Based on analysing the design of run back(RB)control for 2×600 MW units in the second-phase project of Huaneng Yimin Power Plant

directing against existing problems

such as overtemperature of the high-temperature flue gas entrained by the blower coal pulverizer to be used for drying

the limited capability of cold air to be used for adjusting outlet temperature of the coal pulverizer leading to activation of the protection for high outlet temperature from the coal pulverizer etc.

the improvement of RB control has been carried out.The target load of RB has been adjusted

the corresponding fuel amount being reduced to 35%

the control logic during process of RB to stop the coal pulverizer being optimized.The test shows that the RB control after improvement can satisty the requirement of rapidly and stably decreasing load of the unit.