Froth Recovery Research Articles

Challenges in flotation scale-up: The impact of flotation kinetics and froth transport

At present, data from industrial flotation operations is still limited and more tests and in-depth studies are required to improve the experimental procedures, measurement devices and analysis, to validate and interpret scale-up factors from batch to plant flotation operations.The new methodologies have contributed to improve predictions of flotation metallurgical performance using more refined scale-up methods, for example, analyzing the scale-up factor by size and liberation classes. These will allow for selecting the best equipment for each mineral and flotation stage (rougher, cleaner and scavenger).In this work, the effect of the pulp zone hydrodynamics affecting the collection residence time and flotation kinetics, and the froth transport, on the overall scale-up factors (typically around 1.8–2.3) was evaluated per particle size classes in the range of 22.5 to 300 µm. Two effects were found that partially explain the scale-up factor in the pulp zone, such as the pulp mixing regime (4–16%) depending on the cells number, and the solids segregation (2–7%) that decreases the residence time of larger particles. However, the most important contribution was the froth transport characteristics that determines the froth recovery which accounted for 48–58% of the scale-up factor, also increasing with particle size. In addition, it was found that the remaining percentage of the overall scale-up factor, around 31%, includes the uncertainty in the collection residence time estimation, which is lower than the effective pulp residence time, and the larger residence time of bubbles in industrial cells. Both effects hinder the identification of the actual flotation rate in the pulp zone.

An improved model for predicting froth recovery

In froth flotation, froth recovery is a key factor as it quantifies the effect that the froth has on the overall cell recovery. Froth recovery is affected by a number of variables, including froth stability, particle size and density, and the operating conditions of the flotation cell. Despite its importance, modelling froth recovery is challenging due to the large number of competing effects involved. In this paper, we present a model for froth recovery that takes into account the effects of detachment and subsequent transport of particles. The model is phenomenological and is derived from a set of coupled partial differential equations used to describe both liquid and particle motion within a froth. An analytical algebraic solution is obtained for the froth recovery by making a number of assumptions, which are discussed and justified in the paper. This model is related to a previous model produced by the authors, in which froth recovery was described in terms of a constant particle detachment fraction. Conversely, this enhanced model includes an improved description for particle detachment behaviour during coalescence events, allowing for a variable particle detachment fraction. The key parameters in the model are two dimensionless groups. The first group combines the particle settling velocity, the air addition rate and froth stability parameters such as air recovery and the change in bubble size over the froth, while the second key dimensionless group is the ratio of the surface loading on the incoming bubbles to the maximum surface loading. This model is compared to experimental results and is shown to accurately describe the evolution of the froth recovery behaviour down a bank of cells in response to the decreasing froth stability.

Decoupling the pulp and froth effect of ultrafine particles on Itabirite iron ore flotation

The reverse flotation of Itabirite iron ore is typically performed after a desliming step in which most of the sub-10 µm particles are removed. This is done to limit processing problems such as poor flotation recovery of SiO2 due to slime coatings, increased slurry viscosities, unmanageable froths and increased losses of hematite particles due to entrainment. However, the rejection of ultrafine particles contributes to large losses in iron recovery and may contribute to the instability of tailings dams. The aim of this study is to decouple the effects of ultrafine particles in the pulp and froth phases to better understand the processing capabilities of the fines fraction. The flotation test work was performed in a special-purpose continuously operated laboratory flotation cell that has a deep froth section to simulate plant-scale froth conditions. Five conditions of fines addition were investigated at 3 different froth heights and a solids concentration of 50%. The behaviour of the pulp and the froth were decoupled using froth stability and froth recovery tests. This showed that, even though there is an exponential increase in froth stability at increasing fines quantities, the performance of the pulp has the overriding effect on the SiO2 recovery. Pulp zone, froth zone and overall SiO2 recoveries showed that recoveries increased by about 3.6% for every 1% decrease in fines content. This meant a large increase of 20% in SiO2 recovery when going from undeslimed to deslimed feed. This was driven largely by increases in the pulp zone recoveries, which were about 4% for every 1% decrease in fines content. The froth recoveries, on the other hand, decreased by between 0.75% and 2.5% for every 1% decrease in fines content, depending on froth height. This paper explores further insights into iron ore flotation processing at different slimes concentrations.

Effects of a cyclonic microbubble flotation column operating parameters on coal process responses

ABSTRACT Processing fine and ultrafine coal particles from primary resources is essential for sustainable development. As one of the most recently developed enrichment equipment, cyclonic microbubble flotation columns (FCMC) showed high efficiency in upgrading various fine minerals. However, understanding the effect of FCMC operating variables on coal upgrading process responses remains a black box and needs fundamental assessments. To fill the gap, this study examined the influence of circulating pump pressure and froth height on the recovery of different coal particle size ranges to assess and explore fundamental FCMC performance. The experimental results established that increased froth height would simultaneously reduce the collection and froth recovery. Coarse particles in the high froth height were detached due to bubble coalescence or rupture, while the liquid drainage reduced fine particle pollution of froth products. Increasing circulating pump pressure would increase the collection zone’s turbulence, lead to coarse particle detachment, and reduce collection recovery. Meanwhile, increasing circulating pump pressure could promote froth stability and decrease froth detachment in the froth zone. The calculated first-order rate constant (k c) confirmed that the flotation rate constants of coarse (−0.5 + 0.25 mm) and fine (−0.074 mm) particles were low, while the intermediate particles (−0.125 + 0.074 mm) had faster flotation kinetics.

Size-by-Liberation Characterisation of an Industrial Flotation Bank in Rougher and Cleaner–Scavenger Operation

The flotation process characterization is typically based on the mineral properties and related to the feed particle size. Laboratory testing allows for the evaluation of the batch flotation kinetics, while plant surveys are carried out for the plant evaluation, and sometimes the rougher flotation stage is also characterized by kinetics, considering either the full sampling of the circuit or the short-cut method. Comparisons of plant and batch results are useful for identifying the scale-up factors. The kinetic evaluation of cleaner stages is less common in plant surveys, and usually, only the overall cleaner and scavenger results are reported. This condition limits a more comprehensive understanding of these stages, which have significant differences from the rougher operation. In this study, the effect of main operating variables in cleaner and scavenger stages, such as finer particle size, higher mass recoveries, higher liberation, particles entrainment, froth recoveries, mineral grades, froth depth, gas rate, and others, was analysed by using an industrial simulation tool that was built from a wide industrial database. For this purpose, data from plant kinetic surveys was used to characterize the mineral feed entering the cleaner–scavenger stage, which allowed for calibrating the simulation tool and predicting the overall circuit performance. The metallurgical results of the cleaner–scavenger bank were compared with those when the bank was operating at a rougher stage (previous operation). The results allowed for evaluating the differences in metallurgical results of the cleaner–scavenger and rougher banks, mainly related to the differences in particle size and liberation as well as in the mass flowrate of collected particles, which affects bubble loading and consequently froth stability, that in turns impacts on froth recovery. The operating conditions and mineral characteristics of each stage also impacted the water recovery and gangue entrainment along the banks. The comparison of predicted recoveries and grades in rougher, cleaner, and scavenger stages showed a good agreement with plant data. These results validated the simulation tool, which is useful and flexible enough to characterize different stages, predict performance and explore new operating conditions.

The Impact of Froth Launders Design in an Industrial Flotation Bank Using Novel Metallurgical and Hydrodynamic Models

In flotation cells, especially in large flotation units, froth management is a crucial variable that should be considered during the design phase or optimized to improve the performance of existing flotation circuits. This paper presents a simulation evaluation of the effect of launder design on the metallurgical performance of an industrial flotation circuit consisting of five TankCell® e630 (630 m3) cells in a Cu rougher duty. This analysis was carried out using a new industrial simulator that includes novel metallurgical and hydrodynamic models, developed from a wide database collected from many industrial concentrators. This tool is currently incorporated into HSC Chemistry® software and allows evaluating the effect of launder design on mineral froth recovery, water recovery, entrainment, and other variables. The industrial flotation circuit was evaluated under different launder design scenarios, considering an actual flotation circuit that includes TankCell® e630 cells for calibration and as a reference (baseline). Firstly, two different designs were evaluated in the full circuit: a standard launder design and a new launder technology. It was found that the new launder technology enabled improvement of the mineral recovery along the circuit, mainly for coarse particles, due to the improvement in froth mineral recovery. Next, a partial upgrade of the launder design along the circuit was analysed. Thus, the new launder technology was evaluated in the first and the last two cells of the bank. The results showed that upgrading the launders in different cells along the circuit delivered an increase in the final recovery with respect to the baseline, with a partial impact on the concentrate grade. However, these changes are less than those when evaluating the full upgrade scenario. A partial launder upgrade either in the first or last two cells of the bank showed similar final recoveries, but the latter enabled a slightly higher concentrate grade (about 1% higher) to be achieved. Finally, the evaluation of launder design using the industrial simulator made it possible to estimate its effect on variables that are not commonly obtained from plant surveys, including superficial gas rates at the froth surface level, froth recovery per particle size, collection recovery per particle size and liberation, gangue entrainment, and bubble loading grade.

Limiting conditions in large flotation cells: Froth recovery and bubble loading

In recent decades, the exponential increase in the cell volume of flotation cells has promoted significant advantages, such as those related to investment costs, footprints, and energy savings. In larger cells, the diameter/height ratios and froth transport distances increase. Thus, the use of froth crowders and internal launders becomes compulsory for maintaining froth transport distances while decreasing the ratio between the gas and collected mineral flow rates. Consequently, the bubble load will increase until reaching a critical bubble surface coverage.In this paper, the concentrate carrying rate (tph/m2) was described in terms of the bubble surface coverage (bubble loading) at the pulp-froth interface and the froth recovery (froth transport) and was evaluated as a function of the cell volume and operating variables. A sensitivity analysis based on industrial operating and design conditions, such as the superficial gas rate, particle size, froth cross-sectional area and cell volume, was developed to evaluate the metallurgical performance of cells with volumes ranging from 100 to 630 m3.The results show that carrying rate limitations can arise for the whole range of cell volumes depending on the critical operating conditions, particularly for the first rougher cells and in the cleaning stages of industrial flotation circuits. An increase in cell volume consistently increases the bubble loading (bubble surface coverage) under all conditions, approaching the limiting conditions more rapidly for cells without internal launders. Otherwise, the limiting condition was achieved when the particle size DPS decreased from 50 to 20 µm and for two separate conditions of superficial gas rate: high (much higher than 1 cm/s) and low (much lower than 1 cm/s). The minimum bubble surface coverage was observed around JG = 1 cm/s, which corresponds to the maximum bubble surface area flux, independent of the cell size.The use of internal launders increases the range of operating conditions without exceeding the maximum bubble loading.

Effect of peracetic acid as a depressant on the flotation separation of chalcopyrite from arsenopyrite

• Separation of arsenopyrite from chalcopyrite hindered by similar floatabilities. • Depression of arsenopyrite flotation required for better separation. • Effect of peracetic acid as a depressant of arsenopyrite was investigated in this study. • Found to greatly aid in flotation separation under neutral pH conditions. Arsenopyrite is an arsenic-bearing mineral that frequently occurs with chalcopyrite in polymetallic sulphide deposits. Their separation via existing methods and reagents involved in the flotation process, however, remains sub-par due to difficulties in the effective depression of arsenopyrite. In this study, the eco-friendly organic oxidant of peracetic acid (PAA, CH 3 C( O)OOH) was used for the first time ever to effectively depress arsenopyrite under conditions of neutral pH. Flotation experiments, adsorption tests, zeta potential analysis, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) were performed to investigate the depression mechanism of PAA on arsenopyrite. Single mineral flotation results showed PAA to have a massive depressive effect on arsenopyrite, reducing its froth recovery from 90% to 3% but only marginally affecting the froth recovery of chalcopyrite. Mixed minerals and bench-scale flotation tests further verified that PAA was an efficient arsenopyrite depressant. Adsorption test results, meanwhile, indicated that PAA could significantly reduce the adsorption of xanthate on the surface of arsenopyrite, but not on that of chalcopyrite. Zeta potential measurements, on the other hand, suggested a strong interaction between the surface of arsenopyrite and PAA compared with chalcopyrite, which induced a positive shift of zeta potential on the arsenopyrite surface. XPS analysis demonstrated that PAA only slightly oxidizes the surface of chalcopyrite, and a very small amount of iron oxide, sulfur oxide and copper oxide were generated, indicating that the surface was still hydrophobic. On the contrary, PAA could strongly oxidize the surface of arsenopyrite and generate a large number of oxygen-containing species, such as As(III)–O, As(V) − O, Fe(III) − O, Fe(III)–SO, SO 3 2− , and SO 4 2− . This was supported by measuring the contents of these oxides of iron, sulphur, and arsenic on the surface of arsenopyrite, which were found to increase from 47.13% to 88.56%, 14.95% to 45.49%, and 45.94% to 81.57%, respectively. Finally, hydrophilic oxide films containing AsO 2 − , AsO 3 − , SO 3 2− , Fe(OH) 3 , FeAsO 4 , and Fe 2 (SO 4 ) 3 were formed on the arsenopyrite surface, which further contributed to its depression.

A dynamic flotation model for predictive control incorporating froth physics. Part I: Model development

It is widely accepted that the implementation of model-based predictive controllers (MPC) ensures optimal operation if an accurate model of the process is available. In the case of froth flotation, modelling for control purposes is a challenging task due to inherent process instabilities. Most models for control have only focused on the pulp phase rather than the froth phase, which is usually oversimplified or even neglected. Despite the fact that froth stability can significantly affect the overall performance of flotation cells, there is still a gap in literature regarding flotation models for control purposes that properly include froth physics.In this paper we describe the development of a dynamic flotation model suitable for model predictive control, incorporating equations that describe the physics of flotation froths. Unlike other flotation models for control in the literature, the model proposed here includes important variables related to froth stability, such as bursting rate and air recovery, as well as simplified equations to calculate froth recovery and entrainment. These model equations allow estimating the amount of valuable material reporting to the concentrate, which can be used as a proxy to estimate grade and recovery. Additionally, pulp-froth interface physics was also included in our model, which enables a more accurate prediction of relevant flotation variables.A sensitivity analysis of the parameters showed that two out of seven parameters were highly sensitive. The highly sensitive parameters are the exponential factor n of the equation for the overflowing bubble size, and the constant value a of the equation for the bursting rate. Although the other parameters showed a reasonably lower sensitivity than n and a, the results also revealed that there is a significant difference in the prediction accuracy if the parameters are poorly estimated. Further simulations of important variables for control exhibited a good adaptability to changes in typical variables, such as air and feed flowrates.An analysis of degrees of freedom of the model established that two variables need to be fixed to have a completely determined system. This means that two variables are available for control purposes, which can be air and tailings flowrates (through the manipulation of the respective control valves). This study therefore paves the way for the implementation of a robust dynamic model for flotation predictive control, incorporating important froth phenomena.

اندازه گیری پایداری کف در سلول فلوتاسیون و بررسی تاثیر عوامل موثر بر آن

In this study, the froth stability for flotation of sulfide ores of iron ore concentrate was determined using the froth stability column and the effect of superficial gas velocity, collector dosage, frother dosage, and sample particle size (d50) on stability were investigated. Therefore, the effect of the parameters on the froth formation and Froth decay was determined according to the froth retention time (or the maximum froth height) and the froth half-life time The results showed that increasing the superficial gas velocity, collector dosage and frother dosage builder has a positive effect on froth stability, so that with increasing frother dosage from 60 to 140 gr/L, froth retention time and froth half-life time Increased by 92 and 71%, respectively. The sample particle size behaved differently in froth formation and decay, so that with d50 reduction, the maximum froth height increased but the froth half-life time decreased. Froth recovery was calculated according to the test conditions at different heights, and since the froth recovery was calculated based on the maximum froth height, the effect of the parameters expressed on the froth recovery was similar to the froth formation (maximum froth height). The results showed that the superficial gas velocity had the greatest effect and the collector dosage had the least effect on froth recovery. Also, froth recovery decreases sharply with increasing froth height, so that the average froth recovery in 30 experiments performed at 10 cm was 31%, while at 15 cm it was about 14%.

Effects of Operating Parameters on the Froth and Collection Zone Recovery in Flotation: An Industrial Case Study in a 10 m3 Cell

The effects of flotation operation parameters, including froth depth, air flowrate, and frother dosage, on the froth and collection zone recovery and the flowrate of particles into the froth phase were investigated in a 10 m3 industrial cell. The results showed that froth recovery increases upon increasing air flowrate and frother dosage, as well as reducing froth depth. While all tested parameters affected the particles that entered into the froth phase, air flowrate and frother dosage showed the most and least significance, respectively. When the air flowrate, frother dosage, and froth depth were 146 m3/h, 150 mL/min, and 5 cm, respectively, froth recovery was found to be above 84%. Also, the effect of the parameters studied on collection zone recovery was different from their effect on the froth zone, with air flowrate having the greatest impact on the former.

Flotation classification in closed-circuit grinding as a way of reducing sulphide ore overgrinding

Research object and aim. Flotation classification in closed-circuit grinding is a way of improving copper ore flotation indicators by reducing minerals overgrinding. Due to valuable components froth recovery with their uncovering in the process of grinding, loss of copper in flotation tailings with secondary slime are reduced significantly. The research aims to study the possibility to improve the flotation of copper ore based on the use of flotation classification in the closed-circuit grinding. Methodology. In order to solve the problem, laboratory studies on closed-circuit grinding experimental modeling were carried out in a mode with and without flotation classification of hydraulic classification discharge. In each grinding mode, five stages of closed-cycle simulation have been implemented. Flotation classification was carried out in froth flotation modes with froth treatment with and without the tapered chute. According to experimental results, the loss of copper has been determined with slime in hydraulic classification discharge and flotation classification, and flotation classification end-product balance was calculated when operating in the closed-circuit grinding. Summary. The obtained experimental data prove the possibility of improving copper ore flotation by reducing minerals overgrinding in the course of flotation classification in closed-circuit grinding. The technology of flotation classification with froth treatment in tapered chutes make it possible to obtain prime concentrate with 18% copper mass fraction when extracting 37.7% copper into it, and final tailings in flotation classification discharge with 0.13% copper mass fraction under 2% loss.

Causal model of an industrial platinum flotation circuit

Models of flotation found in literature are generally complex and reliant on manual surveys and laboratory data. Furthermore, these models do not usually indicate the causal relationships from true process independent variables to process outputs such as individual cell recovery and metal grade. These models are often found to be suitable for design but less applicable to the simulation of an industrial plant to perform offline control and optimization studies. This study explains these relationships from the individual cell inputs, level and air valves, to cell hydrodynamics and ultimately mass produced, recovery and grade. A technique is proposed to derive individual cell froth recovery by adjusting one froth stability parameter across the entire bank. The model is trained on an industrial platinum concentrator using predominantly online plant data and the model predictions are compared to real plant data over a period of a month.

Effects of flotation operational parameters on froth stability and froth recovery

SYNOPSIS The effect of flotation operational parameters on froth stability and froth recovery was studied. Froth stability was measured using a special column. To determine the froth recovery, the froth height change model and froth height exponential model were used. It was found that since the interactions between the pulp and froth zones affect the time of froth formation, the exponential model is more suitable than the froth height change method for determining the froth recovery. The results showed that superficial air velocity and collector dosage have, respectively, the highest and lowest effect on the froth recovery, while froth recovery decreases sharply with increasing froth height. Keywords: froth stability, froth recovery, superficial air velocity, collector dosage, frother dosage.

Effect of aggloflotation of coal slimes by use Flomin C9606 as a collector

In many coal preparation concentrators, coal slimes form the major challenge due to difficulties in its processing and upgrading. Several techniques are currently being devised in coal industries to aid in beneficiation of the coals in their finer sizes. Ultra-fine coal particles are exclusively processed by oil agglomeration, selective flocculation or hydrophobic flocculation flotation techniques. In this research, the focus is on hydrophobic flocculation flotation to clean ultrafine coal particles. Collector dosage, agitation stirring speed and grinding fineness batch tests were conducted, followed by flocculation and froth flotation. The results showed that optimum collector dosage (Flomin C9606) was 10 kgs/ton, the impeller speed 1,500 rpm and 30 minutes achieved the best grinding fineness. Two stage flow sheet produced froth recovery of 86.28% and ash content was 6.39%. It was therefore concluded that Flomin C9606, as a collector, was capable of obtaining clean coal product from these results.

A phenomenological model of entrainment and froth recovery for interpreting laboratory flotation kinetics tests

There is currently no standard approach to laboratory flotation testing and interpretation. The deficiency stems, in part, from the difficulties in quantifying the recovery of mineral particles by hydraulic entrainment (Re) and the recovery of collected mineral particles across the froth zone (Rf) of a laboratory flotation cell. For lack of alternatives, most practitioners ignore entrainment (Re = 0) and assume that froth recovery is 100% (Rf = 1). Consequently, differences in test scraping frequency or froth characteristics can lead to large differences in the inferred collection kinetics.This paper proposes resolving the problem by incorporating a phenomenological solution for Re and Rf. By considering the test water balance, incorporating hindered settling theory, and making some simple assumptions regarding the pulp, interface, and froth phases, it can be shown that the entrainment recovery of any mineral can be calculated solely from the particle size and specific gravity. A similar approach can be used to estimate the froth recovery as a function of time.The method is applied to a data set of flotation tests conducted with different scraping rates, and it is demonstrated that it yields similar flotation rate constants regardless of the scraping rate.

Impulse energy inputs to modify subsurface structure and functions and process properties of calcium-bearing minerals

Using Hammett indicators, X-ray fluorescence spectroscopy and atomic force microscopy, the authors analyze influence of high-voltage nanosecond impulses on structure and chemistry of surface and on process properties of calcium-bearing minerals. As a result of impulse energy inputs for t ≤ 30 s, the change in the structure and functions of mineral surface includes: enhancement of electron–donor capacity and formation of structural defects on the surface of fluorite, and enhancement of acceptor capacity of the surface of calcite and scheelite. Pre-treatment of mono-mineral samples by electrical impulses increases flotation ability of calcium-bearing minerals: increment in froth recovery makes 10–12% for scheelite, 5–6% for fluorite and 7–8% for calcite.

The effect of cell hydrodynamics on flotation performance

It is clear that along with gas dispersion characteristics, the energy dissipated by the impeller is process determining in flotation, and its effect on flotation kinetics has been widely studied. However, turbulent conditions inside a flotation cell have usually only been changed by varying impeller speed or air flowrate or both. Therefore, there is a need to investigate not only these variables but also how changes in impeller/stator mechanism size and design, cell aspect ratio and cell design affect turbulence. This should lead to a better understanding of the effect of cell hydrodynamics on flotation performance. The aim of this work was to evaluate the role of flotation cell hydrodynamics on flotation performance in a fully instrumented 3m3 cell. The cell was operated at a copper concentrator in Australia with different combinations of airflow rates, impeller speeds and sizes and cell aspect ratio providing a wide range of hydrodynamic conditions. An analysis of the flotation cell performance showed that the overall copper recoveries were very similar for the conditions tested. However, by decoupling pulp effects from froth effects it was possible to determine whether the changes made affected the pulp zone and/or froth zone responses. The analysis showed that the overall recovery had the potential to be up to 10% higher if not limited by froth recovery. Comparing the metallurgical performance of the cell with the different hydrodynamic conditions it was found that the collection zone flotation rate was not directly related to overall energy dissipation, as is commonly observed at laboratory scale, where energy is usually only changed by varying impeller tip speed. Results suggest that it is the size of the turbulent zone, rather than just energy input, that affects flotation recovery.

Flotation frother mixtures: Decoupling the sub-processes of froth stability, froth recovery and entrainment

The flotation process consists of two distinct phases: the pulp and froth phase. One of the main roles of the froth phase is to create a suitable environment for the separation of floatable, valuable minerals from non-selectively recovered, entrained gangue minerals. As a result the froth phase plays a significant role in the metallurgical performance of industrial flotation cells. Froth stability is important for the recovery of valuable minerals. However, a stable froth may contribute to increased entrainment and, consequently, a lower grade.This study compares the effect of frother mixtures with that of their single component frothers on the froth stability, froth recovery and entrainment of a platinum-bearing UG2 ore using polyglycol and alcohol frothers. The study showed that frother mixtures resulted in a greater froth stability than either of their component frothers. The increased froth stability was reflected in increased froth recoveries and greater overall recoveries. However, the important aspect in the use of frother blends was that they altered the froth structure and resulted in a lower degree of entrainment. This, together with the increased recovery, resulted in higher grades of valuable mineral recovered to the concentrate when using the frother mixtures.

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.