Flotation Cell Research Articles

Simulation of bubble–particle attachment process and estimation of attachment probability using a coupled smoothed particle hydrodynamics–discrete element method model

The bubble–particle attachment is an important step in determining the success of recovery in froth flotation. In this study, the bubble–particle attachment process was investigated using a coupled smoothed particle hydrodynamics (SPH)–discrete element method (DEM) model. The effects of particle inertia and the drag of fluid flow on the particle motion were examined. The sliding time was determined for different particle sizes, densities, and bubble sizes, and the simulated sliding time was compared with the analytical solution and our own experimental results using a high-speed camera. As the particle size and density increased, the sliding time decreased. However, this value was independent of the bubble size. The induction time was calculated as a function of the particle size and contact angle from an empirical model, and it was used to determine the attachment and net probabilities in a dynamic simulation. Based on the SPH–DEM simulation results, novel probability models were developed for bubble–particle interactions. Both attachment and net probabilities could be decoupled into hydrodynamic and thermodynamic effects, given that the collision probability was also derived as a single function of the particle Stokes number. The developed probability models embodying the mutual influence of bubbles and particles can be extended to macroscopically describe flotation cells and evaluate cell performance including particle recovery.

Intensification of coal slime separation in fluidized bed flotation column: change of turbulence

ABSTRACT Flotation cell and flotation column are widely used as the separation equipment for coal slime. In order to obtain better flotation results for different particle sizes, different turbulence intensity of flow field need to be created, but the turbulence intensity is not easy to adjust in conventional flotation equipment. In this paper, a new fluidized bed flotation column was designed to control turbulence intensity by the liquid velocity and static bed height. The effects of liquid velocities (0.198 m/s,0.226 m/s,0.254 m/s) and static bed heights (0.317 m,0.343 m,0.380 m) on coal slime flotation with different particle sizes were studied, which were evaluated by the combustible recovery, ash content, and the yield of clean coal. The research results showed that the flotation performance of coarse particles is better with low turbulence caused by low liquid velocity and great static bed height than that in high turbulence. Under the condition of high liquid velocity and low bed height, a high turbulence intensity environment is created, and the fine particle separation efficiency is better than that in low turbulence.

Valorization of copper smelter slag through the recovery of metal values by a synergistic bioprocess system of bio‐flotation and bio‐leaching

AbstractSlag sample generated as solid waste from a copper plant in Southern Africa contains strategically important base metals like copper, nickel and cobalt. X‐ray diffraction and X‐ray fluorescence analysis confirmed the presence of fayalite (Fe2SiO4), silica (SiO2) and alumina (Al2O3) as the major mineral phases in the slag sample. The presence of alumina and silicate minerals in copper slag are the major obstacles in the recovery of base metals in mineral processing industries. The copper slag may be hazardous if abandoned to the environment but it may be a valuable resource if the metal values can be recovered. Hence, the present study focused on the application of a bio‐surfactant extracted from Lactobacillus fermentum bacterium as a bio‐collector in the flotation of the slag sample to reduce its silica and alumina content. Subsequently, the slag sample was subjected to bio‐leaching by Acidithiobacillus ferrooxidans bacterium for recovery of the metal values. Flotation batch experiments were conducted in 1 L scale Denver flotation cell and during the process, about 37.90% of silica and 22.82% alumina were removed from the slag sample. The findings from this study further revealed the effectiveness of the bio‐surfactant‐assisted flotation process on the bio‐leaching of base metals from the slag sample. Flotation of silica and alumina from the slag improved bio‐leaching performance and recovered about 74.0% of copper, 60.0% of nickel and 33.4% cobalt in the bio‐leaching process conducted at laboratory scale.

Metallurgical testing and CFD simulation of StackCell® SC-50 high-intensity flotation machine

An extensive field test was conducted by Rio Tinto and Eriez to evaluate the operability and metallurgical performance of a StackCell® SC-50 high-intensity flotation machine for recovery of copper and molybdenum from flotation tailings. The field test of the 15-m 3 StackCell flotation cell was conducted at Rio Tinto’s state-of-the-art tailings recovery demonstration plant located within Kennecott Utah Copper’s tailings facility. The metallurgical results demonstrate that the StackCell technology provides a unique solution for recovering metal values from tailings, with excellent selectivity and an order of magnitude increase in flotation kinetics compared to conventional mechanical flotation machines. The metallurgical advantages of the StackCell are particularly pronounced for treating fine tailings, with upgrade ratios >25 achieved at average copper and molybdenum recoveries of 20% and 28%, respectively, within approximately one minute of flotation residence time. Computational fluid dynamics (CFD) simulations were conducted to provide a fundamental explanation of the findings from metallurgical field measurements. The simulations show that maximum levels of turbulent dissipation rates in the StackCell contacting chamber are nearly 5 times that of rotor/stator mechanisms in conventional mechanical flotation machines. Furthermore, the high levels of turbulent dissipation rates in the contacting chamber are favorable for high collisions and attachments rates of fine particles with air bubbles.

Development of a flotation simulator that can predict grade vs. Recovery curves from mineral liberation data

Flotation is a kinetic process designed to separate mineral fines by control of hydrophobicity . In general, both the recovery and selectivity of a flotation process increase with contact angle. It is difficult, however, to model flotation kinetics using the thermodynamic parameter. In the present work, we consider flotation as heterocoagulation so that the bubble-particle interactions occurring in the pulp phase of a flotation cell can be modeled using the hydrophobic force as a kinetic parameter that can represent the role of contact angles in flotation. The pulp-phase model developed in this manner has been combined with a froth-phase model developed earlier by considering the effect of particles in film thinning kinetics and bubble coarsening (Park et al, 2018). The combined model has been used to develop a flotation simulator that can be used to construct grade vs . recovery curves from feed characteristics ( e.g ., mineral liberation and particle size) and various operating parameters. The simulator has been tested successfully against a set of bench-scale continuous flotation test results reported in the literature (dos Santos and Galery, 2018).

Flotation behaviour in reflux flotation cell – A critical review

• The roles of three major components of the Reflux Flotation Cell are introduced. • The flux mechanism formed in the boundary of major components is discussed. • Three theories adapted to characterise the Reflux Flotation Cell were explained. • The operating parameters of the Reflux Flotation Cell were evaluated. • Future research directions on the Reflux Flotation Cell are recommended. The development of new flotation equipment has to address the challenges confronting the minerals industry, the low flotation efficiency of fine and coarse particles and the need to process a higher volume of ores due to the decreased feed grades. By combining a downcomer, a fluidised bed and inclined channels within one equipment, the Reflux Flotation Cell (RFC) offers a general solution to improving fine and coarse particle flotation while maintaining a high throughput. Current research on the RFC has proven its success in coal flotation. Based on the published research work, this paper introduces the history of RFC development, illustrates the unique structure of the RFC and the role of each major component, discusses the flux mechanism formed in the boundary between the fluidised bed and inclined channel section, explains the main theories adapted to characterise the RFC and evaluates the effect of the operating parameters on its performance. This information provides a general picture of the RFC from both theoretical and practical perspectives. This paper also recommends future research on the RFC to expand its application from coal flotation to minerals flotation and also model the bubble motion in inclined channels and the flux mechanism in the boundary area, both of which dictate the performance of the RFC.

Mechanical Flotation of Mineral Particles with an Underwater Speaker

ABSTRACT This paper aims to demonstrate a safe, non-chemical approach for improving the efficiency of froth flotation. Laboratory scale flotation tests for quartz particles of different sizes (< 20 µm, 20–38 µm, 38–75 µm, 75–106 µm, 106–150 µm, 150–212 µm) with an ether amine collector at different dosages were conducted in batch mode by using a bottom-driven mechanical flotation cell. An underwater loudspeaker was placed in the flotation pulp phase. The solids concentrations tested were 5% and 20% by weight. The results showed that acoustic sound (at 375 Hz and 77 decibels) increased the flotation recovery by at least 6% over a broad particle size range (i.e. 20–212 micron). The results also suggested applying acoustic sound in a flotation system can improve flotation recovery to a larger extent at a lower reagent dosage. An advantage of having the loudspeaker immersed in the pulp phase rather than in air above the flotation cell was the substantially reduced noise level. The present study provides a potential approach for improving flotation performance and reducing the chemical reagent consumption in flotation cells.

Technological assessments on recent developments in fine and coarse particle flotation systems

• Froth flotation of fine and coarse particles is studied, focusing on cell designs. • Generating micro-bubbles, intensive turbulence, and high gas hold-up are advantages of intensified cells. • Scaling up/down procedures for the intensified cells are found unclear. • Positioning the optimum location of discussed cells in flotation circuits is found challenging. After more than a century applying flotation to the mining industry, two completely different strategies have been introduced for processing purposes. One is the classical approach viz. grinding ores to a certain extent (fine particles) and floating them via conventional mechanical and pneumatic cells i.e., Jameson, Imhoflot™ and Reflux™. This strategy continues because mines face declining cut-off grades, complex and poly-mineralized ores, and they are required to achieve an acceptable degree of mineral liberation. The other school of thought deals with coarse particle processes mainly owing to the low energy requirements, that includes SkimAir® flash, fluidized bed and HydroFloat™ cells. There is no study in the literature to comparatively present the recent developments of flotation apparatuses versus the conventional mechanical cells. To cover this knowledge gap in the literature, the present paper endeavors to critically evaluate these concepts from several points of view, including existing technological advancements, water and energy usage, kinetics, and circuit design. A brief introduction of advanced technologies, along with their applications is presented. The data from literature and case studies showed that the Jameson, Imhoflot™ and recently developed Reflux™ flotation cells can be very effective for recovering fine particles owing to their specific hydrodynamic designs, intensive energy dissipation rate and generation of micron-sized bubbles (100–700 µm). Very low (less than a few minutes) mean particle residence time, high gas-hold up (ca. 50–70 %), no agitation and high efficiency of particle-bubble collision were identified as their main advantages compared to traditional mechanical flotation cells. In addition to their common applications in cleaner stage, these cells were used in pre-flotation and scalping (producing final concentrate from the rougher feed) duties. Their main challenges were recognized as relatively unclear procedure on their scale up/down, optimization and simulation. The HydroFloat™ cell was indicated as a promising technology for recovering coarse particle fraction sizes by taking advantage of the fluidized-bed concept with plug-flow dispersion regime, high particle residence time, and limited cell turbulence. We finally concluded that fine particle flotation may remain as the main focus of re-processing tailings dams, while coarse particle treatment should be the focus of this century to reduce total energy consumptions.

Dense liquid flotation: Can coarse particle flotation performance be enhanced by controlling fluid density?

• Bubble-load is optimized in bubble-particles aggregates of fine particles compared to coarser ones. • Coarser particles simulate the detachment behavior of finer particles at increased fluid SGs. • Increased critical detachment amplitudes at increased fluid SGs translate to better flotation performance for coarse particles in terms of recovery, rate, and maximum floatable size. • Increasing fluid SG beyond a limit increases the likelihood of detachment in the froth phase. • Particle weight in fluid is the major detachment force, and the effect of cell turbulence on coarse particle flotation performance is largely dependent on it. In this work, we investigate the influence of fluid density on bubble-particle detachment and coarse particle flotation performance. Detachment studies were carried out using an electro-acoustic apparatus in a dense liquid environment using a lithium heteropolytungstate (LST) mixture with subsequent flotation studies carried out in a micro flotation cell at varying fluid densities. Our results indicate that bubble load was inherently limited by particle surface area and weak particle–particle interactions at coarser sizes. Coarser particles tend to follow the detachment behavior of relatively finer particles at increased fluid density. We also found that flotation performance in terms of recovery, rate, and maximum floatable size can be enhanced by controlling fluid density within a stated limit beyond which detachment in the froth phase causes overall performance to drop.

A new approach to measure gas holdup in industrial flotation Machines. Part III: Industrial prototype design and assessment

• An industrial gas holdup sensor prototype was validated in a 250 m 3 flotation cell at Los Pelambres. • A weakly dependence of sensoŕs discharge coefficient to Reynolds number was observed. • Gas holdup predictions were largely insensitive to errors in the anticipated pulp kinematic viscosity. • Submersible sensor provided robust accurate gas holdup measurement over long periods of time. An industrial gas holdup sensor was designed, constructed, and its performance assessed on a 250 m 3 self-aerated Wemco cell at Los Pelambres concentrator. The submersible sensor comprised a ceramic-liner IP68 magnetic flowmeter assembled to a stainless steel gas exclusion cell, which resembles an inverted truncated cone. The gas exclusion cell was designed to avoid low-velocity sections where particles could settle. When the sensor device is vertically immersed in an aerated pulp a continuous downward flow of pulp without bubbles is induced through it. A remotely installed processing unit converts the flow velocity signal, provided by the magnetic meter, into a gas holdup signal, by applying Bernoullís equation to the induced flow. The ideal velocity in the Bernoullís equation is obtained by multiplying the measured velocity and the discharge coefficient. The discharge coefficient was found to be fairly constant over a wide range of Reynolds numbers. Gas holdup measurements were compared against those obtained by sampling a fixed volume of aerated pulp using the JK Tech Air Holdup Probe. These tests were conducted on different days over nine months to allow for the pulp properties to change. Gas holdup changes in the flotation machine were achieved by restricting the air intake to the cell by placing a stainless steel cap on top of the air suction pipe. Short and long-term testing demonstrated the sensoŕs capability to provide reliable and accurate continuous-time gas holdup measurements for industrial flotation machines.

Oxidation-reduction effects in the flotation of copper sulfide minerals and molybdenite – A proof of concept at industrial scale

Redox potential (Eh) control plays a significant role during sulfide mineral flotation by influencing the reactions on the surface of the minerals and accordingly the flotation behaviour. In this study, the metallurgical performance of typical copper sulfide minerals, molybdenite as well as gangue minerals (e.g., pyrite, tennantite, and enargite) under different pH and Eh conditions of the flotation cell were investigated. The copper and molybdenum processing plant at the Sungun complex-Iran were selected as a case study. For this purpose, Eh of flotation cells of phases 1 and 2 of copper and molybdenum processing circuits – Sungun complex – were measured by off-line method. After performing chemical analysis, the mineralogical study of the input load and products of each of the aforementioned flotation circuits in the rougher, cleaner, re-cleaner, and scavenger stages was performed. Based on the results, the potential in cells of phases 1 and 2 of copper concentration plants is in the range of −60 to −100 mV; and for the molybdenum plant, is in the range of −500 to −700 mV. The potentials of more than −100 mV in the phases of copper concentration plants have created suitable conditions for the separation of copper sulfide and molybdenite minerals from gangue minerals, especially pyrite. Adjustment of Eh in the range of −500 to −700 mV in the molybdenum processing plant has also led to the depression of copper minerals and the flotation of molybdenite, resulting in the effective separation of these minerals. However, grade analysis and mineralogical studies indicate the misplaced copper minerals into tailings, the passage of chalcopyrite and pyrite to molybdenum concentrate, the misplaced molybdenite to copper concentrate, and also the presence of minerals containing harmful elements such as arsenic in copper concentrate. Eh fluctuations in phase 1 and 2 of copper plants, the interaction of copper sulfide minerals, especially chalcopyrite with pyrite (and the depression of pyrite in Eh more than −100 mV), are reasons for the misplaced copper minerals into tailings. The interaction of chalcopyrite and pyrite with molybdenite and the high flotation tendency of molybdenite at the potential of +600 mV is the main factor in increasing the Cu and Fe grade in molybdenite concentrate. The interaction of copper minerals with arsenic-bearing minerals and the similar flotation behavior of these minerals in the potential of the rougher cells of the molybdenum processing plant has increased the arsenic grade in the copper concentrate or molybdenum tailings.

The effect of feed solids concentration on flotation performance using the Reflux Flotation Cell

This study examines the separation performance achieved using the Reflux Flotation Cell (RFC) when treating low economic value coal waste streams over a range of feed solids concentrations. Feed solids concentrations of 1.3, 2.4 and 5.7 wt% were examined using a fine coal suspension of nominally 50 wt% head ash, covering the typical range emerging from the overflow of a desliming hydrocyclone. This work was also extended to include much higher levels of ultrafine gangue through the addition of significant levels of silica, resulting in an extreme feed ash of 97 wt% head ash, the aim being to assess whether these levels of gangue minerals affect hydrophobic particle capture. For the actual plant feed, as the feed solids concentration was increased the flux of hydrophobic particles fed to the RFC increased in a fixed ratio to the flux of hydrophilic particles. These results showed a greater gas flux was required to maintain combustible recovery as the feed flux of hydrophobic particles increased. The relationship between bubble surface coverage and hydrophobic particle recovery was also investigated. Estimates of the average bubble surface coverages, ranging 6–18%, showed a decreasing trend between recovery and surface coverage. By establishing a strong positive liquid bias flux, ∼0.7 cm/s in magnitude, the product ash was maintained within a narrow band of 7.0–11.9 wt% ash across the series of experiments, demonstrating consistent and strong product desliming over the up to 16-fold increase in feed solids concentration.

Considering Specific Ion Effects on Froth Stability in Sulfidic Cu-Ni-PGM Ore Flotation

The mining and mineral processing of Cu-Ni-PGM sulfide ores in South Africa occurs in semi-arid regions. The scarcity of water resources in these regions has become one of the biggest challenges faced by mineral concentrators. As a result, concentrators are forced to find ways through which they can manage and control their water usage. The recycling and re-use of process water in mineral concentration plants has therefore become a common practice. This practice is beneficial in that it reduces reliance on municipal water and harnesses compliance to stringent environmental regulations on freshwater usage. This approach also offers a better response to the Sustainable Development Goals (SDGs) for the mining industry, as water and its preservation form part of the SDGs. This practice could, however, be somewhat concerning to a process operator because recirculated water often has higher concentrations of ions compared to fresh or potable water. This is because an unintended change in the process water quality may affect critical aspects of flotation such as the stability of the froth. This issue has led to the need for both the mining industry and researchers in the field to find the ions in process water that have the greatest impact on froth stability. Thus, the authors of this study investigated the effects of various ions common in the process water of a typical Cu-Ni-PGM ore on froth stability using a 3 L bench scale flotation cell. Solids and water recoveries were used as proxies for froth stability. These were further complemented by bubble size, water recoveries, foam height, and dynamic foam stability from two-phase flotation systems. A two-phase foam study resulted in observations that supported findings from a three-phase study. Generally, single salt solutions containing Ca2+ and Mg2+ ions resulted in higher water recoveries both in the two-phase foam and three-phase froth studies, increases in foam heights and dynamic foam stability, and a decrease in bubble size compared to the solutions that contained Na+. SO42− also resulted in increased foam stability compared to Cl− and NO3−. These results showed that the divalent inorganic electrolytes—Ca2+, Mg2+, and SO42−—were more froth- and foam-stabilizing than the monovalent inorganic electrolytes—Cl−, NO3−, and Na+. This finding was in agreement with previous research. The findings of this study are deemed crucial in the development of a process water management protocol in sulfidic Cu-Ni-PGM ore concentrators. However, more comparative three-phase froth stability tests are needed as subjects of future investigative work to further ascertain specific ion effects on froth stability in sulfide ores.

Investigating the System Flotation Kinetics of Fine Chalcopyrite in a REFLUX™ Flotation Cell using a Standardised Flotation Cell Reference Method

• Performance ratio was proposed to compare froth flotation technologies. • Performance was based on the relative cell product flux at a given recovery. • Product cleaning was quantified using a selectivity parameter. • Reflux Flotation cell was compared to a batch mechanical cell. • Performance ratio ranged from 3 to 20 fold. There is increasing recognition of the need to develop and optimise the individual sub-processes of flotation. The REFLUX™ Flotation Cell offers the opportunity to achieve this goal within a single system, fundamentally by decoupling the water recovery and hence entrainment from the imposed gas flux. In this study, the flotation kinetics achieved using a batch mechanical cell were determined for a pure chalcopyrite feed less than 0.1 mm. These results were then used to assess the performance of the REFLUX™ Flotation Cell operated under continuous steady state conditions. A standardised flotation cell reference method was established based on the ratio of the product flux of the REFLUX™ Flotation Cell relative to the plug-flow equivalent result for a batch mechanical cell. This analysis, conducted as a function of the particle size, indicated a performance ratio of ∼3–20 fold. Moreover, the analysis provided insights into the effects of the operating conditions on the kinetics of the REFLUX™ Flotation Cell. This work was then extended to establish an assessment of the counter current washing achieved as a function of the particle size for when the pure chalcopyrite ore was combined with ultrafine silica.

Investigation of the gas-liquid-particle multi-phase hydrodynamics of Wemco flotation cells

Computational Fluid Dynamics (CFD) modelling of a 1.3 m3 flotation cell fitted with a Wemco 56 mechanism has been performed, backed up by experimental measurements. The flow field, gas dispersion and solids concentration in the flotation cell were studied. Both the PIV measurements and CFD modelling of the cell revealed that the rotor generated a jet stream towards the wall, which induced two strong vortices, one below the rotor level and the other extending from the rotor region to near the free surface. The strong downward flow along the wall of the tank turns horizontally passing underneath the false bottom and up through the draft tube. Inside the draft tube, an average axial velocity of about 0.7 m s−1 with a flow rate of 0.05 m3 s−1 was predicted, in good agreement with experiment. The void fraction was found to vary significantly with height in the cell. The maximum value of void fraction reached 0.55 near the froth interface in the air–water system. In the presence of solids, the air bubbles were able to penetrate further downwards to the bottom of the tank and the void fraction reached a maximum value of 0.35 near the froth interface. The Sauter mean bubble diameter was found to be in the range of 0.3–0.9 mm in the air–water system. The solids concentration was practically uniform throughout the tank except for the region near the surface. CFD simulation results for velocity, bubble size, void fraction and solids concentration are analysed in detail. CFD simulation was then carried out for an industrial-scale Wemco 225 cell (92 m3). Predictions are similar to those for the smaller Wemco 56, though there are differences in detail. Voidage predicted by CFD model of the Wemco 225 cell agrees with plant measurements.

Full-Scale trial of the REFLUX™ flotation cell

A 2 m diameter REFLUX™ Flotation Cell was fed at roughly 210 m3/h, equivalent to a flux of 1.9 cm/s, about twice the maximum rate used in conventional flotation cells. The coal feed slurry had 59–64 wt% head ash and nominal size range −0.100 mm (Sauter mean size 0.004 mm). The air, wash water and underflow rates were 180 m3/h, 65 m3/h and 235 m3/h respectively, giving a positive downwards wash water bias flux of 0.2 cm/s. Product ashes of 11–15 wt% were obtained at combustible recoveries of 58–75 %, with results on or better than the tree curve. These initial results demonstrate that the beneficial hydrodynamics seen at laboratory scale are realised at full-scale. Also demonstrated is the use of a novel oil-agglomeration technique to obtain detailed performance versus size data, showing that high hydrophobic recoveries were being obtained at sizes down to 0.001 mm.

Bioengineering of Halobacterium sp. NRC-1 gas vesicle nanoparticles with GvpC fusion protein produced in E. coli

Gas vesicle nanoparticles (GVNPs) are hollow, buoyant prokaryotic organelles used for cell flotation. GVNPs are encoded by a large gas vesicle protein (gvp) gene cluster in the haloarchaeon, Halobacterium sp. NRC-1, including one gene, gvpC, specifying a protein bound to the surface of the nanoparticles. Genetically engineered GVNPs in the Halobacterium sp. have been produced by fusion of foreign sequences to gvpC. To improve the versatility of the GVNP platform, we developed a method for displaying exogenously produced GvpC fusion proteins on the haloarchaeal nanoparticles. The streptococcal IgG-binding protein domain was fused at or near the C-terminus of GvpC, expressed and purified from E. coli, and shown to bind to wild-type GVNPs. The two fusion proteins, GvpC3GB and GvpC4GB, without or with a highly acidic GvpC C-terminal region, were found to be able to bind nanoparticles equally well. The GVNP-bound GvpC-IgG-binding fusion protein was also capable of binding to an enzyme-linked IgG-HRP complex which retained enzyme activity, demonstrating the hybrid system capability for display and delivery of protein complexes. This is the first report demonstrating functional binding of exogenously produced GvpC fusion proteins to wild-type haloarchaeal GVNPs which significantly expands the capability of the platform to produce bioengineered nanoparticles for biomedical applications.Key points • Haloarchaeal gas vesicle nanoparticles (GVNPs) constitute a versatile display system. • GvpC-streptococcal IgG-binding fusion proteins expressed in E. coli bind to GVNPs. • IgG-binding proteins displayed on floating GVNPs bind and display IgG-HRP complex. Graphical abstract

A Convolutional Neural Network for Classification of Froth Mobility in an Industrial Flotation Cell

ABSTRACT Froth flotation is widely used in the resource industry as a particle separation process. The performance of the flotation process is significantly affected by the mobility of the froth phase. Despite its importance, little work has been done to develop a simple and robust method for indicating froth mobility. In the present study, a simple method to monitor froth mobility was developed using a readily available web-camera to take images and a convolutional neural network (CNN) model classifying the images mainly based on the degree of motion blur. The CNN model was trained with a newly built froth image dataset, comprising froth images taken near the overflowing lip of an industrial flotation cell at a wide range of operating conditions using the web-camera. It was found that the trained model could correctly classify 98% of the froth images into one of three categories: low, medium, and high mobility. The froth mobility determined by the trained CNN model was in good agreement with the one analyzed with a commercial software. A potential application of the present method for indicating flotation performance was illustrated.

ASM-VoFDehaze: a real-time defogging method of zinc froth image

When the ambient temperature is low, a large amount of water mist and dust will inevitably appear around the zinc flotation cell, forming haze, which seriously affects the extraction of flotation froth image features. General defogging methods of natural image are difficult to obtain satisfactory results for such industrial haze image. Therefore, we propose a real-time defogging method based on ASM-VoFD (Atmospheric Scattering Model and the Variable-order Fractional Differential). First, the dark pixel ratio is used to detect fog in froth image, which solves the redundant calculation caused by unnecessary defogging operations. Second, the linear transformation of the atmospheric scattering model is used to calculate the initial transmission map, and the gaussian filter is used to optimize the initial transmittance, and the haze-free image is restored with atmospheric light estimation. Finally, a variable order fractional differential operator is used to enhance the edges and texture details of the restored froth image, which solves the problems of blurred edges and low contrast. The experiments show that the algorithm has a good defogging effect on the industrial images, enhance the edges of the image, and can be effectively implemented in O(N) time to meet the application requirements of real-time flotation monitoring.

CONTROLLING GRINDING PROCESS PARAMETERS USING CENTRAL COMPOSITE DESIGN TO REDUCE SLIMES IN PHOSPHATE ORE BENEFICIATION

Ultrafine particles resulting from the grinding operations of phosphate ore cause problems of air pollution, and of the beneficiation plants particularly, flotation cells and filtration units. Particles of less than 38 μm are one of the undesirable consequences of the phosphate ore beneficiation stage, where fine or ultrafine powder accounts for 10–30 percent of phosphate quantities and is regarded as a loss. Furthermore, maintaining additional amounts of phosphate by reducing these particles will provide several benefits, including minimizing the environmental implications of slime disposal and enhancing the economic impact of the phosphate ore beneficiation process. This paper aims to maximize the useful phosphate particles and reduce the slime instead of doing even more work with traditional techniques. This goal might be attained by increasing the percent of particles of the desired size of the phosphate (Target) during the grinding process by determining the optimal operational conditions, that will reduce the amount of slime. The central composite design (CCD) is used to identify the number of experiments to be evaluated and to create a predictive model to be used for determining the optimal operation parameters. As a result of the optimization process, a maximum Target of 87.6% was obtained at grinding conditions t (5.1 min), v (42.6%), s (81.2%), and c (50.7%). Where t, v, s, and c stand for grinding time, occupied volume of ball, rotational speed percent from critical speed (%) and solid concentration by volume (%) respectively.