_The control of pH is one of the most difficult challenges in the process industry because of the severe nonlinearities in the behaviour of the system. Different approaches for the pH control are proposed in various literatures. In the present study, control of pH using fuzzy model for internal model controller based PI is proposed. Modelling of the pH process is supposed to be a difficult task because one needs to have knowledge about the components and their nature in the process stream in

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... er to model its dynamics. In this work, fuzzy model is proposed using the first principle equation of the nonlinear pH process and used for controlling the pH process effectively using IMC based PI.