NMC Battery Recycling（1）

NMC battery black mass wet treatment process

The facility consists of a lithium extraction workshop, a NMC battery leaching and extraction workshop, a lithium deposition workshop, and an evaporation and crystallization unit. The black mass from crushed NMC battery cells and purchased NMC battery black mass are temporarily stored in a black mass warehouse. Selective lithium extraction then occurs in the lithium extraction workshop, producing a lithium-rich solution, a nickel-cobalt-manganese mixture, and nickel-cobalt hydroxide. The lithium-rich solution is piped directly to the lithium deposition workshop to produce lithium carbonate. The nickel-cobalt-manganese mixture and nickel-cobalt hydroxide are then transported directly to the NCM battery leaching and extraction workshop, where leaching and extraction processes produce nickel sulfate solution, cobalt sulfate solution, and manganese sulfate solution.

Below are the first part of the process of NMC battery recycling

Lithium extraction process

All types of tanks in the lithium extraction workshop are covered, and the liquid materials are transferred by pipeline pumping. The tank cover is equipped with an exhaust hole that is directly and tightly connected to the collection pipeline.

1. Unpacking

Ton bags of NMC battery black mass are transported by forklift from the black mass warehouse to the enclosed unpacking room within the lithium extraction workshop. Inside the unpacking room, the NCM battery black mass is manually unpacked and dropped into the silo through the feed port. Pneumatic conveying pipes then transport the powder from the silo to the slurry mixing tank. Above the unpacking room, a negative pressure collection system with a 10,000 m³/h air volume is installed. The dust generated by unpacking is collected by negative pressure, then treated with a three-stage bag filter before being discharged through a 20m-high exhaust stack.

2. Acidification

Two 30m³ dilute sulfuric acid preparation tanks are installed in the lithium extraction workshop. 98% sulfuric acid, the raw material, is pumped directly from the tank farm into the tanks via sealed pipes. The sulfuric acid is then prepared into the 4 mol/L sulfuric acid needed for lithium extraction. The sulfuric acid mist generated in each tank is collected through sealed pipelines and fed under negative pressure into a 20cm φ gas collection main. After treatment with a three-stage alkali solution spray, it is discharged through a 20cm high exhaust stack.

3. Slurry preparation

Add pure water, prepared 4mol/L sulfuric acid and primary washing water from the lithium extraction workshop into the slurry mixing tank respectively, then add the NMC battery black mass into the slurry mixing tank, stir and mix the slurry evenly at room temperature, and pump it directly into the leaching tank through the pipeline.

4. Before the leaching slurry enters the leaching tank, nitrogen is used to replace the air in the tank. After the slurry is directly pumped into the leaching tank through a pipeline, additives are added to the leaching tank, and finally steam is introduced. Mix and stir for about 1-2 hours. The leaching reaction temperature is 60℃-80℃.

The leaching process reaction is as follows:

MnSO₄+H₂O=Mn(OH)₂+H₂SO₄

CoSO₄+H₂O=Co(OH)₂+H₂SO₄

NiSO₄+H₂O=Ni(OH)₂+H₂SO₄

2LiNi0.6Co0.2Mn0.2O₂+H₂SO₄=Li₂SO₄+0.4MnO₂+0.4CoO+1.2NiO+H₂O+0.3O₂

O₂+C=CO₂

After the leaching reaction is completed, the material is pumped into the filter press for filtration, and the lithium-rich solution obtained by filtration enters the subsequent impurity removal process; the nickel-cobalt-manganese mixture (water content 30%) obtained by filtration is then washed and filtered twice before being packaged and transported to the NMC battery leaching and extraction workshop for use.

The sulfuric acid mist generated in the leaching tank is collected through a closed pipeline and then fed into a φ20cm gas collecting main pipe under negative pressure. It is then treated with "three-level alkali solution spraying" and discharged through a 20cm high exhaust pipe; all the water washing filtrate is reused as production make-up water and is not discharged externally.

5、Remove impurities

The lithium-rich solution is piped through a sealed container to a decontamination tank, where a 32% caustic soda solution is added. The pH is controlled between 8 and 10, the reaction temperature is maintained at 60°C, and the reaction time is controlled at 2 hours. After the reaction time has expired, the slurry is pumped to a filter press for solid-liquid separation, which lasts for 2 hours. The resulting nickel-cobalt hydroxide (30% moisture content) is then washed twice with water and filtered, then bagged and transported to the NCM battery leaching and extraction workshop for future use. The wash filtrate is fully recycled back into the slurry mixing tank as production feed water and is not discharged.

After impurities are removed, the lithium-rich solution must be further defluorinated using a defluoridation agent (primarily composed of polyaluminum sulfate). The resulting fluoride residue undergoes two stages of water washing and filter pressing. The wash filtrate is fully recycled back into the slurry mixing tank as production feed water and is not discharged. The fluoride residue, with a moisture content of 30%, is temporarily stored in the plant's hazardous waste storage facility as solid waste awaiting identification.

The lithium-rich solution after fluorine removal is then precisely filtered and sent to the lithium precipitation workshop as the raw material solution for preparing lithium carbonate.

Leaching process

The NCM leaching and extraction workshop features an acid preparation area, equipped with two 100m³ 98% concentrated sulfuric acid transfer tanks, one 100m³ hydrochloric acid transfer tank, six 2mol/L sulfuric acid preparation tanks, and two 6mol/L hydrochloric acid preparation tanks. All acid tanks and immersion tanks within the NMC leaching and extraction workshop are covered. Liquid materials are transferred via pipeline pumping. The tank covers are equipped with air extraction holes that directly and tightly connect to the collection pipeline.

1. Acidification

The raw materials, 98% sulfuric acid and 30% hydrochloric acid, are pumped directly from the tank farm into transfer tanks in the acid blending area through sealed pipelines. These tanks are then mixed into 2 mol/L sulfuric acid and 6 mol/L hydrochloric acid for the production line, respectively. Acid mist generated within each tank is collected through sealed pipelines and fed under negative pressure into a 20cm φ gas collection manifold. After undergoing a three-stage alkali spraying, demisting, and two-stage activated carbon adsorption process, it is discharged through a 20cm high exhaust stack .

2. Slurry preparation

First, add condensed water to the slurry mixing tank, then add the nickel-cobalt-manganese mixture and nickel-cobalt hydroxide to the slurry mixing tank, maintaining a solid-liquid ratio of 1:1, and stir for 30 minutes before stopping. The slurry is directly pumped into the low-acid leaching tank in the leaching workshop through a pipeline.

3. Acid leaching

A two-stage countercurrent acidic reduction leaching process is used, with the first stage being a low-acid leaching process and the second stage being a high-acid leaching process. Low-valent oxides (NixMnyCo1-x-yO) in the raw materials can be directly leached using sulfuric acid, while high-valent oxides (NixMnyCo1-x-yOz, 1<z<2) require the addition of a reducing agent for reduction leaching. The proposed project uses a two-stage countercurrent acidic reduction leaching process to dissolve metal compounds such as nickel, cobalt, manganese, copper, lithium, aluminum, and iron in the powder with sulfuric acid to form a sulfate solution. Some high-valent cobalt and manganese are reduced to divalent metal ions and enter the leachate. The leaching process primarily produces the following reactions:

Ni(OH)₂+H₂SO₄→NiSO₄+2H₂O

NixMnyCo1-x-yOz+H₂SO₄+H₂O₂→NiSO₄+MnSO₄+CoSO₄+H₂O+O₂↑

NixMnyCo1-x-yO+H₂SO₄→xNiSO₄+yMnSO₄+(1-x-y)CoSO₄+H₂O

Ni(OH)₂+H₂SO₄→NiSO₄+2H₂O  

Co(OH)₂+H₂SO₄→CoSO₄+2H₂O

Mn(OH)₂+H₂SO₄→MnSO₄+2H₂O

Cu(OH)₂+ H₂SO₄→CuSO₄+2H₂O

2Al(OH)₃+ 3H₂SO₄→Al₂(SO₄)₃+3H₂O

2Fe(OH)₃+ 3H₂SO₄→Fe₂(SO₄)₃+3H₂O

（1）Low acid leaching

The first stage of leaching is low-acid leaching, with the endpoint pH controlled between 1.5 and 2. Steam is introduced to maintain the reaction temperature at 80°C to 100°C, the reaction time at 16 hours, and the solid-liquid ratio at 1:3-5. The slurried slurry is then transferred to a low-acid leaching tank via a sealed pipeline. After the raw materials are added, 2 mol/L sulfuric acid and 27.5% hydrogen peroxide are slowly added to the tank as leaching agents. After the leaching time is reached, the low-acid leaching slurry is pumped to a filter press for liquid-solid separation, which lasts for 2 hours. The low-acid leachate from the filter press flows by gravity into a low-acid leaching filtrate transfer tank for temporary storage before being pumped to the subsequent copper removal process. The low-acid leaching residue from the filter press is re-slurried in the slurry mixing tank and then enters the second stage of high-acid leaching. The acid mist generated during the low-acid leaching process is treated with "three-stage alkali solution spraying + demisting + two-stage activated carbon adsorption" and then discharged through a 20m high exhaust pipe.

（2）High acid leaching

The second stage of leaching is high-acid leaching, with the pH at the leaching endpoint controlled between 0.5 and 1.0. Steam is introduced to maintain the reaction temperature at 60°C to 95°C, the reaction time at 8 hours, and the solid-to-liquid ratio at 1:3-5. The low-leaching residue is mixed in a slurry mixing tank with the high-leaching residue washing filtrate, the copper-removing slag washing filtrate, and the iron- and aluminum-removing slag washing filtrate. The mixture is then piped to the high-acid leaching tank, where 2 mol/L sulfuric acid and 27.5% hydrogen peroxide are slowly added as leaching agents. After the leaching time is reached, the high-acid leaching slurry is pumped to the filter press for liquid-solid separation, and the filtration time is 2 hours; the high-acid leaching liquid obtained by filtration flows into the high-acid leaching filtrate transfer tank for temporary storage, and then returns to the low-acid leaching tank for further leaching; the high-acid leaching residue (carbon black) obtained by filtration has a moisture content of 50% after two-stage water washing and filtration, and is temporarily stored in the hazardous waste temporary storage warehouse in the factory area as solid waste to be identified.

The acid mist generated during the high-acid leaching process is treated with a three-stage alkaline solution spraying, mist removal, and two-stage activated carbon adsorption process before being discharged through a 20-meter-high exhaust stack. The filtrate from the high-acid leaching residue wash is fully recycled into the low-acid leaching residue slurry tank as production feed water and is not discharged externally.

4. Removal of copper

The low-acid leachate is piped to a copper removal tank, where sodium thiosulfate and sodium carbonate are added. The pH is controlled between 3 and 5, and steam is introduced to maintain a reaction temperature of 50°C to 80°C for a reaction time of 6 hours. After the reaction time is reached, the copper removal slurry is pumped to a filter press for liquid-solid separation, which lasts for 2 hours. The copper slag obtained by filtration, after washing and filtration, has a moisture content of approximately 30%. It is temporarily stored in the plant's hazardous waste storage facility as solid waste awaiting identification. The filtrate is then pumped to the low-acid leachate slurry tank via a pipeline as production feed water.

5. Removal of iron and aluminum

After copper removal, the low-acid leachate still contains impurities such as iron and aluminum, requiring further impurity removal. Therefore, the low-acid leachate is pumped through a pipeline into an iron removal tank. 27.5% hydrogen peroxide and sodium carbonate are added to the iron removal tank to control the pH between 3.5 and 5. The reaction temperature is then controlled at 50°C to 80°C using steam heating. After stirring for 2-3 hours, the reaction is considered complete when the Fe content in the slurry is ≤ 0.1 g/L and the Al content is ≤ 0.20 g/L. The slurry is then pumped to a filter press for liquid-solid separation, which lasts for 2 hours. The resulting iron-aluminum slag undergoes two stages of water washing and filtration, resulting in a moisture content of approximately 30%. This slag is then stored in the hazardous waste storage facility within the plant as solid waste awaiting identification. The filtrate is then pumped through a pipeline into the low-acid leachate slurry tank as production feed water.

6. Parameter-adjusted precision filtration

The low-acid leachate after iron and aluminum removal is sent to the extraction process after precision filter pressing .

Black mass leaching process flow chart