Coal Mill Fan for Captive Power Plants

The process

Captive power plants at process industries run AFBC, CFBC or grate boilers on coal, lignite, husk or bagasse. The fan set is the boiler fan set, sized for the fuel and for a plant that cannot afford a stop.

The gas at the fan

Fluidised bed combustion carries bed material fines and fly ash in the flue gas. The dust is abrasive and the loading ahead of the collector is high, so the ID fan is placed after the dust collector wherever the layout allows.

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 with a shaft cooling disc and bearings outside the casing
Also specified	Hard facing or liners on the blade pressure face
Density at the fan	At about 160°C the gas density is close to 0.81 kg/m³, 68% 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 captive power plants

Coal Mill Fan in other processes

Services on this fan

Information needed to select or quote

1. Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
2. Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
3. Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
4. Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.