Neutralization process control using an adaptive fuzzy controller

Controlling of neutralization processes is a classical problem beyond many common control techniques available today due to their strong nonlinearity and extreme sensitivity to disturbances. This paper proposes an adaptive fuzzy control scheme for wastewater neutralization process control. A standard Mamdani type fuzzy system is constructed to describe the nonlinearity of the process and the parameters in the fuzzy system are tuned online using the least square algorithm with deadzone. The controller is designed based on the fuzzy model and the control action is computed by exploiting the special features of the fuzzy system. Simulation results are given in control of the acidity in the continuous flow of an industrial wastewater treatment system.

I. Introduction

Neutralization is a common and important operation in chemical plants, such as biological, wastewater treatment, electrochemistry and precipitation systems. The purpose of neutralization is to adjust the pH value to neutrality for a certain requirement, for example, to minimize the environmental impact in wastewater treatment systems. In the literature, different approaches to control of neutralization processes have been applied, such as modified PI, linear adaptive, model-based, nonlinear adaptive, and predictive adaptive controllers (see [3], [4],. [7] and the references therein). Despite various techniques devoted to improve those classical methods, the performance of neutralization control is not yet adequate due to the inherent nonlinearity of the titration curve and high sensibility to small perturbations near the equivalence Point.