Calcination of Precipitated Calcium Carbonate with Surfactant-assisted Agglomeration -A Non-isothermal Topochemical Approach

It has been shown that precipitated calcium carbonate prepared by surfactant-assisted agglomeration (PCC-SAA) provided higher capacity for the carbon dioxide capture during calcination carbonation cycling as compared to commercially available calcium carbonate. It was also shown previously that the capacity was maintained over multiple cycles while commercially available calcium carbonate significantly lost its capacity. In order to understand the differences in the calcination behaviour of the PCC-SAA sample as compared to the commercially available laboratory-grade calcium carbonate (AC) sample, a nonisothermal topochemical approach was adopted to delineate the various controlling mechanisms for calcination of CaCO3. Activation energies were calculated using iso-conversional methods such as Friedman’s method, the KSA method, and the FWO method. In addition, the mechanism was identified at different heating rates by applying the Malek’s method and evaluated in some cases using the JMA kinetics. Finally, four mechanisms were used to calculate the pre-exponential (frequency factor). Some key differences such as the initiation temperature, and mechanisms were found between the two samples. Generally, it was found that the differences in the two samples were primarily due to the structural causes. It was observed that the initiation temperature for CaCO3 decomposition, activation energies and mechanisms were a function of the heating rates. D2 or D4 was identified as the controlling mechanisms at lower temperatures for the PCC-SAA sample in contrast to JMA (n > 1) kinetics for the higher heating rates. For the AC sample, 3D diffusion process appears to control the calcination of the AC sample.