water reactor is produced directly in the reactor core, while, in contact, the steam in a pressurized water reactor (PWR) is produced in a secondary system. The pressure of a pressurized boiling reactor varies from the primary system to the output steam, while the pressure of a boiling water reactor remains constant.
An advantage of the pressurized water reactor is that the pressurized water reactor can operate at higher temperature and pressure on the order of approximately 315°C (600°F) and 2,400 psi. This provides a higher efficiency than the boiling water reactor.
See: Nuclear Reactor – Boiling Water Reactor.
Bone Dry
The term bone dry when applied to biomass or a biomass product refers to 0% moisture content and refers to (in this context) the biomass being extremely or completely dry. For example, wood heated in an oven at a constant temperature of 100°C (212°F) or above until its weight stabilizes is considered bone dry or oven dry.
Boson
A boson is a particle which carries a force and has a whole number spin (spin is a property of subatomic particles). Bosons carry energy. A photon is an example of a boson as it has a spin of 1 and carries electromagnetism. Mesons are also bosons as they carry nuclear force.
See also: Electron, Nuclear Energy, Photon, Positron.
Bottom Ash
The most common type of furnace in the electric utility industry is the dry, bottom- pulverized feedstock boiler. When pulverized feedstock is burned in a dry, bottom boiler, approximately 80% w/w of the unburned material or ash is entrained in the flue gas and is captured and recovered as fly ash. The remaining 20% w/w of the ash is dry bottom ash, a dark gray, granular, porous solid that is collected in a water-filled hopper at the bottom of the furnace. When a sufficient amount of bottom ash drops into the hopper, it is removed by means of high-pressure water jets and conveyed by sluiceways, either to a disposal pond or to a decant basin for dewatering, crushing, and stockpiling for disposal or use.
Bottom ash is the coarser component of the ash and may comprise a substantial portion of the waste. Rather than floating into the exhaust stacks, it settles to the bottom of the power plant boiler. Bottom ash is not quite as useful as fly ash, although power plant owners have tried to develop options for beneficial use options, such as structural fill and road-base material. However, the bottom ash remains toxic when recycled and can leak heavy metals into the groundwater.
See also: Ash, Biomass Ash, Boiler Slag, Fly Ash.
Bottoming Cycle
The bottoming cycle is a cogeneration system in which steam is used first for process heat and then for electric power production. In the plant, a waste-heat recovery boiler recaptures the unused energy and uses it to produce steam to drive a steam turbine generator to produce electricity.
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