Case Study of an Automatic pH Control Strategy for a Strong Acid-Strong Base System

The control of pH has been studied extensively for its distinct, nonlinear, and unstable character as well as its wide application in the process industries. Of particular importance is the strong acid-strong base system for its steep titration curve and difficulty in reaching steady state. In this study, the development and design of a simple yet robust single-tank industrial neutralization process is presented. The technical keys are the proper choice of holdup volume, the understanding of pH sensor time lag and maintenance procedures for them, the proper tank mixing design, the choice of set point, and the incorporation of the difference between the actual and indicated pH.