Kinetic Expression for the Carbonation Reaction of K2CO3/ZrO2 Sorbent for CO2 Capture

For the kinetic study of K2CO3/ZrO2 sorbent in the carbonation reaction to capture CO2 from the flue gas, reaction experiments were carried out at temperatures between 328 and 343 K for CO2 gas compositions not exceeding 18% at 1 bar, and a phenomenological kinetic model was proposed to fit the carbonation conversion data obtained. Time dependent carbonation conversions of the sorbent appeared as sigmoid curves. Sigmoid characteristics of the conversion curve were more pronounced for the sorption reaction at lower temperature and lower gas phase concentration of CO2. Such conversion behavior of fresh-dried K2CO3/ZrO2 sorbent could be closely described with the reaction rate equation in the form: r = kf(X)(yCO2)(n). The reaction rate constant k as a temperature dependent term could be represented by Arrhenius' equation with the negative apparent activation energy of -17.43 kJ/mol and the pre exponential factor of 3.83 x 10(-3) 1/min. The term f(X) was a function introduced to reflect the carbonation rate change with the fractional carbonation conversion X of the sorbent, and its parameters were determined by correlation equations of the reaction temperature and the gas phase concentration of CO2. The reaction order n with respect to y(CO2), the gas phase mole fraction of CO2, was determined to be 0.49. And, the characteristics of K2CO3/ZrO2 sorbent in the carbonation reaction for CO2 capture was discussed in relation to the kinetics obtained.