Impact of delay on robust stable optimization of a CSTR with recycle stream*

We demonstrate that the normal vector method for robust optimization of nonlinear systems with uncertain parameters can be extended to systems with delays. A first-order exothermic irreversible reaction carried out in a CSTR with recycle stream serves as example for the broad class of nonlinear delay differential equations (DDE) with uncertain parameters. The stability boundaries that must be taken into account in the robust optimization consist of Hopf bifurcation points in this case. We show that (i) an unstable steady state of operation results if stability boundaries are neglected and (ii) a conservative optimal steady state results if the delay is ignored.