The mass transfer with chemical reaction model is investigated. A diffusion type of model is proposed for modeling of the scale effect in column apparatuses, where the velocity and concentration distributions are replaced with theirs average values at the cross-section areas of the column. The obtained results show that scale effect is related with one parameter which is possible to be calculated using experimental data for average concentration at some different points at the column height. (C) 2008 Elsevier Ltd. All rights reserved.