Abstract: In this paper, the runback control strategies for the world’s first 600-MW supercritical CFB unit of Baima Power Plant are ananlyzed. The analysis includes post-runback control mode switching, override interlock, deviation block, limit block and parameters change-over. With these control strategies, the runback actions can be completed highly automatically and the unit can be recovered to the target load at the optimal runback rate with all the main parameters controlled within the normal operation range. Moreover, during the fan runback, by performing the interlock and override functions, the furance pressure control quality is improved; and during the feedwater pump runback, lower target load is more helpful for the steam/water system heat balance. By adopting the desuperheating control based on the physical mechanism model, the fast increase of steam temperaure can be inhibited, and by adopting the two-staged priamry air control, boiler normal fluidizing and bed pressure balance can be ensured. The runback tests show that the control quality of these strategies are good enough for popularization.

Key words: 600 MW, supercritical unit, CFB, runback (RB), control strategy