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Computational Fluid Dynamics (CFD):An Effective Tool for FCC Design, Improvement and Troubleshooting
David Chaplin, FCC Technology Manager d id h li @ h
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CFD Modeling PhilosophyCFD Modeling Philosophy
• Two CFD modeling approaches for multiphase
Continuous Approachtwo-fluid model
gas-solid systems– Continuous approach
• Gas phase as fluid; solids phase as pseudo fluid
Vapor Volume fraction
Solid Volumeas pseudo fluid– Discrete approach
• Gas phase as fluid; solid phase as solid particles
CFD ft d ithi thDiscrete Approach
Solid Volume fraction
• CFD software used within the Alliance
– FluentBarracuda by CPFD Software LLC
particle-dynamics model
Vapor
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– Barracuda by CPFD Software LLC– Software selected depends on
problem
p
Solid Particles
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CFD Application in Alliance FCC T h l
CFD Application in Alliance FCC T h lTechnologyTechnology
• Research and DevelopmentD l t d d i f t h l– Development and design of new technology
– Cost-effectively screen new designs– Minimize cost of cold-flow testing
• Design– Developing design criteria
Fine tuning and optimization– Fine tuning and optimization
• Unit Revamps and Troubleshooting– Design optimization
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– Diagnose root causes– Validating solutions
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FCC Areas Modeled With CFDFCC Areas Modeled With CFD 0
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Reactor RSS DevelopmentReactor RSS Development
• Validate cold flow results with fluent CFD software• Optimize design with CFD• Develop design criteria
ImplementationConcept Validation Cold Flow Experiments & CFD Design
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Regenerator RSS DevelopmentRegenerator RSS Development
Objective• Reduce catalyst loss rate
– Replace tee separators in a high efficiency combustor
• Improve cyclone reliability• Regenerator too small to• Regenerator too small to
increase number of cyclones to reduce inlet velocity
• Adapt reactor RSS design – No cold flow work– CFD modeling only
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Before Revamp After Revamp
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Regenenerator RS2 DevelopmentRegenenerator RS2 Development
• Replace Combustor Tee Separator2• High separation efficiency of RS2
• Improved cyclone reliability• Increases regenerator capacity g p y• No interference with cyclones diplegs
≥2
Patte
rns
m/s
) ≥5
ng(%
v)
≥
Patte
rns
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Gas
Flo
w P
≤-5
vel(
m
so
lids
load
i
Solid
Flo
w
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0 solids loading (% v) =10 solids loading (% v) =1
G
0 residence tim e (s) =10 residence tim e (s) =1
0 S
Regenenerator RS2 DevelopmentRegenenerator RS2 Development
BEFORE AFTER
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RS2 Development for External Riser System
Concept CFD Optimization Pilot PlantCo cept C Opt at o ot a t
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Initial Design Concept Improved
Design
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Spent Catalyst Wye Bathtub DistributorDesign Optimization
Spent Catalyst Wye Bathtub DistributorDesign OptimizationDesign OptimizationDesign Optimization
Cat Density Profiley
Original Concept
Cat Velocity Profile
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Cat Velocity ProfileOptimized Design
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Spent Catalyst DistributorCFD M d liCFD Modeling
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Spent Catalyst Wye Bathtub DistributorDesign Optimization
Spent Catalyst Wye Bathtub DistributorDesign OptimizationDesign OptimizationDesign Optimization
CFD used to determine optimum design parameters Pr
ofile
• Improved catalyst distribution along its length
at D
ensi
ty P
Ca
ofile
eloc
ity P
ro
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Plan view showing uniformdistribution of catalyst
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Regenerator Fluidization OptimizationRegenerator Fluidization Optimization
CFD Modeling to study the effect of
i i l tiair ring location on fluid bed hydraulics
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Staggered Inner ring relocated
to BTL
All rings at same
elevation.
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Regenerator Fluidization Optimization Regenerator Fluidization Optimization Staggered ring Relocate inner ring to BTL Relocate middle and inner
ring To BTL
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Stripper TroubleshootingStripper Troubleshooting
I fl f t• Influence of reactor fluidization on stripper performanceperformance
• CFD used to study effect of reactor fluidization on stripper operationS i d
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• Stripper upset caused by de-fluidized catalyst entering stripper
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Reactor RS2 Dome Steam SpecificationsReactor RS2 Dome Steam SpecificationsContours of mole fraction of HC vapor (red).
Steam is blue.
CFD used to develop new design criteria
Slip Joint
design criteria for dome steam flowrate.
V
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Vapor outlet
Increase dome steam flow
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ConclusionsConclusions
• FCC Alliance committed to improving FCC hardware through increased use of CFDhardware through increased use of CFD– Reduce technology development cost– Bring new technologies to market faster– Improve FCC hardware design– Verify design without cold flow testing – Increase reliabilityy– One of the key troubleshooting tools
• CFD is a cost-effective tool that is useful in most aspects of FCC design
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aspects of FCC design
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