Cyclic CO2 Capture Behavior of Limestone Modified with Pyroligneous Acid (PA) during Calcium Looping Cycles

In this work, pyroligneous acid (PA) was used to modify limestone, and the CO2 capture capacity in calcination/carbonation cycles was consequently strengthened. The cyclic CO2 capture behavior of PA-modified limestone was investigated in a thermogravimetric analyzer and a dual fixed-bed reactor. The main component of the PA-modified limestone was found to be calcium acetate hydrate. The optimum ratio of PA to limestone was found to be 20 mL/g. The PA-modified limestone was found to retain a higher CO2 capture capacity for carbonation at 700 °C. The carbonation conversion of the PA-modified limestone achieved 0.33 after 103 cycles, whereas, for the original sorbent, the conversion was just 0.078 under the same reaction conditions. The modification of limestone increased the surface area and pore volume of the calcined material during cycles. Furthermore, the calcined form of the modified limestone had more pores in the ranges of 1.8–4.6 and 18–155 nm, and as a result, its surface area and pore volume were both expanded.