Hydrocarbon Processing - March 2022 - 44

Process Optimization
* Vessel design that has an optimized
number and geometry of elements
to minimize wasted space
* Filter element design with an
optimum effective surface area.
ber diameters,
Recent innovations such as finer fihigher
media porosity
and greater gradient density have led to
important benefits, including lower pressure
loss, higher DHC, reduced particle
capture size and improved efficiencies.
However, the performance of traditional
cylindrical filters can only be pushed so
far. Much of this is due to the inherent
limitations of their physical shape. Traditional
cylindrical filters leave considerable
dead space in a filter vessel, particularly
when multiple filters are placed in a
housing. A trapezoidal design minimizes
the dead space and maximizes the effective
filter media surface area in a pressure
vessel (FIG. 3).
By minimizing dead space, trapezoidal
filters can provide up to 176% more
effective surface area than cylindrical filters,
depending on the configuration of
the filter (TABLE 2). This results in lower
pressure drops and longer online life.
The density of the trapezoidal configuration
also results in fewer filters to stock,
change out and dispose. Additionally, the
use of trapezoidal filters in place of cylindrical
elements has the potential to reduce
costs in areas such as shipping, storage
and changeout, thereby presenting
operating units with a significant overall
cost reduction.
Greater surface area equals longer
filter cartridge life. The increase
in surface area has a direct impact on
filter cartridge life. This is because a filter
cartridge's DHC is directly related to
the amount of usable surface area in the
cartridge itself. When the surface area is
increased, the corresponding decrease
in fluid flow per unit area drives up the
DHC. By doubling the surface area, a filter
system can increase filter life by up to
four times, as illustrated in Eq. 1:
Le = (Ae / Ao)n
(1)
where:
Le = Extended filter life
Ae = Extended surface area
Ao = Original surface area
n = The ability of the solid to form a
porous cake.
When various factors-cartridge life,
reliable catalyst bed performance and
uptime-are taken into consideration,
a clearer view of the importance of filter
selection begins to take shape. After several
months of successful operations, one
facility using the proprietary trapezoidal
filtersa
recorded measurable benefits in
several key areas, including an 84% increase
in effective surface area; a 400%-
500% increase in filter life; lower direct
consumable costs; fewer process upsets;
and reduced labor, shipping and disposal
costs.
Takeaway. For refiners that place a priority
on minimizing downtime, optimizing
performance, protecting the longevity of
catalyst reactors and minimizing the overall
lifecycle costs of their filtration systems,
upgrading the quality and construction of
the filter system represents a giant step
toward achieving these goals. Proper feed
filter filtration can prevent millions of dollars
in lost production, along with direct
losses related to material and labor costs.
An important step toward optimizing
performance for the industry is to include
ASTM F795-88 (1993) testing standards
to determine cartridge filter efficiency.
Furthermore, by requiring filter manufacturers
to adhere to a recommended sizing
specification of 0.5 gpm/ft2
flow per unit
FIG. 3. A proprietary trapezoidal-shaped cartridged filtera
area up to 169% vs. traditional cylindrical element designs (left).
(right) increases the usable surface
area of media or less, operators can put all
manufacturers on a level playing field and
evaluate products accordingly.
As a result, a more accurate measure
TABLE 2. Increased packing density and surface area of trapezoid-shaped elements
Vessel
Number of
diameter, in.
18
24
30
36
42
48
cylindrical 740
style elements
4
8
13
21
29
37
44 MARCH 2022 | HydrocarbonProcessing.com
Number of
trapezoidal filter
elements
6
11
19
30
38
50
Increase in
packing density, %
50
38
54
43
31
35
Increase in
surface area, %
Up to 176
Up to 153
Up to 169
Up to 163
Up to 141
Up to 148
of true lifecycle cost can be evaluated,
which incorporates the filter life (as determined
by DHC) and ancillary costs,
such as shipping, storage and changeout
times. Furthermore, migrating away from
existing cylindrical filters toward more
innovative solutions (such as trapezoidal
filters) can help operators significantly
improve both value and efficiency. This
will move them toward a new standard in
overall filtration system performance.
NOTE
a Filtration Technology Corp.'s Invicta® filter
http://www.HydrocarbonProcessing.com
Hydrocarbon Processing - March 2022

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