Chemical Engineering November 2012 - 9

Edited by Gerald Ondrey
November 2012
This filtration system saves
space, time and money
n the production of deionized (DI) water
from river water, sand filters are commonly
used to remove solid particles prior
to the ion-exchange units. However, sand
beds occupy a large space - as large as 3-m
wide and over 5-m high - and need to operate
with very low filtration speeds to ensure
the output has a solids content of less than
1 mg/L (1 ppm) to prevent fouling of the ionexchange
resins. Sand filters also have to be
cleaned periodically by backwashing with
large volumes of water (160 m3), which must
be performed off line for about 20 min, so
a second sand filter is required to operate
while the other is being cleaned.
An alternative system that reduces the
drawbacks of sand filters has been developed
by Lenzing Technik GmbH (Lenzing, Austria;
www.lenzing-technik.com). The OptiFil
filter uses a very fine (10 µm) filter media
(or even a metal-fiber fleece) on which a fine
layer of particles forms within seconds at
the beginning of the filtration cycle, thanks
to a patented design, says product manager
Stefan Strasser. This filter cake is periodically
cleaned by partial backwash (diagram),
which retains 95% of the filter area during
backwashing and thus enables uninterrupted
operation, Strasser says. Only 20-30
L of water is required for backwashing.
For DI applications, the investment costs
for an OptiFil filter are as little as one half
those needed for a sand filter, while operating
costs are about a third, says Strasser,
because the OptiFil requires less brackish
water (1% versus 8% for a sand filter),
consumes less air and is much less laborand
time-intensive for maintenance. Total
space and weight requirements for the
I
Feed
pump
Inlet
unfiltered
medium
Filtering
Outlet V2
Outlet
filtered medium
V7
Reject
P2
V3
V4
P1
V1
V6
Draining V5
∆P
Backwashing
Outlet
filtered medium
Outlet V2
V7
Reject
P2
Feed
pump
Inlet
unfiltered
medium
V3
V4
P1
V1
V6
Draining V5
∆P
OptiFil are also reduced by 95%, he says.
The first application of the OptiFil filter
for DI applications has been operating since
December 2011, in which the feed water's
solids concentration of 35-150 mg/L is reduced
to less than 0.5 mg/L. The system -
also available in the North American market
through W. Fritz Mezger Inc. (Spartanburg,
S.C.; www.mezgerinc.com) - is suitable for
both new installations and as a retrofit. For
this application, the system removes particles
as small as 5 µm (99%), 3 µm (80%) and
even 1 µm (35%), says the company.
A new catalyst enables lower-temperature
H2 production using the sulfur-iodine cycle
A
mong the many different ways being
investigated for making hydrogen
" from water " is the so-called sulfuriodine
(S-I) cycle, which involves three
chemical reactions whose net products
are H2 and O2: the decomposition of
sulfuric acid into SO2, H2O and O2;
the decomposition of hydrogen iodide
into H2 and I2; and the regeneration of
H2SO4 and HI by the Bunsen reaction
(I2 + SO2 + 2H2O → 2HI + H2SO4).
Note: For more information, circle the 3-digit number
on p. 60, or use the website designation.
Because the S-I cycle requires only
water and heat, it has the potential
for making H2 using solar energy as
the heat source.
One of the main drawbacks of the S-I
cycle (in addition to the use of corrosives
materials) is the high temperature
(900°C) required for the decomposition
of H2SO4 - the most energy-intensive
step. Up to now, only expensive platinum-based
catalysts have been develWater
treatment
The recently introduced FoodPro
ST line of water-treatment
chemicals from GE Power &
Water (Trevose, Pa.; www.
ge.com) prevents corrosion
and scale in stainless-steel
sterilizers and pasteurizers in
the food and beverage industry,
and they are less expensive
than alternatives because
they contain no molybdate.
When calculated on the costs
to treat 1 m3 of water, FoodPro
ST chemicals are 30% more
(Continues on p. 10)
oped to lower the temperatures required
for this step in the cycle.
A new catalyst - a macroporoussupported
Cu-V oxide - has been developed
by professor Masato Machida
at Kumamoto University (Kumamoto;
www.chem.kumamoto-u.ac.jp/~lab0/
machida), in collaboration with Toyota
Motor Corp. (Toyota; Tokyo, both Japan),
(Continues on p. 13)
CHEMICAL ENGINEERING WWW.CHE.COM NOVEMBER 2012 9
Filter material
V8
P3
Motor
M
Outlet
filtered
medium
Filter material
V8
P3
Motor
M
Outlet
filtered
medium
http://www.lenzing-technik.com http://www.ge.com http://www.mezgerinc.com http://www.chem.kumamoto-u.ac.jp/~lab0/ http://WWW.CHE.COM
Chemical Engineering November 2012

Table of Contents for the Digital Edition of Chemical Engineering November 2012
