A Hybrid Intelligent Control Model for Regulating pH In Industrial Chemical Process

Abstract

This paper present a hybrid intelligent control model for pH regulation in industrial chemical process. A Chemical Plant containing a continuous stirred tank reactor (CSTR) for water treatment was model for compensating the performance of a pH regulation in the process plant. pH is the measure of the degree of acidity or basicity  of an aqueous solution, the pH values ranges from 0-14, with 7 being neural, pHs less than 7 indicate acidic and greater 7 basic. Regulating  pH in neutral region is an essential process due to the fact that small variation of input may results to large variation of the output. A pH neutralization process for water treatment was modeled based on the reaction of strong acid and strong base of one molarity in CSTR. The dynamics transfer function of pH system was developed as first order plus delay time (FOPDT) process. A proportional integral and derivative (PID) compensator model was initially designed using PID Tuner in MATLAB. Thereafter, a Fuzzy Logic system employing linguistic variables was designed using Fuzzy Inference System (FIS) in the MATLAB software tool.  The gains of the PID algorithm were combined with the Fuzzy Logic system to produce the proposed hybrid intelligent Model called Fuzzy-PID. The Model was incorporated into the loop of pH regulating process whose values range from 0-14 in the pH scale. The process analysis was modeled in MATLAB/Simulink environment to examine the effectiveness of the hybrid system.  The application was developed using JAVA, and Netbean IDE 8.0.1. The work adopted Object Oriented Methodology in the development of the application. Simulation was initially conducted considering loop response of pH system in terms of step input without the addition of the proposed intelligent hybrid model. In order to validate the effectiveness of the proposed system, simulations were conducted in acid, neutral and base media with pH setpoint target of 5, 7 and 9 respectively on settling time, rising and overshoot as well the error performance analysis with Integral Absolute Error (IAE), Integral Square Error (ISE) and Integral Time Absolute Error (ITAE). It was observed that the ITAE produces less error performance on the hybrid model (FPID) with 36.53 and PID 42.75. The results obtained may show that the proposed hybrid system was able to maintain the setpoint pH values in the various media than individual model.