Characterization and Removal Potential of Fluorine in Lignite from a Mine in Shaanxi Province, China: A Case Study

Fluorine appears in coal and is released into the atmosphere upon combustion, resulting in harmful impacts on the environment and life, which needs to be removed from coal before utilization. Coal can be processed by flotation and gravity separation to reduce its fluorine content. In this study, a lignite sample from a mine in Shaanxi Province, China, was characterized using the float-sink test, sieving test, X-ray diffraction (XRD), and polarized light microscopy. Mineralogical analysis indicated that the fluorine in coal is mainly contained in Muscovite and polylithionite, and partly in pyrite. The washability and floatability analyses were employed to evaluate the extent of fluorine removal from >0.5 and <0.5 mm size fractions of lignite, respectively. Compared to the raw sample that contained 347.74 mu g/g fluorine content, the proposed combination of gravity-flotation separation process decreased the fluorine content to 90.14 mu g/g, which meets the requisites of coal standards.