REFINING PROCESS OF CRUDE OIL

“PRODUCTION OF GASOLINE “

Refining
A petroleum refinery is a processing plant that converts crude oil into a mix of different
finished petroleum products.
There are four main steps in the oil refining process.

 The most basic and common step is distillation, where crude oil is separated into its
component parts or distillation cuts. This is typically done in a two-stage
process: atmospheric distillation then vacuum distillation
 Next, these distillation cuts are further processed through conversion units to transform
them into a more profitable mix of products. A typical refinery has 5-10 different
conversion units, such as an FCC or coker. These allow the refinery to produce a mix of
petroleum products that is more valuable than the mix that occurs naturally in crude oil.
Many of the outputs from one conversion unit are also then fed into another conversion
unit
 Next, refiners employ treating units such as hydrotreaters to improve stream qualities and
to remove contaminants
 Finally, refiners blend different streams to create batches of finished refined
products meeting the exact quality specifications that the market wants
 
 
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Furnace
structure in which useful heat is produced by combustion or other means. Historically,
the furnace grew out of the fireplace and stove, following the availability of coal for
heating.
Chemical energy is transformed into heat by burning fuels such as coal, wood, oil, and
hydrocarbon gases.
 
https://www.britannica.com/technology/furnace
 
 

Atmospheric distillation
Also known as: atmospheric tower, pipe still, crude unit, primary distillation, crude distillation
unit, CDU, fractional distillation
Atmospheric distillation is the first and most fundamental step in the
the refining process. The primary purpose of the atmospheric distillation tower is to
separate crude oil into its components (or distillation cuts, distillation fractions) for further
processing by other processing units.
 
How it works
Crude oil is first heated to about 700-750F (400C). The heated crude is injected into the
lower part of the distillation column, where much of it vaporizes. As the vapors rise
through the tower, they pass through a series of perforated trays or structured packing.
As the vapors cool, their components will condense back into liquid at different levels in
the tower based on their boiling point. A portion of the vapors reaches the top of the
column, where it is cooled through heat exchangers and air coolers and partly
converted back into liquid. A portion of this is fed back into the distillation column as a
reflux stream to contact with the rising vapors, helping to cool them. These are sent to
the vacuum distillation for further fractionation under a vacuum.
 
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distillation/
 

Desalter
In a refinery, crude oil containing high levels of salt will go through a desalter before
being fed to the atmospheric distillation tower.
Removal of salts is important for reducing corrosion in the distillation tower and
downstream processing units. If not removed, the salt will form acids when heated that
will result in corrosion. Also, the salt can form deposits on heat exchanger surfaces over
time, resulting in fouling.
Desalting also removes suspended solids such as sand, dirt, and rust particles picked
up in transport.
How it works
In the desalter, the crude oil is heated and then mixed with 5-15% volume of fresh water
so that the water can dilute the dissolved salts. The oil-water mix is put into a settling
tank to allow the salt-containing water to separate and be drawn off. Frequently, an
electric field is used to encourage water separation. Demulsifying chemicals are also
used. For high levels of salt and/or to achieve very low final concentrations, two- or
three-stage desalting may be used.
Typical desalted crude will have concentration of 1 pound/thousand barrels (PTB).
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Vacuum distillation
Also known as: vac tower, vacuum unit, vacuum flasher, VDU
The vacuum tower separates the atmospheric resid generated by the atmospheric
distillation tower into its components by distilling the resid under a vacuum.
The vacuum is critical for separating the VGO from vacuum resid to provide feed
separately for the cracking units (FCC and hydrocracking) and deep conversion units
(coker, visbreaker, asphalt). The heavier the crude processed, the larger the vacuum unit
that will be required to separate the bottom of the barrel.
How it works
Atmospheric tower bottoms are injected into the vacuum tower under a pressure at
about 1/20th of atmospheric pressure (typically 25 to 40 mmHg or lower). Under these
low pressures, the atmospheric resid will vaporize at temperatures below those where it
starts to crack. This allows separation of very heavy components without cracking.
 
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distillation/
 

VGO
Also known as: vacuum gasoil
VGO is one of the two outputs of the vacuum distillation tower (along with vacuum resid).
VGO is the lighter material of the two.
The primary use of VGO is as feed to cracking units such as the FCC or the hydrocracker.
These units upgrade VGO into more valuable products, namely gasoline and diesel.
If not upgraded, VGO is blended into residual fuel oil. However, this is fairly rare since
the value of VGO is much greater as a feed into upgrading. Often, if a refinery lacks
enough cracking to upgrade the VGO it generates, it will sell this as an intermediate to
another refinery, rather than downgrading it by blending into residual fuel oil.
VGO is often sub-divided into a lighter and heavier fraction called LVGO and HVGO,
respectively.
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Hydrocracker
Also known as: HCK, HCU, unicracker, VGO hydrocracker
In a refinery, the hydrocracker upgrades VGO through cracking while injecting hydrogen.
This yields a high volume of high-quality diesel and kerosene product. This is in contrast
to the FCC, which uses the same feed (VGO) but produces more and better-
quality gasoline.
The hydrocracker is particularly valuable in a refinery that is trying to maximize diesel
production and reduce residual fuel oil
The flexiblity in the design and operation of hydrocrackers allows a wide range of feeds
and of product yields. However this comes at very high capital and operating costs.
Inputs
Hydrocrackers can take a wide variety of feeds depending upon the desired products.
The most common are:

 VGO - This lighter fraction from the vacuum distillation unit is the most common feed for
most hydrocrackers. It is a desirable feed when the refiner is attempting to maximize
overall diesel production
 Coker gasoil - This VGO-range product from the coker is well suited to a hydrocracker,
which is better able to handle its unsaturated components than an FCC unit is
 Cycle oils and cracked distillates - These low-quality diesel-range streams can be
hydrocracked to make jet fuel and gasoline-range material
 Atmospheric gasoil - This straight run diesel-range material can be hydrocracked to
increase gasoline production by generating additional naphtha feed for the reformer
 
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desk/hydrocracker/

Gasoline
Also known as: petrol, motor gasoline, mogas, benzine
Gasoline is one of the major petroleum products produced from processing crude oil in a
petroleum refinery.
Gasoline is one of the higher-valued light products (along with jet fuel and diesel). It is
used almost exclusively in the transportation sector, mostly as a fuel in automobiles and
other light-duty vehicles. Demand for gasoline varies seasonally with the highest
demand during the Northern Hemisphere summer. Summer is also when gasoline
quality specifications (especially vapor pressure) tend to be tightest, resulting in generally
higher prices in these months.
Generally, refiners will try to maximize their yield of gasoline, along with diesel, to
maximize profit. Since the two products draw from different boiling range material, they
are largely complementary. However, there are a few conversion units that favor one over
the other, forcing refiners to make a call on which will be more value-creating. Most
notably, FCCs will tend to upgrade VGO more toward gasoline, and hydrocrackers will
upgrade VGO more toward diesel.
Gasoline product qualities

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