Kiln riser and preheater tower ducts
Tertiary air, kiln riser and preheater outlet: the hottest and dustiest positions on a cement line.
The kiln riser and the tertiary air duct are the two positions where a cement plant damper is asked to work at the edge of what steel can do. Gas leaves the kiln at 350 °C to 400 °C, sometimes higher during upset, carrying raw meal dust that is both hot and abrasive.
Temperature margin
We design the blade and frame for 450 °C so that an upset does not distort them. That margin costs a little in material and nothing in operation, and it removes the most common cause of a seized damper on a kiln line. Where the client's process control can guarantee a lower limit, we will design to it, but we will say what we assumed.
Dust build-up
Material builds up on the upstream face of any obstruction. Blade profiles on these gates are angled so that dust slides off rather than accumulating, and the frame is set flush with the duct so there is no ledge at the joint. A purge of plant air at the guide, at low volume, keeps the guide clear between strokes.
Expansion
The duct between the kiln and the preheater moves significantly between cold and hot. The gate frame must not become a structural anchor. We show slotted holes and the fixed point on the drawing, and we recommend that the duct designer confirms the movement figures before the spool piece is fabricated.
Tertiary air
Tertiary air dampers modulate to control kiln hood draft and calciner temperature. They cycle continuously, so the linkage and the actuator bear the wear rather than the blade. Hardened pins, reamed fits and an actuator rated for continuous duty are the specification points that matter.
Talk to us about this duty
Send the duct section, design temperature, pressure difference and the duty point. We reply with the gate type, the material selection, the drive and a general arrangement drawing for approval.