Performance evaluation and sensitivity analysis of polyethyleneimine-based sorbent in a circulating fluidized bed carbon dioxide capture unit

Greenhouse gases, particularly carbon dioxide, have increased the Earth's average temperature by 1 °C, which has resulted in significant consequences for human life. To prevent further global warming and maintain a stable lifespan, it is imperative to achieve carbon neutrality. Post-combustion capture using an amine-based aqueous solvent is an advanced technology that has gained attention, but there are challenges such as corrosion, environmental impact, and energy consumption associated with it. This study aims to evaluate the performance of a polyethyleneimine-based sorbent in a circulating fluidized bed carbon dioxide capture unit and to determine the optimal operating conditions through sensitivity analysis. Various variables, including carbon dioxide concentration, water vapor content, desorber temperature, and sorbent residence time, were analyzed. The unit was continuously operated for 128 h even under challenging conditions with higher oxygen concentrations than the actual flue gases, and sorbent degradation was negligible. The results showed a 55 % carbon dioxide removal efficiency, a dynamic sorption capacity of 0.041 g-CO₂/g-sorbent, and a regeneration heat energy of 4.2 GJ/tCO₂. Sensitivity analysis revealed that there was minimal improvement even with changes in the absorber structure and physical properties of the sorbent. Only an increase in the sorbent reaction rate had a significant effect. If the reaction rate were to double, the carbon dioxide removal efficiency would reach 90 %, with a dynamic sorption capacity of 0.068 g-CO₂/g-sorbent and regeneration heat energy of 2.9 GJ/tCO₂.