| 摘要 |
<p>PURPOSE:To reduce the consumption amount of limestone, electric power and sulfuric acid, by controlling the charging amount of a limestone slurry on the basis of a pH-value while controlling the recirculation amount of the limestone slurry corresponding to a desulfurization ratio. CONSTITUTION:The pH set value corresponding to the SO2-amount in exhaust gas is calculated by a function generator 24 and, after side pH set value is corrected by an optimum pH correction value signal 22, the deviation with an actually measured pH value is operated by a subtractor 26 to be inputted to a function generator 27. This corrected value is added to the set value of the limestone excessive ratio corresponding to the amount of SO2 from a function generator 28 and the signal corresponding to the change speed of the absolute value of SO2 from a gain setting device by an adder 31 to obtain an objective limestone slurry flow amount signal. The opening degree of a flow control valve 3 is controlled on the base of the deviation of this flow amount signal and an actual slurry flow amount. An actual desulfurization ratio eta is calculated from the signal 15 of SO2-concn. in exhaust gas and an outlet SO2 concn. signal 35 and, from the deviation with a required desulfurization ratio eta0, the objective value of a limestone slurry recirculation flow amount is calculated and the operation of a slurry recirculation pump is controlled corresponding to the deviation with an actual slurry recirculation flow amount by a controller 46.</p> |
