Dynamic simulation of chemical processes described by distributed and lumped parameter models

Abstract

Currently available dynamic simulation routines are limited to processes in which the units can be described by lumped parameter models. In this paper, a general procedure is presented which permits the units to be described by both distributed and lumped parameter models. The partial differential equations resulting from a distributed parameter model are transformed into a set of ordinary differential equations by discretizing the spatial variable. The coupling of this set of discretized equations to the sets from other units is accomplished through the boundary conditions which represent the inlet and outlet of the unit. The resulting large set of time-dependent ordinary differential equations is solved simultaneously using a Gear-type integrator. The method is demonstrated by considering the start-up of a process composed of a tubular reactor, a gas absorption column and a completely mixed tank.