Experimental and CFD Analysis of a Sieve Tray

Distillation is the most widely used separation process, allowing the separation of miscible liquids based on their relative volatility differences. Conventional models for distillation columns project are based on the hypothesis of well mixed phases, which can affect the process efficiency by neglecting the fluid dynamic effects. These phenomena, however, can only be considered by a detailed mathematical model, such as those applied on Computational Fluid Dynamic (CFD) studies. The present work aims to develop a CFD model capable of reproducing experimental fluid dynamic data on a sieve tray, such as volumetric fraction profiles and pressure drop, where clear liquid height can be calculated by subtracting the pressure drop associated with the vapor bubble formation and vapor flow through perforation (dry tray pressure drop). In this regard, physical data was obtained in a three-stage acrylic column, where the lower stage distributes the gas and the upper stage distributes the liquid, thus the pressure drop measures are taken in the middle stage. Water simulates the liquid phase and air, the gas phase. A transient three-dimensional model, with two Eulerian phases, was applied in a commercial CFD code, using k-epsilon turbulence model in both phases. The computational domain consists in the middle stage, where the physical data was obtained, using velocity and pressure-outlet boundary-conditions for inlets and outlets, respectively. Numerical volumetric fraction profiles, clear liquid height, total pressure drop and dry pressure drop results were compared with experimental data.