SYNTHESIS OF CALCIUM OXIDE FROM WASTE COCKLE SHELL FOR CO2 ADSORPTION

• Main Author: MOHAMED, MUSTAKIMAH BT MOHAMED
• Format: Thesis
• Language: English
• Published: 2011
• Online Access: http://utpedia.utp.edu.my/2806/1/MSc_Chemical_Engineering-Mustakimah_Mohamed.pdf; http://utpedia.utp.edu.my/2806/

Calcium oxide (CaO) is recognized as an effective carbon dioxide (CO2) adsorbent. It can be synthesized via calcination of calcium carbonate (CaCO3) sources including seashell. Malaysia is abundantly available with cockle shell and exploiting this resource as the potential alternative CO2 adsorbent is an advantage. Main objective of this research is to synthesis CaO by calcining waste cockle shells and demonstrate its capability to capture CO2 via carbonation reaction. The performance of calcination and carbonation reaction under various conditions such as particle sizes of sample, heating rate, calcination duration and temperature, are examined. Characterization analysis are conducted using x-ray fluorescence spectrometry (XRF), x-ray diffraction (XRD), energy dispersive x-ray spectrometry (EDX), scanning electron microscope (SEM) and physisorption analyzer while thermal stability, reactivity and kinetic analysis for calcination and carbonation of cockle shell are illustrated using thermal gravimetric analyzer (TGA). Material characterization indicates cockle shell is made up of aragonite and CaO can be synthesized at calcination temperature higher than 700°C and held for more than 20 minutes. Carbonation is maximized when CaO is synthesized at calcination temperature of 850°C for 40 minutes and heating rate is 20°C/min and using particle size of < 0.125 mm. At carbonation temperature of 600-650°C, 0.72kg of CO2 can be captured by 1kg of synthesized CaO. During palm kernel shell (PKS) steam gasification, CO2 released is 16% lesser once synthesized CaO is applied. Kinetics analysis shows that activation energy (Ea) to synthesis CaO from cockle shell is estimated to be 297.39kJ/mol and fit to zero order reaction where regression coefficient value is 0.999. Carbonation that been tested at 500-850°C shows that activation energy (Ea) at product layer diffusion control region is 102.5kJ/mol and chemical reaction control region is 72.7 kJ/mol. This study concludes that cockle shell is a good source to generate CaO adsorbent to capture CO2. At selected condition, synthesized CaO able to adsorb more CO2 and acquire lower activation energy compared to commercial CaO.