A High Temperature Lithium Orthosilicate-Based Solid Absorbent for Post Combustion CO2 Capture

Abstract

Capture of carbon dioxide from combustion processes presents a unique and challenging technical problem arising from low CO2 partial pressures, high flow rates, and the presence of water vapor and reactive contaminants such as SO2. A series of solid sorbents were evaluated to determine suitability for postcombustion capture. A lithium orthosilicate (Li4SiO4)-based absorbent supplied by Toshiba Corporation was found to have the most promising properties. The absorbent reacts chemically with CO2 at elevated temperatures (550 °C) to form lithium carbonate (Li2CO3) and lithium metasilicate (Li2SiO3). The presence of water vapor was shown to greatly enhance CO2 absorption rates without affecting capacity. Breakthrough capacities of ∼5–6 mmol/g (22–26 wt %) were obtained using a “clean” synthetic flue gas containing 15% CO2 and 10% H2O in N2 at 550 °C. Experimental studies showed that the absorbent used in a fixed bed process will likely require a thermal swing process with absorption at 550 °C and regeneration...