Understanding the Software Options

Edited by Gerald Ondrey August 2011
Three-mechanism grinding mill achieves finer, more uniform particles
newly introduced cryogenic grinding
A mill from Air Products and Chemicals
Inc. (Allentown, Pa.; www.airproducts.com/
ultrafine) can generate consistent yields of
particles between 45 and 250 µm, and in
some applications can achieve particle sizes
of 10 µm. The ultrafine grinding mill also
achieves narrower particle size distributions
than conventional impact mills.
Known as the PolarFit ultrafine-grinding
mill (diagram), the cryogenic grinder
employs a combination of size-reduction
strategies — impact, particle attrition and
particle-particle collisions — in one machine
to reach finer particle sizes and raise yields
within a particular size range. “We set out
to design a highly flexible machine,” says
technology manager Jon Trembley, “and one
that both lowers energy input and makes
efficient use of liquid nitrogen” (to remove
heat generated by the grinding process).
The PolarFit mill has an easily adjustable
grinding gap, and is intended for low-maintenance
operation.
Before being launched at last month’s PTX
Canada tradeshow in Toronto, the PolarFit
mill had undergone an internal analysis
A promising new forward-osmosis membrane
Forward osmosis (FO) has been recognized
as a valuable technology for many applications
including wastewater reclamation,
seawater desalination, and energy production,
due to the low energy input required.
The osmotic pressure gradient across a
semipermeable FO membrane causes water
to diffuse naturally through the membrane,
leaving impurities behind. However, when
water diffuses through the selective layer
of the FO membrane, the draw solution
at the permeate side is substantially diluted,
while the back diffusion of draw solutes
through the support layer works to
compensate the diluted draw solutes. The
compensation process is severely hindered
by the tortuous, dense and thick support
layers of conventional FO membranes. As
a result, the competing process between
dilution and back diffusion equilibrates
at a transverse draw-solute concentration
profile, leading to an internal concentration
polarization (ICP) problem.
To overcome this problem, researchers
Note: For more information, circle the 3-digit number
on p. 54, or use the website designation.
Granulated
feed
Cooling conveyor
Control console
program, processing 2–3 tons of material at
a time while being compared to competing
products. The product performed well for
various cryogenic size-reduction applications,
including plastics, pigments, powder
coatings, thermoplastic elastomers, spices
and other food products. The PolarFit mill is
available with grinding rotors in three standard
sizes — 200, 400 and 800 mm, as well
as in custom-made sizes.
from the School of Civil and Environmental
Engineering, Nanyang Technological University
(Singapore; www.ntu.edu.sg) fabricated
a novel nanocomposite FO membrane
with a scaffold-like nanofiber layer that, the
researchers claim, possesses remarkable advantages
over conventional sponge-like support
layers, such as low “tortuosity”, high porosity
and extreme thinness. This structure
guarantees direct paths for salt and water
diffusion, which could also eliminate the
ICP bottleneck, the researchers say.
An electrospinning technique is used to
fabricate the membrane. A rotating drum
is employed to fabricate a large-area polyethersulfone
nanofiber support on a nonwoven
fabric, where the diameters of the
nanofibers are in the range 50 to 150 nm.
The thickness of the support layer can be
adjusted by controlling the electrospinning
time. The water permeability of the new
nanocomposite membrane was observed
to be about 3.5 times higher than that of a
commercial FO membrane.
Grinding
mill
Powdered product
Liquid
nitrogen
tank
Graphene from dry ice
Researchers at Northern Illinois
University (NIU; DeKalb,
Ill.; www.niu.edu) discovered a
new method for producing graphene
that involves burning
pure magnesium metal in dry
ice. The method, which is capable
of producing large quantities
of graphene in sheets
less than ten atoms thick, is
simpler than conventional
methods for generating graphene,
and avoids hazardous
chemicals. The NIU scientists
knew that burning Mg metal
in carbon dioxide produced
carbon, but the structure of
the resulting carbon had not
been studied carefully before,
says NIU researcher Amartya
Chakrabarti. Graphene, twodimensional
carbon arranged
in hexagonal lattice, has
been the focus of extensive
research because of its electrical
and mechanical properties.
A new thermophile
Scientists from the University
of Calif., Berkeley (UCB; www.
berkeley.edu) and the University
of Maryland School of
Medicine have discovered a
microbe in a Nevada hot spring
that metabolizes cellulose at
a record-high temperature of
109°C. The hyperthermophil-
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CHEMICAL ENGINEERING WWW.CHE.COM AUGUST 2011 9