CONTROL DEVICE FOR INJECTION OF ALKALINE AGENT FOR WATER PURIFYING PLANT

摘要

PURPOSE:To enable the control of pH of treated water to a target value with quick response by automatically correcting the error of the predicted pH after the injection of an alkaline agent to improve the accuracy of a feedforward control and combining said control with a feedback control. CONSTITUTION:The feedforward correction rate of the injection rate of the alkaline agent to obtain the target pH from the predicted pH at the point right after the chemical injection by a prediction calculator 11 and buffer capacity is calculated in a feedforward calculator 12. The feedback correction rate of the injection rate of the alkaline agent to obtain the target pH by feeding back the indicated value of a treated water pH meter 8 is calculated in a feedback calculator 15. The correction factor of the feedforward correction rate is calculated from the time series data of the predicted pH point at the point where the pH meter 8 is installed by the prediction calculator 11 and the indicated value of the pH meter 8 is calculated in an output correction calculator 13. The feedforward correction rate and the feedback correction rate are weighed and added in an adder 14.