Optimal Control of Fixed-Bed Reactors with Catalyst Deactivation

• Author / Creator

  Mohammadi, Leily

• Catalytic reactors have widespread applications in chemical and petrochemical industries. The most well known type of catalytic reactors are fixed-bed or packed-bed reactors where the reaction takes place on the surface of the catalyst.
  One of the most important phenomena that takes place in a catalytic fixed-bed reactor is catalyst deactivation. Catalyst deactivation can have variety of consequences. It can have negative effects on the conversion and selectivity of the desired reaction. Consequently, it will affect the productivity and energy efficiency of the plant. It is therefore important to design efficient controllers that are able to track the optimal pre-defined trajectories of the operating conditions to ensure optimal operation of the plant.
  Depending on the transport and reaction phenomena occurring in a fixed-bed
  reactor, it can be modelled by a set of partial differential equations (PDEs) or a mixed set of PDEs and ordinary differential equations (ODEs). Moreover, the governing transport phenomenon (i.e. diffusion or convection) dictates the type of PDEs involved in the model of the reactor (i.e. parabolic or hyperbolic).
  In this work, infinite dimensional optimal control of a fixed-bed reactor with catalyst deactivation is studied. Since dynamical properties of hyperbolic PDEs and parabolic PDEs are completely different, they are discussed as different topics.
  The thesis begins with optimal control of a class of fixed bed reactors with catalyst deactivation modelled by time-varying hyperbolic equations. Then the model predictive control of this class of distributed parameter systems under parameter uncertainty is explored. The optimal control of reactors modelled by parabolic PDEs is first explored for the case of reactors without catalyst deactivation. Then the proposed controller is extended to a more general class of distributed parameter systems modelled by coupled parabolic PDE-ODE systems which can represent fixed-bed reactors with the rate of deactivation modelled by a set of ODEs.
  Numerical simulations are performed for formulated optimal controllers and their performance is studied.

• Subjects / Keywords

  • Optimal Control
  • Infinite-dimensional systems
  • Distributed parameter systems

• Graduation date

  Spring 2013

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R37069

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.