WE GOT THE ALARM ON THE #3 KILN FIRING SYSTEM. THIS AUTOMATICALLY STOPS THE COAL BELT, SCREW, & ROTARY AIRLOCK THE FEEDS THE COAL MILL. AFTER ALARM CLEARED THE COAL FEED GROUP WAS RESTARTED. A LOUD NOISE WAS HEARD FROM THE COAL MILL AREA. (THE BELT & SCREW HAD NOT BEEN STARTED.) OCCASIONAL SPARKS COMING OUT OF THE COAL TRAP WERE OBSERVED. RUPTURE DISC ON TOP OF CYCLONE WAS DAMAGED.