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Transformation of Mg-bearing minerals and its effect on slagging during the high-alkali coal combustion

Year: 2024
Type: article
Abstract: To better understand the mineralogical, release-transformation patterns and ash deposition of Mg-bearing minerals, Wucaiwan Coal (WCW), Meihuajing Coal (MHJ), and slag of water wall from a power plant were collected, the density separation experiments and high-temperature ash evolution experiments were conducted. XRF, XRD, and SEM-EDS were used to analyze the mineralogy, chemical composition, and slag characteristics. The results show that Mg and Ca in high-alkali coal are highly homologous, mainly in heavy minerals and carbonate, followed by silicate, with the least spinel form. During combustion, the release of Mg is affected by its occurrence form. At the same time, Ca has a competitive and synergistic effect on the transformation of Mg-bearing minerals, which depends on the relative content of Si in ash. Mg-bearing minerals gradually transform into thermally stable minerals, with the transformation pathway being magnesium calcite → Mg-bearing silicate (diopside, akermanite, bredigite) → hedenbergite/spinel. Spinel is identified as the primary Mg-bearing mineral in high-temperature ash, suggesting that Mg2+, Al3+, and Fe3+ are more prone to forming stable Mg-bearing minerals, with Al3+ capable of mutual substitution with Fe3+. In coal combustion, the formation of Mg-Al-Fe and Mg-Al-Fe-Si-Ca eutectic systems causes slagging on the water wall and worsens water wall corrosion.
DOI: 10.1016/j.fuproc.2024.108166
Language: English
Open Access status: gold
Estimated APC paid: $3,000
OpenAlex ID: W4404870882
FWCI: 2.192
Cites: 48
Cited by: 10
Related to: 10