Systematic study on ash fusion behavior and structural transformation during co-gasification of two typical agricultural by-products.

Abstract

Biomass gasification is an effective approach to enhance the economical utilization of agricultural residues. However, the specifics of the ash chemistry composition lead to complex the ash fusion behavior, which significantly affects the long-term stable operation of gasifiers. In this study, a potassium-rich corn cob (CC) and a silica-rich rice husk (RH) were used as raw materials. A multi-scale method combining ash fusion temperature measurement, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and FactSage thermodynamic simulation was employed to systematically investigate the mechanism of ash fusion temperature with blending ratio during co-gasification. The results showed that as the RH content increased, the ash fusion temperature exhibited the V-shaped trend of first decreasing and then increasing, with the minimum value occurring at the RH addition of 30%. For CC, phosphorus and silicon existed as a stable network structure, which was the main reason for its high ash fusion temperature. When the RH content was 30%, K2O reacted with SiO2 to form a low-melting-point eutectic while simultaneously disrupting the stable Ca-P framework structure to generate low-melting-point compounds containing K-Ca-P structures, thereby reducing the ash fusion temperature. When the RH ratio exceeded 70%, the excessive SiO2 re-polymerized to form a highly polymerized silicate network structure dominated by Q3(Si) and Q4(Si), leading to a significant increase in ash fusion temperature. This study provides a theoretical basis for ensuring safe and efficient gasifier operation by regulating ash fusion behavior through raw material blending.

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