Adsorption and ion exchange fixed-bed operation scale-up: a new parameter to be taken into account

The paper aims at investigating the importance of including chemical heterogeneity in scaling up fixed bed operations as it has been found to induce additional dispersion. A discrete chemical heterogeneity distribution has been considered in the one-dimensional advective-dispersive equation. The partial differential equation was solved using finite volumes method based on the Adam-Bashforth algorithm. Increased dispersion was estimated comparing breakthrough curves second order moments keeping identical hydrodynamic properties as well as medium global capacity. First, effect of the same chemical heterogeneity distribution was evaluated at different bed lengths. Then, different distributions were considered at different bed lengths too. Effect of chemical heterogeneity was found decreasing with the medium size but depending on the distribution type though a constant mean value of the distribution. As a result, dispersion increase due to chemical heterogeneity depends essentially on the column size and on the nature of heterogeneity distribution causing dependence of the breakpoint time on both. Consequently, when the contact time is the scaling parameter, scale-up requires an additional relation which accounts its variation with the nature and the scale of chemical heterogeneity.

کلیدواژه ها:

adsorption ، chemical heterogeneity ، dispersion ، fixed bed ، porous media