CN115353238A - Treatment method of battery-grade lithium nitrate production wastewater - Google Patents

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to a treatment method of battery-grade lithium nitrate production wastewater. The treatment method comprises the step of sequentially enabling battery-grade lithium nitrate production wastewater to enter a heat exchange unit, an ultrafiltration unit, a primary softener, a primary reverse osmosis unit, a primary softener, a secondary reverse osmosis unit and an electrodialysis unit for separation treatment. According to the invention, salt substances and organic matters are removed or concentrated from the solution by utilizing the efficient saline-water separation function of the reverse osmosis membrane and the selective permeability of the electrodialysis ion exchange membrane, so as to generate a high-concentration lithium nitrate solution; effectively solves the problem of water resource and lithium nitrate raw material waste when the conventional technology is used for treating the battery-grade lithium nitrate production wastewater.

Description

A kind of treatment method of battery grade lithium nitrate production wastewater

technical field

The invention belongs to the technical field of waste water treatment, and in particular relates to a treatment method for battery-grade lithium nitrate production waste water.

Background technique

Lithium nitrate (LiNO ₃ ) is an indispensable electrode material in the production of lithium-ion batteries. Whether it is a lithium iron phosphate battery or a ternary lithium battery, the use of lithium nitrate is inseparable. With the rise of the new energy industry, especially new energy vehicles, the demand for lithium-ion batteries has increased significantly, which has led to an increase in the demand for lithium nitrate year by year. The treatment of lithium nitrate production wastewater and the recovery of high-value materials in wastewater have become a new topic.

The production process of lithium nitrate generally uses lithium carbonate or lithium hydroxide to react with nitric acid, and the lithium nitrate produced by the reaction is evaporated and dried. Therefore, condensed water generated by evaporation and drying will be produced in this process, and the water contains system. Lithium nitrate and other raw materials.

Due to the low concentration of lithium nitrate in lithium nitrate wastewater, in the usual treatment process, lithium nitrate wastewater is usually discharged after physical and chemical coagulation and sedimentation or merged into other wastewater such as domestic sewage in the factory area for treatment and discharge after reaching the standard. Cause the waste of water resource and lithium nitrate raw material.

Contents of the invention

The present invention aims to solve the above problems, and provides a treatment method for battery-grade lithium nitrate production wastewater, which can realize the comprehensive recovery and utilization of water resources and lithium resources.

According to the technical scheme of the present invention, the treatment method of said battery-grade lithium nitrate production wastewater comprises the following steps,

S1: The battery-grade lithium nitrate production wastewater enters the heat exchange unit for cooling;

S2: The battery-grade lithium nitrate production wastewater after cooling enters the ultrafiltration unit for filtration, the concentrated water obtained from the filtration is directly discharged, and the product water obtained from the filtration enters the primary softener to remove calcium and magnesium ions;

S3: The water produced by the first-stage softener enters the first-stage reverse osmosis unit for concentration and separation. The product water obtained by the concentration and separation of the first-stage reverse osmosis unit is discharged as circulating cooling water, and the concentrated water obtained by the concentration and separation of the first-stage reverse osmosis unit enters the second-stage softener. Remove calcium and magnesium ions;

S4: The water produced by the secondary softener enters the secondary reverse osmosis unit for concentration and separation, and the product water obtained from the concentration and separation of the secondary reverse osmosis unit is discharged as circulating cooling water;

S5: The concentrated water obtained from the concentration and separation of the secondary reverse osmosis unit enters the electrodialysis unit for brine separation, and the product water obtained from the brine separation is returned to the primary reverse osmosis unit for further treatment or directly discharged, and the concentrated water obtained from the brine separation is used as a production raw material to extract lithium for reuse , Complete the treatment of battery-grade lithium nitrate production wastewater.

The invention comprehensively recycles water resources and lithium resources through the joint use of membrane system and electrodialysis system.

Further, in the step S1, the battery-grade lithium nitrate production wastewater is stored in a regulating tank before entering the heat exchange unit, and the regulating pond is used for buffer storage of the battery-grade lithium nitrate production wastewater.

Further, in the step S1, the temperature is lowered to 30-40° C., preferably 35° C., to protect the membrane material in subsequent processing.

Further, the average pore size of the ultrafiltration membrane in the ultrafiltration unit is 30-70 nm.

Further, in the step S2, external pressure filtration is adopted.

Further, in the step S2, the water production rate of the ultrafiltration unit is 90-95%, preferably 93%, the feed water flow rate is 28-32m ³ /h, and the water production flow rate is 26-29m ³ /h (into primary softener), the flow rate of concentrated water is 1.5-2.5m ³ /h; in one embodiment, the flow rate of incoming water is 29m ³ /h, and the flow rate of product water is 27m ³ /h (entering the primary softener), Concentrated water flow rate is 2m ³ /h discharge

Further, in the step S3, the average operating pressure of concentration and separation in the primary reverse osmosis unit is 0.7-1.0 mpa.

Further, in the step S3, the recovery ^rate of the concentrated and separated product water in the primary reverse osmosis unit is 70-80%, preferably 75%; -7.5m ³ /h.

Further, in the step S4, the average operating pressure of concentration and separation in the secondary reverse osmosis unit is 1.2-2.0 mpa.

Further, in the step S5, the recovery rate of the concentrated and separated product water in the secondary reverse osmosis unit is 55-65%, preferably 75%; the influent flow rate is 6.5-7.5m ³ /h, and the concentrated water flow rate is 2.5-3.0m ³ /h;.

Specifically, the treatment system adopted in the above treatment method includes a heat exchange unit, an ultrafiltration unit, a primary softener, a primary reverse osmosis unit, a primary softener, a secondary reverse osmosis unit, and an electrodialysis unit connected in sequence, wherein The water outlet of the first-stage reverse osmosis unit and the second-stage reverse osmosis unit are connected to the oxidation tank, the water outlet of the electrodialysis unit is connected to the first-stage reverse osmosis unit and/or the drainage pond, and the concentrated water outlet of the electrodialysis unit is provided with a reuse pool .

Further, the heat exchange unit is a plate heat exchanger, and its heat exchange material can be SUS304 (304 stainless steel), and the water inlet end of the heat exchange unit is provided with a regulating pool; the ultrafiltration unit includes an ultrafiltration water inlet tank, an ultrafiltration water inlet pump , ultrafiltration backwash pump, ultrafiltration membrane group, ultrafiltration pipeline, instrument, etc.; primary softener, secondary softener including softening water inlet tank, softener tank, resin, regeneration system, softener pipeline, Softener meter.

Compared with the prior art, the technical solution of the present invention has the following advantages:

(1) The present invention utilizes the high-efficiency brine separation effect of the reverse osmosis membrane and the selective permeation performance of the electrodialysis ion-exchange membrane to realize the removal or enrichment and concentration of salts and organic matter from the solution to produce a high-concentration lithium nitrate solution;

(2) The present invention effectively solves the problem of waste of water resources and lithium nitrate raw materials that exist when the conventional technology is processing battery-grade lithium nitrate production wastewater, and realizes comprehensive recycling of water resources and lithium resources.

Description of drawings

FIG. 1 is a schematic structural view of the processing system in Example 1.

Figure 2 is a schematic flow chart of the processing method in Example 2.

Explanation of reference signs: 1-regulating tank, 2-heat exchange unit, 3-ultrafiltration unit, 4-first-stage softener, 5-first-stage reverse osmosis unit, 6-first-stage softener, 7-second-stage reverse osmosis unit, 8-electrodialysis unit, 9-oxidation tank, 10-drainage tank, 11-reuse water tank.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

Example 1

As shown in Figure 1, the treatment system for battery-grade lithium nitrate production wastewater includes a regulating tank 1, a heat exchange unit 2, an ultrafiltration unit 3, a primary softener 4, a primary reverse osmosis unit 5, and a primary softening tank connected in sequence. Device 6, secondary reverse osmosis unit 7 and electrodialysis unit 8. Wherein, the concentrated water outlet of the ultrafiltration unit 3 is connected to the drainage pool 10; the water production outlet of the first-stage reverse osmosis unit 5 and the second-stage reverse osmosis unit 7 is connected to the oxidation tank 9; the water production outlet of the electrodialysis unit 8 is connected to the first-stage reverse osmosis The unit 5 and/or the drainage tank 10, the concentrated water outlet of the electrodialysis unit is connected to the reuse water tank 11.

Example 2

As shown in Figure 2, the treatment method of battery-grade lithium nitrate production waste water adopts the treatment system in embodiment 1, comprises the following steps:

S1: Use a booster pump to pump the battery-grade lithium nitrate production wastewater (wastewater) stored in the regulating tank into the heat exchange unit (plate heat exchanger) to cool down under the action of cooling water, and the temperature of the wastewater is reduced from 50°C to 35°C ℃;

The total salt content of the wastewater in the regulating tank is 1000mg/L, and the flow rate of the wastewater entering the regulating tank is 29m ³ /h; the flow rate of the water entering the heat exchange unit is 29m ³ /h;

S2: The battery-grade lithium nitrate production wastewater after cooling enters the ultrafiltration unit for filtration to remove suspended solids; the concentrated water filtered by the ultrafiltration unit is directly discharged, and the filtered product water enters the primary softener to remove calcium and magnesium ions;

The ultrafiltration unit includes an ultrafiltration water inlet tank, an ultrafiltration water inlet pump, an ultrafiltration backwash pump, an ultrafiltration membrane group, pipelines, instruments, etc.; the designed water production rate of the ultrafiltration unit is 93%, and the influent flow rate is ^29m3 /h. The produced water enters the primary softener at a flow rate of 27m ³ /h, and the concentrated water is discharged at a flow rate of 2m ³ /h (into the drainage tank 10);

S3: The water produced by the primary softener enters the primary reverse osmosis unit for concentration (concentrating lithium nitrate) and separation. Concentrated water obtained from the concentration and separation of the osmosis unit enters the secondary softener to remove calcium and magnesium ions;

The designed water recovery rate of the primary reverse osmosis unit is 75%, the influent flow rate is 27m ³ /h, the product water flow rate is 20.25m ³ /h (discharged into the oxidation tank), and the concentrated water enters the secondary softener at a flow rate of 6.75m ³ /h , after a first-stage reverse osmosis system, the concentration of lithium nitrate is concentrated and increased to 4 times that of raw water (battery-grade lithium nitrate production wastewater);

S4: The water produced by the secondary softener enters the secondary reverse osmosis unit for concentration and separation, and the product water obtained from the concentration and separation of the secondary reverse osmosis unit is discharged as circulating cooling water;

The design water recovery rate of the two-stage reverse osmosis unit is 60%, the influent flow rate is 6.75m ³ /h, the product water flow rate is 4.05m ³ /h (discharged into the oxidation tank), and the concentrated water enters the electrodialysis unit at a flow rate of 2.7m ³ /h , through the secondary reverse osmosis unit, the concentration of lithium nitrate is concentrated and increased to 10 times that of raw water;

S5: Concentrated water obtained from the concentration and separation of the two-stage reverse osmosis unit enters the electrodialysis unit, and brine is separated by electrodialysis. Lithium reuse, complete the treatment of battery-grade lithium nitrate production wastewater.

The designed water flow rate of the electrodialysis unit is 2.75m ³ /h, the flow rate of concentrated water is 0.27m ³ /h, and the flow rate of product water is 2.43m ³ /h. After the electrodialysis unit, the concentration of lithium nitrate is concentrated and increased to 55 times that of the raw water, meeting the water quality requirements for the production of lithium nitrate.

Example 3

On the basis of Example 2, the obtained product water (electrodialysis and ultrafiltration product water) obtained by the direct discharge of brine separation in step S5 is returned to the primary reverse osmosis unit for further processing. Processing capacity, increase processing flow rate.

Apparently, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in various forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. However, the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. a treatment method for battery grade lithium nitrate production waste water, is characterized in that, comprises the following steps, S1: The battery-grade lithium nitrate production wastewater enters the heat exchange unit for cooling; S2: The battery-grade lithium nitrate production wastewater after cooling enters the ultrafiltration unit for filtration, the concentrated water obtained from the filtration is directly discharged, and the product water obtained from the filtration enters the primary softener to remove calcium and magnesium ions; S3: The water produced by the first-stage softener enters the first-stage reverse osmosis unit for concentration and separation. The product water obtained by the concentration and separation of the first-stage reverse osmosis unit is discharged as circulating cooling water, and the concentrated water obtained by the concentration and separation of the first-stage reverse osmosis unit enters the second-stage softener. Remove calcium and magnesium ions; S4: The water produced by the secondary softener enters the secondary reverse osmosis unit for concentration and separation, and the product water obtained from the concentration and separation of the secondary reverse osmosis unit is discharged as circulating cooling water; S5: The concentrated water obtained from the concentration and separation of the secondary reverse osmosis unit enters the electrodialysis unit for brine separation, and the product water obtained from the brine separation is returned to the primary reverse osmosis unit for further treatment or directly discharged, and the concentrated water obtained from the brine separation is used as a production raw material to extract lithium for reuse , Complete the treatment of battery-grade lithium nitrate production wastewater. 2. The method for processing battery-grade lithium nitrate production waste water as claimed in claim 1, characterized in that, in the step S1, the battery-grade lithium nitrate production waste water is stored in a regulating tank before entering the heat exchange unit. 3. The method for treating battery-grade lithium nitrate production wastewater as claimed in claim 1, characterized in that, in the step S1, the temperature is lowered to 30-40°C. 4. the processing method of battery grade lithium nitrate production waste water as claimed in claim 1, is characterized in that, the ultrafiltration membrane average aperture 30-70nm in the described ultrafiltration unit. 5. the treatment method of battery grade lithium nitrate production wastewater as claimed in claim 1, is characterized in that, in described step S2, adopts external pressure filter. 6. the treatment method of battery grade lithium nitrate production wastewater as claimed in claim 1, is characterized in that, in described step S2, the water production rate of ultrafiltration unit is 90-95%. 7. the treatment method of battery grade lithium nitrate production wastewater as claimed in claim 1, is characterized in that, in described step S3, the average operating pressure of concentration and separation in the primary reverse osmosis unit is 0.7-1.0mpa. 8. The method for treating battery-grade lithium nitrate production wastewater as claimed in claim 1 or 7, characterized in that, in the step S3, the recovery rate of the product water concentrated and separated in the primary reverse osmosis unit is 70-80%. 9. The method for processing battery-grade lithium nitrate production wastewater as claimed in claim 1, characterized in that, in said step S4, the average operating pressure of concentration and separation in the secondary reverse osmosis unit is 1.2-2.0mpa. 10. The method for treating battery-grade lithium nitrate production wastewater as claimed in claim 1 or 9, characterized in that, in the step S4, the recovery rate of the product water concentrated and separated in the secondary reverse osmosis unit is 55-65%.

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