| Abstrakt: |
In the present study, 20 wt % K2CO3was added to coal and coal/biomass blends in a 20:80 wt % ratio and subsequently were heating-treated at 600 °C using CO2or N2atmospheres. The reactivity under oxy-combustion conditions (21% O2+ 79% CO2) was studied by thermogravimetry, and characterization of chars was carried out by N2adsorption, scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy. Higher activation energy for impregnated coal/biomass blends compared to impregnated coal was observed, likewise, for materials thermally treated with CO2. It is demonstrated that CO2gasification takes place together with O2combustion under oxy-combustion conditions. Isotopically labeled 13C18O2was used to confirm the participation of CO2gasification reactions at 450, 500, 550, and 600 °C in both catalyzed and uncatalyzed systems under O2+ CO2. The catalytic effect of potassium promotes CO2gasification, and the highest CO (12C18O) desorption was obtained with impregnated samples. It is possible to suggest that CO2gasification reactions follow different reaction pathways in the presence or absence of potassium. The catalytic gasification reaction proceeded preferentially through a molecular CO2(13C18O2) adsorption route, while the noncatalyzed systems advanced using a dissociative adsorption pathway. |
