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

Abstract

The invention provides a treatment process based on evaporation mother liquor generated in a waste battery recovery process, and the treatment process comprises the following steps: carrying out pyrolysis treatment on the evaporation mother liquor to obtain a mixed material; carrying out vibration screening treatment on the mixed material so as to remove organic carbonized ash in the mixed material; carrying out dissolution and value adjustment treatment on the mixed material subjected to vibration screening to obtain a mixed solution; performing freezing crystallization treatment on the mixed solution to obtain sodium sulfate salt and frozen liquid; performing evaporation and concentration treatment on the frozen liquid to obtain sodium chloride salt and a carnallite solution; and carrying out drying treatment on the carnallite solution to obtain carnallite. According to the treatment process, organic matters in the evaporation mother liquor can be effectively removed, salt resources in the evaporation mother liquor can be recovered to the greatest extent, and meanwhile, classified recovery of sodium salt is also realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of waste battery recycling, and in particular to a treatment process for evaporation mother liquor generated in the waste battery recycling process. Background Art

[0002] In the battery recycling process, the used batteries are pre-treated to obtain battery powder, which enters the wet comprehensive recycling system. The recycling process of the wet comprehensive recycling system is as follows: the original battery powder is acid-leached to obtain a complex leachate, and then the impurity metals are removed in stages to obtain a valuable metal solution. The valuable metal solution is then subjected to a solvent extraction deep purification and enrichment process to recover the valuable metals, and then the mother liquor after extraction is evaporated and concentrated to reduce the volume of the mother liquor, so that the concentration of impure salts in the mother liquor is increased, which is convenient for the recovery of impure salts. However, this recycling method inevitably mixes organic extractants into the evaporated mother liquor.

[0003] For example, the battery recycling process of the related technology uses activated carbon to remove organic matter from the mother liquor. Due to the limited adsorption effect of activated carbon, organic solvents still remain in the mother liquor. At the same time, the mother liquor contains a large amount of sodium salt, which makes the mother liquor unsuitable for direct discharge. If the mother liquor is directly evaporated, it will not only consume a lot of energy, but the evaporated impure salt will contain extractants, which will cause the impure salt to be scrapped, thereby causing a waste of salt resources.

[0004] Therefore, how to effectively remove organic matter from the evaporation mother liquor while recovering salt resources to the greatest extent is the main problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a treatment process for evaporation mother liquor generated during the recycling of waste batteries, which can effectively remove organic matter in the evaporation mother liquor while recovering salt resources to the greatest extent.

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

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

[0008] Performing pyrolysis treatment on the evaporated mother liquor to obtain a mixed material;

[0009] Performing vibration screening on the mixed material to remove organic carbonized ash in the mixed material;

[0010] Performing dissolution and value adjustment treatment on the mixed material after vibration screening to obtain a mixed solution;

[0011] The mixed solution is subjected to a freeze crystallization process to obtain a sodium sulfate salt and a frozen liquid;

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

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

[0014] In one embodiment, before the step of subjecting the evaporation mother liquor to pyrolysis, the treatment process further comprises:

[0015] The evaporation mother liquor is subjected to extraction treatment to recover the lithium ions remaining in the evaporation mother liquor.

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

[0017] performing a pre-carbonization treatment on the evaporated mother liquor to obtain a solid salt mixture;

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

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

[0020] Stirring and dissolving the mixed material after vibration screening to obtain the mixed solution;

[0021] The mixed solution is subjected to a pH adjustment treatment.

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

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

[0024] In one embodiment, the step of subjecting the mixed solution after the filtration and adsorption treatment to freeze crystallization treatment comprises:

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

[0026] Performing a first filter pressing and drying treatment on the sodium sulfate slurry to obtain the frozen filtrate and the sodium sulfate salt respectively;

[0027] The frozen liquid and the frozen filtrate are sent to an evaporation concentration treatment step.

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

[0029] performing an evaporation treatment on the frozen liquid to obtain an evaporated liquid;

[0030] Performing thickening and separation treatment on the evaporated liquid to obtain the sodium chloride slurry and the mixed salt solution respectively;

[0031] Performing a second filter pressing and drying treatment on the sodium chloride slurry to obtain the sodium chloride salt and the evaporated filtrate respectively;

[0032] The mixed salt solution and the evaporated filtrate are sent to a drying step.

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

[0034] Detecting whether the sodium chloride concentration of the frozen liquid is greater than or equal to a preset sodium chloride concentration value; if so, subjecting the frozen liquid to evaporation and concentration treatment;

[0035] Otherwise, the frozen liquid is recycled to the dissolution and adjustment step.

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

[0037] Detect whether the mass percentage of sodium chloride in the frozen liquid is greater than or equal to a preset mass percentage value; if so, stop the evaporation process.

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

[0039] Compared with the prior art, the present invention has at least the following advantages:

[0040] 1. By pyrolyzing the evaporation mother liquor, on the one hand, part of the volatile organic matter and water can be evaporated and formed into pyrolysis tail gas for removal; on the other hand, the CO bonds and CH bonds in another part of the organic matter can be broken, the volatile components are released and discharged with the pyrolysis tail gas, so that the carbon in the mixed material is enriched, that is, the organic matter is converted into organic carbonized ash;

[0041] 2. Taking advantage of the difference in density between organic carbonized ash and salt, the mixed material is vibrated and screened to remove the organic carbonized ash during the vibration process, which can effectively remove the organic matter in the evaporation mother liquor;

[0042] 3. The mixed material is dissolved and adjusted to form a mixed solution, and the mixed solution is then subjected to a freezing and crystallization treatment. During the freezing process, the solubility of sodium sulfate decreases to recover the sodium sulfate salt. The frozen liquid is then evaporated and concentrated. During the evaporation process, the solubility of sodium chloride decreases to recover the sodium chloride salt. Finally, the mixed salt solution is dried to recover other mixed salts. In this way, the sodium sulfate salt and the sodium chloride salt are recovered respectively by utilizing the different solubilities of the sodium sulfate salt and the sodium chloride salt. Both the sodium sulfate salt and the sodium chloride salt are returned to the front-end battery preparation process for recycling. In this way, the salt resources in the evaporation mother liquor can be recovered to the greatest extent, and the classified recovery of the sodium salt can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 The present invention is a flow chart of a treatment process of evaporation mother liquor generated in the process of recycling waste batteries;

[0045] Figure 2 for Figure 1 Flow chart of step S90 in the processing process shown;

[0046] Figure 3 for Figure 1 Flow chart of step S100 in the processing process shown;

[0047] Figure 4 for Figure 1 Flow chart of step S300 in the processing process shown;

[0048] Figure 5 for Figure 4 Flow chart of step S304 in the processing process shown;

[0049] Figure 6 for Figure 1 Flow chart of step S301 in the processing process shown;

[0050] Figure 7 for Figure 1 Flow chart of step S400 in the processing process shown;

[0051] Figure 8 for Figure 1 Flow chart of step S500 in the processing process shown;

[0052] Fig. 9The present invention is a flow chart of the treatment process of the evaporation mother liquor generated during the recycling process of waste batteries. DETAILED DESCRIPTION

[0053] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

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

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0056] See also Figure 1 In order to better understand the treatment process of the evaporation mother liquor generated in the waste battery recycling process disclosed in the present invention, the treatment process of the evaporation mother liquor generated in the waste battery recycling process is further explained below:

[0057] A treatment process for evaporation mother liquor generated during the recycling of waste batteries according to one embodiment includes some or all of the following steps:

[0058] S100, performing pyrolysis treatment on the evaporated mother liquor to obtain a mixed material.

[0059] In this embodiment, by subjecting the evaporation mother liquor to pyrolysis treatment, the water content and part of the volatile organic matter in the evaporation mother liquor can be discharged in the form of pyrolysis tail gas, while the CO bonds and CH bonds in another part of the organic matter are broken to release volatile components (such as carbon dioxide and water vapor), so that the carbon in the mixed material is enriched, that is, the organic matter is converted into organic carbonized ash, and the volatile components will be discharged with the pyrolysis tail gas. In this way, part of the organic matter can be removed in the pyrolysis treatment, thereby improving the treatment effect of the organic matter.

[0060] S200, vibrating and screening the mixed material to remove the organic carbonized ash in the mixed material. In this embodiment, the organic carbonized ash in the mixed material is screened by a vibrating screen due to the different densities between the organic carbonized ash and the salt, so that the organic carbonized ash can be removed, thereby improving the treatment effect of the organic matter. Furthermore, in the related art, the use of activated carbon to remove organic matter in the mother liquor will produce a large amount of activated carbon that adsorbs organic matter. Since the activated carbon adsorbs a large amount of organic matter, it will cause the activated carbon to be unable to regenerate or the regeneration effect is poor, so that the activated carbon needs to be scrapped and disposed of in strict accordance with the relevant requirements for hazardous wastes, that is, the waste activated carbon is solidified, landfilled, etc. as hazardous waste, which will cause a large amount of resource loss and a huge burden on the environment. In this embodiment, the mixed material obtained after pyrolysis is vibrated and screened to remove the organic carbonized ash in the mixed material. Therefore, the organic matter in the evaporation mother liquor can be effectively removed without the use of activated carbon adsorption, avoiding the loss of activated carbon resources and environmental pollution, making the entire treatment process more environmentally friendly.

[0061] Further, in one embodiment, the eccentric shaft speed of the vibrating screen is 730r / min to 1000r / min, the amplitude of the vibrating screen is 6mm to 8mm, and the screen surface inclination of the vibrating screen is 20 degrees. Further, in this embodiment, the eccentric shaft speed of the vibrating screen is 800r / min, and the amplitude of the vibrating screen is 7mm. Under this vibration condition, the organic carbonized ash can be removed to the greatest extent.

[0062] S300, performing dissolution and value adjustment processing on the mixed material after vibration screening to obtain a mixed solution.

[0063] In this embodiment, the mixed material after vibration screening is dissolved to form a mixed solution, and the solid-liquid mass ratio of the mixed solution is controlled to make the sodium sulfate in the mixed solution in a saturated state, so as to facilitate the subsequent precipitation of sodium sulfate.

[0064] Furthermore, in one of the embodiments, the solid-liquid mass ratio of the mixed solution after the dissolution adjustment treatment is 0.55:1 to 0.6:1. It can be understood that the solid-liquid ratio of the mixed solution after the dissolution adjustment treatment is controlled between 0.55:1 and 0.6:1, so that the sodium sulfate in the mixed solution is saturated, and the sodium sulfate salt can be recovered to the greatest extent, and the sodium sulfate salt can be returned to the battery preparation process for recycling, realizing the recycling and reuse of salt resources.

[0065] S400, performing freeze crystallization treatment on the mixed solution to obtain sodium sulfate salt and frozen liquid.

[0066] In this embodiment, since the solubility of sodium sulfate, sodium chloride and other impurity salts is different, and the solubility of sodium sulfate is lower in a freezing environment, the mixed solution is frozen so that sodium sulfate is precipitated from the mixed solution in an environment of -1°C to 1°C to form a slurry. At this time, sodium chloride and impurity salts will not precipitate. In this way, the sodium sulfate can be refined to recover the sodium sulfate salt to the greatest extent, and the sodium sulfate salt can also be returned to the front-end battery preparation process for recycling, thereby realizing the reuse of salt resources.

[0067] S500, evaporating and concentrating the frozen liquid to obtain a sodium chloride salt and miscellaneous salt solution.

[0068] In this embodiment, the sodium chloride salt is refined by evaporating and concentrating the frozen liquid, and impurity salts will not precipitate. In this way, the sodium chloride salt can be recovered to the greatest extent, and the sodium chloride salt can be returned to the front-end battery preparation process for recycling, thereby realizing the reuse of salt resources.

[0069] S600, drying the mixed salt solution to obtain mixed salt.

[0070] In this embodiment, the mixed salt solution is dried by a drum dryer, and the mixed salt solution is further evaporated and dehydrated to recover other mixed salts. In addition, the organic content in the mixed salts is low, so there is no need to scrap the mixed salts, so the mixed salts can be sold, avoiding the waste of mixed salt resources and valuing the mixed salt resources.

[0071] Furthermore, in one of the embodiments, 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] See also Figure 1 In one embodiment, before the step S100 of pyrolyzing the evaporation mother liquor, the treatment process further includes the following steps:

[0073] S90, extracting the evaporation mother liquor to recover the residual lithium ions in the evaporation mother liquor. In this embodiment, since a small portion of lithium ions will remain in the front-end valuable metal extraction process and not be recycled, the evaporation mother liquor is extracted to recover the residual lithium ions in the evaporation mother liquor, thereby improving the treatment effect of the evaporation mother liquor and maximizing the recovery resources of the evaporation mother liquor.

[0074] For further information, see Figure 2 , step S90 of extracting the evaporated mother liquor comprises:

[0075] S91, transporting the evaporated mother liquor to an extraction tank;

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

[0077] It should be noted that the model of the extractant is HBL121, which is specially used for extracting lithium ions, and the diluent is sulfonated kerosene, wherein the mass of the extractant accounts for 28% of the total mass of the mixture of the extractant and the diluent, and the mass of the diluent accounts for 72% of the total mass of the mixture of the extractant and the diluent, so that the lithium ions in the evaporation mother liquor can be adsorbed into the extract, and the lower layer of the evaporation mother liquor is transported to the pyrolysis treatment process to maximize the recovery of the evaporation mother liquor resources.

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

[0079] For further information, see Figure 2 After step S92 of adding an extractant and a diluent into the extraction tank to extract lithium ions from the evaporated mother liquor, step S90 further includes the following steps:

[0080] S93, performing an acid-adding and decomposition operation on the upper layer of the extract to form an upper layer of an extractant and a lower layer of a decomposition solution;

[0081] S94, performing an alkali saponification operation on the upper layer extractant;

[0082] S95, returning the upper layer of extractant to the extraction tank for recycling.

[0083] It should be noted that by adding 2 mol / L sulfuric acid to the upper extract for analysis, lithium sulfate soluble in water is formed, so that lithium ions are separated from the upper extract to the lower analysis solution, and the resource recovery of the evaporated mother liquor is maximized. Then, by adding sodium hydroxide solution to the upper extract for saponification reaction, not only the sulfuric acid in the upper extract can be neutralized, but also the upper extractant can be saponified, the upper extractant can be reactivated, and the upper extractant can be circulated back to the extraction tank for continued use, which can further reduce the processing cost of the evaporated mother liquor.

[0084] See also Figure 3 In one embodiment, the step S100 of pyrolyzing the evaporation mother liquor comprises:

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

[0086] S104, carbonizing the solid salt mixture to obtain a mixed material.

[0087] It should be noted that the evaporation mother liquor is pre-carbonized by a pre-carbonization reactor. Specifically, the evaporation mother liquor is pumped into the pre-carbonization reactor, and the mother liquor enters the furnace body from the upper end in a spray state. The liquid flow rate is 4L / min, the upper furnace temperature is controlled at 400°C to 500°C, the lower furnace temperature is controlled at 300°C to 350°C, and the pyrolysis time is controlled at 60min. Under this temperature and time control, pre-carbonization solidifies the salt in the evaporation mother liquor and pyrolyzes and carbonizes some organic matter in an oxygen atmosphere. At the same time, volatile organic matter will enter the exhaust gas treatment system along the exhaust gas emission end of the pre-carbonization reactor. Furthermore, the solid salt mixture is carbonized by a solid carbonization reactor. Specifically, the solid salt mixture after pre-carbonization is also doped with organic carbon matter. The dried solid salt mixture is immediately sent to the solid carbonization reactor after pre-carbonization. The pyrolysis carbonization temperature is controlled at 750°C to 850°C, nitrogen is used as a protective gas, and the pyrolysis time is controlled at 20min to 30min, so that the organic carbon is pyrolyzed into organic carbonized ash and moisture in an oxygen-free environment. The moisture enters the exhaust gas treatment system along with the exhaust gas of the solidification carbonization reactor, thereby effectively removing organic matter in the evaporation mother liquor.

[0088] Furthermore, the pyrolysis tail gas enters the spray tower of the tail gas treatment system, so that the harmful substances in the tail gas are washed away by the spray water, and the tail gas passing through the spray tower can be discharged after meeting the emission standards. Furthermore, the spray water is transported to the biochemical system for treatment to ensure that it can be discharged after meeting the emission standards, thereby ensuring the environmental protection of the entire treatment process.

[0089] See also Figure 4 In one embodiment, the step S300 of dissolving and adjusting the mixed material after vibration screening includes:

[0090] S302, stirring and dissolving the mixed material after vibration screening to obtain a mixed solution; in this embodiment, the mixed material after vibration screening is stirred and dissolved in pure water in the re-dissolution tank. Further, the stirring time of the stirring and dissolving operation is 30 minutes to 60 minutes, which can ensure that the mixed solution is completely dissolved.

[0091] S304, adjusting the pH value of the mixed solution.

[0092] It can be understood that the mixed material after vibration screening is stirred and dissolved in the re-dissolution tank by pure water, and then the pH of the mixed solution is adjusted to react the carbonate ions and bicarbonate ions in the mixed solution to form carbon dioxide and water, thereby further concentrating the mixed solution.

[0093] For further information, see Figure 5 The step S304 of adjusting the pH of the mixed solution includes:

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

[0095] S3044, adding sodium hydroxide solution into the mixed solution to adjust the pH value of the mixed solution to a neutral condition, so that the solubility of sodium salt and other impurity salts are at a higher level, avoiding the premature precipitation of salt.

[0096] Furthermore, the mixed solution is subjected to a pH adjustment treatment, and the temperature is controlled at 40°C to 45°C. Specifically, 30% sulfuric acid is added to the mixed solution to adjust the pH value of the mixed solution to 3, and the temperature is controlled at 40°C to 45°C, so that the carbonate ions and bicarbonate ions in the mixed solution can be reacted to form carbon dioxide and water, and the mixed solution is further concentrated to increase the concentration of sodium sulfate and sodium chloride, which is convenient for subsequent salt precipitation. Then, by adding sodium hydroxide solution to the mixed solution, the pH value of the mixed solution is adjusted back to 7, and the temperature is controlled at 40°C to 45°C, so that the solubility of sodium salt and other miscellaneous salts is at a higher level, avoiding the situation where salt precipitates prematurely.

[0097] See also Figure 1 In one embodiment, after the operation step S300 of dissolving and adjusting the mixed material after vibration screening, and before the operation step S400 of freezing and crystallizing the mixed solution, the processing process further includes the following operation steps:

[0098] S301, filtering and adsorbing the mixed solution to remove residual organic matter in the mixed solution.

[0099] It is understandable that since there may be a small amount of difficult-to-degrade organic matter remaining after pyrolysis treatment and some organic carbonized ash remaining in the mixed solution, the difficult-to-degrade organic matter and organic carbonized ash can be removed by filtering and adsorbing the mixed solution, thereby further improving the treatment effect of organic matter in the evaporation mother liquor, thereby effectively improving the quality of recovered impure salts.

[0100] For further information, see Figure 6 In one embodiment, the step S301 of filtering and adsorbing the mixed solution after the dissolution adjustment process includes:

[0101] S3012, filtering the mixed solution after the dissolution and adjustment process to remove the organic carbonized ash remaining in the mixed solution;

[0102] S3014, using degreasing resin to adsorb the mixed solution to remove residual organic matter in the mixed solution.

[0103] It should be noted that the organic carbonized ash remaining in the mixed solution after the dissolution adjustment treatment is removed by filtering, and then the residual organic matter in the mixed solution is adsorbed and removed by a large-pore degreasing resin, which further improves the treatment effect of organic matter in the evaporation mother liquor.

[0104] It should be noted that the organic carbonized ash after filtration should be treated as hazardous waste, and the pore size of the oil removal resin is 200nm~300nm.

[0105] Furthermore, after the degreasing resin is saturated with adsorption, it needs to be analyzed by adding liquid alkali, and the analyzed liquid is transported to the biochemical system for treatment to ensure that it is discharged only after meeting the standards. Furthermore, after the degreasing resin has been used for a period of time, it needs to be regenerated. Through acidic and alkaline treatment, the degreasing resin can be regenerated and recycled, and the regenerated liquid is also transported to the biochemical system for treatment to ensure that it is discharged only after meeting the standards.

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

[0107] S402, performing cooling and separation treatment on the mixed solution after the filtration and adsorption treatment to obtain sodium sulfate slurry and frozen liquid respectively.

[0108] In this embodiment, the mixed solution is subjected to a temperature reduction and separation process by a freezing crystallization device. Further, the temperature of the freezing crystallization device is -1°C to 1°C.

[0109] S404, performing a first filter pressing and drying treatment on the sodium sulfate slurry to obtain a frozen filtrate and sodium sulfate salt, respectively.

[0110] In this embodiment, the sodium sulfate slurry is subjected to solid-liquid separation by a horizontal screw compressor to obtain sodium sulfate crystals and a frozen filtrate, and then the sodium sulfate crystals are dried by a fluidized drying bed to recover the sodium sulfate salt. In this way, the sodium sulfate salt can be recovered to the greatest extent, thereby realizing the classified recovery of sodium salt and the reuse of salt resources.

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

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

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

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

[0115] In this embodiment, the frozen liquid is evaporated by an evaporation MVR device to remove most of the water to form an evaporated liquid, so that the sodium chloride concentration in the evaporated liquid is increased to be in a sodium chloride saturated state, so as to facilitate the precipitation of sodium chloride.

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

[0117] S504, performing thickening and separation treatment on the evaporated liquid to obtain sodium chloride slurry and mixed salt solution respectively.

[0118] In this embodiment, the evaporated liquid is subjected to thickening and separation treatment by a thickener, so that sodium chloride is precipitated from the evaporated liquid in the thickener, and the evaporated liquid is separated into sodium chloride slurry and a mixed salt solution.

[0119] S506, performing a second filter pressing and drying treatment on the sodium chloride slurry to obtain sodium chloride salt and an evaporated filtrate respectively.

[0120] In this embodiment, the sodium chloride slurry is subjected to solid-liquid separation by a horizontal screw compressor to obtain sodium chloride crystals and an evaporation filtrate, and then the sodium chloride crystals are dried by a fluidized drying bed to recover the sodium chloride salt. In this way, the sodium chloride salt can be recovered to the greatest extent, thereby realizing the classified recovery of sodium salt and the reuse of salt resources.

[0121] S508, conveying the impure salt solution and the evaporated filtrate to a drying process. In this embodiment, the impure salt solution and the evaporated filtrate are conveyed to the next drying process to recover the impure salt.

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

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

[0124] Detecting whether the sodium chloride concentration of the frozen liquid is greater than or equal to a preset sodium chloride concentration value; if so, performing evaporation and concentration treatment on the frozen liquid;

[0125] Otherwise, the frozen liquid is recycled to the dissolution and adjustment step.

[0126] It should be noted that when the sodium chloride concentration of the frozen liquid in the frozen mother liquid tank is greater than or equal to the preset sodium chloride concentration value, the energy consumption of the evaporation MVR device can be reduced, and a better concentration effect can be achieved. When the sodium chloride concentration of the frozen liquid in the frozen mother liquid tank is less than the preset sodium chloride concentration value, it is refluxed to the dissolution and value adjustment step as a solvent to dissolve the mixed material, saving the input of pure water and reducing the processing cost of the evaporation mother liquid.

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

[0128] Furthermore, the frozen liquid is recycled to the dissolution and adjustment step, specifically, the frozen liquid is recycled to the re-melting tank. Furthermore, before the frozen liquid is returned to the re-melting tank, it needs to be heat exchanged by a heat exchanger to avoid the low-temperature frozen liquid from being difficult to completely dissolve the mixed material and to avoid the premature precipitation of sodium sulfate in the re-melting 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 treatment process further comprises:

[0130] Check whether the mass percentage of sodium chloride in the frozen liquid is greater than or equal to a 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 in a saturated state, the evaporated liquid is passed into a thickener for thickening to precipitate sodium chloride. Sodium chloride forms sodium chloride slurry at the bottom of the thickener according to the principle of gravity drop. In this way, sodium chloride can be recovered to the greatest extent while reducing the energy consumed by evaporation, further reducing the processing cost of the evaporated mother liquor.

[0132] Furthermore, the mass proportion of sodium chloride in the frozen liquid is detected in real time, that is, the mass proportion of sodium chloride in the frozen liquid in the evaporation MVR device is displayed in real time, which can avoid excessive evaporation, minimize evaporation energy consumption, and further reduce the processing cost of the evaporation mother liquor.

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

[0134] Examples are listed below, but it should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial channels unless otherwise specified. Specific embodiments

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

[0137] The target evaporation mother liquor is treated by the treatment process disclosed in the present invention, and the target evaporation mother liquor is treated in three batches.

[0138] The specific operation steps of the treatment process are as follows:

[0139] (1) Extraction: The evaporated mother liquor on the production line enters the extraction tank to extract 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 the extractant and the diluent, and the mass of the diluent accounts for 72% of the total mass of the mixture of the extractant and the diluent). After the extraction is completed, the evaporated mother liquor enters the next process, and 2 mol / L sulfuric acid solution is added to the organic phase for analysis. After the analysis is completed, it is saponified with sodium hydroxide solution. Among them, the extractant is HBL121 extractant produced by Hunan Hongbang New Materials Co., Ltd.

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

[0141] (3) Carbonization: After pre-carbonization, the dried solid salt mixture is immediately fed into a solid carbonization furnace. The pyrolysis carbonization temperature is controlled at 800°C, nitrogen is used as a protective gas, and the pyrolysis time is controlled at 30 minutes. The waste gas generated by the pyrolysis enters the tail gas treatment system.

[0142] (4) Vibration screening: Use a vibrating screen to separate part of the organic carbonized ash from the salt in the carbonized mixed material. The eccentric shaft speed of the vibrating screen is 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. The organic carbonized ash is treated as hazardous waste.

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

[0144] (5) Filtration: Filter to remove organic carbonized ash in the mixed solution.

[0145] (6) Adsorption: After filtration, the mixed solution is adsorbed with a large-pore degreasing resin to remove organic matter in the mixed solution. After adsorption saturation, liquid alkali is used for analysis, and the analyzed solution is collected and enters the biochemical system.

[0146] (7) Freeze crystallization: The mixed solution after adsorption is transported to a freeze crystallization device, where the temperature is reduced to 0°C to obtain sodium sulfate slurry, which is then separated into solid and liquid by a horizontal screw compressor. The compressed solid is then sent to a fluid drying bed for drying. The frozen liquid and the frozen filtrate enter a frozen mother liquor tank. When the sodium chloride concentration is greater than 300 g / L, the frozen liquid enters an evaporation MVR device for evaporation and concentration. When the sodium chloride concentration is less than 300 g / L, the frozen liquid flows back to the anti-dissolution tank to continue dissolving sodium sulfate and enriching sodium chloride. The evaporation MVR device is a mechanical vapor recompression evaporator of Hebei Leheng Energy Saving Equipment Co., Ltd.

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

[0148] (9) Fluidized bed drying: The compressed solid salt is sodium sulfate decahydrate and sodium chloride. The solid salt needs to be subjected to crystallization water removal. The solid salt is respectively transferred to a solid fluidized bed for drying. The hot air temperature is 150°C, the hot air pressure is -100 Pa, and the drying time is 40 min to obtain anhydrous sodium sulfate and anhydrous sodium chloride, respectively.

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

[0150] The characterization data of the output anhydrous sodium sulfate and sodium chloride are shown in Tables 1 and 2, wherein Table 1 shows the composition of the output sodium sulfate and Table 2 shows the composition of the output 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 the surface of a substance, expressed as the percentage of white content. The whiteness of industrial sodium sulfate is required to be above 82%.

[0157] As can be seen from Tables 1 and 2, the target evaporation mother liquor is divided into three batches for sodium salt recovery treatment using the recovery treatment process disclosed in the present invention. The purity of sodium chloride recovered by the three batches of water is above 97%, and the purity of sodium sulfate recovered by the three batches of water is above 98%. The sodium chloride and sodium sulfate recovered by the three batches of water do not contain organic matter, and the content of other impurities is also low. Moreover, the whiteness of the sodium sulfate recovered by the three batches of water is above 82%, so that the sodium chloride and sodium sulfate recovered by the three batches of water can be directly transported to the front-end battery preparation process for use. This also shows that the treatment process disclosed in the present invention can effectively remove organic matter in the evaporation mother liquor, realize the fine classification recovery of sodium salt, and recover the salt resources in the evaporation mother liquor to the greatest extent.

[0158] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the disclosed patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the disclosed patent shall be subject to the attached claims.

Claims

1. A process for treating evaporation mother liquor generated in the process of recycling waste batteries, characterized in that: The steps include: Performing pyrolysis treatment on the evaporated mother liquor to obtain a mixed material; Performing vibration screening on the mixed material to remove organic carbonized ash in the mixed material; Performing a dissolution and value adjustment process on the mixed material after the vibration screening process to obtain a mixed solution; The mixed solution is subjected to a freeze crystallization process to obtain a sodium sulfate salt and a frozen liquid; The frozen liquid is evaporated and concentrated to obtain a sodium chloride salt and miscellaneous salt solution; The mixed salt solution is dried to obtain mixed salt.

2. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 1 is characterized in that: Before the step of pyrolyzing the evaporation mother liquor, the treatment process further comprises: The evaporation mother liquor is subjected to extraction treatment to recover the lithium ions remaining in the evaporation mother liquor.

3. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 1, characterized in that: The steps of pyrolyzing the evaporation mother liquor include: performing a pre-carbonization treatment on the evaporated mother liquor to obtain a solid salt mixture; The solid salt mixture is subjected to carbonization treatment to obtain the mixed material.

4. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 1, characterized in that: The step of dissolving and adjusting the mixed material after the vibration screening process comprises: Stirring and dissolving the mixed material after the vibration screening process to obtain the mixed solution; The mixed solution is subjected to a pH adjustment treatment.

5. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 1, characterized in that: After the step of dissolving and adjusting the mixed material after the vibration screening process, and before the step of freezing and crystallizing the mixed solution, the processing process further includes: The mixed solution is subjected to filtering and adsorption treatment to remove residual organic matter in the mixed solution.

6. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 1, characterized in that: The step of subjecting the mixed solution to freeze crystallization treatment comprises: The mixed solution is subjected to a cooling and separation treatment to obtain the sodium sulfate slurry and the frozen liquid respectively; Performing a first filter pressing and drying treatment on the sodium sulfate slurry to obtain the frozen filtrate and the sodium sulfate salt respectively; The frozen liquid and the frozen filtrate are sent to an evaporation concentration treatment step.

7. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 1, characterized in that: The step of evaporating and concentrating the frozen liquid comprises: performing an evaporation treatment on the frozen liquid to obtain an evaporated liquid; Performing thickening and separation treatment on the evaporated liquid to obtain sodium chloride slurry and the mixed salt solution respectively; Performing a second filter pressing and drying treatment on the sodium chloride slurry to obtain the sodium chloride salt and the evaporated filtrate respectively; The mixed salt solution and the evaporated filtrate are sent to a drying step.

8. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 7, characterized in that: Before the step of evaporating the frozen liquid, the step of evaporating and concentrating the frozen liquid further includes: Detecting whether the sodium chloride concentration of the frozen liquid is greater than or equal to a preset sodium chloride concentration value; if so, subjecting the frozen liquid to evaporation and concentration treatment; Otherwise, the frozen liquid is recycled to the dissolution and adjustment step.

9. The process for treating the evaporation mother liquor generated in the waste battery recycling process according to claim 7, characterized in that: After the step of evaporating the frozen liquid and before the step of thickening and separating the evaporated liquid, the treatment process further comprises: Detect whether the mass percentage of sodium chloride in the frozen liquid is greater than or equal to a preset mass percentage value; if so, stop the evaporation process.

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

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