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

“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).”

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