|
Ultrafiltration is a pressure-driven membrane process used
for the separation of macrosolutes from a solvent, usually
water. The permeate flux of ultrafiltration of
macromolecular solution is usually analyzed by the gel
polarization model 、 the osmotic ressure model and the
resistance-in-series model. In the present study, the gel
polarization model and the resistance-in-series model have
been modified to improve the theoretical predication.
Experimental work has been carried out for
polyvinylpyrrolidone solutions which were ultrafiltrated by
using polysulfone hollow fiber membrane module. The
experimental data agree quite well with the correlation
equation based on the modified resistance-in- series model.
This modified model was then employed for optimum design of a
hollow fiber membrane module with total length of hollow
fibers N*L fixed . It was found that under certain solution
concentration Ci、 volume flow rate and trans- membrane
pressure at the inlet,incereasing the length of a hollow
fiber L (or decresing the number of hollow fiber N) will
increase the fluid velocity in hollow fiber Ui. Furthermore,
since the increase of Ui have two con- flict effect: one
is the desirable effect of decreasing the resistance of gel
layer on the fiber wall which is is good for
ultrafiltration, and the other one is the un- desirable
effect of decreasing the transmembrane pressure which is bad
for ultrafiltration . Therefore , with total length of hollow
fiber ， there exists an optimum length L as well as optimum
number N of a hollow fiber for maximum permeate flux.
|