Influence of CO2 concentration on PEI–silica adsorbent based CO2 capture using fluidised bed reactor

https://doi.org/10.1016/j.cej.2014.04.063

“One of the most advantageous features of chemi-sorbents over physi-sorbents is that chemi-sorbents do not suffer from a significant reduction in CO₂ adsorption capacities at relatively low CO₂ partial pressures. A number of tests with the BFB reactor were conducted with different CO₂ concentrations in the simulated flue gas to investigate the impact of CO₂ partial pressure. With tests II24 to II26, the CO₂ concentration in the simulated coal-fired flue gas was decreased to 5% with O₂ concentration being kept at 4% and the capacities under this condition were compared with those of the nearest cycles II20 to II23 where 15% CO₂ was present in the simulated flue gas (Fig. 12). It was expected that adsorption capacities with 5% CO₂ in the feed gas were lower than those with 15% CO₂ in the feed gas due to lower reaction kinetics. However, as illustrated in Fig. 12, the equilibrium and breakthrough capacities remained reasonably high at ca. 10.1 wt% and 7.7 wt% respectively, representing a relative loss of only about 8%. In order to fully simulate the flue gas of Natural Gas Combined Cycle (NGCC) power plants, the O₂ concentration in the simulated flue gas was increased to 12 vol% by replacing part of the N₂ with air while keeping the CO₂ concentration at 5%. As shown in Fig. 13, changing the simulated flue gas from the conditions of a coal-fired power plant to those of a NGCC power plant caused the adsorption capacities to reduce by a relative loss of ca. 11%. Capacities observed with cycles II51-54 and cycles II58-60 indicate that the high oxygen level at 12% in the simulated flue gas (NGCC) did not cause appreciable oxidative degradation. ”

“Fig. 12. Comparison of capacities when different CO₂ concentration is present in the simulated flue gas (Batch II, initial bed temperature 50 °C, cycles ID: II20–II26, numbers in figure indicate the cycle ID number).”