Effects of reflux and reflux-barrier location on solvent extraction through cross-flow flat-plate membrane modules with internal reflux

The influence of reflux as well as reflux-barrier location on cross-flow membrane extraction through the flat-plate module with internal reflux has been investigated. The recycle barrier is placed in the raffinate phase to divide the flow channel of width B into an operating subchannel of width ΔB and a reflux subchannel of width (1 − Δ)B. Considerable improvement in performance is obtainable if cross-flow membrane extraction is operated with internal reflux which provides the increase of fluid velocity, resulting in reduction of mass-transfer resistance. It was further found that suitably adjusting the recycle-barrier location in raffinate phase such that 0.75 < Δ < 0.9, is beneficial to total mass-transfer rate and thus, the reflux ratio can be reduced for achieving the same performance with the reflux barrier located at the centerline, Δ = 0.5. However, the hydraulic dissipated energies though are small, they increase rapidly with reflux ratio as well as when the recycle barrier goes far from the centerline for improving performance. Therefore, the increase of operating cost due to the friction loss of fluid flow should be also taken into consideration.