Design and Operation of a Fluidized Bed Hydrator for Steam Reactivation of Calcium Sorbent

The decreasing CO2 capture capacity of calcium sorbents over multiple reaction cycles poses a significant challenge to the large-scale cyclic carbonation-calcination process. Several approaches, including intermediate hydration, have been suggested to overcome this limitation. Until this study, most hydration studies have been performed at laboratory-scale using thermogravimetric techniques at conditions that may not be feasible for process scale-up. Moreover, data on the design of a steam hydrator suitable for the calcium looping process is not available. For the first time, this study reports the design of a bench-scale high-temperature steam hydrator for calcium sorbent reactivation. The hydrator, consisting of a fluidized-bed reactor with additional internals, was evaluated using cold-flow tests following which several reaction parameters were investigated in the hot unit. The results obtained from these high-temperature steam hydration tests (300-500 degrees C) are discussed here. Specifically, at an average temperature of 473 degrees C and P-H2O = 1 atm, the 30 min hydration conversion exceeded 70%. In addition, the sorbent reactivity toward CO2 was appreciably recovered proportional to the extent of hydration. Lastly, the potential to extract the heat of reaction (>450 degrees C) for process heat integration further expands the marketability of this high-temperature steam hydrator as a viable option for a wide range of applications ranging from CO2 capture to chemical heat pump systems.