  This paper deals with the structural analysis problem of dynamic lumped
process high-index DAE models. We consider two methods for index reduction of
such models by differentiation: Pryce's method and the symbolic differential
elimination algorithm rifsimp. Discussion and comparison of these methods are
given via a class of fundamental process simulation examples. In particular,
the efficiency of the Pryce method is illustrated as a function of the number
of tanks in process design.
