Title : A new approach for modeling catalytic processes in column apparatuses
Abstract:
The presented theoretical analysis in the plenary lecture shows, that the mechanics of continua cannot be used to model the gas (liquid)-solid catalytic processes in the column apparatuses, because fluid velocities in the gas (liquid) phase and interphase gas (liquid)-solid boundaries are unknown and cannot be determined. These problems are overcome by replacing the surface (heterogeneous) phase boundary reactions with equivalent volume (homogeneous) reactions, and the unknown phase velocities are replaced by the average velocity of the cross section of the column. This leads to parameters in the models that must be determined by experimental data.
The modeling of the catalytic processes is related with the creation of new type of convection-diffusion and average-concentration models.
The convection-diffusion models permit the qualitative analysis of the processes only, because the velocity distribution in the column is unknown. On this base is possible to be obtained the role of the different effect in the process and to reject those processes, whose relative influence is less than 1%, i.e. to be made process mechanism identification.
The average-concentration models are obtained from the convection-diffusion models, where average velocities and concentrations are introduced. The velocity distributions are introduced by the parameters in the model, which must to be determined experimentally.
The theoretical analysis of the average-concentration models of the catalytic process in the column apparatuses (in the approximations of the mechanics of continua) shows, that the radial non-uniformity of the axial component of the fluid velocity is the reason for the reduction of the efficiency of the processes and the appearance of the experimentally determinable parameters in the models. The plenary lecture shows, that the tangential introduction of the gases (liquids) into the column minimizes the radial non-uniformity of the axial component of the fluid velocity and cancels the values of the experimentally determinable parameters. The only parameters that remain to be determined are the interphase mass transfer coefficients (as volume factors), but they do not depend on the diameter of the column and can be determined by experimental data obtained on a model (small diameter) column.
