Method of control for a wet lime-gypsum process desulfurization plant

Abstract

In an absorption tower of a wet lime-gypsum process desulfurization plant which desulfurizes an exhaust gas by bringing an incoming exhaust gas into contact with an absorbent liquid circulated therethrough by means of a plurality of pumps, an optimum pH value of the absorbent liquid and an optimum number of working pumps are set according to an amount of an exhaust gas load of the absorption tower, and a feed rate of the absorbent liquid and a number of working pumps are controlled on the basis of these set values. According to one mode of embodiment of the invention, a variation rate of the exhaust gas load and a desulfurization ratio are detected, and when the amount of exhaust gas load is constant or rising and also the desulfurization ratio is lower than a desired desulfurization ratio, the number of working pumps is correctively increased. According to another mode of embodiment of the invention, there are provided first and second simulation model, in the first simulation model a pH value of an absorbent liquid and a desulfurization ratio are calculated on the basis of an exhaust gas flow rate, an inlet SO.sub.2 concentration, an absorbent liquid circulation flow rate and a feed rate of a neutralizing agent of the absorbent liquid, these calculated values are compared with detected values of the pH value and the desulfurization ratio during operation, a reaction constant set within the first and second simulation model is corrected on the basis of deviations between the compared values, and said two optinum set values are calculated by the corrected second simulation model.