Abstract: The designed coal of the 2020t/h of Huadian International Zouxian Power Plant project phase III is local soft coal. For the near term, the fired coal quality was changed greatly due to the insufficient coal supply. In a certain period after the coal grade was changed, the unstable boiler combustion was often occurred or the furnace negative pressure was rocked in largescale amplitude, and the temperature of main steam and reheated steam can not reach the required value; even the boiler flame out accident was happened. This became a serious potential hazard for stable and economical operation of unit. The reasons of this fault were analyzed. The relevant solution was proposed, and better result had been obtained.

Key words: boiler, burner, combustion adjustment, coal grade, stability