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Underground soft rock mining
Published in A.J.S. (Sam) Spearing, Liqiang Ma, Cong-An Ma, Mine Design, Planning and Sustainable Exploitation in the Digital Age, 2023
A.J.S. (Sam) Spearing, Liqiang Ma, Cong-An Ma
Liners (or similar such as blankets, geofabrics and geotubes) are now commonly used for most ash ponds, and if correctly built, they limit the leaching caused by percolation resulting from rainfall. Water overtopping is a serious potential issue, and the design should be such that this can be avoided even under extreme weather events.
Thermal Power Generation
Published in T.M. Aggarwal, Environmental Control in Thermal Power Plants, 2021
Fly ash handling systems may be generally categorized as dry or wet, even though the dry handling system involves wetting the ash to 10–20% moisture to improve handling characteristics and to mitigate the dust generated during disposal. In wet systems, the ash is mixed with water to produce a liquid slurry containing 5–10% solids by weight. This is discharged to settling ponds, often with bottom ash and FGD sludges, as well. The ponds may be used as the final disposal site, or the settled solids may be dredged and removed for final disposal in a landfill. Wherever feasible, decanted water from ash disposal ponds should be recycled to formulate ash slurry. Where heavy metals are pre-sent in ash residues or FGD sludgse, care must be taken to monitor and treat leachates and overflows from settling ponds. In addition to disposing of them in lined places to avoid contamination of water bodies. In some cases, ash residues are being used for building materials and in road construction. Gradual reclamation of ash ponds should be practiced.
Constructed Wetlands for Treatment of Ash Pond Seepage
Published in Donald A. Hammer, Constructed Wetlands for Wastewater Treatment, 2020
Gregory A. Brodie, Donald A. Hammer, David A. Tomljanovich
Coal processing and transporting and coal ash storage frequently results in acid drainage similar to seepage from surface and underground mine areas. Ash storage pond seepage has concentrations of metallic ions similar to acid mine drainage (AMD), but the aggregate flow from many seeps along one ash pond dike may be orders of magnitude greater than individual mine drainage seeps. Typically the Tennessee Valley Authority (TVA) ash pond seeps have pHs of 3–6, total iron (Fe) of 100–200 mg/L and total manganese (Mn) of 5–10 mg/L, but Fe may be 300–400 mg/L and Mn may be 70–80 mg/L and flows range from 500–2000 L/min. Ash pond seeps may also contain other contaminants such as Se, Be, Al, and heavy metals.
Targeting ash generated from coal combustion as secondary source of rare earth elements
Published in International Journal of Coal Preparation and Utilization, 2023
Akshay Kumar Singh Choudhary, Santosh Kumar, Raj Vardhan Sharma, Manavalan Satyanarayanan, Sudip Maity
Coal fly ash (CFA) has emerged as one of the best alternative resources for REE. In modern Indian thermal power stations (TPS) mostly bituminous rank coal is used which has a typical ash percentage between 30% and 45% (Yousuf et al. 2020). More than 80% of coal combustible products is CFA, and the remaining 20% is bottom ash (BA) (Cwirzen 2020). In India, more than 270.82 MT of CFA was generated in 2021–22, of which 95.95% was utilized, having average ash content of 35.68% (undefined). This still leaves us with millions of tons of unutilized coal ash (CA) which has to be disposed of in landfills or engineered structure used at TPPs known as an “ash pond” which contaminate land, air, and water resources. It is high time to maximize the target for waste-to-wealth toward sustainable development of the environment and humanity as a whole.
Environmental hazard assessment of coal ash disposal at the proposed Rampal power plant
Published in Human and Ecological Risk Assessment: An International Journal, 2018
Moreover, monitoring of HCSD sites in the United States (multiple ponds in a disposal system) confirms major leaching and contamination of groundwater from the “paste matrix” that forms in HCSD (PPL 2013). Unlined disposal ponds cause pollution of groundwater, which can contaminate public and private water wells, and also move to the surface through seeps and springs where it will expose fish and wildlife to toxins. A lined pond, which is proposed for the Rampal Plant, may retard seepage into groundwater but the “containment” feature afforded by a liner means that there is an accumulation of water from rainfall, analogous to plugging a bathtub with the shower left running. The trapped water has to go somewhere. The bathtub will eventually overflow, as will the ash pond. The result is that a lined, uncapped, open surface HCSD ash pond allows overflow of accumulated precipitation, which would be a major concern in Rampal due to its high annual rainfall. Also, the occurrence of monsoons would likely lead to seasonal flooding and associated overflow of contaminated water from the disposal pond. Overflow from the ash pond would be highly contaminated due to leaching of toxins. Moreover, the Rampal site is in a “wind risk zone” and is vulnerable to storm surges of 7.4 m that could easily result in catastrophic failure of the impoundment (BPDP 2013, page 120; BIFPCL Rampal Tender Document B9, page 52; Jacob 2016).
Controlled Low-Strength Materials (CLSM) as backfill: experimental investigation on CLSM properties and numerical evaluation of stresses and strains using PLAXIS 2D
Published in Geomechanics and Geoengineering, 2022
Lini Dev K, Akhilesh Kumar, Chandan Kumar Singh
One of the main drawbacks of industrial revolution is the generation of huge quantity of wastes because of improper planning in the industrial sector. This generation of wastes has led to environmental pollution and is the main concern for all the manufacturing and processing industries. One of the major contributors of these industrial wastes are the thermal power plants in India. The huge production of electricity from the coal ash-based thermal power plants has led to production of coal ashes. As per the Central Electricity Authority (CEA) report (2020), nearly 217.04 million metric tons of coal ashes are produced in 2018–19 in India. This current production is about to cross 600 million metric tons by 2032. The deposition of coal ashes in ash ponds is an issue for the environmentalists as it leads to serious environmental issues such as air pollution, water pollution and soil degradation. Even though fly ash is used for different applications such as replacement for cement in construction industry, reclamation of low-lying areas, manufacturing of bricks, and backfilling applications, as per Bhatt et al. (2019) utilisation of fly ash for different applications in India is only about 50% of its total production. Pond ash, which is also a by-product from the thermal power stations, is typically considered a waste material and usually gets deposited in ash ponds. In order to avoid the severe disadvantages caused by the disposal of pond ash in ash ponds, it can be reutilised in some other forms. The reutilisation of these industrial by-products for other applications in civil engineering will help to preserve the raw resources and avoid the negative impacts related to acquisition and processing of these raw materials.