1. Techniques For Troubleshooting FCC Regenerator Problems

2. CONFIDENTIAL BUSINESS INFORMATION
Overview
Introduction
Particulate Emissions:
CPFD Modeling
Catalyst attrition
Cyclone integrity
SEM analysis
Afterburn Control
Analysis & control
Gaseous Emissions Control
Control of SOx emissions
Control of NOx emissions
Conclusion
CONFIDENTIAL BUSINESS INFORMATION

3. Introduction
There has been substantial experience gained in troubleshooting FCC regenerator operations during the last 68+ years
Many important lessons learned – one of the most important is that:
Effective troubleshooting requires a solid set of baseline data taken during normal operations
Selective use of additives can also help enhance the performance of the regenerator
Refer to reference section of associated paper for key landmark papers related to regenerator troubleshooting

4. CONFIDENTIAL BUSINESS INFORMATION
Overview
Introduction
Particulate Emissions:
CPFD Modelling
Catalyst attrition
Cyclone integrity
SEM analysis
Afterburn Control
Analysis & control
Gaseous Emissions Control
Control of SOx emissions
Control of NOx emissions
Conclusion
CONFIDENTIAL BUSINESS INFORMATION

5. Particle Fluid Dynamics
One of the most interesting tools to become available in recent years is CPFD Modeling
Computational Particle Fluid Dynamics
Extremely computer intensive, has only very recently become a practical tool
Using a very simple set of boundary conditions, these models can provide a whole new level of understanding of regenerator operations
INTERCAT is grateful to Barracuda
for the following simulation

6. Particle Fluid Dynamics
Simulation is of a Model II Regenerator
Spent Catalyst enters through the bottom nozzle
Baffle plate above the catalyst inlet to deflect catalyst into the dense bed
Three combustion air rings
Single regenerated catalyst standpipe
12 pairs of cyclones

7. Particle Fluid Dynamics
In this flowing simulation colour is used to represent catalyst density
Simulation revealed several interesting features:
Catalyst entering regen is concentrated on outside bend of pipe
Deflector plate was ineffective at keeping catalyst in the bed
Much of the incoming catalyst bypasses the bed and enters the dilute phase directly
Bed is very unstable, with no clear level
Red area below air rings shows a large dead zone of defluidized catalyst

8. Particle Fluid Dynamics
In this flowing simulation colour is used to represent catalyst density
Simulation revealed several interesting features:
Catalyst entering regen is concentrated on outside bend of pipe
Deflector plate was ineffective at keeping catalyst in the bed
Much of the incoming catalyst bypasses the bed and enters the dilute phase directly
Bed is very unstable, with no clear level
Red area below air rings shows a large dead zone of defluidized catalyst

9. Particle Fluid Dynamics
This view shows only catalyst that has been in the regenerator for less than 30 seconds
Note large amount of unregenerated catalyst making its way to the very top of the dilute phase

10. Particle Fluid Dynamics
This view shows only catalyst that has been in the regenerator for less than 30 seconds
Note large amount of unregenerated catalyst making its way to the very top of the dilute phase

11. Particle Fluid Dynamics
Close in view of bed shows catalyst from primary cyclone dipleg bypassing the bed, and directly entering the standpipe
Explains “salt and pepper” appearance of ECat

12. Particle Fluid Dynamics
Close in view of bed shows catalyst from primary cyclone dipleg bypassing the bed, and directly entering the standpipe
Explains “salt and pepper” appearance of ECat

13. Particle Fluid Dynamics
This view was generated to assess likely areas of erosion
Green areas show time averaged areas of high velocity and high catalyst density
This simulation was carried out before the unit was shut down
When unit was opened up, wear was found to be in exactly the areas predicted by the CPFD simulation

14. Particle Fluid Dynamics
This close match gave confidence in the model predictions
Model could then be used to design a new deflector plate & internal configuration
New design was implemented, and unit operation has been very stable since startup

15. Attrition in Regenerators
Particle attrition at grids
with back eddy
Air
All units have a low level of attrition occurring continuously
Submerged jet attrition at the grid
Attrition in cyclones
Abnormal Attrition can be substantial
Improperly designed, eroded, or missing orifices in steam lines
Excessive velocities through air grid
High turbulence caused by a broken air grid
High catalyst velocities through slide valves
Developing a good normal operating baseline is strongly recommended in order to prepare for troubleshooting any future loss problems

16. Attrition in Regenerators
How Can We Check Catalyst Attrition Rates?
Capture & analyze fines samples regularly
3rd stage separator or isokinetic sample
Need to request detailed PSD analysis
Plot wt% capture vs. PSD
Normal Distribution:
One primary peak at μ
One attrition peak at 0-5 μ
One “breakage” peak at μ
If Attrition Source Present:
Primary peak shifted to lower particle size & reduced in magnitude
Attrition peak increases & dominates

17. 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
Note that PSD of catalyst is different at each point – this is key to effective troubleshooting
(Conceptual example)

18. Troubleshooting Cyclones
Primary cyclone hole
A secondary peak is observed to the right of the primary peak
Positioned at >60 μ
The attrition & breakage peaks continue to be present

19. Troubleshooting Cyclones
Secondary cyclone hole
A secondary peak is observed to the right of the primary peak
Positioned at μ
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

20. Dipleg Pressure Balance
Knowledge of cyclone dipleg levels can be very important
Too high a dipleg level will cause catalyst entrainment
Minimum distance of catalyst level to cyclone vortex is approximately 600 mm (24 inches)
Increases in unit feed rate can increase required dipleg level beyond this minimum
Result: catalyst attrition, erosion in cyclone cones & hoppers, entrainment
Higher catalyst levels occur in secondary cyclones lead to entrainment losses
Plot cyclone dipleg heights vs. catalyst losses to determine unit specific critical dipleg level
ρbed
hbed
hdl
ρdl

21. Attrition vs. Fresh Cat Losses
Filter paper
When losses increase, the first response is normally to ask if they due soft fresh catalyst
If losses are from fresh catalyst:
Fines surface area > ECat
Fines metal levels < ECat
If attrition source/hole:
Fines surface area = ECat
Fines metal levels = Ecat
SEM check:
Acquire ESP, stack fines, etc.
Analyze particle morphology
Base line critical
SEM image

22. SEM Fines Analysis Typical FCC fines Attrition fines
Note: well rounded equilibrium particles
Attrition fragments will vary by unit
Base lining normal operations critical
Particle size 1-3 µ
Magnification = 10,000X
5 µ
Attrition fines
Primarily sharp irregular morphology
Particle size 1-2 µ
Magnification = 2,500X
20 µ

23. CONFIDENTIAL BUSINESS INFORMATION
Overview
Introduction
Particulate Emissions:
CPFD Modeling
Catalyst attrition
Cyclone integrity
SEM analysis
Afterburn Control
Analysis & control
Gaseous Emissions Control
Control of SOx emissions
Control of NOx emissions
Conclusion
CONFIDENTIAL BUSINESS INFORMATION

24. 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
Can result in serious damage to internals leading to premature shutdown & costly repairs
Two types of afterburn observed:
Kinetically limited afterburn
Due to insufficient regenerator bed residence time for complete combustion
Afterburn induced by poor catalyst and/or air distribution
Frequently due to inherent design features &/or air grid mechanical failures
Source: Jack Wilcox, RPS

25. Kinetic Limited Afterburning
Characteristics:
Well dispersed afterburn across regenerator cross section
Commonly seen when there are:
High superficial velocities
Low bed levels
Low bed temperatures
Solutions:
Consider raising bed level
Use of CO Promoter
Kinetically limited units generally respond well to CO Promoter use

26. Distribution Induced Afterburn
Characterized by localized afterburning
Induced by poor air &/or catalyst distribution
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 has little effect on regionalized afterburn
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
Maldistribution may be confirmed using a portable gas analyzer
O2 rich
CO rich
O2 rich
CO rich
Source: J.W. Wilson, AM-03-44

27. Gas Analyzer Verification
Portable gas analyzers are effective at confirming maldistribution
Typical equipment used:
Reaction Mix Sample (RMS) probe
Mott filter element used to remove catalyst fines from the gas stream
Spent cat entry #1
Catalyst withdrawal #2 #3

28. CONFIDENTIAL BUSINESS INFORMATION
Overview
Introduction
Particulate Emissions:
CPFD Modeling
Catalyst attrition
Cyclone integrity
SEM analysis
Afterburn Control
Analysis & control
Gaseous Emissions Control
Control of SOx emissions
Control of NOx emissions
Conclusion
CONFIDENTIAL BUSINESS INFORMATION

29. Controlling SOx in Full Combustion
Feedstock effect
About 10% emitted as SOx (range: 5-35%)
To improve SOx additive efficiency:
Drive SO2 to SO3 equilibrium towards SO3
Increase excess O2 (up to ~2%)
Reduce bed temperature
Increase regenerator pressure
Use of CO promoter
Enhance additive efficiency
Increase cat circulation rate
Factors reducing additive efficiency:
High catalyst losses
Large regenerator inventories
Poor stripper efficiencies
High Fe on equilibrium catalyst
Total elimination of SOx emissions is achievable

30. Controlling SOx - Partial Combustion
SOx additives in partial burn:
Majority of S is normally in reduced form
e.g. COS, H2S
Oxidation of S→SO2→SO3 limiting step
Tailored oxidation component required for maximum additive effectiveness
Compare SO2 in flue gas vs. stack prior to using additives
Normally only about 30% of S will be in oxidized state
Partial burn guidelines:
There is a practical upper limit to SOx reduction with additives
Monitor SOx concentration in flue gas upstream of CO Boiler thru trial
Monitor regenerator CO-to-CO2 ratio as additive concentration increases
Sulfur Species Data from European 7% CO
Deep SOx reductions in partial burn are feasible

31. Controlling NOx Emissions
NOx formation:
~10% of N in coke emitted as NOx
Excess O2 is the most significant operating variable affecting NOx emissions
Maldistribution of air & catalyst leads to high NOx emissions
NOx reducing additives are effective in full combustion
There is an effective unit specific maximum concentration
Exceeding this maximum will have no effect or may actually increase NOx
Additive efficiency is highly unit specific
Effectiveness in Partial Burn is limited

32. 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 can be improved for reduced emissions:
Ensure counter current operation
Distribute spent catalyst uniformly across the top of the regenerator bed
Inject combustion air uniformly across cross section of regenerator
Additives are normally effective for further reductions if needed
Courtesy: KBR

33. 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
Be sure to use good additive loader technology for optimum performance
See example on right 
Reliable additive injection is essential
INTERCAT offers loaders for all of its additives
Example of enhanced additive effectiveness due to improved loader reliability

34. CONFIDENTIAL BUSINESS INFORMATION
Overview
Introduction
Particulate Emissions:
CPFD Modeling
Catalyst attrition
Cyclone integrity
SEM analysis
Afterburn Control
Analysis & control
Gaseous Emissions Control
Control of SOx emissions
Control of NOx emissions
Conclusion
CONFIDENTIAL BUSINESS INFORMATION

35. Conclusion
Advanced troubleshooting techniques can help the FCC engineer monitor, troubleshoot, & optimize the FCC regenerator
A good quality base case taken during normal operations is essential for swift troubleshooting
Most catalyst companies have substantial “hands on” regenerator troubleshooting & optimization expertise
Take advantage of this expertise, and use it to ensure the baseline FCC operation is thoroughly understood
Will ensure that any operational problems can be quickly diagnosed whenever they arise