A MODEL SIMULATION OF THE FILTERING PROCESS
IN MULTICHANNEL CERAMIC MEMBRANES
G. G. Kagramanov,
Yu. I. Dytnerskii,
and P. G. Il’in
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 4, pp. 5 – 12, April, 2001.
The filtering process in ceramic membranes is analyzed by jointly solving Darcy and Laplace equations and
an equation for continuous flow of an incompressible fluid to determine the pressure and velocity profiles over
the cross section of a membrane cell. Computational and experimental data for multichannel ceramic mem
branes how that the filtering efficiency of the channels decreases from the center to the periphery depending
on the pore size and on the thickness of both the selective layer and the substrate.
At present, production of ceramic membranes for micro-
and ultrafiltration and also instrumentation and equipment
for separation processes using these membranes are expand-
ing continuously. Ceramic membranes when compared with
polymer membranes exhibit a number of advantages, which
allows their use for specific technologies; in a sense, the for-
mer serve to complement, rather than replace, the latter .
The main advantages of ceramic membranes are:
thermal stability, which allows filtration to be carried out
at high temperatures;
high mechanical strength, which allows the use of unsup
ported (free-standing) membranes at high pressure drops and
use of the backwash for membrane regeneration during fil
tration; furthermore, ceramic membranes are distinguished
for high erosion resistance;
chemical resistance. Certain types of ceramic membra
nes are capable of operating in the entire pH range; owing to
this property, their service life in corrosive media can extend
to five years or even more;
stability (inertness) to microbial attack;
the possibility of designing membranes with custom-tai
lored and controlled properties. By way of example, ceramic
membranes may possess catalytic, hydrophilic, and hydropho
bic properties, or they may develop a variable surface charge.
A serious drawback of ceramic membranes is their high
cost. Still, allowing for their extended (severalfold) service
life vis-a-vis polymer membranes, it becomes clear that the
competitiveness of ceramic membranes remains high. One
will note also that the area of application of ceramic mem-
branes shows an ever-growing tendency to expand.
The ceramic membrane consists of a coarse-dispersed
substrate and a finely dispersed thin selective layer.
To improve the regenerative ability and extend the ser-
vice life of membranes, they are designed as a three-layer
structure in which the coarse-dispersed substrate is underlain
with a high-quality intermediate layer (“sublayer”), which al
lows one to prepare the upper filtering layer with the smallest
possible pores [2, 3].
The requirements placed on ceramic membranes are
rather demanding. Depending on the operating conditions,
ceramic membranes should have an open porosity of
30 – 60% (not infrequently with a tailored pore size), high
mechanical strength, high thermal and chemical resistance,
serviceability at low and high temperatures, etc.
To increase the productivity of filtering units and to save
their working space, the conventional single-channel filter
cells designed as cylindrical tubes (Fig. 1a ) are replaced by
multichannel ceramic cells. Of these, 7- and 19-channel cells
which are cylinders or hexagonal ceramic prisms with axi
ally directed channels for the filtered fluid (Fig. 1b and c)
have become widespread. The thin selective layer (mem
brane layer) in single-channel ceramic cells can be supported
on either the outer or inner surface of the tubular substrate,
whereas in multichannel cells — only on the inner channel’s
Therefore, a numerical technique by which one can esti
mate the performance efficiency of each individual channel
Refractories and Industrial Ceramics Vol. 42, Nos.3–4, 2001
1083-4877/01/0304-0139$25.00 © 2001 Plenum Publishing Corporation
D. I. Mendeleev University of Chemical Engineering, Moscow,
Russia; Gelios Joint-Stock Company, Moscow, Russia.