Transmitted and Reflected Visible Light Microscopy of Two Bituminous Fly Ashes

1984 ◽  
Vol 43 ◽  
Author(s):  
Donald L. Biggs ◽  
Joseph J. Bruns
Keyword(s):  
Fly Ash ◽  
Light Microscopy ◽  
Silicate Glass ◽  
Power Plants ◽  
Magnetic Fraction ◽  
Fly Ashes ◽  
Complete Replacement ◽  
Replacement Product ◽  
Nonmagnetic Particles ◽  
Ferrite Spinel

AbstractFly ashes of high magnetic content taken from two midwestern power plants were examined to determine the mineralogy of the magnetic and nonmagnetic fractions. Fly ash spheres from the magnetic fraction are predominantly composed of ferrite spinel, hematite and silicate glass. The hematite appears to be a replacement product of the original ferrite spinel. Nonmagnetic phases include mullite, lime, small amounts of hematite and silicate glass. Quartz morphology indicates that it did not fuse in the furnace. Mullite and lime have morphologies indicative of crystallization in the furnace. Hematite is bonded to the nonmagnetic particles or as a complete replacement of ferrite spinel spheres.

scholarly journals DETERMINING THE ROLE OF INDIVIDUAL FLY ASH PARTICLES IN INFLUENCING THE VARIATION IN THE OVERALL PHYSICAL, MORPHOLOGICAL, AND CHEMICAL PROPERTIES OF FLY ASH

2016 ◽  
Vol 56 (4) ◽  
pp. 265-282 ◽  
Author(s):  
Usman Haider ◽  
Zdenek Bittnar ◽  
Lubomír Kopecky ◽  
Vít Šmilauer ◽  
Jaroslav Pokorny ◽  
...  
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Chemical Properties ◽  
Cementitious Materials ◽  
Individual Particle ◽  
Particle Analysis ◽  
Fly Ashes ◽  
Alumino Silicate ◽  
Individual Particles

The properties of fly ashes vary because of the differences in the properties of their individual particles, and the determination of variation in these properties is of interest to the industries which use pulverized raw fly ash in applications, such as in cementitious materials and in the recovery of certain rare elements from raw fly ash. To investigate the differences in individual particles, four pulverized raw fly ashes from thermal power plants of the Czech Republic were used in this research. It was observed from FE-SEM that all four fly ashes consist of glassy hollow spherical, solid spherical, porous spherical, bright spherical, porous slaggy and compact slaggy particles. Box and whisker diagrams were plotted from the data of EDX individual particle analyses, which showed that the data of percentages for the Si, Al, and Fe elements is more scattered as compared to other elements. It was further observed from ternary phase diagrams and pseudo coloured images, that nature of fly ash particles changes from alumino silicate glassy to alumino silicate calcite metallic to pure ferro-metallic,where glassy particles showed high percentages and pure calcite particles were absent in fly ashes. Furthermore, a comparison between the XRF, the EDX total area analyses, showed that the EDX individual particle analysis gives more realistic and reliable data with median, mean, and the standard deviation for percentages of each element present in the fly ashes.

Studies on the Leaching and Weathering Processes of Coal Ashes

1983 ◽  
Vol 15 (11) ◽  
pp. 163-191 ◽  
Author(s):  
Hay Leim ◽  
Magnusöm Sandstr ◽  
Tom Wallin ◽  
Anders Carne ◽  
Ulla Rydevik ◽  
...  
Keyword(s):  
Power Plants ◽  
Coal Ash ◽  
Mass Action ◽  
Equilibrium Analysis ◽  
Metal Leaching ◽  
Magnetic Fraction ◽  
Fly Ashes ◽  
X Ray ◽  
Weathering Processes ◽  
Coal Ashes

Within the Swedish project Coal-Health-Environment (Kol-Hälsa-Mi1jö) leaching studies were made on several types of coal ashes, fly ashes, bottom ashes and scrubber sludges. Studies were made on the effects of pH, pCl, pCO3. pEDTA and pSO4, in the leaching solution on the leaching of metals from coal ashes. As a model for the leaching system, we studied the leaching of Cr, Co, Ni, tu, Zn, Mo, Se, As, Cd and Pb. The leaching of the metals was found to increase with pH for pH less than 2 and pH greater than 9, and to decrease for 2 > pH > 6. The metal leaching behaviour may in part be explained by the mass-action law. We have also made long-term leaching tests of several coal ashes from Danish and Finnish Power Plants using leaching water of different pH. The dominating crystalline phases in the different coal ashes have been identified by X-ray diffraction technique. The major species in the different coal ashes were found to be mullite (3A12.2SiO2), α-quartz (Sio2) and the iron oxides magnetite and hematite. Leaching and X-ray studies were also made on the magnetic fraction of the fly ashes. Equilibrium analysis were made on the system Me-OH-Cl-CO32− - SO42−, where Me = Cr, Co, Ni, Cu, Zn, Mo, Se, As, Cd and Pb, partly using the computer program HALTAFALL. A model for the metal leaching from a coal ash deposit will be discussed.

The Suitability of Fly Ash for Use in Concrete According to EN 450 Based on their Particle Size

2018 ◽  
Vol 276 ◽  
pp. 110-115
Author(s):  
Martin Ťažký ◽  
Martin Labaj ◽  
Rudolf Hela
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Catalytic Reduction ◽  
Raw Materials ◽  
Thermal Power ◽  
Combustion Process ◽  
Thermal Power Plants ◽  
Mechanical Parameters ◽  
Fly Ashes ◽  
The Impact

The by-products of energy industry are nowadays often affected by new limits governing the production of harmful gases discharged into the air. These stricter and stricter criteria are often met by electricity producers by changing the combustion process in thermal power plants itself. Nowadays, the SNCR (selective non-catalytic reduction) application is quite common in the combustion process in order to help reduce the nitrogen oxide emission. This article deals with the primary measures of thermal power plants, which in particular consist of a modified treatment of raw materials (coal) entering the combustion process. These primary measures then often cause the formation of fly ash with unsuitable fineness for the use in concrete according to EN 450. The paper presents the comparison of the physico-mechanical parameters of several fly ashes with a different fineness values. The primary task is to assess the impact of non-suitable granulometry in terms of EN 450 on the other physico-mechanical parameters of fly ashes sampled within the same thermal power plant. Several fly ashes produced in the Czech Republic and surrounding countries were evaluated in this way.

Characterization of North American Lignite Fly Ashes II. XRD Mineralogy

1987 ◽  
Vol 113 ◽  
Author(s):  
G. J. McCarthy ◽  
D. M. Johansen ◽  
A. Thedchanamoorthy ◽  
S. J. Steinwand ◽  
K. D. Swanson
Keyword(s):  
Fly Ash ◽  
Bituminous Coal ◽  
Coal Fly Ash ◽  
Fly Ashes ◽  
X Ray ◽  
Mining Areas ◽  
Lignite Fly Ash ◽  
Coal Fly Ashes ◽  
Ferrite Spinel

ABSTRACTX-ray powder diffraction has been used to determine the crystalline phase mineralogy in samples of fly ash from each of the lignite mining areas of North America. The characteristic phases of North Dakota lignite fly ashes were periclase, lime, merwinite and the sulfate phases anhydrite, thenardite and a sodalite-structure phase. Mullite was absent in these low-Al2O3 ashes. Montana lignite ash mineralogy had characteristics of ND lignite and MT subbituminous coal fly ashes; mullite and C3A were present and the alkali sulfates were absent. Texas and Louisiana lignite fly ashes had the characteristic mineralogy of bituminous coal fly ash: quartz, mullite, ferrite-spinel (magnetite) and minor hematite. Even though their analytical CaO contents were 7–14%, all but one lacked crystalline CaO-containing phases. Lignite fly ashes from Saskatchewan were generally the least crystalline of those studied and had a mineralogy consisting of quartz, mullite, ferrite spinel and periclase. Quantitative XRD data were obtained. The position of the diffuse scattering maximum in the x-ray diffractograms was indicative of the glass composition of the lignite fly ash.

scholarly journals Synthesis and sintering of high-temperature composites based on mechanically activated fly ash

2012 ◽  
Vol 44 (2) ◽  
pp. 135-146 ◽  
Author(s):  
A. Terzic ◽  
Lj. Pavlovic ◽  
N. Obradovic ◽  
V. Pavlovic ◽  
J. Stojanovic ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Fly Ash ◽  
Mechanical Activation ◽  
Power Plants ◽  
Sem Analysis ◽  
Fly Ashes ◽  
Physico Chemical ◽  
Fly Ash Utilization ◽  
And Behavior

Amount of fly ash which is and yet to be generated in the coming years highlights the necessity of developing new methods of the recycling where this waste can be reused in significant quantity. A new possibility for fly ash utilization is in high-temperature application (thermal insulators or/and refractory material products). As such, fly ash has to adequately answer the mechanical and thermal stability criteria. One of the ways of achieving it is by applying mechanical activation procedure on fly ash. In present study, fly ashes from two different power plants were mechanically activated in a planetary ball mill. Mechanically treated fly ashes were cemented with two different binders: standard Portland cement and high-aluminates cement. Physico-chemical analysis and investigation of mineralogical components of composites are emphasized, due to the changes occurred in fly ash during mechanical activation and sintering of composites. Macro-performance of the composites was correlated to the microstructure of fly ash studied by means of XRD and SEM analysis. Thermal stability of crystalline phases was investigated with DTA. Highlight was placed on determination of relationship between mechanically activated fly ash and obtained composites microstructure on one side and behavior of sintered composites on the other side.

scholarly journals Separation of Cenospheres from Fly Ashes by Floatation Method

2010 ◽  
Vol 13 (1-2) ◽  
pp. 89 ◽  
Author(s):  
L.M. Manоcha ◽  
K.A. Ram ◽  
S.M. Manocha
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Ceramic Particle ◽  
Composition Analysis ◽  
High Concentration ◽  
Fly Ashes ◽  
Power Station ◽  
Different Types ◽  
Chemical Composition Analysis

Fly-ashes are non-combustible mineral residues which are produced from coal in thermal power plants. Four different types of fly ashes were collected from different power station in Gujarat. Characterization through SEM shows that fly ash contains cenosphere i.e. gas bubble containing ceramic particle independent of their bulk density. Floatation technique was used for the separation of cenosphere from fly ash. Two solvents with extremely different densities were used for the separation of cenospheres. All methods gave approximately yield of less than 1 % cenosphere in fly ash. Color of cenospheres varied from gray to almost white and the value of density range from 0.4 – 0.8 g/cc. Further, chemical composition analysis revealed that cenospheres do not contain any high concentration of hazardous elements.

scholarly journals Stabilization of Indian Fly Ashes with Soils, Cement, and Randomly Oriented Fibers

2012 ◽  
Vol 3 ◽  
pp. 1-8
Author(s):  
Shenbaga R. Kaniraj ◽  
V. Gayathri ◽  
V.G. Havanagi
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Experimental Studies ◽  
Fly Ashes ◽  
Strength Criteria ◽  
Permeability Characteristics ◽  
Polyester Fibers ◽  
Soil Mixtures ◽  
Pavement Base

 Experimental studies were carried out on fly ashes from two Indian thermal power plants, namely Rajghat and Dadri, with the aim of improving the utilization of fly ash in geotechnical engineering applications. It was attempted to improve the engineering performance of fly ash by several means such as by mixing fly ash with soils, cement, and polyester fibers. The research program included the study of: a) physical properties, chemical composition and morphology of the fly ashes; b) compaction, strength, and permeability characteristics of the fly ashes and fly ash-soil mixtures; c) compaction and strength characteristics of fly ash-soil mixtures stabilized with fibers alone, with cement alone, and with both cement and fibers. Results showed that addition of fly ash to soils would result in lighter and stronger fills. Fiber inclusions increased the strength of fly ash-soil specimens significantly and altered their behaviour from brittle to ductile. Even small cement contents increased the strength of the fly ash-soil mixtures significantly. With higher cement contents of up to 18% it was possible to prepare fly ash-cement design mixes that satisfied the strength criteria for pavement base courses.

STUDY OF FLY ASH FROM POWER GENERATING ENTERPRISES TO USE IT AS AN ALTERNATIVE TO LIME MINERAL FILLER FOR THE PRODUCTION OF ASPHALT MIXTURES

2021 ◽  
Vol 2021 (24) ◽  
pp. 40-47
Author(s):  
Ivan Kopynets ◽  
◽  
Volodymyr Kaskiv ◽  
Оleksii Sokolov ◽  
◽  
...  
Keyword(s):  
Power Plants ◽  
Thermal Power ◽  
Asphalt Mixtures ◽  
Fine Aggregate ◽  
Fly Ashes ◽  
Complete Replacement ◽  
Different Origins ◽  
Mineral Fillers ◽  
Mine Dump

Introduction. Asphalt mixtures are one of the most widely used materials in the construction of roads. For the production of these mixtures, mainly conditioned mineral materials are used — coarse aggregate, fine aggregate and filler, and bitumen is used as a binder. Problem statement. In Ukraine, the filler is mainly used material obtained by grinding the carbonate rocks, which is established in DSTU B V.2.7-119 and DSTU B V.2.7-121. At the same time, as a result of coal combustion, millions of tons of dusty waste are generated at power generating plants of Ukraine - fly ashes and ashes from the hydraulic mine dump. These materials are close by grading to the requirements for the filler in accordance with DSTU B V.2.7-121 and probably can be used for the production of asphalt mixtures. Purpose. Determination of the possibility of using the fly ashes for the production of asphalt mixtures. Materials and methods. Type B asphalt concrete and mineral fillers of different origins were used during the research. Results. Test results showed that the studied fly ashes can be used for the production of asphalt mixtures, because the complete replacement of limestone filler with fly ashes from the thermal power plants does not lead to the deterioration of asphalt mixtures properties.

scholarly journals Influence of Activators on Mechanical Properties of Modified Fly Ash Based Geopolymer Mortars

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1033 ◽  
Author(s):  
Piotr Prochon ◽  
Zengfeng Zhao ◽  
Luc Courard ◽  
Tomasz Piotrowski ◽  
Frédéric Michel ◽  
...  
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Biomass Combustion ◽  
Fly Ashes ◽  
Binding Properties ◽  
Alkali Activated ◽  
Modified Fly Ash ◽  
Scanning Electron ◽  
And Calorimetry

The aim of this work was to study the influence of the type of activator on the formulation of modified fly ash based geopolymer mortars. Geopolymer and alkali-activated materials (AAM) were made from fly ashes derived from coal and biomass combustion in thermal power plants. Basic activators (NaOH, CaO, and Na2SiO3) were mixed with fly ashes in order to develop binding properties other than those resulting from the use of Portland cement. The results showed that the mortars with 5 mol/dm3 of NaOH and 100 g of Na2SiO3 (N5-S22) gave a greater compressive strength than other mixes. The compressive strengths of analyzed fly ash mortars with activators N5-S22 and N5-C10 (5 mol/dm3 NaOH and 10% CaO) varied from 14.3 MPa to 5.9 MPa. The better properties of alkali-activated mortars with regular fly ash were influenced by a larger amount of amorphous silica and alumina phases. Scanning electron microscopy and calorimetry analysis provided a better understanding of the observed mechanisms.

scholarly journals Distribution of Lanthanides, Yttrium, and Scandium in the Pilot-Scale Beneficiation of Fly Ashes Derived from Eastern Kentucky Coals

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 105 ◽  
Author(s):  
James C. Hower ◽  
John G. Groppo ◽  
Prakash Joshi ◽  
Dorin V. Preda ◽  
David P. Gamliel ◽  
...  
Keyword(s):  
Rare Earth ◽  
Fly Ash ◽  
Power Plants ◽  
Pilot Scale ◽  
Fly Ashes ◽  
Eastern Kentucky ◽  
Minor Elements ◽  
High Concentrations ◽  
The Individual ◽  
Plant Basis

In this study, Central Appalachian coal-derived fly ashes from two power plants were beneficiated in a pilot-scale facility in order to produce a product with a relatively consistent concentration of rare earth elements (REE). The <200-mesh final fly ash product was produced by removing the carbon- and Fe-rich particles prior to screening at 200 mesh (75 µm). The Plant D fly ash had high concentrations of CaO and SO3, which were diminished through the two months when the ash was being beneficiated, representing a consequence of the heat, humidity, and excessive rainfall in the Kentucky summer. The high CaO and SO3 concentrations through the early runs likely contributed to the lower REE in the <200-mesh products of those runs. Of the non-REE minor elements, Ba, V, Mn, Zn, and As showed the greatest between-run variations within the runs for each plant. The overall REE concentrations proved to be similar, both on a between-run basis for the individual fly ash sources and on a between-plant basis. Variations in fly ash quality will occur in larger-scale operations, so on-going attention to the fly ash quality and the response of the fly ash to beneficiation is necessary. Changes in the Plant D fly ash with time imply that both the freshness of the original ash and the length and conditions of its storage at the site of beneficiation could be factors in the quality and consistency of the processed fly ash.

Sign in / Sign up

Export Citation Format

Share Document