EVALUATION ON NUMERICAL-METHODS FOR RESOLUTION OF STIFF SYSTEMS

Batch distillation process is characterized as being highly flexible, handling a wide range of different mixtures, feed compositions, number of components, changes in product demands and availability of shared storage. Unlike continuous distillation, batch distillation is inheren tly an unsteady state process and therefore the modelling of such colu mns is dynamic in nature. This generates a set of differential-algebra ic equations (DAE) which is very stiff. In this work, the numerical in tegration of the system of differential equations is made by using Eul er method, Runge-Kutta 4 th. order with variable step method and the s emi-implicit method of Villadsen and Michelsen. All of them are compar ed using different degrees of stiffness. This result is very important to be used in on-line control purposes.