Analysis of interfacial reaction behavior between magnetite and laterite nickel ore in pellet oxidation roasting process
In order to reveal the consolidation mechanism between magnetite and laterite nickel ore in the process of pellet oxidation roasting,the interfacial reaction between magnetite and laterite nickel ore in this process was studied by diffusion couple method.The results show that after oxidation roasting at 1 300 ℃ for 120 min,most of the Fe3O4 in the magnetite that does not contact with the laterite nickel ore is oxidized to hematite(Fe2O3),and some silicate phases fill voids to assist consolidation.This layer is mainly composed of Fe2O3 recrystallization,and the consolidation strength is high.A diffusion layer is formed at the junction of magnetite and laterite nickel ore.The main phase in the diffusion layer is magnesia-iron spinel((Mg,Fe)O·Fe2O3),and a small amount of silicate liquid phase is filled to assist consolidation.A large amount of Mg diffuses from laterite nickel ore to magnetite,and forms magnesia-iron spinel after diffusion.The formation of magnesia-iron spinel hinders the oxidative recrystallization of magnetite,which is not conducive to the improvement of compressive strength of pellets.The laterite nickel ore not in contact with magnetite is mainly composed of forsterite,glassy and hematite.Among them,the content of for-sterite is the highest,and the glassy is filled in the gap between forsterite,while hematite exists in glassy.Because of the low content of Fe2O3 in laterite nickel ore,the dispersed Fe2O3 has less contact due to the barrier of a large amount of forsterite during high temperature roasting.It is difficult for Fe2O3 crystals to effectively connect and grow,and a large amount of Fe2O3 is scattered in the whole laterite nickel ore in a fine crystal state.Therefore,the consolidation strength of this part is poor.The results provide a theoretical basis for the preparation of high strength oxidized pellets containing chromium nickel iron ore.
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