Carbonation Behavior of fly ash with circulating fluidized bed combustion (CFBC)

Abstract

This paper investigates the reaction rates of CO2 that stores carbonation through comparing the carbonation behavior between Ca(OH)2 and fly ash with circulating fluidized bed combustion (CFBC) containing a large amount of free CaO. Because fly ash with CFBC contains abundant free CaO, it cannot be used as a raw material for concrete admixtures; hence, its usage is limited. Thus, it has been buried until now. In order to consider its reuse, we conduct carbonation reactions and investigate its rates. X-ray diffraction (XRD), thermogravimetric/differential thermal analysis (TG/DTA), and X-ray fluorescence (XRF) are conducted for the physical and chemical analyses of the raw materials. Furthermore, we use a PH meter and thermometer to verify the carbonization rates. We set the content of the fly ash of CFBC, Ca(OH)2, CO2 flow rate, and water to 100 ∼ 400 g, 30 ∼ 120 g, 700 cc/min, and 300 ∼ 1200 g, respectively, based on the content of the free CaO determined through the TG/DTA analyses. As a result, the carbonization rate of the fly ash with CFBC is the same as that of Ca(OH)2, and it tends to increase linearly. Based on these results, we investigate the carbonization behavior as a function of the free CaO content contained in the raw material.