The invention relates to a kind of spraying water-amount controlling
system and its method in stack gases desulfurization industrial art with semi-
drying way, which belongs to the field of stack gases desulfurization industrial art in form of semi-
drying. The feature of the invention is that as follows: in inlet
flue, there is a
relative humidity probe; according to the data of inlet
flue, the data of outlet
flue and the data of amount of
water spray in desulfurizing
tower, the data handling apparatus can calculate the temperature of near adiabatic saturation or the temperature of near-
dew port in the outlet of desulfurizing
tower, and then compares them with the corresponding setting value. Then by the difference of comparing, it can control the open and shut of
electromagnetic valve in order to realize the precise control of spraying water amount. At the same time, the invention raises a full range method of controlling computers. Finally, the invention can prevent from the problem of being stained with dust and the
corrosion problem of costly
relative humidity probe efficiently, so it has high reliability and high economy.