In-situ ash sintering process analysis during the co-combustion of the coal gasification fine slag and corn straw

The co-combustion of coal gasification fine slag (CGFS) and biomass is proposed to enhance the poor combustion characteristic of CGFS and alleviate the ash-related issues of biomass. In this study, the sintering mechanism of CGFS ash (FA) and corn straw ash (SA) was revealed by in-situ image analysis and thermodynamic modelling. The sintering process of FA includes initial sintering stage (S1), holding stage (S2), and primary melting stage (S3). The S1 is initiated by the flow of the low-viscosity slag, whereas the subsequent S2 and S3 stages are predominantly governed by the crystallization and then the melting of anorthite with increasing temperatures, respectively. The AAEMs in SA loosens the structure of FA, thereby facilitating the onset of S1 at a low temperature. Concurrently, the anorthite is gradually converted to diopside, which possesses a lower melting point, and subsequently into sanidine, which exhibits a higher melting point. This transformation extends the temperature range across S1 and S2, leading to an initial decrease followed by an increase of ash fusion temperatures with the SA addition. The dry bottom boiler suits for the co-combustion of CGFS and corn straw and the boiler exit temperature is suggested to be higher than 968 °C.