On deconvolution for understanding synergistic effects in co-pyrolysis of pinewood and polypropylene

Abstract

The synergistic effects on syngas observed in co-pyrolysis of pinewood and polypropylene (PP) were systematically investigated on a fixed bed reactor with tailored feedstock configurations in this paper. The synergistic effects focused on evolutionary and cumulative behaviors of evolved syngas were quantified by juxtaposing the results from co-pyrolysis of pinewood-PP mixtures with weighted results from the pyrolysis of pinewood and PP as individual components. Examination of different feedstock configurations revealed quantified contributions on volatile interactions and catalytic effect of char to the overall synergy. Results showed that syngas yield, H2 yield and CO yield with co-pyrolysis were promoted by 27%, 80% and 63%, respectively, as compared to the weighted aggregates from individual pyrolysis. Reduced char residue and improved energy yield in co-pyrolysis contributed to a remarkable enhancement in apparent thermal efficiency from 69.93% to 80.67%. Interactions between volatiles evolved from pinewood and PP suppressed CnHm formation while significantly enhancing H2 and CO yields. Mutual interactions between the volatiles accelerated the evolution of each gas component during co-pyrolysis. Pinewood char showed a negligible catalytic effect in evenly mixed configuration, but this effect was pronounced in separated PP and pinewood char. The porous structure of pinewood char can be easily blocked by the fused PP during co-pyrolysis, which was responsible for the delayed CnHm and syngas evolution. This paper provides results that help assist to elucidate the detailed synergistic mechanism during co-pyrolysis of biomass and plastic wastes.