Innovation Series: Advanced Science (ISSN 2938-9933, CNKI Indexed)

Study on the Migration Patterns of Mercury and Arsenic in Coal During the Coal Preparation Process

Guangpin Xia¹, Pinghong Li¹, Jian Gu¹, Jun Wang^1, Yonghua Ji^{1, *}, Bingke Qin²

¹ School of Mining and Mechanical Engineering, Liupanshui Normal University, Liupanshui 553004, Guizhou, China

² School of Chemistry and Materials Engineering, Liupanshui Normal University, Liupanshui 553004, China

Corresponding Author: Yonghua Ji

Abstract: Float-sink tests were conducted on raw coal from Naluozhai, Liupanshui, to separate the coal into different density fractions, yielding three products: clean coal, middlings, and gangue. Proximate analysis was performed using an automatic industrial analyzer to determine moisture, ash, volatile matter, and fixed carbon content. Total sulfur content was measured with a computerized total sulfur analyzer. XRD and XRF were employed to characterize the mineralogical and elemental composition of the raw coal, respectively. An automatic mercury analyzer and an atomic fluorescence spectrophotometer were used to quantify the concentrations of As and Hg and investigate their enrichment and migration characteristics. The results indicated that Naluozhai coal is classified as low-to-medium ash, medium sulfur, medium mercury, and low arsenic coal. Its primary chemical components are Fe₂O₃, SiO₂, and Al₂O₃, with quartz, kaolinite, and pyrite as the main minerals. Both mercury and arsenic in the raw coal exhibited moderate enrichment. After separation, mercury in the clean coal showed slight enrichment, while arsenic showed no significant enrichment. Mercury in the middlings remained moderately enriched, and arsenic showed slight enrichment. In contrast, both mercury and arsenic were significantly enriched in the gangue. The float-sink test results demonstrated that the majority of mercury and arsenic migrated to high-density products, particularly the gangue, while their concentrations were significantly reduced in the clean coal. This indicates that coal preparation is a cost-effective and efficient pre-removal method for mercury and arsenic.

Keywords: Coal; Harmful elements; Migration patterns; Mercury and arsenic

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