The reduction of ilmenite concentrate in 30vol% CO–70vol% N_2 atmosphere was characterized by thermogravimetric and differential thermogravimetric(TG–DTG) analysis methods at temperatures from 1073 to 1223 K.The iso...The reduction of ilmenite concentrate in 30vol% CO–70vol% N_2 atmosphere was characterized by thermogravimetric and differential thermogravimetric(TG–DTG) analysis methods at temperatures from 1073 to 1223 K.The isothermal reduction results show that the reduction process comprised two stages;the corresponding apparent activation energy was obtained by the iso-conversional and model-fitting methods.For the first stage,the effect of temperature on the conversion degree was not obvious,the phase boundary chemical reaction was the controlling step,with an apparent activation energy of 15.55–40.71 k J·mol^(–1).For the second stage,when the temperatures was greater than 1123 K,the reaction rate and the conversion degree increased sharply with increasing temperature,and random nucleation and subsequent growth were the controlling steps,with an apparent activation energy ranging from 182.33 to 195.95 k J·mol^(–1).For the whole reduction process,the average activation energy and pre-exponential factor were 98.94^(–1)18.33 k J·mol^(–1) and 1.820^(–1).816 min^(–1),respectively.展开更多
The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of appare...The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy（Ea）were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction（G（α）=1-（1-α）~2,whereαis the conversion degree）plays an important role in the whole oxidation process.At the first stage（α=0.05-0.30）,the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage（α=0.30-0.50）,the oxidation process is completely controlled by the secondary chemical reaction（G（α）=1-（1-α）~2）.At the third stage（α=0.50-0.95）,the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G（α）=（1-α）^（-1）（β=10K·min^（-1）,whereβis heating rate）,G（α）=（1-α）^（-1/2）（β=15-20K·min^（-1））,and G（α）=（1-α）^（-2）（β=25K·min^（-1））,respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol^（-1）.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51374262)
文摘The reduction of ilmenite concentrate in 30vol% CO–70vol% N_2 atmosphere was characterized by thermogravimetric and differential thermogravimetric(TG–DTG) analysis methods at temperatures from 1073 to 1223 K.The isothermal reduction results show that the reduction process comprised two stages;the corresponding apparent activation energy was obtained by the iso-conversional and model-fitting methods.For the first stage,the effect of temperature on the conversion degree was not obvious,the phase boundary chemical reaction was the controlling step,with an apparent activation energy of 15.55–40.71 k J·mol^(–1).For the second stage,when the temperatures was greater than 1123 K,the reaction rate and the conversion degree increased sharply with increasing temperature,and random nucleation and subsequent growth were the controlling steps,with an apparent activation energy ranging from 182.33 to 195.95 k J·mol^(–1).For the whole reduction process,the average activation energy and pre-exponential factor were 98.94^(–1)18.33 k J·mol^(–1) and 1.820^(–1).816 min^(–1),respectively.
基金supported by the National Natural Science Foundation of China(Grant No.51234010)Special Fund for Basic Scientific Research in Colleges and Universities of the Central Business (No.0903005203413)
文摘The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy（Ea）were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction（G（α）=1-（1-α）~2,whereαis the conversion degree）plays an important role in the whole oxidation process.At the first stage（α=0.05-0.30）,the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage（α=0.30-0.50）,the oxidation process is completely controlled by the secondary chemical reaction（G（α）=1-（1-α）~2）.At the third stage（α=0.50-0.95）,the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G（α）=（1-α）^（-1）（β=10K·min^（-1）,whereβis heating rate）,G（α）=（1-α）^（-1/2）（β=15-20K·min^（-1））,and G（α）=（1-α）^（-2）（β=25K·min^（-1））,respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol^（-1）.
