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:
The bulk density differs widely between different types of biomass. Together with the heating value, it determines the energy density of the gasifier feedstock, i.e., the potential energy available per unit volume of the feedstock. Biomass of low bulk density is expensive to handle, transport, and store. Apart from handling and storing behavior, the bulk density is important for the performance of the biomass as a fuel inside the reactor: a high void space tends to result in channeling, bridging, incomplete conversion and a decrease in the capacity of the gasifier. The bulk density varies widely (100 to 1,000 kg/m3) between different biomass feedstocks not only because of the character of the biomass but also as a result of the way the biomass comes available (chips, loose, baled).
Bunker
A bunker is a storage tank used for gaseous fuels, liquid fuels, and biomass fuel products.
Fuel bunkers, commonly known as bunkers, are containers for the storage of fuel on steam-powered boats or steam tank engines or rooms for the storage of fuel in furnaces. The term bunker or fuel bunker is typically only used for storage areas for solid fuels (such as coal or, in the current context, solid biofuel). The term fuel tank is typically used for liquid fuels) or gaseous fuels.
Bunker Fuel Oil
Bunker fuel is technically any type of fuel oil used aboard ships. It gets its name from the containers on ships and in ports that it is stored in; in the days of steam, they were coal bunkers, but now, they are bunker-fuel tanks.
Bunker fuel is the colloquial term for fuel oil used by marine vessels. Bunker fuels A, B, and C are respectively downgrading quality-classifications of fuel oil, characterized by their boiling points, carbon-chain lengths, and viscosities, all of which contribute to their value (in other words, Bunker A is more valuable than Bunker C). Currently, most of the global shipping fleet relies on diesel Bunker C fuel oil which contributes significant amounts of greenhouse gas emissions, sulfur, and other emissions that contribute negatively to climate change and negative environmental and human health impacts.
More specifically, bunker A is No. 2 fuel oil, bunker B is No. 4 or No. 5, and bunker C is No. 6. Since No. 6 is the most common, bunker fuel is often used as a synonym for No. 6. No. 5 fuel oil is also called navy special fuel oil or just navy special, No. 6 or 5 are also called furnace fuel oil (FFO); the high viscosity requires heating, usually by a recirculated low pressure steam system, before the oil can be pumped from a bunker tank. In the context of shipping, the labeling of bunkers as previously described is rarely used in modern practice.
Butane
Butane is a gaseous component of natural gas. Butane can also be produced from crude oil. Butane gas (n-butane) is the four-carbon unbranched alkane (CH3CH2CH2CH3). Butane is also used as a collective term for n-butane together with its only other isomer, iso-butane [methylpropane, CH(CH3)3]. Butanes are highly flammable, colorless, odorless, easily liquefied gases.
Butane is sold bottled as a fuel for cooking and camping. When blended with propane and limited amounts of other hydrocarbon derivatives (subject to the specifications), it is referred to commercially as liquefied petroleum gas. It is also used as a gasoline component and as a feedstock for the production of base petrochemicals in steam cracking, as well as a propellant in aerosol sprays.
Very pure forms of butane, especially iso-butane, can be used as refrigerants and have largely replaced the ozone layer-depleting halomethanes in household refrigerators and freezers. The flammability of butane is not usually an issue because the amount of butane in an appliance is not enough to cause a combustible mix given the amount of air in a room.
Butane Dehydrogenation
The butane dehydrogenation process is a process for removing hydrogen from butane to produce butenes and, on occasion, butadiene.
This process is achieved in several ways – the most common method is to heat hydrocarbon derivatives to high temperature, as in thermal cracking, that causes some dehydrogenation. In the chemical process industries, nickel, cobalt, platinum, palladium, and mixtures containing potassium, chromium, copper, aluminum, and other metals are used in very large-scale dehydrogenation processes.
n-Butane, iso-butane, and t-butane, while naturally occurring, have few commercial applications beyond fuels. Butanes can be isomerized and then reacted with iso-butene or other light olefins in alkylation processes to yield high-octane motor gasoline blending stock. Butenes, 1-butene, cis-2-butene, trans-2-butene, and iso-butene, also known as butylenes, by comparison have a variety of commercial uses. Iso-butene is a primary reactant in the production of methyl tertiary butyl ether (MTBE), a major additive in reformulated gasoline and used to reduce emissions from automobile exhaust. Butenes are oligomerized and hydrogenated to produce higher alkanes for gasoline blend stock uses and can be reacted further to produce other commercially important products. It is estimated that 90% of butene consumption is in motor fuel applications such as alkylate, polymer gasoline, and oligomerized gasoline blend stocks. Butenes are also blended directly into gasoline and mixed with propane and butanes in liquefied petroleum gas. Approximately 10% of the available butenes are used in chemical production where the most important products are butadiene, sec-butyl alcohol, butyl rubber, and polybutylene elastomer.
Butenes are produced as by-products of many refinery processes. Due to the huge volumes of crude oil subjected to catalytic cracking, catalytic crackers are the single largest source of mixed butenes that are typically used for MTBE production. Cracking catalysts and conditions are sometimes formulated and selected to especially maximize the production of iso-butene. Steam cracking of olefins is another major source of by-product butenes.
Butenes are dehydrogenated further to produce butadiene. Butadiene is one of three copolymers in abs, acrylonitrile-butadiene-styrene plastic and styrene-butadiene rubber. Dehydrogenation reactions are endothermic, and those of butane and butene are no exception.
One goal of the various processes for producing either butenes or butadiene is to maximize feedstock conversion and simultaneously selectivity to the desired product isomer. For example, while mixed butenes are typically used for MTBE and polygas synthesis, polybutylene production requires higher purity 1-butene. The yield of each isomer is controlled by the reaction conditions employed. The recovered yield is controlled by the downstream separation steps applied to the mixture of product and un-reacted starting materials. The practical result of these sometimes conflicting demands is a wide range of conversion technologies and separation approaches, each more or less optimized for a specific end use application.
Maximization of the conversion of feed to product can be accomplished by reducing the vapor pressure of the products in the reactor. A common practice is to add steam to the reactor. This not only reduces the partial pressure of the products driving the conversion higher; it is typically also utilized to import the needed heat of reaction into the reaction vessel. Steam is used because it can be easily separated from the reactor effluent through condensation. Another approach is to selectively remove one of the products of the reaction from the reactor, in this case the hydrogen.
Hydrogen is removed СКАЧАТЬ