Evaluation of Coal Quality: A Case Study of Ankpa Coal, Mamu Formation Anambra Basin, South-Eastern Nigeria

Abstract

Coal, being an economic deposit, can be used for various purposes depending on their properties and composition. Hence, the need to carry out a detailed investigation on Ankpa coals. Ankpa coals fall within the Mamu Formation of Anambra Basin in south-eastern Nigeria. The coals were investigated to deduce the rank and the coal quality with respect to power generation, cokability, handling, fueling, combustion, agglomeration, and slagging potential. Nine coal samples were collected from two boreholes (BH-2) and (BH-4) having depths of 16.5 and 27.4 m, respectively, and were subjected to proximate, ultimate, and elemental analyses. Moisture content ranges from 2.10 to 8.75 wt%, ash content, 4.45–26.8 wt%, volatile matter, 40.10–56.9 wt%, and the fixed carbon 20.45–39.24 wt%. The moderate moisture, low to high ash content, and high volatiles matter in the coals suggest high volatile sub-bituminous, non-coking coal. The carbon content range from 23.3 to 52.4%, hydrogen 1.73–6.88%, oxygen 9.57–18.9%, nitrogen 1.42–2.93%, and sulphur 0.73–4.15%. The sulphur content (>0.8%) and nitrogen content (>1.5%) indicate non-coking coal and it would pollute the atmosphere during combustion by releasing flue gases. The agglomeration and slagging were deduced by the ratio of C/H, FC/V, SiO₂/Al₂O_3, Fe₂O₃/CaO, silica ratio (G), and base/acid ratio (B/A). The agglomeration level and tendency of the coals to slag varies from weak to strong. The coals are not suitable for coking, but can be used for power generation, combustion applications, and fuelling due to its high combustibility.