RTD STUDY BY CFD UN REACTOR

Abstract

The Residence time distribution (RTD) of a chemical reactor is a probability distribution function that describes the amount of time fluid elements could spend inside the reactor. Chemical engineers use the RTD studies to characterize the mixing and flow within reactors and to compare the behavior of real reactors to their ideal models. This is useful not only for troubleshooting in the reactors, but in estimating the yield of a given reaction and designing reactors. Since the fluid mechanics in most of the chemical process equipments is very complex, it is practically impossible to estimate axial mixing using fundamental principles. Also the various models proposed deviate from each other at different flow regions. CFD used for RTD studies are giving satisfactory results for various flow ranges. So the use of CFD for study of RTD in reactors for various flow ranges has been increased over a decade. In the present work, the turbulent flow pattern in pipe has been simulated using k-epsilon model and profiles of axial velocity were found. The CFD simulations have been done to determine the residence time distribution (RTD) in turbulent region using the Nitrogen-Argon system. An extensive comparison is done between the CFD predicted RTD curve and experimental curve (Flint and Einseklam (1969)). There is 7% error between the two RTD curves obtained. Then RTD in laminar flow through Plug flow Reactor for Water-phenol system is also studied using CFD simulations. The CFD predicted RTD curve is compared with the experimental data obtained from laboratory. Effect of mass flow rate of fluid entering the reactor, mass fraction of solute, geometry of system on RTD is also studied in this work. The results obtained have been explained and suitable conclusion was arrived upon