Analysis of Microstructural Change Mechanism During High-Temperature Pyrolysis of Carbonaceous Reducing Agents for Silicon Smelting

In this study, X-ray diffraction, Raman spectroscopy, Fourier infrared spectroscopy, and reaction kinetics were used to investigate the microstructure and graphitization mechanism of carbon-reducing agents used in silicon smelting. The results showed that petroleum coke and charcoal exhibited graphitization-like behavior within the temperature range of 1300-1600celcius, of which the graphitization degree of petroleum coke was the highest. The correlation analysis revealed that the graphitization degree (g) and the area ratio of D peak to G peak of Raman spectroscopy (R) had a strong correlation coefficient (R-2 > 0.9), and the transition temperatures of petroleum coke and charcoal to the graphitization stage were 1720 and 2457celcius, respectively. These results showed that petroleum coke was the first to enter the graphitization stage, and the carbon layer structure formed was more stable and orderly, with a higher degree of aromatization. However, due to the high content of alkali metals and the existence of porous structure in charcoal, the reactivity of charcoal was significantly enhanced, thus inhibiting the graphitization reaction. This study provides valuable information for the subsequent research on the mixing ratio of different carbon-reducing agents in silicon smelting.