Abstract: In the commission period of 600MW boiler unit in Qiandong Power Plant, some abnormal phenomena in BBD mill pressure directfired system were occurred in varying degrees which are as follow: the raw coal bin became empty, coal feeder discontinued, top and lower shutters became jammed and not flexible, coal feeder and coal feeder cleaning motor went wrong frequently, etc., even the over temperature and burning damage in coal feeder were occurred. The reason, feature and hazard of these abnormal phenomena in milling system were analyzed, and relevant technical measures were proposed and then adopted, so the safe and economical operation of boiler unit was assured.

Key words: BBD mill, milling system, analysis of abnormal phenomena, technical measures, high-duty power boiler