Hydrocyclones are widely applied devices in mineral processing due to their simple design, high capacity and low operational costs. Some of the main applications are classification in closed grinding circuits and desliming, as well as dewatering. However, hydrocyclones have an inherent inefficiency known as the fine particles bypass to the underflow stream, often associated with entrainment by water flow. Several approaches have been proposed to mitigate fine particle bypass, such as optimizing hydrocyclone design, adjusting apex and vortex finder diameters, water injection systems and improved inlet design. The objective of the present work was to assess hydrocyclone performance on different apex and vortex diameter combinations, seeking the reduction in fine particles bypass to underflow on the Paragominas bauxite processing industrial desliming circuit. Two different bauxite samples were used in a hydrocyclone classification test work, carried out on a specially built pilot plant. Six different combinations of apex and vortex were evaluated in a 254 mm diameter hydrocyclone, covering a range of apex-to-vortex diameters from 0.38 to 0.57. The results indicate operating conditions that significantly reduce fine particles bypass to underflow, increasing classification efficiency with minor effects in overflow selected size distribution parameter—d95. Accordingly, smaller apex-to-vortex ratios result in overall better performances, reducing fine particles bypass to underflow from 33% to 7%, as well as reducing the partition curve slope from 0.52 to 0.21 for one of the tested samples. Significant benefits are also obtained in terms of reducing the contents of reactive silica in the underflow of the optimized desliming hydrocyclone.
Reis et al. (Tue,) studied this question.