Total Pressure: The sum of all system resistances: inlet losses, mill pressure drop (a major component, typically 4000-8000 Pa for a vertical mill), classifier loss, ducting losses, and the backpressure of the final dust collector (bag filter). A detailed pressure drop calculation for the entire gas path is mandatory.
Fan Type Selection:
Primary Air Fan: Typically a single-stage, high-pressure centrifugal fan. It must handle pre-heated air (200-400°C), so material and cooling of bearings/shaft must be considered. It often requires a variable speed drive or inlet guide vanes for control.
Exhaust/Mill Fan: Usually a heavy-duty induced draft (ID) centrifugal fan, handling the dust-laden, moist air after the mill. It must be designed for erosion resistance (hardened blades, wear plates) and possible slight negative pressure operation to prevent dust leakage.
Key Selection Parameters: Fan efficiency (select a model operating near its best efficiency point at the duty point), material of construction (wear-resistant steels for exhaust fan), type of drive (direct vs. geared), and control method (VSD is optimal for energy savings).
