Preprocessing Process Flow for Pyrolysis and Sorting of Charged Lithium Batteries

This charged pre‑treatment technology enhances safety and efficiency from the source by using charged batteries to induce oxygen‑depleted tearing; it thoroughly removes organic components through thermal volatilization and anaerobic pyrolysis, while utilizing residual battery heat and the self‑igniting heat generated by volatile pyrolysis gases to provide thermal energy, thereby achieving energy savings and ensuring stable downstream processes. Finally, by leveraging highly efficient flexible stripping and multi‑stage precision sorting, it enables the extraction of valuable resources with high purity recovery rates. The entire process forms a closed loop that is safe, environmentally friendly, energy‑efficient, highly productive, and boasts a high degree of resource utilization—making it an advanced, leading technological approach for the resource recovery and utilization of waste lithium‑ion batteries today.

Lithium Battery Exhaust Gas Treatment Process Using the Dual-Alkali Method

1. 1. Thermal Volatilization: The electrolyte LIPF6 in lithium batteries has poor thermal stability and tends to decompose when heated under oxygen‑poor conditions. 
   LiPF₆ (lithium hexafluorophosphate) → LiF↓ + PF₅↑ (Lithium fluoride LiF is a solid and remains almost entirely within the lithium electrode material; it does not volatilize into gas. Therefore, during the downstream exhaust gas treatment process, the wastewater will not contain lithium fluoride LiF.)
2. Pyrolysis: LiPF₆ (lithium hexafluorophosphate) → LiF↓ + PF₅ (Phosphorus pentafluoride is toxic and reacts with water to produce HF). 
   Hydrolysis: 
   LiPF₆ (lithium hexafluorophosphate) + H₂O → LiF (lithium fluoride) + 2HF + POF₃; 
   PF₅ (phosphorus pentafluoride) + H₂O → 2HF + POF₃ (phosphorus trifluoride oxide); 
   POF₃ (phosphorus trifluoride oxide) + H₂O → 2HF + PO₂F; 
   PO₂F (phosphorus difluoride) + 2H₂O → HF + H₃PO₄ (phosphoric acid) 
   Defluorination reaction: 
   (1) HF + NaOH → NaF (sodium fluoride) + 2H₂O 
   Ca(OH)₂ (calcium hydroxide) + 2NaF (sodium fluoride) → CaF₂ (calcium fluoride)↓ + 2NaOH 
   2HF + Ca(OH)₂ (calcium hydroxide) → CaF₂ (calcium fluoride)↓ + 2H₂O 
   (2) H₃PO₄   +3NaOH→ Na₃PO₄ (sodium phosphate) +3H₂O 
   2Na₃PO + 3Ca(OH) ₂ →Calcium ₃ (Phosphate) ₂ (Calcium phosphate)↓ + 6NaOH 
   2LiPF₆ (lithium hexafluorophosphate) + 8Ca(OH)₂ (calcium hydroxide) → Ca₃(PO₄)₂↓ + 5CaF₂↓ + 8H₂O + 2LiF↓ 
   The alkaline solution uses sodium hydroxide and calcium hydroxide, with sodium hydroxide serving solely as a catalytic intermediate that is recycled, while calcium hydroxide reacts chemically with phosphorus and fluorine to form salts, which are then removed via precipitation and filtration. There is no need to invest in a costly RTO regenerative thermal oxidation system for exhaust gas treatment.
3. No Dioxin: The four key conditions for dioxin formation are the presence of chlorine, oxygen, metal compound catalysts, and an optimal temperature range of approximately 260–860°C. Under anaerobic conditions, feedstock undergoes pyrolysis to produce small molecules, and the feedstock itself is virtually free of chlorine. These small gas molecules are fully combusted, releasing heat in the process. Since the combustion gases contain neither chlorine nor metal catalysts, the conditions necessary for dioxin formation are simply absent.
4. Because the exhaust gas combustion temperature is below 800°C, virtually no nitrogen oxides are produced; since the combustion involves only small, combustible molecules, no furan‑type gases are generated in the exhaust.
5. Two alkaline spray stages are used (the alkaline solutions consist of sodium hydroxide and calcium hydroxide; sodium hydroxide is recycled solely as a catalytic intermediate, while calcium hydroxide is used to ultimately react phosphorus and fluorine into salts, which are then removed via precipitation and filtration).
6. Phosphorus pentafluoride PF5 is adsorbed and converted into calcium salt precipitates through spray scrubbing with calcium hydroxide Ca(OH)2 solution. The reaction is as follows: 2PF5 + 8Ca(OH)2 → Ca3(PO4)2↓ (calcium phosphate) + 5CaF2↓ (calcium fluoride) + 8H2O. Therefore, direct spray application of calcium hydroxide Ca(OH)2 solution should be avoided as much as possible, since this can easily lead to scaling within the spray tower, resulting in equipment blockage.
7. After alkali spraying, the gas is further washed with clean water spray. The primary function of clean water spray washing is to remove calcium phosphate Ca₃(PO₄)₂, calcium fluoride CaF₂, and alkaline substances from the gas, thereby preventing air pollution caused by calcium phosphate Ca₃(PO₄)₂, calcium fluoride CaF₂, and alkaline gases present in the exhaust stream. Once cleaning is complete, moisture is removed from the gas through mist separation (the main purpose of mist separation is once again to eliminate the water, calcium phosphate Ca₃(PO₄)₂, and calcium fluoride CaF₂ contained in the mist). The gas is then ignited, allowing the flue gas to be discharged at high altitudes in compliance with emission standards.  
8. The flue gas combustion temperature is approximately 700°C. Since it does not exceed 1,000°C, no nitrogen oxides are produced (if nitrogen oxide removal is required, urea can be injected). The combustible substances are all carbonate esters with relatively small molecular weights and do not contain high‑molecular‑weight plastics. Because carbonate esters burn completely and efficiently, no furan‑type gases are generated in the flue gas either.
9. Rather than relying on RTO combustion exhaust gas treatment equipment, various types of waste gases are utilized to supply heat to the oxygen‑free furnace system through a combined combustion and crushing process. The carbonate components found in electrolytes, along with hydrogen fluoride and phosphorus fluoride generated by the volatilization of lithium hexafluorophosphate, undergo mutual combustion with the combustible gases produced during the pyrolysis of organic materials in the downstream processes. Within the combustion chamber, the waste gases generated during crushing, sorting, and pyrolysis serve as supplemental oxygen, thereby completing the combustion process. The residual heat from combustion is then used to heat the oxygen‑free furnace, enabling the cyclical utilization of organic energy throughout the lithium battery sorting process. After being thermally utilized through combustion, the exhaust gases undergo rapid quenching, multiple stages of alkaline liquid spraying, mist separation, and catalytic adsorption to further absorb trace harmful gases present in the exhaust stream. The treated gases are then discharged via an induced draft fan and chimney, meeting all relevant emission standards.

Main Advantages of Pre‑Treatment for Recycled Lithium Batteries with Electricity

1. Live‑charge crushing pretreatment reduces equipment investment and costs associated with discharging, and the residual electrical energy generated during the crushing of live batteries can be harnessed for secondary utilization through heat generation.
2. After seven generations of upgrades and improvements, the electrically assisted crushing process has significantly reduced nitrogen consumption, with each ton of material requiring approximately 80 cubic meters of nitrogen when the nitrogen purity is 98.5%.
3. The live‑charge shredding process utilizes a closed, modular, series‑connected tearing system that can complete the tearing of battery modules—ranging in length from 18 mm to 500 mm—directly from cylindrical cells in a single pass. The maximum output for live‑charge battery shredding can reach 5 tons.
4. The lithium battery materials undergo low‑temperature volatilization, medium‑temperature volatilization, high‑temperature pyrolysis, residual heat pyrolysis, and a cooling system. The material travels through a section approximately 50 meters long, ensuring thorough volatilization, pyrolysis, and cooling.
5. The electrolyte and organic materials are fully utilized, while the combustion of volatile and pyrolysis exhaust gases provides heat for pyrolysis, medium‑temperature volatilization, low‑temperature volatilization, and preheated oxygen‑enriched air supply, resulting in a total waste gas combustion heat utilization rate of nearly 80%.
6. Pre‑treatment of charged lithium batteries to a capacity of over 1 ton requires virtually no external heat source; the residual electricity in the batteries and the pyrolysis gas from the organic compounds they contain provide sufficient heat for self‑sufficiency.
7. The pyrolysis material paddle cooling system is equipped with a powder removal function, achieving a powder removal rate of 70% during cooling while simultaneously reducing the material temperature to below a safe threshold of 50°C.
8. Using magnetic separation, color sorting, and eddy current separation, copper blocks, aluminum blocks, stainless steel, and ferrous materials are thoroughly separated.
9. The flexible kneading and powder removal process minimizes fine powder generated from the positive and negative electrodes’ copper and aluminum, thereby enhancing electrode powder purity and increasing copper and aluminum recovery rates. At the same time, the workshop maintains low noise levels, with operational noise below 80 decibels under normal conditions.
10. Screening is performed using an air-flow centrifugal grading sieve, achieving mechanical forces without vibration. This enhances purity, efficiency, and stability.
11. All dust outlets are equipped with negative-pressure collection systems to prevent dust generation.
12. The exhaust gas does not need to be treated by combustion in an RTO system, significantly reducing exhaust gas treatment costs.
13. Pre‑treatment for the recovery of lithium batteries with electricity, consuming less than 100 cubic meters of nitrogen per ton, with zero cubic meters of natural gas; compared to other manufacturers, nitrogen and natural gas consumption has decreased by more than fivefold year-on-year.
14. This production process can handle an annual throughput of up to 30,000 tons per production line, with processing costs below 350 yuan per ton.
15. This technology employs a closed-loop process featuring charged, oxygen‑poor crushing, electrolyte volatilization, oxygen‑free pyrolysis, flexible powder removal, and precise sorting, thoroughly addressing the pain points of traditional recycling—such as “slow discharge, severe pollution, and significant metal loss”—and achieving safe crushing → organic removal → efficient powder removal → precise sorting → high‑purity recovery.

Indicator Parameters and Cost Accounting (The following are non-saltwater discharge recovery indicators; the actual results shall be subject to acceptance testing.)

Treatment of Waste Lithium‑Ion Battery Exhaust Gases and Discharge of the Three Wastes

Results of Organized Waste Gas Testing

Complies with the national standards “Technical Guidelines for Pollution Control in the Treatment of Waste Lithium-Ion Power Batteries” (HJ1186-2021) and GB18484-2020. The following are the emission monitoring indicators after waste lithium‑ion battery exhaust gas treatment:

Photos of the pre‑processing stage for the live‑battery recycling of waste lithium batteries.