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Catalytic Cracking^ Catalytic Cracking

Chapters 6 Chapters 6

Petroleum Refinery SchematicPetroleum Refinery Schematic

Light Naphtha

CrudeOil

Desalter

GasSeparation &Stabilizer AtmosphericDistillation VacuumDistillation

SolventDeasphalting Visbreaking^ Coking

FluidizedCatallyticCracking

Hydro-cracking NaphthaReforming

Isom-erization

Sat GasPlant

Polymer-ization Alkylation

NaphthaHydro-treating

Treating &Blending

Coke

Fuel Gas^ LPG^ AviationGasoline AutomotiveGasoline Solvents Jet Fuels Kerosene Solvents Heating Oils^ Diesel ResidualFuel Oils Asphalts Lubricant^ Greases^ Waxes

HeavyNaphtha

Kerosene

Distillate

AGO LVGO HVGO

Vacuum Residuum

CatDistillates

Gas OilHydro-treating^ DAO

Isomerate

Gas

AlkylFeed

Gasses PolymerizationNaphtha Alkylate

Butanes

LPG

Reformate^ Naphtha Fuel Oil Bottoms

Distillates

DistillateHydro-treating

CatNaptha Cycle Oils SDABottoms

CokerNaphtha

CokerGas Oil

SulfurPlant^

Sulfur

Naphtha^ Fuel Oil

SolventDewaxing

Lube Oil^ Waxes

PurposePurpose

•^

Crack carbon-carbon bonds in gas oils^ »

Fine catalyst in fluidized bed reactorallows for immediate regeneration »^

Lowers average molecular weight &produces high yields of fuel products »^

Produces olefins

•^

Attractive feed characteristics^ »

Small concentrations of contaminants

Poison the catalyst

»^

Small concentrations of heavyaromatics

Crack & deposit coke on catalyst

•^

Products may be further processed^ »

Further hydrocracked »^

Alkylated to improve gasoline anti-knock properties

Characteristics of Petroleum ProductsCharacteristics of Petroleum Products

FCC ComplexFCC Complex

Ref: http://www.osha.gov/dts/osta/otm/otm_iv/otm_iv_2.html

FCC Riser/Regenerator CombinationFCC Riser/Regenerator Combination

Refining Overview – Petroleum Processes & Products

,

by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000

Fluidized Catalytic CrackingFluidized Catalytic Cracking

•^

Up-flow dense phase particulate solid process credited to W.K. Lewis, MIT

-^

Originally developed as the Winkler coal gasification process^ »

Standard Oil of New Jersey, Standard Oil of Indiana, M.W. Kellogg, Shell Oil,The Texas Company, & others

•^

Dense phase – back mixed reactor^ »

Model I FCCU at Standard Oil of New Jersey’s Baton Rouge Refinery, 1942 »^

Model II dominated catalytic cracking during early years

Designed before first Model I operating

•^

Dilute phase — riser reactor design^ »

Catalysts based on molecular sieve – 1960s »^

Significantly higher cracking activity & gasoline yields – lower carbon oncatalyst »^

Plug flow – drastically reduced residence time & 90% feed conversions

Development of Catalytic CrackingDevelopment of Catalytic Cracking

-^

In 1960s catalysts based on molecular sieve were offered^ »

Significantly higher cracking activity & gasoline yields at lower overallcarbon on the catalyst

-^

These catalysts made the new dilute phase — riser reactor designpractical^ »

Utilized plug flow configuration allowing drastically reduced residencetime & feed conversions to 90%.

FCC ProductsFCC Products

FCC ProductsFCC Products

Primary goal to make gasoline & diesel whileminimizing production of heavy fuel oil“Cat gasoline” contributes largest volume to thegasoline pool•Front end rich in olefins & sulfur•Back end highly aromatic, high in sulfur, withsome olefins•Does not contain much C-6 & C-7 olefins – veryreactive & form lighter olefins & aromatics

FCC ProductsFCC Products

Light ends contain large amounts of olefins•Good for chemical feedstock•Can recover chemical grade propylene &ethylene•Propylene, butylene, & C5 olefins can bealkylated for higher yields of high-octanegasoline

FCC ProductsFCC Products

Little cat kerosene or jet fuel•High sulfur content•Low centane number because of aromatics –lowers quality diesel pool

Product YieldsProduct Yields

-^

Produces high yields of liquids & small amounts of gas & coke^ »

Mass liquid yields are usually 90%-93%; liquid volume yields are oftenmore than 100% »^

(Rule of thumb) Remaining mass yield split between gas & coke

-^

The yield pattern is determined by complex interaction of feedcharacteristics & reactor conditions that determine severity ofoperation^ »

Rough

yield estimation charts given in text pp. 117-130 pp. 144-

-^

Conversion defined relative to what remains in the originalfeedstock boiling range

(^

)

Conversion

Gas Oil Yield

Use of Yield ChartsUse of Yield Charts

Coke Total

LCO HCO

Cycle Oils

Gasoline

C3 C3= IC4 NC4 C4=s

LPG

Fuel Gas

Density

Wt%

Vol%