Plate-fin Air-to-air Heat Exchangers in The Lithium Battery Drying Process

In the lithium battery drying process, the plate-fin air-to-air heat exchanger's core function is to recover the sensible heat of high-temperature waste gas containing NMP, preheat fresh air, and create low-temperature conditions for downstream NMP condensation, achieving both energy savings and solvent recovery.

Waste gas source: Exhaust gas from the oven after positive electrode coating, 80–120℃, containing NMP vapor (boiling point 202℃), trace dust, and low humidity.

Key challenges: High energy consumption from direct emissions, NMP waste, and failure to meet environmental standards; high downstream condensation load.

Heat exchanger role: Gas-to-gas sensible heat recovery; does not directly condense NMP, only cools and preheats fresh air.

Flowchart: Fresh air (20–25℃) → Plate-fin heat exchanger (preheated by waste gas) → Oven heater → Drying; Oven waste gas (80–120℃) → Plate-fin heat exchanger (heat release and cooling) → Condensation unit (NMP recovery) → Tail gas treatment/emission. Heat Exchange Mechanism

Plate-fin structure: Aluminum/stainless steel fins + baffles, counter-current heat exchange, thermal efficiency 70–90%.

Complete isolation: Independent fresh air/exhaust gas channels, no cross-contamination, ensuring clean electrode surfaces.

Temperature changes: Exhaust gas 80℃→40–50℃; Fresh air 20℃→50–60℃.

NMP Recovery System Complete Chain

Waste heat recovery section: Plate-fin heat exchanger, exhaust gas 80℃→45℃, fresh air preheating, energy saving 30%+.

Condensation recovery section

Level 1: Circulating water cooling (45℃→30℃), preliminary condensation.

Level 2: Chilled water cooling (30℃→15–18℃), deep condensation, NMP recovery rate ≥85%.

Post-treatment section: Activated carbon adsorption/rotary concentrator, exhaust gas NMP ≤300ppm, meeting emission standards.

Core Advantages

Energy Saving: Fresh air preheating reduces steam/electric heating, saving millions of units of energy annually.

Recycling: Exhaust gas cooling improves downstream NMP condensation efficiency, with a recovery rate of 85-95%.

Safety: Isolation design prevents cross-contamination; NMP concentration < lower explosive limit.

Economy: Investment payback period of 6-12 months, long-term cost reduction.