Simulation of drop formation in a single hole in solvent extraction using VOF method
Multi-scale and/or multi-disciplinary approach to process-product innovation
CFD & Chemical Engineering- II (T3-4b)
Keywords: drop formation, single hole, wetting, contact angle, VOF
Formation of solvent drops in sieve plates is a very important phenomenon in solvent extraction. Small droplets are usually desired to increase the interfacial area available for mass transfer and to maximize the process efficiency. Formation of very small satellite drops is, however, a common problem, which is frequently met in industrial extraction equipment. Very small droplets are difficult to separate from the continuous phase and their presence can adversely affect the extraction efficiency. Formation of satellite drops can be affected by changes in flow conditions and in the mechanical structure of the sieve plates. Drop formation in sieve plates is a complex phenomenon, which depends on the flow velocity in the holes, physical properties of the liquid phases, like surface tension and density difference between the phases, material properties of the sieve plate, like the wetting properties and surface roughness, hole size and structure, distance between the holes and alignment of holes on the sieve plate.
The motivation of this study is the need to find optimal structure for the holes, optimal construction material for the sieve plates and optimal flow conditions in the holes to minimize the production of small satellite drops. At the same time, high mass transfer efficiency is required.
Drop formation in single holes is studied by using Computational Fluid Dynamics simulations. Simulations were carried out by using ANSYS CFX 10. The VOF method was implemented for the calculation of the location of the interface between the phases. To minimize the computational load the simulations were carried out as two-dimensional simulations.
The simulated results were verified by comparison to experimental observations obtained by high-speed video recordings. Experiments and simulations were carried out for different hole sizes, ranging from 2 to 4 mm, and for different flow velocities ranging from 0.1 to 0.4 m/s. The material of the plate was stainless steel. The surface of the steel was polished and cleaned with acetone to remove any contaminants. The shape of the hole was also varied including a shape of conical opening and a shape of conical contraction above the base level (volcano shape). The purpose of the different shapes was to produce different contact angles around the hole.
A reasonable agreement between the measured and calculated drop formation was observed in each case.
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 15:20 to 15:40, in session CFD & Chemical Engineering- II (T3-4b).
