Fourier trigonometric series algorithm used in Fick's diffusion law is extended to Fourier-Bessel algorithm in a fractal diffusion model for porous materials. It is applied to chemical engineering for computation of concentration distribution and relative adsorption. The fractal diffusion model introduces structure parameters d_f and θ Concentration distribution and relative adsorption calculated by fractal diffusion model are qualitatively consistent with those by Fick's diffusion law. d_f and θ exhibit different effects on concentration distribution of porous materials, and describe diffusion in porous materials well.