Characteristics of ferrospheres in fly ashes derived from Bokaro and Jharia (Jharkand, India) coals

Valentim, Bruno; Shreya, Neha; Paul, Biswajit; Gomes, Celeste Santos; Sant'Ovaia, Helena; Guedes, Alexandra; Ribeiro, Joana; Flores, Deolinda; Pinho, Sílvia C.; Suárez‐Ruíz, Isabel; Ward, Colin R.

doi:10.1016/j.coal.2015.11.013

Cited by 32 publications

(37 citation statements)

References 66 publications

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“…The reacted feldspars could also suggest that feldspars in the studied combustion residues decomposed during combustion; hence, feldspars may have derived through reactions between Ca, K, and Na and aluminosilicate glass (Querol et al, 1994;Vassilev et al, 2003;Silva et al, 2014). In addition, the FeCa-rich composition of glass could indicate that liberated Fe and Ca from decomposition of nonsilicate minerals during combustion could take place in the formation of glass in the studied FA and BA samples (Sokol et al, 2002;Dai et al, 2014;Valentim et al, 2016).…”

Section: Mineralogical Compositionmentioning

confidence: 98%

“…Pyrites in the FC were decomposed during combustion and converted to Fe-oxides and pyrrhotite or other FeS phases (Huffman et al, 1989;McLennan et al, 2000). If these phases do not come in contact with aluminosilicate glass, Fe-rich glass could form during combustion (Sokol et al, 2002;Valentim et al, 2016). In the studied samples, both Fe-oxides and Fe-rich glass were identified in combustion residues through the SEM-EDX examination (Figures 5a-5d and 6a-6d); hematite is abundant in FA and BA samples (Table 2).…”

Section: Mineralogical Compositionmentioning

confidence: 99%

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Mineralogy and geochemistry of feed coals and combustion residues of the Kangal power plant (Sivas, Turkey)

Karayi̇ǧi̇t¹,

Oskay²,

Gayer³

2019

Turkish J Earth Sci

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This study focuses on mineralogical and geochemical compositions of feed coal (FC) and combustion residues, namely fly ash (FA) and bottom ash (BA) samples, obtained from the Kangal coal-fired power plant in central Turkey. The X-ray powder diffraction data indicate that carbonate and clay minerals are dominant phases in the FC samples. In the FA samples, quartz, hematite, anhydrite, lime, and feldspar are generally dominant and abundant phases, whereas calcite, ettringite, and portlandite are generally more abundant in the BA samples. The elements Mo, Cs, and U are significantly enriched in the studied FC, FA, and BA samples. The statistical analysis and SEM-EDX data show that Ca, Ti, and the vast majority of trace elements are inorganically affiliated, and only Tl and U have probable organic affinity in the FC. In addition, the redox conditions in the paleomires presumably resulting in Mo and U enrichment in FC, whereas their enrichment in FA and BA is most likely related to retention by CaO and Ca-sulfate. The Cs enrichment in FA is due to retention by glass. The elements in the FA and BA are distinguished into four groups according to their volatility during combustion. The elements As, Mo, Cd, Tl, and U (Group I) are the most volatile elements during combustion and condensation in the FA. The elements Li, Zn, Ga, Rb, Nb, Cs, Ba, La, and Pb (Group IV) did not become more volatile or less volatile during combustion and are located in BA. Nevertheless, Zn and Pb in the BA seem to be related to the presence of unaffected pyrite and sphalerite, and are due to low combustion efficiency of the boiler during the sampling period. Overall, enriched elements and minerals in FA and BA suggest that their disposal should be undertaken with caution.

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Section: Mineralogical Compositionmentioning

confidence: 98%

Section: Mineralogical Compositionmentioning

confidence: 99%

Mineralogy and geochemistry of feed coals and combustion residues of the Kangal power plant (Sivas, Turkey)

Karayi̇ǧi̇t¹,

Oskay²,

Gayer³

2019

Turkish J Earth Sci

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“…Raman spectroscopy has also been employed in the identification of a variety of minerals, including crystalline and amorphous phases [22,23]. Minerals especially the iron oxides produce strong Raman bands [24]. In addition to iron oxides, the occurrence of quartz and calcite in power plant fly ashes has also been revealed by Raman spectroscopy [25].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy

Yin

et al. 2019

Crystals

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The organic and mineral components in two coals and resulting high-temperature ashes with high silicon content were characterized by second-derivative infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The infrared spectra of raw coals show weak organic functional groups bands but strong kaolinite bands because of the relatively high silicates content. In contrast, the Raman spectra of raw coals show strong disordered carbon bands but no mineral bands since Raman spectroscopy is highly sensitive to carbonaceous phases. The overlapping bands of mineral components (e.g., calcite, feldspar, and muscovite) were successfully resolved by the method of second-derivative infrared spectroscopy. The results of infrared spectra indicate the presence of metakaolinite in coal ashes, suggesting the thermal transformation of kaolinite during ashing. Intense quartz bands were shown in both infrared and Raman spectra of coal ashes. In addition, Raman spectra of coal ashes show a very strong characteristic band of anatase (149 cm–1), although the titanium oxides content is very low. Combined use of second-derivative infrared spectroscopy and Raman spectroscopy provides valuable insight into the analyses of mineralogical composition. The XRD results generally agree with those of FTIR and Raman spectroscopic analyses.

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“…It can be seen in Table 2 that coarse products have the higher contents of Fe as compared to fine products, this identifies that Fe rich particles also known in literature as ferrospheres or magnetospheres [33] are coarser in size and are present mostly in coarse products due to which coarse products have higher percentage of Fe. It can further be seen that as the classifiers wheel speed is increased, Fe content of coarse products decreases which is primarily due to addition of more non-Fe rich finer fraction from fine products.…”

Section: Chemical Propertiesmentioning

confidence: 78%

“…9 were analysed using EDX analyses with point analyses and small area analyses for the composition of Si, Al, and Fe as they are present in high percentages among the elemental composition of separated fly ashes in Table 2. It was seen from the results of the EDX individual particle analyses that majority of particles in 8000 rpm fines and 10000 rpm fines have contents of Si > 50%, Fe < 10%, and Al > 20 %, while only very few brighter particles rich in Fe were observed which showed contents of Fe between 10 and 30% which also observed by [33] are known as ferrospheres. EDX analyses for individual particles of 8000 rpm coarse and 10000 rpm coarse products also showed contents of Si > 50%, Fe < 10%, and Al > 20 %, but a higher variation of contents were observed as compared to fine products.…”

Section: Edx Individual Particle Analysesmentioning

confidence: 92%

Dry separation of brown coal fly ash, determination of its physical, morphological, chemical, and mechanical properties of its cementitious mixes

Haider

Bittnar²,

Ali³

et al. 2017

Period. Polytech. Civil Eng.

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The dry separation of brown coal fly ash was carried out in this research using ultrafine air classifier. Classifiers wheel speed was increased from 2000 to 10000 rpm to obtain fine and coarse products. As the speed of classifier was increased diameter of particles decreased and particle morphology was observed on optical, electron microscopes which showed that at 10000 rpm classifiers wheel speed, average fine particles morphology changed from angular and rounded irregular slaggy particles to spherical particles. High volume cementitious mixes were prepared with fine and coarse products in which cement -60% fine products samples showed a considerable increase of compressive strength as compared to cementitious raw fly ash control samples.

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Characteristics of ferrospheres in fly ashes derived from Bokaro and Jharia (Jharkand, India) coals

Cited by 32 publications

References 66 publications

Mineralogy and geochemistry of feed coals and combustion residues of the Kangal power plant (Sivas, Turkey)

Mineralogy and geochemistry of feed coals and combustion residues of the Kangal power plant (Sivas, Turkey)

Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy

Dry separation of brown coal fly ash, determination of its physical, morphological, chemical, and mechanical properties of its cementitious mixes

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