Calciner blockages during AFR firing are not a slow drift — they tend to arrive over hours, not days. Sticky ash from low-quality AFR, low melting-point compounds in the substitute fuel, and chloride or alkali cycling all combine to bond material to refractory in places the calciner was not designed to be cleaned. The blockage stops the kiln, and even after clearance the chemistry that produced it is still in the system. Restarting on the same fuel mix usually re-creates the problem within a campaign.
Why this matters in the afr / alternative fuels
A calciner blockage during AFR is one of the most expensive AFR-related events a plant can experience. The kiln stops, refractory in the calciner sees thermal shock during recovery, and the cleaning operation itself can damage cyclone steelwork that takes weeks to repair properly. The campaign loses days, the AFR programme loses credibility with operations, and the economics of substitution shift unfavourably for months while everyone waits for confidence to return.
The deeper cost is institutional: every AFR-driven blockage makes future substitution proposals harder to approve, even when the next AFR supplier is genuinely better. Treating these events as chemistry problems with a long memory — not isolated cleaning incidents — is the only durable approach.