Thermodynamic conditions of reactions between high-carbon ferromanganese powders and gas decarbonizers like O2, CO2 and water vapor were studied by thermodynamic calculation. In O2, CO2 and water vapor atmosphere, high-carbon ferromanganese powders were decarburized in a fluidized bed. When the temperature is respectively higher than 273, 1 226 and 1 312 K, the gas-solid decarburization reaction will occur between ferromanganese carbide on the surface of the high-carbon ferromanganese powders and different gas decarbonizers. Since metal manganese is easy to be oxidized by O2, CO2 or water vapor, the decarburization reaction will transfer into a solid-solid phase reaction of ferromanganese carbide and ferromanganese oxide, promoting external diffusion of carbon to achieve a further decarburization of high-carbon ferromanganese powders.
Solid-phase decarburization of high-carbon ferromanganese powders(HCFPs)was conducted using calcium carbonate powders(CCPs)as a decarburizer by microwave heating.Solid-phase decarburization kinetics was investigated by isothermal method.The results show that the HCFPs show excellent microwave absorption at a higher average heating rate of 80 ℃/min,while CCPs exhibit poor microwave absorption at a lower heating rate of 5-20℃/min;the heating characteristics are in-between when HCFPs and CCPs are mixed.The average heating rates of the mixture are 32.14,31.25,31.43,and 30.77 ℃/min when the mixture is heated up to 900,1 000,1 100,and 1 200℃,respectively.The good microwave absorption property of the mixed material lays the foundation for the solidphase decarburization of HCFPs containing CCPs.Solid-phase decarburization of HCFPs containing CCPs is a firstorder reaction by microwave heating.Apparent activation energy of solid-phase decarburization is 55.07kJ/mol,which is far less than that of ordinary carbon gasification reaction and that of solid-phase decarburization under the same decarburization condition by conventional heating.It indicates that microwave heating not only produces thermal effect,but also has non-thermal effect.
The solid-phase decarburization of high-carbon ferromanganese powders (HCFPs) was investigated using calcium carbonate as the decarburizer by microwave heating and conventional heating methods to explore the differences of microwave heating and conventional heating.Experimental results show that HCFPs containing calcium carbonate were heated up to 900,1 000,1 100,and 1 200 ℃ and held for 60 min for decarburization by microwave heating at decarburization ratios of 76.69%,82.90%,84.11%,and 85.75%,respectively.These ratios are higher than the decarburization ratios used for conventional heating under the same experimental conditions.The microwave heating can significantly improve decarburization ratio.This indicates the microwave heating field features a non-thermal effect,which in turn,visibly enhances the carbon diffusion ability of HCFPs.It also improves the kinetic conditions of solid-phase decarburization.
GUO Li-naCHEN JinSHI Wen-liZHAO JingLIU KeLIU Jin-ying
The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm.The relationships between bed voidage and such parameters as bed height,particle size,fluidizing air velocity,and air flow were obtained.Experimental results show that the powder material with high density can be fluidized in the spout-fluidized bed where the particle size is a key factor influencing the quality of fluidization.
