The capture of CO2 by particles of calcined dolomite in a gas-fluidized bed was investigated experimentally in a laboratory-scale reactor. Step-response experiments were performed to determine CaO conversion rates in the bed as a function of time and dolomite particle diameter. It was found that the CO2 capture dynamics in the fluidized bed itself could be extracted from the overall system response curves by making use of a blank testperformed under identical flow and temperature profile conditions but with no calcined dolomite present. A simple flow-with-reaction model of the process was proposed; it provided a good description of the transient behaviour in terms of an empirical transfer coefficient, which was found to depend linearly on dolomite particle diameter. A shrinking core model was then developed and applied, to evaluate the individual effect of chemical kinetics and pore diffusion on the global reaction rate. The chemical process was found to control the smallest particle size carbonation test, in very good agreement with the kinetic constant value proposed in literature (Bhatia and Perlmutter, 1983), whereas the diffusion coefficient, needed to describe CO2 uptake as particle grows, appeared to be a function of sorbent size: this points to the need of more sophisticated SRD (simultaneous reaction and diffusion) models to describe the real behaviour of systems at hand.
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