Abstract:

In order to provide theoretical guidance for the development and utilization of Tibet Kamado microcrystalline magnesite，the thermal decomposition characteristics of Tibet microcrystalline magnesite with particle size ≤0.5 mm were studied by thermogravimetric（TG） curve under different heating rates and the thermodynamic calculation was carried out.At the same time，according to the thermogravimetric test data of microcrystalline magnesite，the activation energy of thermal decomposition of Tibet microcrystalline magnesite at different heating rates was calculated by non-isothermal thermogravimetric analysis（FWO method and KAS method）.Finally，the micromorphology of magnesium oxide，the decomposition product of Tibet microcrystalline magnesite was analyzed.The results of decomposition thermodynamics showed that with the increase of heating rate（from 2 ℃/min to 10 ℃/min），the heat required for the decomposition of the microcrystalline magnesite was increased gradually（from 187.93 kJ/mol to 207.08 kJ/mol）.The results of reaction kinetics showed that the activation energies of the microcrystalline magnesite calculated by the FWO method and the KAS method were similar.When the decomposition rate was ≤ 30%，the activation energy of thermal decomposition was decreased sharply with the increase of decomposition rate.When the decomposition rate was >30%，the activation energy of thermal decomposition was decreased slowly with the increase of decomposition rate and gradually became gentle.The microscopic morphology of microcrystalline magnesite decomposition showed that the greater the heating rate，the larger the magnesia grains of the decomposition product.

Key words: microcrystalline magnesite, thermal decomposition behavior, thermodynamics, kinetics