Hydrodynamics and residence time distribution of liquid flow in tubular reactors equipped with screen-type static mixers

Abstract

This paper discusses the characteristics of liquid flow through tubular reactors/contactors equipped with woven mesh, screen-type static mixers from hydrodynamic and macromixing perspectives. The effect of changing the screen geometry, number of mixing elements, reactor configuration, and the operating conditions, were investigated by using four different screen types of varying mesh numbers. Pressure drop was measured over a wide range of flow rates (2300⩽Re⩽21,500) and was found to increase with a decreasing mesh opening. Friction factor values are also reported in the work, when compared to other types of motionless mixers, screen-type mixers were found to require much lower energy requirements with very low recorded Z values (1.15⩽Z⩽5) that are two to three orders of magnitude lower than those reported for other motionless mixers.Furthermore, residence time distribution experiments were conducted in the transitional and turbulent regimes (2300⩽Re⩽11,500). Using a deconvolution technique the RTD function was extracted in order to quantify the axial/longitudinal dispersion. The findings highlight that regardless of the number and geometry of the mixer, reactor configuration, and/or operating conditions, axial dispersion coefficients that are lower than those of an empty pipe were always recorded. The wire diameter and mesh opening were found to directly affect the axial dispersion in the reactor, while, the number of elements showed a minor effect. Furthermore, the choice of the characteristic parameter used to calculate the Reynolds number was found to be of paramount importance in analyzing the data.