Beneficiation of low-grade iron ore using individual and combined gravity and magnetic methods

The depletion of high-grade iron ore reserves has increased interest in beneficiating fine-grained, low-grade iron ores, including those from the Tang Zagh deposit in southern Iran. This study evaluated multi-gravity separation (MGS), wet high-intensity magnetic separation (WHIMS), and a combined MGS–WHIMS flowsheet for upgrading a low-grade iron ore sample containing ۴۵.۵۶% total Fe. Individual tests were conducted on three particle size fractions with d۹۰ values of ۳۸, ۷۵, and ۱۵۰ µm using three-stage rougher–cleaner–recleaner circuits under fixed operating conditions. In addition, combined tests were conducted on the particle size fractions with d۹۰​ values of ۳۸ and ۷۵ µm. Metallurgical performance was compared using concentrate grade, iron recovery, and the separation efficiency (S.E.) index. Both MGS and WHIMS showed a clear grade–recovery trade-off with decreasing particle size. WHIMS produced the highest concentrate grades, reaching ۶۲.۱۸% Fe, but showed substantially lower recovery, particularly in the finest fraction, where recovery declined to ۱۳.۶۰%. In contrast, MGS provided a better balance between grade and recovery, achieving ۶۰.۵۶% Fe at ۳۹.۱۳% recovery for the d۹۰ = ۳۸ µm fraction and outperforming WHIMS in overall separation efficiency. Relative to the three-stage WHIMS tests, the combined MGS–WHIMS circuit resulted in higher recovery and separation efficiency (S.E.), while producing concentrates with ۶۲.۱۰% Fe at ۲۷.۷۲% recovery for the d۹۰ = ۳۸ µm fraction and ۶۰.۷۹% Fe at ۳۴.۹۲% recovery for the d۹۰ = ۷۵ µm fraction. However, its overall separation efficiency remained lower than that of a standalone three-stage MGS. These results indicate that a three-stage MGS is the most effective route among the tested options for beneficiating fine-grained Tang Zagh iron ore. While, the combined circuit may be considered when a higher concentrate grade is prioritized over maximum recovery.

کلیدواژه ها:

Fine Hematite Particles ، Low-grade iron ore ، Multi-Gravity Separator (MGS) ، WHIMS ، Magnetic separation ، Tang_Zagh Mine