Canadian Finishing and Coatings Manufacturing: Nov/Dec 2022 - 36

PLATING AND ANODIZING: FILTER SYSTEMS
temperatures (e.g. Ni Chloride at 60 degrees Celsius). Effective
sealing of disc plates is proven by a white impression left on spent
media near the eye and perimeter contact surfaces. Once the disc
pack is formed, lab samples for testing with particle counters
(Spectrometer) are useful but often side-stepped. Typical pH
levels of three to four can challenge chemical resistance of resin
bonded cellulous filter disc media while acid copper at a pH of
one will result in rapid degradation. More chemically resistant
polypropylene disc media allow for change-out intervals based
on organic breakdown levels as opposed to predicting filter media
resistance. However, not all forms of synthetic media have good
porosity at low micron retention levels (i.e. <5 µm absolute).
Considering the human eye can view down to 30-40 microns,
the release of broad spectrum D.E., powder carbon particles of <1
to 100 microns and potential media fibres, auxiliary filtration
can protect processes from these disruptive particulates.
Inclusion of suspended contaminants can lead to roughness on
the finished plate and ultimately costly rejections.
Considering the many variables in forming and maintaining a
proper disc pack, the addition of downstream or parallel polishing
filters should be considered to capture particulates at the source.
Polishing filters require adequate flow capacities with absolute
micron ratings.
Carbon Canister - Activated Granulated Carbon
Carbon canister filter units accommodate activated granulated
carbon, circumventing the more involved disc pack procedures.
Advanced grades of granular carbon have a complex range of
particulate sizing to optimize performance. Granular carbon
canister loading involves simpler set-up and verification
procedures, but the removal and disposal of spent carbon can be
laborious.
Granular carbon canisters utilize mesh filter media to
minimize the release of particulates. Therefore, second stage
polishing filters are required to retain the release of suspended
carbon particles.
Extruded Carbon Elements - Activated Granulated &
Powder Carbon
Recent advancements in forming elements or cartridges from
extruded, granulated and powder carbon ensures total contact
and minimizes the release of particulates. Optimal consistency
for coarser granular components is 30-35 per cent volume for a
support structure or " skeleton " , embedded with pathways and
25-30 per cent transport pores for flow, and 30-40 per cent of
adsorption pores to remove soluble organic contaminants. This
is somewhat analogous to the varying capacities and functions of
arteries, veins and capillaries in the body.
Self-contained carbon block elements circumvent more
labour-intensive carbon treatment methods and operational
procedures. Extruded carbon " block " cartridges are available in
D.O.E. and S.O.E. configurations in various diameters including
2.5-in., 4.5-in. and 6-in. Ø, and 10-in., 20-in., 30-in., and 40-in.
lengths. Carbon block filters can be equipped with an integral PP
melt-blown pre-filter layer. This feature preserves the carbon for
adsorption of soluble bath impurities rather than expending the
carbon matrix for filtering suspended contaminants.
Replacement of carbon block elements reduces exposure
of personnel to process chemicals and waste material, and
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Considering the human eye can
view down to 30-40 microns, the
release of broad spectrum D.E.,
powder carbon particles of
<1 to 100 microns
and potential media fibres,
auxiliary filtration can protect
processes from these disruptive
particulates.
minimizes the load on waste treatment, water usage and eventual
disposal costs.
Carbon Impregnated Cartridges & Disc Media
Carbon impregnated felt cartridges or discs contain minimal
carbon content. Example: 2.5-in. Ø x 10-in. L carbon cartridges
are impregnated with ¼ - 1 oz. est. (7-30 gm) of carbon. This is
suitable for low capacity, light carbon treatment applications.
An equivalent 2.5-in. Ø x 10-in. carbon block cartridge contains
0.7 lbs. (>300 gm). Media and the support structure used in felt
cartridges must withstand corrosive chemistries and elevated
temperatures to avoid discharge of debris.
Carbon Treatment Tanks
Surface area has a dramatic effect on carbon volume. Suspended
carbon in loose bed treatment systems requires excessive coarse
mesh carbon to avoid particle release. Finer mesh size carbon
used in formed carbon blocks contains 15X the surface area
increasing the kinetic activity and reducing contact time.
Loose Bed Contact Time/Empty Bed Contact Time (EBCT)
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Canadian Finishing and Coatings Manufacturing: Nov/Dec 2022

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