3.8 Article

Thermal decomposition behaviour and kinetics of Xinjiang siderite ore

Publisher

TAYLOR & FRANCIS AS
DOI: 10.1080/03719553.2015.1118213

Keywords

Siderite ore; Thermal decomposition; Thermodynamics; Kinetics; Phase transformation process; Activation energy

Funding

  1. National Natural Science Foundation of China [51574281]

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In order to provide a better theoretical foundation for utilisation of Xinjiang siderite resources in China, its thermal decomposition behaviour was studied in neutral and oxidising atmospheres by employing thermodynamics analysis, chemical titration, thermogravimetric, and X-ray diffraction means. Isothermal experiments were conducted to investigate the thermal decomposition kinetics of siderite lump in a weakly oxidising atmosphere at 500-850 degrees C. The results reveal that siderite has self-magnetisation characteristics under controlled conditions, and the phase evolution process and final products of decomposition depend temperature and atmosphere. The phase transformation process in weak oxidising atmosphere follows the steps as: FeCO3 -> Fe3O4 -> gamma-Fe2O3 at 550 degrees C, and FeCO3 -> FeO + Fe3O4 -> Fe3O4 -> gamma-Fe2O3. alpha-Fe2O3 at 800 degrees C. In inert atmosphere, the decomposition pathway is FeCO3 -> Fe3O4 below 733 degrees C and FeCO3. FeO + Fe3O4 above 733 degrees C. The molar ratio of FeO/Fe3O4 increases with temperature. The decomposition kinetics of siderite lump in oxygen-deficient atmosphere is consistent with chemical reaction control in the temperature range 500-700 degrees C and nucleation and growth mechanism in the 750-850 degrees C. The corresponding activation energies are 53 . 73 and 38 . 15 KJ mol(-1), respectively.

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