A review of rare earth elements and yttrium in coal ash: Content, modes of occurrences, combustion behavior, and extraction methods

Fu, Bojie; Hower, James C.; Zhang, Wencai; Luo, Guangqian; Hu, Hongyun; Yao, Hong

doi:10.1016/j.pecs.2021.100954

Cited by 89 publications

(60 citation statements)

References 301 publications

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“…The REE contents in the coal ashes are in the range of 159.9-266.6 ppm, 8 to 30 times more than the feed coals, with a global CV of 13.10% (Table S2). Still, the average REE content, 211 ppm, is low compared to the averages reported for coal ashes from China (473 ppm), the United States (460 ppm), Europe (279 ppm), and others (298 ppm) [41], as well as the references therein. The ashes present H-type enrichment (La N /Lu N < 1), positive anomalies of Y, Eu, and Gd, and negative anomalies of Ce (Table S2).…”

Section: Geochemical Associationsmentioning

confidence: 71%

“…The normalization to the upper continental crust (UCC), besides being needed to eliminate the Oddo-Harkins effect (zig-zag shape), can provide information about the enrichment patterns and anomalies of individual elements that can be used to assess the REE differentiation during coal combustion [18,23,41,75]. Furthermore, it can provide information about the analysis quality.…”

Section: Ree Classification Patterns and Anomaliesmentioning

confidence: 99%

“…The increase in LREE/HREE ratio across the ESP rows was previously reported for a power plant burning high-S coals from western Kentucky [13]; however, most of the published data describe a decrease in the LREE/HREE ratio (e.g., [47,107]), as in S4 (Table S2). Although these trends are not entirely understood but the following may play major roles [41,48]: (a) the vaporization-condensation of HREEs associated with OM; and (b) higher amounts of glass in the FA from the ESP back rows. The organic association of REEs is commonly linked with low-rank coals, but it can also be found in minor amounts in high-rank bituminous coals [79].…”

Section: Geochemical Associationsmentioning

confidence: 99%

“…During coal combustion, the REEs tend to be retained on the solid residue, i.e., fly ash, bottom ash, and slag, because of their nonvolatile properties [38][39][40]. The average REE concentration in world coal combustion ashes was estimated by Fu et al [41] as 435.45 ppm (Sc not included), which is about 2.4 times higher than the concentration in UCC [32]. The distribution patterns of REEs from combustion ashes are comparable to the ashes obtained in the laboratory, which supports the nonpartitioning during combustion [17].…”

Section: Introductionmentioning

confidence: 99%

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Integrative Study Assessing Space and Time Variations with Emphasis on Rare Earth Element (REE) Distribution and Their Potential on Ashes from Commercial (Colombian) Coal

et al. 2022

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The increasing demand for rare earth elements (REEs), which is associated with their economic importance and the supply risk, has motivated the research for alternative secondary sources of these elements. Coal and coal combustion ash have been pointed out as promising REE raw materials. This research seeks to understand REE fractionation, from feed coals to ashes, considering seasonal variations, and to assess the trends within the ash fractions that can be used for further beneficiation processes. Colombian commercial feed coals, combustion ashes, and their respective fractions were sampled from a Portuguese power plant and were characterized via petrographical, mineralogical, and chemical analyses. The total REE concentrations in the feed coals studied range between 6.97 and 23.15 ppm, while, in the ashes, they vary from 159.9 to 266.6 ppm. Fly ash (FA) from electrostatic precipitator (ESP) presented higher concentrations than the bottom (BA) and economizer (ECO) ashes. Furthermore, REEs and the LREE/HREE ratio increased slightly towards the back rows of the ESP. In the feed coals, the REEs are significantly correlated with ash, and they occur in micrometric phosphate minerals intermixed with clays. In the ashes, the REEs were mostly detected in micrometric particles, with P and Al-Si as the major components. The results from the fractioned samples show that the REEs were enriched in the fine (<25 µm) and nonmagnetic fractions of the ESP FA. A single trial combining sieving and magnetic separation enabled the attainment of a REE recovery of 53%, and a final enrichment factor of 1.25. Coal combustion ashes and their respective size fractions are promising REE raw materials; however, the REE oxide concentrations are below the economical cutoff of 1000 ppm.

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Section: Geochemical Associationsmentioning

confidence: 71%

Section: Ree Classification Patterns and Anomaliesmentioning

confidence: 99%

Section: Geochemical Associationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Integrative Study Assessing Space and Time Variations with Emphasis on Rare Earth Element (REE) Distribution and Their Potential on Ashes from Commercial (Colombian) Coal

et al. 2022

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“…With the increasing shortages of critical raw materials, there are ongoing efforts worldwide aimed at obtaining them from other sources. One of these sources may be waste from energy processes such as coal combustion or gasification [9][10][11][12][13][14][15][16][17][18][19][20]. With regard to individual critical raw materials, certain features, on the basis of which we can talk about the profitability of their recovery and extraction, are determined.…”

Section: Introductionmentioning

confidence: 99%

Selected Critical Raw Materials in Waste from Coal Gasification in Poland

Bielowicz

2021

Energies

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In an effort to identify new sources of critical raw materials (CRMs) possibility of recovering selected CRMs from Polish coals, chars, and ashes resulting from the combustion of coals and chars was investigated. The samples were collected from pilot fluidized bed gasification systems. The search for CRMs in coal gasification wastes has not been widely reported before. The study used 2 bituminous coal and 1 lignite sample; the concentration of individual critical raw materials (CRMs) was analyzed using the ICP-MS method. The obtained results were compared with Clarke values in coal ash and in the Earth’s crust, and with the adopted cut-off grade. As shown by the analysis, the highest concentrations of CRMs can be found in fly ash, mainly in samples from the eastern part of the Upper Silesian Coal Basin. This applies mostly to Be, Cs, or Sb due to the fact that their concentrations were found to be higher than the Clarke value in the Earth’s crust; the mentioned fly ashes could be used as potential sources of critical elements if appropriate recovery technologies are developed. In addition, the tested materials have elevated Se, Pb, Ni concentrations, but their recovery is currently not economically viable. Compared to the currently adopted cut-off grade levels, there are no critical elements in the analyzed coal gasification waste that could be recovered.

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Intensified extraction of rare earth elements from coal fly ash

Lomanjaya

Liu

2023

J of Chemical Tech & Biotech

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BACKGROUND:The high demand for coal-based energy leads to the production of a massive amount of coal fly ash (CFA). Owing to the content of rare earth elements (REEs), CFA is regarded as one of the promising secondary sources of REEs. The corrent study utilized two intensified extraction methods, subcritical water extraction (SWE) and microwave assisted extraction (MAE), in the recovery of REEs, including yttrium (Y) and samarium (Sm), from CFA sample.RESULTS: The effects of acid concentration, temperature, and solid to liquid ratio (S/L), and reaction time on leaching efficiency were investigated. Total of 80.32% of Y and 68% of Sm were leached out using SWE at 1.0 N HCl, S/L of 5 g/L, 150 °C for 5 min. Meanwhile, MAE yielded leaching efficiency of 71.99% of Y and 54.48% of Sm at 2.0 N HCl, S/L of 2.5 g/L, 150 °C for 5 min. Both methods performed better than conventional method. CONCLUSIONS: From comparisons, SWE showed advantages of higher leaching efficiency at lower acid concentration, while MAE was more rapid and more energy efficient for REEs recovery from CFA.

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A review of rare earth elements and yttrium in coal ash: Content, modes of occurrences, combustion behavior, and extraction methods

Cited by 89 publications

References 301 publications

Integrative Study Assessing Space and Time Variations with Emphasis on Rare Earth Element (REE) Distribution and Their Potential on Ashes from Commercial (Colombian) Coal

Integrative Study Assessing Space and Time Variations with Emphasis on Rare Earth Element (REE) Distribution and Their Potential on Ashes from Commercial (Colombian) Coal

Selected Critical Raw Materials in Waste from Coal Gasification in Poland

Intensified extraction of rare earth elements from coal fly ash

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