Acid Generating Potential of Coals from Benue Trough, Nigeria

T. M. Adene
University of Ibadan, Ibadan, Nigeria

Much attention has been focused in recent years on coal as an alternative source of energy. Currently, exploration and exploitation of coal particularly in the Benue Trough have been intensified with a bid to diversifying the economy which has been almost solely dependent on oil and gas. In assessing the quality of coal, it is always essential to study the acid generating potential, and these have been undertaken on some selected coal samples from outcrop, boreholes and mines within the Benue Trough of Nigeria. This is to rank some of the coals occurring within the trough into acid producing and stable non-acid producing rocks. Coal ash samples were also analyzed for reactive sulphur contents and their base potential as well as degree of weathering quantified by the chemical index of alteration (CIA). The results indicate that the main acid producing rocks in the, Benue Trough are the coal rocks of the lower (LBC) and middle (MBC) Benue Trough, while the main alkaline producing rocks are the coals of the upper (UBC) Benue Trough. The coal ash has the potential to be a problematic acid generator with high CIA values ranging between 64.9 to 97.5%, low proportion of base neutralizing cations (CNK) in an A-CNK-FM ternary plot with values ranging between 2 to 19% and high reactive sulphur content of greater than 3.4kg/tonne. The information obtained from this study could be utilized in the management of existing and potential coalmines for control and treatment of acid mine drainage in the Benue Trough. It could also assist with local, regional and international energy resource evaluation, environmental and health assessment.