In depth analysis of alumina removal from iron ore fines using teetered bed gravity separator

The performance of floatex density separator (FDS) for alumina removal from iron ore fines of size <1˙0 mm has been studied. Screw classifier feed containing 4˙28% alumina has been used as the raw feed material. Desliming in hydrocyclone helps to reduce the alumina content down to 3˙39% by removing high alumina bearing ultrafine particles. Experimental campaign was undertaken considering a factorial design of experiments with three factors, namely teeter water rate, bed pressure and feed pulp density, to quantify the influence of various parameters. It was found that in single stage processing in FDS, 72% of the feed alumina could be removed. A concentrate containing 1˙66% alumina could be achieved at a yield of ∼57% in FDS. Higher teeter water was found to improve alumina removal albeit with a small decrease in iron recovery. It was observed that higher bed pressure and lower pulp density are favourable for alumina rejection. The present study established that underflow moisture is a good indicator of FDS performance. The misplacement of ultrafines in FDS underflow product increases linearly with underflow moisture content. It has been suggested that a feed with a narrow size distribution would be better suited for processing in the FDS. Splitting the feed into a coarse and a fine size fraction and treating them separately would be beneficial in obtaining still better alumina removal.