CFD Simulation of Liquid Hold-Up in Structured Packed Columns

Different types of structured packings commonly used in distillation columns posses different wetting characteristics due to their shape and the nature of their surface [1]. Liquid holdup is an important parameter that links many of the design parameters [2]. In this study, Computational Fluid Dynamics (CFD) has been used to determine the liquid film thickness in four types of structured packings (Mellapak 250 X, Mellapak 250Y, Flexipak 1Y and Gempak 1A). Model parameters were evaluated in two dimensional simulations using two-fluid model and standard k- ε turbulence model .By predicting the liquid film thickness, liquid hold up can be calculated from theoretical model [3]. In this paper, in all the packings by approaching to the flooding point, the thickness of the liquid film will increase, due to direct correlation of the liquid accumulation with liquid film thickness, in all of the packings the liquid accumulation will increase. It is observed that the packing Mellapak 250Y at the flow rate of the gas higher than 2.21m/s would flooding and these flow rates for the packings Mellapak250X, Flexipak1Y and Gempak1A are 2.75m/s, 2.33m/s and 0.98m/s respectively. The results agree well with experimental data available from the literatures.The average relative error for prediction of liquid hold-up in Mellapak 250 Y, Mellapak 250 X, Flexipak 1Y and Gempak 1A are 15.20%,17.6%,14.98% and 13.04% respectively.

Keywords:

Structured packed column , Computational fluid dynamics , liquid film thickness , liquid hold up