Study On Determination Of Efficient Diffusion Coefficient Of Porous Materials

Diffusion throughout all aspects of chemical engineering, such as catalysis, adsorption and membrane separation processes, fluid mixtures in porous media diffusion is the decisive factor in the decision process performance. Gas diffusion in porous media in the free gas is different from the solid medium, the diffusion coefficient will be reduced. Different porous materials have different porosity and tortuosity. Therefore, porous materials quickly and accurately determine the porosity and gas in porous media and the effective diffusion coefficient in the chemical and research work are of great significance.(1) Based on quasi steady state assumption and material balance, a new way to determine the diffusion coefficient and porosity of porous materials has been developed. First cover a porous membrane on the opening of a glass pipe with a specific liquid, after a certain time measure the drop of the surface of liquid, then balance the material in the glass tube and the porous material membrane, respectively to get the diffusion coefficient and porosity of the porous material. The results of the new method are comparable to the traditional Hg method, when demonstrate the new method is simple, easy to carry out and reliable.(2) Evaporation pipe method were determined in H2O-Air system and Ethanol-Air system. Discussed the diffusion distance, diffusion time and diffusion temperature in the steady-state diffusion model, then established the suitable gas diffusion length, time, and temperature.(3) Evaporation pipe method for determination of diffusion coefficients of binary gas is based on the principle of steam diffusion in porous media through physical and mathematical models. Covered the porous membrane in the evaporation pipe, the diffusion processes divided into two parts, one for free diffusion into the free gas. the other for a period of diffusion into porous membrane. In glass tube, free air section and porous media section of the material balance of liquid vapor to obtain the effective diffusion coefficient of steam in porous media, and then calculate the porosity of the porous medium. And then calculate the porosity of the porous medium. This method could widely used in other fields, such as Chemical Engineering. Building Materials and Food Industry. It has important significance in improving calculation accuracy and enhancing labour efficiency.