Size-dependent variations in fly ash trace element chemistry: Examples from a Kentucky power plant and with emphasis on rare earth elements

Jingjing Liu, Shifeng Dai, Xin He, James C. Hower, Tanaporn Sakulpitakphon

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

Rare earth elements while not considered to be volatile in coal combustion do show some variation between ash collection rows. To better understand this variation, we investigate the trace element variations (with emphasis on rare earth elements) in size fractions of fly ash from multiple ash collection rows at a single power-generating unit at a southeastern Kentucky power plant. Fly ash samples were investigated using optical microscopy, X-ray fluorescence, and inductively coupled plasma mass spectrometry. The arsenic concentration increases from the hottest to the coolest ends of the ash collection system. The relationship between Hg capture and the flue gas temperature is illustrated by the increase in Hg between the economizer hopper and the cooler mechanical hopper. Although the rare earth elements do not show significant variation between rows of ash collection systems, the ratio of light and heavy rare earth elements (LREE/HREE) decreases from the economizer and mechanical rows to the electrostatic precipitator row. Petrographic differences between the ash sizes may also contribute to the LREE/HREE distributions. The glass fraction that appears somewhat uniform using optical microscopy contains rare-earthelement-bearing minerals, accounting for at least some of the rare earth elements seen in the "glass". The positive Eu anomalies in the ashes could possibly be due to the coal combustion conditions rather than inherited from raw coals, and the rare earth element composition in feed coal is probably responsible for the medium rare earth element enrichment type in different size fractions of fly ash.

Original languageEnglish
Pages (from-to)438-447
Number of pages10
JournalEnergy and Fuels
Volume31
Issue number1
DOIs
StatePublished - Jan 19 2017

Bibliographical note

Publisher Copyright:
© 2016 American Chemical Society.

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology

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