Influence of moisture and oxygen on PEI–silica adsorbent CO2 capture using fluidised bed reactor

“To investigate the effects of moisture on the performance of PEI–silica adsorbent, a moisture saturator is installed at the entrance of BFB to generate a stream of moisture that is introduced into the main simulated flue gas stream. The moisture saturator is operated at 40 °C and the volumetric concentration of the saturated moisture in the gas mixture is around 8.8% (wet basis). A stream of air is also introduced to the gas mixture, replacing part of the pure N2, generating oxygen concentration at 4% (dry basis) while keeping the total dry gas flow rate at 8 l/min (at 20 °C, 1.013 × 105 Pa). The final composition of the simulated flue gas mixture (CO2: 15% (dry basis), O2: 4% (dry basis), balanced by N2 with the addition of 8.8% (wet basis) moisture) represents a realistic flue gas stream from coal-fired power plants. The same amount of moisture is also present in the stripping N2 gas flow at the desorption stage.

Fig. 8 shows the results of capacities of subsequent cycles with addition of moisture and oxygen from cycle 39 to cycle 60 (the missing cycles between cycle 25 to cycle 38 were conducted for other research purposes under dry conditions and the results haven’t been included in this paper). It clearly indicates that the decreasing tendency of capacities shown in Fig. 7 has been completely avoided. The capacities were not impaired by the presence of moisture, and in the first several cycles with the presence of moisture in adsorption/desorption there was even a slight increase in capacity, probably due to the regeneration of the already degraded PEI–silica adsorbent by the aid of moisture during desorption. This finding agrees well with that obtained by Sayari and Belmabkhout [27] where the adsorption capacities stabilized over 40 cycles for three types of amine-containing adsorbents in the presence of moisture. The positive effect of moisture on the performance of PEI–silica adsorbent is utmost important as it indicates the long-term stability and low frequency of adsorbent replacement, thus making this adsorbent more competitive for commercial scale utilization.”


Fig. 8. Effect of moisture and oxygen in the simulated flue gas on capacities (Batch I, initial bed temperature 50 °C, cycles ID: I39–I60).”

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