The Experimental Study Of Nb-bearing Ore With Direct Reduction For Preparing Nb-enriched Slag

Niobium is an important strategic material in materials industry and high technology fields, and is widely used in industry of national defense, iron and steel, superconductivity and electronic industry etc. Aiming at the problem of efficiently utilizing the Fe-Nb-RE resource of Baryunebo mine, direct reduction followed by magnetic separation is investigated in present work, which can give the theoretical references for industrial application in future. The iron and niobium can be separated by the magnetic separation and Nb-enriched slag can be obtained. we contrastively analyse how the reduction temperature, reduction time and the rate of carbon and oxide (C/O) effect on the degree of metallization and size of iron grain of pellets for niobite concentration ore. Then we can obtain the optimum reduction process and the optimum reduction parameters for manufacturing niobium enriched slag.Summarizing the research content, the main conclusions include:(1) According to thermodynamic analysis, under the standard condition, on the basis of reduction characteristics of niobium oxides and iron oxides, by controlling the parameters such as reaction temperature, we intend to apply direct reduction process on selective reduction of niobium concentrate ore followed the magnetic separation and Nb-enriched slag can be obtained. The above is the main theoretical basis for experimental investigation.(2) When the temperature is excessive, the pellets will be melted and direct reduction cannot be used; While the temperature is not enough, the degree of metallization is low, the iron grain is small; At1200℃, the degree of metallization is very high, reached90%, and the iron grain has grown up and separated with slag obviously. This kind of form is beneficial for the separation of iron and slag.(3) When the C/O equals0.7and0.8, due to lack of the reducing agent, the degree of metallization is very low. While C/O equal0.9, after20min, the degree of metallization is much higher than the above samples, the degree of metallization is above90%. If we extend the reduction time, due to the reducing atmosphere is weakened and the reoxidation is easily occured.(4) Summering the experimental results, the optimum reduction parameters are0.9of C/O,1200℃and20min. Based on these optimized parameters, the iron phase has gathered obviously and has also been independent with the slag phase, the majority of Nb are inset between slag and iron phase in the form of TiNbO4, and few of them are in the form of NbC, and we can separate Nb from iron and get Nb-riched slag through the magnetic separation way(5)The content of Nb-riched slag after Melting separation is4.3%, the yield of niobium is only69.4%. After grinding3min, The content of Nb-riched slag after magnetic separation is5.16%, and the the yield of niobium is89%.Nb-enriched slag is obtained, which is a good feed for producing ferroniobium or metallic niobium in electric furnace. These experimental results can give some theoretical references for efficiently utilize the Fe-Nb-RE resource of Baryunebo mine and industrial application in future.