An air-to-air heat exchanger in NMP (N-Methyl-2-pyrrolidone) heat recovery systems works by recovering thermal energy from hot, solvent-laden air (usually from drying or coating processes) and transferring it to incoming fresh air, without mixing the two streams. This reduces energy consumption and helps condense and recover NMP for reuse.

Here's how it works:

1. Exhaust Air (Hot, NMP-laden):
   Warm air containing NMP vapor exits from the production process (e.g., a lithium battery electrode drying oven).

2. Heat Exchange Process:
   This exhaust air passes through one side of the air-to-air heat exchanger (usually a plate or rotary type made of corrosion-resistant materials like coated aluminum or stainless steel).
   On the other side, cooler fresh air flows in the opposite direction.

3. Heat Transfer:
   The heat from the exhaust air is conducted through the metal plates to the incoming fresh air, warming it up without allowing NMP vapor to cross over.

4. Energy Savings:
   The pre-heated fresh air then enters the process (e.g., drying oven), requiring less energy to reach the target temperature.

5. NMP Condensation (optional second stage):
   After heat is extracted, the exhaust air (now cooler) can go to a condenser or scrubber, where NMP vapor condenses and is collected for reuse.

Key Benefits:

• Energy Efficiency: Reduces the need for new heat energy by reusing waste heat.

• Solvent Recovery: Prepares the exhaust air for effective NMP condensation downstream.

• Environmental Compliance: Reduces NMP emissions.

• Process Stability: Helps maintain consistent drying conditions.