FLASH CALCINATION OF A MAGNESITE ORE IN A FREE-FALL REACTOR AND LEACHING OF MAGNESIA

Flash calcination of a magnesite ore in a free-fall reactor and leachi ng of calcined magnesite with aqueous carbon dioxide were investigated . The effect of temperature and particle size on the weight loss were observed in the calcination experiments. The maximum weight loss was o btained as 43.2% for the particles of -100+140 mesh at the calcination temperature of 850 degrees C. In leaching experiments; leaching tempe rature and time, particle size, stirring speed, and solid/liquid ratio were selected as variables. The dissolution fraction of magnesium inc reases with the increase in the leaching time, temperature and to a le sser degree stirring speed. The dissolution also increases with decrea sing solid/liquid ratio and particle size. A thermal gravimetric metho d was used to measure activation energy, preexponential factor and rat e constants for the thermal decompositon of the magnesite ore. The act ivation energy and preexponential factor were calculated as 39.4 kcal mol(-1) and 3.5 X 10(6) s(-1), respectively. The rate constants were f ound to vary between 1.2 x 10(4) and 1.3 X 10(-2) s(-1) in the tempera ture range of 823 to 1023 K.