Reduction Characteristics of Carbon-Containing REE–Nb–Fe Ore Pellets

Bo Zhang,Chengjun Liu,Maofa Jiang,Yong Fan,Yun Ye

doi:10.3390/met8040204

Abstract

To separate and recover the valuable metals from low-grade REE (rare earth elements)–Nb–Fe ore in China, the reduction characteristics of carbon-containing REE–Nb–Fe ore pellets, including mineral phase variation, reduction degree, and reaction kinetics, were observed based on thermogravimetry experiments. The results showed that the reduction and separation efficiency of valuable metals in the carbon-containing pellets were superior to the ones in the previous non-compact mixture. After the reduction roasting of the pellets at 1100 °C and a subsequent magnetic separation, the iron powder with a grade of 91.7 wt % was separated, and in magnetic separation tailings the grades of Nb2O5 and (REE)O were beneficiated to approximately twice the grades in the REE–Nb–Fe ore. The reaction rate of the reduction of the carbon-containing pellets was jointly controlled by the carbon gasification reaction and the diffusion of CO in the product layer with an activation energy of 139.26–152.40 kJ·mol−1. Corresponding measures were proposed to further improve the kinetics condition.

Highlights

Bayan Obo ore, Inner Mongolia in China is a well-known multimetallic iron ore deposit, which accounts for 35% of the world’s REE reserves and 5.5% of the world’s Nb reserves, in addition to abundant iron ore [1]
The grade of REE–Nb–Fe ore beneficiated from the tailings could still not meet the requirements of the Nb industry and REE industry [3]
To improve the reduction process, the carbon-containing pellets were of ore and carbon can be reduced at moderately high temperatures to produce direct-reduction iron (DRI) within a rotary prepared through a pressure the mixture of the REE–Nb–Fe fine ore and the pulverized hearth furnace (RHF),molding which has with been proven to be environment-friendly and economically viable carbon

Summary

Introduction

Bayan Obo ore, Inner Mongolia in China is a well-known multimetallic iron ore deposit, which accounts for 35% of the world’s REE reserves and 5.5% of the world’s Nb reserves, in addition to abundant iron ore [1]. To separate and recover valuable metals from the low-grade REE–Nb–Fe ore, a process comprising of reduction roasting, magnetic separation, and sulfuric acid (H2 SO4 ) leaching was proposed in our previous investigation [4]. The REE–Nb–Fe fine ore and pulverized coal were mixed and roasted in a graphite crucible at an optimal temperature. The REE–Nb–Fe fineenhances ore and pulverized coal wereresistance mixed and roasted in a graphite crucible at an optimal temperature. To improve the reduction process, the carbon-containing pellets were of ore and carbon can be reduced at moderately high temperatures to produce DRI within a rotary prepared through a pressure the mixture of the REE–Nb–Fe fine ore and the pulverized hearth furnace (RHF),molding which has with been proven to be environment-friendly and economically viable carbon.

Mineral Phase Variation and Separation Efficiency of the Valuable Metals

7.29 REVIEW

Kinetic Analysis of Reduction Reaction

10. Schematic

Conclusions