Cracking process

Contents :
Thermal Cracking
------------- Steam Cracking
------------- Thermal Cracking process to produce gasoline
------------- Thermal Reforming
------------- Visbreaking
------------- Coking
Catalytic Cracking
Hydrocracking

Definition
 All hydrocarbon decomposition reaction
 In oil industry Heavy hydrocarbons with high boiling
point of 200 ° c
 Decomposition of a gas or a light cutting oil

• 1941: Standard Jersey developed the world’s first steam
cracker at Baton Rouge.
• In 1891 The thermal cracking
method was invented.
• modified in 1908
• In 1934 factory of Shukhov cracking
process established at Baku, USSR.
William Burton
Vladmir Shukov

• In 1923 The catalytic cracking
method was invented
• In 1942 FCC method was invented
In Burton Rouge Refinery
Companies:
• EXXON
• UOP
• M.W.KELLOGG

Thermal cracking
 The processes is which hydrocarbons are decomposed
at elevated temperatures to from material of lower
Mol. Wt

Thermodynamic
 Chart thermodynamic stability of
hydrocarbons
Hydrocarbons are unstable with respect to
the elements at any temperature
Unsaturated hydrocarbons to the
corresponding saturated hydrocarbons are
only stable at high temperatures.
The stability of these compounds is reduced
with longer hydrocarbon chain.
Increasing the molecular weight reduction of
thermal stability
stability Paraffin < olefin< naften
<aromatics.

PARAFIN
OLEFIN
Naphthene
aromatic
stability
OLEFIN
naphthen
aromatic
PARAFIN
Cracking activity
molecular weight
thermal stability

Kinetics
Reaction
Parameter
pressure
temperature
residence time
Thermal cracking conversion increases with temp. and residence time
Under very severe thermal cracking conditions, there is tendency for
coke formation

Cracking goal
Increase the value of a product
change to a widely used products
production of Rare-market products.
Improve the quality of a product

Steam cracking
 In the process of steam cracking of thermal decomposition
(pyrolysis) of saturated hydrocarbons (natural gas and oil cut)
is done in the presence of water vapor.
 Production of unsaturated hydrocarbons such as ethylene
and propylene and butane
 Products, raw material is petroleum.

 A wide variety of feed used for pyrolysis
 United States natural gas (ethane , propane)
 European countries and Japan cutting crude oil
Feed

53
27.9
7.5
5.7
4 1
0.1
World ethylene feedstock in 2011
naphtha
ethane
propane
gas oil
butane
ref gas
other

Chemistry of steam cracking
Propagation
Initiation
Termination
𝐶𝐻3 − 𝐶𝐻3 𝐻3 𝐶0 + 𝐻3 𝐶0
𝐻3 𝐶0 + 𝐶𝐻3 − 𝐶𝐻3 𝐶𝐻4 + 𝐻3 𝐶 − 𝐶0 𝐻2
𝐻3 𝐶 − 𝐶0 𝐻2 𝐻2 𝐶 = C𝐻2 + 𝐻0
𝐻0 + 𝐻3 𝐶 − 𝐶𝐻3 𝐻2 + 𝐻3 𝐶 − 𝐶0 𝐻2
𝐻3 𝐶 − 𝐶0 𝐻2 etc.
𝐻0 + 𝐻0 𝐻2
𝐻3 𝐶 − 𝐶0 𝐻2 + 𝐻3 𝐶0 𝐻2 𝐶 = 𝐶𝐻2 + 𝐶𝐻4
etc.

Motivation for steam cracking
The worldwide
demand and
production of
olefins…
Currently, production
through steam cracking
1. 94% of the world propylene.
2. In Western Europe, 95% of
`````ethylene and 70–75% of
111propylene.
3. In Asia, 61% of ethylene.
*source-2011-november_Olefinek eloallitasa.pdf

• Overall a cracking process consists of two main components
 Hot Section Pyrolysis
 Cold Section Products, separation and purification
Quench &
Heat Recovery
Steam Cracker
Furnace
Compression Refrigeration Fractionation
Cracked Products
ProductsFeed
Fuel

Process of steam cracking
Pyrolysis section
Fractionation and
Compression Section
Product recovery and
Separation Section
Naphtha

• designed to
increase quickly
temperature of
feed
• Tubes must be
resistant to
corrosion and high
temperatures.
• The quenching
operation, heat is
recovered.
Furnace

Thermal flux
(Kcal / m². h)
Conversion
(%)
Mass flow
(Kg / m². s)
FeedInternal diameter of
pipe(mm)
20000 – 2500050 – 60110 – 130Ethan100
12000 – 1500070 – 85130 – 140propane100
9500 – 1200075 – 90140 – 160butane100
9500 – 1200050 – 58120 – 130Gasoline115

Pressure(Kg / cm²)Temperature(° C)Productfeed
.2 - .51000 – 1400AcetyleneEthan
.2 – 2800 - 850EthyleneEthan
.2 – 2770 - 800Propylene , EthylenePropane , butane
.5 - 2720 - 770Propylene , EthyleneLight Gasoline
.5 - 2720 - 750Propylene , EthyleneLight Gas oil

Separation
section
Ethylene (24%)
Propylene(20%)
Butadiene(3%)
BTX(1%)
Petroleum
ether(25%)
Products from separation
section

Energy analysis in steam cracking
sections
Section Energy required Energy loss
pyrolysis 65% 75%
fractionation and
compression
15% 25%
recovery section 20% 15%
“ Steam cracking is the most energy-consuming process in
the chemical industry and globally uses approximately 8% of
the sector’s total primary energy use.”

enter heat through steam injection
Reduce heat flux per meter of pipe
Help to de-cokeing
Increase reaction volume and
investment for furnace
Create units to separate water from
products

Thermal Cracking
------------- Steam Cracking
------------- Thermal Cracking process to produce gasoline
------------- Thermal Reforming
------------- Visbreaking
------------- Coking
Catalytic Cracking
Hydrocracking

Thermal Cracking process to
produce gasoline:

Intensity of operation :
Temperature
Time
Pressure

Thermal Reforming
Thermal reforming means cracking of gasoline in order to improvement of
“Octane Number” & increase it’s “volatility”
It work @ a classic system at Extreme operating conditions :
• P =20 to 70 Kg/cm²
• T = 510 ͦᶜ to 580 ͦᶜ
• No Reflux

Visbreaking
The viscosity reduction is a relatively mild thermal cracking to
reduce viscosity and pour point is used.
The aim is to reduce the viscosity of the fuel, without any significant
change in its stability.
The main cause of high viscosity is long paraffin chains attached to
aromatic rings.
Intensity of cracking is low

Reactions:
• Break off the chains of cyclo-paraffin and aromatic
• Gum converts to light hydrocarbons
• Naphthenic rings Cracking @ T>900 °F
Operations :
Furnace
Soaker
TemperatureResidence timeStop unitFuel used
Furnace890-9301-3 min3-6 month
%80 of
operation costs
soaker800-830More than 3min6-18 month
%50 of
operation costs
Visbreaking

A unit of reduce viscosity (Soaker))
Visbreaking

Coking
Convert heavy cuts to coke &…
coke
Methods
Sponge coke
Needle coke
Shot coke
Delayed Coking
Fluid Coking
Flexicoking

Coking -> Delayed Coking
Accumulator
Fractionator
Naphtha
Gas
P/A
Steam Stripper
Steam
Light gas oil
Steam Heavy
gas oil
Feed
Steam Gen.
Condensate
Drum
Coke
Heater
Decoking
Waterjet
Coke Drum

Coking -> Fluid Coking
Is newer than delayed coking
Produce powder coke

Catalytic Cracking
in Refining Industry
A

Introduction:
•E Houdry began his studies on catalytic craching & an
industrial unit was built in the U.S. in 1936
•Most important process since 1940 that mainly used for
the production of gasoline from high boiling
temperature such as heavy distillate ,olefinic light
hydrocarbons , gas oil,…
•Production of 45% gasoline in the world

Catalytic Cracking vs
Thermal Cracking:
• Better selectivity in the cracking operation gives less of the light-end
substance
• More isomerization of the olefins occurs
• Saturation of the double bonds is better controlled
• Diolefin production is less
• Aromatic production is better
• Coke is formed more economically
• Ability to tolarete high-sulfur charge increase

• Production of methane & ethane is less
• Production of propane & butane is more
• The formation of heavier oil & tars is minimized
• In the catalytic cracking hydrocarbons crack 50-60 time
rapidly than no catalytic operations

Operation Variable:
• PRESSURE :AT 25 psig
• TEMPERATURE: 860-968 F in Reaction &
• 1000-1300 F in Regeneration
• Space Velocity
• Catalyst to oil ratio

Parts of catalytic cracking:
• 1-CRACKING
• 2-REGENERATION
• 3-FRACTIOANATION

Reactors in Cat cracker:
• 1.FIXED BED REACTOR
•2.MOVING BED REACTOR
• 3.FCC OR FLUID CATALYTIC CRACKING

Fixed bed reactor:
Disadvantage! :
• Complete vaporization of feed
• Equilibrium never is reached
• Temperature variation!

Moving bed reactor(TCC):
Condition Operation:
• 10 psig Pressure
• 850-925 F

FCC:
• 1 IV…..Exxon research
• 2 Uopfluid Catalytic Cracking
• 3 Texaso Fluid Catalytic Cracking

For the first time, Farben company applied Hydrocracking method for gasoline
producing and it has been very conventional process, recently. because :
gasoline
consumption
hydrogen
price

the most important property of hydrocracking is high hydrogen
pressure.
Hydrogen
influences
Catalyst
activity
and
selectivity
coking
branched
alkanes

reactions :
1) Chain breaking (simple hydrocracking reaction)
2) De-alkylation
3) Ring breaking
olefins and aromatics hydrogenation reactions occur
In Hydrocracking but these are not main reactions.

Thermodynamic studies :
Type of reaction heat of reaction(400C)
a) Hydrocracking
1) paraffins
2) naphthenes
3) aromatics
Kcal/mol
11-14
10-12
10-11
b) Hydrogenation
1) olefins
2) aromatics
27-31
48-52

Kinetics studies :
hard operating conditions
-ring breaking
occurs just after hydrogenation
branched hydrocarbon
Iso-alkane production increasing
naphthenes

Kinetics studies :
-rate of reaction and feed molecular weight relationship

Catalyst :
metal : Pt , Al , Pd , W , Ni
Catalyst
acid-base : silicon-aluminum (crystal or zeolite)
Catalyst activity is reduced by coke , Nitrogen and Sulfur composition.

Methods
Two basic methods for Hydrocracking:
1) Fixed Bed Catalytic Hydrocracking
2) Fluidized Bed Hydrocracking

Methods
company Method
Standard Oil Co. and U.O.P (Isomax)
Union Oil Co. (Unicracking)
Exxon Research and Engineering (G. O. Fining)
Gulf Oil Co. and houdry Process (H. G. Hydrocracking)
Texaco (H – Oil) F.B.Hc
C – E Lummus (LC – Fining) F.B.Hc
Shell Development Co. (Shell)
Badische Anilin and institute Francais du Petrole (BASF – IFP Hydrocracking)
U.O.P (Unibon)

Methods
main equipment sections for Hydrocracking :
a) Reaction section with one (or two) reactor.
b) Separation section with separator or stabilizer columns
Reaction Separation

Fixed Bed Catalytic Hydrocracking
Tow processes are defined for this purpose:
Single-stages
feed is heavy
Fresh feed have no poisoning
impurities
Production are Gasoil and jet fuel
Two-stages
More flexible than
single-stage
Desulfurization and
denitrogenation in first
stage

Fluidized Bed Hydrocracking
‘H – Oil’ and ‘LC – Fining’ processes
Fluidized bed Hydrocracking is designed for heavy feed.
Pressure is approximately 200atm.
Depends on feed and rate conversion, temperature is between 420-450 C.
The great advantage of this process : catalyst utilization

Operating parameters
1) Temperature
2) Pressure
3) Volume space velocity
space velocity refers to the quotient of the entering volumetric flow rate of
the reactants divided by the catalyst bed volume.

Hydrogen consumption
Feed molecular weight
Production molecular weight Hydrogen consumption
Percentage of Sulfur in feed
Consequently

Productions
Generally, hydrocracking is a process as purpose of gasoline, gasoil and jet
fuel producing.
In the USA, it is based on gasoline production and in Europe, it is based on
jet fuel and gasoil production.

Cracking process

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