Effect of iron-containing binder on oxidation kinetics of magnetite pellets
The kinetics of pellet oxidation was studied by changing the ratio of iron-containing binders in magnetite pellets to 0％,4％and 8％.Firstly,the temperature range of magnetite powder oxidation was determined at 240.1-1 029.7 ℃ by TG-DTG-DSC analysis,and then isothermal oxidation kinetics experiments were carried out on pellets at 400-1 000 ℃ for 0-15 min.According to the change data of FeO content in pellets with oxidation time dur-ing the reaction process,the change law for the oxidation degree of pellets and the influence of iron-containing binder on the oxidation degree of pellets were analyzed.The experimental data were fitted by f(C)-t diagrams of 0,1st and 2nd order elementary reaction orders,respectively.The results show that the pellet oxidation reaction conforms to the kinetic law of the 1st order reaction,and the reaction rate constant k under different iron-containing binder ratios is determined.Finally,the activation energy of the reaction was calculated based on the unreacted core shrinkage model and the Arrhenius equation,and the limiting links of reaction were determined.The results show that in the low temperature section(400-700 ℃),the activation energy of the oxidation reaction is 23.40,20.83,20.73 kJ/mol re-spectively when the proportion of iron-containing binder is 0％,4％and 8％,which indicates that the iron-contai-ning binder can accelerate the oxidation process of pellets.The reason is that the precipitation of crystal water in binder increases the porosity of pellets,makes the contact between gas O2 and magnetite more sufficient,and the oxidation rate of pellets is faster.However,when the proportion of iron-containing binder increases from 4％to 8％,the oxidation rate of pellets increases slightly,because the decomposition and diffusion of crystal water in bind-er affect the oxidation of pellets.In the high temperature section(800-1 000 ℃),the reaction activation energy of different iron-containing binders are 43.37,35.16,35.98 kJ/mol,respectively,showing a trend of decreasing first and then increasing,which is indicating that excessive iron-containing binders are not conducive to the oxidation re-action.The research conclusions are of great significance for optimizing the ratio of iron-containing binders,impro-ving the quality of pellets and guiding the production of pellets.
iron-containing binderpellet oreoxidation kineticsunreacted shrinking core modelactivation energy
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