Flottasie van 'n growwe pirieterts in 'n luggeborrelde hidrosikloon
Thesis (MScEng) -- Stellenbosch University, 1986
ENGLISH ABSTRACT: High turbulence, high shear forces and high centrifugal forces characterise the flow in hydrocyclones. These characteristics are employed advantageously in the air-sparged hydrocyclone so that a space time of only one second is necessary for effective flotation. Conventional flotation processes on the other hand require a few minutes. Flotation of pyrite from a coarse Witwatersrand ore (100% -300 micron; 92% +38 micron) produces a sulphur recovery of 90% with a sulphur grade of 40% in the concentrate when the content of solids of the slurry feed equals 10%. Higher recoveries up to 93% are possible when slurries with a higher content of solids (e.g. 30%) are used. However, the sulphur grade then decreases to about 35%. Flotation in a batch cell produces a recovery of sulphur of 95% with a sulphur grade of 40%, but in this case a flotation time of 5 minutes is required. A hydrocyclone with a diameter of 50 mm and a length of 410 mm produces optimum results at a slurry feed rate of 35 to 40 l/min and an air-flow rate of 200 l/min. An air-flow rate of about 150 l/min is adequate at slurry feed rates lower than 35 l/min. Flotation of particles finer than 38 micron is more successful at higher slurry feed rates. The optimum flotation of coarse particles (i.e. +106 micron) occurs at lower feed rates. The best flotation results are obtained in the size fraction between 38 and 75 micron, which produces a recovery and content of sulphur of 95% and 51% respectively. A collector concentrate of 160 g/ton, which is thrice the quantity used in conventional processes, is required. The best recoveries at slurry feed rates lower than 35 l/min are obtained when the frother concentrate is low (approximately 20 mg/l). A higher frother concentrate, i.e. between 50 to 60 mg/l, is required at higher feed rates. The air-sparged hydrocyclone may be used effectively for rougher flotation and especially for the flotation of ore finer than 150 micron. The use of a specially designed pedestal can minimize blockage of the underflow. Such a pedestal has been designed and tested successfully.