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K P Galvin - One of the best experts on this subject based on the ideXlab platform.
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recovery and cleaning of fine hydrophobic particles using the reflux Flotation Cell
Separation and Purification Technology, 2020Co-Authors: M J Cole, J E Dickinson, K P GalvinAbstract:Abstract The Reflux Flotation Cell (RFC) consists of a vertical vessel located above a series of parallel inclined channels. This novel system, which is the inverse of an existing gravity separation system known as the Reflux Classifier, provides a powerful mechanism for enhancing bubble-liquid segregation. The usual link between the imposed gas flux and water recovery in the froth product is decoupled through this mechanism, resulting in the establishment of a concentrated bubbly zone throughout the upper section of the Cell, and no froth zone. A downwards fluidization arrangement promotes strong washing of the Flotation product, to remove the hydrophilic slimes from the hydrophobic concentrate. The mechanism also provides for strong control of the bias flux, allowing a significant positive bias flux to be established. A feed suspension of fine coal tailings containing hydrophobic coal and hydrophilic mineral matter was subjected to the novel Flotation, providing an ideal basis for studying the interplay between the hydrophobic particle recovery, inferred by the combustible recovery, and the product grade, inferred by the mineral matter content of the product, expressed by the ash %. The feed ash % was about 43 wt%. The product cleaning was compared to firstly, the results from the tree Flotation method, and secondly, a newer method known as Coal Grain Analysis (CGA). The RFC results were found to lie to the left of the tree curve, converging to the limit described by the CGA analysis. This work suggests the RFC and CGA provide a form of mutual validation on the limits of cleaning, though more work will be needed to confirm this finding. The RFC was operated with a volumetric feed flux of the order 1 cm/s, a rate comparable to that of conventional Flotation systems, with the bias flux ranging from 0.0 cm/s to 1.9 cm/s. For a fixed gas flux of 1.1 cm/s, increases in the liquid bias flux from 0.0 cm/s to 1.0 cm/s resulted in a decrease in product ash from 18.2% to 7.8%, and a reduction in combustible recovery from the order 87% to 75.6%. Operating at the lowest gas flux of 0.6 cm/s, and the strongest bias flux of 1.9 cm/s yielded a low product ash of 6.7% at the reduced combustible recovery of 64%.
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Flotation of coarse coal particles in the reflux Flotation Cell
Minerals Engineering, 2020Co-Authors: J L Sutherland, J E Dickinson, K P GalvinAbstract:Abstract Froth Flotation is a separation process that has widespread application throughout the coal and minerals industries. Conventional Flotation technologies are effective in recovering coal up to about 0.35 mm and dense minerals up to about 0.10 mm. There are significant benefits to both the coal and minerals industries in increasing the upper particle size. This paper reports on an investigation of coarse coal Flotation up to a nominal 2 mm size using the Reflux Flotation Cell (RFC). The first part of the investigation involved the Flotation of coal tracer particles added to the system individually, with the RFC operating at a specific hydrodynamic condition defined by the feed and gas fluxes. The particles were strongly hydrophobic, having relative densities (compared to water) within the range 1.25 – 1.30. The particles were saturated by the collector, diesel oil, prior to each experiment to ensure consistent hydrophobicity. The tracer particle experiments revealed a general trend of decreasing coarse particle yield with increasing gas flux. The yields were highest at gas fluxes below 0.5 cm/s, and largely independent of the volumetric feed flux over the range 0.9 to 6.0 cm/s. The data revealed a dependence on the gas volume fraction in the overflow, with the highest recoveries observed when held at nominally 0.80 or less. The second part of the investigation involved the Flotation of industrial coal slurry at 5 wt% solids concentration. The performance of the RFC was judged with reference to Tree Flotation for particles below 0.125 mm, and Float/Sink separation at a relative density of 1.6 for particles −2.0 +0.125 mm. Again, high recoveries of 82% to 97% for fractional sizes spanning −2.0 +0.125 mm were achieved provided the gas flux was below 0.5 cm/s. Product grade surpassed the tree curve using inverted fluidization water, without any recovery losses over the full particle size range.
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the kinetics of fast Flotation using the reflux Flotation Cell
Chemical Engineering Science, 2019Co-Authors: K Jiang, J E Dickinson, K P GalvinAbstract:Abstract This paper examines the kinetics of Fast Flotation of very fine, hydrophobic particles using a rectangular-sectioned downcomer in the Reflux Flotation Cell (RFC). Three separate downcomers of equal height and breadth, but different channel widths of 2, 4.5, and 9 mm, were used to investigate the recovery of particles ranging from 1 to 100 µm in diameter. The RFC utilises parallel inclined channels to enhance the segregation rate of rising bubbles in liquid, a phenomenon known as the Boycott Effect. This work was focused on the contribution of the downcomer kinetics to the Fast Flotation. Feed fluxes over the range of 0.9–8.6 cm/s were examined, with residence times in the downcomer of less than 1 s. Recovery due to entrainment was made consistent by fixing the portion of liquid reporting to the overflow to 10% of the feed volumetric rate, independent of the gas flux employed. Kinetic rate constants for the particle recoveries were analysed by varying Flotation parameters such as particle size, gas flux and feed flux, obtaining downcomer kinetic constants of up to 419 min−1. Distinct kinetic behaviour was found for the 1–10 µm and 10–100 µm coarser particles, with the kinetics of finer particles being more dependent on the particle size. The kinetics using the narrower downcomer widths (4.5 mm and 2 mm) relied more on the gas flux than the feed flux, while the kinetics using the wider downcomer width showed more dependence on the feed flux. Scaling laws for the kinetic rate constant were derived empirically based on the downcomer channel width, particle size, gas flux and feed flux. These scaling laws provided insight into the underlying mechanisms and a basis for exploring the potential Flotation performance over a wide range of system operational conditions. The narrower downcomers exhibited better performance at the feed fluxes
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fast Flotation of coal at low pulp density using the reflux Flotation Cell
Chemical Engineering Research & Design, 2015Co-Authors: J E Dickinson, K Jiang, K P GalvinAbstract:Abstract Fast particle Flotation is accomplished by maximising three fundamental aspects: the kinetics of particle–bubble attachment, the bubble interfacial flux for particle extraction, and the rate of bubble–liquid segregation. In practice, it has been impossible to extend all three aspects simultaneously using conventional Flotation devices. Hence, significantly higher processing rates using a single Flotation Cell has not been possible. Here, the Reflux Flotation Cell has been used in this work to address all three aspects in unison in a single stage of separation. This novel system permits throughput rates well beyond conventional Flotation standards. Stable operation using extreme gas and feed fluxes is accomplished using a system of parallel inclined channels located below the vertical portion of the Cell. In this paper a highly diluted coal feed comprised of well-liberated coal particles at 0.35 wt% solids, was prepared from hydrocyclone overflow. The volumetric feed flux was increased to nearly 10 times the typical conventional level, achieving an extremely low Cell residence time, in the order of 25 s. Very good combustible recoveries were obtained, with the +38 μm portion increasing from 92.3% to 98.5% with increasing gas flux. The partitioning of particles below 38 μm decreased with decreasing particle size until separation became governed by hydraulic entrainment, clearly evident at a particle diameter of ∼1.65 μm.
D.a. Deglon - One of the best experts on this subject based on the ideXlab platform.
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investigation of bubble particle attachment detachment and collection efficiencies in a mechanical Flotation Cell
Powder Technology, 2020Co-Authors: Hossna Darabi, D.a. Deglon, Bahram Rezai, S Javad M Koleini, Mahmoud AbdollahyAbstract:Abstract The paper presents the effect of impeller speed and superficial gas velocity on bubble-particle attachment, detachment and collection efficiencies using pure quartz particles in a mechanical Flotation Cell. Detachment and collection efficiencies in different parts of Cell were calculated by local turbulent energy dissipation rate measurements using high speed stereoscopic particle image velocimetry technique. In addition to high detachment efficiency, low attachment efficiency is also one of the reasons for low collection efficiency for coarse particles. The Flotation rate constant increased with an increase in superficial gas velocity. However, the effect of superficial gas velocity on collection efficiency was negligible. This means that any effect of superficial gas velocity on Flotation rate constant was due to changes in the number of bubbles and collision frequency. The Flotation rate constant, collision frequency, and the number of bubbles increased with increasing impeller speed. However, collection efficiency decreased with increasing impeller speed.
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investigation of bubble particle interactions in a mechanical Flotation Cell part 1 collision frequencies and efficiencies
Minerals Engineering, 2019Co-Authors: Hossna Darabi, D.a. Deglon, Bahram Rezai, S Javad M Koleini, Mahmoud AbdollahyAbstract:Abstract In this study the influence of impeller speed and superficial gas velocity on hydrodynamic parameters, bubble-particle collision frequency and efficiency using pure quartz particles of different sizes in an aerated Denver Flotation Cell was investigated. Collision frequency in different parts of Cell was calculated by local turbulent energy dissipation rate measurements. Collision efficiency due to gravitational, inertial, interceptional and turbulence mechanism was determined. The overall collision efficiency (Ec) was also investigated. The results showed that the bubble-particle frequencies for different particle sizes in the turbulent zone were 10–12 times higher than in the quiescent zone. Under various hydrodynamic conditions, minimum and maximum values of Ec were observed for −38 µm and −300 + 212 µm particles, respectively. The turbulence mechanism was the main collision mechanism for fine particles. The collision efficiency of coarse particles was mainly influenced by gravitational, inertial and interceptional mechanisms.
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Particle Image Velocimetry Study of the Turbulence Characteristics in an Aerated Flotation Cell
Industrial & Engineering Chemistry Research, 2017Co-Authors: Hossna Darabi, D.a. Deglon, S.m. Javad Koleini, Bahram Rezai, Mahmoud AbdollahyAbstract:The turbulence characteristics in the presence of bubbles is very important for multiphase processes such as froth Flotation. The turbulence characteristics in an aerated Denver Flotation Cell were investigated using a high speed stereoscopic particle image velocimetry technique at single-phase (water) and two-phase (water and air) systems to provide insight into the change in liquid phase hydrodynamics. The effect of the gas flow rate (0.043–0.125 cms–1) and Reynolds number (107 000–154 000) on the fluid flow properties were investigated. The results showed that the flow pattern at the both systems was the radial-type flow. The presence of air bubbles changed the local turbulence characteristics (mean velocity, the root-mean-square velocity, turbulence kinetic energy dissipation, and turbulence kinetic energy). The results obtained may be useful for deeper investigation about the effect of the turbulence properties on the hydrodynamic characteristics and subprocesses in the mechanical Flotation Cells.
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the effect of energy input on the Flotation of a platinum ore in a pilot scale oscillating grid Flotation Cell
Minerals Engineering, 2017Co-Authors: Mehdi Safari, M C Harris, D.a. DeglonAbstract:Abstract This study investigates the effect of energy/power input on the Flotation of a platinum ore in a pilot-scale oscillating grid Flotation Cell. Oscillating grids generate near ideal hydrodynamic environments, characterised by turbulence which is relatively homogeneous and isotropic. Secondary rougher feed and primary cleaner tail streams were floated in a pilot-scale oscillating grid Flotation Cell at power inputs from 0 to 2.5 W/kg, using 0.71 and 1.47 mm bubbles. From this study one may conclude that the effect of energy/power input on the Flotation rate is strongly dependent on the particle and bubble size. For large bubbles (1.47 mm), increasing energy input generally leads to an increase in the Flotation rate for finer particles (−25 μm) and an optimum Flotation rate for intermediate (+25–53 μm) & coarse particles (+53–75 μm). For small bubbles (0.71 mm), increasing energy input leads to a decrease in the Flotation rate for all conditions. Optimum conditions for PGM Flotation are using small bubbles at low energy inputs, or large bubbles at higher energy inputs.
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the effect of energy input on the Flotation of quartz in an oscillating grid Flotation Cell
Minerals Engineering, 2012Co-Authors: W T Massey, M C Harris, D.a. DeglonAbstract:Abstract This paper investigates the effect of energy input on the Flotation of quartz in an oscillating grid Flotation Cell. Oscillating grids exhibit relatively isotropic and homogeneous turbulence. Previous work was limited to power intensities of less than 0.60 W/kg. The current work uses a new oscillating grid Cell which operates at much higher power intensities. Quartz (sub 100 μm) was floated in the new Cell at power intensities from 0.5 to 5 W/kg and using three discrete bubble sizes (0.13 mm, 0.24 mm and 0.82 mm). Results show that the effect of power intensity on Flotation kinetics is strongly dependent on both particle and bubble size. For small bubbles, high Flotation rates are achieved at very low power intensities. For larger bubbles, Flotation rates increase with increasing power intensity for fine and intermediate particles, while an optimum power intensity is reached for coarser particles.
Emmanuel Manlapig - One of the best experts on this subject based on the ideXlab platform.
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comparison of gas hold up distribution measurement in a Flotation Cell using capturing and conductivity techniques
Minerals Engineering, 2006Co-Authors: Edy Sanwani, J-p. Franzidis, Yonggang Zhu, Emmanuel ManlapigAbstract:This paper presents and interprets results of experimental measurements of the spatial gas hold-up distribution in a 3 (3) glass rectangular Flotation Cell at the JKMRC using two different techniques. The gas hold-up device with the capturing technique was developed at the JKMRC and has been used widely in the P9 project(1) while the one with conductivity technique was developed at the CSIRO Thermal and Fluids Engineering laboratory at Highett, Victoria, Australia. Measurements were conducted at more than 64 locations in the Cell to determine the local gas hold-up distribution in the Cell. Since the measurements using the two techniques were conducted at the same locations, the results may be compared with each other. The results indicate that the gas hold-up varies widely inside the Flotation Cell. The gas hold-up distributions measured by the two techniques are relatively similar except in some locations which can be reasonably explained. (c) 2006 Elsevier Ltd. All rights reserved.
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The JKMRC high bubble surface area flux Flotation Cell
Minerals Engineering, 1999Co-Authors: M. A. Vera, J-p. Franzidis, Emmanuel ManlapigAbstract:The High Bubble Surface Area Flux Flotation Cell (HSbFC) is a 16-litre mechanical Flotation Cell with a bottom driven impeller, which is operated continuously. Bubble formation is carried out using an in-line mixer which enables the Cell to achieve superficial gas velocities (J(g)) equivalent to those generated in industrial Flotation Cells (0.7-1.2 cm/s). At the same time, the Cell produces considerably smaller bubble sizes, consequently, a high bubble surface area flux (Sb) Can be generated. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.
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studies on impeller type impeller speed and air flow rate in an industrial scale Flotation Cell part 3 effect on superficial gas velocity
Minerals Engineering, 1996Co-Authors: B K Gorain, J-p. Franzidis, Emmanuel ManlapigAbstract:Abstract Superficial gas velocity was measured at different locations in a 2.8 m 3 portable industrial scale sub-aeration Flotation Cell, treating zinc cleaner feed at Hellyer Concentrator in Tasmania, Australia. The Cell was fitted in turn with four different impeller-stator systems, and operated over a range of air flow rates and impeller speeds. Superficial gas velocity values ranged from 0.29 cm/sec to 6.4 cm/sec at the air flow rates employed. The distribution of air in the Cell was very dependent on the impeller type, as well as on the operating conditions in the Cell. For a well dispersed condition, the value of superficial gas velocity was uniform at different locations, whereas for flooding conditions the superficial gas velocity was very high near to the impeller and much lower away from the impeller.
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Studies on impeller type, impeller speed and air flow rate in an industrial scale Flotation Cell part 2: Effect on gas holdup
Minerals Engineering, 1995Co-Authors: B K Gorain, J-p. Franzidis, Emmanuel ManlapigAbstract:Abstract Gas holdup was measured at different locations in a 2.8 m 3 portable industrial scale subaeration Flotation Cell, treating zinc cleaner feed at Hellyer Concentrator in Tasmania, Australia. The Cell was fitted in turn with four different impeller-stator systems, and operated over a range of air flow rates and impeller speeds. The gas holdup was found to increase with increase in impeller speed as well as with increase in air flow rate, the manner in which it increased depended on the impeller type. Values ranged from 2% to 33%, with the greatest values produced by the Outokumpu impeller.
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Studies on impeller type, impeller speed and air flow rate in an industrial scale Flotation Cell — Part 1: Effect on bubble size distribution
Minerals Engineering, 1995Co-Authors: B K Gorain, J-p. Franzidis, Emmanuel ManlapigAbstract:Abstract Bubble size distributions were measured at different locations in a 2.8 m3 portable industrial scale sub-aeration Flotation Cell, treating zinc cleaner feed in the Hellyer Concentrator in Tasmania, Australia. The Cell was fitted in turn with four different impeller-stator systems, and operated over a range of air flow rates and impeller speeds. The mean bubble size was found to increase with increase in air flow rate at different locations in the Cell, for all four impellers, and to decrease with increase in impeller speed. The mean bubble size was largest close to the impeller shaft and smallest at the impeller discharge point, for all the impellers. The shape of the bubble size distribution also changed with location in the Cell. The “global mean” bubble size calculated by simple arithmetic average of the values at six locations in the Cell coincided remarkably well with the mean bubble size measured halfway between the impeller shaft and the side of the Cell, at the top of the pulp. In general, the impellers produced “global mean” values of 1.0 mm or less at the manufacturer's recommended impeller speed.
Mahmoud Abdollahy - One of the best experts on this subject based on the ideXlab platform.
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investigation of bubble particle attachment detachment and collection efficiencies in a mechanical Flotation Cell
Powder Technology, 2020Co-Authors: Hossna Darabi, D.a. Deglon, Bahram Rezai, S Javad M Koleini, Mahmoud AbdollahyAbstract:Abstract The paper presents the effect of impeller speed and superficial gas velocity on bubble-particle attachment, detachment and collection efficiencies using pure quartz particles in a mechanical Flotation Cell. Detachment and collection efficiencies in different parts of Cell were calculated by local turbulent energy dissipation rate measurements using high speed stereoscopic particle image velocimetry technique. In addition to high detachment efficiency, low attachment efficiency is also one of the reasons for low collection efficiency for coarse particles. The Flotation rate constant increased with an increase in superficial gas velocity. However, the effect of superficial gas velocity on collection efficiency was negligible. This means that any effect of superficial gas velocity on Flotation rate constant was due to changes in the number of bubbles and collision frequency. The Flotation rate constant, collision frequency, and the number of bubbles increased with increasing impeller speed. However, collection efficiency decreased with increasing impeller speed.
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investigation of bubble particle interactions in a mechanical Flotation Cell part 1 collision frequencies and efficiencies
Minerals Engineering, 2019Co-Authors: Hossna Darabi, D.a. Deglon, Bahram Rezai, S Javad M Koleini, Mahmoud AbdollahyAbstract:Abstract In this study the influence of impeller speed and superficial gas velocity on hydrodynamic parameters, bubble-particle collision frequency and efficiency using pure quartz particles of different sizes in an aerated Denver Flotation Cell was investigated. Collision frequency in different parts of Cell was calculated by local turbulent energy dissipation rate measurements. Collision efficiency due to gravitational, inertial, interceptional and turbulence mechanism was determined. The overall collision efficiency (Ec) was also investigated. The results showed that the bubble-particle frequencies for different particle sizes in the turbulent zone were 10–12 times higher than in the quiescent zone. Under various hydrodynamic conditions, minimum and maximum values of Ec were observed for −38 µm and −300 + 212 µm particles, respectively. The turbulence mechanism was the main collision mechanism for fine particles. The collision efficiency of coarse particles was mainly influenced by gravitational, inertial and interceptional mechanisms.
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Particle Image Velocimetry Study of the Turbulence Characteristics in an Aerated Flotation Cell
Industrial & Engineering Chemistry Research, 2017Co-Authors: Hossna Darabi, D.a. Deglon, S.m. Javad Koleini, Bahram Rezai, Mahmoud AbdollahyAbstract:The turbulence characteristics in the presence of bubbles is very important for multiphase processes such as froth Flotation. The turbulence characteristics in an aerated Denver Flotation Cell were investigated using a high speed stereoscopic particle image velocimetry technique at single-phase (water) and two-phase (water and air) systems to provide insight into the change in liquid phase hydrodynamics. The effect of the gas flow rate (0.043–0.125 cms–1) and Reynolds number (107 000–154 000) on the fluid flow properties were investigated. The results showed that the flow pattern at the both systems was the radial-type flow. The presence of air bubbles changed the local turbulence characteristics (mean velocity, the root-mean-square velocity, turbulence kinetic energy dissipation, and turbulence kinetic energy). The results obtained may be useful for deeper investigation about the effect of the turbulence properties on the hydrodynamic characteristics and subprocesses in the mechanical Flotation Cells.
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column Flotation Cell design by drift flux and axial dispersion models
International Journal of Mineral Processing, 2015Co-Authors: Mohsen Hemmati Chegeni, Mahmoud Abdollahy, Mohammad Reza KhalesiAbstract:Abstract A common problem in column Flotation research is designing the appropriate Cell which provides all the requirements of the desired tests. The drift flux model and the axial dispersion model were used in this paper for designing a column Flotation Cell for research purposes. To validate the approach, a column with required values of axial mixing coefficient ( E ), vessel dispersion number ( N d ), bubble diameter ( d b ), column height ( H c ) and gas holdup ( e g ) equal to 0.003 (m 2 /s), 0.32, 1.7 (mm), 1.15 (m) and 7.2 (%) were assumed respectively and the column diameter was calculated as 5.42 (cm) by the developed methodology. The Flotation column was constructed based on the calculated value of column diameter and required values of above-mentioned variables. Residence time distribution (RTD) of the liquid phase was measured for the column using the tracer impulse response method. Vessel dispersion number ( N d ) was measured from the RTD statistics equal to 0.32, which was completely similar to its required value. One other set of information from the literature was also used for validation and it was found that the methodology is capable of designing of columns with required specifications.
J E Dickinson - One of the best experts on this subject based on the ideXlab platform.
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recovery and cleaning of fine hydrophobic particles using the reflux Flotation Cell
Separation and Purification Technology, 2020Co-Authors: M J Cole, J E Dickinson, K P GalvinAbstract:Abstract The Reflux Flotation Cell (RFC) consists of a vertical vessel located above a series of parallel inclined channels. This novel system, which is the inverse of an existing gravity separation system known as the Reflux Classifier, provides a powerful mechanism for enhancing bubble-liquid segregation. The usual link between the imposed gas flux and water recovery in the froth product is decoupled through this mechanism, resulting in the establishment of a concentrated bubbly zone throughout the upper section of the Cell, and no froth zone. A downwards fluidization arrangement promotes strong washing of the Flotation product, to remove the hydrophilic slimes from the hydrophobic concentrate. The mechanism also provides for strong control of the bias flux, allowing a significant positive bias flux to be established. A feed suspension of fine coal tailings containing hydrophobic coal and hydrophilic mineral matter was subjected to the novel Flotation, providing an ideal basis for studying the interplay between the hydrophobic particle recovery, inferred by the combustible recovery, and the product grade, inferred by the mineral matter content of the product, expressed by the ash %. The feed ash % was about 43 wt%. The product cleaning was compared to firstly, the results from the tree Flotation method, and secondly, a newer method known as Coal Grain Analysis (CGA). The RFC results were found to lie to the left of the tree curve, converging to the limit described by the CGA analysis. This work suggests the RFC and CGA provide a form of mutual validation on the limits of cleaning, though more work will be needed to confirm this finding. The RFC was operated with a volumetric feed flux of the order 1 cm/s, a rate comparable to that of conventional Flotation systems, with the bias flux ranging from 0.0 cm/s to 1.9 cm/s. For a fixed gas flux of 1.1 cm/s, increases in the liquid bias flux from 0.0 cm/s to 1.0 cm/s resulted in a decrease in product ash from 18.2% to 7.8%, and a reduction in combustible recovery from the order 87% to 75.6%. Operating at the lowest gas flux of 0.6 cm/s, and the strongest bias flux of 1.9 cm/s yielded a low product ash of 6.7% at the reduced combustible recovery of 64%.
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Flotation of coarse coal particles in the reflux Flotation Cell
Minerals Engineering, 2020Co-Authors: J L Sutherland, J E Dickinson, K P GalvinAbstract:Abstract Froth Flotation is a separation process that has widespread application throughout the coal and minerals industries. Conventional Flotation technologies are effective in recovering coal up to about 0.35 mm and dense minerals up to about 0.10 mm. There are significant benefits to both the coal and minerals industries in increasing the upper particle size. This paper reports on an investigation of coarse coal Flotation up to a nominal 2 mm size using the Reflux Flotation Cell (RFC). The first part of the investigation involved the Flotation of coal tracer particles added to the system individually, with the RFC operating at a specific hydrodynamic condition defined by the feed and gas fluxes. The particles were strongly hydrophobic, having relative densities (compared to water) within the range 1.25 – 1.30. The particles were saturated by the collector, diesel oil, prior to each experiment to ensure consistent hydrophobicity. The tracer particle experiments revealed a general trend of decreasing coarse particle yield with increasing gas flux. The yields were highest at gas fluxes below 0.5 cm/s, and largely independent of the volumetric feed flux over the range 0.9 to 6.0 cm/s. The data revealed a dependence on the gas volume fraction in the overflow, with the highest recoveries observed when held at nominally 0.80 or less. The second part of the investigation involved the Flotation of industrial coal slurry at 5 wt% solids concentration. The performance of the RFC was judged with reference to Tree Flotation for particles below 0.125 mm, and Float/Sink separation at a relative density of 1.6 for particles −2.0 +0.125 mm. Again, high recoveries of 82% to 97% for fractional sizes spanning −2.0 +0.125 mm were achieved provided the gas flux was below 0.5 cm/s. Product grade surpassed the tree curve using inverted fluidization water, without any recovery losses over the full particle size range.
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the kinetics of fast Flotation using the reflux Flotation Cell
Chemical Engineering Science, 2019Co-Authors: K Jiang, J E Dickinson, K P GalvinAbstract:Abstract This paper examines the kinetics of Fast Flotation of very fine, hydrophobic particles using a rectangular-sectioned downcomer in the Reflux Flotation Cell (RFC). Three separate downcomers of equal height and breadth, but different channel widths of 2, 4.5, and 9 mm, were used to investigate the recovery of particles ranging from 1 to 100 µm in diameter. The RFC utilises parallel inclined channels to enhance the segregation rate of rising bubbles in liquid, a phenomenon known as the Boycott Effect. This work was focused on the contribution of the downcomer kinetics to the Fast Flotation. Feed fluxes over the range of 0.9–8.6 cm/s were examined, with residence times in the downcomer of less than 1 s. Recovery due to entrainment was made consistent by fixing the portion of liquid reporting to the overflow to 10% of the feed volumetric rate, independent of the gas flux employed. Kinetic rate constants for the particle recoveries were analysed by varying Flotation parameters such as particle size, gas flux and feed flux, obtaining downcomer kinetic constants of up to 419 min−1. Distinct kinetic behaviour was found for the 1–10 µm and 10–100 µm coarser particles, with the kinetics of finer particles being more dependent on the particle size. The kinetics using the narrower downcomer widths (4.5 mm and 2 mm) relied more on the gas flux than the feed flux, while the kinetics using the wider downcomer width showed more dependence on the feed flux. Scaling laws for the kinetic rate constant were derived empirically based on the downcomer channel width, particle size, gas flux and feed flux. These scaling laws provided insight into the underlying mechanisms and a basis for exploring the potential Flotation performance over a wide range of system operational conditions. The narrower downcomers exhibited better performance at the feed fluxes
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fast Flotation of coal at low pulp density using the reflux Flotation Cell
Chemical Engineering Research & Design, 2015Co-Authors: J E Dickinson, K Jiang, K P GalvinAbstract:Abstract Fast particle Flotation is accomplished by maximising three fundamental aspects: the kinetics of particle–bubble attachment, the bubble interfacial flux for particle extraction, and the rate of bubble–liquid segregation. In practice, it has been impossible to extend all three aspects simultaneously using conventional Flotation devices. Hence, significantly higher processing rates using a single Flotation Cell has not been possible. Here, the Reflux Flotation Cell has been used in this work to address all three aspects in unison in a single stage of separation. This novel system permits throughput rates well beyond conventional Flotation standards. Stable operation using extreme gas and feed fluxes is accomplished using a system of parallel inclined channels located below the vertical portion of the Cell. In this paper a highly diluted coal feed comprised of well-liberated coal particles at 0.35 wt% solids, was prepared from hydrocyclone overflow. The volumetric feed flux was increased to nearly 10 times the typical conventional level, achieving an extremely low Cell residence time, in the order of 25 s. Very good combustible recoveries were obtained, with the +38 μm portion increasing from 92.3% to 98.5% with increasing gas flux. The partitioning of particles below 38 μm decreased with decreasing particle size until separation became governed by hydraulic entrainment, clearly evident at a particle diameter of ∼1.65 μm.