High-Temperature Ash Behavior of Biomass: A Comparative Study of Corn and Wheat Straw

• • Corn straw ash (CSA) flow temperature is 1241 °C, higher than wheat straw ash (WSA) despite CSA having higher K2O and lower SiO2; this anomaly is due to elevated CaO (10.39%) and MgO (7.33%) in CSA promoting high-melting silicates (K2MgSiO4, K2Ca2Si2O7, CaSiO3). • • WSA, with lower CaO (4.92%) and MgO (2.82%), tends to form low-melting potassium silicates, resulting in a lower flow temperature (<1300 °C) and different slagging behavior. • • Both ashes exhibit crystalline slag behavior; CSA viscosity spikes sharply during cooling due to rapid crystal growth (KAlSiO4 grain size increases from 20.5 nm at 1350 °C to 192.9 nm at 1050 °C), while WSA viscosity remains high due to persistent KAlSiO4 and late-stage K2O2 precipitation. • • High P2O5 content (10.05%) in WSA induces a 'chemical dilution effect' that sustains KAlSiO4, leading to higher overall viscosity and rapid viscosity rise at the end of cooling; this suggests different mitigation strategies: for CSA, additives like Fe2O3 to promote low-temperature eutectics; for WSA, CaO/MgO addition to suppress KAlSiO4 formation.