Chemical Engineering October 2021 - 52

CPI 2021 Special Advertising Section
Fast, homogenous mixing
The Bella XN fluidized zone mixer from Dynamic Air is a twin-shaft design that uses a
" weightless " central fluidized area to provide thorough yet gentle mixing of dry products
ing times of 15-30 s. A weightless
zone created by low-speed
counter-rotating paddles generates
low friction without
shear. This makes it ideal for
abrasive products and fragile
products that cannot tolerate
rough handling. Even flakes
or spray-dried bodies remain
intact.
The twin-shaft Bella mixer
T
he Bella fluidized-zone
twin-shaft paddle mixer
by Dynamic Air achieves fast,
high-capacity, low-shear, precision
mixing of either dry bulk
solids or liquids with solids.
Regardless of particle size,
shape or density, materials are
mixed with a fast, efficient, and
gentle action, with typical mixThe
Bella mixer consists
of twin drums which have
two counter-rotating agitators
with specifically angled
paddles. The paddles sweep
the entire bottom of both
mixer drums and yet allow
the mixer to be started under
full load (Figure 1). The material
in the mixer moves in a
Figure 1 (right, top): In
Zone A, fluidization promotes
thorough mixing. Figure 2
(right): Material interchange
between the two drums
ZONE A
ZONE B
horizontal counter-clockwise
direction at the perimeter
while simultaneously moving
both left and right in the center
(Figure 2). The material in
Zone B (Figure 1) is in its normal
gravimetric state as it is
being moved and dispersed.
In Zone A, a weightless zone is
created which effectively lifts
the ingredients to an almost
weightless state, allowing them
to move freely and randomly,
regardless of particle size and
density. Thus the two zones'
interaction becomes highly efficient
as every particle moves
rapidly to create a highly homogeneous
mix, the key to the
Bella mixer mixing technology
for fast, precise mixing.
The Bella mixer is available
in stainless steel and mild steel
construction.
www.dynamicair.com/
products/mixers.html
Protecting the vacuum system
Vacuum plays an essential role in chemical processes. Whether in vacuum conveying,
inertization, distilling, or drying processes, Busch Vacuum Solutions technology helps
make processes safer, faster, and more economical.
D
epending on the process gas, the vacuum pump can be exposed
to certain risks. It is therefore important that the process
gases are sufficiently known to minimize these risks. Different components
are often required, which can be installed on the inlet or
pressure side, to convey the process gas without damaging the vacuum
pump. This is called a vacuum system, which can also consist
of several vacuum pumps.
For the safe operation of the vacuum system, it is important to
protect it from corrosion and deposits caused by crystallization or
polymerization and to increase the material resistance. Various
measures can be effective in protecting the vacuum system or the
individual vacuum pumps against corrosion.
The first possibility is to prevent corrosive substances from entering
the interior of the vacuum pump. This can be implemented by
upstream condensers or gas scrubbers.
The second possibility to avoid corrosion is to keep the process
stream in the gas phase. In a screw vacuum pump, this can be implemented
by setting a certain operating temperature. In addition,
the process gas can be diluted by a supplied ballast gas to reduce
the partial pressure of the condensable gases. So, the following
simple logic applies - suction in gaseous form and ejection in gaseous
form. The minimum temperature must therefore be selected
so that it is high enough to prevent gases from condensing out. The
maximum temperature must be selected so that the vacuum pump
is not damaged or so that the maximum permissible temperature
according to ATEX classification is not exceeded.
52
A third
possibility
is to use
compatible
materials
for the vacuum
pump.
In COBRA
screw vacuum
pumps
from Busch
Vacuum
Solutions, for example,
all parts
in contact with the process are made of ductile cast iron by default
and have a special coating that is resistant to almost all chemicals.
For extreme cases, other coatings are available to provide additional
protection.
Dry screw vacuum pumps are ideal vacuum generators in processes
where the process gas to be conveyed should not come into
contact with an operating fluid inside the vacuum pump. This prevents
the process gas from contaminating or reacting with the operating
fluid. The elimination of operating fluids in the compression
chamber of the vacuum pump also eliminates the need to source
and process them or dispose of them - and the associated costs.
www.buschusa.com
Vacuum system with four screw
vacuum pumps as backing pumps.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
OCTOBER 2021

http://www.dynamicair.com/ http://www.buschusa.com http://WWW.CHEMENGONLINE.COM

Chemical Engineering October 2021

Table of Contents for the Digital Edition of Chemical Engineering October 2021