Study of limestone thermal decomposition in O2/CO2 atmosphere

Abstract

Oxygen-enriched fluidized bed combustion is a new technology which can realize CO2 zero emission, enhance the combustion efficiency and reduce pollutants emission. Due to the high concentration of CO2, the technology has many different aspects in limestone thermal decomposition and calcium-based desulfurization compared with conventional combustion. In this article, experiments have been done to investigate the behavior and mechanism of limestone thermal decomposition by a thermogravimetric analyser (TGA). It was observed that the limestone specialities of physical properties, pore structure, impurities categories and content have an important influence on the decomposition properties. The present of CO2 increase the imestone decomposition temperature, and shorten the time length of complete decomposition; especially in low CO2 concentration atmosphere. When the CO2 concentration was above 40%, the most probable decomposition mechanism transformed from nuclear producing and growing process (G(α)=[-ln (1-α)]3/2) to fast chemical reaction process (G(α)=(1-α)-1-1), and the value of E increase linearly with rise in the CO2 concentration. A rise in heating rate increase the limestone decomposition temperature beacause of the hysteresis effects of heat transfer, and the effect become more severe with the heating rate increasing. The small limestone paiticle is easier to decompose completely by the fine heat transfer property in interior of the paiticle. In the decomposition process, two countering effects of calcination and sintering must be considered in the practical application. © Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2012.