Lithium battery production wastewater treatment system and process

Abstract

The invention belongs to the technical field of lithium battery production wastewater treatment, and particularly relates to a lithium battery production wastewater treatment system and process. The treatment system for the lithium battery production wastewater comprises a reaction zone, a coagulation zone, a flocculation zone and an inclined tube settling zone which are sequentially communicated along the flowing direction of the wastewater, and further comprises a mud and sand return pipe, a hydrocyclone for separating micro sand and sludge and a sludge level meter, one end of the mud and sand return pipe is communicated with the bottom of the inclined pipe settling zone, and the other end of the mud and sand return pipe is respectively communicated with the flocculation zone and the front end of the hydrocyclone; an underflow port at the lower end of the hydrocyclone is communicated with the flocculation zone, and the upper end of the hydrocyclone is communicated with a sludge discharge pipe; the mud level meter is arranged in the inclined tube settling zone and is used for monitoring the mud and sand deposition thickness of the inclined tube settling zone. The treatment system and process have a good treatment effect on the lithium battery production wastewater, and finally, Ni in the effluent can be controlled to be less than 0.5 mg / L, and SS in the effluent can be controlled to be less than 10mg / L.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery production wastewater treatment, and specifically relates to a lithium battery production wastewater treatment system and process. Background Art

[0002] Lithium battery wastewater is wastewater containing various pollutants generated during the production of lithium-ion batteries and related processes. Lithium-ion batteries have the advantages of high energy density and long life, and are widely used in electronic equipment, electric vehicles and other fields. With the continuous growth of demand for lithium-ion batteries, the treatment of lithium-ion wastewater has also received increasing attention. The wastewater generated by lithium battery processes has the following main characteristics:

[0003] Complex composition: Lithium battery wastewater contains a variety of pollutants, including heavy metal ions (such as cobalt, nickel, manganese, lithium, etc.), acids, alkalis, organic matter, fluorides, etc. These pollutants are of various types and have different chemical properties, making them difficult to treat. High oil content: The production of wastewater is accompanied by extraction and other processes. The extractant is mostly an organic solvent. Even after passing through the oil removal device, there is still a small amount of residue, which is difficult to remove, increasing the difficulty of wastewater treatment. High heavy metal content: A large amount of wastewater containing heavy metal ions will be generated during the production of lithium-ion batteries and the recycling of waste lithium-ion batteries. These heavy metal ions are toxic and difficult to degrade in the environment. If they are discharged directly without treatment, they will cause serious pollution to the soil, water bodies and ecological environment, and will also enter the human body through the food chain, endangering human health. High magnesium hardness: The raw water contains a large amount of magnesium hardness, which makes it very easy to scale, increasing the difficulty of treatment; large changes in pH: Acids, alkalis and other chemicals are used in the production of lithium-ion batteries, so the pH of lithium-ion wastewater varies greatly. For example, an acid solution may be used in the preparation of positive electrode materials, while an alkaline solution may be used in the preparation of negative electrode materials, resulting in unstable pH of the wastewater. Large fluctuations in water volume: The production scale and production process of lithium-ion battery manufacturers are different, and the amount of wastewater generated will also vary. At the same time, the amount and time of recycling of used lithium-ion batteries are also uncertain, resulting in large fluctuations in the amount of lithium-ion wastewater. This fluctuation in water volume poses certain challenges to the design and operation of wastewater treatment systems.

[0004] Furthermore, there are many problems with the current conventional lithium battery production wastewater treatment system: ① High operating costs, large floor space, poor impact resistance, and difficulty in timely adjustment when water volume and water quality fluctuate, resulting in a significant excess of heavy metal ions in the effluent; ② The treatment effect of Ni ions in heavy metal ions is poor, and the nickel ions in the influent fluctuate greatly, with a content of 30-500 mg / L. When the nickel ions in the raw water are >300 mg / L, it is difficult to remove them to less than 1 mg / L; ③ Nickel in the wastewater can be recycled after precipitation. The wastewater contains a certain amount of extractant, which will float on the water surface in the sedimentation tank. The floating oil adsorbs the flocs, causing the flocs on the water surface to continuously agglomerate, which not only affects the sedimentation effect, but also makes the sludge impossible to be recycled. ④ Due to the characteristics of Ni precipitation itself, the flocs produced are lighter, the residence time required for precipitation is longer, the tank body is large, and the influent fluctuations easily lead to mud overturning, resulting in excess Ni and SS in the effluent.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a lithium battery production wastewater treatment system and process, which is aimed at treating lithium battery production wastewater with high heavy metal content, complex composition, high oil content and great treatment difficulty, and solving the problems of unstable effluent, high operating cost, poor treatment effect, excessive effluent and inability to recycle some sludge in the current treatment system.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A lithium battery production wastewater treatment system, comprising a reaction zone, a coagulation zone, a flocculation zone and an inclined tube sedimentation zone which are sequentially connected along the flow direction of the wastewater, and also comprising a mud and sand return pipe, a hydrocyclone for separating micro-sand and sludge, and a mud level meter;

[0009] One end of the mud and sand return pipe is connected to the bottom of the inclined tube sedimentation zone, and the other end is respectively connected to the flocculation zone and the front end of the hydrocyclone; the bottom flow outlet at the lower end of the hydrocyclone is connected to the flocculation zone, and the upper end is connected to the sludge discharge pipe; the mud level meter is arranged in the inclined tube sedimentation zone to monitor the mud and sand deposition thickness in the inclined tube sedimentation zone.

[0010] Furthermore, a reflux valve is provided on the pipeline connecting the mud and sand return pipe with the flocculation zone, and a cyclone valve is provided on the pipeline connecting the mud and sand return pipe with the front end of the hydrocyclone; the mud level meter is connected to a DCS remote control system, and the DCS remote control system controls the stroke switching of the reflux valve and the cyclone valve.

[0011] Furthermore, the reaction zone is provided with a treatment agent dosing pipeline for dosing the treatment agent; a dosing flow meter is installed on the treatment agent dosing pipeline;

[0012] And / or, the reaction zone is provided with a pH online detector for monitoring the pH value of the reaction zone.

[0013] Furthermore, the flocculation zone is provided with a sand adding port for initially adding micro-sand;

[0014] And / or, the coagulation zone is provided with a coagulant addition pipeline; and / or, the front end of the inclined tube sedimentation zone is provided with a skimming pipe device for collecting floating oil and floating mud.

[0015] In addition, the present invention also provides a treatment process for lithium battery production wastewater, which adopts the above-mentioned treatment system and includes the following steps:

[0016] Step 1: Add a treatment agent to the reaction zone. After the wastewater reacts with the treatment agent, the complexed nickel ions are converted into free nickel ions. The wastewater is then sent to the coagulation zone, and a coagulant is added to perform a coagulation reaction to aggregate the suspended matter and pollutants in the water.

[0017] Step 2: The wastewater after coagulation treatment is sent to the flocculation area, and flocculants are added for flocculation reaction, and micro sand is added at the same time to make the suspended matter form larger flocs;

[0018] Step 3: The wastewater after flocculation treatment passes through the inclined tube sedimentation area. After the mud and sand are settled, the sedimentation thickness is controlled. When the mud level is low or higher than the set sedimentation thickness, the mud and sand return along the mud and sand return pipe. According to the mud level monitored by the mud level meter, the mud and sand are controlled to flow back to the hydrocyclone or flocculation area. The effluent meets the discharge standards.

[0019] Further, in step S3, the sedimentation thickness of mud and sand is controlled to be 10-15% of the height of the inclined tube sedimentation zone; when the mud level is lower than 10% of the height of the inclined tube sedimentation zone, the return valve is opened and the cyclone valve is closed, and all the mud and sand are returned to the flocculation zone; when the mud level is higher than 15% of the height of the inclined tube sedimentation zone, the cyclone valve is opened and the return valve is closed, and the micro-sand in the mud and sand enters the flocculation zone through the low flow port at the lower end of the hydrocyclone, and the sludge in the mud and sand is discharged from the sludge external discharge pipe.

[0020] Further, in step S1, the treatment agent is a mixture of alkali solution and sodium hypochlorite; the dosage ratio of the alkali solution to the sodium hypochlorite is 1:2;

[0021] and / or, the pH value of the reaction zone is controlled at 8.5 to 9.5;

[0022] And / or, after adding the treating agent into the reaction zone, rapidly stir at a rate of 30 rpm for 10 to 15 minutes.

[0023] Furthermore, in step S1, the dosage of the coagulant is 50-55 mg / L; and / or, the coagulant is ferric chloride; and / or, after the coagulant is added, rapid stirring is performed at a rate of 30 rpm for 10-15 min.

[0024] Further, in step S2, the dosage of the flocculant is 3-3.5 mg / L; and / or, the flocculant is a PAM flocculant; and / or, after adding the flocculant, the mixture is slowly stirred at a speed of 20 rpm for 10-15 min.

[0025] Furthermore, the amount of fine sand input from the sand adding port for the first time is 200-220 kg / ㎡ of the inclined pipe area.

[0026] Compared with the closest prior art, the technical solution provided by the present invention has the following excellent effects:

[0027] (1) The treatment system and process of the present invention have a good treatment effect on lithium battery production wastewater, and can ultimately control the effluent Ni to below 0.5 mg / L and the effluent SS to below 10 mg / L.

[0028] (2) By strictly controlling the addition ratio of alkali solution and sodium hypochlorite, the steady state of complex nickel ions is destroyed and divalent nickel ions are oxidized into trivalent nickel ions, thereby forming trivalent nickel ion precipitation, which removes the complex nickel ions and accelerates the reaction rate.

[0029] (3) By setting a sand adding port in the flocculation zone to add micro sand, the sedimentation rate of solid particles is increased, the sediment is heavier, it is not easy to combine with floating oil, and the formation of scum is slowed down.

[0030] (4) By using a mud level meter to control the return of mud and sand to the hydrocyclone or flocculation zone, on the one hand, the amount of micro-sand and flocculent mass in the flocculation zone can be adjusted to ensure the flocculation effect; on the other hand, the difficulty of sludge recovery and operating costs can be reduced.

[0031] (5) The present invention improves the impact resistance and treatment efficiency of the entire treatment system by improving and upgrading the existing system, ensuring stable effluent, shortening the sedimentation time, reducing the volume of the pool, occupying a small area, and reducing the operating cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0033] Figure 1 This is a flow chart of a system for treating lithium battery production wastewater according to an embodiment of the present invention.

[0034] In the figure: 1. Reaction zone; 11. Treatment agent addition pipeline; 2. Coagulation zone; 21. Coagulant addition pipeline; 3. Flocculation zone; 31. Flocculant addition pipe; 4. Inclined tube sedimentation zone; 5. Mud and sand return pipe; 6. Hydrocyclone; 7. Mud level meter; 8. Reflux pump; 9. Sludge discharge pipe; 10. Reflux valve; 11. Cyclone valve; 12. Slag skimming pipe device. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0036] In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, they can be fixed connections or detachable connections; they can be directly connected or indirectly connected through intermediate components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0037] According to a first aspect of the present invention, a system for treating lithium battery production wastewater is provided. Figure 1 As shown, it includes a reaction zone 1, a coagulation zone 2, a flocculation zone 3 and an inclined tube sedimentation zone 4 which are connected in sequence along the flow direction of the wastewater; the reaction zone 1 is provided with a treatment agent addition pipeline 11 for adding the treatment agent, and a pH online detector is also provided as above for monitoring the pH value of the reaction zone; the coagulation zone 2 is provided with a coagulant addition pipeline 21, and the addition amount is automatically controlled according to the water inlet, so that the heavy metal ions in the water are clustered into flocs; the wastewater passing through the coagulation zone 2 enters the flocculation zone 3 through the bottom pipe, the flocculation zone 3 is provided with a sand addition port for the first addition of micro-sand, and is also provided with a flocculant addition pipe 31, a guide tube is arranged in the flocculation zone 3, and the flocculant addition pipe extends to the bottom position of the guide tube, and the wastewater passing through the flocculation zone 3 flows into the inclined tube sedimentation zone 4 by the inclined wall push flow pool, and the flocs are precipitated under the action of the inclined tube and collected by the mud collecting bucket in the center of the sedimentation zone.

[0038] In addition, the present invention is provided with a skimming pipe device 12 at the front end of the inclined tube sedimentation area 4. After the floating oil and floating mud are collected by the skimming pipe, they flow into the mud collection bucket by gravity. The mud collection bucket sludge is discharged to the designated location by using the sludge. It should be noted that the skimming pipe device of the present invention is a conventional device in the field, mainly composed of a slag removal pipe, a worm gear, a support, an end bearing, etc., a certain angle opening is opened on the pipe, and the two ends of the sewage pipe are fixed with a bearing seat. When skimming, the handwheel worm mechanism is rotated to drive the slag removal pipe to rotate a certain angle, so that the notch is immersed below the slag layer, and the floating slag and floating oil automatically flow into the pipe and are discharged. After skimming the oil residue, the handwheel is rotated in the opposite direction to stop the notch from discharging upward. The skimming pipe can be installed horizontally, which is easy to install. Features of the skimming pipe: ① stable and labor-saving; ② uniform overflow, slight changes in the liquid level, which does not affect the use effect; ③ simple structure, high rigidity, easy installation and use; ④ simple operation, continuous or intermittent mud discharge can be carried out as needed.

[0039] Specifically, the treatment system of the present invention also includes a mud and sand return pipe 5, a hydrocyclone 6 for separating micro-sand and sludge, and a mud level meter 7; since the sludge contains micro-sand, direct discharge into the sludge pool will affect subsequent treatment, such as causing equipment wear and clogging of the pipeline, and direct discharge will also lead to waste of micro-sand, so it is necessary to separate the micro-sand in the sludge, so a hydrocyclone 6 is arranged on the top of the flocculation zone 3, wherein one end of the mud and sand return pipe 5 is connected to the bottom of the inclined tube sedimentation zone 4, and is used to return the mud and sand (sludge containing micro-sand) precipitated in the inclined tube sedimentation zone, and a reflux pump 8 is arranged on the mud and sand return pipe 5; the other end of the mud and sand return pipe 5 is respectively connected to the flocculation zone 3 and the front end of the hydrocyclone 6; the mud and sand return pipe 5 can be selectively divided into two paths, one path enters the hydrocyclone 6, and the other path enters the flocculation tank 3; the bottom flow outlet at the lower end of the hydrocyclone 6 is connected to the flocculation zone 3, and the upper end is connected to the sludge discharge pipe 9.

[0040] When mud and sand enter the hydrocyclone 6, the cyclone effect is used to accelerate the sedimentation of micro-sand in the sludge. Most of the sludge is discharged from the sludge external discharge pipe 9 connected to the upper end of the cyclone for subsequent treatment; and the micro-sand and a very small part of the sludge enter the bottom flow outlet at the lower end of the hydrocyclone 8, and are then sent to the flocculation zone 3, which is conducive to the formation of relatively large alum flocs in the flocculation zone 3, and can also make the micro-sand reused, thereby reducing the cost of sewage treatment.

[0041] Furthermore, the mud level meter 7 is arranged in the inclined tube sedimentation area 4 to monitor the thickness of mud and sand deposition in the inclined tube sedimentation area 4. Based on this scheme, as a preferred embodiment, a return valve 10 is provided on the pipeline connecting the mud and sand return pipe 5 with the flocculation area 3, and a cyclone valve 11 is provided on the pipeline connecting the mud and sand return pipe 5 with the front end of the hydrocyclone 6; the mud level meter 7 is connected to the DSC remote control system, and the monitored mud and sand deposition thickness in the inclined tube sedimentation area 4 is fed back to the DSC remote control system, and the DSC remote control system controls the stroke switching of the return valve 10 and the cyclone valve 11 according to the received data information, thereby realizing automatic control.

[0042] According to the second aspect of the present invention, in order to further understand the lithium battery production wastewater treatment system of the present invention, the present invention also provides a lithium battery production wastewater treatment process, comprising the following steps:

[0043] Step 1, adding a treatment agent to the reaction zone, the treatment agent used in the present invention is a mixture of alkali solution and sodium hypochlorite; wherein the ratio of the addition amount of alkali solution to sodium hypochlorite is 1:2; adding alkali solution and sodium hypochlorite to the reaction zone, sodium hypochlorite is used to destroy the steady state of complexed nickel ions and oxidize divalent nickel ions into trivalent nickel ions, thereby reacting with hydroxide to form flocculation precipitation, converting complexed nickel ions into free nickel ions while also accelerating the reaction rate. The dosage of reagent is controlled by the dosing flowmeter on the dosing pipe. The alkali solution and hyposodium are mixed in advance in the dosing tank to control the alkali solution: hyposodium = 1:2. If the hyposodium dosage is too much, the reagent will be wasted and the excess oxidant cannot be consumed. Secondly, the hyposodium decomposes and produces gas, which will aggravate the floating phenomenon of flocs. Too little dosage will affect the nickel removal effect. Trivalent nickel ions are easier to precipitate than divalent nickel ions. Therefore, the reagent ratio needs to be strictly controlled. At the same time, the reaction zone controls the dosage of alkali solution to adjust the pH value. The pH value is controlled at 8.5-9.5. (For example, 8.5, 9, 9.5), the wastewater contains a certain amount of magnesium hardness. If the pH value is controlled to be high, magnesium hardness will precipitate. First, the subsequent process is prone to scaling and clogging. Second, it increases the difficulty of nickel recovery in the sludge. There are many impurities. If the pH is low, the nickel removal effect is poor, which can easily lead to excessive nickel ions in the effluent. Therefore, the reaction pH value needs to be strictly controlled; after the wastewater reacts with the treatment agent, the complexed nickel ions are converted into free nickel ions. After the complexed nickel ions are removed, they are then sent to the coagulation area, and coagulants are added for coagulation reaction to remove suspended matter and pollutants in the water;

[0044] Step 2: The wastewater after coagulation treatment is sent to the flocculation area, and flocculants are added for flocculation reaction. At the same time, micro sand is added to further remove suspended matter; micro sand can increase the sedimentation rate of solid particles, increase the weight of sediment, and is not easy to combine with floating oil, slowing down the formation of scum. In addition, the amount of micro sand used is related to the flocculation effect. It is necessary to strictly control the amount of micro sand added for the first time and the amount of micro sand returned to ensure the flocculation effect (for example, 200kg / ㎡ inclined tube area, 210kg / ㎡ inclined tube area, 220kg / ㎡ inclined tube area).

[0045] Step 3. The wastewater after flocculation treatment passes through the inclined tube sedimentation area. After the mud and sand are settled, the sedimentation thickness is controlled. When the mud level is low or higher than the set sedimentation thickness, the mud and sand return along the mud and sand return micro-sand for the first time from the sand adding port with an amount of 200-220kg / ㎡ inclined tube area flow tube. According to the mud level monitored by the mud level meter, the mud and sand are controlled to flow back to the hydrocyclone or flocculation area. The effluent meets the discharge standards.

[0046] Since the nickel ion content of the influent water is between 30-500mg / L and fluctuates greatly, the amount of flocs produced in the flocculation zone also changes accordingly. When the nickel ion content of the influent water is low and less flocs are produced, not only micro-sand return is required to assist sedimentation, but also a large amount of sludge return is required. At this time, the demand for sludge discharge is very small. Therefore, a mud level meter is set in the sedimentation area to characterize the amount of sediment in the incoming water. When the mud level gradually decreases, it means that the sediment in the incoming water is less. At this time, the sludge process needs to be switched from the hydrocyclone pipeline to the return pipeline to maintain the amount of flocs in the flocculation zone, otherwise it needs to be switched to the hydrocyclone pipeline.

[0047] In the above-mentioned lithium battery production wastewater treatment process, as a preferred implementation mode, in step S3, the sedimentation thickness of the mud and sand is controlled to be 10-15% (such as 10%, 11%, 12%, 13%, 14%, 15%) of the capacity of the inclined tube sedimentation zone; when the mud level is lower than 10% of the capacity of the inclined tube sedimentation zone, the return valve is opened and the cyclone valve is closed, and all the mud and sand are returned to the flocculation zone; when the mud level is higher than 15% of the capacity of the inclined tube sedimentation zone, the cyclone valve is opened and the return valve is closed, and the micro-sand in the mud and sand enters the flocculation zone through the low flow port at the lower end of the hydrocyclone, and the sludge in the mud and sand is discharged from the sludge external discharge pipe.

[0048] The sediment thickness of mud and sand is 10% as the lower limit, and the height of the scraper needs to be considered. If the lower limit is set too low, the scraper cannot hang the mud, which is equivalent to idling energy consumption, and will lead to less return sediment content and less flocs in the flocculation zone, which cannot replenish the amount of flocs in the flocculation zone, resulting in poor flocculation effect and high operating costs. When the sediment thickness of mud and sand is greater than 15%, open the cyclone valve, close the return valve, and switch the process to the cyclone. Most of the sludge will be discharged and the mud level will drop accordingly. At this time, 10-15% of the process is the cyclone process. When the mud level drops below 10%, switch to the return pipeline. At this time, there is no sludge discharge and the mud level will gradually rise. At this time, 10-15% of the process is the return pipeline. It is a dynamic balance process.

[0049] In the above-mentioned treatment process of lithium battery production wastewater, as a preferred implementation mode, in step S1, after adding the treatment agent in the reaction zone, stir rapidly at a rate of 30 rpm for 10 to 15 min (for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min); after adding the coagulant, stir rapidly at a rate of 30 rpm for 10 to 15 min (for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min); in step S2, after adding the flocculant, stir slowly at a rate of 20 rpm for 10 to 15 min (for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min).

[0050] The present invention will be described in detail below in conjunction with embodiments of the present invention, and each example is provided by way of explanation of the present invention without limiting the present invention. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present invention includes such modifications and variations within the scope of the appended claims and their equivalents.

[0051] In the embodiments of the present invention, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0052] Example 1

[0053] This embodiment provides a treatment process for lithium battery production wastewater. The experimental object is a stream of lithium battery production wastewater (pH value is about 7, nickel ion content is 100-400mg / L) from a new energy company in Hubei. The specific treatment steps are as follows: the reaction zone controls the pH value to 9 by controlling the amount of alkali solution and sodium hypochlorite, and stirs rapidly for 10 minutes; the coagulant ferric chloride dosage in the coagulation zone is 50mg / L, and stirs rapidly for 10 minutes; the flocculant PAM dosage in the flocculation zone is 3mg / L, and stirs slowly for 12 minutes; the amount of micro-sand added from the sand adding port for the first time is 200kg / ㎡ of the inclined tube area. A skimming pipe device is provided at the front end of the inclined tube sedimentation zone. The mud and sand in the inclined tube sedimentation zone are quickly separated, and the clean water flows upward, and enters the water outlet tank through the inclined tube separation through the water collecting tank, and the mud and sand sink downward. When the machine is started for the first time, the reflux pipeline is used first to control the deposition thickness of the mud and sand to be 10-15% of the height of the inclined tube sedimentation zone. When the mud level is higher than 15%, the mud and sand process is switched to the hydrocyclone pipeline without separate reflux; when the mud level drops below 10% again, the mud and sand process is switched to the reflux pipeline without entering the hydrocyclone for separation and discharge.

[0054] Comparative Example 1

[0055] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that the pH value of the reaction zone is controlled to be 8.

[0056] Comparative Example 2

[0057] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that the pH value of the reaction zone is controlled to be 10.

[0058] Comparative Example 3

[0059] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that sodium hypochlorite is not added to the reaction zone.

[0060] Comparative Example 4

[0061] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that no mud level meter is used and a manual switching process is adopted.

[0062] Manual switching is difficult to adjust in time: when the mud level is high, mud overturning is likely to occur, resulting in higher Ni and SS in the effluent; when the mud level is low, the discharged mud is too thin, resulting in high operating costs for reuse.

[0063] Comparative Example 5

[0064] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that no skimming pipe device is provided.

[0065] Comparative Example 6

[0066] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that the sedimentation thickness of the mud and sand is controlled to be 5-15% of the height of the inclined tube sedimentation zone.

[0067] The mud level is set too low: When the mud level is too low, the return sediment content is small, and most of it is clean water. The operating cost is high, the sludge reuse is difficult, and it cannot play the role of replenishing the floc volume in the flocculation zone. The flocculation effect is poor, resulting in higher SS and Ni in the effluent.

[0068] Comparative Example 7

[0069] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that the sedimentation thickness of the mud and sand is controlled to be 10-20% of the height of the inclined tube sedimentation zone.

[0070] The mud level is set too high: When the mud level in the inclined tube sedimentation area is too high, it is easy for the flocs to fail to settle in time, causing the pool to overturn, resulting in higher SS and Ni in the effluent.

[0071] Comparative Example 8

[0072] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the remaining step parameters are the same as those in Example 1. The only difference is that the initial input amount of micro-sand from the sand adding port is 150 kg / ㎡ of the inclined pipe area.

[0073] Comparative Example 9

[0074] This comparative example provides a treatment process for lithium battery production wastewater. The experimental object is the same as that in Example 1, and the parameters of the other steps are the same as those in Example 1. The only difference is that the amount of micro-sand input from the sand adding port for the first time is 250 kg / ㎡ of the inclined pipe area.

[0075] The relevant indicators of the effluent quality of Example 1 and Comparative Examples 1-9 are shown in Table 1:

[0076] Table 1

[0077]

[0078]

[0079] As can be seen from Table 1, compared with Example 1, in Comparative Example 1, due to the low pH value of the reaction zone, the Ni content in the effluent water quality is high; in Comparative Example 2, due to the high pH value of the reaction zone, more Mg is precipitated, which is not conducive to Ni reuse; in Comparative Example 3, due to the absence of sodium hypochlorite in the treatment agent in the reaction zone, the Ni content in the effluent water quality is high; in Comparative Example 4, due to the absence of a mud level meter and the use of only a manual switching process, the Ni and SS contents in the effluent water quality are high; in Comparative Example 5, due to the absence of a skimmer, the effluent water quality is high. The pipe device results in a high SS content in the effluent water quality and the scum is difficult to handle; in Comparative Example 6, the sediment deposition thickness is set too low, resulting in a high Ni content in the effluent water quality and high operating costs; in Comparative Example 7, the sediment deposition thickness is set too high, resulting in a high SS content in the effluent water quality and easy overturning of the pool; in Comparative Example 8, the initial input amount of micro-sand from the sand adding port is too low, resulting in a high SS content in the effluent water quality; in Comparative Example 9, the initial input amount of micro-sand from the sand adding port is too high, the sand concentration is too high, resulting in easy clogging of the cyclone.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium battery production wastewater treatment system, characterized in that: It includes a reaction zone, a coagulation zone, a flocculation zone and an inclined tube sedimentation zone which are sequentially connected along the flow direction of the wastewater; it also includes a mud and sand return pipe, a hydrocyclone for separating micro-sand and sludge, and a mud level meter; One end of the mud and sand return pipe is connected to the bottom of the inclined tube sedimentation zone, and the other end is respectively connected to the flocculation zone and the front end of the hydrocyclone; the bottom flow outlet at the lower end of the hydrocyclone is connected to the flocculation zone, and the upper end is connected to the sludge discharge pipe; the mud level meter is arranged in the inclined tube sedimentation zone to monitor the mud and sand deposition thickness in the inclined tube sedimentation zone.

2. The processing system according to claim 1, characterized in that A reflux valve is provided on the pipeline connecting the mud and sand return pipe with the flocculation zone, and a cyclone valve is provided on the pipeline connecting the mud and sand return pipe with the front end of the hydrocyclone; the mud level meter is connected to the DCS remote control system, and the DCS remote control system controls the stroke switching of the reflux valve and the cyclone valve.

3. The processing system according to claim 1 or 2, characterized in that: The reaction zone is provided with a treatment agent dosing pipeline for dosing the treatment agent; the treatment agent dosing pipeline is installed with a dosing flow meter; And / or, the reaction zone is provided with a pH online detector for monitoring the pH value of the reaction zone.

4. The processing system according to claim 1 or 2, characterized in that: The flocculation zone is provided with a sand adding port for initially adding micro sand; And / or, the coagulation zone is provided with a coagulant addition pipeline; and / or, the front end of the inclined tube sedimentation zone is provided with a skimming pipe device for collecting floating oil and floating mud.

5. A process for treating wastewater from lithium battery production, characterized in that: The processing system according to any one of claims 1 to 4 is used, comprising the following steps: Step 1: Add a treatment agent to the reaction zone. After the wastewater reacts with the treatment agent, the complexed nickel ions are converted into free nickel ions. The wastewater is then sent to the coagulation zone, and a coagulant is added to perform a coagulation reaction to aggregate the suspended matter and pollutants in the water. Step 2: The wastewater after coagulation treatment is sent to the flocculation area, and flocculants are added for flocculation reaction, and micro sand is added at the same time to make the suspended matter form larger flocs; Step 3: The wastewater after flocculation treatment passes through the inclined tube sedimentation area. After the mud and sand are settled, the sedimentation thickness is controlled. When the mud level is low or higher than the set sedimentation thickness, the mud and sand return along the mud and sand return pipe. According to the mud level monitored by the mud level meter, the mud and sand are controlled to flow back to the hydrocyclone or flocculation area. The effluent meets the discharge standards.

6. The treatment process according to claim 5, characterized in that: In step S3, the sedimentation thickness of mud and sand is controlled to be 10-15% of the height of the inclined tube sedimentation zone; when the mud level is lower than 10% of the height of the inclined tube sedimentation zone, the return valve is opened and the cyclone valve is closed, and all the mud and sand are returned to the flocculation zone; when the mud level is higher than 15% of the height of the inclined tube sedimentation zone, the cyclone valve is opened and the return valve is closed, and the micro-sand in the mud and sand enters the flocculation zone through the low flow port at the lower end of the hydrocyclone, and the sludge in the mud and sand is discharged from the sludge external discharge pipe.

7. The treatment process according to claim 5, characterized in that: In step S1, the treatment agent is a mixture of alkali solution and sodium hypochlorite; the dosage ratio of alkali solution to sodium hypochlorite is 1:2; and / or, the pH value of the reaction zone is controlled at 8.5 to 9.5; And / or, after adding the treating agent into the reaction zone, rapidly stir at a rate of 30 rpm for 10 to 15 minutes.

8. The treatment process according to claim 5, characterized in that: In step S1, the dosage of the coagulant is 50-55 mg / L; and / or, the coagulant is ferric chloride; and / or, after the coagulant is added, rapid stirring is performed at a rate of 30 rpm for 10-15 min.

9. The treatment process according to claim 5, characterized in that: In step S2, the dosage of the flocculant is 3-3.5 mg / L; and / or, the flocculant is a PAM flocculant; and / or, after adding the flocculant, the mixture is slowly stirred at a speed of 20 rpm for 10-15 min.

10. The treatment process according to any one of claims 5 to 9, characterized in that: The initial input amount of fine sand from the sand adding port is 200-220kg / ㎡ of inclined pipe area.

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