of the electrolyte and solid materials. A dried solid material is subjected to screening, grinding, air separation, and magnetic separation processes to separate and recover black powder, copper powder, aluminum powder, steel shell, and plastic, resulting in black powder with low aluminum content. The black powder is dried twice at a temperature of 250-350℃ to remove high-boiling-point carbonate organic matter, and the volatile organic gases are mixed with low-temperature evaporated gases. The organic vapor in the electrolyte is cooled down, causing the organic matter to re-condense into liquid organic matter, thus realizing the recovery of organic matter in the electrolyte.

2. The method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries as described in claim 1, characterized in that, The vacuum drying temperature is <120℃. Low-temperature drying avoids embrittlement of the aluminum foil, maintains its toughness, and makes it less likely to break into powder with the same particle size as the black powder during subsequent grinding, thereby achieving effective separation of aluminum and black powder.

3. The method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries as described in claim 2, characterized in that, The obtained black powder is dried a second time at a temperature of 250-350℃ to remove high-boiling-point carbonate organic matter and further reduce the amount of residual organic matter in the black powder.

4. The method for preparing high-purity black powder by low-temperature dismantling of waste lithium batteries as described in claim 3, characterized in that, The low-boiling-point and high-boiling-point organic matter is removed separately by step-by-step drying. First, vacuum drying at <120℃ is used to remove the low-boiling-point electrolyte, and then secondary drying at 250-350℃ is used to remove the high-boiling-point carbonate organic matter, thus avoiding the problem of aluminum foil pulverization caused by using a single high-temperature drying.

5. A waste gas treatment process for the preparation of high-purity black powder from the low-temperature dismantling of waste lithium batteries, used in the method for preparing high-purity black powder from the low-temperature dismantling of waste lithium batteries as described in any one of claims 1-4, characterized in that, Includes the following steps: First-grade detergent uses water, and water-soluble organic matter is absorbed by the water. Phosphorus pentafluoride decomposes into hydrogen fluoride and phosphoric acid when it comes into contact with water. The absorption of phosphoric acid leads to a decrease in pH, which inhibits the absorption of hydrogen fluoride. The secondary stage uses aluminum sulfate solution to absorb hydrogen fluoride, forming a fluorine-aluminum mixed solution with strong complexing ability, which deeply removes fluorides from the waste gas; The organic waste gas after the aforementioned fluorine and phosphorus removal is added to a thermal oxidation incinerator for incineration to remove organic matter, resulting in purified high-temperature flue gas. The absorbent obtained from the first-stage washing process is mixed with calcium salt to neutralize phosphorus and produce calcium phosphate, which is then separated from the solution to obtain organic waste liquid. The organic waste liquid obtained above after phosphorus removal is subjected to indirect heat exchange with the high-temperature flue gas obtained from the thermal oxidation incinerator, so that the organic matter in the solution is re-evaporated into organic waste gas and returned to the thermal oxidation incinerator for high-temperature incineration removal. The solution used to remove organic matter is returned to the primary washing stage for recycling. The solution obtained from the aforementioned secondary absorption is processed into aluminum fluoride or cryolite to achieve the recovery of fluorine resources.

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