Hydrocarbon Processing - January 2022 - 74

Heat Transfer
TABLE 1. Four potential solutions
Change existing
burner layout
Flame interaction
Simplify operation
Eliminate ambient eff ects
Increase fuel effi ciency
Reduce fouling
Increase capacity
Reduce emissions
CAPEX
OPEX
Implementation time
+
++
+
+
-
-
Convection replacement
++
++
++
+
--
+++
--
FDAPH burners
* Air distribution inside the new
combustion air duct
* APH bypass duct design to prevent
acid dewpoint corrosion.
To mitigate the impact on NOx
and
ensure the best possible flame performance,
an innovative companya
designed
the burners. They selected a proprietary
round flame burnerb
for its compact design
and its ability to produce very low
NOx
FIG. 8. Flames after revamp.
avoidance, the project showed a payback
period of less than 2 yr. Most importantly,
this option allowed for the highest
capacity increase (29%). One benefit
of this option was that a substantial
portion of the work could be done with
the heater in operation, reducing downtime.
An overview of the revamp scope
is shown in FIG. 4.
Potential problem analysis. A drastic
modification like this can result in unforeseen
issues. Importantly, during the
change of the combustion system and air
supply, potential issues include:
* Flame shape, flame interactions,
NOx
emissions, incident radiant
flux profile, and temperature
uniformity using five high-capacity
74 JANUARY 2022 | HydrocarbonProcessing.com
Results. The turnkey project was successfully
executed within 7 mos from
profile requirements for this project for
a wide fuel composition ranging from
natural gas to liquefied petroleum gas
(LPG). Despite the much higher heat
release and air temperature, the burnerb
fit in the existing openings of the ND
burner, so no floor modifications were
necessary. A CFD model of the new arrangement
(FIG. 5) demonstrated that
flame impingement would be eliminated
with the proposed arrangement while
meeting NOx
requirements.
On the execution side, a risk that
required mitigation was the potential
interference of the large APH structure
with the existing equipment. The heater
and its surrounding area were scanned
using lasers, which produced a 3D model
that was imported into the author's
company's model. During construction,
the distance between the new and existing
equipment was as small as 0.5 in.
Thanks to the laser scan technology and
3D modeling (FIG. 6), zero field interferences
or fit-up issues were experienced.
NOTES
a Broken Arrow-based company, Zeeco
b GLSF FREE JET round flame burner
ERWIN PLATVOET is the CTO of
XRG Technologies, and has served
the industry around the globe
in a variety of roles, including
R&D Engineer, Cracking Furnace
Specialist, Director of Engineering,
and now Chief Technology Officer
of XRG Technologies. He holds eight patents in fired
heat transfer and emissions control technologies,
has published numerous papers, and co-authored
the John Zink Combustion Handbook and Industrial
Combustion Testing book. Mr. Platvoet has been
an active member of the API 560 and API 535
subcommittees, and is a graduate of Twente
University in the Netherlands with an MS degree
in chemical engineering.
emissions while meeting the flux
FD APH
+++
++
+++
+++
+++
+++
+
---
++
-
Do nothing
---
-
-
placement of purchase order to startup.
By following a structured decision methodology
like the Kepner-Tregoe Matrix,
the optimal solution was selected considering
CAPEX, OPEX, process availability,
reliability and plant throughput.
Integration of smart tools like CFD and
3D modeling in every facet of the design
process prevents mistakes and rework
while ensuring the project goals are met
(FIG. 7). The burnersb
produce well-behaved
flames without visible interactions
(FIG. 8). Due to the solid improvement in
heat flux uniformity, the coil outlet temperatures
are now within a narrow band.
The fuel efficiency and capacity goals
were met while peak skin temperatures
at SOR were 100°C lower than before
the revamp. The predicted NOx
emissions
from the CFD model were validated
with official stack measurements,
which showed that the actual emissions
were 30% below the required limits.
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