Mineralogy, physicochemical and oxidative thermal analyses of Cretaceous coals from the Benue Trough, Nigeria

Abstract

The erratic supply of electricity in Nigeria has renewed interest in the utilisation of coal for energy self-sufficiency and diversification of the national energy mix. In this study, selected coal samples from three regions of the Benue Trough Basin were examined through pore water chemistry, X-ray diffraction (XRD), and thermosgravimetric analysis (TGA). The low pH observed for the Lower Benue Trough (LBT) coals indicates the release of sulphur and acids during oxidation. Mineralogical analyses reveal quartz, kaolinite, montmorillonite, albite, pyrite, gypsum and sodium chlorate in the coal samples. The genetic kaolinite species identified in Imeagha (IMG) coal are detrital kaolinite and the highly crystalline neomorphic kaolinite. Gypsum and jarosite minerals occurred in minor quantities in Garin Maiganga (GMG), whereas significant amount of pyrite was detected in Enugu (ENG) coal. Oxidative thermal degradation resulted in the residual mass (RM) ranging between 4.35% and 56.96%) and mass losses (ML) between 43.04% and 95.65%) due to the drying, devolatilization, and coke formation in the samples. The most reactive coal examined was GMG coal, whereas the least reactive was IMG coal. Lamja (LMZ), GMG, and OKB coals are suited for electricity generation, whereas ENG and IMG coals can be utilised for cement production.

Keywords

• Benue trough
• Cretaceous coal
• Mineralogy
• Physicochemical analysis
• Thermogravimetry