Abstract: A fractal pore diffusion model of fiuidS in porous media which is in good agreement with the experimental data of the coke-CO2 reaction, has been derived by using the Mandelbrot's fractal length-area relation. Based on the model, a new formula and its interpretation about the tortuosity of pore structures of a porous medium have been suggested, from which the fructal pore dthesion resistance has been defined. The resistance ascends obviously with the fmctal pore dimension and the conversion rutio increasing, especially in the middle-latter period of fiuid-solid reactions.

Key words: fractal model, pore diffusion, new tortuosity, fluid-solid reaction