Alkylation is a process for chemically combining
isobutane with light olefinic hydrocarbons, typically
C3 and C4 olefins, (e.g.propylene, butylene) in
the presence of an acid catalyst, usually sulphuric
acid or hydrofluoric acid. The product, alkylate
(an isoparaffin) has a high-octane value and is
blended into motor and aviation gasoline to improve
the antiknock value of the fuel.
The light olefins are most commonly available
from the Catalytic crackers.
Alkylate is one of the best gasoline blending
components because it is a clean burning, very
low sulphur component, with no olefinic or aromatic
compounds and with high octane and low vapour
The Indian scenario is unique, in that on the
one hand, the relative gasoline consumption is
much lower vis a vis the developed counter parts,
on the other hand, the C3 and C4 components, which
are otherwise used in alkylation as a feedstock,
offer much higher value alternative, i.e. LPG.
LPG is in large deficits in India, and to meet
its demand, Reliance's configuration is designed
to maximize the production of LPG. Hence the processing
scheme currently does not include Alkylation.
Bottom of the Barrel Processing
"Bottom of the barrel" is a term used
to refer Vacuum residue (VR) boiling above 5650C.
It is produced from bottom of the Vacuum Distillation
Column. Traditionally this material, high in sulphur,
asphaltenes and metals has been blended into heavy
or industrial fuel oil.
Outlets for high sulfur fuel oil are becoming
increasingly scarce, with stringent emission norms
for SOx and NOx . In the most parts of the world,
increasing switch over from heavy fuel oil to
clean combustion natural gas for power generation
is already evident. The process of displacing
high sulfur fuel oil is expected to gather further
momentum as further switching from fuel gas to
natural gas takes place for environmental and
There are several options for the bottom-of-the
barrel processing including Delayed Coking, Visbreaking
and Resid Desulfurization. Reliance has selected
Delayed Coking for upgrading the "bottom
Catalytic cracking is a process which breaks
down the larger, heavier, and more complex hydrocarbon
molecules into simpler and lighter molecules by
the action of heat and aided by the presence of
a catalyst but without the addition of hydrogen.
In this way, heavy oils (fuel oil components)
can be converted into lighter and more valuable
products (notably LPG, gasoline and middle distillate
components). The catalytic cracking unit is known
as the Fluidized Catalytic Cracking or FCC.
The FCC is the most widely used secondary conversion
process in the refinery industry. Traditionally,
the FCC units have been operated on either the
maximum gasoline mode or the maximum distillate
mode, dependent largely on the seasonal product
Of late, a third mode is gaining importance,
that of a maximum olefin mode which maximizes
LPG, propylene and butylene. In India, FCC in
the max olefin mode is suitable for maximum value
addition because LPG and propylene are among the
highest value petroleum products. Reliance operates
the Jamnagar FCC in the max olefin mode, to maximize
LPG and propylene. FCC in the max olefins mode
also produces isobutylene which can be used for
MTBE, isobutane and butylene which can be processed
into alkylate and isoamylene which can be used
for TAME. MTBE, Alkylate and TAME are principal
gasoline additives used to improve gasoline quality.
Reliance utilizes the isoamylene from the FCC
as a feedstock to produce TAME in the Jamnagar
The FCC feed is also known as vacuum gas oil
(VGO) because it is generally a product from the
Vacuum Distillation Column. The FCC feed can be
of three types:-
- Hydrotreated VGO
- VGO mixed with VR (Process is known as Resid
FCC or RFCC).
The VGO material for the FCC feed is generated
from the Vacuum Distillation Column in the CDU/VDU
and from the Coker.
Delayed Coking is a high severity "Bottom
of the barrel processing" scheme by which
heavy crude oil fractions can be thermally decomposed
under conditions or elevated temperatures to produce
a mixture of lighter oils and petroleum coke.
The light oils can be processed further in other
refinery units or blended into products. The coke
can be used either as a fuel or in other metallurgical
applications such as the manufacturing of steel
The Delayed Coking process achieves approximately
70% of residue conversion to lighter products
compared to only about 30% in Visbreaking. Reliance
has selected Delayed Coker to maximize conversion
to higher products.
Reliance, with a large Delayed Coker to handle
100% of Vacuum Residue, is able to achieve much
higher value addition and "zero fuel oil
Distillation (Atmospheric and Vacuum)
This is the first stage in the refining for
separating crude oil components at atmospheric
pressure by heating, and subsequent condensing,
of the fractions (unfinished petroleum products)
by cooling. Distillation under reduced pressure
(less than atmospheric) i.e. Vacuum Distillation
lowers the boiling temperature of the liquid being
distilled permitting the production of distillates
at lower temperature than would be necessary in
atmospheric distillation, thus avoiding coke formation.
The Jamnagar Refinery has a combined Crude Distillation
Unit / Vacuum Distillation Unit (CDU / VDU) to
separate the crude oil into primarily fractions
of LPG, Naphtha, Kerosene, Gasoil, Vacuum Gas
Oil and Vacuum Residue. The combined CDU/VDU maximizes
energy integration to minimize the energy required
for primary separation.
Hydrotreating is used for treating petroleum
fractions in the presence of catalysts and substantial
quantities of hydrogen. Hydrotreating results
in desulphurisation, (removal of sulphur), denitrification
(removal of nitrogen compounds) and conversion
of olefins to paraffins.
Reliance has the highest Hydrotreating Capacity
relative to crude distillation which enables it
to produce world class products and high value
Oxygenates are ethers which are used as gasoline
additives to improve the gasoline. Two principal
oxygenates are Methyl Tertiary Butyl Ether (MTBE)
and Tertiary Amyl Methyl Ether (TAME).
Reforming Process rearranges hydrocarbon molecules
in the naphtha (or naphthatype) feed, thereby
converting paraffinic and naphthenic type hydrocarbons
into aromatic type hydrocarbons, suitable for
blending into finished gasoline. Since its product,
reformate, is richer in aromatics than its feed,
naphtha, this process is also used to produce
aromatic petrochemicals (Benzene, Toluene and
The Reforming process requires high temperature
and catalyst to facilitate the reaction.The Reforming
catalyst contains Platinum. The Platinum based
catalyst has to be protected and hence reformer
feed has to be sulphur free.
In this process, heat and pressure are used
to break down, rearrange, or combine hydrocarbon
molecules. Thermal cracking includes vis-breaking,
delayed coking, fluid coking, and other similar
Vis-breaking is a relatively mild thermal cracking
process in which heavy atmospheric or vacuum-distillation
bottoms are cracked at moderate temperatures to
make light products and produce a lower viscosity
residue than the initial feed to the unit.
Vis-breaking process achieves about 30% of residue
conversion to lighter products. Vis-breaking is
one of the least costly upgrading processes, and
is common where there is still a relatively large
use of heavy fuel oil. But with the problems of
surplus fuel oil compounding the world over, the
importance of this process is expected to decline.
Sweetening The petroleum products should be free
of mercaptans (a form of sulphur compound) because
otherwise it emits foul odour on burning. Sweetening
is a process of mercaptan removal by oxidation.
This sweetening process is also better known by
the patented process name of Merox or mercaptan
oxidation. Reliance has 4 sweetening units to
remove mercaptans from :-
- Saturated LPG
- Unsaturated LPG