Effect of Temperature on the Carbonation Reaction of CaO with CO2

Abstract

It is well-known that carbonation is characterized by a rapid initial rate followed by an abrupt transition to a very slow reaction rate. The slow period is believed to be controlled by the diffusion of reacting species throughout the product layer of CaCO 3 . The thickness of the carbonate layer formed on the free surfaces of CaO is a critical parameter to mark the end of the fast reaction period. This study addresses the question of how temperature affects the reaction process. For example, when the carbonation reaction enters the product layer diffusion-controlled stage at a low temperature such as 500 °C, how does an increase to 600 °C affect the conversion as a function of time and what changes occur in the CaCO 3 product layer morphology? This work discusses the interesting finding that the fast reaction stage is recovered again when the temperature is increased. To understand and explain this phenomenon, it is necessary to investigate the mechanism of the temperature effect on the carbonation reaction. Many phenomena are not well explained by the theory of a critical product layer thickness, which is now used almost exclusively to explain the “maximum” conversion during carbonation reaction cycles. Therefore, we provide a new insight into this issue from a nanoscale point of view by combining thermogravimetric analysis (TGA) with the trapping mode (TM) of an atomic force microscope (AFM) to explain the mechanism of the reaction temperature’s effect on the reaction rate and solid conversion characteristics.