Chemical Engineering September 2014 - 72

Water Management Special Advertising Section
Polypropylene makes the difference
GEA BIOdek trickling filter media made from polypropylene are stronger and more
environment-friendly than their PVC equivalents
to grow. Sufficient air circulation is necessary to provide the required
oxygen. The biofilm should have the appropriate thickness,
and the water should flow through slowly and evenly. The result is
a balanced three-phase system in which water, air, and biosolids
share the void space within the fill medium.
Achieving this balance is a challenge for the design engineer.
BIOdek fills from GEA Heat Exchangers are available in a selection
of media types to accommodate the process requirements with
any desired type of flow pattern and a variety of channel sizes.
As well as meeting the process requirements, the medium
Tough stuff: Trickling filter media made from polypropylene
need no protective grating to prevent damage during inspection
T
rickling filter media made of polypropylene (PP) have gained
growing acceptance in recent decades, notes GEA Heat
Exchangers, because they have valuable features that make them
attractive substitutes for commonly used PVC fills.
Simple though plastic trickling filter media might appear, they
have to meet many criteria if the biological treatment process is to
be successful. They should provide a large surface for the biofilm
must be self-supporting and rigid enough to withstand the weight
of the biofilm and captured water. It must retain its shape for decades,
and must be environment-friendly in manufacture and disposal.
Here PP has several advantages over PVC:
* PP is less brittle than PVC, so during inspections an operator
can walk on top of a PP bed without damaging it. PVC filters require
a separate PVC grating to prevent breakage.
* PP is less dense than PVC, so PP sheets are much thicker than
PVC sheets of the same weight. This provides greater resistance
to erosion and media buckling, which is the most common cause
of failure when a filter collapses.
* GEA BIOdek PP media are thermo-welded, eliminating the solvent
emissions associated with manufacturing PVC products.
* PP media can be recycled at the end of their working lives.
www.gea-heatexchangers.com
Plastic control valves handle corrosive chemicals
Collins 2-in. valves and actuators are specially designed to handle corrosive fluids -
acids, bleaches, chlorine, pH control - and aggressive environments
C
ollins Instrument Company's line of
economical 2-in. flanged plastic control
valves handle corrosive liquids including
hydrochloric acid, caustic, sulfuric acid,
and many others. With bodies of either
PVDF or polypropylene, these highly-responsive
control valves are specifically designed
for use with corrosive media and/or
corrosive atmospheres.
Suitable for applications in numerous
industries, including chemical, petrochemical,
pulp and paper, and municipal, these
valves are extremely corrosion-resistant,
and feature fast-acting positioning (stroke
rate approximately 1⁄2 in./s). They are available
with a wide selection of trim sizes, in
globe, angle, and corner configurations.
The differential-area piston eliminates
the necessity for auxiliary loading regulators.
All actuator parts apart from the integral
positioner are molded of glass-filled,
UV-inhibited polypropylene. Before shipment,
the aluminum positioner and a portion
of the cylinder are immersed in Dip
Seal to provide atmospheric protection.
Plastic valves and actuators from Collins
The integral positioner eliminates the need
for external linkages which are subject to
corrosion and malfunctioning. Valves may
also be furnished without a positioner for
on/off applications.
Collins also offers a plastic pneumatic
actuator. The combination of a plastic actuator
and a plastic valve body provides
an effective way to handle both corrosive
materials flowing through the valve, and
harsh environments that can attack the
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outside of the valve and actuator. Collins
plastic control valve packages withstand
salty marine atmospheres as well as industrial
environments that are too corrosive
for metal valves and actuators.
Collins actuators incorporate a unique
internal locking ring to attach the cylinder
to the yoke. A semicircular groove is
machined inside the lower edge of the cylinder,
and a matching groove cut in the
yoke. When the yoke and cylinder are assembled,
a flexible polypropylene rod is
inserted into the groove through a slot in
the side of the cylinder, securing the two
sections together.
Along with its corrosion resistance the
Collins control valve features a stem packing
arrangement that virtually eliminates
the problem of fugitive emissions, thereby
protecting the environment.
Located on the Texas Gulf Coast in
the town of Angleton, Collins Instrument
Company has been serving the chemical
and petrochemical industry for over
65 years.
www.collinsinst.com
http://www.gea-heatexchangers.com http://www.collinsinst.com
Chemical Engineering September 2014

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