Thermal Activation of CaO-Based Sorbent and Self-Reactivation during CO₂ Capture Looping Cycles

Abstract

In this study, the thermal activation of different types of CaO-based sorbents was examined. Pretreatments were performed at different temperatures (800--1300 degrees C) and different durations (6--48 h) using four Canadian limestones. Sieved fractions of the limestones, powders obtained by grinding, and hydroxides produced following multiple carbonation/calcination cycles achieved in a tube furnace were examined. Pretreated samples were evaluated using two types of thermogravimetric reactors/ analyzers. The most important result was that thermal pretreatment could improve sorbent performance. In comparison to the original, pretreated sorbents showed better conversions over a longer series of CO2 cycles. Moreover, in some cases, sorbent activity actually increased with cycle number, and this effectwas especially pronounced for powdered samples preheated at 1000 degrees C. In these experiments, the increase of conversion with cycle number (designated as self-reactivation) after 30 cycles produced samples that were approximately 50% carbonated for the four sorbents examined here, and there appeared to be the potential for additional increase. These results were explained with the newly proposed pore--skeleton model. This model suggests, in addition to changes in the porous structure of the sorbent, that changes in the pore--skeleton produced during pretreatment strongly influence subsequent carbonation/ calcination cycles.

Additive effects of steam addition and HBr doping for CaO-based sorbents for CO 2 capture

“…Such findings are consistent with those of (Lysikov et al, 2007) and confirmed by (Manovic and Anthony, 2008) who demonstrated that pre-sintering limestones by heating them to a high temperature (> 1200 °C ) for long periods of time (up to 24 h), though initially causing significant sintering and loss of reactivity, led to an increase in the long-term reactivity of the limestones. It was hypothesised (Lysikov et al, 2007) that rapid initial sintering of the sample led to the formation of a hard internal skeleton of an optimal pore-size distribution which acted as a support for subsequent cycles of carbonation and calcination.…”

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.…”

Novel Ni–Mg–Al–Ca catalyst for enhanced hydrogen production for the pyrolysis–gasification of a biomass/plastic mixture

“…CaO is a common CO 2 absorbent, which can be used repeatedly by the cycle of carbonation/decarbonation [27,28]. That reaction is described as…”