A lithium iron phosphate cleaning wastewater recycling treatment system and recycling treatment method

Abstract

The application provides a lithium iron phosphate cleaning wastewater recycling treatment system, characterized by comprising: a reaction tank, which is used for receiving lithium iron phosphate cleaning wastewater and performing a pretreatment reaction to obtain a pretreatment mixed solution; a dewatering device, which is used for receiving the pretreatment mixed solution and performing mud-water separation to obtain a pretreatment intermediate solution; a precision filter, which is used for receiving the pretreatment intermediate solution and performing precision filtration to obtain a pretreatment solution; an ultrafiltration device, which is used for receiving the pretreatment solution and performing ultrafiltration to obtain a reverse osmosis treatment solution; a first reverse osmosis device, which is used for receiving the reverse osmosis treatment solution and performing desalination treatment to obtain a first reverse osmosis clear solution; and a second reverse osmosis device, which is used for receiving the first reverse osmosis clear solution and performing desalination treatment to obtain recycled water, wherein the system has a high wastewater recycling ratio, low energy consumption and is suitable for large-scale industrial application. The application also provides a lithium iron phosphate cleaning wastewater recycling treatment method.

Description

Technical Field

[0001] This invention relates to the field of new energy battery manufacturing, and more specifically, to a recycling and treatment system and method for lithium iron phosphate cleaning wastewater generated during the lithium iron phosphate manufacturing process. Background Technology

[0002] With the development of science and technology, electronic devices are being used more and more widely, especially mobile electronic devices, which are finding increasingly diverse applications. Almost all mobile electronic devices rely on batteries, making battery technology research and development a focus of increasing attention, with battery manufacturing technology being the core of the industry.

[0003] Common batteries, such as lithium iron phosphate (LFP) batteries, have become the mainstream in the current new energy industry due to their excellent cycle performance, high safety, and environmentally friendly nature. Compared with traditional lithium-ion rechargeable battery cathode materials, LFP batteries are more widely available, cheaper, and more environmentally friendly. The main wastewater generated during the LFP manufacturing process is LFP cleaning wastewater. With the expanding application of LFP materials, the output of LFP cleaning wastewater during manufacturing is also increasing. Currently, there is a lack of effective methods for large-scale automated recycling and treatment of LFP cleaning wastewater, and improvements are urgently needed. Summary of the Invention

[0004] In view of the above, the present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a lithium iron phosphate cleaning wastewater recycling and treatment system and method. Through the recycling and treatment system or method provided by the present invention, intelligent, large-scale, and automatic recycling of lithium iron phosphate cleaning wastewater can be achieved, greatly improving the wastewater discharge pollution problem in the lithium iron phosphate manufacturing process, while simultaneously achieving efficient resource reuse, resulting in significant benefits.

[0005] Therefore, in a first aspect, embodiments of the present invention provide a lithium iron phosphate cleaning wastewater recycling and treatment system, comprising:

[0006] The reaction tank is used to receive lithium iron phosphate cleaning wastewater and carry out pretreatment reactions to obtain a pretreatment mixture.

[0007] A dehydration device is used to receive the pretreatment mixture and perform mud-water separation to obtain a pretreatment intermediate liquid;

[0008] A precision filter is used to receive the pretreatment intermediate liquid and perform precision filtration to obtain a pretreatment liquid;

[0009] An ultrafiltration device is used to receive the pretreatment liquid and perform ultrafiltration to obtain a reverse osmosis solution to be treated;

[0010] A first-stage reverse osmosis unit is used to receive the reverse osmosis solution to be treated and perform desalination treatment to obtain a first reverse osmosis clear solution.

[0011] A secondary reverse osmosis unit is used to receive the first reverse osmosis solution and perform desalination treatment to obtain recycled water.

[0012] Preferably, the dehydration device is one of a vacuum filter, a filter press, a centrifuge, a screw press, or a roller press.

[0013] Preferably, the reaction tank includes a first reaction tank and a second reaction tank, and the dewatering device includes a first filter press and a second filter press, wherein,

[0014] The first reaction tank is used to receive lithium iron phosphate cleaning wastewater and perform a first pretreatment reaction to obtain a first pretreatment mixture;

[0015] The first filter press is used to receive the first pretreatment mixture and perform mud-water separation to obtain the first pretreatment intermediate liquid;

[0016] The second reaction tank is used to receive the first pretreatment intermediate liquid and perform a second pretreatment reaction to obtain a second pretreatment mixture;

[0017] The second filter press is used to receive the second pretreatment mixture and perform mud-water separation to obtain the second pretreatment intermediate liquid;

[0018] The precision filter is used to receive the second pretreatment intermediate liquid and perform precision filtration to obtain the pretreatment liquid.

[0019] Preferably, the reaction tank further includes a third reaction tank for receiving the pretreatment solution and performing an acidification reaction to obtain an acidified pretreatment solution;

[0020] The ultrafiltration device is used to receive the acidification pretreatment solution and perform ultrafiltration to obtain the reverse osmosis solution to be treated.

[0021] Preferably, it also includes a backwash collection tank for collecting the remaining backwash liquid after ultrafiltration of the ultrafiltration device and conveying it to the second reaction tank.

[0022] Preferably, it further includes a ferric phosphate sludge tank for receiving ferric phosphate sludge produced by the sludge-water separation process of the first filter press; and / or,

[0023] It also includes a heavy metal sludge tank for receiving heavy metal sludge generated from the sludge-water separation process of the second filter press.

[0024] Preferably, it further includes an evaporation device for receiving the first high-concentration liquid to be treated generated by the first-stage reverse osmosis device and evaporating and crystallizing it to obtain an evaporated liquid, which is then transported to the second-stage reverse osmosis device.

[0025] Preferably, the evaporation device is one of a multi-effect evaporation device or an MVR evaporation device.

[0026] Preferably, the first-stage reverse osmosis unit is also used to receive a second high-concentration liquid to be treated generated by the second-stage reverse osmosis unit.

[0027] Preferably, the precision filter is further used to receive the remaining filtrate to be returned after the ultrafiltration device has obtained the reverse osmosis solution.

[0028] Secondly, embodiments of the present invention also provide a method for recycling and treating lithium iron phosphate cleaning wastewater, comprising the following steps:

[0029] S10. Add hydrogen peroxide (H2O2), ferrous sulfate (FeSO4), and sulfuric acid (H2SO4) to the lithium iron phosphate cleaning wastewater in a certain proportion, mix them, remove the precipitate after reaction, and obtain the first pretreatment intermediate liquid.

[0030] S20. Add sodium hydroxide to the first pretreatment intermediate solution to adjust the pH value to alkaline. After the reaction, remove the precipitate to obtain the second pretreatment intermediate solution.

[0031] S30. The second pretreatment intermediate liquid is precisely filtered to obtain the pretreatment liquid.

[0032] S40. Add sulfuric acid to the pretreatment solution to adjust the pH to acidic, and then proceed with ultrafiltration, first-stage reverse osmosis and second-stage reverse osmosis to obtain recycled water.

[0033] Preferably, step S30, which involves precision filtering the second pretreatment intermediate liquid to obtain the pretreatment liquid, specifically includes:

[0034] The second pretreatment intermediate liquid is precisely filtered to obtain the pretreatment liquid and the liquid to be rewashed.

[0035] Step S20 involves adding sodium hydroxide to the first pretreatment intermediate solution to adjust the pH to alkaline, reacting the precipitate to obtain the second pretreatment intermediate solution, specifically including:

[0036] Mix the first pretreatment intermediate solution and the solution to be backwashed, add sodium hydroxide to adjust the pH to alkaline, and remove the precipitate after the reaction to obtain the second pretreatment intermediate solution.

[0037] Preferably, the clarified liquid obtained from the first-stage reverse osmosis process is subjected to the second-stage reverse osmosis process, and the first high-concentration liquid obtained from the first-stage reverse osmosis process is evaporated and crystallized to obtain an evaporation treatment liquid for the second-stage reverse osmosis process.

[0038] Preferably, the clarified liquid obtained from the secondary reverse osmosis process is the recycled water, and the second high-concentration liquid obtained from the secondary reverse osmosis process is reused for the primary reverse osmosis process.

[0039] Preferably, the clarified liquid obtained from the ultrafiltration process is subjected to the first-stage reverse osmosis, and the filtrate to be returned from the ultrafiltration process is subjected to the precision filtration again.

[0040] Preferably, the molar ratio of the lithium iron phosphate cleaning wastewater to hydrogen peroxide, the ferrous sulfate, and the sulfuric acid satisfies n(wastewater):n(H2O2):n(FeSO4):n(H2SO4) = 1:0.221:0.321:0.11.

[0041] Preferably, in step S20, the pH value is adjusted to 8-11; in step S40, the pH value is adjusted to 4-5.

[0042] The lithium iron phosphate cleaning wastewater recycling and treatment system provided in this embodiment of the invention has a simple structure. Through multi-step combined recycling and treatment, the purity of the recycled wastewater is improved. Furthermore, the products of the process steps are repeatedly recycled and treated, which further improves the overall recycling efficiency and realizes efficient and automatic recycling and treatment of cleaning wastewater. This lithium iron phosphate cleaning wastewater recycling and treatment system and method are conducive to resource conservation, suitable for large-scale application, and realize cost reduction and efficiency improvement in production and manufacturing. Attached Figure Description

[0043] Figure 1 A schematic diagram of the framework structure of a lithium iron phosphate cleaning wastewater recycling and treatment system provided in an embodiment of the present invention;

[0044] Figure 2 A schematic diagram of the framework structure of another lithium iron phosphate cleaning wastewater recycling and treatment system provided in an embodiment of the present invention;

[0045] Figure 3 A flowchart of a method for recycling and treating lithium iron phosphate cleaning wastewater provided in an embodiment of the present invention. Detailed Implementation

[0046] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0047] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided in this invention; however, those skilled in the art will recognize the applicability of other processes and / or the use of other materials.

[0048] Please refer to this as well. Figure 1 This invention provides a lithium iron phosphate cleaning wastewater recycling and treatment system 100, applied in the lithium iron phosphate material manufacturing process to recycle and treat the generated lithium iron phosphate cleaning wastewater. The lithium iron phosphate cleaning wastewater recycling and treatment system 100 specifically includes:

[0049] Reaction tank 10 is used to receive lithium iron phosphate cleaning wastewater and carry out pretreatment reaction to obtain pretreatment mixture;

[0050] Dehydration device 20 is used to receive the pretreatment mixture and perform mud-water separation to obtain pretreatment intermediate liquid;

[0051] Precision filter 30 is used to receive the pretreatment intermediate liquid and perform precision filtration to obtain pretreatment liquid;

[0052] Ultrafiltration device 40 is used to receive the pretreatment liquid and perform ultrafiltration to obtain reverse osmosis solution to be treated;

[0053] A first-stage reverse osmosis unit 50 is used to receive the reverse osmosis solution to be treated and perform desalination treatment to obtain a first reverse osmosis clear solution.

[0054] The secondary reverse osmosis unit 60 is used to receive the first reverse osmosis solution and perform desalination treatment to obtain recycled water.

[0055] The reaction tank 10, dehydration device 20, precision filter 30, ultrafiltration device 40, primary reverse osmosis device 50, and secondary reverse osmosis device 60 are arranged sequentially and connected to each other via pipelines, sequentially conveying the treated target recovery liquid from the upstream device to the downstream device. In this embodiment, a chemical precipitation method is used, adding an appropriate amount of chemical reagent to react with metal ions in the wastewater to generate precipitates; the precipitates are separated from the wastewater by precipitation or filtration; large metal precipitates are removed by precision filtration; ultrafiltration with a pore size of 0.1 micrometers can intercept impurities remaining in the water after sand filtration; the effluent from the ultrafiltration membrane meets the requirement of a reverse osmosis feed water fouling index (SDI) ≤ 3; high-purity water is then recovered through primary and secondary reverse osmosis to meet the purity requirements of the water; thus, efficient recovery of lithium iron phosphate cleaning wastewater is achieved.

[0056] The precision filter 30 employs a novel low-pressure backwash liquid filtration device, combining surface filtration technology, industrial automatic control technology, and valve technology to achieve automated surface filtration. Its filtration method is positive pressure, using a filter membrane to filter solid particles and suspended matter in the liquid, achieving a removal rate of up to 99%. Its specific working principle includes: Filtration: The liquid to be filtered is pumped into the lower chamber of the filter by the inlet pump, while the clear liquid enters the upper chamber through the filter element. Solid substances in the liquid are trapped on the filter membrane surface, forming a filter cake; Backwash: Within seconds of the backwash valve opening, negative pressure is created inside the chamber, causing the clear liquid to flow back and causing the filter cake to detach completely from the filter membrane surface; Sedimentation: Under gravity, a large amount of filter cake settles vertically in the turbid liquid in the lower chamber, naturally accumulating towards the discharge port in the conical section; Discharge: When the discharge port opens, the accumulated slag cake is rapidly discharged, while the residual mud cake remaining on the filter element surface is removed from the filter membrane surface through a secondary backwash.

[0057] The ultrafiltration device 40 serves as a pretreatment for reverse osmosis, removing suspended particles, colloids, and microorganisms from the water. Under water pressure, water molecules and small molecules permeate through the ultrafiltration membrane, while suspended particles, colloids, and microorganisms are trapped on the membrane surface. Because the micropores on the ultrafiltration membrane are very small, it effectively removes various suspended particles, colloids, bacteria, and large organic molecules larger than the pore size, ensuring that the SDI of the water entering the reverse osmosis unit meets requirements. The ultrafiltration device 40 is an integrated unit, meaning that the membrane, pipes, valves, and instruments are all integrated on a single frame. All system pipelines and equipment have undergone operational testing, pipeline pressure testing, and electrical testing before leaving the factory. Upon arrival at the site, only the inlet and outlet pipelines, power supply, and control cable need to be connected for immediate use, saving on-site construction and commissioning time.

[0058] Reverse osmosis utilizes the property of a reverse osmosis membrane (an artificial semi-permeable membrane) to selectively allow only the solvent (usually water) to pass through while retaining solutes (soluble salts, colloids, suspended solids, etc.). By using a pressurized device with the pressure difference across the membrane as the driving force, the osmotic pressure of the solvent is overcome, forcing the solvent through the reverse osmosis membrane, thus achieving the separation of liquid mixtures. Generally, a single seawater reverse osmosis membrane element can achieve a rejection rate of over 99.7%, a single brackish water reverse osmosis membrane element can achieve a rejection rate of over 99.4%, and a single low-pressure reverse osmosis membrane element can achieve a rejection rate of over 98.6%. In this embodiment, to improve the recovery rate of the reverse osmosis system, the reverse osmosis units are arranged in series, thus the system's rejection rate will be lower than that of a single reverse osmosis membrane element. First-stage reverse osmosis can remove over 98% of dissolved salts and over 99% of colloidal microorganisms and organic matter from water, while second-stage reverse osmosis can remove over 90% of dissolved salts and over 99% of colloidal microorganisms and organic matter from water.

[0059] Furthermore, the dehydration device 20 is one of a vacuum filter, a filter press, a centrifuge, a screw press, or a roller press.

[0060] Sludge dewatering further removes pore water and capillary water from the sludge, reducing its volume. After dewatering, the sludge moisture content can be reduced to 70%–80%, and its volume is 1 / 10–1 / 4 of the original volume, which is beneficial for subsequent transportation and processing. Mechanical sludge dewatering methods include filtration dewatering, centrifugal dewatering, and press dewatering. Filtration dewatering includes vacuum filtration and pressure filtration (press filtration); centrifugal dewatering uses a centrifuge; press dewatering uses a screw press or roller press. Press filtration and centrifugal dewatering are the most commonly used methods. Sludge filtration dewatering uses the pressure difference across the filter medium as the driving force, forcing the sludge water through the filter medium to form a filtrate, while solid particles are retained on the medium to form a filter cake, thus achieving the purpose of sludge dewatering. Plate and frame filter presses were the first machines used for dewatering in the chemical industry. Although plate and frame filter presses are generally intermittently operated, require significant investment in infrastructure and equipment, and have relatively low filtration capacity, they are used for dewatering in subsequent embodiments due to their advantages such as high filtration driving force, high solid content in the filter cake, clear filtrate, high solid recovery rate, and low consumption of conditioning chemicals.

[0061] Please refer to Figure 2 Furthermore, the reaction tank 10 includes a first reaction tank 11 and a second reaction tank 12, and the dewatering device 20 includes a first filter press 21 and a second filter press 22, wherein...

[0062] The first reaction tank 11 is used to receive lithium iron phosphate cleaning wastewater and perform a first pretreatment reaction to obtain a first pretreatment mixture;

[0063] The first filter press 21 is used to receive the first pretreatment mixture and perform mud-water separation to obtain the first pretreatment intermediate liquid;

[0064] The second reaction tank 12 is used to receive the first pretreatment intermediate liquid and perform a second pretreatment reaction to obtain a second pretreatment mixture;

[0065] The second filter press 22 is used to receive the second pretreatment mixture and perform mud-water separation to obtain the second pretreatment intermediate liquid;

[0066] The precision filter 30 is used to receive the second pretreatment intermediate liquid and perform precision filtration to obtain the pretreatment liquid.

[0067] In this embodiment, two consecutive sets of reaction tanks 10 and filter presses 20 are set up to complete two sets of chemical precipitation reactions to precipitate and transform two types of substances in the lithium iron phosphate cleaning wastewater. Specifically, the lithium iron phosphate wastewater first enters the first reaction tank 11, where hydrogen peroxide, ferrous sulfate, and sulfuric acid are added to react and remove most of the iron phosphate. The wastewater is then separated into mud and water by the first filter press 21. The clarified liquid from the first filter press 21 enters the second reaction tank 12, where alkali is added to adjust the pH to alkaline, causing heavy metals in the water to precipitate. The precipitate is then separated into mud and water by the second filter press 22. Through these two-step precipitation reaction and mud-water separation, most of the metal ion impurities are removed.

[0068] Furthermore, the reaction tank 10 also includes a third reaction tank 13, which is used to receive the pretreatment liquid and perform an acidification reaction to obtain an acidified pretreatment liquid;

[0069] The ultrafiltration device 40 is used to receive the acidification pretreatment solution and perform ultrafiltration to obtain the reverse osmosis solution to be treated.

[0070] In this embodiment, the pH of the ultrafiltration permeate is adjusted to 4-5 to ensure that the reverse osmosis can operate under slightly acidic conditions, thereby effectively reducing the tendency of the reverse osmosis membrane to scale.

[0071] Furthermore, it also includes a backwash collection tank 70, which is used to collect the remaining backwash liquid after ultrafiltration by the ultrafiltration device 40 and transport it to the second reaction tank 12.

[0072] In this implementation, the ultrafiltration membrane is specifically designed for the removal of particulate matter. Water is pressurized and passes through the membrane; due to the very small micropores on the membrane, this technology can effectively remove all suspended matter, including microorganisms. These contaminants accumulate on the membrane surface, therefore, periodic backwashing with a reverse flow of water is required to remove the contaminants.

[0073] Based on the water quality, the system adopts a cross-flow filtration method. Since the ultrafiltration concentrate and backwash effluent mainly consist of suspended matter and colloids, with no change in the content of other ions, the concentrate and backwash effluent from the ultrafiltration unit 40 are returned to the pre-stage reaction tank for recycling, ensuring higher system economy.

[0074] Furthermore, it also includes an iron phosphate sludge tank 80 for receiving iron phosphate sludge produced by the sludge-water separation of the first filter press 11; and / or,

[0075] It also includes a heavy metal sludge tank 90 for receiving heavy metal sludge generated by the sludge-water separation of the second filter press 12.

[0076] In this embodiment, the iron phosphate sludge and heavy metal sludge generated during pretreatment are collected for subsequent treatment, and secondary pollution is avoided.

[0077] Furthermore, it also includes an evaporation device 95, which is used to receive the first high-concentration liquid to be treated generated by the first-stage reverse osmosis device 50 and evaporate and crystallize it to obtain an evaporated liquid and transport it to the second-stage reverse osmosis device 60.

[0078] Evaporators are classified into evaporation concentrators and evaporation crystallizers according to their uses. The names of evaporators may vary depending on the process used, but they are essentially the same. The main purpose of an evaporator is to evaporate the non-volatile solutes in a solution, boil and vaporize the solution and remove it, thereby increasing the concentration of solutes in the solution.

[0079] Furthermore, the evaporation device 95 is either a multi-effect evaporator or a steam mechanical recompression (MVR) evaporator. The main difference between these two types of evaporation processes lies in the utilization of steam.

[0080] In this embodiment, the multi-effect evaporator specifically adopts a triple-effect evaporator, which consists of three sets of heaters, three sets of separators, a preheater, a pump set, a thickener, a mother liquor tank, a centrifuge, electrical instrumentation and control systems, valves, and pipelines. The three sets of evaporators operate in series, forming a triple-effect crystallizing evaporator. The entire evaporation system adopts a continuous feeding and continuous discharging production method. High-salt wastewater first enters the first-effect forced circulation crystallizing evaporator, which is equipped with a circulation pump that pumps the wastewater into the evaporation heat exchange chamber. In the evaporation heat exchange chamber, external steam liquefies to generate latent heat of vaporization, heating the wastewater. Due to the high pressure in the evaporation heat exchange chamber, the wastewater is heated to superheated at a pressure higher than the normal boiling point of liquids. After the heated liquid enters the crystallizing evaporation chamber, the pressure of the wastewater drops rapidly, causing some of the wastewater to flash evaporate or boil rapidly. The steam after the wastewater evaporates enters the second-effect forced circulation evaporator as driving steam to heat the second-effect evaporator. Unevaporated wastewater and salt are temporarily stored in the crystallizing evaporation chamber. The first, second, and third effect forced circulation evaporators are connected by a balance pipe. Under negative pressure, high-salinity wastewater flows sequentially from the first effect to the second and third effects. The wastewater is continuously evaporated, and the salt concentration in the wastewater increases. When the salt content exceeds saturation, salt continuously precipitates out and enters the salt collection chamber at the bottom of the evaporation crystallization chamber. A brine pump continuously sends the saline wastewater to a vortex salt separator. Inside the vortex salt separator, solid salt is separated and enters a salt storage tank. The separated wastewater then enters the second effect forced circulation evaporator for heating. This entire process repeats continuously, achieving the final separation of water and salt.

[0081] In addition, MVR evaporation consists of heaters, separators, preheaters, steam compressors, pump sets, thickeners, mother liquor tanks, centrifuges, electrical instrumentation and control systems, valves, and pipelines.

[0082] The working process of an MVR evaporator involves a low-temperature steam compressor compressing the secondary steam generated during material evaporation, increasing its pressure, temperature, and enthalpy. This converts electrical energy into heat energy. The heated secondary steam returns to the evaporation system to heat the material before entering a heat exchanger for condensation, thus fully utilizing the latent heat of the steam. Except during startup, no live steam is required during the entire evaporation process.

[0083] The secondary steam, compressed by the compressor, is sent to the heating chamber of the evaporator as heating steam to keep the liquid boiling. The heating steam itself condenses into water and is discharged from the system. The heated material is vaporized and concentrated and then discharged from the system as the final product. In the entire MVR evaporation system, the steam that was originally going to be wasted has value, the latent heat is recovered, and the efficiency can be increased by more than 50%.

[0084] The most critical component in an MVR evaporator is the steam compressor. The steam compressor is a key device in the heat recovery system that increases the temperature and pressure of the generated steam through compression. Its function is to pressurize and heat low-pressure (or low-temperature) steam to meet the temperature and pressure requirements of the process or project. Mechanical steam compressors are divided into two types: Roots steam compressors and centrifugal steam compressors. Centrifugal steam compressors are further divided into ordinary centrifugal compressors and single-stage high-speed centrifugal steam compressors. Different types of compressors have different characteristics and advantages under different application conditions.

[0085] 1) Roots compressors are positive displacement blowers, and compared to ordinary centrifugal compressors, they have a higher compression ratio. Roots steam compressors, due to their lower rotational speed, offer better stability.

[0086] Generally, the speed of a Roots steam compressor is between 980 and 1450 r / min, the speed of a regular centrifugal steam compressor is between 6000 and 9000 r / min, while the maximum speed of a single-stage high-pressure centrifugal blower can reach 30000 r / min.

[0087] Of course, the disadvantages of Roots blowers are also obvious. Their inherent defects include small single-stage volumetric flow rate, low efficiency, and short maintenance cycle (generally 2000h / time). At the same time, Roots blowers have a wide noise spectrum, with low and medium frequency noise of 63-8000HZ as the main component. The noise during operation can reach more than 100 decibels, which is very harmful to the health of personnel.

[0088] 2) Ordinary centrifugal steam compressors typically have a compression temperature rise of 8 to 10 degrees Celsius. Currently, the main models used are imported compressors, which have the advantages of high efficiency and stable performance.

[0089] In applications requiring a higher compression ratio, two centrifugal steam compressors can be connected in series to achieve a higher compression temperature rise, but at the same time, the efficiency of the compressors will decrease.

[0090] In general, boiling point occurs during evaporation, and some solutions may even boil very high. In such cases, two or three stages of fans need to be used in series.

[0091] 3) The significant features of a single-stage high-speed centrifugal compressor are high fan speed and a high compression ratio, resulting in a higher compression temperature rise. At the same time, it also has high efficiency, low energy consumption, and larger throughput, thus making it more widely used.

[0092] Currently, single-stage high-speed centrifugal compressors are mainly domestically produced, and the technology is relatively mature. The equipment maintenance cycle is more than 18 months. The noise frequency of single-stage high-speed centrifugal compressors is between 8000 and 12000 Hz, which is high-frequency secondary wave noise, exceeding the sensitive range of the human ear, and does not cause much harm to personnel.

[0093] Furthermore, the primary reverse osmosis unit 50 is also used to receive the second high-concentration liquid to be treated generated by the secondary reverse osmosis unit 60. In this embodiment, the high-concentration water from the secondary reverse osmosis re-enters the primary reverse osmosis unit, achieving recycling and further improving the recovery effect.

[0094] Furthermore, the precision filter 30 is also used to receive the remaining filtrate to be returned after the ultrafiltration device 40 has obtained the reverse osmosis solution through ultrafiltration. In this embodiment, the remaining filtrate to be returned after ultrafiltration by the ultrafiltration device 40 re-enters the precision filter, achieving recycling.

[0095] Please refer to Figure 3 This invention also provides a method for recycling and treating lithium iron phosphate cleaning wastewater, comprising the following steps:

[0096] S10. Add hydrogen peroxide (H2O2), ferrous sulfate (FeSO4), and sulfuric acid (H2SO4) to the lithium iron phosphate cleaning wastewater in a certain proportion, mix them, remove the precipitate after reaction, and obtain the first pretreatment intermediate liquid.

[0097] S20. Add sodium hydroxide to the first pretreatment intermediate solution to adjust the pH value to alkaline. After the reaction, remove the precipitate to obtain the second pretreatment intermediate solution.

[0098] S30. The second pretreatment intermediate liquid is precisely filtered to obtain the pretreatment liquid.

[0099] S40. Add sulfuric acid to the pretreatment solution to adjust the pH to acidic, and then proceed with ultrafiltration, first-stage reverse osmosis and second-stage reverse osmosis to obtain recycled water.

[0100] Further, step S30, which involves precision filtering the second pretreatment intermediate liquid to obtain a pretreatment liquid, specifically includes:

[0101] The second pretreatment intermediate liquid is precisely filtered to obtain the pretreatment liquid and the liquid to be rewashed.

[0102] Step S20 involves adding sodium hydroxide to the first pretreatment intermediate solution to adjust the pH to alkaline, reacting the precipitate to obtain the second pretreatment intermediate solution, specifically including:

[0103] Mix the first pretreatment intermediate solution and the solution to be backwashed, add sodium hydroxide to adjust the pH to alkaline, and remove the precipitate after the reaction to obtain the second pretreatment intermediate solution.

[0104] Furthermore, the clarified liquid obtained from the first-stage reverse osmosis process is subjected to the second-stage reverse osmosis process, and the first high-concentration liquid obtained from the first-stage reverse osmosis process is evaporated and crystallized to obtain an evaporation treatment liquid, which is then subjected to the second-stage reverse osmosis process.

[0105] Furthermore, the clarified liquid obtained from the secondary reverse osmosis process is the recycled water, and the second high-concentration liquid obtained from the secondary reverse osmosis process is used again for the primary reverse osmosis process.

[0106] Furthermore, the clarified liquid obtained from the ultrafiltration process undergoes the first-stage reverse osmosis, and the filtrate to be returned from the ultrafiltration process is subjected to the precision filtration again.

[0107] Furthermore, the molar ratio of the lithium iron phosphate cleaning wastewater to hydrogen peroxide, the ferrous sulfate, and the sulfuric acid satisfies n(wastewater):n(H2O2):n(FeSO4):n(H2SO4)=1:0.221:0.321:0.11.

[0108] Furthermore, in step S20, the pH value is adjusted to 8-11; in step S40, the pH value is adjusted to 4-5.

[0109] This system combines the characteristics of lithium iron phosphate wastewater with the design of various influencing factors to achieve the optimal overall system performance.

[0110] This system adopts a forced circulation evaporation process, and the material flow velocity in the heat exchange tube reaches 1.5 to 2 m / s. At this flow velocity, tube blockage is not likely to occur, which can effectively prevent the occurrence of tube blockage.

[0111] During the evaporation process, the material is heated by the heater under the drive of the circulating pump, rises along the central tube of the evaporation chamber, evaporates on the liquid surface, generates maximum supersaturation, and can achieve effective separation.

[0112] The steam compressor is one of the core components of the MVR unit. The compressor design adopts advanced design concepts such as numerical simulation, computer simulation and finite element analysis, which can meet the performance requirements of the system under different working conditions to the greatest extent.

[0113] Based on aerodynamic theory, the MVR steam compressor utilizes advanced fluid design software and CFD flow field analysis, achieving a three-dimensional impeller efficiency of over 92%. This series of products boasts advantages such as high efficiency, compact structure, stable operation, wide operating range, and simple operation. The overall performance has reached the advanced level of similar products both domestically and internationally, and it is widely used in industries such as petroleum, chemical, food, pharmaceutical, wastewater treatment, beverage, and additives.

[0114] The lithium iron phosphate cleaning wastewater recycling and treatment system provided in this embodiment of the invention has a simple structure. Through multi-step combined recycling and treatment, the purity of the recycled wastewater is improved. Furthermore, the products of the process steps are repeatedly recycled and treated, which further improves the overall recycling efficiency and realizes efficient and automatic recycling and treatment of cleaning wastewater. This lithium iron phosphate cleaning wastewater recycling and treatment system and method are conducive to resource conservation, suitable for large-scale application, and realize cost reduction and efficiency improvement in production and manufacturing.

[0115] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0116] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A lithium iron phosphate cleaning wastewater recycling and treatment system, characterized in that, include: The first reaction tank is used to receive lithium iron phosphate cleaning wastewater and hydrogen peroxide (H2O2), ferrous sulfate (FeSO4), and sulfuric acid (H2SO4), and to carry out the first pretreatment reaction to obtain the first pretreatment mixture. The molar ratio of the lithium iron phosphate cleaning wastewater to hydrogen peroxide, the ferrous sulfate, and the sulfuric acid satisfies n(wastewater):n(H2O2):n(FeSO4):n(H2SO4)=1:0.221:0.321:0.

11. A first filter press is used to receive the first pretreatment mixture and perform mud-water separation to obtain a first pretreatment intermediate liquid. The second reaction tank is used to receive the first pretreatment intermediate liquid and sodium hydroxide, and adjust the pH value to 8-11 to carry out the second pretreatment reaction to obtain the second pretreatment mixture. The second filter press is used to receive the second pretreatment mixture and perform mud-water separation to obtain the second pretreatment intermediate liquid. A precision filter is used to receive the second pretreatment intermediate liquid and perform precision filtration to obtain a pretreatment liquid; The third reaction tank is used to receive the pretreatment solution and sulfuric acid, and adjust the pH value to 4-5 to carry out an acidification reaction to obtain an acidified pretreatment solution. An ultrafiltration device is used to receive the acidification pretreatment solution and perform ultrafiltration to obtain a reverse osmosis solution to be treated; A first-stage reverse osmosis unit is used to receive the reverse osmosis solution to be treated and perform desalination treatment to obtain a first reverse osmosis clear solution. A secondary reverse osmosis unit is used to receive the first reverse osmosis solution and perform desalination treatment to obtain recycled water.

2. The recycling system according to claim 1, characterized in that, It also includes a backwash collection tank for collecting the remaining backwash liquid after ultrafiltration of the ultrafiltration device and transporting it to the second reaction tank.

3. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 1, characterized in that, It also includes a ferric phosphate sludge tank for receiving ferric phosphate sludge produced by the sludge-water separation process of the first filter press; and / or, It also includes a heavy metal sludge tank for receiving heavy metal sludge generated from the sludge-water separation process of the second filter press.

4. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 1, characterized in that, It also includes an evaporation unit, which receives the first high-concentration liquid to be treated generated by the first-stage reverse osmosis unit and evaporates and crystallizes it to obtain an evaporated liquid, which is then transported to the second-stage reverse osmosis unit.

5. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 4, characterized in that, The evaporation device is either a multi-effect evaporator or an MVR evaporator.

6. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 1, characterized in that, The primary reverse osmosis unit is also used to receive a second high-concentration solution produced by the secondary reverse osmosis unit; and / or The precision filter is also used to receive the remaining filtrate to be returned after the ultrafiltration device has obtained the reverse osmosis solution.

7. A method for recycling and treating lithium iron phosphate cleaning wastewater, characterized in that, Including the following steps: S10. Add hydrogen peroxide (H2O2), ferrous sulfate (FeSO4), and sulfuric acid (H2SO4) to the lithium iron phosphate cleaning wastewater in a certain proportion and mix. After the reaction, remove the precipitate to obtain the first pretreatment intermediate liquid. The molar ratio of the lithium iron phosphate cleaning wastewater to hydrogen peroxide, the ferrous sulfate, and the sulfuric acid satisfies n(wastewater):n(H2O2):n(FeSO4):n(H2SO4)=1:0.221:0.321:0.

11. S20. Add sodium hydroxide to the first pretreatment intermediate solution, adjust the pH value to 8-11, remove the precipitate after reaction, and obtain the second pretreatment intermediate solution. S30. The second pretreatment intermediate liquid is precisely filtered to obtain the pretreatment liquid. S40. Add sulfuric acid to the pretreatment solution to adjust the pH value to 4-5, and then perform ultrafiltration, first-stage reverse osmosis and second-stage reverse osmosis to obtain recycled water.

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