The Physicochemical Characterization of a Newly Explored Thar Coal Resource

Abstract

The samples of Thar coalfield were characterized using a thermogravimetric analyzer, atomic absorption spectrophotometer, X-ray diffractometer, Fourier transform infrared spectra, and scanning electron microscopy-energy dispersive x-ray spectroscopy analysis. The samples were ranked as lignite and subbituminous according to American Society for Testing and Materials standard classification. Differential thermogravimetric analysis results specified chemical reactivity of coal at the primary devolatilization region (257–412°C) and secondary devolatilization region (741–900°C). The minerals identified were quartz, kaolinite, dikite, halloysite, gold copper indium, graphite hydrogen nitrate, and magnesium vanadium molybdenum oxide. X-ray diffraction study confirmed the presence of mineral constituents as indicated by microscopic investigation. Fourier transform infrared spectra identified C=C aromatic groups at 1,500–1,700 cm⁻¹ as maturity indicator and 2,800–3,000 cm⁻¹ and 2,300 cm⁻¹ as aliphatic stretching regions. The peaks of quartz and kaolinite were observed at 900–1,100 cm⁻¹. Strong correlations between mineral matter-SiO₂ (r ² = 0.808) and Al₂O₃-SiO₂ (r ² = 0.957) indicates Al and Si as the dominant inorganic components. Cluster analysis appeared as an additional tool for coal ranking based on their physicochemical properties.

Keywords:

• atomic absorption spectrophotometer
• coal characterization
• proximate analysis
• thermogravimetric analyzer
• X-ray diffractometer

Notes

^a ar basis: as-received basis; daf basis: dry, ash-free basis; m,mmf basis: moist, mineral-matter-free basis.