Kenji Essaki

Novel CO2 Absorbents Using Lithium-Containing Oxides

Publisher Summary Lithium-containing oxides have been developed for application as a series of novel CO 2 absorbents. The absorption is ascribed to the mechanism whereby lithium oxide in the crystal structure reacts reversibly with CO 2 . Among these absorbents, lithium orthosilicate (Li 4 SiO 4 ) reacts with CO 2 at higher reaction rate at around 500°C. Furthermore, the emission was performed at a much lower temperature than that of CaO. This temperature enables Li 4 SiO 4 to be used repeatedly in pure CO 2 . Moreover, the absorption also proceeds at ambient temperature in an atmospheric environment. This characteristic suggests numerous possible applications such as air cleaners or cartridges. In this study, CO 2 absorption properties of lithium orthosilicate and its contemplated applications were investigated. From the viewpoint of preventing global warming, there is a growing need to reduce the amount of emission of carbon dioxide (CO 2 ). For that purpose, saving of energy, improvement of conversion efficiency, and development of alternative energy sources and separation of CO 2 are promising countermeasures. Regarding separation of CO 2 , it is thought to be effective to remove CO 2 from the high-temperature fuel gas of power plants. However, most CO 2 removal techniques have poor heat-tolerance. The authors have developed a novel CO 2 separation technique by employing the chemical reaction of lithium zirconate (Li 2 ZrO 3 ) with CO 2 . The application to power plants is expected to be the most effective for combating global warming. To achieve continuous absorption, a system in which several reactors are changed sequentially constitutes a basic approach.

Performance Prediction of High-Temperature CO2 Capture System Utilizing Lithium Silicate for Pulverized Coal-Fired Power Plant

Lithium silicate is a solid CO2 -sorbent that can be used repeatedly, and uniquely features absorption of CO2 at temperatures between 500°C and 600°C with an exothermic reaction and regeneration at temperatures above 700°C with an endothermic reaction. This paper introduces the conceptual model and feasibility study of the CO2 capture system utilizing the lithium silicate applicable to a pulverized coal-fired power plant. In this system, assuming a moving bed, the sorbent reactor is installed in a 500MW boiler and absorbs CO2 in the flue gas, and after the absorption process, recirculation of CO2 transports the heat for regeneration. To design the system, unsteady state numerical analysis was used to predict the reactor performance in a 60-minute cycle for absorption and regeneration, which includes the reaction rate based on experimental data. The analysis result indicates that about 20% of CO2 can be captured from flue gas without significant loss in the power generation efficiency.Copyright