Iron in Coal and Slagging

Bryant, Glenn; Bailey, C. W.; Wu, Hongwei; Mclennan, A. R.; Stanmore, B. R.; Wall, Terry

doi:10.1007/0-306-46920-0_43

Cited by 8 publications

(5 citation statements)

References 8 publications

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“…CCSEM results (Table ) identified some included siderite to be present in Coal A and Coal B. Based on the analysis of the combustion residues for these coals by SEM and electron microprobe, Mössbauer spectroscopy, and previous work, the transformation mechanisms of included siderite are presented in Figure . These results are now discussed with reference to the mechanistic diagram.…”

Section: Resultsmentioning

confidence: 91%

Ash Formation Mechanisms during pf Combustion in Reducing Conditions

et al. 1999

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A range of pulverized coals were combusted in a laboratory drop-tube furnace at temperatures of 1573, 1723, and 1873 K under oxidizing and reducing conditions to determine the effect of combustion stoichiometry on ash formation mechanisms. As iron mineral transformations were expected to be most affected by combustion stoichiometry, two of the test coals chosen were of high pyrite (FeS2) content and two of high siderite (FeCO3) content. It was found that the ash formation mechanisms of excluded quartz, koalinite, and calcite were not affected by oxidizing or reducing combustion conditions. Excluded pyrite was found to decompose to pyrrhotite, which oxidized to produce an FeO−FeS melt phase which was stable under reducing conditions. Under oxidizing conditions oxidation continued, producing magnetite and hematite. Excluded siderite was found to decompose to wustite, which was stable under reducing conditions, but oxidized to produce magnetite under oxidizing conditions. Included pyrite and siderite were determined to behave as for excluded pyrite and siderite if there was no contact with alumino-silicates. Included pyrite that contacted alumino-silicate minerals was observed to form two-phase FeS/Fe-glass ash particles, with incorporation of iron into the glass proceeding as the FeS phase was oxidized. Included siderite that contacted alumino-silicate minerals was determined to directly form iron alumino-silicate glass ash particles. Iron alumino-silicate glass ash was determined to form with iron in the Fe2+ state, much of which subsequently transformed to the Fe3+ state in oxidizing conditions, but remained primarily as in the Fe2+ state under reducing conditions.

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Section: Resultsmentioning

confidence: 91%

Ash Formation Mechanisms during pf Combustion in Reducing Conditions

et al. 1999

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“…The ranges and averages of the elements (in µg/g, unless otherwise indicated) in the studied FA and BA samples, and their comparison with worldwide brown coal ashes (a: from Ketris and Yudovich (2009) pyrite associations, and unaffected pyrites were identified from both FA and BA samples. These assemblages could relate to either the low-efficiency of the boiler or the reduced atmospheric conditions in the sampled boilers (Spliethoff et al, 1996;Bryant et al, 1999;McLennan et al, 2000). Carbonate minerals are the dominant phases in the FC samples, and their breakdown during combustion resulted in the formation of lime (CaO) in the boiler (Filippidis et al, 1996;Vassilev and Vassileva, 1996;Fernandez-Turiel et al, 2004).…”

Section: Mineralogical Compositionmentioning

confidence: 99%

“…Additionally, pyrrhotite, Fe-oxide- pyrite associations, and unaffected pyrites were identified from both FA and BA samples. These assemblages could relate to either the low-efficiency of the boiler or the reduced atmospheric conditions in the sampled boilers (Spliethoff et al, 1996;Bryant et al, 1999;McLennan et al, 2000).…”

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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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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“…Huggins et al correlated the liquidus surfaces of the SiO 2 −Al 2 O 3 −XO (where X = Fe, Ca, and K 2 ) ternary systems with trends obtained for the AFT of coal ash. Hurst et al and Wall et al used SiO 2 −Al 2 O 3 −CaO and CaO−MgO−FeO n ternary equilibrium diagrams to predict the effect of CaO and Fe 2 O 3 on the AFT of coal ash. However, these methods could only be applied to a limited range of conditions and were only able to qualitatively predict the AFTs of coal ashes.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Chinese Coal Ash Fusion Temperatures in Ar and H₂ Atmospheres

et al. 2009

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The ash fusion temperatures (AFTs) of 21 typical Chinese coal ash samples and 60 synthetic ash samples were measured in Ar and H2 atmospheres. The computer software package FactSage was used to calculate the temperatures corresponding to different proportions of the liquid phase and predict the phase equilibria of synthetic ash samples. Empirical liquidus models were derived to correlate the AFTs under both Ar and H2 atmospheres of 60 synthetic ash samples, with their liquidus temperatures calculated by FactSage. These models were used to predict the AFTs of 21 Chinese coal ash samples in Ar and H2 atmospheres, and then the AFT differences between the atmospheres were analyzed. The results show that, for both atmospheres, there was an apparently linear correlation and good agreement between the AFTs of synthetic ash samples and the liquidus temperatures calculated by FactSage (R > 0.89, and σ < 30 °C). These models predict the AFTs of coal ash samples with a high level of accuracy (SE < 30 °C). Because the iron oxides in coal ash samples fused under a H2 atmosphere are reduced to metallic iron and lead to changes of mineral species and micromorphology, the AFTs in a H2 atmosphere are always higher than those with an Ar atmosphere.

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Iron in Coal and Slagging

Cited by 8 publications

References 8 publications

Ash Formation Mechanisms during pf Combustion in Reducing Conditions

Ash Formation Mechanisms during pf Combustion in Reducing Conditions

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

Prediction of Chinese Coal Ash Fusion Temperatures in Ar and H₂ Atmospheres

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Iron in Coal and Slagging

Cited by 8 publications

References 8 publications

Ash Formation Mechanisms during pf Combustion in Reducing Conditions

Ash Formation Mechanisms during pf Combustion in Reducing Conditions

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

Prediction of Chinese Coal Ash Fusion Temperatures in Ar and H2 Atmospheres

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Prediction of Chinese Coal Ash Fusion Temperatures in Ar and H₂ Atmospheres