(317a) Effect of External Recycle on Extraction in Rectangular Membrane Modules

Effect of external recycle on extraction in rectangular membrane modules The solvent extraction carried out in a microporous membrane device, is a dis- persion-free separation process which can overcome the application limitations of conventional solvent extraction. The analysis of solvent extraction in the membrane modules with external recycle has been carried out by mass-transfer theory, analogous to heat transfer in recycled heat exchangers. When solvent extraction is carried out in a microporous membrane device, the membrane is generally in contact with two kinds of fluid at two sides (phase a and phase b) and if fluids a and b are miscible, then in the pores of membrane are filled with another fluid (phase c) which is immiscible with these two fluids. The solute is extracted from phase a to phase c and then to phase b, or vice versa. Application of the external or internal reflux to the design and operation of a mass-or heat- transfer equipment can effectively enhance the effect on mass or heat transfer. For solvent extraction through membrane modules, the recycle effect is suitable for the system with higher distribution coefficients where the fluid-phase mass-transfer resistances are more strongly predominate. The analysis of solvent extraction in the membrane modules with external recycle has been carried out by mass-transfer theory, analogous to heat transfer in recycled heat exchangers. Considerable improvement is achievable by recycle operation if the increase in mass-transfer coefficient by applying the recycle effect can compensate for the decrease in the driving force of mass transfer due to the dilution of inlet feed solution.