화학공학소재연구정보센터
Industrial & Engineering Chemistry Research, Vol.51, No.27, 9320-9327, 2012
A High Temperature Lithium Orthosilicate-Based Solid Absorbent for Post Combustion CO2 Capture
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 degrees 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 similar to 5-6 mmol/g (22-26 wt %) were obtained using a "clean" synthetic flue gas containing 15% CO2 and 10% H2O in N-2 at 550 degrees C. Experimental studies showed that the absorbent used in a fixed bed process will likely require a thermal swing process with absorption at 550 degrees C and regeneration at 650 degrees C. Even for the high capacity of the Li4SiO4-based absorbent, an alternative to conventional fixed bed technology will be required for practical postcombustion capture from coal-fired power plants. Processes that can shorten cycle times by rapidly heating and cooling vessels and/or sorbents will be needed, and possible alternatives are described.