Conceptual Design for Integrating Lithium-Based Carbon Capture Looping Systems into Natural Gas Combined Cycle Power Plants

Lithium orthosilicate (Li₄SiO₄) based sorbents have been reported to show relatively high CO₂ capture capacity and high stability and require lower regeneration temperatures than other high-temperature sorbents. Based on these properties, a capture plant concept could be envisaged, aiming for achieving as low as possible CO₂ capture penalties. Accordingly, this work presents a conceptual AspenPlus process simulation study that evaluates the thermal integration of Li₄SiO₄-based looping systems into a natural gas combined cycle (NGCC) power plant with the addition of a secondary oxyfuel combustion system and a secondary steam cycle. Based on previously obtained experiment results, absorption and desorption temperatures of 525 and 700 °C, respectively, a sorbent fractional conversion of 0.2 in the absorber, and a sorbent make up ratio of 0.01 were used in the model. The results show that implementation of a Li₄SiO₄-based high-temperature carbon capture (HTCC) system into a NGCC power plant reduces the plant efficiency by 9.2% penalty points. This energy penalty is close to the one obtained from the integration of first-generation amine-based capture technologies, 8.4% penalty points, and lower than that for CaO-based HTCC plants (12.5% points), which were evaluated under the same assumptions as those used in this work. A sensitivity analysis on the impact of varying different process parameters on plant efficiency and integration penalties has been performed. Sorbent regeneration temperature was observed to be the most affecting parameter. However, it was found to be constrained by upper and lower limits. In line with the current findings, using improved Li₄SiO₄ sorbents could lead to further reduction in CO₂ capture penalties. ©