In the coming decades, the shifting demand for fossil-based transportation fuels will be the defining factor that will transform existing oil refining capacity. Future refineries will be equipped with flexible technology solutions that can enable them to make a wide variety of chemicals and intermediates.
Currently, most refineries are focused on the production of
gasoline and distillate transportation fuels. However, energy analysts predict
that mandated fuel economy standards, as well as growth in alternative
drivetrains and shared mobility services will impact the overall global demand
for transportation fuels over the coming decades. As a result, more refineries are considering
diversifying their offerings to a variety of petrochemicals.
An oil refinery or petroleum refinery is
an industrial process plant where crude oil is
transformed and refined into useful products such as petroleum
naphtha, gasoline, diesel fuel, asphalt base, heating
oil, kerosene, liquefied petroleum gas, jet
fuel and fuel oils.
Petrochemicals feed stock like ethylene and
propylene can also be produced directly by cracking crude oil without the need
of using refined products of crude oil such as naphtha. The crude
oil feedstock has typically been processed by an oil production
plant. There is usually an oil depot at or near an oil refinery for
the storage of incoming crude oil feedstock as well as bulk liquid products.
Oil refineries are typically large, sprawling industrial
complexes with extensive piping running throughout, carrying streams
of fluids between large chemical processing units, such
as distillation columns. In many ways, oil refineries use much of the
technology and can be thought of, as types of chemical plants. The
Reliance Industries owned Jamnagar refinery is part of the world’s largest
oil refining complex, with a processing capacity of 1.2Mbpd. Some modern
petroleum refineries process as much as 0.9Mbpd.
Operation
Raw or unprocessed crude oil is not generally useful in
industrial applications, although "light, sweet" (low viscosity,
low sulphur) crude oil has been used directly as a burner fuel to produce
steam for the propulsion of seagoing vessels. The lighter elements, however,
form explosive vapours in the fuel tanks and are therefore hazardous. Instead,
the hundreds of different hydrocarbon molecules in crude oil are separated in a
refinery into components that can be used as fuels, lubricants, and feedstocks
in petrochemical processes that manufacture such products as
plastics, detergents, solvents, elastomers, and fibres such as
nylon and polyesters.
Different boiling points allow
the hydrocarbons to be separated by distillation. Since the
lighter liquid products are in great demand for use in internal combustion
engines, a modern refinery will convert heavy hydrocarbons and lighter gaseous
elements into these higher-value products.
Oil refineries operations will typically process about a hundred
thousand to several hundred thousand barrels of crude oil a day. Because
of the high capacity, many of the units operate continuously, as opposed
to processing in batches, at steady state or nearly steady state
for months to years. The high capacity also makes process
optimisation and advanced process control very desirable.
Products
The majority of the feed crude oil is converted to petroleum
products, which includes several classes of fuels. Oil refineries also produce
various intermediate products such as hydrogen, light hydrocarbons,
reformate and pyrolysis gasoline. These are not usually transported but
instead are blended or processed further on-site. Chemical plants are thus
often adjacent to oil refineries or a number of further chemical processes are
integrated into it. Technical reasons and environment protection demand a very
low sulphur content in all but the heaviest products, so it is transformed
to hydrogen sulphide via
catalytic hydrodesulphurisation and removed from the product stream
via amine gas treating. Using the Claus process, hydrogen sulphide is
afterward transformed to elementary sulphur to be sold to the chemical
industry.
According to the composition of the crude oil feed and depending
on the demands of the market, refineries can produce different shares of
petroleum products. The largest share of oil products is used as "energy
carriers", i.e. various grades of fuel oil and gasoline.
These fuels include or can be blended to give gasoline, jet fuel, diesel
fuel, heating oil, and heavier fuel oils. Heavier (less volatile)
fractions can also be used to produce asphalt, tar, paraffin
wax, lubricating and other heavy oils. Refineries also produce
other chemicals, some of which are used in chemical processes to
produce plastics and other useful materials.
First Stage Processing
The crude oil distillation unit (CDU) is the first processing
unit in virtually all petroleum refineries. The CDU distils the incoming crude
oil into various fractions of different boiling ranges, each of which is then
processed further in the other refinery processing units. The CDU is often referred
to as the atmospheric distillation unit because it operates at
slightly above atmospheric pressure.

In a typical crude oil distillation unit the incoming crude oil
is preheated by exchanging heat with some of the hot, distilled fractions and
other streams. It is then desalted to remove inorganic salts (primarily sodium
chloride).
Following the desalter, the crude oil is further heated by
exchanging heat with some of the hot, distilled fractions and other streams. It
is then heated in a fuel-fired furnace (fired heater) to a temperature of about
398 °C and routed into the bottom of the distillation unit.
The cooling and condensing of the distillation tower overhead is
provided partially by exchanging heat with the incoming crude oil and partially
by either an air-cooled or water-cooled condenser. Additional heat is removed
from the distillation column by a pump around system.
The overhead distillate fraction from the distillation column is
naphtha. The fractions removed from the side of the distillation column at
various points between the column top and bottom. Each of the side-cuts (i.e.,
the kerosene, light gas oil, and heavy gas oil) is cooled by exchanging heat
with the incoming crude oil.
All of the fractions (i.e., the overhead naphtha, the side-cuts,
and the bottom residue) are sent to intermediate storage tanks before being
processed further.
Shift Towards Integration
In the medium term AME
anticipate a shift towards integrated refinery models, where refining and
petrochemical units are interconnected, is an approach designed to make
refinery operations more sustainable.
The conventional model,
where refiners generate revenue primarily by processing crude oil to produce
transportation fuels, is increasingly under threat from falling fuels demand,
particularly in Europe.
Shell refineries for example have in recent years shifted
towards a crude-to-chemicals mode providing site flexibility in producing
fuels, lubricants, and chemical products as market demands shift.