COMPARATIVE ANALYSES OF COMBUSTION EFFICIENCIES OF COALS FROM NIGERIA FOR POWER GENERATION

Abstract

Three coal samples from Onyeama (Enugu State), Owukpa (Benue State) and Odagbo (Kogi State) in Nigeria were collected and tested. These were characterized to determine the proximate and the ultimate analyses, calorific value and the thermogravimetric analysis, and their combustion efficiencies for power generation comparatively analyzed. The proximate analysis and the calorific value tests were done at the Energy Research Center, University of Nigeria – Nsukka, while the ultimate analysis test was conducted at the National Geosciences Research Laboratory, Kaduna. Also, the thermogravimetric analysis was carried out at the Energy Research Center, Usman Danfodio University, Sokoto. From the test results, the moisture contents ranged from 10.60 to 16.80%. The Owukpa coal sample had the highest moisture content of 16.80%, followed by Odagbo with 15.95% and Onyeama bearing 10.60%. The volatile matter contents of the samples indicated that Owukpa had the highest value of 19.95%, followed by Onyeama with 18.65% and Odagbo having the least value of 18.58% respectively. Similarly, the Owukpa coal sample had the highest fixed carbon of 55.22% followed by Onyeama with 53.36% and Odagbo with the lowest value of 50.38%, while the ash contents showed Onyeama to possess the highest value of 17.39%, and closely followed by Odagbo with 15.06% and Owukpa having the lowest content of 8.03%. Moreso, Onyeama coal sample with the highest fuel ratio of 2.86 would give the best ease of ignition and fuel burnout followed by Owukpa (2.77), and Odagbo (2.71). The percentages of the elemental carbon of Onyeama, Owukpa and Odagbo coal samples were 52.2170, 53.8178 and 50.8754% respectively, while the hydrogen contents indicated Onyeama (4.7236%), Owukpa (4.0141%) and Odagbo (3.8163%). The nitrogen, sulphur and oxygen contents obtained revealed Onyeama (1.3756, 0.10 and 13.6938%), Owukpa (1.4350, 0.10 and 15.9031%) and Odagbo (1.4260, 0.92 and 12.8423%) respectively. Consequently, the Onyeama coal sample had the highest heating value of 32.916MJ/kg, followed by Odagbo (32.037MJ/kg) and Owukpa (30.062MJ/kg). Based on the comparative analyses, the Onyeama coal indicated the overall best fuel sample followed by Owukpa and then Odagbo in that order in-view of their fuel ratio, combustion efficiencies, quality of the fuel, ease of ignition and fuel burnout.