Fractal characteristic of three Chinese coals

Experimental and theoretical investigation about coal/char structure is presented. Surface structures of parent coal and char with different burn-off ratios were analyzed. We introduced the fractal theory into Scanning Electron Microscopy image analysis and utilize the particle surface fractal dimension (Dps) to quantitatively describe the surface character of coal/char particles. Dps of three Chinese coals reach their maximum in the 35–45 wt% char burn-off interval and then decrease with increasing carbon burn-off ratio. The inner-pore information of coal/char particles was determined by N2 isotherm adsorption/desorption. Using fractal BET model, internal surface fractal dimension (Ds) of coal/char particles was calculated. The Ds change trend of three Chinese coals is similar to their SBET development. It means the Ds can quantitatively describe the inner pore structure character of coal/char particles.