CHARACTERISATION OF SOME NIGERIAN COALS FOR POWER GENERATION

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Author

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Department of Engineering

ABSTRACT
Five coal samples from Odagbo (Kogi State), Owukpa (Benue State), Ezimo (Enugu State), Amansiodo (Enugu State) and Inyi (Enugu State) weresubjected to proximate analysis, ultimate analysis, calorific value determination, petrographic and thermogravimetric analysis to determine their suitability for power generation. Tests were carried out at the laboratories of Advanced Coal Technology, South Africa (now Bureau Veritas Testing and Inspections South Africa, BV-TISA) and the Institute of Applied Materials of the University of Pretoria. Based on analysis of results of tests carried out, Amansiodo coal is a bituminous, low sulphur and medium ash coal; while Owukpa coal is a sub-bituminous A, low sulphur, low ash coal rich in huminites. In addition, Odagbo coal is a sub-bituminous B, medium sulphur, low ash coal rich in huminites; Ezimo coal is a sub-bituminous C, low sulphur, high ash coal; while Inyi coal is a sub-bituminous C, low sulphur, high ash coal.Between Odagbo and Owukpa sub-bituminous coals, Owukpa has a lower ignition temperature (283.63oC) due to its higher volatile matter content (39.1%). However, Ezimo sub-bituminous coal, which has a lower volatile matter (31.1%) unexpectedly has the same ignition temperature as Owukpa (283.63oC) due to its higher liptinite content (7.2%) when compared with that of Owukpa (2.9%). The five (5) coal samples analysed can be used for power generation using circulating fluidised bed combustion (CFBC) technology due to its tolerance of a widevariety of coals and particle sizes. Amansiodo coal is suitable for power generation using pulverised coal combustion technology based on comparison of its gross calorific value (27.48MJ/kg), ash content (8.6%), inherent moisture content (5.4%), sulphur content (0.92%), etc with requirements published by coal-fired power plant operators. Gross calorific values, inherent moisture and contents of Odagbo, Owukpa, Ezimo and Inyi sub-bituminous coals make them largely suitable for pulverized coal combustion when vi compared with the coal fuel used for the Genessee Phase 3 power station in Canada. The ease of combustion of the coal samples in decreasing order is Odagbo, Owukpa, Inyi, Ezimo and Amansiodo. The ignition temperatures of the coals increase with decreasing volatile matter content, their calorific values are strongly correlated with the fixed carbon, elemental carbon, volatile matter and hydrogen contents in decreasing order.