CaCO 3 is a promising material for thermochemical energy storage (TCES) systems. It can store and release heat upon reversible decarbonation to CaO, which emits heat through carbonation. Decarbonation temperature of CaCO 3 directly affects the properties of CaO, which influences heat supply in result. The current research studies CaCO 3 /CaO system, specifically analyzing the conversion of CaO into CaCO 3 (carbonation) for various CaO samples prepared at decarbonation temperatures between 600 and 975 °C. A relation is developed using regression analysis to verify the linearity between reactivity of CaO samples and decarbonation temperature at which it was prepared. The carbonation of all CaO samples at various partial pressures of CO 2 and temperatures is also analyzed. The whole process is performed for pure and SiO 2 doped systems (molar ratio 1:1). The efficient performance of CaCO 3 /CaO system is noted for decarbonation temperatures above 750 °C or below 925 °C for pure material. While for doped material, the decarbonation temperature for efficient performance lies between 700 °C and 800 °C. Both systems performed with higher efficiency when CO 2 pressure was kept constant and the carbonation temperature was increased.
Nano-sized calcium carbonate , as a multifunctional material, is widely used in various industrial fields. The morphology, particle size, surface property of CaCO 3 particles have great impact on the application effect. This study presents an energy-saving and efficient approach to controllably prepare CaCO 3 nanoparticles and conduct surface modification simultaneously. Ca(OH) 2 /CO 2 carbonation method was adopted to prepare CaCO 3 nanoparticles using a membrane dispersion microreactor in the presence of calcium stearate (CaSt 2 ) surfactant . The effects of gas and liquid flow rates , temperature and the dosage of surfactant were systematically investigated. The effect of surface modification was evaluated by contact angle and active ratio. The as-prepared hydrophobic CaCO 3 nanoparticles were of good dispersity, with an average particle size of 34 nm, a specific surface area of above 30 m 2 /g and a contact angle of 107.8°. In this work, the effect of surfactant on the carbonation reaction was greatly diminished by adding CaSt 2 surfactant to a portion of Ca(OH) 2 slurry. Additionally, the modification process was carried out without organic solvents and high temperature. As compared to post-modification method, the in-situ modification process is of significant practical importance because of high production efficiency, excellent process stability, and high product quality.
Kai Luo,Wensheng Zhang,Jiayuan Ye,Jun Li,Zhongyuan Lu,Xuehong Ren
The physical and microscopic properties of γ-C 2 S and β-C 2 S under hydration, carbonation , and hydration–carbonation cycle reactions were investigated. The hydration–carbonation cycle reaction facilitated the carbon sequestration of C 2 S, and the generation of CaCO 3 filled the pores of the matrix and enhanced the matrix density in the carbon fixation reaction process. In the subsequent hydration and reaction process, the formation of hydration products increased the number of pores in the matrix and reduced the matrix density. Post-hydration, γ-C 2 S slurry became powder and had no mechanical strength . However, after carbonation reaction and two carbonation–hydration cycles, γ-C 2 S exhibited better mechanical properties than β-C 2 S.
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