The process
A vertical roller mill grinds and dries raw meal in one body, with hot kiln gas drawn up through the table and separator by the mill fan. The fan carries the full product stream to the bag filter or cyclones, so the dust load is the heaviest on the line and the wheel is built for wear.
The gas at the fan
Hot gas that has dried the raw meal and now carries the fine product toward the separator and collector. Very heavy fine dust loading; the impeller is built for wear and balanced to tolerate build-up.
Selection for this duty
| Blade form | Radial tipped with wear liners, or straight radial where the dust is coarse |
| Material of construction | Mild steel with replaceable wear liners on the blades and the scroll at the cut-off |
| Drive and bearings | Direct coupled or belt driven; belt drive where the duty point may need tuning at site |
| Also specified | Hard facing or liners on the blade pressure face |
| Density at the fan | At about 90°C the gas density is close to 0.97 kg/m³, 81% of standard air. Pressure developed and power drawn fall in the same ratio, so the selection is made at this density and the motor is checked at cold start. |
Draws hot kiln gas through the raw mill and separator, drying the raw meal on the way and carrying the fine product to the collector. Heavy fine dust, so wear protection on the impeller is standard. Client-stated blade types for the Raw Mill Fan in general: Backward curved and radial tipped.
Industries
Other fans in vertical roller raw mills
Raw Mill Fan in other processes
Services on this fan
Information needed to select or quote
- Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
- Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
- Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
- Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.