Effects of residual carbon on slag flow characteristics of Zhundong high-alkali coal under oxy-fuel condition

The implementation of oxy-fuel combustion technology in slag-tapping cyclone furnace holds significant promise for addressing the challenges associated with the combustion of Zhundong high-alkali coal. However, the flow characteristics of the Zhundong high-alkali coal slag under oxy-fuel condition remain unclear, while the influences of residual carbon have yet to be fully understood. In the present study, a high-temperature flow experimental system was designed to investigate the effects of residual carbon content, degree of graphitization of residual carbon, and atmosphere on the high-temperature flow behaviors of the high-alkali coal slag. The scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) was utilized to further analyze the microscopic characteristics and elemental distribution within the slag samples. The results reveal that under oxy-fuel condition, the flow length of slag diminishes as the content of residual carbon increases. The flow length and flow area of the slag without residual carbon are 42.4 mm and 561.2 mm2, respectively, while the flow length and flow area of the slag decrease to 9.9 mm and 89.1 mm2, respectively, when the residual carbon content is 10 %. The slag samples blended with residual carbon exhibit rougher and looser surfaces, with numerous particles adhering to them. In addition, the higher the degree of graphitization in the residual carbon, the lesser its impact on the flowability of the slag. Compared with oxy-fuel and air atmospheres, the residual carbon has a lesser effect on slag flow behaviors in inert atmosphere. The slag samples in oxy-fuel atmosphere display relatively smooth surfaces with dense structures and extensive liquid-phase areas. On the contrary, slag samples under inert condition feature fewer smooth surfaces, with adherent particles visible along the edges of the structure. The mechanism of the effects of residual carbon on the flow characteristics of high-alkali coal slag under different atmospheric conditions is elucidated in the present study, which can contribute to clean and efficient energy production.