Characterization of Ash Melting of Reed and Wheat Straw Blend

Ash melting could cause severe problems in boiler operation, such as agglomeration of the fluidized bed. Our previous work has shown that the ash melting behavior of the blend of reed and wheat straw is complex and needs further investigation. The ash melting behavior was studied using different laboratory methods such as simultaneous thermal analysis, heating microscope, scanning electron microscopy with energy dispersive X-ray (SEM/EDX) analysis, and X-ray diffraction (XRD). In the thermodynamic modeling, we used FactSage software, which supplements well the results obtained by other methods and vice versa. The results indicated that melting started at 660-680 °C when Na and K salts were melted and molten K₂SO₄ covered the ash material; the content of liquid mass fraction was 13.8%, revealing that the studied ash blend could already be sticky at 680 °C. Intensive melting took place in the temperature range of 800-980 °C. The rapid melting between 950 and 980 °C was caused by the melting of SiO₂ and K₂MgSi₅O₁₂; the ash material became glassy and amorphous. We propose an alternative distribution of ash melting stages for the studied blend.