Study On Flash Magnetization Roasting Technology For Refractory Low-grade Red Iron Ores

Magnetizing reduction is one of the most effective operations in the treatment of the refractory low-grade red iron ores, and in a rather long period, It is a most effective means of recycling utilization of refractory red iron ore in China. However, it is difficult to be widely used, because the traditional magnetization roasting technology has several disadvantages, such as poor quality of product, high energy consumption, high costs, much investment and little benefits. Moreover, in recent years, there is no actual breakthrough in magnetization roasting either in technology development or in equipment research, so there is no breakthrough in effective exploitation of plentiful red iron resources.In this dissertation, a new "flash magnetization roasting and low intensity magnetic separation" technology in solving the problem of utilization of refractory low-grade red iron ores has been explored. The development of new types of magnetization roasting equipment has been researched in the bench scale test;the method of fluidized bed roasting was applied in improving roasting environment, shortening roasting duration and reducing energy consumption. Through the theoretical calculations and cold model tests, it was proved that the particle of iron ore can exactly suspend in fluidized bed. Iron ore particle (-0.355mm) which contain a lot of ferrous silicate gangue was charged into the flash magnetizing roasting furnace at temperature of 600⁸50℃, particle are suspended fluidized-bed by hot gas, the gas mainly consist of 4.9¹8.1% CO₂ , 0⁰.1% O₂, 0.1⁹.0% CO% and others. Along with the increasing of gas-solid contact area, thus fasten the velocity of heat transfer, mass transfer and reaction process, so weakly magnetic iron minerals (Hematite, Limonite, Siderite, etc.) are converted into magnetite with strong magnetism in the furnace within several seconds, but the magnetism of gangue has changed little. Then most iron minerals in reduced product can be separated by low intensity magnetic separation.Low grade iron concentrate(T_Fe30³5%) of Daye Iron Mine which mainly consist of Hematite, Siderite, ferrous Silicate and so on was used as test specimen, iron concentrate(T_Fe59⁶2%)could be obtained by flash magnetization roasting andlow intensity magnetic separation technology, its iron recovery of concentrate is between eighty-two and eighty-six percent. And the whole process of magnetization roasting just takes about 10⁶0 seconds, so the prediction that it takes only several seconds to finish magnetization roasting of this iron ore is proved scientific.Flash magnetization roasting trial has tested the velocity of red iron ore magnetization reducing reaction successfully, provided with theoretical basis for research of large-scale fluid bed magnetization roasting equipment. It is expected that the fluid bed roasting magnetization technology will further shorten roasting duration from about 80 minutes to several seconds;this new technology suggests new routes for red iron ore utilization in China. At the same time, it will provide with reference for the technological reform in some Iron Enterprises, such as Jiugang, Baogang and Daye, and will create enormous economic benefits and social significance.