Crude Oil 101
Crude oil is a complex mixture of many different components. The separation of
these components into useable products is known as refining. Refineries must be designed
to handle the type of crude oil they are going to process. Crude oil from the Appalachian
Basin (Pennsylvania Grade Crude Oil) contains a lot of wax and paraffin. The amounts of
gasoline and fuels that are produced or distilled are relatively small, and in some
conditions are by-products of the refining process. The lubricating stocks and waxes that
are obtained from Pennsylvania Grade Crude oil are the most desired portions. Other crude
oil, such as that from Prudhoe Bay in Alaska, contain much less wax and far more fuel. The
bottoms or residue left after the distillation are very asphaltic and very good for making
road tar and heavy burner fuel.
From the analysis of the crude oil, it can be determined what the basic
composition of the crude is and what applications it is best suited for.
As as example
as crude oil comes out of the ground, it can be
The American Petroleum Institute (API) gravity methodology determines these
The Pennsylvania Grade Crude oil can be broken down into the following basic
fractions, or components: Gasoline, Kerosene and Fuel Oil, Gas Oil, Wax Distillate, and
Cylinder Stock or Bottoms.
The gasoline fraction is further refined and through a variety of processes is
converted into the fuel we power our cars with. Certain portions of the gasoline fraction
are removed (depentanized) and others have their chemical structure changed (isomerized).
Some impurities are removed (desulfurized), and others have components added to produce
the final product (reformulated gasoline).
The kerosene and fuel oil fraction is basically unchanged and used as fuel for
the trucking and construction industry. This fraction can also be processed into some of
the specialty solvents used in manufacturing.
The gas oil fraction is a heavy, relatively slow burning, non-volatile fuel, or
it is frequently used as a light lubricating oil. This fraction can be used either as a
fuel or as an oil. If the gas oil fraction is hydroprocesssed, it can be made into white
oil (sewing machine oil) or high quality oils for use in cosmetics and pharmaceuticals.
The wax distillate is a valuable source of lubricating stock and paraffin. By
removing the wax or paraffin one of the basic components of lubricant is produced
(neutral). Neutrals can be further refined through distillation (fractionation) and
hydroprocessing (catalyzation) to produce a series of specialized components used in the
manufacture of engine oils, gear lubricants, and greases. The addition of additives to
control oxidation, thermal degradation, and viscosity produce the high quality lubricants
used today. Paraffins are used in many different aspects of our daily life. They are used
not only in candles, but in cosmetics, paper coating, inks, fabrics, and even on our
The Cylinder Stock or Bottoms fraction is what is left over after the crude oil
has been put through the distillation tower. The wax portion is removed to create a
product called Micro Wax. Micro has a much higher melting point than paraffins and is
therefore suitable for a variety of products we use daily, such as a component of many
plastics, candy, and in building materials. Many types of candy that would be too soft
otherwise, have their form because of the inclusion of micro wax. A Canadian company has
even developed a process to form micro wax and polymers into a structural material that
does not require maintenance, in essence it is a wax brick. The oil portion of the
cylinder stock is further processed to remove the resins. These resins are used to create
many different products ranging from high temperature insulations to undercoatings or
fuels for ocean going barges. The oil portion of cylinder stock is then a heavy lubricant
base stock used in heavy duty gear oil applications and many industrial lubricants.
The refining of crude oil is a complex and involved operation that generate
many different components that are the building blocks for virtually every product we use
in our daily lives. As you can now see, the products of the refining process are not just
limited to the automotive industry, as many people would think, but are important
components in almost every modern convenience manufactured today.
of Crude Oil accoridng to the U. S. Environmental Protection Agency
The petroleum industry often characterizes crude oils according to their
geographical source, e.g.,
Crude. Oils from different geographical areas have unique properties; they can
vary in consistency from a light volatile fluid to a semi-solid.
Classification of crude oil types by geographical source is generally not a
useful classification scheme for response personnel because they offer little
information about general toxicity, physical state, and changes that occur
with time and weathering. These characteristics are primary considerations in
oil spill response. The classification scheme provided below is more useful in
a response scenario.
Light, Volatile Oils. These oils are highly fluid, often clear, spread rapidly
on solid or water surfaces, have a strong odor, a high evaporation rate, and
are usually flammable. They penetrate porous surfaces such as dirt and sand,
and may be persistent in such a matrix. They do not tend to adhere to
surfaces; flushing with water generally removes them. Class A oils may be
highly toxic to humans, fish, and other biota. Most refined products and many
of the highest quality light crudes can be included in this class.
Non-Sticky Oils. These oils have a waxy or oily feel. Class B oils are less
toxic and adhere more firmly to surfaces than Class A oils, although they can
be removed from surfaces by vigorous flushing. As temperatures rise, their
tendency to penetrate porous substrates increases and they can be persistent.
Evaporation of volatiles may lead to a Class C or D residue. Medium to heavy
paraffin-based oils fall into this class.
Heavy, Sticky Oils. Class C oils are characteristically viscous, sticky or
tarry, and brown or black. Flushing with water will not readily remove this
material from surfaces, but the oil does not readily penetrate porous
surfaces. The density of Class C oils may be near that of water and they often
sink. Weathering or evaporation of volatiles may produce solid or tarry Class
D oil. Toxicity is low, but wildlife can be smothered or drowned when
contaminated. This class includes residual fuel oils and medium to heavy
Nonfluid Oils. Class D oils are relatively non-toxic, do not penetrate porous
substrates, and are usually black or dark brown in color. When heated, Class D
oils may melt and coat surfaces making cleanup very difficult. Residual oils,
heavy crude oils, some high paraffin oils, and some weathered oils fall into
classifications are dynamic for spilled oils; weather conditions and water
temperature greatly influence the behavior of oil and refined petroleum
products in the environment. For example, as volatiles evaporate from a Class
B oil, it may become a Class C oil. If a significant temperature drop occurs
(e.g., at night), a Class C oil may solidify and resemble a Class D oil. Upon
warming, the Class D oil may revert back to a Class C oil.
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laboratory uses the methods and standards of these organizations
ASTM [ American Standard and Testing Material ] methods.
For detailed information see the ASTM website at: http://www.ASTM.ORG
And The SAE [Society of Automotive Engineers]
For detailed information see the SAE website at:
established industry standards.
Petroleum Institute [API].
the EPA [
Environmental Protection Agency ]
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