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Fossil fuels: Coal, Oil and natural Gas
25 Aralık, 2010  |  Yorum yok  |  Energy, Energy Technology

Fossil fuels provide the bulk of the energy that powers the industrialized and developing world. As demand for fossil fuels increases, the technical undertakings needed to satisfy it must be constantly adapted.

Oil is most important fuel, heat source, and raw material in the chemical industry, but before it can be efficiently utilized, it must be refined. Refineries first remove sulfur from the oil. The resulting oil is then separated through distillation into its lighter and heavier components: gasoline, diesel, heating oil, and tar. To improve engine performance and reduce wear, various substances are added to gasoline.

Coal, on the other hand, often needs only a mechanical cleaning before it can be used. With so-called ‘cracking techniques’, it is also possible to produce liquid fuel from coal, for instance, to power vehicles. However, this process is technically complex and not yet cost-effective.

Natural gas contains 85-98 percent methane, along with other hydrocarbons, carbon dioxide, and sometimes helium. For easier transport and for use as a fuel, it is compressed and party liquefied. The heat produced during this compression process can be used for many purposes, including to heat homes or swimming pools.

Energy Production

Chemical energy stored in gasoline and other fuel is released and used in a multitude of ways. Many power plants produce energy using combustion engines. The fuel’s energy is converted to heat, which turns water into steam, which then exerts pressure to turn a turbine. The turbine drives a generator to produce electricity through the principle of induction. Thus, the energy from coal, oil, or natural gas must undergo numerous transformations, before it can be used in the form of electricity. During electricity production, excess heat is also given off, which can be transferred to other locations, for example, to heat buildings. This process of power-heat coupling, or cogeneration, makes better use of the same amount of fuel. Increased efficiency is important as combustion releases large amounts of CO2 into the atmosphere, a major contributor to the greenhouse effect.

Nuclear power

Nuclear technology works by splitting atomic nuclei to release vast amounts of energy. To begin the process, neutrons bombard fissionable material such as uranium or plutonium. When a neutron hits an atom’s nucleus at just the perfect speed, the nucleus split apart.

This produces smaller atoms, more free neutrons, and energy. The free neutrons then split other nuclei, initializing a chain reaction. A nuclear reactor’s core contains fuel rods of fissionable material bundled together. During controlled fission, moderators such as water or graphite control the neutron’s speed and control rods slow or stop the chain reaction when necessary. The heat from fission is then collected by a coolant substance and used to drive turbines and generators.

Types of reactors

Reactors differ according to the fission process used and the materials used as rods, coolant, and moderators. Boiling water reactors have on cooling cycle, the water that cools the reactor also drives the turbines as steam. Pressurized water reactors have separate water circulation systems. ‘Fast breeder’’ reactors, with liquid sodium coolant, ‘breed’ new fissionable material, extracting more energy from a given amount of uranium. Pebble bed reactors, on the other hand, use helium coolant, and spheres of fissionable material instead of rods. There are various risks associated with nuclear technology and different hazards are produced by each type of reactor. In boiling water reactors, defective turbine housings can leak radioactive water into the environment from the primary circulation system. In pebble-bed reactors, helium at over 1832°F can contact water, abruptly vaporize, and subsequently explode. Even properly functioning reactors produce radioactive waste that remains dangerous to plant life, animals, and humans for thousand of years. Despite the multitude of risks, nuclear power will continue to be used and innovations in safety mechanisms and more efficient utilization of fissionable material will constantly be discovered.

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