화학공학소재연구정보센터
Energy & Fuels, Vol.33, No.6, 5505-5517, 2019
Kinetics Modeling, Development, and Comparison for the Reaction of Calcium Oxide with Steam
The hydration reaction between calcium oxide (CaO) and steam has applications as (i) a means to increase the reactivity of CaO-based sorbents for calcium-looping (CaL) CO2 capture processes and (ii) a process for thermochemical energy storage. However, the hydration kinetics of CaO have not been widely investigated in the literature, with previous investigations generally performed under diffusion-controlled conditions in a thermogravimetric analyzer. This work uses three particle models including (i) a developed form of the shrinking core model (D-SCM), (ii) the random pore model (RPM), and (iii) a developed form of the grain catalyst model (D-GCM) to evaluate the behavior of the reaction between CaO and steam in an atmospheric fluidized bed reactor under typical CaL conditions while minimizing diffusional resistances. The D-SCM was developed to account for particle expansion and changing bulk concentrations while the D-GCM was developed to improve its handling of changing steam concentrations. The suitability of each of the three models is assessed under kinetic-controlled conditions by varying particle size (200-710 mu m), steam concentration (10-20 mol %), particle calcination temperature (850-950 degrees C), and reaction temperature (300-400 degrees C). The D-SCM showed the greatest versatility and demonstrated greater accuracy over the SCM, providing a good fit for experimental data across all experimental conditions tested including data from literature. The RPM consistently bounded the data between a kinetics-controlled and diffusion-controlled prediction, and the D-GCM also showed greater accuracy over the GCM and produced consistent fits across steam concentrations at 300 degrees C but deteriorated at higher reaction temperatures. Further, a quantitative comparison of the modeling results was carried out by chi(2) goodness-of-fit (chi(2)-GOF) statistical testing.