Post on 29-May-2017
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Processes in the oil refinery
Crude oil
Straight run gasoline
LPG and Gas
Naphtha
Hydro-treating
Reformate
Middle distillates
Heavy atm. gas oil
Solventextraction
Lube base stocks
Gasoline
Vacuum gas oil
Solventdewaxing
Lube oils
Waxes
Gasoline, Naphtha, Middle distillates
Gasoline, Naphtha, Middle distillates
Gasoline, Naphtha, Middle distillates
Slurry oil
Refinery fuel gas
LPG
Gasoline
Solvents
Kerosene
Diesel
Heating oil
Lube oil
Greases
Asphalt
Industrial fuels
Coke
Trea
ting
and
Blen
ding
Delayed coker / Flexicoker
Propanedeasphalter
Hydro-treating
Catalyticreforming
Catalyticcracking
Visbreaker
Hydro-cracking
Fuel oil
Asphalt
LPG and Gas
Cycle oil
Alkylation AlkylateLPG
Hydro-treating
Vacu
umD
istil
latio
nAt
mos
pher
icD
istil
latio
n
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Crude Oil RefiningDistillate fraction Boiling point
(oC)C-atoms/molecule
Gases <30 1-4Gasoline 30-210 5-12Naphtha 100-200 8-12Kerosine (jet fuel) 150-250 11-13Diesel, Fuel oil 160-400 13-17AtmosphericGasoil
220-345
Heavy Fuel Oil 315-540 20-45AtmosphericResidue
>540 >30
Vacuum Residue >615 >60
MiddleDistillates
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Chemical processesThermal Catalytic
Visbreaking HydrotreatingDelayed coking Catalytic reformingFlexicoking Catalytic cracking
HydrocrackingCatalytic dewaxingAlkylationPolymerizationIsomerization
Processes in an Oil Refinery
Physical processes
DistillationSolvent extractionPropane deasphaltingSolvent dewaxingBlending
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620 K
C1 - C4
Gases
Gasoline
Kerosene
Gas oil
ResidueCrude oil
steam
steam
steam
reflux water
Fractionator Stripper StripperFurnace
Simple Crude Distillation
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Market DemandsMarket Demands
•• Clean products (no S, N, O, metals, etc.)Clean products (no S, N, O, metals, etc.)•• More gasoline (high octane number)More gasoline (high octane number)•• More diesel (high cetane number)More diesel (high cetane number)•• Specific products (Aromatics, alkenes, etc.)Specific products (Aromatics, alkenes, etc.)•• Less residueLess residue
How to meet these demands?How to meet these demands?
•• More sophisticated distillationMore sophisticated distillation•• Physical separation stepsPhysical separation steps•• Chemical conversion stepsChemical conversion steps
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620 K
C1 - C4
Gases
Gasoline
Kerosene
Gas oil
ResidueCrude oil
steam
steam
steam
reflux water
Fractionator Stripper StripperFurnace
More sophisticated ???Higher T Higher T distillation distillation ????
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Modern Crude Distillation Unit
reflux water
vacuumsteam
Crude Oil
vacuum
Intermediate gas oil
Heavygas oil
Slops
Gases
Gasoline
vacuum residue
Kerosene
Lightgas oil
steam
Mainfractionator
Strippers Mild vacuumcolumn
Driers
circulating reflux
circulating reflux
FurnaceFurnace
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Propane DeasphaltingExtraction
ReasonReasonCokeCoke--forming tendencies of forming tendencies of asphaltenicasphaltenic materialsmaterials
How?How?Reduction by removal of suitable solventReduction by removal of suitable solvent
propane propane butane, pentanebutane, pentane
Why propane?Why propane? Conditions?Conditions? Flow scheme?Flow scheme?Easy separationEasy separationAvailableAvailable......
Modest temperatureHigh pressure
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Propane Deasphalting
Deasphalted oil
Vacuum residue
Liquid propane
Asphalt
Propane recycle
Flash drumDeasphalting tower Strippers
Steam
Steam
Condensers
Steam condenser
Water
Propane storage
Make-up propane
310 - 330 K35 - 40 bar
Steam
Propane evaporatorCond.
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Thermal Processes
Feedgasoilcoke
Furnace
T, tres
Visbreakingmild conditions
Delayed Cokinglong residence time (24 h)
Flexicokingcombination thermal cracking and coke gasification/combustion
Steam Crackingproduction lower olefins
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~ 10 wt%
~ 80 wt%
Heavy gas oil
Fractionator Vacuum fractionator
Gasoline
FlashReactor
Cracked residue
Light gas oil
730 K20 bar1-8 min
Furnace
Visbreaking
Vacuum residue
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UnstabilizedNaphtha
Gas
Furnace Fractionator
CokeFeed
Coke drums Gas oil stripper
Gas oil
2 bar
24 h
770 K
710 K
Delayed Coking
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Modern oil refinery
Crude oil
Straight run gasoline
LPG and Gas
Naphtha
Hydro-treating
Reformate
Middle distillates
Heavy atm. gas oil
Solventextraction
Lube base stocks
Gasoline
Vacuum gas oil
Solventdewaxing
Lube oils
Waxes
Gasoline, Naphtha, Middle distillates
Gasoline, Naphtha, Middle distillates
Gasoline, Naphtha, Middle distillates
Slurry oil
Refinery fuel gas
LPG
Gasoline
Solvents
Kerosene
Diesel
Heating oil
Lube oil
Greases
Asphalt
Industrial fuels
Coke
Trea
ting
and
Blen
ding
Delayed coker / Flexicoker
Propanedeasphalter
Hydro-treating
Catalyticreforming
Catalyticcracking
Visbreaker
Hydro-cracking
Fuel oil
Asphalt
LPG and Gas
Cycle oil
Alkylation AlkylateLPG
Hydro-treating
Vacu
umD
istil
latio
nAt
mos
pher
icD
istil
latio
n
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Octane Numbers, Boiling Points•• nn--pentanepentane 6262 309 K309 K•• 22--methyl butanemethyl butane 9090 301301•• cyclopentanecyclopentane 8585 322322•• nn--hexanehexane 2626 342342•• 2,22,2--dimethylbutanedimethylbutane 9393 323323•• benzenebenzene >100>100 353353•• cyclohexanecyclohexane 7777 354354•• nn--octaneoctane 00 399399•• 2,2,32,2,3--trimethylpentanetrimethylpentane 100100 372372•• methylmethyl--tertiarytertiary--butylbutyl--etherether 118118 328328
•• straight run gasolinestraight run gasoline 6868 67 (MON)67 (MON)•• FCC light gasolineFCC light gasoline 9393 8282•• alkylatealkylate 9595 9292•• reformate reformate (CCR)(CCR) 9999 8888
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Cetane Numbers•• nn--alkanesalkanes 100100--110110•• nn--hexadecane (cetane)hexadecane (cetane) 100100•• isoiso--alkanesalkanes 3030--7070•• alkenesalkenes 4040--6060•• cycloalkanescycloalkanes 4040--7070•• alkylbenzenesalkylbenzenes 2020--6060•• naphtalenesnaphtalenes 00--2020•• αα--methyl naphthalenemethyl naphthalene 00
•• straight run gas oilstraight run gas oil 4040--5050•• FCC cycle oilFCC cycle oil 00--2525•• thermal gas oilthermal gas oil 3030--5050•• hydrocracking gas oilhydrocracking gas oil 5555--6060
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Product DistributionThermal versus Catalytic Cracking
0
20
40
60
80
100
120
140
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Carbon Number
mol
per
100
mol
cra
cked
n-C
16 Thermal
Catalytic
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CH2 C CH3C+H3CCH3 CH3
CH3
H3C CCH3
CH2 + C CH3
CH3
CH3+
Catalytic Cracking•• World capacity: > 500 million metric ton/yearWorld capacity: > 500 million metric ton/year
•• Reactions:Reactions:–– CC--C bond cleavage:C bond cleavage:–– IsomerizationIsomerization–– ProtonationProtonation//deprotonationdeprotonation–– AlkylationAlkylation–– PolymerizationPolymerization–– CyclizationCyclization, condensation , condensation coke formationcoke formation
“β scission”
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+ H + o rC H C H 2R C H 2 C +RH
HR C + C H 3
H
Alkenes:
via carbenium ions
Stability: tertiary > secondary > primary > ethyl > methyl
+ H+ C +RH
HHC H3 + H2C H2 C H3R R C + C H3
H
Alkanes:
via carbonium ions
Or, if carbenium ions are present:
C H 2 C H 2 C H 3C +H 3CC H 3
H 3C C C H 2 C H 2 C H 2 C H 3
H
H
+
+
H 3C C C H 2 C H 2 C H 2 C H 3
H
C H 2 C H 2 C H 3C HC H 3
H 3C+
Cracking Mechanism
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+
H3C CH2 CH2 CH2 CH2 CH2 CH3
H3C CH CH3
CH3
H3C CH CH2 CH2 CH2 CH2 CH3
H3C CHCH2
CH CH3CH2CH2
H+
CH CH3H2C
H3C CH CH3
CH3
H3C CH CH CH2 CH2 CH3
CH3
+
hydride shifts +C-C bond breaking
hydride transfer
Isomerization
etc.
Protonated cyclopropane
Classical carbenium ion
Initation
n-Alkene
n-Alkane
iso-Alkane
+
+
Cracking Mechanism
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Mechanism: HMechanism: H++ donor or Hdonor or H-- acceptor acceptor acid sitesacid sites
Catalysts for FCC
OriginallyOriginally•• AlClAlCl33 solution:solution:
–– corrosioncorrosion–– waste streamswaste streams
SubsequentlySubsequently•• Clays (acidClays (acid--treated)treated)•• Amorphous silicaAmorphous silica--aluminaalumina
–– more stable and more selectivemore stable and more selective–– better pore structurebetter pore structure–– better attrition stabilitybetter attrition stability
•• ZeolitesZeolites–– even more active and stable (less coke, higher thermal stabilityeven more active and stable (less coke, higher thermal stability))
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4.5
5
5.5
6
6.5
7
1960 1965 1970 1975 1980 1985 1990 1995
Year
Feed
thro
ughp
ut (m
illion
bar
rels
/day
)Capacity required with amorphous catalysts(extrapolated)
Capacity with zeolitic catalysts(actual situation)
Catalytic Cracking Capacity in the US
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-
-
silica-alumina:
silica:
SiO
OO
Si
Si
Si SiO
OOO
Si
Si
SiOH H++
OO
O
Si
Si
SiO
OOO
Si
Si
Si H++Al HO Si Al Si
Weak acid
Strong acid
Cracking Catalysts
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• Large number found and/or synthesized
• Total porosity up to 0.5 ml/g
• Examples:
Supercage0.8 nm
Sodalite cage
FAU
SOD
LTA
Y (Faujasite)Zeolite A
Sodalite
Zeolites
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RECl3, NH4Cl
Wash liquor
Sodium silicate
Sodium aluminate
Water
NaOH
Al2O3 source
SiO2 source
Water
NaOH
Na zeolitecrystallization
Silica-aluminasynthesis
Filter Dryer
Mixer
Ion exchange
FCC catalyst particles
Spray dryer
Matrix material
Zeolite
matrixzeolite (dp = 2-10 µm)
50-70 µm
Micro pores < 3 nmMeso pores 3 - 50 nmMacro pores > 50 nm
Production of FCC catalyst
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Coke: carbon deposited
“Mixed Blessing”
• Catalyst poisoned
• Regeneration provides heat
0
20
40
60
80
100
1950s 1960s 1970s 1980s
% w
t on
feed
Gas
LPG
Gasoline
LCO
HCO/slurry
Coke
Amorphous ZeoliteLow Al High Al REY USY
Product Distribution of Gas Oil Cracking
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Cracking
C + O2→ CO / CO2
Air
Flue gas
Spent catalyst
Regenerated catalyst
Feed
To fractionation
970 K
775 K
SteamGrid
2-stage Cyclones
Regenerator Reactor
Riser
Fluidized bed
Fluidized bed
2-stage Cyclones
FCC: Fluidized-bed Reactor and Regenerator
Latermuch moreactive catalyst
Consequencesfor process?
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Modern FCC Unit: Riser Reactor
waste heat boiler
compression
expansion
catalyst fines
propane
propene
butane
butene
L/L sep.water
G/L sep.gas (C2 and lighter)
slurry oil
light cycle oil
heavy cycle oil
flue gas
spent cat.
regenerated cat.
steam
riser
steam
cyclones
FeedAir
Gasoline
Regenerator Reactor Fractionator Absorber Debu-tanizer
Depro-panizer
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0 20Time (s)
Cat
alys
t fra
ctio
n (a
.u)
Total area = 1
Riser Reactor: Plug flow Reactor??Residence Time Distribution ?
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Reactor Regenerator
Temperature (K) 775 973
Pressure (bar) 1 2
Residence time 1-5 s minutes/half hour
Typical Conditions in Riser FCC
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Sulfur Distribution in FCC Products
“product” % of sulfur in feed ton/day* S (SO2)H2Sliquid productscoke → SOx
50 ± 1043 ± 5 7 ± 3
83.671.911.7 (23.3)
•• Capacity: Capacity: 50000 barrels /day50000 barrels /day•• catalyst / oil ratio: catalyst / oil ratio: •• Catalyst inventory: Catalyst inventory: •• Catalyst Catalyst recirculationrecirculation rate: rate: •• feedstockfeedstock sulfursulfur content:content: 2 wt%2 wt%
6 kg/kg6 kg/kg500 ton500 ton50000 ton/day50000 ton/day
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Removal of SO2 in FCC unit
Is it possible to reduce emission of SOIs it possible to reduce emission of SO22 at low at low investment???investment???
•Change selectivity catalyst?•Add novel catalyst?•………………..
ClueSome sulphates stable under oxidation and unstable under reducing conditions
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Removal of SO2 in FCC unit
Oxidation of SO2 in regenerator and adsorption of SO3 on MO:
Reduction of metal sulfate in riser and release of H2S:
Regeneration of metal oxide in stripper with release of H2S:
2 SO2 + O2 → 2 SO3
SO3 + MO → MSO4Stable in oxidizing conditions
MSO4 + H2 → MSO3 + H2O
MO + H2Sor
MS + H2O
MS + H2O → MO + H2S
M: Ce, Mg,..
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Novel Developments in FCC0.51 - 0.55 nm
Production of light alkenes (CProduction of light alkenes (C33==, C, C44
==))–– addition of ZSMaddition of ZSM--55–– ApplicationApplication
»» petrochemical feedstockpetrochemical feedstock»» isobutene for MTBE, ETBEisobutene for MTBE, ETBE
Processing of heavier feedstocksProcessing of heavier feedstocks–– improved reactors, strippers, feed injection, gas/solid separaimproved reactors, strippers, feed injection, gas/solid separationtion–– application of catalyst cooling and high application of catalyst cooling and high TT
»» much higher coke production, metal deposits, more much higher coke production, metal deposits, more sulfursulfur
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Hydrotreating and HydrocrackingHYDROTREATINGHYDROTREATING•• Conversion with hydrogenConversion with hydrogen•• Reactions: hydrogenation &Reactions: hydrogenation & hydrogenolysishydrogenolysis•• Removal of heteroRemoval of hetero--atoms (S, N, O)atoms (S, N, O)•• Some hydrogenation of double bonds & Some hydrogenation of double bonds &
aromatic ringsaromatic rings•• Molecular size not drastically alteredMolecular size not drastically altered•• Also termedAlso termed hydropurificationhydropurification
HYDROCRACKINGHYDROCRACKING•• Similar to hydrotreatingSimilar to hydrotreating•• But, drastic reduction in molecular sizeBut, drastic reduction in molecular size
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Objectives Hydrotreating
•• Protection of the environmentProtection of the environment–– reduction acid rainreduction acid rain
•• Protection of downstream catalystsProtection of downstream catalysts–– in further processingin further processing–– SS--compounds in Diesel fuel give difficulties in catalytic compounds in Diesel fuel give difficulties in catalytic
cleaning of exhaust gasescleaning of exhaust gases
•• Improvement of gasoline properties Improvement of gasoline properties –– odour, colour, stability, corrosionodour, colour, stability, corrosion
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Hydrotreating Reactions
5) Phenols
4) Pyridines
3) Benzothiophenes
2) Thiophenes
1) Mercaptans
5
5
3
RSH +
+
+
+
+
+
+
+
+
H2
H2
H2
H2
H2
RH
S
S
H2S
H2S
H2S
+ NH3
H2O
N
OH
HDSHDS
HDSHDS
HDSHDS
HDNHDN
HDOHDO
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0 1 2 3 4 5
1000/Temperature (1/K)
0
10
20
30
40
50
60
70
80
90
100
S
S
CH3SH
lnK e
q
Industrial conditions600-650 K
Equilibrium data
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Naphtha Gas Oil� Temperature (K): 590 - 650 600 - 670� Pressure (bar): 15 - 40 40 - 100� H2/oil (Nm3/kg): 0.1 - 0.3 0.15 - 0.3 � WHSV (kg feed/(m3 catalyst)/h) 2000 - 5000 500 - 3000 � Catalyst: mixed metal sulfides (CoS and MoS2 or NiS and WS2
on Al2O3)
γ-Al2O3
‘CoMoS’S
CoMo
Typical process conditions
Process design ???
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Inert beads
Catalyst bed
Distributor
Support grid
Product
Gas + liquid
Catalyst particle with liquid film
Gas
DeflectorGas
Liquid
Complete wetting
Incomplete wetting
Trickle-bed Reactor
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steam
Hydrogen
hydrogen recycle to H2S removal
Sour water
Product
SeparatorStripperHot HP separator
ReactorFurnace
Gas (C3
-)
Recycle gas scrubbing
NaphthaCold HP separator
H2S
water
Hot LP separator
Hydrotreating Process (trickle bed)
Feed
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Development of maximum Sulfur Content in automotive Diesel in Europe
Year
1 2 3 4
3000
500 35050
0
500
1000
1500
2000
2500
3000
3500
1996 2000 2005< 1996
Max S in Dieselppm
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Activity of Various Catalysts for HDS ofPretreated Gas Oil
CoMo/γ-Al2O3260 ppm
NiW/γ-Al2O3
PtPd/ASA (I)
Pt/ASA
Feed 760 ppm
NiMo/γ-Al2O3230 ppm
200 ppm
140 ppm
60 ppm
S
CH3
S
CH3
SCH3
C2H5
SCH3
Retention time
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1
10
100
1000
10000
0 0.5 1 1.5 2
FCC feedstock sulfur, wt.%
FCC
gas
olin
e su
lfur,
ppm
w
untreated feed
FCC feedstock sulfur, wt.%
FCC gasoline S
ppmw untreated feed
Effect of HDS of FCC feedstock on gasoline sulfur content