Thermal decomposition characteristics of low-grade rhodochrosite ore in N2, CO2 and air atmosphere

Roasting is an essential process before ammonia leaching of low-grade rhodochrosite ore. Thermal decomposition characteristics and phase transformation rules of low-grade rhodochrosite ore with a particle size of less than 74 µm in N 2 , CO 2 and air were studied. MnCO 3 , MgCO 3 and CaCO 3 in rhodochrosite are decomposed into MnO, MgO and CaO at 339 ℃, 306 ℃ and 842 ℃, respectively. MnO is oxidized to MnO 2 , Mn 2 O 3 and Mn 3 O 4 at 339 ℃, 533 ℃ and 1005 ℃, respectively. The TG/DTA and phase transformation results indicated that by thermal decomposition of rhodochrosite ore in air, N 2 and CO 2 , MnCO 3 is converted into Mn 2 O 3 , MnO and MnO, respectively. MnCO 3 is converted to MnO at a higher temperature in a carbon dioxide atmosphere (512 ℃) than in a nitrogen atmosphere (400 ℃).