<p>Co-combustion of biomass and coal offers a promising approach to reduce carbon emissions in traditional coal combustion processes, supporting the carbon peak and carbon neutrality strategy. However, interactions between biomass ash and coal ash components can lead to the formation of low-melting eutectics, causing ash-related issues such as slagging, sintering and scaling. The thermal properties and mineral evolution of ash during the co-combustion of rice husk (RH) and Shanxi coal (SC) were investigated in this study. The effects of blend ratio, atmosphere and combustion temperature on mineral evolution of ash were studied using a tube furnace reactor. The ash characteristics were investigated using XRF, ICP-MS, XRD, SEM and ash fusion point. The results showed that the thermogravimetric (TG) curves shifted to lower temperatures with an increasing in the RH ratio. Two reaction stages were observed: devolatilization (Stage I, 200–350&#xa0;°C) and combustion (Stage II, 350–600&#xa0;°C). The deformation temperature, softening temperature, hemisphere temperature and flow temperature values displayed a “V”-shaped trend with variation in the RH ratio. Alkali metals in the RH ash reacted with SiO₂ and Al₂O₃, forming low fusion point eutectics such as KAlSi₃O₈, Ca₂Al₂SiO₇ and CaAl₂Si₂O₈ that lowered the ash fusion point. The ash fusion point initially increased and then decreased as O₂ concentration increased. An oxygen-rich atmosphere and elevated combustion temperatures promoted the reaction between alkali metals and aluminum silicates, forming low-temperature eutectics. These findings demonstrate that adding RH can effectively improve SC combustion, while SC ash mitigates slagging issues associated with RH ash.</p> Graphical Abstract <p></p>