The process
The coal mill dries and grinds fuel for the kiln burner with hot gas drawn from the preheater or cooler. The mill fan handles gas carrying pulverised coal and is built spark resistant, with seal air keeping dust out of the bearings and a bag filter on the fine coal bin vent.
The gas at the fan
Gas carrying pulverised coal is combustible. Spark resistant construction with non-ferrous rubbing parts, a shaft seal and earthing of all components are required, with explosion relief on the system.
Selection for this duty
| Blade form | Radial tipped, or backward inclined where the fan sits after the collector |
| Material of construction | Mild steel |
| Drive and bearings | Direct coupled or belt driven; belt drive where the duty point may need tuning at site |
| Also specified | Spark resistant construction with non-ferrous rubbing parts, shaft seal, earthing and a flameproof or increased safety motor |
| Density at the fan | At about 80°C the gas density is close to 1.00 kg/m³, 83% 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 gas through the coal mill to dry and convey the pulverised coal to the burner or the fine coal bin. Built spark resistant because the gas carries combustible dust. Client-stated blade types for the Coal Mill Fan in general: Backward curved and radial tipped.
Industries
Other fans in cement plant coal mills
Coal Mill Fan in other processes
Services on this fan
Rotor Replacement and Performance EnhancementDynamic Balancing and Vibration AnalysisCondition Monitoring and Troubleshooting
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.