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    Electric power plants commonly use a pulverized coal steam-generating system, in which metal spheres or cylinders crush pieces of coal into a fine powder. Hot air blows the... More »

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Delayed coking Last Updated on 2012-03-14 00:00:00 Delayed coking is one of the chemical engineering unit processes used in many petroleum refineries. The main objective of the delayed coking unit is to convert low value residual products to lighter products of higher value and to produce a coke product. In brief, the process heats the residual oil from the vacuum distillation unit in a petroleum refinery to its thermal cracking temperature in the heat transfer tubes of a furnace. This partially vaporizes the residual oil and initiates cracking of the long chain hydrocarbon molecules of the residual oil into hydrocarbon gases, coker naphtha, coker gas oil and petroleum coke. The heater effluent discharges into very large vertical vessels (called "coke drums") where the cracking reactions continue to completion, forming solid petroleum coke which deposits out and accumulates in the coke drums from which the product... More »
Fossil fuel combustion flue gases Last Updated on 2011-11-08 00:00:00 Fossil fuel combustion flue gases refer to the emissions of combustion product gases resulting from the burning of fossil fuels such as coal, oil, and natural gas.[1] Most fossil fuels are combusted with ambient air being the oxidant (as differentiated from combustion with pure oxygen) and this article is based on the use of ambient air as the combustion air. Discussion of flue gas components Since ambient air contains about 79 volume percent gaseous nitrogen (N2),[2] which is essentially non-combustible, the largest part of the flue gases from most fossil fuel combustion is uncombusted nitrogen. The next largest part of the flue gas is carbon dioxide (CO2) which can be as much as ten to fifteen volume percent or more of the flue gas. This is closely followed in volume by water vapor (H20) created by the combustion of the hydrogen in the fuel with atmospheric oxygen.... More »
Health impact of coal and electricity consumption Last Updated on 2011-06-20 00:00:00 Public Health Impact of Coal and Electricity Consumption: Risk–Benefit Balance Varies by Country This article, written by Tanya Tillett*, appeared first in Environmental Health Perspectives—the peer-reviewed, open access journal of the National Institute of Environmental Health Sciences The article is a verbatim version of the original and is not available for edits or additions by Encyclopedia of Earth editors or authors. Companion articles on the same topic that are editable may exist within the Encyclopedia of Earth. Access to electricity contributes to good health by powering infrastructure for clean drinking water and sanitation and by reducing the need for indoor burning of coal, wood, and other solid fuels. But these benefits can be offset by health threats posed by the emissions from... More »
Coal-Fired Power Plants Last Updated on 2010-11-09 00:00:00 Electric power plants commonly use a pulverized coal steam-generating system, in which metal spheres or cylinders crush pieces of coal into a fine powder. Hot air blows the coal powder into a furnace, where it combusts at high temperatures and converts water to steam. The steam passes through a series of high-, mid-, and low-pressure turbines connected to a common shaft that spins a generator. This type of power plant requires high-grade (low ash content) coal. Another type of coal-fueled power plant utilizes “fluidized bed combustion,” a method that involves burning coal in a layer (bed) of heated particles suspended in flowing air. [1] At sufficiently high air velocity, the bed acts as a fluid that thoroughly mixes coal particles with air, completely combusting the coal at relatively low temperatures. The advantage of fluidized bed combustion is that it can use... More »
History of the manufactured and natural gas industries in the USA Last Updated on 2009-01-27 00:00:00   The historical gas industry includes two chemically distinct flammable gases. These are natural gas and several variations of manufactured coal gas. Manufactured gas should not be confused with natural gas, the primary fuel gas of our day. Manufactured, or artificial gas, was produced from coal, petroleum oil or mixtures of coal and oil. The first attempts to manufacture gas on a commercial basis  were made in the late 1700s and early 1800s by Phillippe Lebon in France and by William Murdoch in England.  Natural gas is composed primarily of methane, a hydrocarbon composed of one carbon atom and four hydrogen atoms, or CH4. As a "fossil fuel", natural gas flowing from the earth is rarely pure. It is commonly associated with petroleum crude oil and may contain other hydrocarbons including ethane, propane and butane. In the United States,... More »