THERMOGRAVIMETRIC ANALYSIS OF ENUGU COAL UNDER INERT AND OXIDATIVE ATMOSPHERES

Abstract

The thermal degradation and kinetics of Enugu coal have been evaluated under inert and air atmospheres using non-isothermal thermogravimetry analysis (TGA). The devolatilization characteristics of coal pyrolysis and combustion (ignition and peak temperature) were evaluated. Coats-Redfern method was applied to determine the apparent activation energy (Eα) of the thermal decomposition of process. The main devolatilization stage of coal pyrolysis takes place in two steps between a temperature of 180-568 oC during which volatile matter was released. On the other hand, the devolatilization stage of coal combustion was characterized by only one single step occurring between a temperature of 370-640 oC where volatiles were released and burned. The peak pyrolysis temperature was 31 oC higher than 420 oC obtained for the combustion process. The result of residual weight of coal at the end of completion of combustion was 11.5 wt% of the initial weight. This quantity is appreciably lower than 78.5 wt% of the initial weights of 100 wt% under inert atmosphere. The mean activation energy of the pyrolysis of the coal was 73.71 kJ mol-1 as against 97.75 kJ mol-1 for coal combustion. The result obtained can be effectively employed in design and optimization of coal combustion furnace.