Frother Concentration Research Articles

Study of froth behaviour in a controlled plant environment – Part 2: Effect of collector and frother concentration

An investigation into froth zone recovery in a controlled plant environment is presented. The effect of operating conditions on the froth performance is given in our previous work (Rahman et al., 2015). This paper is primarily concerned with the influence of chemical properties such as frother and collector concentration on the froth behaviour. The results suggested that increasing the collector concentration gave expected results in the collection (pulp) zone, with a significant increase in coarse particle recovery. However, at high collector concentrations, it was observed that there was an increase in bubble coalescence and froth instability as well as a slight decrease in froth recovery. Increasing frother concentration gave a significant improvement in froth recovery and a slight increase in the collection zone recovery was also found. This was attributed to the formation of finer, more stable, bubbles and a corresponding increase in froth stability. Size and grade analysis of the samples suggested that the dropback particles were mainly composite or middling fractions. It appeared that particles whose grade was higher than the feed may be collected into the froth zone, but some particles with grades lower than the concentrate may detach from the froth.

Automatic control of bubble size in a laboratory flotation column

Gas dispersion properties play an important role on determining the metallurgical performance of flotation processes. Indeed, bubble surface area flux (Sb) has been found to correlate with the collection zone flotation rate constant and is therefore a potential variable to regulate in order to achieve a target performance. Sb can be calculated as a combination of two other gas dispersion properties, namely, gas superficial velocity and the Sauter bubble mean diameter. This communication describes the design and implementation of a feedback control system for the Sauter bubble mean diameter in an attempt towards controlling Sb. In order to track changes on bubble size, the Sauter bubble mean diameter was derived from an adaptive bubble size probability density function (PDF). A Gaussian mixture model was used to represent the bubble size PDF and its parameters were updated on-line and in real-time by a dedicated computer from sequentially incoming images. To improve bubble size controllability, a frit-and-sleeve sparging device was installed. This device allows modifying bubble size by manipulating the water flow rate circulating through a sleeve surrounding a porous ring (shear water). A Wiener model is used to represent the dynamic relationship between the shear water flow rate and the Sauter bubble mean diameter. A nonlinear control, based on the internal model control (IMC) structure, was designed and implemented. Tracking and regulation performance against gas velocity and unmeasured frother concentration variations were then successfully evaluated in a two-phase system.

Prediction of Gas Holdup in a Flotation Column by Artificial Neural Network

Flotation column is one of the separation technologies investigated for removal of gangue mineral from coal fines. The effect of process variables, such as gas flow rate, feed flow rate, and frother dosage on gas holdup, were investigated. In this study, the measurement of gas holdup in presence of coal fines was carried out in a laboratory flotation column by a phase separation method. Detailed parametric study was performed to observe the effect of slurry concentration, gas flow rate, slurry flow rate, and frother concentration on gas holdup. An artificial neural network approach with three layers was systematically employed to predict gas holdup using some of the experimental results. The rest of the experimental results were successfully compared with the model predictions with less than 5% average error. In this work, emphasis was made on random selection of training data and small network. The developed trained network was also able to capture the non-linear prediction of gas holdup with new operating conditions that were not used in the training process and enhanced the physical understanding of the process.

Amenability Testing of Fine Coal Beneficiation Using Laboratory Flotation Column

The amenability of beneficiating a low rank coal has been studied using a laboratory CPT CoalPro flotation column. After review of the published literature various relationships between bubble size and superficial gas rate, bubble surface area flux and gas hold up and slip velocity and bubble size have been deduced in relation to the coal slurry and compared with relationships reported in the literature. A performance curve for the flotation column tested under the operating conditions revealed that the optimal size range of coal that yields optimal separation occurred in the size range 60­200 microns. Empirical relationships a) to estimate the gas hold up in terms of the measurable quantities, such as superficial gas and water flow rates and frother concentration and b) to predict the carrying capacity of particles of various sizes into the concentrate have been developed. Based on grade/recovery plots, the optimal separation that can be achieved for the given coal in a flotation column was found to be 85% combustible recovery with 81% ash rejection at the separation efficiency of 62% along with the corresponding operating conditions. Empirical relationships to predict the recovery of combustibles and ash rejection in terms of operating variables have also been proposed. [doi:10.2320/matertrans.M2014462]

Application of Statistical Analysis on the Bubble Surface Area Flux in a Column Flotation Cell

Flotation is a widely used separation process with applications from mineral separation to de-inking of recycled paper, waste water treatment, and solid remediation. In flotation column, bubble surface area flux (Sb) has been reported to describe the gas dispersion properties, and it has a strong correlation with the flotation rate constant. No information is available regarding Sb for coal flotation in column cell. This paper describes the effects of hydrodynamic parameters on Sb by means of a 23 factorial experimental design in designed flotation column using coal slurry. The results showed that Sb increased with increasing superficial gas velocity and frother concentration, but decreased with increasing solid concentration. The main and interaction effects of operating parameters on Sb were evaluated using Yates’ analysis. The statistical model was developed to predict Sb in column flotation cell using experimental data. This paper also presents the development of the statistical model and the validation using a number of additional data sets. There is a good agreement between experimental results and predicted results from the developed model.

Experiences in using gas dispersion measurements to evaluate metallurgical performance of scavenger cleaner and recleaner circuit at Vale’s Thompson Mill

The performance of a flotation circuit is largely the result of the operator’s response to visual clues. This includes manipulation of the gas input and how it is distributed to cells in a bank. A new gas dispersion technology was presented which was conducted to perform characterization tests in Outokumpu 30 m3 and 50 m3 flotation cells installed at Thompson Vale’s concentrator, and subsequent data analysis. The experimental program was designed to establish “as-found” baseline conditions for each cell of the two-parallel banks in the scavenger-cleaner and recleaner circuit, to select and characterize one typical cell in the two banks with either different frother concentrations or different air flow rates, and establish what variables can be manipulated in future characterization work. A three-parameter model was developed in order to link the bubble size and frother concentration. This relationship can be used to correlate gas dispersion change to improved metallurgical performance.

Nano-microbubble flotation of fine and ultrafine chalcopyrite particles

As is well known to mineral processing scientists and engineers, fine and ultrafine particles are difficult to float mainly due to the low bubble-particle collision efficiencies. Though many efforts have been made to improve flotation performance of fine and ultrafine particles, there is still much more to be done. In this paper, the effects of nano-microbubbles (nanobubbles and microbubbles) on the flotation of fine (−38+14.36μm) and ultrafine (−14.36+5μm) chalcopyrite particles were investigated in a laboratory scale Denver flotation cell. Nano-microbubbles were generated using a specially-designed nano-microbubble generator based on the cavitation phenomenon in Venturi tubes. In order to better understand the mechanisms of nano-microbubble enhanced froth flotation of fine and ultrafine chalcopyrite particles, the nano-microbubble size distribution, stability and the effect of frother concentration on nanobubble size were also studied by a laser diffraction method. Comparative flotation tests were performed in the presence and absence of nano-microbubbles to evaluate their impact on the fine and ultrafine chalcopyrite particle flotation recovery. According to the results, the mean size of nano-microbubbles increased over time, and decreased with increase of frother concentration. The laboratory-scale flotation test results indicated that flotation recovery of chalcopyrite fine and ultrafine particles increased by approximately 16–21% in the presence of nano-microbubbles, depending on operating conditions of the process. The presence of nano-microbubbles increased the recovery of ultrafine particles (−14.36+5μm) more than that of fine particles (−38+14.36μm). Another major advantage is that the use of nano-microbubbles reduced the collector and frother consumptions by up to 75% and 50%, respectively.

Correspondence of bubble size and frother partitioning in flotation

The size of bubbles created in the flotation process is of great importance to the efficiency of the mineral separation achieved. Meanwhile, it is believed that frother transport between phases is perhaps the most important reason for the interactive nature of the phenomena occurring in the bulk and froth phases in flotation, as frother adsorbed in the surface of rising bubbles is removed from the bulk phase and then released into the froth as a fraction of the bubbles burst. This causes the increased concentration in the froth compared to the bulk concentration, named as frother partitioning. Partitioning reflects the adsorption of frother on bubbles and how to influence bubble size is not known. There currently exists no such a topic aiming to link these two key parameters. To fill this vacancy, the correspondence between bubble size and frother partitioning was examined. Bubble size was measured by sampling-for-imaging (SFI) technique. Using total organic carbon (TOC) analysis to measure the frother partitioning between froth and bulk phases was determined. Measurements have shown, with no exceptions including four different frothers, higher frother concentration is in the bulk than in the froth. The results also show strong partitioning giving an increase in bubble size which implies there is a compelling relationship between these two, represented by C Froth/C Bulk and D 32. The C Froth/C Bulk and D 32 curves show similar exponential decay relationships as a function of added frother in the system, strongly suggesting that the frother concentration gradient between the bulk solution and the bubble interface is the driving force contributing to bubble size reduction.

Investigation of the Effects of Hydrodynamic Parameters on the Flotation Recovery of Coal Particles

The separation efficiency of the flotation process depends not only on differences in the physico-chemical surface properties of various minerals within an ore but also on the hydrodynamics of flotation. The aim of this article was to study the effects some fundamental hydrodynamic variables such as impeller speed on coarse particles flotation using a combination of factorial and one factor at a time experimental methods. As a function of impeller speed, the most important variable according to the factorial experiments, coarse-particle recovery increased with a Reynolds number around 119600, a Froude number of 1.53, and an air capacity number of 0.00346 and then decreased significantly due to the domination of the detachment mechanism in the process. Impeller clearance off-bottom was the second most important parameter and it was found that increasing impeller clearance off-bottom declined recovery as a result of decreasing the intensity of particle suspension. Frother concentration was the third most important parameter and the recovery increased by raising frother concentration up to 170 ppm, stayed steady between 170 to 200 ppm and then dropped. Also investigating the effects of solids showed that coarse coal recovery increases gradually by increasing solids concentration.

Effect of Fine Particles' Entrainment on Conventional and Column Flotation

The entrainment of particles in a flotation has been considered as one of the significant factors affecting both concentrate grade and recovery for a decades. It is based on the changes depending on the establishment of linear relationship between water recovery and solid recovery. In this study, entrainment of fine particle using a mixture of artificial ore (celestite:calcite; 1:1) was investigated in conventional and column flotation. The effects of frother concentration and particle size were tested. The results showed that the particle size and frother concentration had significant effect on the grade and recovery, flotation time, and fine gangue entrainment. Entrainment factors for the conventional and column flotation were compared. Kirjaveinen (1989) model was used for describing a specific entrained factor (P i ) of hydrophilic particles. It has been found that Kirjaveinen model supports the results of this study.

Boiling treatment of ABS and PS plastics for flotation separation

A new physical method, namely boiling treatment, was developed to aid flotation separation of acrylonitrile–butadiene–styrene (ABS) and polystyrene (PS) plastics. Boiling treatment was shown to be effective in producing a hydrophilic surface on ABS plastic. Fourier Transform Infrared analysis was conducted to investigate the mechanism of boiling treatment of ABS. Surface rearrangement of polymer may be responsible for surface change of boiling treated ABS, and the selective influence of boiling treatment on the floatability of boiling treated plastics may be attributed to the difference in the molecular mobility of polymer chains. The effects of flotation time, frother concentration and particle size on flotation behavior of simple plastic were investigated. Based on flotation behavior of simple plastic, flotation separation of boiling treatment ABS and PS with different particle sizes was achieved efficiently. The purity of ABS and PS was up to 99.78% and 95.80%, respectively; the recovery of ABS and PS was up to 95.81% and 99.82%, respectively. Boiling treatment promotes the industrial application of plastics flotation and facilitates plastic recycling.

A novel approach to prevent bubble coalescence during measurement of bubble size in flotation

Effect of frothers in preventing bubble coalescence during flotation of minerals has long been investigated. To evaluate the performance of a frother, an apparatus to measure the bubble size is a basic necessity. McGill Bubble Size Analyzer (MBSA) or bubble viewer that has been developed and completed by McGill University’s Mineral Processing Group during the last decade is a unique instrument to serve this purpose. Two parameters which are thought to influence the bubble size measurements by McGill bubble viewer include water quality and frother concentration in the chamber. Results show that there is no difference in Sauter mean (D32) when tap or de-ionized water was used instead of process water. However, the frother concentration, in this research DowFroth 250 (DF250), inside the chamber exhibited a pronounced effect on bubble size. Frother concentration below a certain point can not prevent coalescence inside the chamber and therefore caution must be taken in plant applications. It was also noted that the frother concentration which has been so far practiced in plant measurements (CCC75-CCC95) is high enough to prevent coalescence with the bubble viewer.

2<sup>k</sup> Factorial Experiments on Factors that Influence the Recovery of Gold during the Upgrade of Ilesha-Itagunmodi Gold Ore through Froth Flotation

A low-grade gold ore from Ilesha-Itagunmodi, south western Nigeria was panned, dried and ball-milled before sieving into fractions. The morphological, mineralogical and chemical composition was studied by optical micro-scopy (Reflected and Transmission), X-ray diffraction (XRD) and Energy Dispersive X-ray fluorescence (XRF), respectively. The sieved fractions were subjected to chemical analysis (AAS). The +106 μm sieve had the highest concentration of the mineral and was then selected for the upgrade through froth flotation using standard reagents. In this paper a report on a 2k factorial experiment that provides an understanding of the impact of operational variables on the quantity of gold mineral obtained from the ore during froth flotation is presented. Analysis results showed that Ilesha-Itagunmodi gold ore is non-refractory with fine grain particles, amenable to froth flotation and contained about 20 other associated minerals, gold had a concentration of about 0.0024%. A com-bination of P-Xanthate and amine glycol collectors at a pH of 9.2 only produced a considerable increase in gold yield. This translated to about 87.13% increase in recovery of gold from the ore. Analysis of variance (ANOVA) was carried out and the model equation obtained was subsequently optimised to obtain a model equation that could be used in predicting the recoverable quantity of gold, indicating that F11,1-values for Collector concentration, Frother concentration, pH and Conditioning time were 156.86, 6.96, 43.81, and 56.77 respectively. A model with an F value of 88.41 was obtained which indicated that the model was significant. The model equation obtained was subsequently optimised to be able to predict the recoverable quantity of gold. A “Pred R-Squared” value of 0.9365 (93.65%) was also obtained and is in reasonable agreement with the “Adj R-Squared” value of 0.9534 (95.34%). It was established that Ilesha placer gold ore is amenable to froth flotation using standard reagents.

Validity of critical coalescence concentration in dynamic conditions

The aim of the study was to confirm that the concept of the critical coalescence concentration (Cho and Laskowski, 2002) is only applicable to static conditions.A new experimental setup was developed. The experimental idea was to sample the same batch of bubbles at their formation point and later, during the bubble rise in static and dynamic conditions. The difference in the measured bubble size in the two sampling areas gives indication on the effect of frothers on bubble coalescence and breakup that takes place after the bubble creation due to the dynamic conditions.Three commercial frothers, DF200, NF240 and DF250, were tested in the experiments.In static conditions, the size of the forming and rising bubbles became equal at the frother concentration equal to the critical coalescence concentration (CCC) observed previously in mechanical flotation cell. On the other hand, in dynamic conditions, the size of rising bubbles was significantly larger than the size of freshly formed bubbles not only below the CCC as expected based on the literature. This finding confirms the hypothesis that the CCC is only applicable in static conditions, or in conditions where hydrodynamic forces do not contribute to bubble coalescence or breakup. The results showed that the frothers have a major effect on bubble size already at the early stage of bubble formation.

Optimization of Operating Parameters for the Selective Flotation of Heavy Metals from Contaminated Fine Sediment Using Response Surface Model

In this study, the effect of different flotation operating variables, such as pH, pulp density, collector concentration, impeller speed, frother concentration, and air flow rate, on selective flotation of heavy metals, especially Cu, from fine dredged sediment has been evaluated. Parameter optimization was done using the single parameter at a time method and response surface method (RSM) using Box-Behnken design and was assessed in terms of metal removal, metal recovery, metal concentration factor, and mass recovery. Among the operating variables studied, pulp pH, collector concentration, pulp density, and impeller speed were found to have significant effect on metal flotation selectivity. A validation study of the response surface model showed its aptness to predict the optimum values of operating parameters and their interactions on flotation responses which evaluate flotation performance. Flotation experiments under optimum operating parameters showed good flotation selectivity for Cu (3.3 ± 0.2) with a mass recovery of (mass of sediment in the froth) 14.1 ± 1 and Cu removal of 37.4 ± 3.6%.

Experimental investigation and modeling of flotation column for treatment of oily wastewater

A unique cyclonic static microbubble flotation column was developed for oily wastewater separation. The separation efficiency was found to be highly dependent on gas holdup and bubble size distribution. By changing the circulation pressure, gas flow rate, frother concentration, the effect of operation parameters on gas holdup and oil removal efficiency were attained. A mathematical modeling between the kinetic constant and the gas holdup was established for oily water separation process. The results show that higher gas holdup and smaller microbubble sizes are beneficial to improve oil removal efficiency.

Developing critical coalescence concentration curves for industrial process waters using dilution

Critical coalescence concentration (CCC) is commonly used to characterize frothers. The CCC is determined from a plot of Sauter mean bubble size (D32) vs. frother concentration, referred to here as the ‘addition’ method. Industrial flotation systems can encounter a number of naturally occurring surfactants and salts that also influence bubble size. In effect there is a ‘system’ CCC. This paper introduces a dilution method to identify the system CCC. The study verifies the dilution technique using the commercial frother DF-250. It is shown that the system CCC can be expressed as an equivalent DF-250 concentration to provide context and a means of comparing water samples. The viability of using gas holdup to provide an estimate of process water D32 is also explored. To illustrate the procedure three samples of process water from the Albian Sands bitumen processing plant were examined. They proved to be similar and yielded a system CCC equivalent to about 20ppm DF-250. It is concluded that the dilution and frother equivalent techniques can be used to help identify system hydrodynamic properties.

Influence of frothers on the detachment of galena particles from bubbles

This study aims to investigate the effect of frother type and concentration on the detachment of galena particles during the coalescence of a bubble pair. An experimental technique was used that allows the interaction between two individual air bubbles and measurement of particles that leave the surface as a result of the merging process. Two different frother types, OrePrep® F-549 a mixture of polyglycols and methyl isobutyl carbinol (MIBC), were used in the study. The results showed that the presence of frothers has a significant effect on the number of hydrophobic particles detaching from the surface of the oscillating bubble. In general, it was found that there is a linear correlation between the percentage of particles leaving the surface and the frother concentration. The F-549 frother was found to be more effective compared to MIBC, as it provided more damping to the oscillating bubble. It was also observed that the presence of particles on the bubble significantly damped the oscillation, resulting in less adhering particles to drop off the bubble surface. A force analysis was conducted to establish a possible link between the detachment forces that arose from the bubble oscillation and frother concentration.

Optimization of the performance of the hydrodynamic parameters on the flotation performance of coarse coal particles using design expert (DX8) software

Hydrodynamic parameters play an important role in flotation efficiency. In the present work, the effects of some key hydrodynamic factors such as impeller speed (600, 700rpm), impeller off-bottom clearance (0.3H, 0.4H), solids percent (12%, 14%), frother type (Pine oil and methyl isobutyl carbinol (MIBC)) and their concentrations (140, 170ppm) on the flotation performance of coarse coal particles were investigated using factorial experimental design. The DX8 software was used to analyze the results of the experiments. According to DX8 software, it is concluded that until 700rpm, the effects of the studied parameters follow the order: impeller off-bottom clearance>impeller rotational speed>frother concentration>the interaction between impeller off-bottom clearance and impeller speed. But for higher impeller speeds, the impeller rotational speed has the most effects. The positive effect of impeller speed before 700rpm (i.e. 97397.38<Re<119589.22, 1.21<Fr<1.53 and 0.0035<Ca<0.0038 for 0.01226<μp<0.01299) and its negative effect beyond (i.e. Re>113609.61, Fr>1.53 and 0.0033<Ca<0.0035 for μp=0.01299) concluded that the optimum value for impeller speed is 700rpm. Also, it was concluded that the recovery of coarse coal particles is increased by increasing pulp solids percent because of increasing medium viscosity.

Flotation of a refuse tailing fine coal slurry

The flotation process performance of a refuse tailing fine coal slurry sample from a Colombian washing coal plant was studied using a mechanical flotation technique. Flotation parameters investigated included dosage of frother methyl-isobutyl-carbinol (MIBC) and collector (kerosene), as well as scrubbing time for the mechanical flotation cell. Flotation kinetics was also studied in the mechanical flotation cell. The results showed that the refuse tailing fine coal slurry was very straightforward to upgrade by flotation. Flotation yield of 45% (dry basis, db), combustible recovery of 92%, product ash of 20%, db and separation efficiency of 79% were obtained when MIBC was used as frother and kerosene as collector. Those results are in agreement with those obtained in the kinetics study, where the best operation condition was using a collector concentration of 2lb/t and a frother concentration of 30ppm of MIBC, which produced the highest flotation rate constant of 0.9457min−1.