Residence time distribution (RTD) revisited

Alírio E Rodrigues

doi:10.1016/j.ces.2020.116188

Residence time distribution (RTD) revisited

Chem Eng Sci. 2021 Feb 2:230:116188. doi: 10.1016/j.ces.2020.116188. Epub 2020 Oct 4.

Author

Alírio E Rodrigues¹

Affiliation

¹ Emeritus Professor, Laboratory of Separation and Reaction Engineering (LSRE), Associate Laboratory LSRE-LCM, Department of Chemical Engineering, Faculty of Engineering, University of Porto (FEUP) Rua Dr Roberto Frias s/n 4200-465 Porto, Portugal.

Abstract

Residence Time Distribution (RTD) theory is revisited and tracer technology discussed. The background of RTD following Danckwerts ideas is presented by introducing "distribution" functions for residence time, internal age and intensity function and how to experimentally obtain them with tracer techniques (curves C and F of Danckwerts). Compartment models to describe fluid flow in real reactors are reviewed and progressive modeling of chromatographic processes discussed in some detail. The shortcomings of Standard Dispersion Model (SDM) are addressed, the Taylor-Aris model discussed and the Wave Model of Westerterp's group introduced. The contribution of Computational Fluid Dynamics (CFD) is highlighted to calculate RTD from momentum and mass transport equations and to access spatial age distribution and degree of mixing. Finally smart RTD and future challenges are discussed.

Keywords: CFD modeling; Compartment models; Internal age distribution; Residence time distribution; Standard dispersion model; Taylor-Aris and Wave models.

Publication types

Review