Eocene-Oligocene Stratigraphy and Industrial Potentials of Lignite Deposits in Anambra State, Nigeria

Abstract

The stratigraphy and geochemistry of the Eocene-Oligocene Ogwashi-Asaba Formation were studied to assess the industrial potentials of its lignite deposits in Anambra State, Nigeria. Methodology involved fieldwork and laboratory analysis. The analyses included proximate, ultimate and X-ray diffraction studies. Five lignitic seams were observed at different stratigraphic levels of the formation. Seam 1 is the lowest seam and includes lignites from Akpuchara and Ekulo streams at Oba, Enem, Ejighioku and Oruru streams at Oraifite, Obiakoloma, Amaiyi and Eze streams at Nnewi. The average moisture, dry ash, volatile matter and fixed carbon contents for seam 1 are respectively 17.20%, 25.64%, 31.84% and 25.12%. The average Carbon (C), Hydrogen (H), Nitrogen (N), Oxygen (O) and Sulphur (S) contents for seam 1 are respectively 35.91%, 2.99%, 1.51%, 9.10% and 0.12%. The calorific value of seam 1 ranges from 582.23 kcal/kg to 4583.79 kcal/kg (2.44-19.19 MJ/kg) with an average value of 3209.13 kcal/kg (9.77 MJ/Kg). Seam 2, 3, 4, 5 are lignites from Oduga stream, Anthill section, Ofala stream and Nneoru stream respectively. The moisture, dry ash, volatile matter and fixed carbon contents for seam 2 are respectively 6.10-11.40%, 63.40-67.60%, 15-19.70% and 6.6-9.83%. The C, H, N, O and S contents for seam 2 are 5.50%, 3.91%, 1.44%, 13.84% and 0.75%. The calorific value of seam 2 is between 1.281.55 and 1322.42 kcal/kg (5.37-5.54 MJ/Kg). Seam 3,4,5 are very thin lignite beds of less economic importance even though their calorific values vary between 984 kcal/kg and 3082.92 kcal/kg (4.12-12.91MJ/Kg). The lignites from the Eocene-Oligocene Ogwashi-Asaba Formation have potentials for use in thermal power generation, household and other industrial uses.