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Minerals 2016, 6(2), 27; doi:10.3390/min6020027

Minerals in the Ash and Slag from Oxygen-Enriched Underground Coal Gasification

School of Chemistry and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
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Academic Editor: Thomas N. Kerestedjian
Received: 30 October 2015 / Revised: 19 January 2016 / Accepted: 21 January 2016 / Published: 30 March 2016
(This article belongs to the Special Issue Minerals in Coal)
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Abstract

Underground coal gasification (UCG) is a promising option for the recovery of low-rank and inaccessible coal resources. Detailed mineralogical information is essential to understand underground reaction conditions far from the surface and optimize the operation parameters during the UCG process. It is also significant in identifying the environmental effects of UCG residue. In this paper, with regard to the underground gasification of lignite, UCG slag was prepared through simulation tests of oxygen-enriched gasification under different atmospheric conditions, and the minerals were identified by X-Ray diffraction (XRD) and a scanning electron microscope coupled to an energy-dispersive spectrometer (SEM-EDS). Thermodynamic calculations performed using FactSage 6.4 were used to help to understand the transformation of minerals. The results indicate that an increased oxygen concentration is beneficial to the reformation of mineral crystal after ash fusion and the resulting crystal structures of minerals also tend to be more orderly. The dominant minerals in 60%-O2 and 80%-O2 UCG slag include anorthite, pyroxene, and gehlenite, while amorphous substances almost disappear. In addition, with increasing oxygen content, mullite might react with the calcium oxide existed in the slag to generate anorthite, which could then serve as a calcium source for the formation of gehlenite. In 80%-O2 UCG slag, the iron-bearing mineral is transformed from sekaninaite to pyroxene. View Full-Text
Keywords: underground coal gasification; coal ash; mineralogy; oxygen-enriched gasification underground coal gasification; coal ash; mineralogy; oxygen-enriched gasification
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Liu, S.; Qi, C.; Zhang, S.; Deng, Y. Minerals in the Ash and Slag from Oxygen-Enriched Underground Coal Gasification. Minerals 2016, 6, 27.

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