Hydrocyclone applied in the physical processing of phosphate concentrate containing rare earth elements

Abstract

Rare earth elements comprise of lanthanides plus yttrium and scandium. They have several applications and are produced by a limited number of countries. Brazil has an estimated reserve of 22 million metric tons and most of the minerals are associated with phosphate. In the fertilizer industry, ores containing rare earth elements are combined with phosphates, fluorides, silica, limestone, titanium and gypsum. As a result, rare earth oxides (REOs) are lost with sterile dump and mining waste or are applied to the soil together with fertilizers. In this scenario, the composition and granulometry of raw and sterile materials from a phosphate producing unit were evaluated. Considering the concentration of REOs, equal to 1.56 wt% in the Catalão (GO) phosphate concentrate and the increase in concentration with the decrease in size, the objective of the present work was to separate the fraction smaller than 25 μm with a new mini- hydrocyclone. The variables such as cone angle, length of the cylindrical region, underflow orifice diameter and feed pressure influenced the following responses: capacity, underflow- to- throughput ratio, total efficiency and concentration of REOs in the overflow stream. The separator capacity was found to range from 881.5 to 1449.0 kg/h while the underflow-to-throughput ratio was between 9 and 40% and the total separation efficiency remained at around 96%. The lowest concentration of rare earth oxides obtained in the overflow stream was 79.5% higher than the concentration in the feed, corroborating the choice of hydrocyclone as a method of concentration of REOs.