Morphology and structure evolution of flaky char particles during CO₂ gasification

High temperature stage microscope was applied to observe morphology evolution of flaky char particles during gasification. Raman spectroscopy was used to analyze crystalline structures of gasification semicoke. Effect of gasification temperature (1000-1200℃) and initial equivalent diameter (1.00-1.60 mm) on morphology and structure evolution were examined. The results show that particle shrinkage in later stage of gasification is more intense than that in early stage. Within tested gasification temperature, the particle ASR (area shrinkage ratio) and VSR (volumetric shrinkage ratio) decrease with increasing temperature. The initial particle size of char has a significant effect on particle shrinkage. At 1100℃ the shrinkage trend of particle marks a turning point at initial diameter of 1.30 mm. The variation of char apparent density is dominated by carbon consumption. When the carbon conversion reaches 80%, the apparent density ratio linearly decreases below 0.4. At the same gasification temperature, with increasing carbon conversion the graphitization of char reduces first and then increases, while the amorphous carbon is opposite.