Niobium and phosphorus behavior during melting-separation process of pre-reduced niobium ore concentrate

The pre-reduced Bayan Obo ferroniobium (FeNb) ore concentrate block was taken as raw materials for studying the physical properties of niobium-enriched slag and changes in niobium recovery rate. In addition, the dephosphorization rate of the slag under different melting-separation conditions was investigated using the melting-separation test. The research results demonstrate that (i) the niobium recovery rate and dephosphorization rate of the slag decrease with the increase in melting-separation temperature; (ii) the niobium recovery rate of the slag initially increases and then decreases with increase in basicity and time; and (iii) the dephosphorization rate of the slag increases with the increase in basicity and time. When the test was performed under the conditions of basicity of 0. 6 - 0. 7, time of 7-10 min, and temperature of 1400-1450 °C, the niobium recovery rate and dephosphorization rate are over 96% and 95%, respectively. By scanning electron microscopy, it is observed that niobium mainly exists in the form of calcium and titanium silicate within the slag phase, with uneven distribution.