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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david.chaplin@shawgrp.com

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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

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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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Flo

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≤-5

vel(

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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.

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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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