Coal slurry is a mixture of solids (mined

coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

coal waste Coal refuse (also described as coal waste, rock, slag, coal tailings, waste material, rock bank, culm, boney, or gob) is the material left over from coal mining, usually as tailings piles or spoil tips. For every tonne of hard coal generated by mi ...

) and liquids (water or organic) produced by a

coal preparation plant file:Coal Washer.JPG, 300px, A coal "washer" in Eastern Kentucky file:FAB's BlaschakCoalCompany IMG 4442 BLASCHAK 'Modern Breaker Coal Processing Plant'.JPG, A modern coal breaker in Mahanoy City, Pennsylvania combines washing, crushing, grading, s ...

Preparation

To transform the coal ash into a

slurry A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal p ...

, coal is separated from non-combustible components and can be fractionated by particle size as well. Coal slurry can be transferred by pipeline or with specialized pumps such as a progressive cavity pump to pump the highly abrasive, corrosive and viscous coal slurry. More than 7 billion tons of coal are mined per year (2010), using approximately 200 litres of water per ton. However, the amount of water required hinges on the surface characteristics of the coal being used. Most coal slurries require the addition of a

surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, fo ...

to reduce the viscosity, ergo reduce the stress on pipelines and pumps. Recent studies have employed new methods of slurry preparation, like using ultrasonic irradiation and a mixture of natural and synthetic surfactants to improve the stability and rheological properties of coal slurry.

Environmental concerns

Ideally, coal slurry consists only of crushed

and water, which can be efficiently separated. In practice, the separation is significantly costly due to the large amounts of water needed and wastewater generated by the process. Furthermore, the slurry consists also of very fine coal dust that results in a waste called

blackwater Blackwater or Black Water may refer to: Health and ecology * Blackwater (coal), liquid waste from coal preparation * Blackwater (waste), wastewater containing feces, urine, and flushwater from flush toilets * Blackwater fever, an acute kidney disea ...

. As blackwater cannot be purified by a

water treatment plant Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, includ ...

, it is stored in large impoundment ponds. Such ponds are susceptible to disastrous releases, such as the Buffalo Creek flood of 1972 or the Martin County coal slurry spill of 2000, which released over 250 million gallons of coal slurry. Coal slurry can contain hazardous chemicals such as arsenic and mercury and can kill aquatic wildlife, as was the case in the Martin County spill. This impounded liquid waste can sometimes total billions of gallons"Coal Sludge Impoundments, West Virginia."
NASA. NASA, 18 Mar. 2006. Retrieved 10 Apr. 2019. in a single facility.

References

External links

{{coal Coal mining Waste Environmental impact of the coal industry Water pollution Energy accidents and incidents

Preparation

Environmental concerns

See also

References

External links