Performance of different H2O sorbents for fluidized bed sorption-enhanced methanation

In this work a CaO, derived from natural limestone, and two commercial zeolites (3A and 4A) were tested as sorbent materials for H2O capture in a new configuration for the sorption-enhanced methanation, based on the concept of chemical looping in dual interconnected fluidized bed systems. The experimental campaign was aimed at studying the sorbent performance in terms of hydration and dehydration cycles at different operating conditions relevant for catalytic methanation. The results showed that CaO has a good capacity to capture and release steam in the temperature range of interest. Unfortunately, even at the lowest temperatures tested, the sorbent was affected by the presence of CO2, which worsened its performance in terms of H2O capture capacity. The zeolites had a more stable behavior than CaO with the number of cycles under all investigated conditions. Comparing the performance of the three materials, the zeolites on average had better asymptotic capture capacity than CaO, and were not affected by deactivation during the cycles.