What are the limitations of rate equation theory?

The limitation of rate equation theory is that the change of cross-sectional area is considered in the derivation model, but it is considered that the cross-sectional area is unchanged when it is brought into parabolic rate equation. Dutch scholar vanDeemter absorbed some concepts in the tray theory, further linked the chromatographic distribution process with the molecular diffusion and mass transfer process in gas-liquid two phases, and established the kinetic theory of chromatographic process, that is, the rate theory.