MVR (Mechanical Vapor Recompression) evaporative crystallization system for lithium battery recovery raffinate

Abstract

The utility model discloses a lithium battery recovery raffinate MVR (mechanical vapor recompression) evaporative crystallization system, which comprises an evaporation unit and a COD (chemical oxygen demand) removal unit, the evaporation unit is communicated with raffinate to be treated, the COD removal unit comprises an electrolytic bath, the liquid inlet end of the electrolytic bath is connected with the discharge end of the evaporation unit so as to remove COD in the concentrated raffinate, and the liquid outlet end of the electrolytic bath is connected with the discharge end of the evaporation unit. The liquid outlet end of the electrolytic cell is connected with the feeding end of the evaporation unit, so that the raffinate without COD flows back to the evaporation unit to be evaporated and crystallized. Compared with the existing Fenton method, the mode of removing COD (Chemical Oxygen Demand) in the raffinate has the advantages of lower cost and environmental protection; compared with the existing electro-catalysis technology or ozone oxidation COD removal, the method has the advantages of low energy consumption and small equipment investment.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium battery recycling, in particular to a lithium battery recycling raffinate MVR evaporation crystallization system. Background Art

[0002] With the extensive use of lithium batteries, the recycling of waste lithium batteries can not only reduce environmental pollution, but also recover valuable metals from waste batteries, thereby effectively alleviating resource shortages. The recycling of existing waste ternary lithium batteries generally involves disassembly, discharge, acid leaching and other steps to obtain the positive electrode material leachate, and then the extraction method is used to recover various valuable metals from the leachate. The raffinate produced by the extraction is fully reused because it contains a large amount of inorganic salts.

[0003] At present, in order to make full use of the inorganic salts in the raffinate, the evaporation process is generally used to treat the raffinate, and the inorganic salts produced can be sold as products. However, due to the introduction of water-soluble substances in the battery, the raffinate often presents high COD water quality. If the COD substances in the raffinate are not completely removed, it will lead to its concentration and enrichment in the MVR evaporation crystallization system. Excessive enrichment of organic matter will lead to a large amount of evaporation and crystallization bubbles, affecting the crystallization of the MVR evaporation and crystallization system. It will also increase the boiling point of the material, resulting in a decrease in the evaporation amount, which will cause the evaporation and crystallization system to surge and fail to produce normally. Therefore, the Fenton method is often used to remove COD from the raffinate in the pretreatment of the existing evaporation system, such as the Chinese patent application "A MVR Concentration Process for Recovering and Extracting Lithium Battery Extraction" published with publication number CN116693089A. However, the Fenton method requires the use of hydrogen peroxide and ferric sulfate to remove COD, which is costly and will produce a large amount of iron-containing waste residue, and the removal effect is poor. Utility Model Content

[0004] In summary, the purpose of the utility model is to provide a lithium battery recovery raffinate MVR evaporation crystallization system to solve the technical problems in the prior art of using the Fenton method to remove COD substances in the lithium battery recovery raffinate, such as high cost, large amount of iron-containing waste slag and poor treatment effect.

[0005] In order to achieve the above technical purpose, the utility model adopts the following technical solutions:

[0006] The utility model provides a lithium battery raffinate recovery MVR evaporation crystallization system, comprising:

[0007] an evaporation unit, the evaporation unit being connected to the raffinate to be treated;

[0008] The COD removal unit comprises an electrolytic cell, the liquid inlet end of the electrolytic cell is connected to the material outlet end of the evaporation unit to remove COD in the concentrated raffinate, and the liquid outlet end of the electrolytic cell is connected to the material feed end of the evaporation unit to return the raffinate after COD removal to the evaporation unit for evaporation and crystallization.

[0009] In some embodiments, the COD removal unit further includes a mother liquid tank, and the mother liquid tank is disposed on a passage connecting a liquid inlet end of the electrolytic cell and a material outlet end of the evaporation unit.

[0010] In some embodiments, the concentration of the raffinate stored in the mother liquid tank is maintained at 400-450 g / L.

[0011] In some embodiments, the reaction temperature in the mother liquid tank and the electrolytic cell is maintained at 40-60°C.

[0012] In some embodiments, the evaporation unit comprises a raffinate storage tank, a heat exchanger, a heater and a separation chamber which are sequentially connected according to the evaporation process flow, the discharge end of the separation chamber is sequentially connected to the mother liquid tank and the electrolytic cell, the liquid discharge end of the electrolytic cell is connected to the feed end of the heater,

[0013] Wherein, the liquid inlet end of the mother liquid tank is also connected to the water outlet end of the heat exchanger, and the discharge end of the heater is also connected to the water inlet end of the heat exchanger.

[0014] In some embodiments, the evaporation unit further includes a thickener and a centrifuge, the inlet and outlet of the thickener are respectively connected to the discharge end of the separation chamber and the feed end of the centrifuge, and the discharge end of the centrifuge is connected to the liquid inlet end of the mother liquid tank.

[0015] In some embodiments, the evaporation unit further comprises a dryer connected to the centrifuge.

[0016] In some embodiments, the evaporation unit further comprises a circulation pump, wherein an inlet and an outlet of the circulation pump are respectively connected to a discharge end of the separation chamber and a feed end of the heater.

[0017] In some embodiments, the evaporation unit further includes a compressor, and two ends of the compressor are respectively connected to the separation chamber and the heater.

[0018] In some embodiments, the evaporation unit further includes a condensed water tank, which is connected to the heat exchanger and is used to store condensed water discharged from the heat exchanger.

[0019] Compared with the prior art, the beneficial effects of the utility model mainly include:

[0020] The utility model provides a lithium battery raffinate recovery MVR evaporation crystallization system, which has a COD removal unit, and the COD removal unit specifically includes an electrolytic cell. When working, hydroxyl radicals are formed on the anode electrode material, and the COD substance in the ternary lithium battery black powder leaching raffinate can be removed to the maximum extent, and the removal effect is good; and compared with the existing Fenton method, the treatment process of the utility model does not need to use hydrogen peroxide and ferric sulfate, the cost is low, and a large amount of iron-containing waste residue will not be generated, thereby avoiding pollution to the environment; compared with electrocatalytic technology or ozone oxidation to remove COD, the utility model has lower energy consumption and small equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural block diagram of the lithium battery raffinate recovery MVR evaporation crystallization system described in the utility model.

[0022] Description of reference numerals:

[0023] 100, evaporation unit, 110, raffinate storage tank, 120, heat exchanger, 130, heater, 140, separation chamber, 150, thickener, 160, centrifuge, 170, dryer, 180, circulation pump, 190, compressor;

[0024] 200. COD removal unit, 210. electrolytic cell, 220. mother liquor tank. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0026] In the process of recycling raffinate, the Fenton method or electrocatalysis and ozone oxidation technology are usually used to remove COD substances in the raffinate, which has the problems of high cost, serious environmental pollution caused by the iron-containing waste slag, poor COD removal effect and high energy consumption. The purpose of the utility model is to propose a lithium battery raffinate recovery MVR evaporation crystallization system to solve the above technical problems.

[0027] Figure 1 The structural diagram of the MVR evaporation and crystallization system for recovering raffinate from lithium battery of the utility model is given. Figure 1 As shown, the lithium battery raffinate recovery MVR evaporation crystallization system includes an evaporation unit 100 and a COD removal unit 200. The COD removal unit 200 is used to effectively remove COD substances in the raffinate so that the concentration process of the raffinate can proceed smoothly.

[0028] The COD removal unit 200 specifically includes an electrolytic cell 210, the liquid inlet end of the electrolytic cell 210 is connected to the discharge end of the evaporation unit 100 to remove COD from the concentrated raffinate, and the liquid outlet end of the electrolytic cell is connected to the feed end of the evaporation unit 100 to reflux the raffinate after COD removal to the evaporation unit 100 for evaporation and crystallization to obtain inorganic salts.

[0029] In the utility model, the raffinate is the raffinate produced by leaching and extracting the black powder of the ternary lithium battery, and its main components are sodium sulfate and a small amount of lithium sulfate. Through the electrolytic cell 210 set up, hydroxyl radicals will be formed on the anode electrode material during operation, and it has a strong oxidizing ability, and can remove the COD substances in the leaching raffinate of the black powder of the ternary lithium battery to the maximum extent, and the removal effect is good; and compared with the existing Fenton method, the treatment process of the utility model does not need to use hydrogen peroxide and ferric sulfate, the cost is low, and a large amount of iron-containing waste slag will not be generated, thereby avoiding pollution to the environment; compared with electrocatalytic technology or ozone oxidation to remove COD, the energy consumption of the utility model is low and the equipment investment is small.

[0030] It is understandable that the COD removal unit 200 described in the present invention includes but is not limited to the electrolytic cell 210. In practical applications, other forms of electrocatalytic devices may also be selected.

[0031] In one embodiment, the COD removal unit 200 further includes a mother liquid tank 220, and the mother liquid tank 220 is disposed on a passage connecting the liquid inlet end of the electrolytic cell 210 and the material outlet end of the evaporation unit 100. That is, the material coming out of the evaporation unit 100 first passes through the mother liquid tank 220 and then enters the electrolytic cell 210, and the raffinate after the COD is removed by the electrolytic cell 210 re-enters the evaporation unit 100 for concentration and recovery. At this time, the COD substance has been removed from the raffinate, so when the raffinate is concentrated in the MVR evaporation and crystallization system, COD will not be enriched, and the boiling point of the material will not be increased, which can ensure the normal operation of the MVR evaporation and crystallization system.

[0032] In one embodiment, the mother liquid tank 220 is made of 316L material, the electrolytic cell 210 is made of PPH, the anode is made of titanium mesh coated with lead dioxide, and the cathode is made of titanium mesh.

[0033] In one embodiment, the evaporation unit includes a raffinate storage tank 110, a heat exchanger 120, a heater 130 and a separation chamber 140 which are connected in sequence according to the evaporation process flow, the discharge end of the separation chamber 140 is connected to the mother liquid tank 220 and the electrolytic cell 210 in sequence, and the liquid discharge end of the electrolytic cell 210 is connected to the feed end of the heater 130.

[0034] In one embodiment, the evaporation unit 100 further includes a thickener 150 and a centrifuge 160, wherein the inlet and outlet of the thickener 150 are respectively connected to the discharge end of the separation chamber 140 and the feed end of the centrifuge 160, and the discharge end of the centrifuge 160 is connected to the liquid inlet end of the mother liquid tank 220.

[0035] In one embodiment, the evaporation unit 100 further includes a dryer 170 , and the dryer 170 is connected to the centrifuge 160 .

[0036] In one embodiment, the evaporation unit 100 further includes a circulation pump 180 , and an inlet and an outlet of the circulation pump 180 are respectively connected to a discharge end of the separation chamber 140 and a feed end of the heater 130 .

[0037] In one embodiment, the evaporation unit 100 further includes a compressor 190 , and two ends of the compressor 190 are respectively connected to the separation chamber 140 and the heater 130 .

[0038] In one embodiment, the evaporation unit 100 further includes a condensed water tank, which is connected to the heat exchanger 120 and is used to store condensed water discharged from the heat exchanger 120 .

[0039] In one embodiment, in order to optimize the COD removal effect, we need to maintain the concentration of the raffinate stored in the mother liquor tank 220 at 400-450 g / L, and maintain the reaction temperature in the mother liquor tank 220 and the electrolytic cell 210 at 40-60°C.

[0040] Therefore, in order to achieve the above-mentioned effect, the liquid inlet end of the mother liquid tank 220 is also connected to the water outlet end of the heat exchanger 120, that is, the raffinate in the raffinate storage tank 110 is heated by the heat exchanger 120 and then introduced into the mother liquid tank 220. On the one hand, it is diluted with the supersaturated sodium sulfate solution in the mother liquid tank 220 to obtain the raffinate meeting the above-mentioned concentration, and on the other hand, the reaction temperature in the electrolytic cell 210 and the mother liquid tank 220 can reach the above-mentioned temperature range. In this way, the sodium sulfate content in the solution is more than 1 times higher than the electrolyte content in the raffinate, and can reach up to 450g / L, and the content is stable and has a certain temperature, which can reach up to 60°C. The high sodium sulfate content is beneficial to reducing the energy consumption of electrocatalysis and improving the current utilization rate. The stable content facilitates the production control of electrocatalysis. Because the solution is a mixed solution after the raffinate is evaporated and preheated, it has a certain temperature, which can increase the conductivity of the solution and change the oxidation potential, which is beneficial to remove COD in the solution. The above can greatly improve the COD removal efficiency of the COD removal unit 200 and reduce the energy consumption of operation.

[0041] In a preferred embodiment, in order to save energy, the discharge end of the heater 130 is also connected to the water inlet end of the heat exchanger 120 to provide a heat source for heating the heat exchanger 120 .

[0042] In summary, the working process of a lithium battery raffinate recovery MVR evaporation crystallization system provided by the utility model is as follows:

[0043] 1. The raffinate generated by the extraction line is stored in the raffinate storage tank 110. The raffinate is heated and concentrated by the evaporation unit 100 composed of the heat exchanger 120, the heater 130, the separation chamber 140, the circulating pump 180, etc. The compressor 190 performs work and pressurizes the steam generated by the evaporation of the raffinate to form secondary steam, which is then sent to the heater 130 to heat the material. The heat source used by the heat exchanger 120 is the condensed water generated by the heater 130;

[0044] 2. When the raffinate is concentrated to a discharge density of 1.4-1.5 g / ml, it enters the thickener 150 to grow the sodium sulfate crystals and thicken the material, and then enters the centrifuge 160 to separate the sodium sulfate salt, and the liquid portion enters the mother liquid tank 220;

[0045] 3. The concentrated raffinate is stored in the mother liquid tank 220, and the raffinate (not concentrated) produced by the heat exchanger 120 is added to the mother liquid tank 220, and the solution concentration is controlled to be 400-450 g / L, and then the solution enters the electrolytic cell 210 for oxidation reaction, and the reaction temperatures of the mother liquid tank 220 and the battery cell 210 are controlled to be 40-60° C.;

[0046] 4. The qualified material after oxidation in the electrolytic cell 210 is returned to the heater 130 for heating, and finally the COD in the raffinate is removed, so that the MVR evaporation crystallization system can operate normally.

[0047] The specific implementation methods of the utility model described above do not constitute a limitation on the protection scope of the utility model. Any other corresponding changes and modifications made according to the technical concept of the utility model should be included in the protection scope of the claims of the utility model.

Claims

1. A lithium battery raffinate recovery MVR evaporation crystallization system, characterized in that: include: an evaporation unit, the evaporation unit being connected to the raffinate to be treated; The COD removal unit comprises an electrolytic cell, the liquid inlet end of the electrolytic cell is connected to the material outlet end of the evaporation unit to remove COD in the concentrated raffinate, and the liquid outlet end of the electrolytic cell is connected to the material feed end of the evaporation unit to return the raffinate after COD removal to the evaporation unit for evaporation and crystallization.

2. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 1, characterized in that: The COD removal unit further includes a mother liquid tank, which is arranged on a passage connecting the liquid inlet end of the electrolytic cell and the material outlet end of the evaporation unit.

3. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 2, characterized in that: The concentration of the raffinate stored in the mother liquid tank is maintained at 400-450 g / L.

4. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 3, characterized in that: The reaction temperature in the mother liquid tank and the electrolytic cell is maintained at 40-60°C.

5. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 2, characterized in that: The evaporation unit comprises a raffinate storage tank, a heat exchanger, a heater and a separation chamber which are sequentially connected according to the evaporation process flow. The discharge end of the separation chamber is sequentially connected to the mother liquid tank and the electrolytic cell. The discharge end of the electrolytic cell is connected to the feed end of the heater. Wherein, the liquid inlet end of the mother liquid tank is also connected to the water outlet end of the heat exchanger, and the discharge end of the heater is also connected to the water inlet end of the heat exchanger.

6. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 5, characterized in that: The evaporation unit further comprises a thickener and a centrifuge, wherein the inlet and outlet of the thickener are respectively connected to the discharge end of the separation chamber and the feed end of the centrifuge, and the discharge end of the centrifuge is connected to the liquid inlet end of the mother liquid tank.

7. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 6, characterized in that: The evaporation unit further comprises a dryer connected to the centrifuge.

8. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 7, characterized in that: The evaporation unit further comprises a circulation pump, wherein an inlet and an outlet of the circulation pump are respectively connected to a discharge end of the separation chamber and a feed end of the heater.

9. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 8, characterized in that: The evaporation unit further includes a compressor, and two ends of the compressor are respectively connected to the separation chamber and the heater.

10. The lithium battery raffinate recovery MVR evaporation crystallization system according to claim 9, characterized in that: The evaporation unit further comprises a condensed water tank, which is connected to the heat exchanger and is used for storing condensed water discharged from the heat exchanger.

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