Study of Decay Behavior of the CO2 Sorption by Limestones applied to the Carbon Sequestration Technology

Abstract

In the Lab of Thermal and Fluids Engineering (NETeF - EESC/USP) has developed a research program on pollution and combustion. The main goal of this program is contribute to the know-how development to minimize environmental impacts in the energy generation process. The Ca-looping process (Ca-L) is a promising technology to reduce of carbon dioxide (CO2) emissions when applied in energy generation systems. Ca-based materials (usually limestone) are used in this process as CO2 sorbents. Thus, the CO2 capture occurs by the reversible reaction between calcium oxide (CaO) and CO2, resulting in the calcium carbonate form (CaCO3). Compared to other technologies applied to carbon sequestration process, the Ca-L process offers additional advantages such: the use of fluidized bed technology that is already well established; this process occurs at high temperature, and the excess of heat generated can be recovered; the cost of limestone sorbents is low because of its wide availability. However, in the applying the Ca-L process is essential to understand the mechanism and the effect of partial pressure of CO2 in both, calcination and carbonation processes; to investigate the effect of sintering and to evaluate the sorbent activity decay. In this postdoctoral project, empirical techniques such as thermogravimetry and porosimetry are applied to investigate the reactivity of limestone sorbents and the effect of CO2 high concentrations in both calcination/carbonation processes. An isoconversional model (Model Free-Kinetics) will be applied to determine the activation energy of the limestone decomposition. In addition, the limestone pore structure developed under different experimental conditions will be correlated with the chemical composition of the sorbents used.