EVALUATION OF THE REACTIVITY OF SOUTH BRAZILIAN LIMESTONES IN RELATION PURE SO2 THROUGH THERMOANALYSIS AND SCANNING ELECTRON-MICROSCOPY

The reactivity of some South Brazilian limestones in relation to pure SO2 was evaluated by thermogravimetric analysis carried out in a fixed bed differential reactor. After the calcination of the samples in a nitrogen atmosphere under non-isothermal conditions, the resulting lime was submitted to a reactivity test in a pure SO2 atmosphere with a constant temperature of 850 degrees C. The correlation between the surface area of the calcines and the observation of microphotographs obtained with the aid of scanning electron microscopy evidenced that the reactivity of the calcined material is directly related to the kind of pore structure developed during the calcination process: The presence of wide-open pores on the structure of the calcined material aids the penetration of SO2 into the interior of the grain, diminishing the resistance to gas diffusion and, consequently, increasing conversion.