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Investigating the effect of lip froth washing on coal yield during flotation of a high ash South African coal

du Plessis Cherryl, Sibanda Vusumuzi, Dworzanowski Marek, Danha Gwiranai, Mamvura Tirivaviri A.

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 6

169--181

EN

An investigation was conducted to evaluate the effect of lip washing on coal flotation at Anglo American’s Goedehoop South (GHS) fine coal plant in South Africa. In the test-work, performance of cells with lip washing system were compared with baseline cells without lip washing in terms of coal yield and coal quality. Yields observed with lip washing were significantly higher than those of baseline cells. Improvements of up to 15% were recorded. The product obtained at low flotation reagent dosages (1.30–1.45 kg/t) on lip wash cells had ~16.85% ash content against ~17.65% with baseline cells, suggesting that higher yields could be achieved at superior qualities to those achieved with baseline cells. At higher reagent dosages (1.60–1.75 kg/t), coal yields further improved but quality reduced on lip wash cells. Calorific Values (CV) of coal products obtained by lip washing and baseline flotation were similar. When different coal particle size fractions were floated separately, the yield increased as particle size increased from 75 to 300 μm and then decreased from 300 to 500 μm for both baseline and lip washing flotation. Lip washing caused a marked increase in the yield for finer particles (< 300 μm) with optimum size class of between 212 – 300 μm. In addition, a much bigger increase in the yield was achievable with lip washing of lower quality coal. The ash content after lip washing of poor-quality coal were also comparable to the ash content after lip washing of good quality coal.

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Improving separation efficiency of galena flotation using the Aerated Jet Flotation Cell

Li Si, Wang Yuhua, Lu Dongfang, Zheng Xiayu, Li Xudong

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 3

513--527

EN

The low separation efficiency of traditional mechanical flotation cells for galena flotation primarily was caused by the low collision probability between bubbles and fine particles and high detachment probability of coarse particles. A flotation device named Aerated Jet Flotation Cell (AJFC) was adopted to improve the separation efficiency of galena flotation. Reducing bubble size and optimizing turbulence distribution were respectively confirmed as effective ways to improve fine galena-bubble collision efficiency and decrease detachment probability of coarse galena. In AJFC, micro-bubbles in diameter of 0.1-0.3 mm were generated by forcing compressed air to pass through porous high-density polyethylene tube, and high shear rate and appropriate turbulence were provided by installing a sparger with holes at the end of downcomer. The key parameters, including sparger hole number, turbulent kinetic energy (TKE), air-slurry ratio and superficial gas velocity (Jg) were optimized to achieve a desired separation performance of galena flotation. Separation efficiency of 62.54 % at a residence time of 2.25 min was achieved by AJFC, while separation efficiency of 59.12 % at a residence time of 7.5 min was achieved by mechanical flotation cell. Besides, AJFC had less loss of Pb in tailings than mechanical flotation cell in the whole particle size range, especially for fine (-25 µm) and coarse (+74 µm) size fractions.

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Determination of bubble size distribution in a laboratory mechanical flotation cell by a laser diffraction technique

Mazahernasab R., Ahmadi R.

Physicochemical Problems of Mineral Processing

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2016

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Vol. 52, iss. 2

690--702

EN

In this study, a laser diffraction technique (LDT) was used to measure size distribution of bubbles generated in a two-phase system in a laboratory mechanical flotation cell. In LDT, a laser light beam passed through the bubbles inside the measurement cell and the scattered light was recorded by detectors. In order to show the effectiveness of LDT, an image analysis technique (IAT) was applied in parallel to measure the size of bubbles. To determine the bubble size by IAT, around 200 images were taken in each test. In addition, the important operating parameters of the mechanical flotation cell affecting the bubble size distribution, including the impeller speed, aeration rate and frother concentration, were investigated. The response parameter in this study was Db(50) which represent the size of bubble at which there is 50% of the distribution. The results of this study showed that the LDT and IAT techniques were in a good agreement when Db(50) was in the range of -800+400 μm and there was a discrepancy for Db(50) in the range of -400+100 μm. Furthermore, Db(50) decreased from 727 to 284 μm when impeller speed increased from 700 to 1200 rpm. Additionally, an increase in the aeration rate from 1 dm3/min to 2.5 dm3/min led to a rise in Db(50) from 418 to 456 μm. Finally, increasing the frother concentration from 10 to 60 ppm reduced the Db(50) from 704 to 387 μm.