Study Of Dephosphorization On Hydrogen Selective-reduction Of Bayan Obo Niobium-bearing Iron Ore Powder

In this paper, the phosphorus transferring behavior was explored in the experiment inhydrogen selectively reducing Bayan Obo niobium-bearing iron ore powder and iron beingmeltingly separated from enrichment of niobium slag. The experiment was consisted bytwo parts: melting separating experiment and single factor experiment. The purpose of theexperiment is to find effective separation melting conditions that can realize the slag-metalseparation of reductive iron ore. On the basis of reading relative literature, themelt-separation temperature of the experiment was set at1450℃,1500℃,1550℃and1600℃. The melt-separation time was20min,25min and30min respectively and then thesingle variable experiment was performed. Through the melting experiment, the bestsmelting conditions was obtained: melt-separation temperature was1550℃andmelt-separation time was25min. The component of the slag phase and the iron phase wererespectively analyzed after the best condition melt-separation. After niobium-bearing ironore powder containing0.1%phosphorus was reduced by hydrogen and then melted, theniobium enriched slag which contained2%niobium was yielded and containingphosphorus less than0.01%. Meanwhile the iron contained niobium of0.0080%andphosphorus of0.23%. And niobium concentration of the niobium enriched slag was2.5times more likely to the niobium-bearing iron ore powder. The experimental resultsindicated that Ca3P2O8can also be reduced by hydrogen when iron oxides were reduced byhydrogen. So the aim that phosphorus and iron elements were separated from the niobiumenriched slag had achieved. In the single factor experiment, each factor of the reductiontemperature and the hydrogen flow rate was studied for exploring dephosphorization,deferrization in the niobium-bearing iron ore powder. The experimental variabletemperature value was:800℃,850℃,900℃,950℃,1000℃,1050℃and1100℃, andthe hydrogen flow rate:40L/h,60L/h,80L/h,100L/h and120L/h. The experimental resultsproved that when the reduction temperature was at800to1000℃and the hydrogen flowrate was in the range of40to120L/h, the phosphorus content in the slag were all <0.01%, but the phosphorus content in the iron increased with decreasing the reduction temperatureand hydrogen flow. The content of niobium in the iron was mainly affected by thereduction temperature, when the reduction temperature was higher than950℃, a part ofniobium mineral in the powder was reduced to silicate and mixed into the iron phase, thatresulted in decreasing niobium enrichment ratio in the slag phase. There were an optimumreduction temperature, an optimum range of hydrogen flow, an optimum melt-separationtemperature, and an optimum melt-separation time for the best dephosphorization,deferrization and the influence of niobium enrichment. The reduction temperature was at950℃, the range of hydrogen flow was100to120L/h, the melt-separation temperaturewas1550℃and the melt-separation time was25min.