The process
The dry process kiln line is a chain of fans from the cooler to the stack. The preheater fan sets the kiln draft through the cyclone stages, the raw mill fan draws the hot gas through the mill, the cooler fans blow and exhaust the clinker bed, and the coal mill fan carries pulverised fuel to the burner. Every gas stream carries abrasive dust at temperature.
The gas at the fan
Kiln gas leaving the preheater carries fine raw meal dust at high temperature. The fan runs hot and dusty for years between stops, so wear liners, a shaft cooling disc and bearings outside the gas path are standard.
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, shaft cooling disc, bearings in a pedestal outside the gas stream, allowance for thermal growth |
| Also specified | Hard facing or liners on the blade pressure face |
| Density at the fan | At about 330°C the gas density is close to 0.59 kg/m³, 49% 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. |
Blows ambient air up through the grate of the clinker cooler. Each compartment has its own fan set for the pressure that bed needs. Client-stated blade types for the Cooler Compartment Fan in general: Backward curved and radial tipped.
Industries
Other fans in cement preheater kilns
Cooler Compartment Fan in other processes
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.