12
Chemical Technology • September 2013
separation/filtration technologies
D
epending on the specific application, the GEA
Westfalia Separator Group provides a wide
range of membrane types under the brand of
the established membrane manufacturer, Membraflow.
This comprises the delivery of ceramic filter elements,
the modules and the accessories which, as is standard
practice in the industry, can be configured by engineer-
ing companies to meet the specific needs of the users.
Ceramic membranes versus polymer
membranes
Ceramic membranes offer many advantages in in-
dustrial applications: they have long service lives, are
absolutely chemically inert, heat-resistant, pressure-
shock-resistant, can always be cleaned and are thus
sustainable.
A direct comparison between ceramic membranes
and polymer membranes demonstrates the advantages
and disadvantages: ceramic membranes are able to
withstand high temperatures of up to 120°C; they can
thus be sterilized, and are also resistant in the entire
pH range of 0 to 14, making them suitable for stan-
dard caustic soda or nitric acid to be used as cleaning
agents. The cleaning process lasts for 1,5 to 2 hours.
On the other hand, polymer membranes can only
be used in a limited temperature range of between
approximately 55°C and maximum 80°C; they cannot
therefore be sterilized, and can only be used within a
pH range of 1,8 to 10,8. This means that expensive
special cleaning agents are necessary, extending the
duration of the cleaning process to 2,5 to 3 hours.
Moreover, backflushing is possible with ceramic mem-
branes, but it is only possible to a limited extent with
polymer membranes.
Flexible configuration:
Membraflow ceramic membrane elements
by Wolf-Dietrich Herberg, Head of Membraflow/Technology Manager: Business Line Beverage Technology, GEA Westfalia
Separator Group, Oelde, Germany
In cross-flow filtration, ceramic membranes from the GEA Westfalia Separator
Group enable the solids to be concentrated to such an extent that no further
processing is necessary. This results in extremely efficient filtration methods
in the application areas of beverage and dairy technology, for renewable
resources, in the chemical and pharmaceutical industries and also in mineral
processing.
With ceramic membranes, high solid dry matter
levels with constantly high flux rates of the filtrate can
be attained throughout the entire life cycle. With poly-
mer membranes, the flux rates decline over the life of
the membrane. Ceramic membranes are used almost
exclusively for concentration tasks such as recovering
beer from excess yeast. Ceramic membranes have a
service life of more than ten years, whereas polymer
membranes have a service life of only one to three
years. They are also vulnerable to pressure peaks,
whereas ceramic membranes are mechanically highly
stable.
Ceramic membranes are therefore a longer-term
solution, and offer a free choice of the most favour-
able pore size for an optimum result. There is no
adsorption of valuable (colour) components; for
instance, there is virtually no colour adsorption in the
case of bright juices. They are resistant to bentonite
and activated carbon in a limited concentration. Pre-
assembly of the membranes permits rapid installation
and commissioning on site; overall therefore, ceramic
membranes have a lower total cost of ownership than
polymer membranes.
Higher filtration volumes
Membrane filtration is typically a cross-flow filtration
process, and differs in major respects from dead-end
filtration, where solids and filtrate flow in one direction
and the particles are retained on the surface of the
filter or in the interior of the filter. In dead-end filtra-
tion, this filter cake increasingly restricts the flow in
the course of the filtration process.
On the other hand, in the case of cross-flow filtra-
tion, the retentate flows at a tangent to the filter sur-
This article
was originally
published in
the ‘Separator's
Digest’
2012/5, and
is republished
here with kind
permission.
