8th Summer School on Petroleum Refining & Petrochemicals 3 – 7 June, 2013
FCC PROCESS FUNDAMENTALS & TECHNOLOGY EVOLUTION June 3, 2013
Debasis Bhattacharyya (
[email protected])
Outline Process fundamentals Catalytic cracking Fluidization regimes Position in refinery Process flow diagram Mode of catalyst regeneration Heat balance Process variables
Technology evolution Reactor-Regenerator configuration Hardware internals Catalysts & Additives Resid processing Requirement specific developments
Summary
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Refining Processes Crude oil separation
Contaminant removal / product quality improvement
Refinery
Molecular cracking: large to small
Molecular rearrangement & combination
Cracking of Heavy Hydrocarbons Cracking : Breaking large molecules by application of heat with or without catalyst with or without hydrogen
Thermal High coke
Catalytic
Hydro Low coke
Fluid Catalytic Cracking (FCC)
Dry gas Vacuum gas oil (VGO)
(H2, C1, C2)
Hydro-treated VGO
LPG (C3, C4)
Hydro-cracker bottom Coker gas oil (CGO) De-asphalted oil (DAO) Reduced crude oil (RCO)
Vacuum residue (VR)
Light cracked naphtha (LCN) (C5-150oC)
Heavy cracked naphtha (HCN) (150 - 220oC)
Light cycle oil (LCO) (220 - 370oC)
Clarified oil (CLO) or Decant oil (DO)
Conversion wt% = (Feed- LCO- CLO)*100/Feed
……. being continued till today5
Position of FCC in Refinery Gas
S T A B
Crude
LPG
Gasoline Blending
C R U D E
HDS
Gasoline
CCR Reformate
D I S T
Kerosene Jet fuel
HDS HDS V A C D I S T
Hydro-cracker/ Treater Visbreaker / Coker BBU
Diesel
FCC
Fuel Oil Coke Bitumen
6
Schematic of FCC Products to Fractionator Reactor
Flue Gas to WHRU Minimum fluidization (0.001-0.05 m/s)
Bubbling (0.05-0.30 m/s) Stripper Steam
Regenerator
SCSV
Turbulent (0.7-1.1 m/s) Fast fluidization/ Pneumatic transport (5-20 m/s)
Air
RCSV
Riser Feed
RCSV with Riser outlet temp. SCSV with reactor level Steam
7
Fluidization Regimes P L
Umf
P L
Umb
Uch
.. . . . ... Fixed bed
Particulate regime
Bubbling regime
Slug flow regime
Turbulent regime
Increasing Gas Velocity
Fast fluidization
.... . . .. . . . . .. . . . .. .... Pneumatic conveying 8
Fluid Catalytic Cracking
Feed surge drum Pump Feed pre-heat furnace
DDSV Orifice chamber CO boiler Waste heat recovery section Flue gas stack
Wet gas compressor
FCC Internals Reactor dome quench nozzle
Cyclone separator
Riser termination device
Regenerator dome quench nozzle
Stripper internals
Cyclone separator Stripping steam distributor
Regenerator air distributor
Spent catalyst distributor
Feed injection nozzles 10
Main Catalytic Cracking Reactions Paraffins
Cracking Cyclization Isomerization H Transfer Cyclization Condensation Dehydrogenation
Olefins
Naphthenes
Aromatics
Cracking
Cracking Dehydrogenation Isomerization
Side chain cracking Trans alkylation Dehydrogenation Condensation
Paraffins + Olefins LPG Olefins Naphthenes Branched Olefins Paraffins Coke Coke Coke
H Transfer
Branched Paraffins
Olefins Cyclo-olefins Dehydrogenation Naphthenes with different rings
Unsubstituted aromatics + olefins Different alkyl aromatics Polyaromatics Alkylation Dehydrogenation Condensation
Aromatics
Coke
Hydrogen transfer Naphthene + Olefin Aromatic + Paraffin 11
Different Modes of FCC: Comparison Mode
LPG
Gasoline
Distillate
Dry gas
Typical product yields, wt% 6.5 4 2
LPG
40
18
10
Gasoline (C5-150oC) TCO (150-370oC)
25 10
45 22
30 44
CLO ( 370oC+ )
4
6
10
Coke
6.5
5
4
216oC - Conversion
90
81
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Coke deposited on catalyst – blocks the active site – causes temporary deactivation needs burning to regenerate before circulating to riser 12
Types of Coke Coke yield = Feed coke + Catalytic coke + Strippable coke + Contaminant coke Feed coke = 1 (feed CCR); where, 1 = f1(feed vaporization/distribution)
Catalytic coke = f2 (ROT, Cat/oil ratio, Catalyst/feed quality, Conversion level..) Strippable coke = f3 (Stripper efficiency, Riser operation- temp.) Contaminant coke= Coke contributed by the contaminant metals in feed = f3 (metal level on catalyst, catalyst characteristics, operation severity, use of metal passivator)
Coke deposited on catalyst – blocks the active site – cause temporary deactivation of the catalysts Coke on catalyst needs to be burnt to regenerate before circulating to riser bottom Balancing coke is the most crucial in design of FCC unit
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Mode of Catalyst Regeneration Coke burning reactions C + 1/2O2 CO (∆H = - 2200 kcal /kg)
CO + 1/2O2 CO2 (∆H = - 5600 kcal /kg) H2 + 1/2O2 H2O (∆H = - 28900 kcal /kg)
Mode
Total Combustion
Partial Combustion
Coke on regenerated catalyst, wt%
< 0.05
> 0.05
Effective catalyst activity
Higher
Lower
Regenerator temperature, oC
Higher
Lower
CO in flue gas, ppm
< 1000
> 1000
Requirement of CO Boiler
No
Yes
Chances of Afterburning
Lower
Higher 14
FCC Heat Balance Flue gas
Regenerator
Spent Catalyst
Reactor Products
Heat of Coke Combustion
Heat losses
Heat Losses
Heat of Reaction Recycle
Regeneration Air
Regenerated Catalyst
Fresh Feed Feed Pre-heater
15
FCC Heat Balance Coke yield
= Wcoke/Wfeed = Wcat*(CSC-CRC) / Wfeed = (Cat/Oil)*(Delta Coke)
Delta Coke = (Cpcat / DHcoke )*(Trg-Trc) (Trg-Trc) Coke yield =
Reactor heat demand per unit total feed
Heat of Combustion per unit Coke = (Cat/Oil)*(Delta Coke)
Delta Coke (Trg-Trc) For a given ROT, more is the Delata coke, more will be the regenerator dense bed temperature 16
Variables in FCC Independent
Feed rate Recycle ratio Feed preheat Riser top temperature Reactor pressure Fresh catalyst activity / Selectivity
Major dependent
Regenerator temperature Catalyst circulation rate Regenerator air flow Coke on regenerated catalyst Product yields 17
Evolution of FCC Technology 1940s
Fluid Catalytic Cracking Process for Gasoline
Period
FCC process development
1936-1941
Fixed bed
1941-1960
Moving bed
1942-today
Fluid bed
1942
1ST commercial FCCU was on stream at Baton Rouge Refinery of Standard Oil of New Jercy
End of 1945
33 FCCU were in operation
1955-1970s
Dense bed reactor
Post 1970s
Short contact riser with pneumatic conveying become popular 18
Evolution of FCC Hardware Design
19
Exxon’s Model-IV FCC Unit
Flexi-cracking by ExxonMobil
20
Evolution of FCC Hardware Design
Kellogg Orthoflow FCC Converter
Orthoflow Resid FCC Converter
21
Resid FCC Units Two-stage regenerator
Fast fluidized regenerator
UOP high efficiency regenerator RFCCU
UOP RFCC Unit
22
Two Stage Regeneration
RFCC unit by SWEC
R2R unit by Axens 23
Evolution of FCC Hardware Design
Source: www.kbr.com
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Feed Injection System Rapid feed vaporization and uniform mixing with catalyst Reduce non-selective cracking & thermal reaction
Better feed nozzle design using dispersion steam Enhance vaporization Avoid backmixing of hydrocarbons
Avoid thermal cracking Reduce hydrocarbon partial pressure
Feed coke = 1 (feed CCR)
Reduce coke make & improve yields
where, 1 = f1(feed vaporization/distribution) 25
Effect of Feed Atomization Parameter
Case-1
Case-2
Case-3
500
100
30
1
125
4630
0.001
0.11
4
at 50% vorization
220
11
4
at 90% vaporization
400
20
8
Oil droplet size, Relative no. of droplets Oil droplets/catalyst particle Vaporization time, milisec
26
Reactor Riser Disengaging Devices
T-Type Disengage r
Down Turned Arm
Vented Riser
Direct-Connected Cyclones 27
Reactor Riser Disengaging Devices
Source: www.kbr.com
Ramshorn type or Linear Disengaging Device (LD2)
Closed Cyclone Riser Termination
Vortex Separation System 28
Regenerator Cyclone System & Orifice Chamber
Source: www.hason-steel.com
Regenerator Cyclones
Orifice chamber
Regenerator Air Distributor Air distributors • • • • •
Minimizing gas bypassing or channeling Mass transfer diffusion resistance Erosion Thermal expansion – mechanical reliability Mechanical integrity of supports
Commonly used • Pipe grid • Air ring Flat pipe grid preferred due to uniform coverage & lower discharge velocity
Efficient air grid • Total combustion regenerators least excess oxygen in flue gas • Partial combustion regenerators minimum afterburning 30
FCC Catalyst Improvement Catalysts Heart of FCC process undergone evolutionary changes Colloidal binder
Zeolite pores 6.5-13. 5A Interparticle void clay Matrix pores 10-200A
1 micron
Zeolite: Silica-alumina Amorphous matrix: Silica, silica-alumina, alumina Filler clay: Silica-alumina Other elements: Rare earth, Sodium
1942
Natural clay, Synthetic low alumina catalyst
1948
Micro-spheroidal catalyst (low alumina)
1955
High alumina synthetic catalyst
1961
D5 zeolite TCC bead catalyst
1964
Spray dried fluid Y zeolites
1980
Coke selective Re-HY catalysts
1986
Improvement in Y-zeolites (USY) – low coke selectivity, Higher octane (low non-framework alumina) 31
FCC Catalyst Improvement Improvements in FCC catalysts Year
1950
1970
1990
Zeolite content, wt%
0
10
40
Particle density, g/cc
0.9
1.0
1.4
Relative Attrition Index
20
5
1
Today’s FCC catalysts Porous spray dried micro-spherical powder Particle size distribution of 20 -120 micron & particle density ~ 1400 kg/m3 Comprising Y zeolite in many derivatives of varying properties Supplied under various grades of particle sizes & attrition resistance Continuing improvement metal tolerance, coke selectivity Zeolite based catalyst – improved yields of desired products with given feed & hardware
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Use of Additives ZSM-5 Additive • Increases yields of LPG / Light olefins • Improves Gasoline RON
CO Promoter • Enhances CO burning in regenerator dense bed
Bottom Cracking Additive • Upgrades bottom fraction of feed without proportional increase in coke make
GSR Additive • Reduces Gasoline Sulfur content by ~ 30%
SOX Control Additive
Ni passivator & V- Trap
• Reduces SOx in regenerator flue gas
• Reduces detrimental effects of metals on product yields & catalyst health 33
Problems with Resid Processing in FCC Ni
More H2, Dry Gas & Coke
S
SOx Emmission, ‘S’ in Product
V &Na
Zeolite Destruction
Basic N2
Zeolite Acidity Neutralization
Aromatics
More Coke & Low conversion
Con. Coke
High Regen temp, Low Cat/Oil High catalyst consumption to maintain activity 34
FCC Catalyst Cooler
External vertical shell & tube heat exchanger
Removal of heat
• Catalyst flows over entire cross sectional area of tube bundle in dense phase
• Reduces regenerator temperature • Retains catalyst’s activity
• Provides variable heat sink & produces steam upto 850 psig
• Increases catalyst to oil ratios • Better yields & enhanced profitability 35
Shifting in objective of FCC operation
Operating Objective
Petrochemical feed stock Alkylation& Isomerization feed
•Product quality •Resid •Gasoline 1942
1970
1990
1995
2010
36
Technologies Developed by IndianOil Technology
Feed
Major products
Challenges overcome
INDMAX
Heavy feedVGO, RCO, VR (part)
Light olefins, LPG, • Deep cracking of heavier feed high octane with lesser Coke & Gas gasoline formation • Unit heat balance • Metal deactivation of catalyst
INDALIN
Naphtha
Light olefins, LPG, • Cracking of low molecular gasoline weight hydrocarbon • Unit heat balance
INDALIN Plus
Naphtha
Auto-grade LPG (saturated) & high octane gasoline
• Cracking of low molecular weight hydrocarbon • Unit heat balance • Saturation of LPG without using external hydrogen
Dist-Extra
Heavy feedVGO
Diesel component with higher cetane
• Optimization of intermediate fraction with lower yield of bottom fraction
Indmax Technology – Resid to Olefins Operational features High cat/oil ratio (15-25) Higher riser temperature (>550oC) High riser steam rate Relatively lower regen temp. Benefits LPG 35-55 wt% Propylene 17-25 wt% feed High octane gasoline (95+) Multifunctional proprietary catalyst Higher propylene selectivity Superior metal tolerance Lower coke make
Successfully commissioned at Guwahati refinery in June’03 - Smoothest commissioning in IOC’s FCC start-up
Indmax can handle high CCR, non-hydrotreated feed with attractive LPG / light olefins yield
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Indmax-FCC Reactor-Regenerator Direct-Coupled Cyclones
Cyclone Containment Vessel (CCV)
Reaction Riser (Short Contact Time)
MG Stripper
Turbulent Regenerator Bed
Direct-Coupled Cyclones Cyclone Containment Vessel (CCV)
MG Stripper
Turbulent Regenerator Bed External Regenerated Catalyst Hopper
Being worldwide licensed by Lummus Technology, USA based on Basic Process Design data/information & catalyst from IndianOil Micro-Jet Feed Injection Nozzles
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INDMAX - Continual Development Improvement of light olefins yield Setting up 85000 BPSD unit Collaboration with Lummus for global marketing & licensing Scale up & Commercialization
Process development & pilot plant demonstration
INDMAX Yields of light olefins with paraffinic VGO feed (wt%): Propylene: 27 Butylenes : 15 Ethylene : 14
IndianOil’s proven INDMAX technology can meet Refiner’s objectives of propylene maximization 40 &
Summary FCC has been the most profitable & flexible refining process for more than seven decades because of its ability to meet changing demands FCC technology is still undergoing significant evolution
Beyond certain feed CCR, RFCC becomes too expensive due to high consumption of catalyst & inferior product yields Increasing gap in propylene demand & supply drives orientation of FCC operation towards propylene maximization Scenario specific tailor made technology can be developed through proper understanding of fundamentals IndianOil’s proven INDMAX technology can meet the Refiner’s objectives of propylene maximization & residue upgradation in an cost effective manner 41
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