When calciner temperature swings outside the band the design and the kiln control loop were tuned for, the AFR feed is almost always the cause. Inconsistent particle size, moisture batches, calorific value variation between deliveries, or simply a dosing system that cannot meter the AFR cleanly — each pushes the calciner off its setpoint. The kiln sees the result downstream as inconsistent meal calcination, and the operator absorbs the swings manually until the loop becomes the disturbance instead of the response.
Why this matters in the afr / alternative fuels
Calciner temperature stability is one of the foundations of stable kiln operation. When it swings, every downstream parameter swings with it — meal calcination, kiln backend temperature, free lime, even ring formation tendency. The kiln's operating window narrows, and the operator's attention is consumed managing a calciner that was supposed to be stable.
The AFR programme also pays a cost: substitution rates have to be backed off to keep the swings inside acceptable bounds, and the economic case for the AFR weakens. Better feed-handling, AFR pre-blending, and more disciplined acceptance criteria for incoming deliveries usually pay back faster than any control-system tuning the swings might appear to need.