Air Classifier — a razor-sharp cut point
The THOR-AC Series sets the benchmark for dry powder separation — delivering razor-sharp D97 cut points through dynamic aerodynamic engineering. By balancing centrifugal acceleration against controlled aerodynamic drag, it removes fine dust fractions or isolates premium micro-fractions from bulk material. Available standalone or integrated directly inside our mills.
- Cut point
- D97 · 3 – 200 µm
- Mechanism
- Centrifugal + drag
- Efficiency
- Up to 92%
- Config
- Standalone / in-mill
Centrifugal out
Drag in
A spinning wheel throws heavy, coarse particles outward to the wall and down to reject, while the system fan's drag pulls light fines inward and up to the product outlet. Tune the wheel speed and the cut point moves — no mesh, no blinding.
- Cut D97
- 3–200µm
- Efficiency
- 92%
- Wheel Ø
- 100–630mm
- Control
- VFD
What is an Air Classifier?
An air classifier is an industrial dynamic dry-powder separation machine that uses aerodynamic drag and centrifugal force to separate fine particles from coarse particles.
As a specialist air-classifier supplier, THOR by CI designs these systems for a cleaner, sharper, more consistent cut point than traditional physical mesh screens — especially with fine, cohesive or highly abrasive materials down to single-digit-micron ranges. It elevates plant efficiency, narrows PSD and eliminates the physical limits of mechanical screening.
Where the classifier sets the cut
How it works
A force balance: centrifugal projection throws coarse out, aerodynamic drag pulls fine in. Where they balance is your cut point.
Pneumatic feeding
Raw powder is suspended in a controlled air stream and introduced into the separation chamber.
Centrifugal projection
The spinning wheel generates a strong centrifugal field, throwing coarse, heavy particles out to the walls.
Aerodynamic drag
The system fan draws air through the blades, pulling fine, light particles inward against the spin.
Fine up, coarse down
On-spec fines exit upward to the cyclone; oversize drops to the coarse port or recirculates to the mill.
Standalone, or built in
Run it as an independent process station, or mount it directly inside the mill — two ways to sharpen the same cut.
Stand-alone air classifier (THOR-AC Series)
An independent process station downstream of any secondary grinding mill — Ball, Pin or Hammer. Material is fed in via pneumatic conveying lines or gravity chutes. Primary advantages: highest separation yield efficiency (92%); a dedicated auxiliary intake fan precisely tunes the air-to-solid ratio; easy retrofit into existing plant lines — no change to the primary mill.
Integrated / in-mill classifier (THOR-IC Series)
Mounted directly inside the primary milling chamber — typically the upper zone of the THOR-JM Jet Mill or specialized Hammer Mills — forming a single integrated unit. Primary advantages: extremely compact plant footprint; eliminates external conveying lines and collectors between mill and classifier; instantly recirculates coarse rejects into the grinding zone — preventing over-grinding and cutting energy per ton.
Main components
Five precision assemblies that shape and control the aerodynamic field.
Dynamic classifier rotor wheel
A precision-balanced wheel with backward-curved ceramic or carbide blades that create the centrifugal field.
Classification housing
A conical separation chamber with tangential air inlets that guide and shape the airflow.
Adjustable guide vanes
Stator vanes surrounding the rotor that control the inlet air angle and flow velocity.
Rotor drive & inverter motor
A high-speed drive controlled by a VFD for precise, real-time wheel-speed adjustment.
Fine & coarse discharge ports
Flanged ports for clean, dust-free pneumatic connection to cyclones or mills.
Advantages & limitations
A sharper cut than any screen — provided the feed is milled and dry.
Advantages
Modular standalone versatility
Integrates into any grinding circuit — Hammer, Pin or Ball — of any brand.
Precise cut-point control (D97)
Adjustable wheel speed shifts the target top-cut anywhere from 3 µm to 200 µm.
High wear protection
Optional alumina-ceramic, silicon-carbide or polyurethane coatings for abrasive minerals.
High recovery yields
Optimized internal aerodynamics keep fines off the coarse fraction — up to 92% efficiency.
Limitations to plan for
Requires upstream grinding
It separates, it doesn't reduce — a pre-milled feed is required.
Moisture sensitivity
Above ~3% moisture, particles agglomerate — reducing efficiency and cut-point accuracy.
Cost of auxiliary fans
High separation velocities need high-pressure exhaust fans, raising capital and power cost.
Technical specifications & model range
Five wheel sizes. Final sizing is confirmed after pilot trials with your actual feed material.
| Model | Rotor wheel diameter | Motor power | Shell speed | Capacity |
|---|---|---|---|---|
| TH-AC-100 | Ø100 mm | 2.2 kW | 36 – 38 rpm | 0.65 – 2 TPH |
| TH-AC-200 | Ø200 mm | 5.5 kW | 36 rpm | 1.5 – 4.8 TPH |
| TH-AC-315 | Ø315 mm | 11 kW | 29.7 rpm | 2 – 5 TPH |
| TH-AC-450 | Ø450 mm | 22 kW | 25.4 rpm | 4 – 10 TPH |
| TH-AC-630 | Ø630 mm | 45 kW | 21.7 rpm | 15 – 28 TPH |
Specifications are typical and subject to change. Final sizing confirmed after pilot trials with your feed material.
Other platforms
The rest of the THOR family Compare or pair — air classifying is often integrated with a mill