(229b) Kinetics Study of Calcium Carbonate Decomposition At High CO2 Environment

With the concerns of “global warming”, CO2 sequestration from cement industry are becoming significant important for the “green processing” for the environments. This is because the cement processing released about 36% of CO2 comparing to the 12% from regular coal-power plant.  CaO/CaCO3, a major component and raw material from cement, was investigated in order to design suitable processing to sequestrate the CO2 during the cement production.  It was found that the raw material particle size, surface area as well as chemical components were important factors, which will effect on the CO2 absorption efficiency, cycle times, particle activities, and so on.  Various analytical equipments such as SEM, XRD, FTIR, TGA, were used to monitor the processing and analysis materials during the processing. 

It was found that there are two competitive mechanisms involved during the processing i.e., chemical reaction and physical diffusion.  In order to investigate the dominated effect, we selected the different particles as model compounds for the analysis.  As a result, we found the small particle (particle size less than 5 micron) is dominated by chemical reaction mechanism, i.e., CO2 can completely diffusion into the core of the particle and result in a complete chemical reaction to form CaCO3; and the larger particle is dominated by the physical diffusion mechanism, i.e., only partial CO2 can diffuse into the CaO particles and formed a “core-shell” particles, where the centre core is CaO and out-shell is CaCO3.  In addition, the small particle always accomplished with a high cycle times and more complete chemical reaction, which was recommended to use in the industry.

Based on the cement processing, various chemical looping processes were used to demonstrate the CaCO3 Calcinations / CaO Carbonation Cycle such as, vacuum processing, solids flow processing, fluidization processing, and cocking gas recycling processing.  The energy efficiency, raw material activities, and corresponding thermodynamic date will be presented during the presentation.