The Air-Sparged Hydrocyclone (ASH) is a high capacity flotation device which is alleged to be more efficient for the flotation of fine particles than conventional flotation equipment. The principal aims of this thesis were to investigate the use of an ASH in the flotation of South African coal ultrafines ( -150 micron), and to determine the effect of various design and operating parameters on the performance of the process, in terms of the product yields and grades obtainable. The testwork was carried out on a typical Witbank coal, from the Kleinkopje Colliery, with an ash content of 23.7 %. The coal was characterised by means of size, ash-by-size and float-and-sink analyses. Batch flotation experiments were carried out to provide a benchmark against which the ASH could be compared. Preliminary ASH work was carried out to determine the required collector and frother dosages and the optimal slurry feed rate. A fractional factorial design, at two levels, was carried out to investigate the effects of the underflow configuration (the use of an orifice and a baffle instead of the conventional pedestal/annular opening), the ratio of the overflow to underflow openings (A*), the ASH length to diameter ratio (Lc/dc), the ratio of the air to slurry feed rates (Q*), the ratio of the vortex-finder length to the cyclone diameter (Lvtfdc) and the size of the slurry inlet (Ainlet)· The effect of pulp density was investigated separately. The results of the testwork showed that the ASH beneficiated the coal successfully at capacities of up to 300 times those possible in conventional (batch) flotation, and in the -region of 1500 times those achieved using the same coal in a column cell. The overall results, in terms of concentrate ash contents at particular yi e ids, showed that the ASH results were comparable with those of the batch cell, but not as good as those of the column cell. The nature of the material being floated resulted in collector dosages in the region of 36 kg/ton being used in the factorial design to achieve concentrate yields in the region of 50 %. However, use of the optimal ASH configuration reduced this required collector dosage to about 25 kg/ton, without loss in performance. A typical (good) ASH result achieved was a yield of 47.7% at a concentrate ash content of 8.8 %. Size analyses indicated that the ASH product is recovered by both flotation and classification with the result that, for the small diameter ASH and Kleinkopje coal sample used, the ASH could not be considered to be a more efficient device for the flotation of fine particles, but rather a less efficient device for the recovery of coarse particles. However, the ASH performance in the ultrafine size fractions (-150 micron) was comparable with that of the batch cell~ The underflow configuration, A* and Lcfdc all had a significant effect on the performance of the ASH. Q* had a minor effect, Lvfldc may have had an effect and Ainlet had no effect on the performance of the ASH. In addition, increasing the pulp density from 1.6 to 9.4% (mass/volume) had no effect on the performance of the ASH. It is recommended that future research include the investigation of preconditioning for the flotation of poorly floatable (inertinite rich) South African coals, the use of an ASH on more floatable coals, the determination of the limit to which the pulp density can be increased (without loss in flotation performance) and the determination of scale-up criteria for the ASH.

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