Ash adhesion and elimination in the gasification process is one of the main challenges in maintaining a continuous operation of the plant. The properties of ash adhesion and elimination are mainly related to particle sintering behavior. Different sintering behaviors of Shenhua coal ash (SCA) and rice straw ash (RSA) below the inherent initial deformation temperature (IDT) were observed by using optical heating stage microscope (OHSM) under CO2 and Ar environments. The particle interaction of the RSA, the IDT of which was lower than that of SCA, was higher than that of SCA at the same temperature. Adding RSA to the SCA was an effective means of increasing particle sintering of SCA. The sintering reaction rate of ash particles highly increased at beginning of sintering stage. The effects of inorganic chemicals in the sintering process were evaluated by using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and typical fouling indices. The Ca and K were predominant contributors to the increase in sintering. The degree of sintering through the experiments was compared to a modified Frenkel sintering model, which accurately simulated the sintering tendency under isothermal conditions. (C) 2016 Elsevier B.V. All rights reserved.