Influence of Hydration by Steam/Superheating on the CO₂ Capture Performance and Physical Properties of CaO-Based Particles

Abstract

This paper studied the effect of the cyclic carbonation/calcination reactions and the hydration-based reactivation methods (i.e., hydration by steam and hydration by superheating) on the CO 2 capture performance and physical properties of pelletized CaO-based sorbent particles in a fixed bed reactor. Hydration by superheating consisted of first a steam hydration process in 15 vol % H 2 O at 300 °C and a subsequent superheating process in 100% CO 2 at 550 °C. It was found that during the successive carbonation/calcination cycles, the chemical activity of CaO sorbent particles fell rapidly while their physical properties (i.e., weight loss after rotations and compressive strength) were largely maintained. In addition, both hydration by steam and hydration by superheating were effective in reactivating the chemical activity of CaO-based pellets to nearly the same level. Hydration by steam, however, significantly weakened the physical strength of CaO-based pellets whereas hydration by superheating largely maintained their mechanical properties over 20 cycles. The positive effect of hydration by superheating was ascribed to the carbonation of Ca(OH) 2 during the superheating step at 550 °C.

In situ synchrotron XRD investigation of the dehydration and high temperature carbonation of Ca(OH)2

“…9,11,13 Second, the absence of an observable CaO phase during the formation of CaCO 3 (80-180 min) strongly suggests that carbonation of CaIJOH) 2 is taking place via a direct Fig. First, the detection of a distinct crystalline CaIJOH) 2 phase significantly above its normal dehydration temperature (415°C, as above) confirms the existence of a "superheated" CaIJOH) 2 phase which was previously only hypothesised based on observed delays in water release and/or weight loss.…”

“…Ca Looping, forms the basis of a number of emerging technologies in applications central to the energy issues of the XXIst century such as CO 2 capture, thermal energy storage and gasification. [9][10][11][12] Namely, hydrating sintered lime (CaO) in steam and then heating the resulting CaIJOH) 2 in the presence of CO 2 was reported to enable the production of active and attrition resistant CO 2 sorbents. This method allows significantly improving the reactivity of the lime sorbent and process economics.…”

“…[1][2][3] A number of Ca Looping schemes also involve the hydration of lime (CaO) and the subsequent dehydration and/or carbonation of the resulting CaIJOH) 2 . [11][12][13] This method can be used both to reactivate "spent" or inactive lime sorbents [10][11][12][13] as well as to produce new and stronger sorbents for Ca Looping processes. [4][5][6] For example, the dehydration and carbonation reactions of CaIJOH) 2 are an essential part of a number of existing schemes such for CO 2 capture from the atmosphere 7 or flue gases, 8 as well as sorbent production and reactivation techniques in the context of Ca Looping processes for CO 2 capture.…”

“…9,11,13 Namely, the dehydration reaction (eqn (2)) normally begins at~300-450°C, depending on the experimental conditions in general and water vapour pressure in particular. 9,11,13 Namely, the dehydration reaction (eqn (2)) normally begins at~300-450°C, depending on the experimental conditions in general and water vapour pressure in particular.…”

Investigation of Y2O3/MgO‐modified extrusion–spheronized CaO‐based pellets for high‐temperature CO2 capture

“…It was of much significance to conduct CO 2 capture performance and mechanical behavior comparison of the Y 2 O 3 /MgO‐supported CaO‐based pellets with other dopant‐included sorbents, such as CeO 2 , ZrO 2 , Al 2 O 3 , and cement . Therefore, some work in which the cyclic CO 2 sorption performance of CaO‐based sorbents was obtained under similar condition to this work was summarized and presented in Figure .…”