Two-stage pyrolysis of refuse-derived fuel: A valuable pathway for enhancing hydrogen production

This study investigates the effect of alumina (Al2O3) as packing material in a two-stage pyrolysis process applied to refuse-derived fuel (RDF). A lab-scale batch reactor system was used, operating at 500 °C in the pyrolysis stage and up to 800 °C in the secondary cracking stage. Two sets of experiments were conducted: one using inert stainless-steel spheres and another using Al2O3 spheres in the cracking reactor. The presence of Al2O3 significantly altered the distribution of pyrolysis co-products. Gas yield increased from 37.9 wt% up to 41.5 wt%, oil yield decreased from 41.8 wt% down to 18.5 wt%, and char yield nearly doubled from 20.3 wt% up to 40.0 wt%. The hydrogen content in the gas was strongly influenced, i.e. it increased from 20.1 vol% up to 58.4 vol%, indicating strong cracking and reforming activity. Elemental analysis revealed a marked shift in carbon retention, with 52.1 wt% of initial carbon retained in char. Van Krevelen analysis showed H/C and O/C ratios of 0.16 and 0.008, respectively, for char obtained with Al2O3, indicating highly carbonized and dehydrogenated material. These findings highlight the potential of Al2O3 as an effective alternative to conventional catalysts for enhancing gas quality and carbon valorization in RDF pyrolysis.