These are process which are used for the processing of liquid fuel.

1. VISBREAKING
AND
DELAYED COKING
Submitted To: Submitted By:
Mr. KL Chauhan Sanyam Jain (13759)
Devendra Poonia (13760)
Boby Kumar (13758)

2. Content:-
Visbreaking
1.Introduction
2.Process Description
3.Purpose
4.Classification of Visbreaking
5.Coil visbreaking
6.Soaker visbreaking
7.Difference between Coil and Soaker Visbreaking
8.Problems encountered in visbreaking
9.Solutions of problems

3. Introduction:
A visbreaking is a processing unit in oil refinery that converts
atmospheric or vacuum residues via thermal cracking to gas, naphtha, distillates
and visbroken residues.
In other words, A visbreaker thermally cracks large hydrocarbon
molecules in the oil by heating in a furnace to reduce its viscosity to produce
small quantities of light hydrocarbons(LPG and Gasoline).

4. Purpose:
1.To reduce the quantity of residual oil produced in the distillation
of crude oil.
2.To increase the yield of more valuable middle distillates(heating
oil and diesel).
3.To reduce the pour point and viscosity of waxy residues used for
blending with lighter fuel oil.
4. Viscosity is reduce by :
a. Vaccum distillation
b. Hydro skimming
5.Increase the proportion of middle distillates in the refinery output. Middle
distillate is used as diluent with residual oils to bring their viscosity down
to their marketable level.

5. A schematic diagram of a Visbreaker unit
( Reference- Visbreaking- Chemical Engineering Process)
Visbreaker Unit

6.  Process Description:
• The process name of visbreaker refers to the fact that the process reduces i.e.
breaks the viscosity of the residual oil.
• The process is mild form of thermal cracking that significantly lowers
the viscosity of heavy crude oil without affecting the boiling point.
• The process is non-catalytic.

7. Aromatic
hydrocarbons Resins
AsphaltenesParaffinic
hydrocarbons
Vacuum residue fed
Vacuum residue fed to a visbreaker can
be considered to be composed of the
following:
• Asphaltenes: Large polycyclic molecules
that are suspended in the oil in a colloidal
form.
• Resins: Also polycyclic but of a lower
molecular weight than asphaltenes
• Aromatic hydrocarbons: Derivatives
of benzene, toluene and xylenes
• Paraffinic hydrocarbons: Alkanes

8. Classification of Visbreaking
Visbreaking
Coil
Visbreaking
Soaker
Visbreaking

9.  Coil visbreaking:
The term coil (or furnace) visbreaking
is applied to units where the cracking
process occurs in the furnace tubes
(or "coils").
Charge is fed to the visbreaker heater
where it is heated to a high temperature,
causing partial vaporization and mild
cracking.
A schematic diagram of a Coil Visbreaker unit
( Reference- Wikipedia)

10. The heater outlet stream is quenched
with gas oil or fractionator bottoms to
stop the cracking reaction.
The vapor liquid mixture enters the
fractionator to be separated into gas,
naphtha, gas oil and visbroken tar.
The visbroken bottoms are then blended
with lighter materials (cutter stock) to
meet fuel oil specifications.
The fractionated visbreaker gas oil is
often used as the cutter stock.
A schematic diagram of a Coil Visbreaker unit

11.  Soaker visbreaking:
In soaker visbreaking, the bulk of
the cracking reaction occurs not in
the furnace but in a drum located
after the furnace called the soaker.
Here the oil is held at an elevated
temperature for a predetermined
period of time to allow cracking to
occur before being quenched.
The oil then passes to a fractionator.
In soaker visbreaking, lower temperatures
are used than in coil visbreaking.
A schematic diagram of a Soaker Visbreaker unit
(Reference- Wikipedia)

12. Coil Visbreaking vs Soaker Visbreaking
Coil Visbreaking
(Low Residence time Cracking)
• Coil visbreaking is applied to the cracking
process units where cracking process occur in
a furnace tube.
• The higher temperatures are used in
coil visbreaking.
• .De-coking: In this petroleum coke deposits in
the tube of the furnace and leads to fouling
or blocking of the tubes.
Soaker Visbreaking
(high residence time cracking )
• In this bulk cracking reaction occur not in the
furnace but in a drum located after the
furnace.
• the lower temperatures are used in Soaker
visbreaking.
• The same will occur in the drum of a soaker
visbreaker, though the lower temperatures
used in the soaker drum leads to fouling at
a much slower rate.

13. Problems in visbreaking:
1.Fouling: It is the accumulation of unwanted material on solid surfaces to the
detriment of function.
.
2.Formation of coke: The formation of coke normally starts at temperatures
>300°C,and is therefore a major problem.
3.Asphaltenes precipitation: Asphaltenes makes precipitation with i-octane.
.

14. Solution of the problem:
High pressure spiral heat exchanger(HPSHE):
• Lower costs the unique self-cleaning effect in an Alfa Laval high pressure spiral
heat exchanger (HPSHE) can avoid fouling and ensure long operation times.
• The HPSHE is designed for pressures up to 100 bar(g).
• Lower internal volumes result in shorter residence times which helps avoid
asphaltene precipitation.
• There is no fouling, there is no extra heat required in the furnace. This leads to
no extra fuel consumption required in the furnace and much less production
downtime.

15. Content:
 Delayed Coking
1.What is coking
2.Types of coking
3.Delayed coking
4.Process Description

16. What is coking?
 Coking is a well-known process in the refining industry, the objective of
which is to upgrade heavy fractions and, more especially, the distillation
residues by subjecting them to heat decomposition.
 The residual products of the refinery form the feed for coking.
 The liquid feed is converted into gas, naphtha, heating oil, gas oil and
coke.
 Coking is done to get either gas oil or coke as the main product.
 The gas oil is used as the feed for catalytic cracking .
 While the coke used as a fuel or in the production of carbon electrodes
and chemicals.

17. Main types of coking processes.
1. Delayed coking – continuous thermal cracking process which generates coke
and produces various distillates in fractionator from vacuum residue. Coke
drum temperature remains around 415 °C –450 °C.
2. Fluid coking - continuous coking process where residue is sprayed on to
fluidised bed of hot coke particles. Here cracking takes place at much higher
temperature than delayed coking (temperature up to 565 °C).
• Both are physical processes that occur at pressures slightly higher than
atmospheric and at temperatures greater than 900oF that thermally crack the
feedstock into products such as naphtha and distillate, leaving behind
petroleum coke.

18. DELAYED COKING
A delayed coking is a type of coking whose process consists of
heating a residual oil feed to its thermal cracking temperature
in a furnace with multiple parallel passes.
Delayed coking is one of the unit processes used in many oil
refineries.
This cracks the heavy, long chain hydrocarbon molecules of the
residual oil into Coker gas oil and petroleum coke.
Delayed Coking is the most commonly used carbon rejection process
that upgrades residues to a wide range of lighter hydrocarbon gas
and distillates through thermal cracking.

19. DELAYED COKING
 The by-product of delayed coking process is petroleum coke.
 The goal for delayed coking operation is to maximise the yield of
clean distillates and minimise the yield of coke.
 Three operating parameters govern the yield pattern and product
quality of Delayed Coking are –
I) Temperature
II) Pressure
III) Recycle Ratio (RR)

20. Delayed coking

21.  In delayed coking, two or more large reactors, called coke drums, are used to
hold, or delay, the heated feedstock while the cracking takes place.
 Residual oil from the vacuum distillation unit is pumped into the bottom of the
distillation column called the main fractionator.
 The residual oil by having it contact the hot vapours in the bottom of the
fractionator .
 From fractionator it is pumped along with the some injected steam into the
fuel fired furnaces and heated to its thermal cracking temperature.
 The injection steam helps to minimize the deposition of coke with in the
furnace tubes.
 The heated stream transferring to coking drum where the temperature and
pressure are maintained at coking conditions so that stream decompose into
coke and volatile components.
Process description

22.  The process is called delayed coking because in this process the coal is heated
using a much more complex system , and it consists of multiple furnaces or coke
drums.
 The Coker fractionating system separates the volatile components generated in
the coking drum into various lighter hydrocarbon streams and components.
 After coking, the coke drum is full of coke and it is then removed using water
jets .
 Like other secondary processing units, coking play an important role in refinery
economics depending on the type and cost of the crude oil run at a refinery.
 Decoking - Process for the removal of coke from a coking reactor of a series of
coking reactors, comprising the projection of water under pressure at the coke
via a water-ejection device hanging from a flexible tube guided by a guide
pulley movably mounted above the reactors for translation between each
reactor of the series of reactors.

23. Thank you