In the recycling process of waste ternary lithium batteries and lithium iron phosphate batteries, sulfuric acid and caustic soda are inevitably converted into sodium sulfate salts due to the technological requirements. The raw solution containing sodium sulfate mainly includes the return solution of lithium salt system, the solution after synthesis of ternary nickel-cobalt, the ternary pre-treatment discharge brine, the solution after precipitation of lithium iron phosphate, the discharge brine of lithium iron phosphate, the solution after precipitation of lithium lithium by lithium lithium salt, the residual solution of nickel-cobalt-manganese salt extraction, the solution after synthesis of nickel-cobalt-manganese, etc. These solutions are directly or purified into the MVR evaporation system, and the most crystallization and drying to produce anhydrous sodium sulfate products. The main production process is as follows:
1. Mix the liquid
Ternary nickel-cobalt synthesis liquid, ternary pre-treated discharge brine, lithium iron phosphate after settling lithium, lithium iron phosphate discharge brine, lithium salt after settling lithium nickel cobalt manganese salt extraction nickel residue, nickel cobalt manganese synthesis liquid and other mixed liquids.
2. Removing impurities and refining
After the preparation of sodium sulfate solution by liquid alkali + sodium sulfide depth to remove heavy metals (press filter out a small amount of nickel and cobalt slag, return to feed for reuse), adjust the PH to 5~7; After the analysis is qualified, the raw liquid tank is entered, and the raw liquid tank plays the role of storing and regulating the raw liquid to meet the continuous and stable operation of MVR wastewater evaporator. The raw liquid tank is equipped with a raw liquid pump. The raw liquid pump evenly transports the sodium sulfate aqueous solution to the evaporation treatment system. The control valve after the raw liquid pump is adjusted to maintain the balance between the lifting amount of the raw liquid and the evaporation amount.
3. Return solution
The sodium sulfate decahydrate crystals produced by the lithium salt system are added to the condensed water and the submerged lithium wash water to form a nearly saturated sodium sulfate solution, which is stored in a separate stock liquid tank and then directly transported to the MVR evaporation and concentration system.
4. MVR evaporation and crystallization of sodium sulfate solution
The aqueous solution containing sodium sulfate is preheated by the condensate preheater and then enters the evaporation chamber of the MVR evaporation crystallization system. The MVR evaporation system is equipped with a vertical heat exchanger after the forced circulation pump. Under the action of the forced circulation pump, the material liquid flows in such a circulation along the evaporation chamber – heat exchanger – forced circulation pump – heat exchanger – evaporation chamber, the material liquid is heated in the heat exchanger, and the gas-liquid-solid separation is realized in the evaporation chamber. The concentrated salt slurry is sent to the salt outlet by the discharge pump for concentration and separation, and then discharged into the salt sink for collection and concentration and separation, and finally discharged into the centrifuge for centrifugal separation. The centrifugal filtrate and the salt separator supernatant are collected into the filtrate tank and sent back to the MVR evaporator for evaporation and crystallization. The sodium sulfate separated from the centrifuge enters the drying system.
5. Drying – Packaging
The sodium sulfate obtained from crystallization contains a small amount of water, and depending on the reuse situation, it is determined whether to use drying equipment to reduce water. The drying equipment can be fluidized bed drying (control drying temperature ~ 150℃), open the vibrating fluidized bed and the supporting dust collection device, and then transported to the vibrating fluidized bed drying with the screw feeder to obtain anhydrous sodium sulfate products (water content <0.5%), packaging for export.
Post time: Aug-28-2024
