Application of Aspen Plus fluidized bed reactor model for chemical Looping of synthesis gas

Abstract

Chemical Looping Combustion technologies are a recent innovation with a natural ability to capture carbon dioxide. In these processes, two interconnected fluidized bed reactors are employed to achieve oxidation and reduction reactions separately. In the current study, an Aspen Plus simulation uses the specialized Fluidized Bed Reactor block to model a Fuel Reactor in which carbon monoxide and hydrogen react with hematite. This reactor block includes a hydrodynamic model that describes the solid volume fraction, particle size distribution and solids entrainment effects, and a reactor model that employs reaction kinetics for the gas–solid reactions. A comparison is performed with an established Stoichiometric Reactor approach for validation purposes, and results agree closely. Several sensitivity studies are carried out to explore the impacts of process variables on carbon dioxide generation and selected hydrodynamic parameters. For the range of conditions simulated, these studies revealed that solid volume fraction decreases with the height of the bed and with increasing superficial velocity. It is also observed that the height to diameter ratio of the fluidized bed is a key variable in sizing the reactor. Based on an analysis performed on two distributor configurations, a bubble cap is the best option to provide a smaller pressure drop. The results presented in the current work also suggest that the application of the Fluidized Bed Reactor model in Aspen Plus provides additional design insights and is a valuable alternative to the commonly used Stoichiometric Reactor approach.