Investigation of Thermal Stability and Continuous CO2 Capture from Flue Gases with Supported Amine Sorbent

Abstract

Amine-functionalized material has gained attention as a promising solid sorbent for CO2 capture. To obtain a high concentration of CO2 for storage, the thermal regeneration temperature of supported amine sorbents should be higher than 135 °C under pure CO2. The thermal stability of solid amine sorbents will become a problem of significance. This study investigated the thermal stability of supported amine sorbents at 140 °C from the perspective of amine types and reactors, with a focus on how to improve the thermal stability of solid amine sorbents. Supported amine sorbents were prepared by impregnating polyethylenimine (PEI) and tetraethylenepentamine (TEPA) of different molecular weights on silica particles. The thermal stability of these amine-functionalized silica particles was investigated as a function of temperature and molecular weight in a thermogravimetric analyzer (TGA) and in a single-fluidized-bed reactor. An important finding was that the supported amine sorbents exhibited much higher thermal stabilities in a single-fluidized-bed reactor than in a TGA for long-term operation (100 h) at 140 °C, because the evaporation of the amines could be greatly inhibited in the fluidized-bed reactor because of the presence of amine vapor in the gas phase. Based on this finding, a simple and effective method of inhibiting amine evaporation was proposed and demonstrated. Furthermore, continuous CO2 capture was demonstrated using PEI-impregnated silica particles in a laboratory-scale dual-fluidized-bed reactor (DFBR). The CO2 capture efficiency was approximately 80% in the absorber during 2 h of operation, and the sorbent still maintained good stability and performance.