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8/7/2019 Intercat_Optimizing & Troubleshooting the FCC Re Generator for Reduced Emissions_RayFletcher_MartinEvans_CatCrackingCom_April2010
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www.intercatinc.com
O timizin & Troubleshootin
the FCC Regenerator for
Ray Fletcher & Martin EvansMarch 2010
5/3/20101
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Overview Introduction
Particulate emissions:
Catalyst attrition Cyclone integrity
Analysis & control
Gaseous emissions
Control of NOx emissions
Conclusion
www.intercatinc.com
NPRA Annual Meeting March 2010
2
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Introduction Substantial experience has been gained during
the last 68+ years related to FCC regenerator
operations
Effective troubleshooting is based upon a solid
set of baseline data taken during normal
operations
Selective use of additives will enable the refiner
to enhance the performance of the regenerator
Refer to reference section of associated paper
for key landmark papers related to regenerator
troubleshooting
www.intercatinc.com
NPRA Annual Meeting March 2010
3
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Overview Introduction
Particulate emissions:
Catalyst attrition Cyclone integrity
Analysis & control
Gaseous emissions
Control of NOx emissions
Conclusion
www.intercatinc.com
NPRA Annual Meeting March 2010
4
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Attrition in Regenerators Two primary sources of attrition:
Continuous & minor:
Particle attrition at grids
with back eddy
Submerged jet attrition at the grid
Attrition in cyclones
Attrition at load line elbows
Abnormal & substantial:
Improperly designed, eroded, or missing orifices in
steam lines
High turbulence caused by a broken air grid
High catalyst velocities through slide valves
Most units will have a low level of attrition
occurring continuously
Baseline essentialAir
www.intercatinc.com
NPRA Annual Meeting March 2010
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Attrition in FCC Regenerators Procedure for monitoring catalyst
attrition:
Capture & analyze fines samples regularly
3rdstage separator or 1ststage ESP bin
Plot wt% capture vs. PSD
Normal distribution:
One primary peak at 20-30
One attrition peak at 0-5
One breakage peak at 10-15
Attrition source present:
Primar eak shifted to lower article size
& reduced in magnitude
Attrition peak increases & dominates
www.intercatinc.com
NPRA Annual Meeting March 2010
6
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Cyclone Integrity Mechanically related problems:
Broken welds
Holes from erosion or high stress tears in
the cyclone or dipleg
Dipleg valves which do not operate
Dipleg valves which do not close because of
bent or lost closure plates
Operationally related issues Excessive mass flows in cyclones & diplegs
Insufficient dipleg length
www.intercatinc.com
NPRA Annual Meeting March 20107
5/3/2010
(Conceptual example)
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Dipleg Pressure Balance Knowledge of cyclone dipleg levels is critical
Minimum distance of catalyst level to cyclone
vortex is approximately 600 mm (24 inches)
Increases in charge rate can increase required
dipleg level beyond this minimum
Result: catalyst attrition, erosion in cyclone cones
& hoppers, entrainment
Higher catalyst levels occur in secondary
Plot cyclone dipleg heights vs. catalyst losses to
determine unit specific critical dipleg levelhdl
dl
Primary dipleg: 480 kg/m3 (30 lb/ft3)
Secondary dipleg: 320 kg/m3 (20 lb/ft3)3 3
bed
hbed
www.intercatinc.com
NPRA Annual Meeting March 20108
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Troubleshooting Cyclones Primary cyclone hole
A secondary peak is observed to the right of
the primary peak
Positioned at >60
The attrition & breakage peaks continue to
be present
www.intercatinc.com
NPRA Annual Meeting March 20109
5/3/2010
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Troubleshooting Cyclones Secondary cyclone hole
A secondary peak is observed to the right of
the primary peak
Positioned at 45-50
The attrition & breakage peaks disappear
Flooded cyclones
Primary peak shifts to the right of a typical
unit
The attrition & breakage peaks continue to
be present
www.intercatinc.com
NPRA Annual Meeting March 201010
5/3/2010
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Overview
Introduction
Particulate emissions:
Catalyst attrition Cyclone integrity
Analysis & control
Gaseous emissions
Control of NOx emissions
Conclusion
www.intercatinc.com
NPRA Annual Meeting March 201011
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Regenerator Afterburning
Afterburning is any increase in flue gas
temperature after leaving the dense bed
May occur in dilute phase, cyclones, or flue gas
Little catalyst present to absorb heat of combustion
May limit throughput or feedstock flexibility
May result in serious damage to internals leading
to premature shutdown & costly repairs
Two types of afterburn observed:
Kinetic limited afterburn
Due to insufficient regenerator bed residence time
for complete combustionSource: Jack Wilcox, RPS
er urn n uce y poor a r or ca a ysdistribution
Frequently due to inherent design features &/or air
rid mechanical failures
www.intercatinc.com
NPRA Annual Meeting March 201012
5/3/2010
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Kinetic Limited Afterburning
Characteristics:
Well dispersed afterburn across regenerator
cross section
High superficial velocities
Low bed levels
Low bed tempertures
Solutions:
Raise bed level
Increase bed temperatures
Add CO Promoter
Thermodynamically limited units generally
respond well to platinum
www.intercatinc.com
NPRA Annual Meeting March 201013
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Distribution Induced Afterburning
Characterized by localized afterburning
Induced b oor air &/or catal st distribution
O2 rich O2 richCO rich
Due to mixing of CO & O2 rich zones above bed Responds less well to CO Promoter
Monitor hotspot temp as Pt concentration increases
Hotspot temperature will drop until O2 is fully
consumed in effected region
Continued additions after temperature fails to drop O2 rich CO rich
NOx emissions will continue to increase
A normally well behaved unit which begins to
afterburn together with a change in losses or
equilibrium PSD indicates air grid damage
Suspected maldistribution may be confirmed
using a portable gas analyzer
www.intercatinc.com
NPRA Annual Meeting March 201014
5/3/2010
Source: J.W. Wilson, AM-03-44
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Gas Analyzer Verification
Portable gas analyzers are
effective at confirmingCL
Catalyst side-entry
#1
maldistribution
Typical equipment used:
Reaction Mix Sample (RMS)
330
probe
Mott filter element used to
remove catalyst fines from thegas s ream
P1
150190
Catalyst
withdrawalCJI
#2#3
www.intercatinc.com
NPRA Annual Meeting March 201015
5/3/2010
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Overview
Introduction
Particulate emissions:
Catalyst attrition Cyclone integrity
Analysis & control
Gaseous emissions
Control of NOx emissions
Conclusion
www.intercatinc.com
NPRA Annual Meeting March 201016
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Controlling SOx: Full Combustion
Feedstock effect
About 10% emitted as SOx (range: 5-35%)
Improve SOx additive efficiency: Drive SO2 to SO3 equilibrium towards SO3
Increase excess O u to ~2%
Reduce bed temperature
Increase regenerator pressure
Use Pt based CO promoter
Enhance additive regeneration
Increase cat circulation rate
Factors reducing additive efficiency:
High catalyst losses Large regenerator inventories
Poor stripper efficiencies
www.intercatinc.com
NPRA Annual Meeting March 201017
High Fe on equilibrium catalyst
5/3/2010
Total elimination of SOx emissions is achievable
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Controlling SOx: Partial Combustion
SOx additives in partial burn:
Majority of S in reduced form
Sulfur Species Data from European FCC @ 7% CO
COS, CS2,H2S
Oxidation of SSO2SO3 limiting step
Tailored oxidation component required
for maximum additive effectiveness
Measure SO2 is flue gas prior to using
additives in partial burn Approximately 30% of S in oxidized state
Partial burn guidelines:
There is a practical upper limit
Monitor SOxconcentration in flue gasupstream of CO Boiler thru trial
Monitor regenerator CO-to-CO2 ratio as
Deep SOx reductions in partial burn are feasible
www.intercatinc.com
NPRA Annual Meeting March 201018
5/3/2010
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Controlling NOx Emissions
NOx formation:
~10% of N in coke emitted as NOx 200)FluegasNOxvsExcessO2
Excess O2
is the most significant operating
variable affecting NOx emissions
Maldistribution of air & catalyst leads to 50
100
150
NOxEmissions(ppm
high NOx emissions
Additive efficiency is highly unit specific
NOx reducin additives are effective in
0.6 0.8 1.0 1.2 1.4
ExcessOxygen(ppm)
full combustion
There is an effective unit specific maximum
concentration
Exceeding this maximum will have no effector may actually increase NOx
www.intercatinc.com
NPRA Annual Meeting March 201019
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Designing for Low NOx Emissions
Control of air-to-catalyst mixing critical to
low NOx emissions
Combustor type regenerators with superior air-
to-catalyst mixing control NOx emissions well
Bubbling bed regenerators may be
improved for reduced emissions:
Ensure counter current operation
Distribute spent catalyst uniformly across the Courtesy: KBR
top of the regenerator bed
Inject combustion air uniformly across cross
section of regenerator
ves are e ec ve or ur er reductions as needed
www.intercatinc.com
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Troubleshooting NOx Emissions
Detecting maldistribution via comparison of cyclone delta temps
.
combination
Look for obvious pattern differences
Use regression analyses plus time plots identify likely root cause & timing
Perform step tests in unit to confirm suspected process variables
www.intercatinc.com
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CO Promotion & NOx Emissions
NOx emissions increase as platinum
content increases
Simultaneous control of afterburn & NOx
emissions is possible via non-Pt promoters
Fully commercialized solution
Utilize best available additive loader
technology for optimum performance
Reliable additive injection is essential
Intercat offers free loader usage for all its
customers
Example of enhanced additive
www.intercatinc.com
NPRA Annual Meeting March 201022
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reliability
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Overview
Introduction
Particulate emissions:
Catalyst attrition
Cyclone integrity
Analysis & control
Gaseous emissions
Control of NOx emissions
Conclusion
www.intercatinc.com
NPRA Annual Meeting March 201023
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Conclusion
Advanced troubleshooting techniques will
enable the process engineer to effectively
monitor, troubleshoot, & optimize the FCC
regenerator A solid base case taken during normal operations is
fundamental to swift troubleshooting
Intercat has developed a substantial base ofhands on regenerator troubleshooting &
optimization expertise
Refinery support available upon request
www.intercatinc.com
NPRA Annual Meeting March 2010245/3/2010
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www.intercatinc.com
O timizin & Troubleshootin
the FCC Regenerator for
Ray Fletcher & Martin Evans
March 2010
5/3/201025