(315b) An Analysis of the Nonlinear Behavior of the Autothermal Reactor

The autothermal reactor presented by [1] shows the multiplicity of the equilibrium profiles for an axial nonisothermal tubular reactor described by Arrhenius type nonlinear models. The unusual behavior is not expected for a tubular reactor with no diffusion effects and linear kinetics. This behavior is similar to the exothermic continuous stirred tank reactor model [2], which shows multiple steady states, stable or unstable, and in practical applications, the unstable steady states may correspond to the operating points of interest. The present work proposes an extended study on the non-linear behavior of the autothermal reactor. Different types of configurations for the reactor (for instance, co-current flow heating jacket and no temperature dependence of the kinetic constant) are studied to compare with the original system.
In [3], an analysis of a simplified tubular reactor with diffusion and temperature dependence kinetics was able to show the conditions necessary for the existence of multiple equilibrium profiles. In this work, a similar analysis is made on a simplified autothermal reactor to find the conditions necessary for the multiplicity of steady-states.
To demonstrate the nonlinear behavior of the full original autothermal model, a numerical analysis is performed to investigate how the system behaves as the model parameters are changed. Different discretization techniques are used to show the influence on the nonlinear behavior obtained.

[1] Bonvin, D., Rinker, R.G., Mellichamp, D.A. (1980). Dynamic analysis and control of a tubular autothermal reactor at an unstable state. Chemical Engineering Science, 35 (3), 603-612.

[2] Vejtasa, S.A., Schmitz, R.A. (1970). An Experimental Study of Steady State Multiplicity and Stability in an Adiabatic Reactor. AIChE Journal, 16(3), 416-419.

[3] Dochain, Dennis., (2016). Analysis of the multiplicity of equilibrium profiles in tubular reactor models. IFAC-PapersOnLine 49-18, 903-908.