Modeling and control design of continuous stirred tank reactor system m saad a albagul d obiad department of control engineering faculty of electronic technology p o box 38645 baniwalid libya albagoulyahoocom abstract continuous stirred tank reactor system cstr is a typical chemical reactor system with complex nonlinear characteristics where an efficient control of the product . Continuous stirred tank reactors cstr are the most important and central equipment in many chemical and biochemical industries that exhibit second order complex nonlinear dynamics the nonlinear dynamics of cstr poses many design and control challenges. In this paper we deal with a novel digital controller design for a continuous stirred tank reactor where an irreversible exothermic liquid phase reaction evolves the controlled output is the reactor temperature the jacket temperature dynamics is considered. The ph control problem in a continuous stirred tank reactor is studied from both atheoretical and application point of view a reaction invariant model for an acid base system which is one of the most complete descriptions for the ph control problem is utilized