Treatment process based on evaporation mother liquor produced in waste battery recycling process

Abstract

This disclosure provides a treatment process for the mother liquor generated during the recycling of waste batteries. The process includes the following steps: pyrolysis of the mother liquor to obtain a mixture; vibration screening of the mixture to remove organic carbonized ash; dissolution and conditioning of the vibratory-screened mixture to obtain a mixed solution; freeze-crystallization of the mixed solution to obtain sodium sulfate and a post-freeze liquid; evaporation and concentration of the post-freeze liquid to obtain sodium chloride and a mixed salt solution; and drying of the mixed salt solution to obtain mixed salts. This process effectively removes organic matter from the mother liquor and maximizes the recovery of salt resources, while also enabling the separate recovery of sodium salts.

Description

Technical Field

[0001] This disclosure relates to the technical field of waste battery recycling, and in particular to a treatment process based on the evaporation mother liquor generated during the waste battery recycling process. Background Technology

[0002] In the battery recycling process, waste batteries are pre-treated to obtain battery powder, which then enters a wet integrated recycling system. The recycling process of the wet integrated recycling system is as follows: the primary battery powder is acid-leached to obtain a complex leachate, which is then subjected to staged removal of impurity metals to obtain a valuable metal solution. The valuable metal solution is then subjected to solvent extraction for deep purification and enrichment to recover valuable metals. The mother liquor after extraction is then evaporated and concentrated to reduce its volume and increase the concentration of impurity salts in the mother liquor, making it easier to recover the impurity salts. However, this recycling method inevitably introduces organic extractants into the evaporated mother liquor.

[0003] For example, the battery recycling process of related technologies uses activated carbon to remove organic matter from the mother liquor. However, due to the limited adsorption effect of activated carbon, organic solvents remain in the mother liquor. At the same time, the mother liquor contains a large amount of sodium salt, making it unsuitable for direct discharge. If the mother liquor is directly evaporated, it will not only consume a lot of energy, but the evaporated salts will also contain extractants, requiring the salts to be disposed of, thus wasting salt resources.

[0004] Therefore, how to effectively remove organic matter from the evaporation mother liquor while maximizing the recovery of salt resources is a major problem that urgently needs to be solved. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a treatment process for evaporation mother liquor generated during waste battery recycling that can effectively remove organic matter from the evaporation mother liquor while maximizing the recovery of salt resources.

[0006] The purpose of this disclosure is achieved through the following technical solution:

[0007] A treatment process for the mother liquor generated during the recycling of waste batteries includes the following steps:

[0008] The mother liquor from the evaporation is pyrolyzed to obtain a mixture.

[0009] The mixture is subjected to vibration screening to remove organic carbonized ash from the mixture;

[0010] The mixture after vibration screening is dissolved and adjusted to obtain a mixed solution;

[0011] The mixed solution is subjected to freeze crystallization to obtain sodium sulfate and the post-freeze solution;

[0012] The frozen liquid is then evaporated and concentrated to obtain a sodium chloride and miscellaneous salt solution;

[0013] The mixed salt solution is dried to obtain mixed salt.

[0014] In one embodiment, prior to the step of pyrolyzing the mother liquor, the treatment process further includes:

[0015] The mother liquor is subjected to extraction treatment to recover residual lithium ions.

[0016] In one embodiment, the step of pyrolyzing the mother liquor includes:

[0017] The mother liquor from the evaporation is pre-carbonized to obtain a solid salt mixture;

[0018] The solid salt mixture is subjected to carbonization treatment to obtain the mixture material.

[0019] In one embodiment, the operation of dissolving and adjusting the mixture after vibration screening includes:

[0020] The mixture after vibration screening is stirred and dissolved to obtain the mixed solution;

[0021] The pH of the mixed solution was adjusted.

[0022] In one embodiment, after the step of dissolving and adjusting the mixture after vibration screening, and before the step of freezing and crystallizing the mixture solution, the processing further includes:

[0023] The mixed solution is subjected to filtration and adsorption treatment to remove residual organic matter in the mixed solution.

[0024] In one embodiment, the step of performing a freeze crystallization treatment on the mixed solution after filtration and adsorption includes:

[0025] The mixed solution after filtration and adsorption is subjected to cooling separation treatment to obtain sodium sulfate slurry and the frozen liquid, respectively.

[0026] The sodium sulfate slurry is subjected to a first pressure filtration and drying treatment to obtain the frozen filtrate and the sodium sulfate salt, respectively.

[0027] The frozen liquid and the frozen filtrate are then transported to the evaporation and concentration process.

[0028] In one embodiment, the step of evaporating and concentrating the frozen liquid includes:

[0029] The frozen liquid is evaporated to obtain an evaporated liquid;

[0030] The evaporated liquid is subjected to thickening and separation treatment to obtain the sodium chloride slurry and the mixed salt solution, respectively.

[0031] The sodium chloride slurry is subjected to a second pressure filtration and drying treatment to obtain the sodium chloride salt and the evaporated filtrate, respectively.

[0032] The mixed salt solution and the evaporated filtrate are then conveyed to the drying process step.

[0033] In one embodiment, prior to the step of evaporating and concentrating the frozen liquid, the step of evaporating and concentrating the frozen liquid further includes:

[0034] The concentration of sodium chloride in the frozen liquid is detected to be greater than or equal to a preset sodium chloride concentration value; if so, the frozen liquid is then subjected to evaporation and concentration treatment.

[0035] Otherwise, the frozen liquid is reused in the dissolution and adjustment process.

[0036] In one embodiment, after the step of evaporating the frozen liquid and before the step of thickening and separating the evaporated liquid, the processing further includes:

[0037] The mass percentage of sodium chloride in the frozen liquid is checked to see if it is greater than or equal to a preset mass percentage value; if so, the evaporation process is stopped.

[0038] In one embodiment, the solid-liquid mass ratio of the mixed solution after dissolution and adjustment treatment is 0.55:1 to 0.6:1.

[0039] Compared with the prior art, this disclosure has at least the following advantages:

[0040] 1. By pyrolyzing the mother liquor, some volatile organic compounds and water can be evaporated and removed as pyrolysis tail gas. On the other hand, the CO and CH bonds in another part of the organic matter can be broken, releasing volatile components and being discharged with the pyrolysis tail gas, thus enriching carbon in the mixture, that is, the organic matter is transformed into organic carbonized ash.

[0041] 2. By utilizing the density difference between organic carbonized ash and salt, the organic carbonized ash is removed during the vibration screening process of the mixture, thus effectively removing organic matter from the evaporation mother liquor.

[0042] 3. After dissolving and adjusting the mixture to form a mixed solution, the mixed solution is then subjected to freeze crystallization. During the freezing process, the solubility of sodium sulfate decreases, allowing for the recovery of sodium sulfate salt. The frozen liquid is then evaporated and concentrated, during which the solubility of sodium chloride decreases, allowing for the recovery of sodium chloride salt. Finally, the mixed salt solution is dried to recover other mixed salts. In this way, the different solubilities of sodium sulfate and sodium chloride salt are used to recover sodium sulfate and sodium chloride salt separately. Both sodium sulfate and sodium chloride salt are recycled back to the front-end battery manufacturing process. This maximizes the recovery of salt resources in the mother liquor and also achieves the classified recovery of sodium salt. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart of the treatment process for the mother liquor generated during the recycling of waste batteries;

[0045] Figure 2 for Figure 1 The flowchart of step S90 in the processing technology shown;

[0046] Figure 3 for Figure 1 The flowchart of step S100 in the processing technology shown;

[0047] Figure 4 for Figure 1 The flowchart of step S300 in the processing technology shown;

[0048] Figure 5 for Figure 4 The flowchart of step S304 in the processing technology shown.

[0049] Figure 6 for Figure 1 The flowchart of step S301 in the processing technology shown;

[0050] Figure 7 for Figure 1 The flowchart of step S400 in the processing technology shown.

[0051] Figure 8 for Figure 1 The flowchart of step S500 in the processing technology shown.

[0052] Figure 9This is a flowchart of the treatment process for the mother liquor generated during the recycling of waste batteries. Detailed Implementation

[0053] To facilitate understanding of this disclosure, a more complete description will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0054] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0056] Please see Figure 1 To better understand the treatment process of the evaporation mother liquor generated during the recycling of waste batteries as disclosed in this disclosure, the following further explanation of the treatment process of the evaporation mother liquor generated during the recycling of waste batteries is provided:

[0057] One embodiment of the treatment process for the mother liquor generated during the recycling of waste batteries includes some or all of the following steps:

[0058] S100 is used to pyrolyze the mother liquor to obtain a mixture.

[0059] In this embodiment, by pyrolyzing the mother liquor, the water and some volatile organic compounds in the mother liquor can be discharged as pyrolysis tail gas. At the same time, the CO and CH bonds in another part of the organic matter are broken, releasing volatile components (such as carbon dioxide and water vapor), which enriches the carbon in the mixture, that is, the organic matter is converted into organic carbonized ash, while the volatile components are discharged with the pyrolysis tail gas. In this way, some organic matter can be removed in the pyrolysis treatment, thus improving the treatment effect of organic matter.

[0060] S200, the mixture is subjected to vibration screening to remove organic carbonized ash. In this embodiment, the density difference between the organic carbonized ash and salt in the mixture is utilized to screen the mixture using a vibrating screen, thus removing the organic carbonized ash and improving the treatment effect of organic matter. Furthermore, in related technologies, the use of activated carbon to remove organic matter from the mother liquor generates a large amount of activated carbon that adsorbs organic matter. Because activated carbon adsorbs a large amount of organic matter, it may become unrenewable or have poor regeneration effects, requiring strict disposal according to hazardous waste requirements, such as solidification or landfill. This results in significant resource loss and places a heavy burden on the environment. In this embodiment, the mixture obtained after pyrolysis is subjected to vibration screening to remove the organic carbonized ash. Therefore, organic matter in the evaporation mother liquor can be effectively removed without the need for activated carbon adsorption, avoiding activated carbon resource loss and environmental pollution, making the entire treatment process more environmentally friendly.

[0061] Furthermore, in one embodiment, the eccentric shaft of the vibrating screen rotates at a speed of 730 r / min to 1000 r / min, the amplitude of the vibrating screen is 6 mm to 8 mm, and the screen surface inclination angle is 20 degrees. Further, in this embodiment, the eccentric shaft of the vibrating screen rotates at 800 r / min, and the amplitude of the vibrating screen is 7 mm. Under these vibration conditions, the removal of organic carbonized ash can be maximized.

[0062] S300 performs a dissolution and adjustment process on the mixture after vibration screening to obtain a mixed solution.

[0063] In this embodiment, the mixture after vibration screening is dissolved to form a mixed solution, and the sodium sulfate in the mixed solution is saturated by controlling the solid-liquid mass ratio of the mixed solution, so that the sodium sulfate can be precipitated in the subsequent process.

[0064] Furthermore, in one embodiment, the solid-liquid mass ratio of the mixed solution after dissolution and conditioning is 0.55:1 to 0.6:1. It is understood that controlling the solid-liquid ratio of the mixed solution after dissolution and conditioning between 0.55:1 and 0.6:1 ensures that the sodium sulfate in the mixed solution is saturated, maximizing the recovery of sodium sulfate salt. The sodium sulfate salt can then be recycled back into the battery manufacturing process, achieving the recycling and reuse of salt resources.

[0065] S400 is used to freeze-crystallize the mixed solution to obtain sodium sulfate and the frozen solution.

[0066] In this embodiment, since sodium sulfate, sodium chloride, and other miscellaneous salts have different solubilities, and sodium sulfate has a lower solubility in a freezing environment, the mixed solution is frozen to precipitate sodium sulfate at -1℃ to 1℃ to form a crystal slurry. At this time, sodium chloride and other miscellaneous salts will not precipitate. This can achieve the purification of sodium sulfate to maximize the recovery of sodium sulfate salt. Moreover, the sodium sulfate salt can be recycled back to the front-end battery manufacturing process, thereby realizing the reuse of salt resources.

[0067] S500 performs evaporation and concentration on the frozen liquid to obtain sodium chloride and other salt solutions.

[0068] In this embodiment, sodium chloride is refined by evaporating and concentrating the frozen liquid, while preventing the precipitation of impurities. This maximizes the recovery of sodium chloride, which can then be recycled back to the front-end battery manufacturing process, thus achieving the reuse of salt resources.

[0069] S600 is used to dry the mixed salt solution to obtain mixed salt.

[0070] In this embodiment, the mixed salt solution is dried by a drum dryer to further evaporate and dehydrate the mixed salt solution in order to recover other mixed salts. Moreover, the organic content of the mixed salt is low, so there is no need to dispose of it as waste. This allows the mixed salt to be sold, avoiding the waste of mixed salt resources and making the mixed salt resources valuable.

[0071] Furthermore, in one embodiment, the drying temperature of the drum dryer is 130°C to 160°C, the rotation speed of the drum is 4 rpm to 5 rpm, and the steam pressure of the drum dryer is 0 to 0.5 MPa.

[0072] Please see Figure 1 In one embodiment, prior to step S100, which involves pyrolyzing the mother liquor, the process further includes the following steps:

[0073] S90, the mother liquor is extracted to recover residual lithium ions. In this embodiment, since a small portion of lithium ions remains unrecovered during the upstream valuable metal extraction process, extracting the mother liquor improves the treatment efficiency and maximizes the recovery of resources from the mother liquor.

[0074] Further, please refer to Figure 2 Step S90, which involves extracting the mother liquor from the evaporated liquor, includes:

[0075] S91, the evaporated mother liquor is transferred to the extraction tank;

[0076] S92, add extractant and diluent to the extraction tank to perform lithium ion extraction on the evaporated mother liquor, so that an upper extract and a lower evaporated mother liquor are formed in the extraction tank.

[0077] It should be noted that the extractant is model HBL121, which is specifically designed for extracting lithium ions, and the diluent is sulfonated kerosene. The extractant accounts for 28% of the total mass of the extractant and diluent mixture, and the diluent accounts for 72% of the total mass of the extractant and diluent mixture. This allows the lithium ions in the mother liquor to be adsorbed into the extractant, while the lower layer of mother liquor is transported to the pyrolysis process, maximizing the recovery of resources from the mother liquor.

[0078] It should be noted that the extractant is HBL121 extractant from Hunan Hongbang New Materials Co., Ltd.

[0079] Further, please refer to Figure 2 After step S92, which involves adding extractant and diluent to the extraction tank for lithium-ion extraction of the evaporated mother liquor, step S90 further includes the following step:

[0080] S93, acid is added to the upper extract to form an upper extractant and a lower eluent;

[0081] S94, alkali saponification of the upper extractant;

[0082] S95, the upper extractant is returned to the extraction tank for recycling.

[0083] It should be noted that by adding 2 mol / L sulfuric acid to the upper extract to perform a leaching reaction, water-soluble lithium sulfate is formed, allowing lithium ions to escape from the upper extract to the lower eluent, maximizing the resource recovery of the mother liquor. Furthermore, adding sodium hydroxide solution to the upper extract for a saponification reaction not only neutralizes the sulfuric acid in the upper extract but also saponifies the upper extractant, reactivating it and allowing it to be recycled back into the extraction tank for continued use, further reducing the treatment cost of the mother liquor.

[0084] Please see Figure 3 In one embodiment, step S100 of pyrolyzing the mother liquor includes:

[0085] S102, the mother liquor is pre-carbonized to obtain a solid salt mixture. In this embodiment, the mother liquor is pre-carbonized in a pre-carbonization reactor. Specifically, the mother liquor is injected into the pre-carbonization reactor, and the mother liquor flows from the upper furnace to the lower furnace in a spray state. Further, the temperature of the upper furnace is controlled at 400℃~500℃, and the temperature of the lower furnace is controlled at 300℃~350℃. Further, the liquid flow rate is 4L / min; further, the pre-carbonization time is 60min.

[0086] S104, carbonizes the solid salt mixture to obtain a mixture.

[0087] It should be noted that the mother liquor is pre-carbonized in a pre-carbonization reactor. Specifically, the mother liquor is injected into the pre-carbonization reactor, entering the furnace from the top in a spray state. The liquid flow rate is 4 L / min, the upper furnace temperature is controlled at 400℃~500℃, and the lower furnace temperature is controlled at 300℃~350℃. At the same time, the pyrolysis time is controlled at 60 min. Under this temperature and time control, the pre-carbonization solidifies the salt in the mother liquor and pyrolyzes and carbonizes some organic matter in an oxygen atmosphere. Meanwhile, the volatile organic compounds will enter the exhaust gas treatment system through the exhaust gas discharge end of the pre-carbonization reactor. Furthermore, the solid salt mixture is carbonized in a solid carbonization reactor. Specifically, the solid salt mixture after pre-carbonization contains organic carbon substances. Immediately after pre-carbonization, the dried solid salt mixture is fed into the solid carbonization reactor. The pyrolysis carbonization temperature is controlled at 750℃~850℃, with nitrogen as a protective gas. The pyrolysis time is controlled at 20min~30min, allowing the organic carbon to pyrolyze into organic carbonized ash and moisture in an oxygen-free environment. The moisture enters the tail gas treatment system along with the tail gas from the solidification carbonization reactor, thus effectively removing organic matter from the mother liquor.

[0088] Furthermore, the pyrolysis exhaust gas enters the spray tower of the exhaust gas treatment system, where harmful substances in the exhaust gas are washed away by the spray water. The exhaust gas, after passing through the spray tower, can be discharged once it meets the emission standards. Going further, the spray water is transported to a biochemical system for further treatment, ensuring that it meets the emission standards before being released, thus guaranteeing the environmental friendliness of the entire treatment process.

[0089] Please see Figure 4 In one embodiment, step S300 of dissolving and adjusting the mixture after vibration screening includes:

[0090] S302, the mixture after vibration screening is stirred and dissolved to obtain a mixed solution; in this embodiment, the mixture after vibration screening is stirred and dissolved in pure water in a remelting tank. Furthermore, the stirring time for the stirring and dissolving operation is 30 min to 60 min to ensure complete dissolution of the mixed solution.

[0091] S304 is used to adjust the pH of the mixed solution.

[0092] Understandably, the mixture after vibration screening is dissolved in pure water in a remelting tank by stirring. Then, the pH of the mixed solution is adjusted to react the carbonate and bicarbonate ions in the mixed solution, so that they form carbon dioxide and water, thereby further concentrating the mixed solution.

[0093] Further, please refer to Figure 5 Step S304, which involves adjusting the pH of the mixed solution, includes:

[0094] S3042, sulfuric acid is added to the mixed solution to adjust the pH value of the mixed solution to acidic conditions, which can react with carbonate ions and bicarbonate ions in the mixed solution to form carbon dioxide and water, further concentrating the mixed solution and increasing the concentration of sodium sulfate and sodium chloride, which facilitates subsequent salt precipitation; in this embodiment, 25% to 30% sulfuric acid is added to the mixed solution.

[0095] S3044: Add sodium hydroxide solution to the mixed solution to adjust the pH value of the mixed solution to neutral conditions, so that the solubility of sodium salt and other miscellaneous salts is at a high level, and the premature precipitation of salts is avoided.

[0096] Furthermore, the pH of the mixed solution is adjusted while the temperature is controlled at 40℃–45℃. Specifically, 30% sulfuric acid is added to the mixed solution to adjust the pH to 3, and the temperature is controlled at 40℃–45℃. This reacts the carbonate and bicarbonate ions in the mixed solution to form carbon dioxide and water, further concentrating the mixed solution and increasing the concentration of sodium sulfate and sodium chloride, which facilitates subsequent salt precipitation. Then, sodium hydroxide solution is added to the mixed solution to bring the pH back down to 7, while the temperature is controlled at 40℃–45℃. This ensures that the solubility of sodium salt and other miscellaneous salts is at a high level, preventing premature salt precipitation.

[0097] Please see Figure 1 In one embodiment, after the operation step S300 of dissolving and adjusting the mixture after vibration screening, and before the operation step S400 of freezing and crystallizing the mixture solution, the processing technology further includes the following operation steps:

[0098] S301, the mixed solution is subjected to filtration and adsorption treatment to remove residual organic matter in the mixed solution.

[0099] It is understandable that after pyrolysis, there may be a small amount of recalcitrant organic matter remaining, as well as some organic carbonized ash remaining in the mixed solution. By filtering and adsorbing the mixed solution, the recalcitrant organic matter and organic carbonized ash can be removed, further improving the treatment effect of organic matter in the evaporation mother liquor, thereby effectively improving the quality of recovered miscellaneous salts.

[0100] Further, please refer to Figure 6 In one embodiment, step S301 of filtering and adsorbing the mixed solution after dissolution and adjustment treatment includes:

[0101] S3012, Filter the mixed solution after dissolution and adjustment treatment to remove residual organic carbonized ash from the mixed solution;

[0102] S3014 uses an oil-removing resin to adsorb and treat the mixed solution to remove residual organic matter in the mixed solution.

[0103] It should be noted that by removing the residual organic carbonized ash in the mixed solution after dissolution and conditioning through filtration, and then adsorbing and removing the residual organic matter in the mixed solution through a large-pore degreasing resin, the treatment effect of organic matter in the evaporation mother liquor is further improved.

[0104] It should be noted that the filtered organic carbonized ash should be disposed of as hazardous waste, and the pore size of the degreasing resin is 200nm~300nm.

[0105] Furthermore, after the degreasing resin becomes saturated, it needs to be desorbed by adding liquid alkali. The desorbed solution is then sent to a biological treatment system for processing, ensuring that it meets the standards before being discharged. Additionally, after a period of use, the degreasing resin requires resin regeneration treatment. Through acid and alkali treatment, the degreasing resin can be regenerated and recycled. The regenerated solution is also sent to a biological treatment system for processing, ensuring that it meets the standards before being discharged.

[0106] Please see Figure 7 In one embodiment, step S400 of freezing and crystallizing the mixed solution after filtration and adsorption treatment includes:

[0107] S402 involves cooling and separating the mixed solution after filtration and adsorption to obtain sodium sulfate slurry and frozen liquid, respectively.

[0108] In this embodiment, the mixed solution is cooled and separated using a cryo-crystallization apparatus. Furthermore, the temperature of the cryo-crystallization apparatus is -1°C to 1°C.

[0109] S404, the sodium sulfate slurry is subjected to a first pressure filtration and drying treatment to obtain a frozen filtrate and sodium sulfate salt, respectively.

[0110] In this embodiment, a horizontal screw compressor is used to perform solid-liquid separation treatment on sodium sulfate slurry to obtain sodium sulfate crystals and cryogenic filtrate. The sodium sulfate crystals are then dried using a fluidized bed to recover sodium sulfate salt. This maximizes the recovery of sodium sulfate salt and realizes the classified recovery of sodium salt and the reuse of salt resources.

[0111] S406, the frozen liquid and frozen filtrate are transported to the evaporation and concentration process.

[0112] In this embodiment, the frozen liquid and the frozen filtrate are first transported to a frozen mother liquor tank for collection and storage, and then the frozen liquid is transported to the evaporation and concentration process through the frozen mother liquor tank.

[0113] Please see Figure 8 In one embodiment, step S500 of evaporating and concentrating the frozen liquid includes:

[0114] S502, the frozen liquid is evaporated to obtain the evaporated liquid.

[0115] In this embodiment, the frozen liquid is evaporated using an evaporation MVR device to remove most of the water, forming an evaporated liquid. This increases the sodium chloride concentration in the evaporated liquid, bringing it to a sodium chloride saturation state, which facilitates the precipitation of sodium chloride.

[0116] It should be noted that the evaporation MVR device is a mechanical vapor recompression evaporator from Hebei Leheng Energy-Saving Equipment Co., Ltd.

[0117] S504, the evaporated liquid is thickened and separated to obtain sodium chloride slurry and miscellaneous salt solution respectively.

[0118] In this embodiment, the evaporated liquid is thickened and separated by a thickener, so that sodium chloride precipitates out of the evaporated liquid in the thickener, and is separated into sodium chloride slurry and miscellaneous salt solution.

[0119] S506, the sodium chloride slurry is subjected to a second pressure filtration and drying treatment to obtain sodium chloride salt and evaporation filtrate, respectively.

[0120] In this embodiment, a horizontal screw compressor is used to perform solid-liquid separation treatment on sodium chloride slurry to obtain sodium chloride crystals and evaporation filtrate. The sodium chloride crystals are then dried using a fluidized bed to recover sodium chloride salt. This maximizes the recovery of sodium chloride salt and realizes the classified recovery of sodium salt and the reuse of salt resources.

[0121] S508, the mixed salt solution and the evaporated filtrate are conveyed to the drying process step. In this embodiment, the mixed salt solution and the evaporated filtrate are then conveyed to the next drying process to recover the mixed salt.

[0122] In one embodiment, the hot air temperature of the fluidized bed is 100°C to 200°C, and the hot air pressure of the fluidized bed is -50Pa to -200Pa.

[0123] In one embodiment, the step of evaporating and concentrating the frozen liquid before the step of evaporating the frozen liquid further includes:

[0124] Check whether the sodium chloride concentration of the frozen liquid is greater than or equal to the preset sodium chloride concentration value; if so, the frozen liquid is then evaporated and concentrated.

[0125] Otherwise, the frozen liquid will be reused in the dissolution and adjustment process.

[0126] It should be noted that when the sodium chloride concentration of the post-freezing liquid in the mother liquor tank is greater than or equal to the preset sodium chloride concentration value, the energy consumption of the evaporation MVR unit can be reduced, while achieving a better concentration effect. When the sodium chloride concentration of the post-freezing liquid in the mother liquor tank is less than the preset sodium chloride concentration value, it is recycled to the dissolution and conditioning step as a solvent to dissolve the mixed materials, saving the input of pure water and reducing the treatment cost of the evaporation mother liquor.

[0127] Furthermore, in one embodiment, the preset sodium chloride concentration is 250 g / L to 350 g / L. In this embodiment, the preset sodium chloride concentration is 300 g / L.

[0128] Furthermore, the frozen liquid is reused in the dissolution and conditioning process; specifically, the frozen liquid is reused in the remelting tank. Further, before flowing back to the remelting tank, the frozen liquid needs to undergo heat exchange treatment via a heat exchanger to prevent the low-temperature frozen liquid from failing to completely dissolve the mixture and to prevent premature precipitation of sodium sulfate in the remelting tank.

[0129] In one embodiment, after the step of evaporating the frozen liquid and before the step of thickening and separating the evaporated liquid, the processing further includes:

[0130] Check whether the mass percentage of sodium chloride in the frozen liquid is greater than or equal to the preset mass percentage value; if so, stop the evaporation process.

[0131] It should be noted that the preset mass percentage value is the mass percentage of sodium chloride when it is in a saturated state. When the sodium chloride in the evaporated liquid is saturated, the evaporated liquid is passed into a thickener to thicken it and cause sodium chloride to precipitate. According to the principle of gravity falling, sodium chloride forms a sodium chloride slurry at the bottom of the thickener. This can maximize the recovery of sodium chloride while reducing the energy consumed by evaporation, and further reduce the treatment cost of the mother liquor.

[0132] Furthermore, the mass percentage of sodium chloride in the frozen liquid is monitored in real time. In other words, the mass percentage of sodium chloride in the frozen liquid within the evaporation MVR device is displayed in real time, which can prevent over-evaporation, minimize evaporation energy consumption, and further reduce the treatment cost of the mother liquor.

[0133] Furthermore, in one embodiment, the preset mass percentage of sodium chloride in the frozen liquid is 30% to 40%; in this embodiment, the preset mass percentage of sodium chloride in the frozen liquid is 36%.

[0134] The following are examples, but it should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples are commercially available unless otherwise specified. Specific Implementation

[0136] Composition of the target evaporation mother liquor: Li + Sodium sulfate: 7-8 g / L, sodium sulfate: 200-240 g / L, sodium chloride: 25-30 g / L, sodium carbonate: 3-5 g / L, COD: 20-30 g / L.

[0137] The target evaporation mother liquor is treated using the processing technology disclosed herein, and the target evaporation mother liquor is processed in three batches.

[0138] The specific operating steps of the processing technology are as follows:

[0139] (1) Extraction: The mother liquor evaporated on the production line is put into the extraction tank for extraction of Li in the mother liquor. The extractant is HBL121 and the diluent is sulfonated kerosene (the mass of the extractant accounts for 28% of the total mass of the mixture of extractant and diluent, and the mass of the diluent accounts for 72% of the total mass of the mixture of extractant and diluent). After the extraction is completed, the mother liquor evaporated is put into the next process. The organic phase is added with 2 mol / L sulfuric acid solution for analysis. After analysis, it is saponified with sodium hydroxide solution. The extractant is HBL121 extractant from Hunan Hongbang New Materials Co., Ltd.

[0140] (2) Pre-carbonization: The mother liquor after lithium extraction is pumped into the pre-carbonization reactor. The mother liquor enters the furnace body from the top in a spray state with a liquid flow rate of 4L / min. The upper furnace temperature is controlled at 400℃~500℃ and the lower furnace temperature is controlled at 300℃~350℃. At the same time, the pyrolysis time is controlled at 60min. Pre-carbonization causes the salt solidified organic matter in the mother liquor to be pyrolyzed, dried and carbonized.

[0141] (3) Carbonization: After pre-carbonization, the dried solid salt mixture is immediately sent into the solid carbonization furnace. The pyrolysis carbonization temperature is controlled at 800℃, with nitrogen as the protective gas. At the same time, the pyrolysis time is controlled at 30min. The waste gas generated by pyrolysis enters the tail gas treatment system.

[0142] (4) Vibration screening: The carbonized mixture is separated from the salt by a vibrating screen. The eccentric shaft of the vibrating screen rotates at 800 r / min, the amplitude of the vibrating screen is 7 mm, and the screen surface inclination angle of the vibrating screen is 20 degrees. Organic carbonized ash is treated as hazardous waste.

[0143] (5) Dissolution and pH adjustment: The mixture is dissolved in pure water and frozen liquid, with the solid-liquid mass ratio controlled at 0.55:1 to 0.6:1. The stirring and dissolution time is 60 min. Then, 30% sulfuric acid is added to adjust the pH to 3 to remove carbonate ions in the mixed solution. The pH is then adjusted to 7 with sodium hydroxide, and the temperature is controlled at 45℃.

[0144] (5) Filtration: Filtration removes organic carbonized ash from the mixed solution.

[0145] (6) Adsorption: After filtration, the mixed solution is adsorbed with a large-pore oil removal resin to remove organic matter in the mixed solution. After adsorption saturation, liquid alkali is used for desorption, and the desorbed solution is collected and sent into the biochemical system.

[0146] (7) Freeze-crystallization: The mixed solution after adsorption is transported to the freeze-crystallization device, and the temperature is lowered to 0°C by the freeze-crystallization device to obtain sodium sulfate crystal slurry. The solid is separated by a horizontal screw compressor. The compressed solid is sent to a fluid drying bed for drying. The frozen liquid and the frozen filtrate enter the freeze mother liquor tank. When the sodium chloride concentration is greater than 300 g / L, the frozen liquid enters the evaporation MVR device for evaporation and concentration. When the sodium chloride concentration is less than 300 g / L, the frozen liquid is returned to the re-dissolving tank to continue to dissolve sodium sulfate and enrich sodium chloride. The evaporation MVR device is a mechanical vapor recompression evaporator from Hebei Leheng Energy-saving Equipment Co., Ltd.

[0147] (8) Evaporation and concentration: The frozen liquid is evaporated and concentrated to increase the mass ratio of sodium chloride in the solution. When the mass ratio of sodium chloride in the frozen liquid is ≥36%, the concentration is stopped and the liquid enters the thickener. The bottom crystal slurry is filtered by a compressor, and the filtered solid is sent to a fluidized bed for drying.

[0148] (9) Fluidized bed drying: The compressed solid salts are sodium sulfate decahydrate and sodium chloride. The solid salts need to be dehydrated. The solid salts are transferred to a solid fluidized bed for drying. The hot air temperature is 150℃, the hot air pressure is -100pa, and the drying time is 40min, to obtain anhydrous sodium sulfate and anhydrous sodium chloride respectively.

[0149] (10) Drying in a drum dryer: The mixed salt solution and the evaporated filtrate are transported to the drum dryer. The mixed salt obtained by drying in the drum dryer is sold. The drying temperature of the drum dryer is 150℃, the drum speed is 4rpm, and the steam pressure is 0.3MPa.

[0150] Characterization data of the produced anhydrous sodium sulfate and sodium chloride are shown in Tables 1 and 2, where Table 1 shows the composition of the produced sodium sulfate and Table 2 shows the composition of the produced sodium chloride.

[0151] Table 1

[0152]

[0153]

[0154] Table 2

[0155]

[0156] It should be noted that whiteness (R475) refers to the degree of whiteness of a material's surface, expressed as a percentage of white content. Industrial sodium sulfate requires a whiteness of 82% or higher.

[0157] As shown in Tables 1 and 2, the sodium salt recovery process of the target evaporation mother liquor was carried out in three batches using the recovery process disclosed in this invention. The purity of the sodium chloride recovered from the three batches of water was above 97%, and the purity of the sodium sulfate recovered from the three batches of water was above 98%. Neither the sodium chloride nor the sodium sulfate recovered from the three batches of water contained organic matter, and the content of other impurities was also low. Moreover, the whiteness of the sodium sulfate recovered from the three batches of water was above 82%, which allows the sodium chloride and sodium sulfate recovered from the three batches of water to be directly transported to the front-end battery manufacturing process for use. This also shows that the processing process disclosed in this invention can effectively remove organic matter from the evaporation mother liquor, achieve fine classification and recovery of sodium salts, and maximize the recovery of salt resources in the evaporation mother liquor.

[0158] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A treatment process for the mother liquor generated during the recycling of waste batteries, characterized in that, Includes the following steps: The mother liquor is subjected to extraction treatment to recover residual lithium ions in the mother liquor; The mother liquor from the evaporation is subjected to pre-carbonization treatment to obtain a solid salt mixture; the solid salt mixture is then subjected to carbonization treatment to obtain a mixed material. The mixture is subjected to vibration screening to remove organic carbonized ash from the mixture; The mixture after vibration screening is subjected to dissolution and value adjustment treatment to obtain a dissolved and value-adjusted mixed solution, including: The mixture after vibration screening is stirred and dissolved to obtain a stirred and dissolved mixed solution; then sulfuric acid is added to the stirred and dissolved mixed solution to adjust the pH value to acidic conditions, and then sodium hydroxide solution is added to adjust the pH value of the mixed solution to neutral conditions. The mixed solution, with its pH adjusted to neutral, is filtered to remove residual organic carbonized ash. Then, an oil-removing resin is used to adsorb and remove residual organic matter from the mixed solution. The mixed solution was then subjected to freeze crystallization to obtain sodium sulfate and the frozen solution. The frozen liquid is then evaporated and concentrated to obtain a sodium chloride and miscellaneous salt solution; The mixed salt solution is dried to obtain mixed salt.

2. The treatment process for the evaporation mother liquor generated during the recycling of waste batteries according to claim 1, characterized in that, The step of performing freeze crystallization on the mixed solution includes: The mixed solution is subjected to a cooling separation process to obtain sodium sulfate slurry and the frozen liquid, respectively. The sodium sulfate slurry is subjected to a first pressure filtration and drying treatment to obtain a frozen filtrate and the sodium sulfate salt, respectively. The frozen liquid and the frozen filtrate are then transported to the evaporation and concentration process.

3. The treatment process for the evaporation mother liquor generated during the recycling of waste batteries according to claim 1, characterized in that, The steps of evaporating and concentrating the frozen liquid include: The frozen liquid is evaporated to obtain an evaporated liquid; The evaporated liquid is subjected to thickening and separation treatment to obtain sodium chloride slurry and the mixed salt solution, respectively. The sodium chloride slurry is subjected to a second pressure filtration and drying treatment to obtain the sodium chloride salt and the evaporated filtrate, respectively. The mixed salt solution and the evaporated filtrate are then conveyed to the drying process step.

4. The treatment process for the evaporation mother liquor generated during the recycling of waste batteries according to claim 3, characterized in that, Prior to the step of evaporating the frozen liquid, the step of evaporating and concentrating the frozen liquid further includes: The concentration of sodium chloride in the frozen liquid is detected to be greater than or equal to a preset sodium chloride concentration value; if so, the frozen liquid is subjected to evaporation and concentration treatment. Otherwise, the frozen liquid is reused in the dissolution and adjustment process.

5. The treatment process for the evaporation mother liquor generated during the recycling of waste batteries according to claim 3, characterized in that, After the step of evaporating the frozen liquid and before the step of thickening and separating the evaporated liquid, the processing technology further includes: The mass percentage of sodium chloride in the frozen liquid is checked to see if it is greater than or equal to a preset mass percentage value; if so, the evaporation process is stopped.

6. The treatment process for the evaporation mother liquor generated during the recycling of waste batteries according to claim 1, characterized in that, The solid-liquid mass ratio of the mixed solution after dissolution and adjustment treatment is 0.55:1 to 0.6:1.

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