Geomineralogical, Physiochemical, Thermal and Kinetic Characterisation of Selected Coals From the Benue Trough and Anambra Basins in Nigeria

Abstract

This study examined the geomineralogical, physiochemical, thermal, and kinetic characteristics of selected coals from Chikila (CHK), Lafia Obi (LFB) and Okaba (OKB) in the Benue Trough and Anambra Basins of Nigeria. Physicochemical characterisation revealed significant quantities of carbon, volatiles, fixed carbon, and heating values (25–30 MJ/kg) but low moisture, and ash contents. The fuel properties indicate subbituminous to bituminous rank coals. The morphological, microstructure and elemental analyses revealed heterogeneous sized coal particles with a glassy sheen due to clay and aluminosilicate minerals such as quartz, alumina, kaolinite, and hematite. Based on thermal analysis, the coal samples are highly reactive and experienced significant thermal degradation as evident in the high mass losses (ML = 91.59 – 94.04%) and low residual masses (RM = 5.96% - 8.41%), which are observed in the orders LFB > OKB > CHK for ML and CHK > OKB > LFB for RM. LFB experienced the highest ML and lowest RM indicating it is more thermally reactive compared to OKB and CHK. Kinetic analysis by Coats-Redfern model revealed low values of activation energy, Ea (30.07 – 43.91) kJ/mol and frequency factor A (1.16×10-02 – 6.73×10-02) min-1 deduced at high R2 (0.98-0.99). The kinetic parameters demonstrated that the selected coal samples are highly reactive under oxidative conditions which are suited for energy recovery through pulverised coal combustion.