Evolution of pore fractal dimensions for burning porous chars

The evolution of pore fractal dimensions for three Chinese chars was investigated. The pores of porous chars can be classified into macro-, micro- and transition-pores based on their fractal dimensions. The radius ranges of the macro-, micro- and transition-pores may be different for various chars. For different conversions in the char combustion process, the fractal dimensions of the micro-pores for different chars are almost the same and the fractal dimensions of macro-pores for the same kind of chars are roughly unchanged. The effects of fractal structure on combustion rate are also discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.