Abstract
Compacts made of concentrated celestite ore (SrSO
4
, 96·5%) were reduced isothermally at 950-1100°C by solid carbon. The reduction of SrSO
4
(water insoluble) to SrS (water soluble) is an important step to produce the most common industrial reagents of strontium salts (SrCO
3
, SrNO
3
and SrCl
2
). The isothermal reduction behaviour was investigated using advanced quadrupole mass spectrometer. X-ray diffraction and SEM analysis were used to characterise the reduced samples. The influence of reduction conditions on the structural characteristics of the products was extensively studied to get clear comprehension of reduction process. It was found that celestite ore is completely reduced to SrS at a temperature above 900°C and the reduction rate increases with temperature. The experimental measurements were used to elucidate the carbothermic reduction mechanism of celestite ores. The reduction of celestite proceeded in only one step and Boudouard reaction is the rate controlling step. The calculated values of activation energy (115·3 kJ mol
−1
) revealed that solid state diffusion mechanism seems to have a role in the reduction process.