Coupling exothermic and endothermic reactions in plug-flow reactor-separation-recycle systems

The nonlinear behavior of plug-flow reactor-separation-recycle systems, where the endothermic first-order reaction A -> R + Q and the exothermic second-order reaction B + Q -> P simultaneously take place, is investigated. As the physical properties of the species involved vary, possible flowsheets are identified and feasible control strategies are suggested. Bifurcation analysis of the reactor-separation-recycle system is performed by choosing set-point variables as bifurcation parameters. Steady state multiplicity is invariably detected leading to complex behavior. Implications on plantwide control are thoroughly discussed and guidelines are provided which enable to select values of set-point variables in a way that guarantees safe operation.