Enhanced CO₂ capture by biomass-templated Ca(OH)₂-based pellets

Biomass-templated Ca(OH)₂-based pellets were synthesized for high-temperature post-combustion CO₂ capture. Four types of biomass-derived materials were used for sorbent templating: cardboard, maple leaves, date seeds, and white soft wood. After calcination at 850°C in air, composite pellets with leaves exhibited a high pore volume of 0.11cm³/g, compared to that of 0.07cm³/g for pellets without biomass addition. The alteration in porosity was attributed to the release of combustion gases during the combustion of biomass. After 20 capture cycles with no steam, these pellets captured 0.24g CO₂/g calcined pellets, compared to 0.18g/g for biomass-free pellets. The highest CO₂ uptake was achieved with pellets containing 10% leaves. This enhancement in CO₂ uptake allowed the possibility of doubling the binder content, thus improving the mechanical strength of the pellets. The introduction of steam to the carbonation environment resulted in relatively high uptakes of 0.53 and 0.41g/g for the first and 20th cycles, respectively. In general, all composite pellets modified with biomass displayed better performance than their counterpart pellets, indicating the benefits of biomass addition. The dispersed biomass ash also appears to have helped stabilize the morphology of these pellets as well as acting as a doping agent assisting CO₂ capture via enhanced diffusion. Considering the fact that such biomass materials are readily available and cheaper than synthetic organic materials by at least an order of magnitude, their utilization should not significantly increase the cost of the templated sorbent.