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 inherently an unsteady state process and therefore the modelling of such columns is dynamic in nature. This generates a set of differential-algebraic equations (DAE) which is very stiff. In this work, the numerical integration of the system of differential equations is made by using Euler method, Runge-Kutta 4 th. order with variable step method and the semi-implicit method of Villadsen and Michelsen. All of them are compared using different degrees of stiffness. This result is very important to be used in on-line control purposes.