Crude Oil Refining & Upgrading

By: Kelvin Wong, Kaying Ng, Shaheen Zangooi

What is Crude Oil & Crude Oil Refining? Crude oil, also known as black gold, is a thick, dark brown or greenish

flammable liquid, which is found in the upper strata of some regions of the Earth's crust

It is a complex mixture of various hydrocarbons, (mainly, alkanes), along with trances of other chemicals and compounds (e.g. Sulphur)

When extracted from underground, it ranges in density from very light to very heavy and in color, from yellow to black

Crude oil can be categorized as either "sweet crude" (where the sulphur content less than 0.5%) or "sour crude," (where the sulphur content is at least 2.5%)

An Oil Refinery

Crude oil must undergo several separation processes so that its components can be obtained and used as fuels or converted to more valuable products

The process of transforming crude oil into finished petroleum products (that the market demands) is called crude oil refining

Distillation of Crude Oil We can separate the components of crude oil by taking advantage of the

differences in their boiling points. This is done by simply heating up crude oil, allowing it to vaporize, and then letting the vapor to condense at different levels of the distillation tower (depending on their boiling points). This process is called fractional distillation and the products of the fractional distillation of crude oil is called fractions

A fraction from crude oil can be categorized into two categories: Refined Product: A crude oil fraction which contains a lot of individual

hydrocarbons (e.g. gasoline, asphalt, waxes, and lubricants)

Petrochemical Product: A crude oil fraction which contain one or two specific hydrocarbons of high purity (e.g. benzene, toluene, and ethylene).

AT THE TOP OF THE

DISTILLATION COLUMN

AT THE BOTTOM OF THE

DISTILLATION COLUMN

Short carbon chains

Long carbon chains

Light molecules Heavy molecules

Low boiling points

High boiling points

Gases & very runny liquids

Thick, viscous liquids

Very volatile Low volatility

Light colour Dark colour

Highly flammable Not very flammable

Crude Oil Refining

Fractions of Crude Oil & Their PropertiesName

Number ofCarbon Atoms

Boiling Point(°C)

Uses

Refinery Gas 3 or 4 below 30Bottled Gas

(propane or butane).

Gasoline 7 to 9 100 to 150Fuel for car

engines.

Naphtha 6 to 11 70 to 200Solvents

and used in gasoline.

Kerosene (paraffin) 11 to 18 200 to 300Fuel for aircraft

and stoves.

Diesel Oil 11 to 18 200 to 300Fuel for road vehicles

and trains.

Lubricating Oil 18 to 25 300 to 400Lubricant for engines

and machines.

Fuel Oil 20 to 27 350 to 450Fuel for shipsand heating.

Greases and Wax 25 to 30 400 to 500Lubricants

and candles.

Bitumen above 35 above 500Road surfaceand roofing.

Chemical Processing The fractions from crude oil are liable to undergo chemical processing to

alter its structure and thus its properties The sort of chemical processing employed depends largely on the market

demand Examples of chemical processes are as the following:

Cracking: the process obtaining relatively simple and small hydrocarbon molecules from the breaking down of large, heavier and more complex hydrocarbon molecules.

Coking: the process of breaking down bitumen into its fractions (done by a Coker)

Alkylation: A process where the structure of a hydrocarbon molecule in one fraction is altered to produce another hydrocarbon molecule with another structure. In alkylation, compounds with a low molecular weight, such as propylene and butylene, are mixed in the presence of a catalyst such as hydrofluoric acid or sulfuric acid

Unification: a process where two or more hydrocarbons are combined to produce a larger one. The major unification process is called catalytic reforming and occurs in the presence of a catalyst (platinum, platinum-rhenium mix) to combine low weight naphtha into aromatics

Treatment Processes Chemical sweetening, acid treating, clay contacting, caustic

washing, hydro treating, drying, solvent extraction, and solvent dewaxing. Sweetening compounds and acids desulphurize crude oil before processing and treat products during and after processing.

Clay Treating Use clay to soak up and remove unwanted components in petroleum

Dilute the oil with solvent and freeze the oil During the freezing process, wax will be solidify leaving only the pure oil

in liquid phase Acid treating

Using concentrated sulphuric acid to convert sludge from the oil Expensive

SO2 Treating Using a very toxic recyclable solvent to remove the worst components in

oil

Treatment: The Finishing Touch Impurities such as organic compounds containing sulphur, nitrogen, oxygen,

water, dissolved metals and inorganic salts must be removed from the distillated and chemically processed fractions

Treating is typically done by passing the fractions through the following: a column of sulphuric acid - removes unsaturated hydrocarbons

(hydrocarbons with carbon-carbon double-bonds), nitrogen compounds, oxygen compounds and residual solids (tars, asphalt)

an absorption column filled with drying agents to dehydrate the fraction

sulphur treatment and hydrogen-sulphide scrubbers to remove sulphur and sulphur compounds

Today, a major portion of refining involves blending, purifying, fine-tuning and improving products to meet specific requirements

Example: Refinery workers carefully blend together a variety of hydrocarbons to make  petrol. Moreover to distinguish the various grades of fuel, technicians add performance additives and dyes. At the end of the production of petrol, the petrol contains more than 200 hydrocarbons and additives

Refining Capacities

Why Upgrade An Oil Refinery? Oil refining releases carbon dioxide into the atmosphere Response to changing market demands for certain products Government regulations Clean Air Act Amendments of 1990 (CAAA90) Changing consumer demand for better and different products Decrease the number of non-hydrocarbons, impurities, and other

constituents Potential physical, mechanical, chemical, and health hazards are

recognized in air

Accomplishment of Oil Refinery Upgrading

The emissions of pollutants from oil refining decreased significantly over the past decade due to the new technology implemented into the oil refining techniques

Solvent-Refining Process Uses chemicals (fairly safe recyclable solvent) to dissolve one part of the oil

from another Removes heavy materials and wax (undesirable component by extraction)

References

How Stuff Works. 1998. How Oil Refining Works?. [Online]. http://science.howstuffworks.com/oil-refining.htm

UTS Energy Corporation. 2005. Glossary. [Online] http://www.uts.ca/glossary/

www.gcsescience.com. 2005. Products of Oil. [Online] http://www.gcsescience.com/a/o5.htm

Alan G. Lucas. 2000. Modern Petroleum Technology Volume 2. New York: John Wiley & Sons Inc.

Douglas M. Ruthren. 1997. Encyclopaedia of Separation Technology Volume 2. New York: John Wiley & Sons Inc.