The Behavior And Kinetics Of Hydrogen Reduction During Producing Magnitite From Shanxi Guangling's Refractory Hematite

Iron ore is the main raw material for the steel industry and the stable development of a country's steel industry is closely related to the development and utilization of its iron ore resources.With the continuous decrease of high grade iron ore resourses and increase of demand for steel,it has been a big problem for China's steel industry to rely heavily on imported iron ore.So,the exploration and utilization of low-grade and refractory hematite in China is very important and strategic for the development of China's steel industry.At present,reducing magnetization and magnetic separation is considered to be a promising approach to produce high grade magnetite from the low-grade,fine-grained and refractory hematite.But the key technology,which is coal magnetization reduction,has many disadvantages,such as higher reducing temperature,green-house gas production and lower recovery of iron.So,in this paper we propose a new magnetization reduction method of magnetization reducing with hydrogen under low reducing temprature.Compared to coal magnetization reduction,it has the advantages of lower reducing temperature,higher concentrates quality and lower carbon deposition in concentrates and it also has the advantage of making full use of coal oven gas.In this paper,the reduction of Shanxi Guangling's refractory hematite ore fine by hydrogen at low temperature was carried out in a fluidized-bed reactor with stirring apparatus,and the magnetic separation of magnetite ore fine obtained by hydrogen reduction was carried on by laboratory Davis magnetic tube.The composition,phase,structure of raw hematite ore,reduced products and magnetic concentrate were analyzed and characterized by chemical analysis method,X-ray diffraction,optical microscope and scanning electron microscope,respectively.The influences of the various reducing factors on the hydrogen magnetizing reduction are estimated by setting orthogonal experiments and according to the results of the orthogonal experiment,the corresponding single factor experiments are carried out.The reduction properities and the hydrogen magnetization reduction kinetics of the Shanxi Guangling refractory hematite are investigated by hydrogen programmed reduction technology.The conclusions obtained are as follows:?Shanxi Guangling's hematite is a sedimentary type iron ore,and the crystallization of iron mineral granularity is very thin.The texture of Guangling's hematite ore is sand cemented structure and similar oolitic structure.The grade of Shanxi Gangling hematite is very low and it consisted of 28.63%TFe.The iron in the ore mainly exists in hematite,limonite and a small amount of magnetite and the recovery of iron can reach to 98.52%,in theory.So,the Shanxi Guangling hematite is typical fine-grained,low-grade and refractory hematite.?The hydrogen magnetizing reduction temperature of Shanxi Guangling's hematite range from 400? to 571 ?.The transition of Shanxi Guangling's hematite(Fe2O3)to magnetite(Fe304)follows a shrinking unreacted core model.Under the given reducing time and with the increase of reducing temperature,the average utilization of hydrogen increases first and finally tends to be a constant value.The size of the new generation magnetite' grain increases first,and then decreases slightly and final continues to increase.The former increase of size of the new generation magnetite's grain is advantageous to the dissociation of the ore,but the latter increase of size of the new generation magnetite's grain is unfavorable.?As the conversion of Fe2O3 increases,the concentrate grade decreases but the recovery of total iron increases.After reduced at 450? for 0.5 hour and milled in a rod mill for 20 minutes,a concentrate with a higher grade(grade:56.99%,iron recovery:49.66%)can be obtained through a simple magnetic separation process with working electrical current of 2A(magnetic filed intensity of 0.156T),or after reduced at 400? for 2.5 hours and milled in a rod mill for 20 minutes,the concentrate with a higher iron recovery(grade:52.06%,iron recovery ratio:72.56%)can also be gained.?The kinetics of hydrogen magnetization reduction has been obtained by by hydrogen programmed reduction technology.The kinetics equations are as follow:(?)...