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Dissolution Reactivity and Kinetics of Low-Grade Limestone for Wet Flue Gas Desulfurization

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journal contribution
posted on 29.07.2020, 20:29 by Shuaiwei Gu, Zhizhong Yang, Zhen Chen, Changfu You
Low-grade limestone with relatively low calcium (Ca) content is an alternative to high-grade limestone for wet flue gas desulfurization (WFGD). This paper presents an experimental study on the dissolution reactivity and kinetics of low-grade limestone under similar conditions which may be encountered in the WFGD process. Four limestone samples with calcium oxide (CaO) content ranging from 34.89 to 62.66 wt % are selected from different sources in China. The effects of experimental variables including the chemical compositions, slurry pH, initial particle size, and reaction temperature on various grades of limestone are investigated, respectively. Results show that dissolution rates of low-grade limestone are significantly inhibited in the presence of dolomite and diopside, which is the main form of Mg contained in low-grade limestone. The particle size has a smaller effect on dissolution reactivity for low-grade limestone compared with high-grade limestone, whereas reaction temperature and pH value have more significant effects. A kinetics analysis shows that lower grade limestone dissolution happens per the shrinking core model with an ash diffusion control and the apparent activation energy for the reaction increases as the limestone grade decreases.