Fossil Fuels Combustion

Chemical reactions are the heart of chemistry. People have always known that they exist. The Ancient Greeks were the firsts to speculate on the composition of matter. They thought that it was possible that individual particles made up matter. Later, in the Seventeenth Century, a German chemist named George Ernst Stahl was the first to postulate on chemical reaction, specifically, combustion. He said that a substance called phlogiston escaped into the air from all substances during combustion. He explained that a burning candle would go out if a candle snuffer was put over it because the air inside the snuffer became saturated with phlogiston. According to his ideas, wood is made up of phlogiston and ash, because only ash is left after combustion. His ideas soon came upon some contradiction. When metal is burned, its ash has a greater mass than the original substance. Stahl tried to cover himself by saying that phlogiston will take away from a substances mass or that it had a negative mass, which contradicted his original theories.

In the Eighteenth Century Antoine-Laurent Lavoisier, in France, discovered an important detail in the understanding of the chemical reaction combustion, oxigine (oxygen). He said that combustion was a chemical reaction involving oxygen and another combustible substance, such as wood.

The large diversity of chemical reactions and approaches to their study results in the existence of several concurring, often overlapping, ways of classifying them. Below are examples of widely used terms for describing common kinds of reactions. When a chemical reaction occurs, the reactants and the product must get an equal amount of energy. The term combustion is usually used for only large-scale oxidation of whole molecules, i.e. a controlled oxidation of a single functional group is not combustion. The general application of combustion reactio is fossil fuels.

Mankind has used fossil fuels for a very long time. The Chinese used coal for heating and metal smelting around 500 BC. Roman historians describe coal being used for heating residences in Britannia during the roman occupation. During the industrial revolution in the 18th century more large-scale mining operations of coal started and oil was later introduced as a replacement for coal. Coal fueled Great Britain’s almost exponential growth of industry and combustion provided energy for the first true worldwide empire. In the end of 18th century was discovered that kerosene could be extracted from crude oil and by using refining even more usable fuels could be obtained. The demand for oil was greatly increased and after the First World War it became the primary fuel for the industrialized world.

The combustion of all fossil fuels follows a very similar reaction: Fuel (any hydrocarbon source) plus oxygen yields carbon dioxide and water and energy. A simple combustion reaction is given for methane. The combustion of methane means that it is possible to burn it. The world and modern society are driven by the need to produce energy to make products (manufacturing), to move around (transportation), to heat homes and buildings, and to create light (electricity). At least 75% of these needs are met by the combustion of fossil fuels. Energy is stored in chemical compounds in the bonds that bind atoms to each other.

Fossil fuels are of great importance because they can be burned (oxidized to carbon dioxide and water), producing significant amounts of energy. The use of coal as a fuel predates recorded history. Coal was used to run furnaces for the melting of metal ore. Semi-solid hydrocarbons from seeps were also burned in ancient times, but these materials were mostly used for waterproofing and embalming.

Commercial exploitation of petroleum, largely as a replacement for oils from animal sources (notably whale oil) for use in oil lamps began in the nineteenth century.

Natural gas, once flared-off as an un-needed byproduct of petroleum production, is now considered a very valuable resource.

Heavy crude oil, which is much more viscous than conventional crude oil, and tar sands, where bitumen is found mixed with sand and clay, are becoming more important as sources of fossil fuel. Oil shale and similar materials are sedimentary rocks containing kerosene, a complex mixture of high-molecular weight organic compounds, which yield synthetic crude oil when heated. These materials have yet to be exploited commercially. These fuels are employed in internal combustion engines, fossil fuel power stations and other uses.

Prior to the latter half of the eighteenth century, windmills or watermills provided the energy needed for industry such as milling flour, sawing wood or pumping water, and burning wood or peat provided domestic heat. The wide-scale use of fossil fuels, coal at first and petroleum later, to fire steam engines, enabled the Industrial Revolution. At the same time, gas lights using natural gas or coal gas were coming into wide use. The invention of the internal combustion engine and its use in automobiles and trucks greatly increased the demand for gasoline and diesel oil, both made from fossil fuels. Other forms of transportation, railways and aircraft also required fossil fuels. The other major use for fossil fuels is in generating electricity and the petrochemical industry. Tar, a leftover of petroleum extraction, is used in construction of roads.

Early combustion techniques: The first, coal ovens were very similar to ordinary wood ovens and were used for heat generation. The typical design was a bed of stone, on which coal was placed and ignited. More coal was added to the fire when the original coal was combusted. Ash and soot remained in a pile together with unburned coal and had to be removed from time to time. The second, critical and supercritical steam boilers: with the invention of electricity generators combustion was quickly adapted to drive steam boilers for power generation. The supercritical systems will result in slightly less fuel consumption due to the higher efficiency. The term boiler is a bit misleading as no actual boiling takes place in a supercritical system. The third, fixed-bed or stoker combustion: the primitive ovens were soon improved and refined once more large scale-coal combustion became important for heat and electricity production. This resulted in the so-called fixed-bed systems or Stoker systems. The fourth, pulverized coal combustion: if  coal particles are made fine enough, they will burn almost as easily and efficiently as a gas. This idea has resulted in the concept of pulverized coal combustion, which is the most wide just principle of combustion world wide today.

The fifth, cyclone furnace combustion: cyclone furnaces are an improved version of cyclone furnace combustion systems that requires less processing of the fuel and can use a wider array of different coal types. With a cyclone furnace it is possible to burn low-grade coal with high water and ash content. The coal is first crushed, into smaller pieces, and can be stored in containers or transported directly into the combustion area. The pieces do not have to be as small as in cyclone furnace combustion. The furnace itself is basically a large cylinder jacketed with water pipes that absorb some of the heat to make steam and protect the burner from melting. The sixth, cogeneration and polygeneration plants: fossil-fired power plants can also operate in cogeneration mode. This means that both useful electricity and heat is produced instead of only electricity. However this is only feasible if the power plant is located close to the consumers to the heat can be transported without being lost. Usually the heat is used for industrial processes, hot water generation or residential heating. By capturing the heat instead of cooling it away more useful energy can be produced from the same amount of fuel. The seventh, fluidized-bed combustion: by suspending a solid fuel on an upward-blowing jet of air a so-called fluidized bed can be obtained. The result is a turbulent mixing of gas and solids, which provide more effective chemical reactions and heat transfer. The behavior resembles to a bubbling fluid and gives a rapid mixing of particles. Compared to cyclone combustion the temperature is lower. Fluidized-bed combustion is of particular value for low-grade, high ash coals that are difficult to pulverize and might have varying combustion properties. The eighth, integrated gasification combined cycle: the integrated gasification combined cycle design creates a synthesis gas from coal or any other carbon source and burns the gas in a high efficiency gas turbine. It is also easier to clean out impurities and noxious materials from the syngas compared to cleaning the exhaust vapor from ordinary combustion of coal. The ninth, combustion of oil: Today only a very small percentage of the worlds electricity comes from combustion of oil. After the oil crisis in the 1980-ies most oil-fired power plants have shut down due to high oil prices. The tenth, combustion of gas: natural gas is burned in gas turbines.

 Finally, emissions from fossil combustion Coal combustion is by far the dominating source of carbon dioxide emissions from power generation. Almost 60% of the world total CO2 emissions from power generation come from coal-fired power plants. However there are also more problems with combustion of fossil fuels than just the released carbon dioxide. Coal is mostly composed of organic matter, but inorganic compounds are also present. It is primary the inorganic material that is deemed responsible for health, environmental and technological problems related to coal combustion. Some of these inorganic trace elements are even naturally radioactive. Sulphur constitutes of a major part of the unhealthy elements in coal. During combustion if can react with oxygen and form sulphur dioxide, which is toxic and leads to acid rain. Nowadays desulphurization is standard procedure for most coal-fired power plants and the emissions have been drastically reduced. Nitrogen can form NOx during combustion. Nitrous oxides are toxic and believed to aggregate asthmatic conditions. Eventually it can produce ground-level ozone, which in unhealthy and irritating. It can also react with water and form nitric acid, which leads to acid rain. NOx formation is generally prevented in modern combustion power plants by various methods such as scrubbing. Smog can be formed from Sox, NOx, volatile organic compounds, peroxyacyl nitrates and aldehydes resulting from incomplete combustion. It is an unhealthy mixture of fog and smoke, which cause problems in urban areas with much combustion. With proper flue gas treatment the possibility for smog creation is reduced to very small numbers.

Will the supplies of fuels we use today come to an end? Fossil energy sources by their very nature are a limited resource, though some are far more abundant than others. We are currently in an energy crisis. Fossil fuels are the lifeblood of our society and for many others around the world. Our supply has a finite end, which is why we are willing to go to war for it and make friends with those we really hate. The former Soviet Union and many of the countries in the Middle East are in our good favor strictly because of their oil reserves. Our foreign aid has a legitimate purpose. Even with our newfound friends, fossil fuels will run out and the use of them will soon take the lives of many people. These are important reasons to find other means of getting the energy we need to continue our society as we know it.

So what are our options? Alternative forms of energy are currently under development even though most of them are only in their inital stages. With increased government and public support, we may be able to speed up the development of these technologies and help free ourselves from the usage of fossil fuels. Oil companies will have to be dealt with because with the future shortages of fossil fuels, they would stand to reap enormous profits. To prevent this, oil and other energy resource providing companies should be encouraged to develop these technologies for the sake of ethics if not for long-term profit gains when all fossil fuel resources are exhausted.

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House, James E. Inorganic Chemistry. 2008. Canada: Elsevier

Huheey, James. Inorganic Chemistry. 1993. USA: Harper Collins College Piblishers

Sugiyarto, KH. Kimia Anorganik 1. 2004. Yogyakarta: FMIPA UNY

Bartok, William; Sarofim, Adel F. 1991.  Fossil Fuel Combustion: A Source Book. New York: John Wiley & Sons, Inc.,

Seidel, Stephen. Can We Delay a Greenhouse Warming?. 1983. Washington, D.C.: Strategic Studies Staff, Office of Policy Analysis

http://www.hubbertpeak.com/campbell/index.html

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http://library.advanced.org/10867/gathered/effected_resources.shtml

http://www.visionlearning.com/library/module_viewer.php?mid=54

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http://www.green-planet-solar-energy.com/fossil-fuels.html

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                Annisa Budhiarti                             08303241010

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