Improving the Quality of Ferruginous Chromite Concentrates Via Physical Separation Methods

Abstract

The low chromium‐to‐iron ratio of chromite ores is an important issue in some chromite deposits. The value of the chromite ore is indeed dictated in the market by its iron, as well as its chromium content. In the present study, a chromite concentrate was reprocessed by gravity (spiral concentrator) and magnetic separation to enhance the chromium‐to‐iron ratio. Also, detailed characterization studies including automated mineralogy were carried out to better understand the nature of the samples. Enhancing the chromium‐to‐iron ratio was achieved by using advanced spiral separators which will be discussed in this paper.

A Process Mineralogical Evaluation of Chromite at the Nkomati Nickel Mine, Uitkomst Complex, South Africa

“…In particles less than 100 µm, the force of the flowing water is more dominant than the force of gravity and these particles are lost to the tailings. At smaller particles sizes the chromite grains also record densities similar to the gangue and are thus lost to the tailings [4]. This explains the higher Cr 2 O 3 grades and recoveries for the PCMZ ores at coarse grinds and highlights the importance of the target grind being more important than liberation.…”

“…Most of the gravity techniques however, become inefficient particularly when treating fine particle sizes that are smaller than 75 µm, as the forces associated with water flow become more dominant than the forces associated with gravity resulting in losses to the tailings [2]. In addition, at smaller particle sizes the gangue minerals have similar densities to chromite which renders gravity separation inefficient ( [4] and references within).…”

“…Chromite is a member of the spinel group and is the only economically important ore mineral of chromium. It is used extensively by the metallurgical industry as feedstock for ferroalloy production [1][2][3][4]. Chromite ore is commonly classified into different grades based on the Cr/Fe ratio as well as the Cr 2 O 3 content.…”

“…The lower grade deposits, with low Cr/Fe ratios (i.e., high iron content and low Cr 2 O 3 content) were as a result not mined. These low-grade deposits have however, been exploited and successfully upgraded using physical methods such as gravity separation [1,4]. Such advances in chromite beneficiation offered an opportunity to investigate the chromite-bearing ore from the Uitkomst Complex at the Nkomati nickel mine.…”

Editorial for the Special Issue: “Physical Separation and Enrichment”

“…Magnetic separation also uses the magnetic properties of different minerals, and the most common application of this method, as one may expect, is separation of iron and iron-bearing minerals [5]. In this Special Issue, Tripathy et al [6] discuss improving the quality of ferruginous chromite concentrates using gravity and magnetic separation. The value of chromite ores is determined by their iron and chromium contents.…”