Stability and multiplicity approach to the design of heat-integrated PFR

Abstract

The nonlinear behavior of the heat-integrated plug-flow reactor, consisting of a feed-effluent heat exchanger (FEHE), furnace, adiabatic tubular reactor, and steam generator is studied, considering a first-order, irreversible, exothermic, adiabatic reaction. Bifurcation theory is used to analyze the relationships among design, reaction thermodynamics and kinetics, and state multiplicity and stability. Hysteresis, isola and boundary-limit varieties are computed, and the influence of the activation energy, reaction heat and FEHE efficiency on the multiplicity region is studied. The double-Hopf and double-zero bifurcation points divide parameter space in regions with different dynamic behavior. State multiplicity, isolated branches, and oscillatory behavior may occur for realistic values of model parameters. A design procedure is proposed to ensure a desired multiplicity pattern and a stable point of operation and to avoid high sensitivity. The procedure was applied to three reaction systems with different kinetic and thermodynamic characteristics.