Regulation Mechanism of Solid Waste on Ash Fusion Characteristics of Sorghum Straw under O2/CO2 Atmosphere

Co-combustion of solid waste and biomass can alleviate biomass ash-related problems. To investigate the effects of solid waste on the ash fusion characteristics of biomass and its variation mechanisms under an oxidation atmosphere, an X-ray diffraction, thermogravimetric analyzer (TG), scanning electron microscope (SEM), and FactSage calculation were used to examine the ash fusion behaviors of sorghum straw (SS) with the addition of textile dyeing sludge (TDS) or chicken manure (CM). The ash fusion temperature (AFT) of SS increased gradually with the TDS ash addition; with CM ash addition, the AFT of SS mixtures increased rapidly (0–20%), decreased slightly (20–30%), and finally increased slowly (30–60%). The generations of high melting point (MP) minerals (e.g., KAlSi2O6, Fe2O3, and Fe3O4) led to an increase in the AFT of TDS-SS mixtures. The K+ in silicate was gradually replaced by Mg2+ or Ca2+, which caused the generations of high-MP minerals (e.g., Ca3MgSi2O8, Ca2MgSi2O7, and CaMgSiO4). The TG analysis showed that the additions of TDS or CM ash slowed down the weight loss of SS mixed ash due to the formation of high-MP minerals. The SEM and FactSage calculations were also explained with the AFT change and their variation mechanisms. The result provided effective references for the AFT regulation during the co-combustion of biomass and solid waste.