Hydrocarbon Processing - March 2022 - 42

Process Optimization
system. For hydroprocessing units, the
feed filter provides a sacrificial system
As a result, operators tend to default to
antiquated and/or undersized designs,
Upgrading the design of the filter system to the latest
technology represents a giant step forward in optimizing
refinery operations through proper catalyst protection
while minimizing total cost of filtration and improving on
predictable reactor performance.
that removes undesirable contaminants
that can cause reactor fouling. A welldesigned
feed filter system will prevent
problems in both hydrotreater and hydrocracker
applications by allowing the
reactors to reach full catalyst life and to
enter scheduled turnarounds as planned.
Although they are replaceable, filters
should be given serious consideration,
within the context of ensuring troublefree
refining operations, to optimize refining
margins and minimize downtime.
Unfortunately, this careful consideration
does not always occur, as feed filters
are often viewed as a " commodity. "
or they simply choose the lowest-cost
option. Because of the importance of
catalyst bed protection, a more comprehensive
view should be taken when determining
the selection of a filter.
Determining a properly sized filtration
system reflects a struggle between
capital and operational expenditures
(CAPEX/OPEX). CAPEX budgets may
call for smaller vessels, which can result in
poor performance and higher changeout
frequency. OPEX is better served by a filter
system sized on criteria that includes
inlet particle size distribution, suspended
solids concentration, higher filter surface
area, higher filter particle retention efficiencies
and total cost of ownership.
The economic relationship between
the filter and reactor.
To truly evaluate a superior value
in a filtration system, it should
be viewed as a component of the
larger refining process. Ideally, a
reactor goes into the scheduled
turnaround for catalyst reload every
3 yr to 7 yr, depending on the
unit. The reactor should reach
terminal differential pressure and
low-level activity simultaneously. However,
many refiners struggle with this and,
due to excessive differential pressure, are
forced to shut down operations prematurely.
The cause of this is poor feed filter
performance, which leads to reactor plugging
and inefficient reactions because of
contaminate loading from the process
feedstock. Signs of this include:
* Reaching catalyst bed differential
pressure prematurely
* Requiring scraping of the guard bed
* Restricted throughput
* Leaving the bypass line
open to help throughput
* Experiencing reactor hot
spots due to channeling.
In addition to poor conversion and
lower productivity, bed loading can cause
the formation of coke, which will ultimately
lead to an early catalyst reload. To
prevent this costly measure, it is critical
to have proper feed filters and to seek out
innovative solutions that enhance the
performance and longevity of the reactor.
In evaluating the economics for a feed
FIG. 2. Hydrocrackers are used for converting heavy feeds (such as vacuum gasoil) into
more valuable middle distillates. Depending on the crude slate and processing, there can
be an estimated 20% yield in light and heavy gasoline (sent to the reformer), along with the
same percentage in kerosene.
TABLE 1. Major refiner's spend on catalysts and chemicals
Catalysts/chemicals
Quantity
Gas/oil hydrodesulfurization
Hydrocracker
Naphtha hydrotreater
Kerosene hydrotreater
5.2 metric tpy
4.4 metric tpy
3.5 metric tpy
2 metric tpy
42 MARCH 2022 | HydrocarbonProcessing.com
filter system, the first thing to consider is
whether the catalyst bed is being protected.
While the catalyst is technically a variable
cost, it is easy to obtain the historical
expenditures at any given refinery. For example,
one major refiner's spend on catalysts
and chemicals is displayed in TABLE 1.
Outside of the one-time cost of the
Cost
$21.9 MM
$12.6 MM
$1.6 MM
$800,000
filter vessel, there are many things to consider
when evaluating the total cost of filtration.
These may vary greatly from one
application to the next, but the following
can typically be found to some degree in
any system:
* Costs of plant downtime, including
loss of production and equipment
replacement, if the right filtration
technology is not deployed
* Labor costs

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Hydrocarbon Processing - March 2022

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