A dynamic model first had to be developed which would form the basis for the internal model of the controller. The model was based on the familiar mass and energy balances about each effect. These were solved numerically using the range kutta 4 th order technique. Several other script files contain code for estimating physical properties (peacock,1995),calculating vessel parameters, and converting steam properties (Perry et st.,1997). The existing model makes the assumption of constant liquid volume hold –up for the firs two effects(without level control) while levels in the final three effects are modeled dynamically using the existing PID controller settings.