Clay and pyrite transformations during ignition of pulverised coal

Hubbard, F. H.

doi:10.1180/minmag.1984.048.347.09

Cited by 21 publications

(10 citation statements)

References 1 publication

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“…also points to a close link between survival of the magnetic record and the degree to which peat has dried out along the edge of drainage gulleys. Hubbard et al (1984) note that whereas magnetite forms during the coal combustion process and is characteristic of the outer rim of the spheres produced, haematite is more likely to be a residual survivor from the original mineral content of the coal. This may contribute to selective survival.…”

Section: Questions Of Survivalmentioning

confidence: 99%

The magnetic record of inorganic fly ash deposition in lake sediments and ombrotrophic peats

et al. 2014

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Interest in identifying a geological marker signifying the starting point for the Anthropocene has prompted an exploration of the stratigraphic record of inorganic particulates generated by industrial activities. Magnetic measurements of recent lake sediments and ombrotrophic peats are here used to reconstruct the history of deposition of inorganic fly ash spheres resulting mainly from solid fuel combustion and metal smelting. The chronologies used have been based on moss-increment counting, radioisotope dating and pollen analysis. The sites come from the United Kingdom, Scandinavia and North America. In several cases where detailed chronologies of both fly ash deposition and local industry can be compared, the sequence of concentration-linked magnetic measurements appears to capture accurately the record of industrial development despite incontrovertible evidence from other peat based records for some selective dissolution of magnetic minerals. The dates at which magnetic concentration increases begin range from the 16 th century in the peat profiles around the head of Morecambe Bay, South Cumbria, in North-West England where early iron manufacture using charcoal-fuelled bloomery hearths is well documented, to the mid 20 th century at the remotest sites in Arctic Scandinavia. The lake sediment profiles used here come mainly from the United Kingdom and, in most cases, they date increases to the late 19 th century or the first decades of the 20 th century. Any attempt to use the magnetic record of fly ash deposition in lake sediments and/or peats to mark the date chosen as the onset of the Anthropocene would require careful choice of site location and archive, bearing in mind the issue of selective magnetic mineral dissolution.

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Section: Questions Of Survivalmentioning

confidence: 99%

The magnetic record of inorganic fly ash deposition in lake sediments and ombrotrophic peats

et al. 2014

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“…This mineral assemblage is typical of low-Ca fly ash derived from combustion of bituminous or sub-bituminous coal; it is far less complex than that of fly ash resulting from lignite coal combustion (Hubbard et al 1984;McCarthy 1988;McCarthy et al 1988;Enders 1996;Bosbach and Enders 1998;Hower et al 1999).…”

Section: X-ray Characterizationmentioning

confidence: 99%

“…The BSE images further revealed that the spherical particles are either hollow (cenospheres) or filled, or that they contain a series of smaller spheres (plerospheres). These morphological charac- teristics are typical of fly ash produced through coal combustion (e.g., Hulett and Weinberger 1980;Smith 1980;Hubbard et al 1984;Fishman et al 1999;Hower et al 1999).…”

Section: Microscopic Characterizationmentioning

confidence: 99%

“…Most of these particles can be identified optically as quartz. Discrete grains of quartz are common in fly ash, and represent entrained material, i.e., a mineral that was present in the coal and survived the brief exposure to high temperature during combustion (Hubbard et al 1984).…”

Section: Microscopic Characterizationmentioning

confidence: 99%

“…small, and thus cannot easily be analyzed chemically. Consequently, there are only relatively few studies that examined the physical and chemical properties of individual particles (e.g., Linton et al 1977;Hulett and Weinberger 1980;Smith 1980;Hubbard et al 1984;Ainsworth et al 1993;Demanet 1995;Bosbach and Enders 1998;Vincze et al 2002). It is the purpose of this paper to report results of an investigation into physical form, chemical composition, and structure of individual fly ash particles.…”

Section: Introductionmentioning

confidence: 95%

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Micro- and nanochemistry of fly ash from a coal-fired power plant

Gieré

Carleton

Lumpkin

2003

American Mineralogist

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Fly ash from a coal-fired power plant was investigated to obtain detailed information on its physical and chemical properties, and to gain an understanding of potential environmental and health impacts associated with its disposal in landfills. The studied material was produced through combustion of Illinois Basin coal and trapped within the power plant by an electrostatic precipitator. It is a finegrained, low-Ca fly ash containing primarily SiO 2 , Al 2 O 3 , and Fe 2 O 3 , and is enriched in many toxic elements (e.g., Be, Zn, As, Cd, Tl, Pb, and U) by a factor of up to 30 relative to coal. The ash consists of mainly hematite, magnetite, mullite, quartz, and amorphous material. These constituents occur mostly as spherical particles with diameters of less than 13 mm. We examined the physical, chemical, and structural characteristics of individual fly ash particles by scanning and transmission electron microscopy and electron probe microanalysis. The results demonstrate that, with the exception of complex plerospheres, individual particles are chemically fairly homogeneous, but a pronounced compositional variation exists among particles with similar physical and structural attributes. Electron microprobe data document that several trace elements, including U, are partitioned into the Ferich particles. Transmission electron microscopy revealed that various types of small (<1 mm) crystalline Ca-rich phases, including lime, are attached to the glass spheres, particularly the nonmagnetic glass. These crystals may contain substantial amounts of S. Even though only a few of these crystals were analyzed quantitatively, our data indicate that the Ca-rich and S-rich phases may be important hosts for trace elements such as V and Zn. The observed element partitioning and the existence of surface-attached crystals enriched in certain trace elements suggest that fly ash from coal-fired power plants might have a more deleterious environmental impact than is inferred from bulk analytical data.

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A compositional index of the pozzolanic potential of pulverized-fuel ash

Hubbard

Dhir

1984

J Mater Sci Lett

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Clay and pyrite transformations during ignition of pulverised coal

Cited by 21 publications

References 1 publication

The magnetic record of inorganic fly ash deposition in lake sediments and ombrotrophic peats

The magnetic record of inorganic fly ash deposition in lake sediments and ombrotrophic peats

Micro- and nanochemistry of fly ash from a coal-fired power plant

A compositional index of the pozzolanic potential of pulverized-fuel ash

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