Assessing the effect of cone ratio, feed solids concentration and viscosity on hydrocyclone performance

• Main Author: Muzanenhamo, Pharaoh Kudzaishe
• Other Authors: Mainza, Aubrey
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2015
• Subjects: Chemical Engineering
• Online Access: http://hdl.handle.net/11427/13325

Includes bibliographical references. === In the mineral processing industry, comminution circuits contain slurries composed of a mixture of particles of varying degrees of liberation and size. Hydrocyclones are commonly used to classify these particles. If the classification stage is not efficient, both grinding and flotation cannot be optimised or operated efficiently. Ores that are mined in industry contain metals of varying specific gravity, which makes recovery of the desired metal challenging. This study focussed on the effect of the hydrocyclone spigot to vortex finder diameter ratio, termed as the cone ratio, solids concentration and viscosity on the classification of two dual density ores. The rheological characteristic of the overflow was also evaluated. A UG2 ore (Upper Group), which consists mainly of silicates, and chromite, and an iron ore, containing mainly iron and silicates, were used as feed material. The UG2 test work was carried out on a University of Cape Town (UCT) 4 inch Multotec cyclone, while the iron ore test work was carried out on an Anglo-American 4 inch Krebs cyclone. The cyclone performance was assessed using the corrected cut size, water recovery to the underflow, sharpness of separation and feed throughput. The rheological characterisation of both the UG2 and iron ore were carried out using an AR (ARES-G2) 1000EX vane rheometer. The results obtained indicated that the cyclone cone ratio, feed solids concentration and viscosity influence the cyclone performance. For the UG2 it was observed that as the cone ratio increased the cut size decreased and levelled off at a cone ratio of 1. However, for the iron ore it was observed that the cut size increased with an increase in the cone ratio, until it reached a peak at a cone ratio of approximately 0.68, before decreasing. The water recovery to the underflow increased with cone ratio and solids concentration and for both ore types. However it was observed that the water recovery was more sensitive to the cone ratio within the range of conditions investigated. The sharpness of separation for the UG2 ore increased with cone ratio for all solids concentrations investigated and reached a peak at a cone ratio of approximately 1 then decreased. The sharpness of separation for the iron ore illustrated different trends at different feed solids concentration. Between 10 and 20 wt. % feed solids concentration the sharpness of separation for iron ore was fairly constant, while at 50 wt. % solids concentration the sharpness of separation increased with cone ratio and then levelled off at a cone ratio of 0.67. An increase in the volumetric throughput with cone ratio was observed for both ore types. Rheological characterization revealed Bingham plastic behaviour for both ore types. An increase in the feed viscosity led to an increase in the cut size, water recovery and sharpness of separation for both UG2 and iron ore. A comparison of the results with a semi mechanistic model revealed a good fit for the volumetric throughput, water recovery and viscosity. However, the sharpness of separation and cut size had more scatter. The standard error for the sharpness of separation model fit was 21% for UG2 and 23% for iron ore while the error for the cut size was 41 % for the UG2 ore and 43 % for the iron ore. It was recommended that for future work, test work should be carried at a constant pressure in order to assess purely the effect of cone ratio. Furthermore, a coarser ore should be used in order to evaluate the effect of cone ratio and feed viscosity on the individual deportment of the prevalent components in the dual density ore types investigated by carrying out assays.