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transcript
FCC Gasoline Treating UsingCatalytic Distillation
Texas Technology ShowcaseMarch 2003, Houston, Texas
Dr. Mitchell E. Loescher
Gasoline of the FutureGasoline of the Future
Lead is outOlefins reducedAromatics reducedBenzene reducedSulfur reduced
Gasoline Desulfurization RequirementsGasoline Desulfurization Requirements
– Pool sulfur specification• Europe
– European Union– 50 ppm max - 2005– 10 ppm max – - available 2005– - standard 2008
• US, Canada– 30 ppm avg - 2002 to 2008
• Future– 15 -10 -5 ppm? - 2005+
Sulfur SourcesSulfur Sources
FCC Naphtha– 200 to 3000 ppm– 25 to 40% of refinery pool volume– 85 to 99% of refinery pool sulfur
FCC Gasoline Feed CompositionFCC Gasoline Feed Composition
02000400060008000
1000012000
50 100 150 200 250
Temperature, C
Sulfu
r, pp
m
0
10
20
30
40
Ole
fins,
%
Sulfur Olefins
Optimized HDS ProcessOptimized HDS Process
FCC C5+GASOLINE
LCNMild HDSMild HDS
MediumMediumHDSHDS
SevereSevereHDSHDS
MCN
HCN
MCN/HCN
Conventional LCN TreatingConventional LCN Treating
Fractionate LCN from FCC Gasoline
SelectiveHydrogenation
TREATED LCN
HYDROGEN
HydrogenCompression
FCC C5+GASOLINE
MCN/HCN
FRESH CAUSTIC
MercaptanRemoval
SPENT CAUSTIC
Caustic wash for mercaptan removal– ~90% effective
Selective hydrogenation of dienes for alky/ethersCompression of makeup hydrogen
LCN
Hydrogenation / DistillationHydrogenation / Distillation
Vent Gas
CW
Steam
Hydrogen
Bottoms
Treated Distillate
HydrocarbonFeed
CDHydro® Process
Add Hydrogen Feed
Replace trays with structureddistillation packing containing catalyst
Vent excess Hydrogen
CDCDHydroHydro ReactionsReactions
Thioetherification
C CCC
C+
SHCC
C
C
C
CC S CC
Selective Hydrogenation
C CCC
C+ H H
C CCC
C
CDCDHydroHydro ReactionsReactions
Isomerization
CCC
C C
RON
118
CDCDHydroHydro ReactionsReactions
Isomerization
CCC
C C
RON
118 150
Hydroisomerization boosts full range FCC naphtha by 0.5 RON
+0.5
Catalytic DistillationCatalytic Distillation
Catalyst SectionDrawing
WireMesh
Catalyst
Vapor
RefluxH2
Optimized FCC Naphtha HDSOptimized FCC Naphtha HDS
FCC C5+GASOLINE
LCN
MCN/HCN
HydrogenCDHydro®
HDSHDS
CW
LPSteam
Low SulfurFCCGasoline
LightEnds LightEnds
StripperReactors
FCCGasoline
Make-upHydrogen Recycle
Hydrogen
Conventional MCN/HCN HDSConventional MCN/HCN HDS
Conventional Reactor DesignConventional Reactor Design
Severity of reactor conditions set by most refractory species– Temperature– H2 partial pressure
Lighter sulfur species react to very high conversionsAll olefins exposed to the most severe conditions
Reactors
Conventional Fixed Bed HDSConventional Fixed Bed HDS
0
20
40
60
80
100
0 0.2 0.4 0.6 0.8 1
Reactor Length
Conv
ersi
on (%
)
Total SLight SHeavy SOlefin 1Olefin 2
Olefin 1 Olefin 1 -- with recombinant mercaptan in productwith recombinant mercaptan in productOlefin 2 Olefin 2 -- w/o recombinant mercaptanw/o recombinant mercaptan
Recombinant Mercaptan ExperienceRecombinant Mercaptan Experience
Mercaptan Levels
0 2 4 6 8 10
Octane Loss (R+M)/2
RSH
Lev
el, p
pm
fixed bed RSH
FCC C5+GASOLINE
Optimized FCC Gasoline HDSOptimized FCC Gasoline HDS
LCNMild HDSMild HDS
MediumMediumHDSHDS
SevereSevereHDSHDS
MCN
HCN
MCN/HCN
80
82
84
86
88
90
92
50 100 150 200 250
Boiling Point, C
Oct
ane
No.,
(R+M
)/2FCC Gasoline Octane DistributionFCC Gasoline Octane Distribution
MCN/HCN with CDMCN/HCN with CDHDSHDS
Conditions milder than conventional fixed bed (17 barg vs 28+)
> 99% HDSHeavy sulfur to bottom
Off GasCW
Hydrogen
CDHDS®
FCC C7+ Gasoline
Light olefins to top Min octane loss(<1@ 90% HDS) Low H2 consumptionLow sulfur bottoms product good for
gasolineNo yield loss due to crackingNo makeup compressorNo mid-cycle shutdown for catalyst regenNo feed storage required
Selectivity CurveSelectivity Curve
0
0.2
0.4
0.6
0.8
1
200 250 300 350 400 450 500
Temperature, F
Conv
ersi
on, F
ract
ion
Sulfur reduction Olefin reduction
Olefin saturation is higher for heavy olefins
Octane vs. Carbon NumberOctane vs. Carbon NumberRON Linear Olefin - Linear Saturate
0
20
40
60
80
100
120
5 6 7 8 9 10 11
Carbon Number
RON
Why isWhy is CDTECH’sCDTECH’s octane loss lower?octane loss lower?
Conventional fixed bed hydrotreaters– Saturate primarily light olefins– Light olefin saturation causes high octane loss
CDHDS– Higher saturation of heavy olefins– Less octane to lose in heavy olefins– Lower octane loss at a given olefin reduction
Fixed Bed HDS Catalyst Life?Fixed Bed HDS Catalyst Life?
FCC turnaround cycle– Modern refineries target 5 year cycle
Conventional fixed bed hydrotreaters– Olefins form oligomers– Oligomers form coke that fouls catalyst– Catalyst activity reduced– Regenerate or replace catalyst– Must shutdown before end of FCC cycle– Fixed bed catalyst life insufficient
Commercial Catalyst Activity for FCC Gasoline HDS
0.000 365.000 730.000
Days on Oil
Rel
ativ
e A
ctiv
ity
Fixed Bed HDS
Catalyst Activity History for Commercial CDHDS Units
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 100 200 300 400 500 600 700 800 900 1000
Days Since Start-up
Obs
erve
d R
ate
Con
st.
Irving Oil Motiva ChevronTexaco
Conventional Fixed Bed Unit Conventional Fixed Bed Unit ShutdownShutdown
FCC unit Sulfur ReductionUnit
Untreated FCC Gasoline storage
x
Conventional Unit RestartConventional Unit Restart
FCC unit Sulfur ReductionUnit
Untreated FCC Gasoline storage
x
Extra Capacity Required
ConclusionsCDHydro
Lowest sulfur and diolefins in LCNEliminates separate mercaptan and diolefin removal units
CDHDSLowest FCC cycle olefin loss via HDSNo cracking yield lossNo diene pretreatment requiredNo regeneration/feed storage required
CDHydro/CDHDSLowest overall octane lossCommercially provenMost cost effective HDS in FR FCC CNLong catalyst life via catalytic distillationLow capital cost
Recommendations
•Plan for 10 ppm sulfur
•Evaluate full FCC cycle performance
•Include shutdown related capital cost
•Thank you to DOE for 1980 funding for CR&L