Mineralogical and Chemical Composition of CFB Fly Ash Derived from Co-Combustion of Xylite and Biomass (original) (raw)
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Fuel, 2007
The chemical and mineralogical composition of fly ash samples collected from different parts of a laboratory and a pilot scale CFB facility has been investigated. The fabric filter and the second cyclone of the two facilities were chosen as sampling points. The fuels used were Greek lignite (from the Florina basin), Polish coal and wood chips. Characterization of the fly ash samples was conducted by means of X-ray fluorescence (XRF), inductive coupled plasma-optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), particle size distribution (PSD) and X-ray diffraction (XRD). According to the chemical analyses the produced fly ashes are rich in CaO. Moreover, SiO 2 is the dominant oxide in fly ash with Al 2 O 3 and Fe 2 O 3 found in considerable quantities. Results obtained by XRD showed that the major mineral phase of fly ash is quartz, while other mineral phases that are occurred are maghemite, hematite, periclase, rutile, gehlenite and anhydrite. The ICP-OES analysis showed rather low levels of trace elements, especially for As and Cr, in many of the ashes included in this study compared to coal ash from fluidised bed combustion in general.
Journal of Hazardous Materials, 2009
The chemical and mineralogical composition of fly ash samples collected from laboratory scale circulating fluidised bed (CFB) combustion facility have been investigated. Three fly ashes were collected from the second cyclone in a 50 kW laboratory scale boiler, after the combustion of different solid fuels. Characterisation of the fly ash samples was conducted by means of X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Quantitative analysis of the crystalline (mineral) and amorphous phases in each ash sample was carried out using the Rietveld-based Siroquant system, with an added spike of ZnO to evaluate the amorphous content. SiO 2 is the dominant oxide in the fly ashes, with CaO, Al 2 O 3 and Fe 2 O 3 also present in significant proportions. XRD results show that all three fly ashes contain quartz, anhydrite, hematite, illite and amorphous phases. The minerals calcite, feldspar, lime and periclase are present in ashes derived from Polish coal and/or woodchips. Ash from FBC combustion of a Greek lignite contains abundant illite, whereas illite is present only in minor proportions in the other ash samples.
The fuel, bed ash, and fly ash were sampled from a circulating fluidized bed combustion (CFBC) unit at two times. The first sampling was a high-sulfur (S) coal-only run, and the second sampling coincided with an experimental burn of up to 10% switchgrass (Panicum virgatum) pressed pellets mixed with a highS coal. The latter blend had a higher moisture content and a lower heating value than the coal-only fuel. Given the time between the samplings and the special needs for the experimental run, unavoidable changes in the coal and limestone complicate comparisons of the bed ash and fly ash chemistry between the sampling times. The bed ash is dominated by CaO and SO 3 , and the fly ash has a higher CaO content than would be expected for a pulverized-coal burn of the same coal. The fly ash chemistry bears a superficial resemblance to class C fly ashes, but given the different combustion conditions and consequent differences in the ash mineralogy, the fly ash should not be considered to be a class C ash. The bed ash mineral assemblages consist of anhydrite, mullite, portlandite, and anorthite, while the fly ash has less portlandite and more anorthite than the bed ash.
Morphology and mineralogy of fly ash from a coal-fueled power plant
Meteorology and Atmospheric Physics, 1984
Morphology, chemical composition and mineralogy of fly ash from a coal-fueled power plant have been investigated. Optical and scanning electron microscopic examinations on both untreated particle samples and thin sections have enabled the investigation of internal and superficial microstructure. Chemical and diffractometric analyses performed on fly ash samples, fractionated by means of magnetic and gravimetric separators, associated the particle morphology to the elemental and mineralogical composition. A classification of single particles was achieved as follows: 1) glassy aluminosilicate with avariable composition; 2) spongy carbonaceous; 3) spherical metallic particles constituted of different iron oxide phases (magnetite, hematite, maghemite); 4) spherical rutile particles; 5) spherical lime particles; 6) mineral formless particles (i.e. quartz and mullite). The mineralogical composition of the coal utilized during instack samplings is also given. Lastly a correlation between the crystalline and amorphous particles constituing the fly ash and the mineral matter present in the burnt fuel has been proposed. Es sind die Morphologie, die chemische Zusammensetzung und die Mineralogie der Flugasche von einem Kohlekraftwerk untersucht worden. Optische und elektronenmikroskopische Untersuchungen von unbehandelten Teilchenproben und von Dünnschnitten haben die Erforschung der inneren und der oberflächlichen Mikrostruktur ermöglicht. Chemische und diffraktometrische Analysen, durchgeführt an Flugascheproben, fraktioniert mittels magnetischer und gravimetrischer Scheider, stellten eine Verbindung der Teilchenmorphologie mit der die Elemente betreffenden und mineralogischen Zusammensetzung her. Folgende Klassifikation der einzelnen Teilchen wurde erhalten: 1. glasige Aluminosilikate mit einer wechselnden Zusammensetzung, 2. absorbierende kohlenstoffhaltige Teilchen, 3. kugelförmige aus verschiedenen Eisenoxydphasen (Magnetft, Hämatit, Maghämit) zusammengesetzte metallische Teilchen, 4. kugelförmige Rutilteilchen, 5. kugelförmige Kalkteilchen, 6. mineralisch formlose Teilchen wie Quarz und Mullit. Die mineralogische Zusammensetzung der Kohle wird mit Verwendung von im Schornstein entnommenen Proben auch angegeben. Schließlich wird eine Korrelation zwischen den kristallinen und amorphen Teilchen, aus denen die Flugasche besteht, und den im verbrannten Brennmaterial vorkommenden mineralischen Stoff vorgeschlagen.
Comparison of fly ash properties from Afsin?Elbistan coal basin, Turkey
Journal of Hazardous Materials, 2005
Afsin-Elbistan (AE) coal fly ashes obtained by burning coal samples from top, middle and bottom sections of the AE coal seam were characterized and their properties were compared. Chemical analysis of the AE coal fly ashes showed that they are mainly composed of CaO, SiO 2 , Fe 2 O 3 and Al 2 O 3. Quantitative X-ray diffraction (XRD) analyses were carried out using an interactive data processing system (SIROQUANT TM) based on Rietveld interpretation methods. Lime is found in all the samples, ranging from around 7% to just over 38%. Amorphous contents of fly ashes are ranged between 19% and 25%. Different types of AE fly ashes revealed that bottom section coal fly ash is very similar to Class F, while medium and top section coal fly ashes are close to Class C and they might be used as mineral admixture in concrete. But also they do not comply with any of the standard. The results presented here show new possibilities for AE coal fly ashes in a wide range of fields, resulting in great advantages in waste minimization, as well as, resources conservation.
Mining and Metallurgy Engineering Bor, 2013
Nowadays, there is an increasing tendency that fly ash from thermal power plants is not only considered as a waste material that is a burden, but as an important secondary raw material that can be useful applied in various branches of economy. Therefore, this paper gives a description of the main characteristics of fly ash, as well as its chemical, mineralogical composition and morphological composition. Depending on those factors, the possibility of fly ash usage depends. In addition, the paper presents some standard norms prescribed by the national and international standards, which relate to the quality of fly ash in terms of its chemical composition.
Mineralogy and Geochemistry of Greek and Chinese Coal Fly Ash: Research for Potential Applications
China is one of the main coal-burning countries, while in Greece lignite has a share of 75% in the electricity production. The production of fly ash in China was around 160 million tonnes in 2002 while in Greece lignite fly ash accounts around 10 Mt. The variation of the Greek fly ash' chemical composition, from Ca-poor to Ca-rich fly ash, has resulted to applications such as dam construction, use in cement and possibly in concrete and road construction. On the other side Chinese fly ash, which is rich in mullite, is broadly applied for brick making.
Relation between silico-aluminous fly ash and its coal of origin
Particuology, 2008
Fly ashes are typical complex solids which incorporate at the same time intrinsic properties derived from the layers (various mineralogical and dimensional spectra) and major transformations generated during prior processing. To use fly ashes in various applications, it is necessary to characterise them completely. The first research to date carried out on silico-aluminous fly ashes in order to characterise them physically, morphologically, chemically and mineralogically, resulted in the recognition that they are relatively simple materials. In the present study, a silicoaluminous fly ash coming from the power station of Albi (France) was selected. Heat treatment at 450 and 1200 • C together with coal simulated the treatment undergone by coal in the power station in order to mimic real coal residue. In conclusion, the diversity of the particles contained in fly ash could only be explained by the relation existing between the fly ash and its coal of origin.
PHYSICAL, CHEMICAL & MINERALOGICAL PROPERTIES OF FLY ASH
nuklearmalaysia.org
Fly ash is the finely divided mineral residue resulting from the combustion of coal in electric generating plants. Fly ash consists of inorganic, incombustible matter present in the coal that has been fused during combustion into a glassy, amorphous structure. Fly ash particles are generally spherical in shape and range in size from 2 μm to 10 μm. They consist mostly of silicon dioxide (SiO 2 ), aluminium oxide (Al 2 O 3 ) and iron oxide (Fe 2 O 3 ). Fly ash like soil contains trace concentrations of the following heavy metals : nickel, vanadium, cadmium, barium, chromium, copper, molybdenum, zinc and lead. The chemical compositions of the sample have been examined and the fly ash are of ASTM C618 Class F.
Preparation and characterization of carbon-enriched coal fly ash
Journal of Environmental Management, 2008
Carbon-enriched fractions have been obtained from two coal fly ash (FA) samples. The FA came from two pulverized-coal fired power stations (Lada and Escucha, Spain) and were collected from baghouse filters. Sieving was used to obtain carbon-enriched fractions, which were further subjected to two beneficiation processes: acid demineralization using HCl and HF, and oil agglomeration using soya oil-water. Yield in weight after sieving, unburned carbon content, and several physicochemical characteristics of the obtained fractions were used to compare the performance of the beneficiation methods. Low carbon concentration was obtained by sieving, particularly in the case of Escucha FA. However, after acid demineralization or oil agglomeration, fractions containing unburned carbon in a range of 63 to 68% were obtained. These fractions showed differences in mineral phase composition and distribution depending on the FA and on the beneficiation method used. The textural properties of the obtained fractions varied as a function of their carbon content and the beneficiation method used. However, no significant differences in morphology of the carbonaceous particles were found.