Combined drying and grinding is technically feasible for NCM ternary cathode powder, yet it comes with strict limitations, especially for high‑nickel and single‑crystal grades. Whether this integrated process can be adopted depends on raw material moisture, NCM nickel content, thermal sensitivity and final PSD requirements. This article draws on JACAN dry processing know‑how from ncm‑mill.com.
Working principle of combined drying-grinding
In an integrated drying‑grinding system, hot inert gas (nitrogen) serves two purposes simultaneously:
- Carries heat to evaporate surface moisture from wet NCM feedstock.
- Acts as the conveying and classification medium to disperse, de‑agglomerate and classify powder inside the grinding circuit.
The feed enters the grinding chamber; hot gas flash‑dries the particles while mechanical impact or particle collision breaks soft agglomerates. Evaporated water vapor is removed with exhaust gas before powder collection. This eliminates a separate standalone drying unit and reduces material handling steps.
Suitable scenarios for combined drying & grinding
Combined drying‑grinding works best for mid‑nickel NCM with low to moderate incoming moisture (typically <0.5%).
- Raw material only has surface adsorbed moisture, not deep‑bound water.
- Target is gentle de‑agglomeration rather than heavy particle size reduction.
- Production layout is compact, and fewer material transfer steps are preferred to cut contamination risk.
Key risks for NCM, especially high‑nickel grades
This integrated process is not recommended for heat‑sensitive high‑nickel NCM and single‑crystal NCM, mainly due to three risks:
- Local overheating risk
Drying requires elevated gas temperature. Hot gas contacting fine NCM particles accelerates surface side reactions, increases residual lithium, triggers re‑agglomeration and caking, and degrades electrochemical performance. Even short flash heating can damage high‑nickel material surfaces. - Moisture vapor condensation risk
Water vapor released during drying may condense in cooler sections of the pipeline or classifier. Condensed water reacts with residual lithium, forming sticky lithium salts, which cause powder adhesion and unstable particle size distribution. - PSD control instability
Moisture content fluctuates batch by batch. Variable moisture changes agglomerate strength in real time, leading to drifting D50 and span. The gas temperature needed for drying conflicts with the low‑temperature requirement to protect NCM crystal surfaces.
Process design rules if combined drying-grinding is adopted
If users still select this combined setup for low‑nickel or mid‑nickel NCM, JACAN recommends these safeguards:
- Use nitrogen as heating medium instead of air to avoid oxidation. Keep heating gas temperature strictly limited to low flash‑dry ranges.
- Install dew point and temperature interlock sensors across the whole loop to monitor water vapor and prevent condensation.
- Optimize gas flow velocity to rapidly remove water vapor from the grinding zone, avoiding vapor accumulation.
- Apply ceramic lining throughout the system to reduce metal contamination.
- Add pre‑screening to remove large hard agglomerates before feeding.
Preferred industrial configuration for high‑nickel NCM
For high‑nickel and single‑crystal NCM, the safer and more reliable route is separate low‑temperature vacuum drying followed by inert‑atmosphere grinding and classification.
Raw powder is dried first under mild vacuum at low temperature to remove moisture without surface damage. Cooled dried powder is then fed into the closed nitrogen grinding circuit. This decouples thermal drying from particle size reduction, stabilizes PSD, and protects NCM electrochemical properties.
Drying and grinding can be combined for mid‑nickel NCM with low surface moisture, using hot nitrogen flash drying inside the grinding loop. However, this integrated method carries thermal degradation and condensation risks. For heat‑sensitive high‑nickel and single‑crystal NCM, the industry standard practice is to separate low‑temperature drying from grinding, to stabilize particle size and preserve cathode material quality.
