A vertical screen multi mill uses rotating impeller blades sweeping material radially outward through a vertical cylindrical screen (0.5–20 mm aperture) the vertical orientation exploits gravity to continuously discharge sized granules downward through the screen without accumulation in the sizing zone. Processing 5–1,500 kg/h at impeller speeds of 500–3,000 RPM, it achieves lower heat generation than horizontal configuration (shorter product dwell time), superior handling of free-flowing dry granules, and direct in-line discharge to collection equipment positioned directly below the mill body.
Feed enters axially from the top; the vertical impeller shaft projects blades radially outward at 500–3,000 RPM. Centrifugal force drives material toward the cylindrical screen wall blades sweep material along the inside of the vertical screen from top to bottom, sizing it progressively as it travels downward under gravity. Sized product passes radially through the screen and falls into the collection vessel below. The vertical geometry reduces product residence time in the milling zone by 30–50% compared to horizontal screens at equivalent throughput reducing fines generation and heat build-up. Screen and impeller change in under 5 minutes without tools.
Challenges
Non-Uniform Residence Time Distribution from Top-to-Bottom Gravity Flow
Material entering the top spends less time in the milling zone than feed further down PSD broadens.
Screen Panel Fatigue from Continuous Radial Blade Load
Repeated radial force on vertical screen panels fatigues attachment welds cracks at screen frame.
Feed Rate Sensitivity Gravity Flow Limits Maximum Throughput
At high feed rates material piles above the screen inlet bypasses milling zone at screen top.
Dry Powder Cohesion Causing Bridging at Vertical Inlet
Cohesive dry powder bridges across the vertical top inlet starves impeller of feed material.
Fines Elution Downward Without Adequate Screen Contact at High Speed
At very high impeller speed, fine particles exit before adequate blade contact product too coarse.
Solutions
- Variable Feed Rate Matched to Impeller Speed (Feed-Speed Ratio PLC Control): PLC links feed rate to impeller speed maintains target material depth in milling zone at all throughputs.
- Ribbed Screen Frame with Gusset Reinforcement at Panel Attachment Points: Structural ribs and gussets distribute radial blade load uniformly prevent panel fatigue cracking.
- Inlet Flow Regulator (Rotating Disc at Top Inlet, VFD-Controlled): Rotating disc at vertical inlet limits maximum entry rate prevents material pile-up above milling zone.
- Anti-Bridge Agitator at Vertical Inlet (Rotating Finger, 10–20 RPM): Slow rotating agitator above inlet prevents cohesive powder bridging continuous reliable feed.
- Staggered Impeller Blade Height (3 Blade Rows at Different Axial Positions): Multiple axial blade rows create overlapping milling zones all material contacts blade regardless of entry position.
Applications
- Pharmaceutical: Dry granule sizing and roller compaction ribbon milling free-flowing granule direct-to-IBC discharge.
- Food & Beverage: Free-flowing food granule sizing, breakfast cereal sizing, spice granule milling with direct bin discharge.
- Chemical: Free-flowing catalyst granule sizing, specialty chemical granule milling vertical geometry reduces heat.
- Nutraceuticals: Free-flowing supplement granule sizing, protein granule milling low heat generation preserves enzyme activity.
- Cosmetics: Free-flowing mineral pigment granule sizing vertical discharge to compact press IBC.
Models & Capacities
| Type 3BÂ Vertical Screen Multi Mill: Models & Capacities | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Model | Scale | Throughput [kg/h] | Impeller Speed [RPM] | Screen Aperture [mm] | Tip Speed [m/s] | D90 Output [µm] | Fines [%] | Motor [kW] | L × W × H [mm] | Weight [kg] |
| MM-V-LAB | Lab | 5–25 | 500–3,000 VFD | 0.5–20 | 1–7 | 200–4,000 | <2 | 0.75–1.5 | 480×380×820 | 48 |
| MM-V-PIL | Pilot | 15–80 | 500–3,000 VFD | 0.5–20 | 1–8 | 200–4,000 | <2 | 1.5–3.0 | 680×500×1,050 | 95 |
| MM-V-250 | Production | 60–250 | 500–2,500 VFD | 0.5–20 | 2–9 | 250–4,000 | <2 | 3.0–7.5 | 900×640×1,300 | 195 |
| MM-V-600 | Production | 150–600 | 500–2,500 VFD | 0.5–20 | 2–9 | 300–4,000 | <2 | 7.5–15 | 1,150×820×1,600 | 365 |
| MM-V-1000 | Production | 300–1,000 | 500–2,000 VFD | 0.5–20 | 2–8 | 350–4,000 | <2 | 15–22 | 1,450×1,050×1,950 | 620 |
| MM-V-1500 | Large Prod | 500–1,500 | 500–1,800 VFD | 0.5–20 | 2–8 | 400–4,000 | <2 | 22–37 | 1,750×1,250×2,300 | 980 |