Hydrocarbon Processing - August 2022 - 36

Catalysts
the screen. This was predictable, as the
screen was designed to capture the material
and the air cannons were intended to
sweep the buildup off the screen face and
into the collection zone. However, even
with the buildup on portions of the screen
face, the distance between the screen and
the catalyst was great enough so that the
gas distribution recovered, resulting in
significantly improved SCR performance.
Since the air cannons were misused,
FIG. 2. Catalyst flow profile before and after screen installation.
the buildup on the screen face eventually
did reach the catalyst face. Once discovered,
the air cannons on the screen were
cycled and effectively broke apart the
particles on the screen, allowing them to
pass through the SCR without causing
additional buildup. The particles were
visibly seen coming out of the stack, and
no pressure drop increase was experienced
across the SCR, confirming the
successful air cannon cleaning.
The air cannons were not operated
regularly to eliminate the risk of material
passing through the screen. After 2 yr, it
was decided to install a finer pitch secondary
screen. The secondary screen eliminated
all particle buildup on the catalyst.
Results. FIG. 4 shows the catalyst face
while the unit was online after more than
1 yr of run time, and indicates almost no
buildup on the SCR itself; the NOx
reFIG.
3. Completed installation of the filtration
screens in a methane reformer.
Turnaround impact. Due to the standardized
modular design, the author's
company's mechanical division can install
SCR screens, air cannons and access doors
in less than a working week of critical path
time. In this referenced case, all the work
was performed within the time window of
the preplanned outage and caused no impact
to the turnaround schedule (FIG. 3).
Prior to the screen installation, the
typical startup sequence required utilizing
a cheese cloth to capture particles
that break free during startup. The new
inline screen system eliminated the need
for the cheese cloth by capturing all particles
that were too large to pass through
the catalyst. This practice was critical before
the screen installation because the
36 AUGUST 2022 | HydrocarbonProcessing.com
FIG. 4. Catalyst face taken while the unit
is online.
work performed during the outage resulted
in dislodging particles larger than
the catalyst opening. This process delayed
complete startup by roughly a day.
Because of the installation of the screen,
this cheese cloth startup process can be
eliminated, saving approximately $1 MM
during each outage.
Operating assessment. Initially, the
Texas plant did not experience any significant
pressure drop increase across the
catalyst, which was a significant improvement.
Before the screen installation, the
catalyst required frequent manual cleaning
at a significant cost. Initially, the plant
opted not to utilize the air cannon system,
which eventually caused buildup across
duction numbers remain constant. Due
to the infrequent firing of the air cannons,
the secondary screen does experience
some minor accumulation. However,
data indicate this does not impact NOx
removal or SCR performance.
This elimination of buildup and pressure
drop eliminated the need for the
plant to run at a reduced output, the ID
fan is running per design, NOx
reduction
of the process gas is optimal and the catalyst
life has increased. After recognizing
this success, the plant has purchased a second
screen system for its sister plant.
NOTES
a IGS' NoNOx Reformer Screens
ANDREW KLINE is the Business
Development Director for the
IGS Environmental Services group
and specializes in SCR efficiencies
in emissions control applications.
He has more than 8 yr of
experience with improvements
in SCR applications, ranging from product
development to engineering. Mr. Kline graduated
with honors from the Virginia Commonwealth
University School of Engineering.
http://www.HydrocarbonProcessing.com
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