The physical structure and chemical and mineralogical composition of Mazidagı (Turkey) phosphate rock have been investigated by using chemical analysis, X-ray powder diffraction, scanning electron microscopy (SEM), thermal analysis, mercury porosimetry, and BET surface area methods. The results of X-ray powder diffraction analysis showed that the major minerals of the rock are calcite, fluorapatite, and carbonate fluorapatite. It was also found that the phosphate rock consists of two different phases which are dispersed in the rock heterogeneously in the SEM photographs, namely, a dark gray calcite-rich phase and a light gray phosphorusrich phase. Qualitative analysis based on the SEM photograph revealed that fluorapatite and carbonate fluorapatite were only concentrated in the phosphorus-rich phase. Calcite having particle sizes smaller than approximately 2 µm were agglomerated between compact phosphorusrich phases having particle sizes between 100 and 300 µm. The rock has a large pore-size distribution with a range of 3-1000 nm. The total porosity in the rock is 18.70%, and porous parts in the rock have been generally accumulated in the calcite-rich phase. The BET surface area of the rock is 15.68 m 2 /g.

The dehydration kinetics of Şebinkarahisar (Gedehor) alunite ore in a fluidized bed was investigated. It was observed that the dehydration reaction rate increased with increasing temperature and decreasing water vapor pressure. However, the particle size and air flow rate did not have a significant influence on the dehydration rate. On the basis of these conversion−time relations, the dehydration process was assumed to be controlled by chemical reaction. By nonlinear regression analysis, the Avrami model was found to fit the kinetic data best. n ∼ 1, the high activation energy value (209 kJ mol-1), and scanning electron microscopic photographs of the calcined ore supported this control mechanism.