Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 249

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.