Fly Ash Collected from Electrostatic Precipitators: Microcrystalline Structures and the Mystery of the Spheres

Abstract

Scanning electron micrographs demonstrate the presence of microcrystalline structures on the surface of coal-derived fly ash samples taken from electrostatic precipitator hoppers. Cenospheres (hollow spheres) were found to be packed with smaller cenospheres, which were also packed with spheres. Microspheres, apparently formed by uneven heating, are encapsulated in the parent sphere. Chemical analyses provide a basis for the postulation of a mechanism of formation for plerospheres (hollow spheres packed with spheres) and microcrystals.

Combustion Aerosols: Factors Governing Their Size and Composition and Implications to Human Health

“…In addition, a large number of the particles will form cenospheres (hollow spheres) or plerospheres (hollow sphere surrounding a number of spherical ash particles). 83,112,127,128 The mechanism for the cenosphere is the formation of gas within the ash particle in a temperature window where the viscosity is low enough to favor the bubble growth but not so low as to have the gas escape and the bubble collapse. One mechanism for cenosphere formation identified by Raask 128 is the reaction within the ash of iron oxide with carbon to form CO.…”

Determination of adsorption efficiency based on cation exchange capacity related to red earth, bone meal and pulverised fly ash as ameliorants to lead contaminated soils

“…PFA also provides a source of extractable P and increase CEC. Fly ash particles are characterised with physical structures consisting of "hollow spheres" which show an increased surface area, capillary action, and nutrientholding capacity compared with sands (Fisher et al, 1976). Interest in the use of fly ash as a soil amendment (or ameliorant) results from (i) the need to develop sustainable uses of this by-product (Adriano et al, 1980;Bilski et al, 1995) and (ii) reports showing improved growth of some crops (El-Mogazi et al, 1988;Rees and Sidrak, 1956), pasture (Hill andLamp, 1980 andSummers et al, 1998), and after turf species Weber, 2001 andPathan et al, 2001), following addition of fly ash to some soils.…”

Trace-element geochemistry of coal resource development related to environmental quality and health

“…The major components of fly ash--silicon, aluminum, calcium, magnesium, iron, sodium, potassium, and titanium--make up from 35 to 70 percent of the total elemental composition of fly ash. Fisher et al (1976) indicated that the composition of fly ash from western , U.S. coals could be approximated by the formula,. Dams (1975), Bern (1976), Swaine (19771, Martens (1971), Mulford and Martens (1971) Soil composition was derived mainly from Bowen (1966) and Lisk (1972).…”

“…Scanning electron microscopic (SEM) observation of fly ash reported by Fisher et al (1976) demonstrated that fly ash is composed of large, hollow, spherical, aluminosilicate particles called plerospheres (or cenospheres), which have smaller particles attached to their surfaces and enclosed within their cavities. SEM studies conducted by Page & a.…”