Tailored catalyst pellet specification for improved fixed-bed transport characteristics: A shortcut method for the model-based reactor design

摘要

To improve the transport characteristics of a catalytic fixed-bed via optimal design of catalyst pellet specifications such as the pellet diameter it is necessary to account for all physicochemical phenomena influenced by the pellet. For the approximative description of the transport phenomena on the catalyst pellet scale a new shortcut method is developed in this work. It enables a generalized and system independent treatment of the aforementioned processes and can be applied to arbitrary reaction networks and reaction kinetic models. Based on linearization and decoupling of the pellet balance equations the method yields an analytical solution. This allows for model-based design of the reactor-catalyst system via dynamic optimization at reduced computational costs as the use of complex heterogeneous models is avoided. In order to ensure accurate predictions of the method, regions with high catalyst utilization are targeted.To indicate the potential of improved bed transport characteristics, the shortcut method is applied to the reactor-catalyst system for ethylene oxide synthesis. The system is optimized in terms of reducing the pressure drop while meeting other reactor performance constraints. The pressure drop could be reduced by more than 60%. The shortcut method is validated using a rigorous stand-alone model of the catalyst pellet.