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Coal slurry is a mixture of solids (mined coal) and liquids (usually water) produced by a coal preparation plant. As a slurry, coal is separated from non-combustable components and can be fractionated by particle size as well. Coal slurry can be transferred by pipeline[1] or with specialised pumps such as a progressive cavity pump to pump the highly abrasive, corrosive and viscous coal slurry.[2]

The scale of water usage and hence potential costs and problems is large. More than 7 billion tons of coal are mined per year (2010), using approximately 200 litres of water per ton.[3]

Environmental concerns[edit]

A 2014 coal slurry spill into a river at Patriot Coal, West Virginia. A straw impoundment has been created across the river to try to hold the spillage.[4]

Ideally, coal slurry consists only of crushed coal 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[5]. Furthermore, the slurry consists also of very fine coal dust that results in a waste called blackwater. As blackwater cannot be purified by a water treatment plant[6], 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 ash slurry[7]. 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[8]. This impounded liquid waste can sometimes total billions of gallons[9] in a single facility.

References[edit]

  1. ^ Red Valve Company: Coal Slurry Pipeline
  2. ^ "Reasons why you should choose the right pump for coal slurry". 2012-07-18. Retrieved September 18, 2012.
  3. ^ D. Woodruff and L. Macnamara, "Treatment of coal tailings" in "The Coal Handbook: Towards Cleaner Production" D Osborne, Ed. Woodhead Publishing, 2013. Print ISBN 0-85709-422-X. Web ISBN 978-0-85709-730-9
  4. ^ Conlon, Kevin. "Officials: Coal slurry spill blackens 6 miles of West Virginia creek". CNN. Retrieved 2 May 2017.
  5. ^ Andrews, Graham F., and Karl S. Noah. "The Slurry-column Coal Beneficiation Process." Fuel Processing Technology 52.1-3 (1997): 247-66. Print.
  6. ^ Shiao-Hung Chiang and James T. Cobb "Coal Conversion Processes, Cleaning and Desulfurization" in Kirk-othmer Encyclopedia of Chemical Technology Wiley-VCH, 2000. doi:10.1002/0471238961.0312050103080901.a01
  7. ^ Kilborn, Peter T. "A Torrent of Sludge Muddies a Town's Future." The New York Times. The New York Times, 25 Dec. 2000. Web. 25 Apr. 2019.
  8. ^ Leung, Rebecca. "A Toxic Cover-Up?" CBS News. CBS Interactive, 01 Apr. 2004. Web. 25 Apr. 2019.
  9. ^ "Coal Sludge Impoundments, West Virginia." NASA. NASA, 18 Mar. 2006. Retrieved 10 Apr. 2019.