Graphite anode powder is the opposite of robust: flaky, low bulk density, cohesive and prone to both bridging in hoppers and segregation during transfer. Get either wrong and you lose tap density, coating uniformity and finally cell performance. The fixes are different for each problem, but both start with respecting the particle shape.
Bridging — Funnel Flow vs Mass Flow
In a funnel-flow hopper, material channels down the middle while the rest stagnates and cakes — a perfect bridge factory. Mass-flow geometry (steep, smooth-lined walls that move the whole bed) denies graphite the stagnant zones where arches form. Outlet size and half-angle come from a wall-friction and flow-function test on the actual lot, not a catalog value.
Anti-Arching Discharge
- Massaging frames — flexible walls activated intermittently; effective on cohesive flakes without compacting them
- Rotary lump breakers — for material already caked upstream (big bag, storage)
- Liner choice — PTFE or polished SS from the friction test, not a default
- Aeration — dry air only, never humid, or you feed the caking mechanism
Segregation — Why Velocity Matters
Dilute-phase conveying throws particles at 18-35 m/s. Flakes of different size and density follow different paths through elbows and vessels, so the powder segregates by the time it lands. Dense-phase moves material in slow plugs at 2-8 m/s, keeping the bed intact and the size distribution stable.
| Dilute-Phase | Dense-Phase (low-speed) | |
|---|---|---|
| Particle velocity | 18-35 m/s | 2-8 m/s |
| Flake breakage | High — wall impacts | Low — plug flow |
| Segregation | Likely by size/density | Minimal, bed moves as one |
| Tap density | Can drift | Stable batch to batch |
What Good Looks Like
- Flow test on the actual lot before hopper dimensions are frozen
- Mass-flow geometry with a friction-tested liner
- Intermittent discharge aids, never continuous vibration
- Dense-phase low-speed conveying specified for flake preservation
Free Flow Assessment
Send 5 kg of your graphite — our lab returns wall friction, flow function and a recommended hopper plus conveying configuration, free, with a test video.
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