Browsing by Author "Laker, Chris James"

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    Investigation of submerged trommel screen
    (Stellenbosch : Stellenbosch University, 2022-04) Laker, Chris James; Akdogan, Guven; Bradshaw, Steven Martin; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH SUMMARY: Trommels are investigated as an alternative to drain and rinse vibrating screens for the purpose of dense medium recovery. Iron ore and cyclone 40 atomized ferrosilicon were used to test screen performance on a submerged washing trommel. This trommel consists of two types of chambers, one for medium drainage and two submerged wash chambers to wash adhering medium. The performance of the drain chamber was evaluated with overflow properties such as moisture content, FeSi content and FeSi carryover, by varying medium relative density (RD) between 2.7 and 3.6. The results were compared to past studies on a vibrating drain and rinse screen by Kabondo (2018). The test work was performed on two separate trommel designs, Submerged DMS Trommel (Mk1) and Trommel Mk2. Due to design limitations in the design of Mk1, there was great uncertainty in the results from the first investigation. Mk1’s performance was however highly promising compared to vibrating drain screens. Percentage moisture in the overflow of Mk1 had a maximum of 3.60 % at a medium RD of 3.6, while vibrating screen results ranged between 10.29 % and 27.91 % at lower medium RDs below 2.3. % FeSi in the overflow of the drain chamber of Mk1 ranged between 11.05 % and 18.76 %, while the vibrating screen ranged between 9.71 % and 36.01 %. % FeSi carryover on Mk1 reached a maximum of 4.96 % while the vibrating screen ranged between 3.12 % and 10.46 %. In addition to competitive drainage of trommel Mk1, batch tests performed in the submerged wash chambers of Mk1, combined with bench tests for submerged washing and rinsing, concluded that the most effective washing method was motion of particles within a submerged bath. Efficiency for submerged washing ranged from 84.82 % to 99.7 %, compared to 74.24 % for rinsing of medium. It was justified to design a new test trommel, Mk2, from the learnings of the first campaign. The second trommel (Mk2) was designed with nine different underflow discharges. For the first time in open literature, trommel Mk2 provided insight into material distribution and utilised screen area of a trommel by evaluating these discharges. It was found that 98 % of drainage occurs through the middle and towards the direction of rotation of the trommel. The work on trommel Mk2 was performed at similar operating conditions as Mk1. The results of Mk2 had higher repeatability and statistical significance. Confidence was provided in the results and it was concluded that trommels is a competitive alternative to vibrating drain and rinse screens. Future work will include test work on all remaining operating parameters to develop a complete understanding how these parameters govern the operation of trommels.