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Rezensionsexemplar
Dezember 2012
Volker Michael Zahn
Adiabatic Simulated Moving Bed Reactor
Principle, Nonlinear Analysis and Experimental Demonstration
This work investigates a heat integrated reactor concept based on unsteady state operation
of several adiabatic catalytic fixed-bed reactors. Exothermic reaction fronts are guided
through such a cascade in the gas flow direction, while cold reactor segments are switched
to the end for efficient thermal regeneration. This inherently periodic operation attempts
to trap a self-sustained exothermic front allowing an autothermal operation. As such, the
switching policy simulates a countercurrent of the solid compared to the fluid phase and is
therefore denoted as a simulated moving bed reactor (SMBR). Potential applications are seen
in catalytic total oxidation of volatile organic compounds (VOC) in diluted off-gases or in
performing equilibrium limited exothermic reactions. This work contains a comprehensive theoretical analysis and an experimental proof-of-concept of the adiabatic simulated moving
bed reactor.
In order to avoid expensive dynamic simulations, a true moving bed reactor model was
derived, which retains all relevant properties of the periodic reactor needed for reactor
analysis and design. This does not only allow a direct approximation of temperature and
concentration profiles, but provides an efficient numerical nonlinear analysis essential to
understand and control ignition-extinction phenomena. Diverse reactor multiple steady
states were encountered and structured with the help of higher order singularities. In this way,
reactor control and the identification of feasible reactions are available. Three discrete-time
control concepts were investigated to maintain the reactor in the limited range of switching
times. Already a simple temperature control was shown to be appropriate.
The model-system experimentally investigated is the total oxidation of propene and ethene on a CuCrOx/Al2O3 catalyst in air. Systematic experiments confirmed the applicable range of switching times as well as the control characteristic. Step experiments altering flow rates and concentrations demonstrated the proper disturbance rejection.
As long as rates of the oxidation reactions are similar, mixtures can be well processed. Otherwise, incomplete conversion of the less oxidizable component can occur. Due to sufficiently high start-up temperatures and an excess of this component the total oxidation of such mixtures can be assured.
The model-system experimentally investigated is the total oxidation of propene and ethene on a CuCrOx/Al2O3 catalyst in air. Systematic experiments confirmed the applicable range of switching times as well as the control characteristic. Step experiments altering flow rates and concentrations demonstrated the proper disturbance rejection.
As long as rates of the oxidation reactions are similar, mixtures can be well processed. Otherwise, incomplete conversion of the less oxidizable component can occur. Due to sufficiently high start-up temperatures and an excess of this component the total oxidation of such mixtures can be assured.
Schlagwörter: simulated moving bed; unsteady reactor operation; heat integration
Forschungsberichte aus dem Max-Planck-Institut für Dynamik komplexer technischer Systeme
Herausgegeben von Prof. Dr. Peter Benner, Prof. Dr.-Ing. Udo Reichl, Prof. Dr.-Ing. Andreas Seidel-Morgenstern und Prof. Dr.-Ing. Kai Sundmacher, Magdeburg
Band 37
Shaker Verlag GmbH
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