Objective: The classical mass transfer theory is not applicable for modeling the
mass transfer of chemical, absorption, adsorption and catalytic processes in column
apparatuses, where the velocity distributions and interphase boundaries are unknown. The
modeling of these processes is related with the creation of new type of convection-diffusion
models (for qualitative analysis) and average-concentration models (for quantitative
analysis), where the surface reactions are replaced by equivalent volume reaction, while the
velocity and concentration distributions are replaced by average velocity and concentrations.
The effect of the radial non-uniformity of the velocity in the average-concentration models is
introduced by model parameters, which must be obtained experimentally.
Method: The new convection-diffusion and average-concentration models are obtained in
the cases of different processes in column apparatuses: simple and complicated chemical
reactions, physical and chemical absorption, physical and chemical adsorption,
heterogeneous catalytic processes (physical and chemical adsorption mechanism). These
models are presented in the monograph Chr. Boyadjiev, M. Doichinova, B. Boyadjiev, P.
Popova-Krumova, “Modeling of Column Apparatus Processes” (Second edition), Springer-
Verlag, Berlin Heidelberg, 2018.
Result: Two hydrodynamic situations are considered, when the radial velocity component is
equal to zero, in the cases of an axial modification of the radial non-uniformity of the axial
velocity component and when the radial velocity component is not equal to zero.
Conclusion: The use of experimental data, for the average concentrations at the column end,
for a concrete process and column, permits to obtain the model parameters, related with the
radial non-uniformity of the velocity. These parameter values permit to use the averageconcentration
models for modeling of different processes.