Micro-scale thermal imaging of CO_2 absorption in the thermochemical energy storage of Li metal oxides at high temperature

摘要

Li-Metal oxides (typical example: lithium ortho-silicate Li_4SiO_4) are regarded as a novel solid carbon dioxide CO_2 absorbent accompanied by an exothermic reaction. At temperatures above 700 °C the sorbent is regenerated with the release of the captured CO_2 in an endothermic reaction. As the reaction equilibrium of this reversible chemical reaction is controllable only by the partial pressure of CO_2, the system is regarded as a potential candidate for chemical heat storage at high temperatures. In this study, we applied our recent developed mobile type instrumentation of micro-scale infrared thermal imaging system to observe the heat of chemical reaction of Li_4SiO_4 and CO_2 at temperature higher than 600 °C or higher. In order to quantify the micro-scale heat transfer and heat exchange in the chemical reaction, the superimpose signal processing system is setup to determine the precise temperature. Under an ambient flow of carbon dioxide, a powder of Li_4SiO_4 with a diameter 50 micron started to shine caused by an exothermic chemical reaction heat above 600 °C. The phenomena was accelerated with increasing temperature up to 700 °C. At the same time, the reaction product lithium carbonate (Li_2CO_3) started to melt with endothermic phase change above 700 °C, and these thermal behaviors were captured by the method of thermal imaging. The direct measurement of multiple thermal phenomena at high temperatures is significant to promote an efficient design of chemical heat storage materials. This is the first observation of the exothermic heat of the reaction of Li4Si04 and CO2 at around 700 ° C by the thermal imaging method.