Kinetics of thermal decomposition of hydrated minerals associated with hematite ore in a fluidized bed reactor
来源期刊：International Journal of Minerals Metallurgy and Materials2017年第3期
论文作者：P.C.Beuria S.K.Biswal B.K.Mishra G.G.Roy
文章页码：229 - 239
摘 要：The kinetics of removal of loss on ignition（LOI） by thermal decomposition of hydrated minerals present in natural iron ores（i.e.,kaolinite,gibbsite,and goethite） was investigated in a laboratory-scale vertical fluidized bed reactor（FBR） using isothermal methods of kinetic analysis.Experiments in the FBR in batch processes were carried out at different temperatures（300 to 1200°C） and residence time（1 to 30 min） for four different iron ore samples with various LOIs（2.34wt% to 9.83wt%）.The operating velocity was maintained in the range from 1.2 to 1.4 times the minimum fluidization velocity（Umf）.We observed that,below a certain critical temperature,the FBR did not effectively reduce the LOI to a desired level even with increased residence time.The results of this study indicate that the LOI level could be reduced by 90% within 1 min of residence time at 1100°C.The kinetics for low-LOI samples（<6wt%） indicates two different reaction mechanisms in two temperature regimes.At lower temperatures（300 to 700°C）,the kinetics is characterized by a lower activation energy（diffusion-controlled physical moisture removal）,followed by a higher activation energy（chemically controlled removal of LOI）.In the case of high-LOI samples,three different kinetics mechanisms prevail at different temperature regimes.At temperature up to 450°C,diffusion kinetics prevails（removal of physical moisture）;at temperature from 450 to 650°C,chemical kinetics dominates during removal of matrix moisture.At temperatures greater than 650°C,nucleation and growth begins to influence the rate of removal of LOI.
P.C.Beuria1，S.K.Biswal1，B.K.Mishra1，G.G.Roy2
1. Institute of Minerals and Materials Technology,Council of Scientific & Industrial Research2. Indian Institute of Technology
摘 要：The kinetics of removal of loss on ignition（LOI） by thermal decomposition of hydrated minerals present in natural iron ores（i.e.,kaolinite,gibbsite,and goethite） was investigated in a laboratory-scale vertical fluidized bed reactor（FBR） using isothermal methods of kinetic analysis.Experiments in the FBR in batch processes were carried out at different temperatures（300 to 1200°C） and residence time（1 to 30 min） for four different iron ore samples with various LOIs（2.34wt% to 9.83wt%）.The operating velocity was maintained in the range from 1.2 to 1.4 times the minimum fluidization velocity（Umf）.We observed that,below a certain critical temperature,the FBR did not effectively reduce the LOI to a desired level even with increased residence time.The results of this study indicate that the LOI level could be reduced by 90% within 1 min of residence time at 1100°C.The kinetics for low-LOI samples（<6wt%） indicates two different reaction mechanisms in two temperature regimes.At lower temperatures（300 to 700°C）,the kinetics is characterized by a lower activation energy（diffusion-controlled physical moisture removal）,followed by a higher activation energy（chemically controlled removal of LOI）.In the case of high-LOI samples,three different kinetics mechanisms prevail at different temperature regimes.At temperature up to 450°C,diffusion kinetics prevails（removal of physical moisture）;at temperature from 450 to 650°C,chemical kinetics dominates during removal of matrix moisture.At temperatures greater than 650°C,nucleation and growth begins to influence the rate of removal of LOI.
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