CaO carbonation kinetics determined using micro-fluidized bed thermogravimetric analysis

A micro-fluidized bed thermogravimetric analysis (MFB-TGA) method based on real-time mass measurement of solid sample inside a fluidized bed was developed. This technique was used to measure the fast reaction kinetics of CaO carbonation in calcium looping with similar characteristics of a strong mass and heat transfer in the
fluidized bed reactor. The effects of particle size, temperature, and CO2 concentration on the fast reaction kinetics of CaO carbonation were investigated. The experimental data measured upon MFB-TGA were interpreted with a K-L two-phase fluidized bed model to evaluate the effect of gas exchange between the bubble phase and the emulsion phase on the carbonation kinetics. We concluded that the kinetics of CaO carbonation measured by MFB-TGA were faster than those measured via regular TGA. The reaction rate constant (ks) was 8.0×10−10 m4/ (mol·s), the activation energy of the carbonation reaction was near zero, and the reaction was first order when the CO2 concentration was within 50 vol% (1 bar). This MFB-TGA method provides a new experimental idea and method for measuring gas–solid reaction kinetics occurring inside fluidized bed reactors.