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Petroleum
Fuel is burned or otherwise consumed to produce heat. The common fuels used in
industry, transportation, and the home are burned in air. The carbon and
hydrogen in fuel rapidly combine with oxygen in the air in an exothermal
reaction—one that liberates heat. Most of the fuels used by industrialized
nations are in the form of incompletely oxidized and decayed animal and
vegetable materials, or fossil fuels, specifically coal, peat, lignite,
petroleum, and natural gas. From these natural fuels other artificial ones can
be derived. Coal gas, coke, water gas, and producer gas can be made using coal
as the principal ingredient. Gasoline, kerosene, and fuel oil are made from
petroleum. For most transportation, fuel must be in a liquid form.
Petroleum, is a flammable liquid that occurs naturally in deposits, usually
beneath the surface of the earth; it is also called crude oil. It consists
principally of a mixture of hydrocarbons, with traces of various nitrogenous
and sulfurous compounds.
During the past 600 million years incompletely decayed plant and animal remains
have become buried under thick layers of rock. It is believed that petroleum
consists of the remains of these organisms but it is the small microscopic
plankton organism remains that are largely responsible for the relatively high
organic carbon content of fine-grained sediments like the Chattanooga shale
which are the principle source rocks for petroleum. Among the leading producers
of petroleum are Saudi Arabia, Russia, the United States (chiefly Texas,
California, Louisiana, Alaska, Oklahoma, and Kansas), Iran, China, Norway,
Mexico, Venezuela, Iraq, Great Britain, the United Arab Emirates, Nigeria, and
Kuwait. The largest known reserves are in the Middle East.
Because of the subterranean origin of petroleum it must be extracted by means
of wells. Until an exploratory well, or wildcat, has been dug, there is no sure
way of knowing whether or not petroleum lies under a particular site. In order
to reduce the number of exploratory wells drilled, scientific methods are used
to pick the most promising sites. Sensitive instruments, such as the
gravimeter, the magnetometer, and the seismograph, may be used to find
subsurface rock formations that can hold crude oil. Drilling is a fairly
complex and often risky process. Some wells must be dug several miles deep
before petroleum deposits are reached. Many are now drilled offshore from
platforms standing in the ocean bed. Usually the petroleum from a new well will
come to the surface under its own pressure. Later the crude oil must be pumped
out or forced to the surface by injecting water, gas, or air into the
deposits.The crude oil is usually sent from a well to a refinery in pipelines
or tanker ships.
The hydrocarbon components are separated from each other by various refining
processes. In a process called fractional distillation petroleum is heated and
sent into a tower. The vapors of the different components condense on
collectors at different heights in the tower. The separated fractions are then
drawn from the collectors and further processed into various petroleum
products. One of the many products of crude oil is a light substance with
little color that is rich in gasoline. Another is a black tarry substance that
is rich in asphalt.
The amount of fossil fuel and natural resources available are limited and
effort must be made to explore the other alternative energy resources.
Energy Resources
In the current free market environment, energy has become a global matter which
concerns with the health of the international economy and financial systems.
The issue becomes one of the extent to which the international economy as well
as individual countries are economically vulnerable to oil price shocks.
One proposed alternative fuel is hydrogen, which is now employed as a fuel only
for a few special purposes because of its high cost. Hydrogen can be produced
by electrolysis of water for which nonfossil fuels would supply the energy.
Solar energy could be utilized either by direct conversion to electricity using
photovoltaic cells or by trapping solar heat. Fuels are rated according to the
amount of heat (in calories or Btu) they can produce. Nuclear fuels are also
possible substitutes for fossil fuels. Nuclear fuels are not burned; they
undergo reactions in which the nuclei of their atoms either split apart, i.e.,
undergo fission, or combine with other nuclei, i.e., undergo fusion. In either
case, a small part of the nuclear mass is converted to heat energy. All nuclear
fuels currently employed in practical, nonweapons applications react by
fission.
High-energy fuels for jet engines and rockets are rated by their specific
impulse in thrust per pound of propellant per second. Hydrogen, which is the
lightest element, is usually used in the form of compounds, because the density
of liquid hydrogen is low and therefore a large volume is required. Addition of
aluminum powder or lithium increases the efficiency. Rockets usually have a
self-contained supply of oxygen or some other oxidizer, such as ammonium,
lithium, or potassium perchlorate. Fuels such as turpentine, alcohol, aniline,
and ammonia use nitric acid, hydrogen peroxide, and liquid oxygen as oxidizers.
More power can be obtained by oxidizing hydrazine, diborane, or hydrogen with
oxygen, ozone, or fluorine.
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