Generation and recovery control of NMP in lithium battery production

NMP is mainly used and discharged in the positive electrode material preparation process, and the main process of using NMP is as follows:

Coating: The positive electrode slurry (lithium nickel cobalt manganese oxide, conductive carbon black, nmp solvent, adhesive PVDF mixture) is evenly coated on both sides of the aluminum foil with a coating machine;

The dryer adopts a closed negative pressure exhaust dryer (drying channel) 1 methyl 2 pyrrolidone. During the coating process, only a small amount of NMP volatilizes at the inlet and outlet of the coating machine, and the exhaust gas in the dryer is led to the exhaust gas treatment facility through the induced draft fan, and is discharged at high altitude; due to insufficient drying, a very small amount of NMP exhaust gas volatilizes unorganized in the workshop .

Baking: After coating, dry the positive electrode in a vacuum dryer at 120 ± 5 °C to remove the NMP component on the electrode. The dried gas is recycled to the NMP recovery unit.

To sum up, NMP is mainly used in the coating process in lithium battery production, and then the recycling control of nmp.

NMP Recycling Control Measures

The principle of NMP recovery treatment process: the NMP gas that is generated in the coating machine in the coating workshop is sucked away by the exhaust fan, and enters the NMP recovery technology equipment through various pipeline systems, and the cooling water and chilled water coil are used to make NMP from It is condensed in the air (the temperature is about 5°C during the cooling process), and then can be purified through data collection to achieve the purpose of corporate recycling research.

NMP recovery process

During the production of lithium-ion batteries, the temperature of NMP in the exhaust gas from the coating machine is very high. The front stage uses water vapor and gas-gas heat exchange to cool the condensed exhaust gas and recover most of the NMP. The remaining exhaust gas enters the post-processing system and is discharged after treatment.

Process flow: After the exhaust gas is cooled, the packing in the tower is wetted by the process water. The 304 stainless steel packing has a large specific surface area, and the waste gas is in full contact with the process water, and melts to the bottom of the packing to complete recovery. As the number of melting cycles increases, the concentration of NMP waste liquid increases. When the set concentration (≥80%) is reached, part of the tail gas enters the secondary absorption tower with low concentration of process water, and then the low-concentration tail gas is washed and finally discharged.

In the currently commonly used NMP recovery process, the NMP liquid concentration sensor MSDR-SH70-DP is installed on the circulation pipeline in the spray tower to monitor the concentration of the NMP solution online in real time.

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