Encyclopedia of Renewable Energy. James G. Speight
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Название: Encyclopedia of Renewable Energy
Автор: James G. Speight
Издательство: John Wiley & Sons Limited
Жанр: Физика
isbn: 9781119364092
isbn:
Bottoming cycle plants produce high temperature heat for industrial processes, and then a waste heat recovery boiler feeds an electrical plant. These plants are only used when the industrial process requires high temperatures, such as furnaces for glass and metal manufacturing, so they are less common.
Bottom Sediment and Water
Bottom sediment and water (sometimes referred to as basic sediment and water, BS&W) is a both a technical specification of certain impurities in liquid feedstocks and fuels and the method for measuring these properties. In the crude state, many fuels contain water and suspended solids – the particulate matter is also referred to as sediment. The water and solids are measured as BS&W. Considerable importance is attached to the presence of water or sediment in fuels because the water and sediment lead to difficulties in use.
Water, with its dissolved salts, may occur as easily removable suspended droplets or as an emulsion. The sediment dispersed in crude oil may be comprised of inorganic minerals from the production of the fuel as well as scale and rust from pipelines and tanks used for oil transportation and storage. Usually, water is present in far greater amounts than sediment but, collectively, it is unusual for them to exceed 1% of the crude oil on a delivered basis. Water and sediment can foul heaters, stills, and exchangers and can contribute to corrosion and to deleterious product quality. Also, water and sediment are principal components of the sludge that accumulates in storage tanks and must be disposed of periodically in an environmentally acceptable manner. Knowledge of the water and sediment content is also important in accurately determining net volumes of crude oil in sales, taxation, exchanges, and custody transfers.
The sediment consists of finely divided solids that may be drilling mud or sand or scale picked up during the transport of the fuel. The solids may be dispersed in the fuel or carried in water droplets. In any form, water and sediment are highly undesirable in a fuel and the relevant tests involving distillation (ASTM D95, ASTM D4006), centrifuging (ASTM D4007), extraction (ASTM D473), and the Karl Fischer titration (ASTM D4377, ASTM D4928) are regarded as important in fuel quality examinations.
See also: Hot Filtration Test.
Boudouard Reaction
The Boudouard reaction is a gasification reaction in which the carbon dioxide formed reacts with carbon to form carbon monoxide:
The reaction is an endothermic reaction and is favored at high temperatures (680°C, 1255°F). Unlike the gasification reactions, combustion reactions are highly exothermic, so the heat generated in combustion is usually balanced by the steam gasification reaction to attain heat integration. An idealized char gasifier with all inlet and outlet streams is used at the same temperature (i.e., 370°C, 700°F).
Breeder Reactor
A breeder reactor is a type of nuclear reactor which produces more fissile materials than they consume. The reactor is designed to extend the nuclear fuel supply for the generation of electricity, and has even been mistakenly called a potential renewable energy source.
By irradiation of a fissile material such as uranium-238 (238U) or thorium-232 (232Th), the reactor creates more fissile material than is used. Breeder reactors were at first found viable because they made more complete use of uranium fuel than light water reactor. Typically, a breeder reactor creates 30% more fuel than it consumes. After an initial introduction of enriched uranium, the reactor only needs infrequent addition of stable uranium, which is then converted into the fuel.
See: Nuclear Reactor – Breeder Reactor.
BRI Process
The BRI process uses a two-stage gasifier that raises the syngas temperature as high as 1,370 °C (2,500 °F) in the second stage to enable cracking of any high-boiling hydrocarbon derivatives to carbon monoxide and hydrogen, maximizing the ethanol yield, thus using a thermal cracking.
The hot producer gases are cooled to 37°C (98°F), and introduced into the biocatalytic reactor where ethanol is produced. Here, the modified bacteria culture Clostridium ljungdahlii is introduced and nutrients are added to provide for cell growth and automatic regeneration of the biocatalyst.
With a hydrogen/carbon monoxide ratio of 2, the reactions indicate that water and ethanol are the only products.
As the ethanol is toxic to the bacteria, there is a need to hold the ethanol concentrations below 3% in the reactor. A dilute, aqueous stream of ethanol is continuously removed through a membrane that retains cells for recycle to maximize reaction rates. Anhydrous ethanol is produced by conventional distillation followed by a molecular sieve, using the waste heat from the process. Water, with nutrients, is recycled from the distillation bottoms back to the biocatalytic reactor. With ambient temperature and pressures, a fermentation time of a few minutes has been achieved.
Briquette
A briquette (or briquet) is a block of carbonaceous smokeless fuel (flammable matter) which is used as fuel to start and maintain a fire. Common types of briquettes are charcoal briquettes and biomass briquettes. Briquettes are used for both domestic and industrial use, prepared from bituminous coal using a binder. Briquette production is a mature technology, and the technology associated with coal briquetting has been developed for almost 100 years.
Historically, briquettes (especially coal and coke briquettes) have been used for fuel for approximately 100 years. Traditionally, briquetting technology was established for developing countries to produce briquettes of local residues, for use in household cooking stoves and restaurants. Later, as the capacities of the machines increased, briquettes were used in industrial boilers to create heat, steam, and power for industry and power plants. Within the past three decades, briquetting has also found its way to households in industrialized countries as consumer logs for wood-burning stoves and fireplaces. However, with the advent of modern fuel systems, the use of briquettes has declined and use for these products is found most often in the operation of barbecue units. While still a marketable product for such use, briquettes as fuel (such as smokeless fuel) are not used often for domestic and industrial heating. In more recent years, as the focus on renewable energy has grown, the applications for briquettes have grown concurrently, as have different technologies and new applications.
The briquette has to be ignited from the bottom by burning wood. During ignition, the upper part of briquette, upon heating, emits volatile matter which is a mixture of carbon and hydrogen compounds and is a strong pollutant. The newly developed briquettes can be ignited from the top just by striking a match, and the volatile matter will be burnt away when it has passed the upper flame. The briquette should be coated with a thin layer of combustibles and oxidizing agent and, therefore, should be kept in a dry place lest moisture retards ignition.
See also: Briquette Binder, Briquette Manufacture.
Briquette Binder
The binder used for coal briquetting has considerable influence СКАЧАТЬ