Turk, A low NOx precalciner has staged combustion at different parts of the precalciner to create a zone with reducing conditions which destroys NOx formed in the burning zone of the kiln. Best regards Dr Michael Clark

There could be many causes for such a sudden rush of material in the burning zone. Possibly the breakaway of some coating or a ring. A sudden change in feed chemistry or fuel calorific value. It is impossible to diagnose the cause without much more information. Thanks Dr Michael Clark