Bottom ash
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Bottom ash is part of the non-
Most bottom ash generated at U.S. power plants is stored in ash ponds, which can cause serious environmental damage if they experience structural failures.
Ash handling processes
In a conventional
More modern systems adopt a continuous removal philosophy. Essentially, a heavy duty chain conveyor submerged in a water bath below the furnace which quenches hot ash as it falls from the combustion chamber and removes the wet ash continuously up to a de-watering slope before onward discharge into mechanical conveyors or directly to storage silos.
Modern municipal waste incinerators reduce the production of
Waste handling
In United States facilities, the ash waste is typically pumped to ash ponds, the most common disposal method.[1] Some power plants operate a dry disposal system with landfills.
Environmental impacts
In the United States, coal ash is a major component of the nation's industrial waste stream.[2] In 2017, 38.2 million short tons (34.7×10 6 t) of fly ash, and 9.7 million short tons (8.8×10 6 t) of bottom ash were generated.[3] Coal contains trace levels of arsenic, barium, beryllium, boron, cadmium, chromium, thallium, selenium, molybdenum and mercury, many of which are highly toxic to humans and other life. Coal ash, a product of combustion, concentrates these elements and can contaminate groundwater or surface waters if there are leaks from an ash pond.[4]
Most U.S. power plants do not use
Ash recycling
Bottom ash can be extracted, cooled and conveyed using dry ash handling technology. When left dry the ash can be used to make concrete, bricks and other useful materials. There are also several environmental benefits.[11]
Bottom ash may be used as raw alternative material, replacing earth or sand or aggregates, for example in
See also
References
- ISBN 9780872626041.
- ^ "Coal Ash Basics". EPA. 2021-01-25.
- ^ 2017 Coal Combustion Product Production & Use Survey Report (PDF) (Report). Farmington Hills, MI: American Coal Ash Association. 2018. Archived from the original (PDF) on 2019-05-07. Retrieved 2019-06-17.
- ^ Schlossberg, Tatiana (2017-04-15). "2 Tennessee Cases Bring Coal's Hidden Hazard to Light". The New York Times.
- .
- ^ "EPA Letting Some Hazardous Coal Ash Ponds Stay Open Longer". U.S. News. 2020-10-16.
- ^ EPA. "Hazardous and Solid Waste Management System: Disposal of Coal Combustion Residuals From Electric Utilities; A Holistic Approach to Closure Part A: Deadline To Initiate Closure." Federal Register, 85 FR 53516. 2020-08-28.
- ^ "Revisions to the Coal Combustion Residuals (CCR) Closure Regulations; Fact sheet". EPA. July 2020.
- ^ EPA (2020-11-12). "Hazardous and Solid Waste Management System: Disposal of CCR; A Holistic Approach to Closure Part B: Alternate Demonstration for Unlined Surface Impoundments." Final rule. 85 FR 72506
- ^ Smoot, D.E. (2020-12-11). "Groups challenge rollback of coal ash rule". Muskogee Phoenix. Muskogee, OK.
- ^ "Coal Ash Reuse". EPA. 2021-01-25.
External links
- EcoSmart Concrete – Use of fly ash and other supplementary cementing materials in concrete
- LondonWaste – How bottom ash is processed to make aggregate