The problems that made ID fans to stall and the load of unit to fluctuate due to unsuitable auto-control of the booster fans' inlet guide vane in system of limestone/gypsum wet flue gas desulphurization (FGD) in recent years have been analysed

as well as the fluctuation of furnace draft and damage of equipments positioned in flue duct of the tail section due to fault close of raw/clean gas dampers being considered.For this

the optimization of control system for original FGD system has been carried out

i.e.the inlet flue gas pressure of booster fan is used as controlled variable

and the open degree of ID fan's damper after processing is used as front feed

and through proportional integral regulator to constitute a constant value composite control system to regulate inlet flue gas pressure of the booster fan

and triggering the main protection system of FGD within 3 s after eliminating the open signal of clean gas damper.After optimization

through application on 2×310 MW units in one power plant

the problems existing in control system of original FGD facility have been comparatively well resolved.