CaO and MgO as physical barriers

https://doi.org/10.1002/cssc.202002078

“The physical separation of two adjacent CaO (or CaCO₃) grains increases the length of the diffusional paths, hence increasing the timescale of sintering. Zhang et al.⁸⁰ investigated the sintering of two separated spherical sorbent nanoparticles (CaO-CaO or CaO-MgO) during CO₂ sorption conditions and in an inert atmosphere via molecular dynamics simulations. The authors show that the carbonation of previously separated CaO nanoparticles leads to the formation of a handle-like, strongly sintered particle as shown in Figure 7 a, b, indicating that the volume expansion during carbonation is the main contributor to sintering of CaO-based sorbents. Simulations with varying radial distances between the CaO nanoparticles revealed that an increase in the radial distance significantly reduced sintering and in turn increased the CO₂ uptake during carbonation. Indeed, simulations of a stabilized nanoparticle system (CaO-MgO) showed that the presence of a metal oxide stabilizer significantly reduced the degree of inter-particle sintering, resulting in a substantially higher CO₂ uptake of the individual CaO nanoparticles, see Figure 7c.”

“Figure 7 Snapshots of molecular dynamics simulations of (a) sintering of CaO nanoparticles at different temperatures (b) sintering of CaO nanoparticles in the presence of CO₂ and (c) sintering of a CaO and MgO nanoparticle in the presence of CO₂. Reprinted with permission from Ref. [80]; copyright PCCP Owner Societies, 2012.”