Magnetite loaded carbon fine particles as low-cost CO2 adsorbent in a sound assisted fluidized bed

Abstract

CO2 adsorption with solid sorbents is one of the most promising options for post-combustion CO2 capture strategies. Typical post-combustion flue-gas conditions are CO2 1–15%vol. and atmospheric pressure and the performances of solid sorbents under typical flue gas conditions have been poorly investigated. In that condition the CO2 uptake capacity is influenced primarily by material functionality effects rather than material pore metrics so materials with a distinctive surface chemistry (presence of activated surface atoms or sites) could find applications in adsorption technologies. Hence the sorbent selection became a key point because the materials should be convenient from the economic point of view but versatile in post-combustion conditions. Recent studies of CO2 adsorption on low-cost iron metal oxide surfaces strongly encourage the possible use of metal oxide as sorbents, but the tendency of magnetite particles to agglomerate causes a lowering of CO2 uptake capacity. The dispersion of magnetite nanoparticles on carbonaceous matrix appears to be a promising strategy to overcome this shortcoming. This work investigates the adsorption behavior of CO2 on composite materials prepared coating a low-cost commercial carbon black (CB) with magnetite fine particles. The CO2 capture capacity of composites produced at different CB load was evaluated on the basis of the breakthrough times measured at atmospheric pressure and room temperature in a lab-scale fixed bed micro-reactor. A CB–FM composite has been selected to verify the possibility of carrying out a two-stage operation and the thermochemical stability in a sound assisted fluidized bed. To this aim the reactor has been firstly operated for CO2 adsorption and then for regeneration. The effect of multiple cycles of adsorption and desorption steps has been also quantified.