Lithium iron phosphate cleaning wastewater recovery treatment system

Abstract

The utility model provides a lithium iron phosphate cleaning wastewater recovery treatment system which is characterized by comprising a reaction tank used for receiving lithium iron phosphate cleaning wastewater and carrying out pretreatment reaction to obtain a pretreatment mixed solution; the dehydration device is used for receiving the pretreatment mixed solution and carrying out mud-water separation to obtain a pretreatment intermediate solution; the precision filter is used for receiving the pretreatment intermediate liquid and performing precision filtration to obtain pretreatment liquid; the ultrafiltration device is used for receiving the pretreatment liquid and performing ultrafiltration to obtain reverse osmosis liquid to be treated; the primary reverse osmosis device is used for receiving the reverse osmosis to-be-treated liquid and carrying out desalination treatment to obtain first reverse osmosis clear liquid; the second-stage reverse osmosis device is used for receiving the first reverse osmosis clear liquid and carrying out desalination treatment to obtain recycled water, and the system is high in wastewater recycling ratio, low in energy consumption and suitable for large-scale industrial application.

Description

Technical Field

[0001] The utility model relates to the field of new energy battery manufacturing, and more specifically, to a recycling and processing system for lithium iron phosphate cleaning wastewater produced in the lithium iron phosphate manufacturing process. Background Art

[0002] With the development of science and technology, the application of electronic devices is becoming more and more extensive, especially the application scenarios of mobile electronic devices are becoming more and more abundant. Almost all mobile electronic devices are inseparable from batteries, and the research and development of battery technology has received more and more attention, among which battery manufacturing technology is the core of the industry.

[0003] Common batteries, such as lithium iron phosphate batteries, have excellent cycle performance, high safety, and are green and pollution-free, making them the mainstream of the current new energy industry. Compared with traditional lithium-ion secondary battery cathode materials, lithium iron phosphate has a wider source, is cheaper, and is more environmentally friendly. The main wastewater in the preparation process of lithium iron phosphate is lithium iron phosphate cleaning wastewater. With the expansion of the application of lithium iron phosphate materials, the output of lithium iron phosphate cleaning wastewater in the manufacturing process is also increasing. At present, there is a lack of better methods for the large-scale automatic recycling and treatment of lithium iron phosphate cleaning wastewater, and improvement plans are urgently needed. Utility Model Content

[0004] In view of the above, the utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model proposes a lithium iron phosphate cleaning wastewater recovery and treatment system. Through the recovery and treatment system provided by the utility model, it is possible to realize intelligent large-scale automatic recovery of lithium iron phosphate cleaning wastewater, greatly improve the wastewater discharge pollution problem in the lithium iron phosphate manufacturing process, and at the same time realize efficient reuse of resources, with obvious results.

[0005] To this end, in a first aspect, an embodiment of the utility model provides a lithium iron phosphate cleaning wastewater recovery and treatment system, comprising:

[0006] A reaction tank, used for receiving lithium iron phosphate cleaning wastewater and performing a pre-treatment reaction to obtain a pre-treatment mixed solution;

[0007] A dehydration device, used for receiving the pre-treatment mixed liquid and performing mud-water separation to obtain a pre-treatment intermediate liquid;

[0008] A precision filter, used for receiving the pre-treatment intermediate liquid and performing precision filtration to obtain a pre-treatment liquid;

[0009] An ultrafiltration device, used for receiving the pre-treatment liquid and performing ultrafiltration to obtain a reverse osmosis treated liquid;

[0010] A primary reverse osmosis device, used for receiving the reverse osmosis treated liquid and performing desalination treatment to obtain a first reverse osmosis clear liquid;

[0011] The secondary reverse osmosis device is used to receive the first reverse osmosis clear liquid 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, and a roller press.

[0013] Preferably, the reaction tank comprises a first reaction tank and a second reaction tank, and the dehydration device comprises 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 mixed solution;

[0015] The first filter press is used to receive the first pre-treatment mixed liquid and perform mud-water separation to obtain a first pre-treatment 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 mixed liquid;

[0017] The second filter press is used to receive the second pre-treatment mixed liquid and perform mud-water separation to obtain a second pre-treatment 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 comprises a third reaction tank for receiving the pre-treatment liquid and performing an acidification reaction to obtain an acidified pre-treatment liquid;

[0020] The ultrafiltration device is used to receive the acidified pre-treatment liquid and perform ultrafiltration to obtain the reverse osmosis treated liquid.

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

[0022] Preferably, it also includes an iron phosphate sludge pool for receiving the iron phosphate sludge generated by the mud-water separation of the first filter press; and / or,

[0023] It also includes a heavy metal sludge pool for receiving the heavy metal sludge generated by the mud-water separation of the second filter press.

[0024] Preferably, it also includes an evaporation device for receiving the first high-concentration treated liquid produced by the first reverse osmosis device and performing evaporation and crystallization to obtain evaporated treated liquid and transport it to the second reverse osmosis device.

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

[0026] Preferably, the primary reverse osmosis device is also used to receive the second high-concentration liquid to be treated produced by the secondary reverse osmosis device.

[0027] Preferably, the precision filter is also used to receive the remaining filtrate obtained by the ultrafiltration device from the reverse osmosis treated liquid through ultrafiltration.

[0028] The lithium iron phosphate cleaning wastewater recovery and treatment system provided by the embodiment of the utility model has a simple structure, and can improve the recovery purity through a multi-step combined recovery treatment, and can further improve the overall recovery efficiency by cyclically and repeatedly recovering the products of the process steps, thereby realizing efficient and automatic recovery and treatment of the cleaning wastewater. The lithium iron phosphate cleaning wastewater recovery and treatment system is conducive to resource conservation, is suitable for large-scale applications, and can achieve cost reduction and efficiency improvement in production and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the framework structure of a lithium iron phosphate cleaning wastewater recovery and treatment system provided by an embodiment of the utility model;

[0030] Figure 2 A schematic diagram of the framework structure of another lithium iron phosphate cleaning wastewater recovery and treatment system provided by an embodiment of the utility model;

[0031] Figure 3 A flow chart of a method for recycling lithium iron phosphate cleaning wastewater provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0033] The disclosure below provides many different embodiments or examples for realizing different structures of the utility model. In order to simplify the disclosure of the utility model, the components and settings of specific examples are described below. Of course, they are merely examples, and the purpose is not to limit the utility model. In addition, the utility model can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the utility model provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the applicability of other processes and / or the use of other materials.

[0034] Please refer to Figure 1 The present invention provides a lithium iron phosphate cleaning wastewater recycling and treatment system 100, which is applied to the lithium iron phosphate material manufacturing process to recycle the lithium iron phosphate cleaning wastewater generated. The lithium iron phosphate cleaning wastewater recycling and treatment system 100 specifically includes:

[0035] The reaction tank 10 is used to receive lithium iron phosphate cleaning wastewater and perform pre-treatment reaction to obtain a pre-treatment mixed solution;

[0036] A dehydration device 20, used to receive the pre-treatment mixed liquid and perform mud-water separation to obtain a pre-treatment intermediate liquid;

[0037] A precision filter 30, used for receiving the pre-treatment intermediate liquid and performing precision filtration to obtain a pre-treatment liquid;

[0038] The ultrafiltration device 40 is used to receive the pre-treatment liquid and perform ultrafiltration to obtain a reverse osmosis treated liquid;

[0039] The primary reverse osmosis device 50 is used to receive the reverse osmosis treated liquid and perform desalination treatment to obtain a first reverse osmosis clear liquid;

[0040] The secondary reverse osmosis device 60 is used to receive the first reverse osmosis clear liquid and perform desalination treatment to obtain recycled water.

[0041] Among them, the reaction tank 10, the dehydration device 20, the precision filter 30, the ultrafiltration device 40, the primary reverse osmosis device 50, and the secondary reverse osmosis device 60 are arranged in sequence, connected to each other by pipelines, and the treated target recovery liquid is transported from the upstream device to the downstream device in sequence. In this embodiment, a chemical precipitation method is used to add an appropriate amount of chemical reagents to react with metal ions in the wastewater to generate a precipitate; the precipitate is separated from the wastewater by precipitation or filtration separation; large particles of metal precipitates are removed by precision filtration; the impurities in the water remaining after the sand filter can be intercepted by the ultrafiltration retention pore size of 0.1 microns; the water effluent through the ultrafiltration membrane meets the reverse osmosis water pollution index (SDI) ≤ 3; and then through the primary reverse osmosis and the secondary reverse osmosis to achieve high-definition water recovery, meet the water purity requirements; and thus achieve efficient recovery of lithium iron phosphate cleaning wastewater.

[0042] Among them, the precision filter 30 adopts a new type of low-pressure backwash liquid filtration equipment, combining surface filtration technology, industrial automatic control technology and valve technology to realize surface technology automation. Its filtration method is positive pressure, and the filter membrane is used to filter solid particles and suspended matter in the liquid, which can make the solid particles and suspended matter in the liquid removed at a rate of up to 99%. Its specific working principle includes: filtration: the liquid to be filtered is pumped into the lower barrel of the filter through the liquid inlet pump, and the clear liquid enters the upper barrel through the filter element, and the solid matter in the liquid is trapped on the surface of the filter membrane to form a filter cake; backwashing: negative pressure is formed in the barrel within a few seconds after the backwash valve is opened, so that the clear liquid flows back and all the filter cakes fall off the surface of the filter membrane; sedimentation: under the action of gravity, a large amount of filter cakes vertically settle in the turbid liquid of the lower barrel, and naturally accumulate toward the slag discharge port when it reaches the conical part; slag discharge: when the slag discharge port is opened, the slag cake accumulated in the slag discharge port is quickly discharged, and at the same time, the residual mud cake retained on the surface of the filter element is separated from the filter membrane surface through secondary backwashing.

[0043] The ultrafiltration device 40 is used as a pre-treatment for reverse osmosis to remove suspended particles, colloids, microorganisms, etc. in water. Under the action of water pressure, water molecules and small molecules pass through the ultrafiltration membrane, and suspended particles, colloids, microorganisms, etc. in water are intercepted on the surface of the ultrafiltration membrane. Since the micropores on the ultrafiltration membrane are very small, various suspended particles, colloids, bacteria and macromolecular organic matter larger than the pore size can be effectively removed to ensure that the water quality SDI entering the reverse osmosis device meets the requirements. The ultrafiltration device 40 adopts integrated device equipment, that is, the membrane, pipeline, valve, instrument and other equipment are integrated on the integrated frame. All system pipelines and equipment have completed equipment operation tests, pipeline pressure tests and electrical tests before leaving the factory. After being transported to the site, it only needs to connect the import and export pipelines, power supply and automatic control cables to be put into use, saving the on-site construction and commissioning cycle.

[0044] Among them, the reverse osmosis method is to use the property of the reverse osmosis membrane (artificial semipermeable membrane) that can selectively only pass through the solvent (usually water) and intercept the solute (soluble salts, colloids, suspended solids, etc.), and use the pressure difference on both sides of the membrane as the driving force to overcome the osmotic pressure of the solvent, so that the solvent passes through the reverse osmosis membrane to achieve the membrane process of separating the liquid mixture. Generally, the interception rate of a single seawater reverse osmosis membrane element can reach more than 99.7%, the interception rate of a single brackish water reverse osmosis membrane element can reach more than 99.4%, and the interception rate of a single low-pressure reverse osmosis membrane element can reach more than 98.6%. In this embodiment, in order to improve the recovery rate of the reverse osmosis system, the reverse osmosis devices are arranged in series, so that the interception rate of the system will be lower than the interception rate of a single reverse osmosis membrane element. The first-stage reverse osmosis can remove more than 98% of soluble salts and more than 99% of colloidal microorganisms and organic matter from water, and the second-stage reverse osmosis can remove more than 90% of soluble salts and more than 99% of colloidal microorganisms and organic matter from water.

[0045] Furthermore, the dehydration device 20 is one of a vacuum filter, a filter press, a centrifuge, a screw press, and a roller press.

[0046] Sludge dehydration can further remove interstitial water and capillary water in the sludge and reduce its volume. After dehydration, the moisture content of the sludge can be reduced to 70% to 80%, and its volume is 1 / 10 to 1 / 4 of the original volume, which is conducive to subsequent transportation and treatment. The mechanical dehydration methods of sludge include filtration dehydration, centrifugal dehydration and press dehydration. Filtration dehydration includes vacuum filtration and pressure filtration (filter press); centrifugal dehydration is dehydration with a centrifuge; press dehydration is dehydration with a screw press or a roller press, and filter press and centrifugal dehydration methods are commonly used. Sludge filtration dehydration uses the pressure difference on both sides of the filter medium as the driving force, so that the sludge water is forced to pass through the filter medium to form a filtrate, and the solid particles are trapped on the medium to form a filter cake, thereby achieving the purpose of sludge dehydration. The plate and frame filter press was the first machine used for chemical dehydration. Although the plate and frame filter press is generally operated intermittently, requires large investment in infrastructure equipment, and has low filtration capacity, it has the advantages of large filtration driving force, high solid content of filter cake, clear filtrate, high solid recovery rate, and low consumption of conditioning chemicals. In the subsequent embodiments, a filter press is used for dehydration treatment.

[0047] Please refer to Figure 2 Further, the reaction tank 10 includes a first reaction tank 11 and a second reaction tank 12, and the dehydration device 20 includes a first filter press 21 and a second filter press 22, wherein,

[0048] 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 mixed solution;

[0049] The first filter press 21 is used to receive the first pre-treatment mixed liquid and perform mud-water separation to obtain a first pre-treatment intermediate liquid;

[0050] The second reaction tank 12 is used to receive the first pre-treatment intermediate liquid and perform a second pre-treatment reaction to obtain a second pre-treatment mixed liquid;

[0051] The second filter press 22 is used to receive the second pre-treated mixed liquid and perform mud-water separation to obtain a second pre-treated intermediate liquid;

[0052] The precision filter 30 is used to receive the second pre-treatment intermediate liquid and perform precision filtration to obtain the pre-treatment liquid.

[0053] In this embodiment, two groups of continuous reaction tanks 10 and filter presses 20 are set to complete two groups of chemical precipitation reactions respectively, and the two types of substances in the lithium iron phosphate cleaning wastewater are precipitated and transformed. Specifically, the lithium iron phosphate wastewater first enters the first reaction tank 11, and hydrogen peroxide, ferrous sulfate and sulfuric acid are added to react to remove most of the iron phosphate, and the first filter press 21 is used to separate mud and water. The clear liquid of the first filter press 21 enters the second reaction tank 12, and alkali is added to the second reaction tank 12 to adjust the pH to alkaline, and the heavy metals in the water are precipitated, and then the second filter press 22 is used to separate mud and water. After two steps of precipitation reaction and mud and water separation, most of the metal ion impurities are removed.

[0054] Furthermore, the reaction tank 10 further includes a third reaction tank 13, which is used to receive the pre-treatment liquid and perform an acidification reaction to obtain an acidified pre-treatment liquid;

[0055] The ultrafiltration device 40 is used to receive the acidified pre-treatment liquid and perform ultrafiltration to obtain the reverse osmosis treated liquid.

[0056] In this embodiment, the pH of the ultrafiltration water is adjusted to 4-5 to ensure that the reverse osmosis can operate under slightly acidic conditions, so as to effectively reduce the scaling tendency of the reverse osmosis membrane.

[0057] Furthermore, a backwash collection box 70 is included, which is used to collect the backwash liquid remaining after ultrafiltration in the ultrafiltration device 40 and transport it to the second reaction tank 12.

[0058] In this embodiment, the ultrafiltration membrane is designed specifically for removing particulates. Water is pressurized and then filtered through the membrane. Since the pores on the membrane are very small, this technology can effectively remove all suspended matter, including microorganisms. These pollutants will accumulate on the membrane surface, so it is necessary to periodically use reverse water flow to remove the pollutants (i.e., backwashing).

[0059] According to the water quality, the system adopts cross-flow filtration. Since most of the ultrafiltration concentrated water and backwashing drainage water are suspended objects and colloids, and the content of other ions has not increased or decreased, the concentrated water and backwashing drainage water of the ultrafiltration device 40 are returned to the front-stage reaction tank for recycling, ensuring higher economic efficiency of the system.

[0060] Furthermore, it also includes an iron phosphate sludge pool 80 for receiving the iron phosphate sludge generated by the mud-water separation of the first filter press 11; and / or,

[0061] It also includes a heavy metal sludge pool 90 for receiving the heavy metal sludge generated by the mud-water separation of the second filter press 12 .

[0062] In this embodiment, the iron phosphate sludge and heavy metal sludge generated in the pre-treatment are collected for subsequent treatment to avoid secondary pollution.

[0063] Furthermore, it also includes an evaporation device 95 for receiving the first high-concentration treated liquid produced by the primary reverse osmosis device 50 and performing evaporation and crystallization to obtain an evaporated treated liquid and transport it to the secondary reverse osmosis device 60 .

[0064] Among them, evaporators are divided into evaporation concentrators and evaporation crystallizers according to different uses. The names of evaporators will be different due to the different processes used, but they are basically the same. The main purpose of the evaporator is to evaporate the non-volatile solutes contained in the solution, boil the solution, vaporize it and remove it, thereby increasing the solute concentration in the solution.

[0065] Furthermore, the evaporation device 95 is a multiple effect evaporation device or a steam mechanical recompression (MVR) evaporation device. The difference between these two types of evaporation processes is mainly the difference in the use of steam.

[0066] In this embodiment, the multiple-effect evaporator specifically adopts a triple-effect evaporator, which is composed of three groups of heaters, three groups of separators, preheaters, pump groups, thickeners, mother liquid tanks, centrifuges, electrical instrument controls, valves, pipelines, etc. The three groups of evaporators are operated in series to form a triple-effect crystallization evaporator. The entire evaporation system adopts a production method of continuous feeding and continuous discharging. High-salt wastewater first enters a first-effect forced circulation crystallization evaporator. The crystallization evaporator is equipped with a circulation pump to pump the wastewater into the evaporation heat exchange chamber. In the evaporation heat exchange chamber, the external steam liquefaction generates latent heat of vaporization to heat the wastewater. Due to the high pressure in the evaporation heat exchange chamber, the wastewater is heated to superheat in the evaporation heat exchange chamber at a pressure higher than the normal liquid boiling point. After the heated liquid enters the crystallization evaporation chamber, the pressure of the wastewater drops rapidly, causing part of the wastewater to flash, or boil rapidly. The steam after the wastewater is evaporated enters the second-effect forced circulation evaporator as a power steam to heat the second-effect evaporator, and the unevaporated wastewater and salt are temporarily stored in the crystallization evaporation chamber. The first-effect, second-effect, and third-effect forced circulation evaporators are connected through a balance pipe. Under the action of negative pressure, high-salt wastewater flows from the first effect to the second effect and the third effect in turn. The wastewater is continuously evaporated, and the salt concentration in the wastewater becomes higher and higher. When the salt content in the wastewater exceeds the saturation state, the salt in the water will continuously precipitate and enter the salt collection chamber at the bottom of the evaporation crystallization chamber. The salt suction pump continuously sends the salt-containing wastewater to the vortex salt separator. In the vortex salt separator, the solid salt is separated and enters the salt storage tank. The separated wastewater enters the second-effect forced circulation evaporator for heating. The whole process is repeated to achieve the final separation of water and salt.

[0067] In addition, MVR evaporation is composed of heater, separator, preheater, steam compressor, pump group, thickener, mother liquid tank, centrifuge, electrical instrument control and valves, pipelines, etc.

[0068] The working process of the MVR evaporator is that the low-temperature steam compressor compresses the secondary steam generated by the evaporation of the material to do work, increase the pressure and temperature of the secondary steam, increase the thermal enthalpy, convert the electrical energy into thermal energy, and the heated secondary steam returns to the evaporation system to heat the material, and then enters the heat exchanger for condensation to make full use of the latent heat of the steam. Except for the start-up, no steam is required during the entire evaporation process.

[0069] The secondary steam compressed by the compressor is sent to the heating chamber of the evaporator for use as heating steam to keep the liquid in a boiling state, while the heating steam itself is condensed into water and discharged from the system. The heated material is discharged from the system as the final product after being vaporized and concentrated. In the entire MVR evaporation system, the steam that was originally to be discarded has a use value, recovering latent heat, and the efficiency can be greatly improved by more than 50%.

[0070] The most critical part of the MVR evaporator is the steam compressor, which is the key equipment of the heat recovery system to increase the temperature and pressure of the steam by compressing the generated steam. Its function is to pressurize and heat the low-pressure (or low-temperature) steam to meet the temperature and pressure requirements of the process or engineering. Mechanical steam compressors are divided into Roots steam compression fans and centrifugal steam compression fans, and centrifugal steam compression fans are divided into ordinary centrifugal compression fans and single-stage high-speed centrifugal steam compressors. Different types of fans have different characteristics and have their own advantages under different application conditions.

[0071] 1) Roots compressor is a positive displacement blower with a higher compression ratio than ordinary centrifugal compressors. Roots steam compressors have better stability due to their lower speed.

[0072] Generally speaking, the speed of Roots steam compression blower is between 980 and 1450 r / min, the speed of ordinary centrifugal steam compression blower is between 6000 and 9000 r / min, and the maximum speed of single-stage high-pressure centrifugal blower can reach 30000 r / min.

[0073] Of course, the disadvantages of Roots blower are also obvious. Its inherent defects are small single-stage volume flow, low efficiency and short maintenance cycle (generally 2000h / time). At the same time, the noise spectrum of Roots blower is relatively wide, with low and medium frequency noise of 63-8000HZ as the main component. The noise during operation is as high as over 100 decibels, which poses a great harm to personnel health.

[0074] 2) The compression temperature rise of ordinary centrifugal steam compression fans is generally 8 to 10 degrees Celsius. Currently, the main application models are basically imported compression fans, which have the advantages of high efficiency and stable performance.

[0075] When a higher compression ratio is required, two centrifugal steam compression fans can be connected in series to obtain a higher compression temperature rise, but at the same time, the efficiency of the fan will decrease.

[0076] Generally speaking, boiling occurs during the evaporation process, and some solutions even boil very high. In this case, two or three-stage fans need to be used in series.

[0077] 3) The salient features of the single-stage high-speed centrifugal compression fan are high fan speed and high compression ratio, resulting in a higher compression temperature rise. At the same time, it also has high efficiency, low energy consumption, and larger processing capacity, so it has a wider range of applications.

[0078] At present, single-stage high-speed centrifugal compressor fans are mainly domestically produced, with relatively mature technology and equipment maintenance cycles of more than 18 months. The noise frequency of single-stage high-speed centrifugal compressor fans is between 8000 and 12000 Hz, which is high-frequency secondary wave noise, exceeding the sensitive area of ​​human ears and not causing much harm to personnel.

[0079] Furthermore, the primary reverse osmosis device 50 is also used to receive the second high-concentration liquid to be treated produced by the secondary reverse osmosis device 60. In this embodiment, the high-concentration water from the secondary reverse osmosis reenters the primary reverse osmosis to achieve cyclic recovery and further improve the recovery effect.

[0080] Furthermore, the precision filter 30 is also used to receive the remaining filtrate from the reverse osmosis treated liquid obtained by ultrafiltration in the ultrafiltration device 40. In this embodiment, the remaining filtrate from ultrafiltration in the ultrafiltration device 40 re-enters the precision filtration to achieve recycling.

[0081] Please refer to Figure 3 The present utility model also provides a method for recycling and treating lithium iron phosphate cleaning wastewater, comprising the steps of:

[0082] S10, adding hydrogen peroxide (H202), ferrous sulfate (FeSO4), and sulfuric acid (H2SO4) to the lithium iron phosphate cleaning wastewater in a certain proportion, removing the precipitate after the reaction, and obtaining a first pre-treatment intermediate solution;

[0083] S20, adding sodium hydroxide to the first pretreatment intermediate solution to adjust the pH value to alkaline, removing the precipitate after the reaction, and obtaining a second pretreatment intermediate solution;

[0084] S30, finely filtering the second pretreatment intermediate liquid to obtain a pretreatment liquid;

[0085] S40, adding sulfuric acid to the pre-treatment liquid to adjust the pH value to be acidic, and obtaining recycled water through ultrafiltration, primary reverse osmosis and secondary reverse osmosis.

[0086] Furthermore, the step S30, wherein the second pre-treatment intermediate liquid is subjected to precise filtration to obtain a pre-treatment liquid, specifically comprises:

[0087] The second pre-treatment intermediate liquid is finely filtered to obtain a pre-treatment liquid and a liquid to be returned for washing;

[0088] The step S20, adding sodium hydroxide to the first pre-treatment intermediate solution, adjusting the pH value to be alkaline, removing the precipitate after the reaction, and obtaining the second pre-treatment intermediate solution, specifically comprises:

[0089] The first pre-treatment intermediate solution and the solution to be backwashed are mixed, sodium hydroxide is added, the pH value is adjusted to be alkaline, and the precipitate is removed after the reaction to obtain a second pre-treatment intermediate solution.

[0090] Furthermore, the clear liquid obtained in the primary reverse osmosis process is subjected to the secondary reverse osmosis, and the first high-concentration liquid obtained in the primary reverse osmosis process is evaporated and crystallized to obtain an evaporated treated liquid for the secondary reverse osmosis.

[0091] Furthermore, the clear liquid obtained in the secondary reverse osmosis process is the recovered water, and the second high-concentrate liquid obtained in the secondary reverse osmosis process is subjected to the primary reverse osmosis again.

[0092] Furthermore, the clear liquid obtained in the ultrafiltration process is subjected to the primary reverse osmosis, and the filtrate to be returned obtained in the ultrafiltration process is subjected to the precision filtration again.

[0093] Furthermore, the molar ratio of the lithium iron phosphate cleaning wastewater to the hydrogen peroxide, the ferrous sulfate, and the sulfuric acid satisfies n(wastewater):n(H202):n(FeSO4):n(H2SO4)=1:0.221:0.321:0.11.

[0094] Furthermore, in the step S20, the pH value is adjusted to 8-11; in the step S40, the pH value is adjusted to 4-5.

[0095] This system combines the characteristics of lithium iron phosphate wastewater and superimposes various influencing factors to optimize the entire system.

[0096] This system adopts a forced circulation evaporation process. The flow rate of the material in the heat exchange tube reaches 1.5-2m / s. At this flow rate, tube blockage is not likely to occur, and the occurrence of tube blockage can be effectively prevented.

[0097] During the evaporation process, the material is heated by the heater under the push of the circulation pump, rises along the central tube of the evaporation chamber, evaporates on the surface of the liquid, produces maximum supersaturation, and can achieve the purpose of effective separation.

[0098] The steam compressor is one of the core equipment of the MVR device. 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.

[0099] MVR steam compressor is based on aerodynamic theory, using advanced fluid design software calculation and CFD flow field analysis, and the efficiency of the three-dimensional flow impeller reaches more than 92%. This series of products has the advantages of high efficiency, compact structure, stable operation, wide range of working conditions, simple operation, etc. The performance of the whole machine has reached the advanced level of similar products at home and abroad, and is widely used in petroleum, chemical, food, pharmaceutical, sewage treatment, beverage, additives and other industries.

[0100] The lithium iron phosphate cleaning wastewater recycling and treatment system provided by the embodiment of the utility model has a simple structure, and can improve the recovery purity through a multi-step combined recycling treatment, and can further improve the overall recycling efficiency by cyclically and repeatedly recycling the products of the process steps, thereby realizing efficient and automatic recycling and treatment of the cleaning wastewater. The lithium iron phosphate cleaning wastewater recycling and treatment system and recycling and treatment method are conducive to resource conservation, are suitable for large-scale applications, and can achieve cost reduction and efficiency improvement in production and manufacturing.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0102] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A lithium iron phosphate cleaning wastewater recovery and treatment system, characterized in that: include: A reaction tank, used for receiving lithium iron phosphate cleaning wastewater and performing a pre-treatment reaction to obtain a pre-treatment mixed solution; A dehydration device, used for receiving the pre-treatment mixed liquid and performing mud-water separation to obtain a pre-treatment intermediate liquid; A precision filter, used for receiving the pre-treatment intermediate liquid and performing precision filtration to obtain a pre-treatment liquid; An ultrafiltration device, used for receiving the pre-treatment liquid and performing ultrafiltration to obtain a reverse osmosis treated liquid; A primary reverse osmosis device, used for receiving the reverse osmosis treated liquid and performing desalination treatment to obtain a first reverse osmosis clear liquid; The secondary reverse osmosis device is used to receive the first reverse osmosis clear liquid and perform desalination treatment to obtain recycled water.

2. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 1, characterized in that: The dehydration device is one of a vacuum filter, a filter press, a centrifuge, a screw press, and a roller press.

3. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 1, characterized in that: The reaction tank includes a first reaction tank and a second reaction tank, and the dehydration device includes a first filter press and a second filter press, wherein: The first reaction tank is used to receive lithium iron phosphate cleaning wastewater and perform a first pretreatment reaction to obtain a first pretreatment mixed solution; The first filter press is used to receive the first pre-treatment mixed liquid and perform mud-water separation to obtain a first pre-treatment intermediate liquid; The second reaction tank is used to receive the first pretreatment intermediate liquid and perform a second pretreatment reaction to obtain a second pretreatment mixed liquid; The second filter press is used to receive the second pre-treatment mixed liquid and perform mud-water separation to obtain a second pre-treatment intermediate liquid; The precision filter is used to receive the second pretreatment intermediate liquid and perform precision filtration to obtain the pretreatment liquid.

4. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 3, characterized in that: The reaction tank also includes a third reaction tank, which is used to receive the pre-treatment liquid and perform an acidification reaction to obtain an acidified pre-treatment liquid; The ultrafiltration device is used to receive the acidified pre-treatment liquid and perform ultrafiltration to obtain the reverse osmosis treated liquid.

5. The recycling system according to claim 4, characterized in that: It also includes a backwash collection box for collecting the backwash liquid remaining after ultrafiltration in the ultrafiltration device and transporting it to the second reaction tank.

6. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 3, characterized in that: It also includes an iron phosphate sludge pool for receiving the iron phosphate sludge generated by the mud and water separation of the first filter press; and / or, It also includes a heavy metal sludge pool for receiving the heavy metal sludge generated by the mud-water separation of the second filter press.

7. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 3, characterized in that: It also includes an evaporation device for receiving the first high-concentration treated liquid produced by the first reverse osmosis device and performing evaporation and crystallization to obtain an evaporated treated liquid and transport it to the second reverse osmosis device.

8. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 7, characterized in that: The evaporation device is a multiple-effect evaporation device or an MVR evaporation device.

9. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 7, characterized in that: The primary reverse osmosis device is also used to receive the second high-concentration liquid to be treated produced by the secondary reverse osmosis device.

10. The lithium iron phosphate cleaning wastewater recovery and treatment system according to claim 1, characterized in that: The precision filter is also used to receive the remaining filtrate obtained by the ultrafiltration device through ultrafiltration of the reverse osmosis treated liquid.

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