Evaluation on thermal pyrolysis of biomass straw waste: Focusing aspects of products yields, syngas emissions and solid products characterization

In this study, a systematic and quantitative investigation of the pyrolysis characteristics of biomass was conducted in a fixed-bed tubular reactor, and the influence of pyrolysis temperature on product yields, gas emission characteristics, and syngas compositions as well as physicochemical characterization of resulting solids (i.e., char/ash morphologies, mineral transformations, and elemental compositions) was explored in detail. The pyrolysis experiments were performed under N₂, and the resulting solid characterization was detected by XRD, SEM, and EDX. The results indicated that with increasing the pyrolysis temperature from 400 to 800°C, the gaseous product yields increased from 54.9% to 66.7%, while the solid product yield showed a reverse trend, varying within 27.7%–40.5%. Meanwhile, the volume fraction of H₂ in syngas increased from 7% to 33%, while the CO₂ presented an opposite trend, suggesting that high temperature favored H₂ formation and inhibited CO₂ formation. On the whole, the CO and CO₂ emissions were prior to CH₄, H₂, and C_nH_m in sequence. A large amount of sylvite (KCl), quartz (SiO₂), dolomite (CaMg(CO₃)₂), and pyroxene (CaMgSi₂O₆) in the resulting solids were identified in crystal phases. Higher pyrolysis temperature had a significant influence on solid microstructures, resulting in a relatively higher slagging tendency due to low melting eutectics containing K-rich and Ca-rich minerals.