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The combustion kinetics of a Samena pyrite ore
(University of Dar es Salaam, 1994) Nyamusika, Stanslaus Simon Manyori
The thermo gravimetric experimental data on the direct oxidation of the Samena pyrite ore have been analysed by use of the sharp—interface, shrinking core model of behaviour. Two stages were discerned. The initial stage involved the crackling of the reactant solid and was controlled by diffusion into the unreacted solid with the activation energy of 4.8 kcal/ gmol. As the internal structure opened up, the participation of the chemical reaction mechanism increased with time resulting into a mixed control regime dominated by intrapellet diffusion, with the activation energy of 20.6 kcal/gmol. The errors inherent in the classical sharp—interface, shrinking core theory in the calculation of activation energies based on initial rates have been demonstrated in this work where initial rates of reactions have been shown not to be necessarily chemical reaction controlled. Chemical analysis suggested that the ore mainly consists of Fe '19 00 and S 39. by weight, other elements being present in minor quantities. The FeS2 has been estimated at 69% by weight. Most of the iron, as revealed by the Moessbaur effect analysis is present in the form of FeS2. A quick estimate of the air supply requirements to a fixed bed reactor of known dimensions and load has been illustrated from the present experimental data.