Selection of cationic collector for reduction of alumina and silica in iron ore slimes of an operating plant by flotation

Abstract

Ultra fines or Slimes generated as overflow in screw classifiers in iron ore washing plants are generally treated in a single or multi-stage hydrocyclones to recover iron values. The underflow of the hydrocyclones forms the concentrate which is generally used for pellets making due to its attractive granulometry and high iron content. It is found, very often, that the performance of hydrocyclones is sub-optimum due to the frequent choking of their lower diameter spigots (cut-point being 20 µm). This affects the overall performance of the washing plant. Considering the granulometry (d80: 40.5 µm) of slimes, cationic reverse flotation of these slimes is thought to be apt to recover iron values by reducing alumina and silica levels. This is supposed to improve the productivity of the washing plant. As a prelude to detailed flotation studies, four cationic collectors which are generically same but of varying chemical composition are evaluated and tested for their performance in the reverse flotation of iron ore slimes from the screw classifier overflow of an operating iron ore washing plant in Bellary - Hospet sector of Karnataka, India. Basically these collectors are ether amines. A stage wise flotation is conducted by adding the collector in three stages. Starch is used to depress hematite. The performance of the four collectors was evaluated based on Tests of significance, namely,‘t-test’ and ‘F-test’ and modified version of Selectivity Index derived by Douglas to select the best one among them for further investigations.