| The quality of iron ore oxide pellet is developed and the consuming energy in production is reduced obviously by using High Pressure Roll Grinding (HPRG) which has been applied widely in iron ore oxide pellet production. Majority of the research in function of HPRG in iron ore oxide pellet are related to the improvement of green ball quality, but less to the function of HPRG in consolidation of iron ore oxide pellet with few points. Study of the function of HPRG in consolidation of iron ore oxide pellet has profound significance for the application of HPRG in the production of iron ore oxide pellet and promotes the progress of production of iron and steel industry.The function and mechanism of HPRG as material-pretreating technology in the consolidation of iron ore oxide pellet were researched systematically in this dissertation, using Yuanjiacun hematite concentrate and Ekou magnetite concentrate as raw materials and the modern analytic technologies of X-ray diffractometry, laser-size, Optical Microstructure, etc, in terms of the relationship of characteristics of iron ore concentrate after being pretreated by HPRG, such as the specific surface area, lattice distortion extent, particle-size distribution, the content of fine particles, the dispersion extent and the consolidation characteristics of preheated and roasted pellets, as well as the effects of HPRG on the Macrostructure and Microstructure of preheated and roasted pellets, Oxidation dynamics of magnetite pellet, with the results as following:(1) The research results revealed that the compression of hematite preheated and roasted pellets was obviously developed by HPRG, but not for the magnetite preheated and roasted pellet.(2) The study of the relationship between the characteristics of iron ore concentrate after being pretreated by HPRG and the consolidation characteristics of iron ore oxide pellet revealed that when raw materials of hematite and magnetite were pretreating respectively, the bad dispersion of pretreated materials and the increase of fine particles were the main reasons that affect the compression of iron ore oxide pellet.(3) The iron ore concentrate was compacted hardly under high pressure roller and consequently massive compact particle-particle unites were remained in iron ore pellet, which promoted the increase of particle-particle contact areas; meanwhile the development of size distribution and increase of fine particles content, especially for the-0.005mm both contributed to the compact extent of iron ore pellet and surface-activation, promoting the solid phase reactivity, all of which contributed to the formation, growth and contact of fine Fe2O3, as well as to the crystallization process of Fe2O3 under high temperature, promoting the increase of compression.(4) The result of oxidation dynamics of magnetite pellet revealed that the oxidation process of magnetite pellet was controlled by the oxygen diffusion in pellet and it was not changed by HPRG, but the apparent activation energy of magnetite oxidation increased 10.58 kJ/mol between 850℃-1000℃. The increase of compaction of magnetite pellet and the bad dispersion of pretreated materials both not only promoted the solid phase reactivity, but also promoted the oxidation rate of magnetite and the formation of compact layer on the magnetite pellet surface, restricting the diffusion of oxygen. Therefore the oxidation extent of magnetite pellet was lowered, promoting the double layer formation and the increase of internal stresses of magnetite roasted pellet, which limited the compression increase of magnetite oxidized pellet. |
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