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FCC Regenerator Design to Minimize Catalyst Deactivation and … · 2008-10-10 · Feed Stock Type...
Transcript of FCC Regenerator Design to Minimize Catalyst Deactivation and … · 2008-10-10 · Feed Stock Type...
FCC Regenerator Design to Minimize Catalyst
Deactivation and Emissions
FCC Regenerator Design to Minimize Catalyst
Deactivation and Emissions
Steve TragesserShaw Energy and Chemicals Group
Shaw Stone & Webster FCCsShaw Stone & Webster FCCs
Resid RFCCs (R2R)Other FCC/DCCs (R1R)
42 RFCC/FCC/DCC Units Licensed
Regenerator Design ObjectivesRegenerator Design Objectives
• Effective regeneration of catalyst• Minimum catalyst deactivation• Efficient use of available air blower capacity • Minimum damage to equipment• Minimum toxic emissions
Typical Regenerator DesignsTypical Regenerator Designs
REGEN
Air
Spent Catalyst
Counter-Current Regeneration
Co-Current Regeneration
REGEN
Air
Spent Catalyst
Typical Co-Current RegeneratorTypical Co-Current Regenerator
Spent catalyst
Air
Regenerator
Reactor
Typical Counter-Current RegeneratorTypical Counter-Current Regenerator
Spent catalyst
Air
Regenerator
Reactor
Interior Particle Temperature RiseInterior Particle Temperature Rise500
450
400
350
300
250
200
1500 2 4 6 108
Tem
pera
ture
Ris
e, °F
Time, Milliseconds
(Co-Current)
(Counter-Current)5% O2
5% C
5% O2
10% C
5% C20% O2
AfterburnAfterburn
Burning of CO Above the Regenerator Bed
1. Can occur in dilute phase, cyclones, plenum chamber and/or flue gas line
2. Temperatures can damage regenerator internals
3. Can be limiting temperature in regenerator
Spent Catalyst DistributionSpent Catalyst Distribution
Spent Catalyst Without DistributorSpent Catalyst Without Distributor
Elimination of Serious Afterburn ProblemsElimination of Serious Afterburn Problems
Principle Causes• Spent Catalyst Distribution• Air Distribution• Shallow Bed
Solutions• Distribute Spent Catalyst Across Bed• Minimum Bed Height (3 – 5 meters)• Air Distribution
– Multiple Rings– Pipe Grids
Axens/Stone & Webster Distributor
Spent Catalyst DistributionSpent Catalyst Distribution
Even catalyst distribution
Side Entry RegeneratorNo Distributor
Poor catalyst distribution
High coke concentration
Bathtub Spent Cat DistributorBathtub Spent Cat Distributor
Bathtub for Counter-current Regeneration and Low NOxBathtub for Counter-current Regeneration and Low NOx
Spent Catalyst DistributorSpent Catalyst Distributor
Bathtub Spent Cat DistributorBathtub Spent Cat Distributor
Bathtub CFD ModelingBathtub CFD Modeling
Combustion Air RingCombustion Air Ring
Cross Section of Ring
Cross Section of Tee
Air Ring Installation Air Ring Installation
Air Ring Nozzle LayoutAir Ring Nozzle Layout
Two Stage Regeneration –The Key to Resid Processing
Two Stage Regeneration –The Key to Resid Processing
Why Two Stages for Resid?• Heat balance control for high
concarbon feeds• Minimizes catalyst deactivation
for severe regeneration required– Lower average catalyst particle
temperature– Less hydrothermal deactivation– Less vanadic acid deactivation
Two Stage Regeneration ConceptTwo Stage Regeneration Concept
1. First stage regenerator design• Countercurrent Regeneration• Heat Removal Via CO
Production (partial burn)2. Second stage regenerator design
• Complete combustion• Minimum moisture
Catalyst Cooler Catalyst Cooler
R2R with Catalyst CoolerR2R with Catalyst Cooler
Catalyst Cooler
SRC Singapore
Regenerator EmissionsRegenerator Emissions
• Particulates
• CO
• SOx
• NOx
Primary Causes of Particulate LossesPrimary Causes of Particulate Losses
• Catalyst Attrition– Fracture– Abrasion
• Cyclone Design• High Superficial Velocities• Damaged Equipment
– Air Distributor– Cyclone System
• Operation– Bed Level– High Velocity Nozzles
Final Particulate Removal OptionsFinal Particulate Removal Options
• 3rd stage cyclonic separation (80 mg/Nm3)• 3rd stage cyclonic separation with 4th stage
underflow filter (50 mg/Nm3)• Wet gas scrubbing (10 to 20 mg/Nm3)• Electrostatic precipitation (10 mg/Nm3)• Physical filtration (less than 10 mg/Nm3)
BP Kwinana Flue Gas FilterBP Kwinana Flue Gas Filter
R1R1
R2R2
140 mg/Nm3140 mg/Nm3
330 mg/Nm3330 mg/Nm3
RegenRegen33rdrd Stage Stage SeparatorSeparator Waste Waste
Heat Heat BoilerBoiler
Orifice Orifice chamberchamber
StackStackReactorReactor Flue Gas Filter by
Pall
2 mg/Nm32 mg/Nm3
BP Kwinana Flue Gas FilterBP Kwinana Flue Gas Filter
TubesheetTubesheetInstallationInstallation
OverviewPictures courtesy of Pall
SOx StrategiesSOx Strategies
• Minimize Coke Yield (Reaction technology)
• Use Desox additive to control small amounts SOx
• Use scrubber to control large amounts SOx
• Avoid Recycle of heavy streams
Wet Gas Scrubbing for SOx Removal
Belco®’s EDV Wet Gas Scrubber
FCC Variable Affecting SOx Emissions and Additive Performance
FCC Variable Affecting SOx Emissions and Additive Performance
Poor stripping will increase SOxStripper Operation
Near-continuous addition improves efficiencyAdditive AdditionIncreasing CO promoter improves efficiencyCO Promoter UsageHigher temp. favors reduction of sulfates to H2SReactor TemperatureIncrease favors SO2 oxidation, hinders SO3 absorptionRegenerator Temp.Increasing excess O2 improves efficiencyRegenerator OperationLarger inventories reduce efficiencyRegenerator InventoryHigher rate improves efficiencyCirculation RateActivity and additives present (SOx & CO)Equilibrium CatalystHigher alumina improves SOx efficiencyFresh Catalyst
Usually heavy coke-sulfur formingRecycle streamsLevel and type of sulfur in feedFeed Stock Type
Effect on Sox Additive PerformanceVariables
NOx ControlNOx Control• Very complex
• Related to feed nitrogen, not combustion air
• High platinum CO promoter & excess oxygen amplifies NOx
• Much of NOx is reduced to N2 or leaves as NH3, HCN, etc. (70 – 95%)
Comparison of NOx Emissions in Commercial FCC Regenerators
Comparison of NOx Emissions in Commercial FCC Regenerators
0
5
10
15
20
30
25
0.0 1.0 2.0 3.0 4.0
Excess Oxygen in Flue Gas
% N in Coke to NOx
Counter-Current (Swirl)Counter-Current (Bathtub)
Optimum Regenerator DesignOptimum Regenerator Design
• Turbulent bed
• Countercurrent regeneration
• Minimum excess oxygen
• Spent catalyst distributed across entire bed
• Minimum gas residence time of 4 seconds
Thank YouThank You
The Shaw Group Inc.