Steam Reactivation of Spent CaO-Based Sorbent for Multiple CO₂ Capture Cycles

Abstract

This study examines steam reactivation of sorbent to improve the reversibility of multiple CaO-CO2 capture cycles. Experiments to obtain spent sorbent were performed in a tube furnace, and reactivation was achieved using steam in a pressurized reactor. Sorbent activity for CO2 capture was then tested in a thermogravimetric analyzer (TGA), in multi-cycle carbonation tests. After reactivation the sorbent had even better characteristics for CO2 capture than that of the natural sorbent. The average carbonation degree over 10 cycles for the reactivated sorbent approached 70%, significantly higher than for the original sorbent (35-40%). This means that the same sorbent may achieve effective CO2 capture over a large number of cycles, in the absence of other phenomena such as attrition. Partially sulfated sorbents may also be reactivated, but hydration itself is also hindered by sulfation.

The calcium looping cycle for CO2 capture from power generation, cement manufacture and hydrogen production

“…calcium acetate, calcium ethanoate (Lu et al, 2006;Lu, H. et al, 2008;Liu et al, 2010a) with particular success using a MgO support (Liu et al, 2010b) to similarly enhance the reactive surface area; dispersal of CaO within an inert porous matrix such as mayenite (Li et al, 2005;Li et al, 2006;Pacciani et al, 2008a) to improve mechanical stability; and use of cementitious binders (Manovic and Anthony, 2009a; to improve mechanical stability. Sorbent reactivity can be periodically improved by hydration of calcined sorbent, though this is often at the expense of mechanical strength of the sorbent (Hughes et al, 2004;Fennell et al 2007b;Manovic and Anthony, 2007;Manovic and Anthony., 2008a;Sun et al, 2008;Zeman, 2008). Thermal preactivation / pre-treatment, by treating sorbent at high temperature under N2, has been found to improve long-term reactivity of sorbents (Manovic and Anthony, 2008b;.…”

Degradation study of a novel polymorphic sorbent under realistic post-combustion conditions

“…These approaches include: the use of dopants [10] [11] [12]; hydration and steam reactivation [13] [14] [15]; thermal pre-sintering [16] [17]; spacer molecule incorporation [18] and sintering resistant internal supports [19] [20]. Recently, Zhao et al [21] has reported a CaO-based sorbent incorporating a supporting structure composed of dicalcium silicate (Ca2SiO4, from here on referred to as C2S which is common notation of this compound in the cement industry) which enabled the sorbent to retain a very high proportion of its carrying capacity throughout many cycles.…”

In situ X-ray diffraction of CaO based CO2 sorbents

“…13,23,24 Hydration of calcined material followed by decomposition can be used as a regeneration method of sintered materials since it can restore a high surface area. [25][26][27][28] A major drawback of hydration as a regeneration method is the reduced mechanical strength of the regenerated material. 26,29,30 However, by hydrating in a CO 2 atmosphere, the reduction in mechanical strength can be retarded.…”