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The awareness of symptoms of global warming and its seriousness urges the development of technologies to reduce greenhouse gas emissions. Carbon dioxide (CO(2)) is a representative greenhouse gas, and numerous methods to capture and storage CO(2) have been considered. Recently, the technology to remove high-temperature CO(2) by sorption has received lots of attention. In this study, hydrotalcite, which has been known to have CO(2) sorption capability at high temperature, was impregnated with K(2)CO(3) to enhance CO(2) sorption uptake, and the mechanism of CO(2) sorption enhancement on K(2)CO(3)-promoted hydrotalcite was investigated. Thermogravimetric analysis was used to measure equilibrium CO(2) sorption uptake and to estimate CO(2) sorption kinetics. The analyses based on N(2) gas physisorption, X-ray diffractometry, Fourier transform infrared spectrometry, Raman spectrometry, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy were carried out to elucidate the characteristics of sorbents and the mechanism of enhanced CO(2) sorption. The equilibrium CO(2) sorption uptake on hydrotalcite could be increased up to 10 times by impregnation with K(2)CO(3), and there was an optimal amount of K(2)CO(3) for a maximum equilibrium CO(2) sorption uptake. In the K(2)CO(3)-promoted hydrotalcite, K(2)CO(3) was incorporated without changing the structure of hydrotalcite and it was thermally stabilized, resulting in the enhanced equilibrium CO(2) sorption uptake and fast CO(2) sorption kinetics.

The qualitative effect of temperature on the particle entrainment rate has been measured in a gas fluidized bed (0.1 m i.d., 1.97 m height). The gas velocity (0.65-2.3 m/s), the bed temperature (12-600 °C), the particle density (2509-6158 kg/m 3 ), and the particle size (0.091-0.363 mm) were considered as experimental variables. The particle entrainment rate increased after an initial decrease with increasing bed temperature. The effect of temperature on particle entrainment rate decreased as either the gas velocity or the particle density increased. Within the experimental range, it could be confirmed that the change of the particle entrainment rate with temperature was very similar to that of the particle size for which the terminal velocity was equal to the gas velocity.

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