Basic Research On Preparation Of Spinel-type Manganese Ferrite By Solid-phase Reaction Of Ferromanganese Ore

High-iron manganese ore is an essential Fe-Mn composite mineral resource in China,which is a typical multi-metal co-existing ore with abundant reserves and great processing difficulties.The traditional beneficiation-smelting process,which aims at efficient separation of manganese and iron,leads to many problems of high energy consumption,high cost and pollution.The direct use of high iron manganese ore solid phase reaction method to prepare high value-added manganese spinel ferric acid,the manganese content of the product is not stable.Impurity elements in the mineral tend to enter the lattice of manganese ferroate and cannot be rejected.Therefore,there is a need to develop new technologies for the preparation of high value-added spinel-type manganese ferrite functional materials from high ferromanganese ores,to reduce the roasting temperature and provide production efficiency.Expanding the source of raw materials provides technical support and scientific basis for the high value-added resource utilisation of high ferromanganese ores.In this thesis,a systematic thermodynamic study of multiphase systems of Fe-Mn oxides is carried out.When the temperature is lower than 1407°C,Mn O can not be reduced to manganese metal,and when the temperature is higher than 685°C,iron oxides can be reduced to iron.The reduction temperature between 685°C and 1407°C can achieve the selective reduction of manganese and iron.During the oxidation process,it is found that spinel manganese ferrite can exist stably when the oxidation temperature exceeds 950°C,which provides theoretical support for the experiment.Study on the process of preparation of low ferromanganese concentrate by selective reduction magnetic separation with high ferromanganese ore as raw material.When the reduction temperature is 1050℃,the time is 5 h,the carbon ratio is 2.0,and the magnetic field intensity is 75 m T,the content of TFe in the magnetic product（low ferromanganese concentrate）is 63.2%and the content of manganese is 21.3%.The manganese grade in manganese rich slag is 51.19%,the manganese recovery is83.58%,and the manganese iron ratio is 5.16.The stable spinel structure of Mn Fe₂O₄can be formed when the calcination temperature is 1100°C and the calcination time is120 min.By magnetic separation,the saturated magnetization（Ms）,coercivity（Hc）and residual magnetization（Ms/Mr）of manganese ferrite are 71.53 emu/g,3.89 Oe and 0.057 respectively.In order to clarify the reaction mechanism and influence in the process of synthesizing manganese ferrate,analytical pure reagent was used for the experiment.In Mn O-Fe₂O₃ system,a stable spinel manganese ferrite structure can be formed when the calcination temperature is 1100°C for 60 min.M?ssbauer spectrum showed that each sample was superposed by two different sets of magnetic fine splitting hexahedral peaks.With the increase of calcination temperature,tetrahedral position（A position）changed like octahedral position（B position）,and the proportion of orthospinel increased.In the Mn O-Fe₂O₃-Si O₂ system,Si O₂ mainly exists in the free state when the calcination temperature is 900～1100°C,and the olivine phase(Mn_xFe_1-x)₂Si O₄（0<x<1）formation is the main limiting link when the calcination temperature exceeds 1100°C.In the Mn O-Fe₂O₃-Al₂O₃ system,when the roasting temperature is900～1100°C,Al₂O₃ mainly exists in the free state and a small amount of manganese aluminum ferrite.When the temperature is higher than 1100°C and the content of Al₂O₃ is more than 6 wt%,It will promote the conversion of Mn_xFe_3-xO₄ to manganese aluminumferrate Mn_y(Fe_3-y-zAl_z)O₄ as the main limiting link.