What is crude oil?

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What is crude oil?

Crude oil is a naturally-occurring substance found trapped in certain rocks below the earth's crust. It is a dark, sticky liquid which, scientifically speaking, is classed as a hydrocarbon. This means, it is a compound containing only hydrogen and carbon. Crude oil is highly flammable and can be burned to create energy. Along with its sister hydrocarbon, natural gas, crude oil makes an excellent fuel.

Hydrocarbons

Hydrocarbons are organic molecules that contain only carbon (C) and hydrogen (H).

Examples of hydrocarbons:

* Methane

* Propane

* Benzene

* Etc......

Unsaturated & Saturated Hydrocarbons

. Saturated Hydrocarbons

Saturated hydrocarbons contain only single carbon-carbon bonds, and therefore contain the greatest possible number of hydrogen atoms for their number of carbon atoms.

E.g.

* Alkanes

* Branched Alkanes

2. Unsaturated Hydrocarbons

Unsaturated hydrocarbons contain double and triple carbon-carbon bonds, and therefore do not contain the greatest possible number of hydrogen atoms for their number of carbon atoms.

E.g.

* Benzene

* Alkenes

* Alkynes

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If there is not enough oxygen present to completely burn the fuel to carbon dioxide and water other products may form. The most common partially burned products are likely to be carbon C (soot) and deadly carbon monoxide CO. It would appear that the hydrogen in the fuel molecules is more easily burned and usually forms water.

eg CH4(g) + O2(g) => C(s) + 2H2O(l) or 2CH4(g) + 3O2(g) => 2CO(g) + 4H2O(l)

Therefore it is extremely important that any combustion system is as efficient as possible eg gas heaters, furnaces etc must all have excellent ventilation for complete combustion to harmless water and carbon dioxide. Carbon monoxide is colourless and odourless and even low concentrations in the air can be fatal. Carbon monoxide is unfortunately emitted by all car exhausts, though catalytic converters help reduce this by converting nitrogen monoxide (another pollutant) and carbon monoxide into harmless nitrogen and carbon dioxide.

2NO(g) + 2CO(g) => N2(s) + 2CO2(l)

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The Problem of Incomplete Combustion

Fossil fuels are a complex mixture of carbon and hydrogen-containing molecules referred to as hydrocarbons (HC). In addition to the pure hydrocarbon molecules, fuels also have a small fraction of molecules containing nitrogen, sulphur and other elements including many metals such as vanadium. Poor quality fuels, such as coals, are comprised of very large, mostly carbon containing molecules. The amount of hydrogen in the fuel increases as the size of the molecules decrease and the quality of the fuel increases. Higher quality fuels which have more hydrogen and smaller molecules burn faster and more completely. When fossil fuels burn, oxygen is reacting with the hydrocarbon molecules to produce carbon dioxide (CO2), water (H2O), oxides of the trace elements (Nox, Sox, Vox, etc. where x is 0 or a small number) and heat. How completely the hydrocarbons burn depends upon three basic factors:
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* The rate at which the molecules burn.

(This rate is a function of how large the molecules are.)

* How much oxygen is present around the fuel molecules

* The length of time that the fuel molecules spend in the fireball

Some of the harmful waste products and effects are:

* Black Smoke problems.

* Slagging, fouling, and corrosion of the car.

Carbon particles (soot), and condensed tar, result from the incomplete combustion of fuels. When present in sufficient particle size and quantity, soot in ...

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