Coal slurry
Coal slurry is a mixture of solids (mined coal or coal waste) and liquids (water or organic)[1] produced by a coal preparation plant.
Preparation
To transform the coal ash into a
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.[5][6]
Environmental concerns
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.[8] 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,[9] 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.[10] 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.[11] This impounded liquid waste can sometimes total billions of gallons[12] in a single facility.
The scope of coal slurry applications
To date, coal slurry fuels are recognised to have low energy density and therefore can only be successfully combusted in high compression engines such as diesel or gas turbine power plants (large engines with low energy density requirements). Other engine systems include slow speed diesel engines and turbines used as power plants for shipping and stationary electricity production.[13]
However, in the combustion market, for small and medium power plants range from 20 kW to 5 MW, the utilisation of CSs will require boiler’s retrofitting.[14]
Other applications found for these slurries are in systems such as boilers, gasifiers and stationary engines with specific requirements divided into two main areas: chemical and physical as shown in table below.
Aspect | Parameter | Application |
Fuel chemistry [15] | Low N < 0.6 wt% (db.)
Low S < 0.1 wt% (db.) (limit for corrosion) |
Boiler |
Ash<0.01% wt% (db.) | Diesel engine (No. 2 diesel fuel) | |
Bulk density 0.6-0.9 ton/m3 or higher | Boiler and gasifier | |
Physical and handling property [15] | Viscosity ≤1000 mPa.s at shear rate of 100s−1 at 25 °C (desirable for fuel handling). | Boiler |
See also
- Coal-water slurry fuel
- Pulverized coal
- Sludge (film)
- Tailings dam
References
- PMID 17276487.
- ^ Admin. "Transferring coal slurry made easy". www.globalpumps.com.au. Retrieved 11 April 2019.
- )
- ISSN 0016-2361.
- .
- PMID 17236802.
- ^ Conlon, Kevin (12 February 2014). "Officials: Coal slurry spill blackens 6 miles of West Virginia creek". CNN. Retrieved 2 May 2017.
- ^ Andrews, Graham F., and Karl S. Noah. "The Slurry-column Coal Beneficiation Process." Fuel Processing Technology 52.1-3 (1997): 247-66. Print.
- ^ 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
- ^ 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.
- ^ Leung, Rebecca. "A Toxic Cover-Up?" CBS News. CBS Interactive, 01 Apr. 2004. Web. 25 Apr. 2019.
- ^ "Coal Sludge Impoundments, West Virginia." NASA. NASA, 18 Mar. 2006. Retrieved 10 Apr. 2019.
- ^ Gary K Ellem (12 December 2023). "A NOVEL 2ND GENERATION LIQUID BIOFUEL PRODUCTION CONCEPT USING BIOMASS CHAR". Chemeca 2010: Engineering at the Edge; 26–29 September 2010, Hilton Adelaide, South Australia.
- ISBN 978-94-011-3844-4.
- ^ ISSN 0887-0624.