Nonlinear computation in DIVA - methods and applications

Methods for one-parameter continuation and stability analysis of periodic solutions as well as two-parameter continuation of Hopf and limit bifurcation points have been added to the dynamic flowsheet simulation environment DIVA. They are specially tailored for large sparse systems of differential algebraic equations with arbitrary structural properties usually arising in dynamic flowsheet simulation of chemical processes and plants. The application of these methods combined with the other capabilities of such an integrated tool for nonlinear system analysis is demonstrated for two different types of processes. The first is the so-called circulation-loop reactor, which has been used for catalytic combustion of waste air. Through periodic operation of the reactor, abatement of small amounts of volatile organic compounds (VOCs) in waste air is possible autothermally or with minimum supply of energy. Control strategies are studied for extending the region of desired periodic operating points, when the amount of VOCs is too small for autonomous periodic operation. The second application is concerned with the nonlinear dynamic behaviour of reactive distillation processes for the production of fuel ethers MTBE and TAME. In particular, the existence of multiple steady states is analyzed for the practical important case, when pre-reaction is carried out prior to the reactive distillation column. Further, these results are compared with the case without pre-reaction and a physical interpretation is given. (C) 1999 Elsevier Science Ltd. All rights reserved.