Use of steel slag as a catalyst in CO₂-cofeeding pyrolysis of pine sawdust

To seek an innovative way for simultaneous waste management and energy recovery, two waste materials (pine sawdust: PSD and steel slag: SS) were used in the pyrolysis process. PSD was used as a carbonaceous material for pyrolysis, and SS was used as a catalyst. Also, to achieve a more sustainable conversion system, a viable use of carbon dioxide (CO₂) as a raw material in the non-catalytic/catalytic pyrolysis process was evaluated. Hence, the present study laid great stress on the CO₂ effects. The present study pointed the optimistic technical features in line with the use of CO₂ in the pyrolysis process. Exploiting CO₂ in pyrolysis of PSD offered a strategic way to control carbon reallocation from liquid to gaseous pyrolysates by the gas phase reactions (GPRs). The reactions of CO₂ and volatile pyrolysates led to CO enhancement, which was only observed at ≥ 600 °C due to the slow reaction kinetics of the GPRs of volatile pyrolysates and CO₂. Such the slow reaction kinetics was expedited remarkably when SS was acted as a catalyst. Moreover, CO₂ expedited thermal cracking of volatile pyrolysates including dehydrogenation, which led to the enhanced formation of CH₄ and H₂.