Industry: New‑energy battery material manufacturing

Application Scenario: Deep dehydration of nano‑alumina (α‑Al₂O₃) for lithium‑ion battery separator coating (applied to high‑safety solid‑state battery separator coatings).

I. Core Pain Points

A new‑energy material manufacturer faced the following challenges with the conventional spray‑drying process when producing nano‑alumina slurry:

- **Crystal structure damage**: High‑temperature hot air (inlet temperature ＞200 °C) triggers phase transformation from α‑phase to γ‑phase, reducing coating insulation performance by 30%.
- **Unqualified moisture content**: Finished product moisture ＞1%, resulting in large fluctuation of separator porosity after coating and shortened battery cycle life.
- **Severe agglomeration**: Hard agglomerate proportion of dried nano‑particles (D50=50 nm) exceeds 15%, requiring additional grinding and raising production costs.

II. Solution

1. Custom Vacuum Rake Dryer

Equipment Parameters

- Model: ZPG‑2000V
- Volume: 2 m³; material: 316L stainless steel with PTFE anti‑stick coating
- Vacuum degree: ‑0.098 MPa (absolute pressure: 200 Pa)
- Temperature control: 60‑80 °C (segmented temperature control, accuracy ±1 °C)
- Rake arm speed: 5‑15 rpm, stepless adjustable

Special Design

- Built‑in ultrasonic crushing module (28 kHz frequency) to break nano‑particle agglomerates in real time.
- Condenser integrated with molecular‑sieve adsorption system for recovering residual isopropanol solvent from moisture (recovery rate ＞95%).

2. Four‑Stage Drying Process

1. Pre‑cooling crystallization: Slurry (40% solid content) is cooled down to 5 °C to precipitate uniform crystal nuclei.
2. Low‑temperature dehydration: 60 °C / 6 h (vacuum degree ‑0.095 MPa) to remove free water down to 5% moisture content.
3. Ultrasonic de‑agglomeration: Ultrasonic device activated at 70 °C for 4 h with simultaneous raking agitation; moisture content reduced to 0.5%.
4. Inert‑gas protection: Back‑filled with argon after drying; oxygen content kept below 10 ppm for direct encapsulation.

III. Operation Results

Performance Improvements

- α‑phase alumina purity ＞99.9%; coating dielectric strength reaches 300 V/μm (only 220 V/μm with the original process).
- Dried particle D50=55 nm; hard agglomerate proportion ＜3%, eliminating the need for secondary pulverization.