Froth Characteristics Research Articles

Diesel oil removal from water by froth flotation under low interfacial tension and colloidal gas aphron conditions

The objective of this work was to investigate the relationship between the froth characteristics, the system interfacial tension (IFT), and the efficiency of diesel oil removal by froth flotation under colloidal gas aphron (CGA) conditions. Branched alcohol propoxylate sulfate sodium salt (C 14–15(PO) 5SO 4Na) as an extended surfactant, was used to form CGA and microemulsions with diesel oil. For the CGA studies, the effects of salinity, surfactant concentration, stirring speed, and stirring time were investigated in order to determine the optimum conditions of the CGA formation which were further used for the froth flotation experiments. The air bubble size measurement was carried out in order to correlate the air bubble size to the froth flotation performance. The results showed that the use of CGA enhanced the process performance of froth flotation in terms of both the removal and the enrichment ratio of diesel oil since CGA increased both froth formation and stability. The froth flotation column which was operated at an air flow rate of 0.30 l/min with the feed solution prepared under non-equilibrium and the CGA conditions at 0.1 wt.% C 14–15(PO) 5SO 4Na, 3 wt.% NaCl, with a stirring speed of 5000 rpm and a stirring time of 5 min, gave the highest oil removal of 97%.

Cronstedt’s zeolite

Abstract Axel F. Cronstedt (1722–1765), famous Swedish mineralogist, was the first scientist to describe, 250 years ago, the distinctive property of zeolites, i.e., the unique frothing characteristics when heated in a blow-pipe flame. Cronstedt examined two specimens: one from Svappavaara in Northern Sweden and one that was said to come generically from Iceland. From Cronstedt’s indications, the occurrence of the first specimen was near the mining area of Kiruna. The morphological characteristics of the specimen suggested that the zeolite species is stilbite which would make it the first discovered zeolite mineral. This paper is devoted to the description of the structure and microstructure of that first discovered natural zeolite from Svappavaara (Northern Sweden). The SEM investigation of all the sample rock cavities filled with the zeolite crystals and the optical observation of the separated zeolite crystals revealed that the sample is mainly composed of stellerite with subordinate stilbite crystals which are present only in a few cavities together with stellerite. The chemical formula of the stellerite crystals derived from the EPMA and TG analyses is (Ca4.03Mg0.01Na0.03K0.11) [Si27.81Al8.19O72]·28.6H2O. The results of the structure refinement confirm that the investigated specimen is actually stellerite and evidenced no ordering in the tetrahedral sites. The structure refinement evidenced no ordering in the tetrahedral sites. The extraframework cation Ca is located in the centre of the main channel parallel to the a axis, on the mirror plane and is surrounded by water molecules with no contact with framework oxygen atoms. The coordination of Ca is 6-fold. A number of short water–water distances are possible by considering the different possible schemes around the Ca atom. Considering the short water–water distances and the partial occupancy of water sites, a number of octahedral coordinations around Ca are possible.

Frothability characterization of residual organic solvents

Organic solvents were evaluated through the determination of froth volume and bubble collapse rate in a froth column meter under various solvent dosages and aeration rate levels. There is a non-linear relationship between the froth volume and the gas flow rate for polyglycol ether type solvents. It is inappropriate to apply the concept of linearity retention time to describe the frothing characteristics of polyglycol ethers. Two new parameters are derived to characterize the foam stability and non-persistency of the frothers. The new parameters are initial dynamic froth index (IDFI) and initial dynamic froth collapse rate (IDCR). IDFI represents the froth volume formation properties, and can be used to relate to the ultimate recovery, Rm, and the flotation rate constant, K. IDCR describes the non-persistency of the froth, and can be used to relate to the quality of flotation concentrates. IDFI value depends on chemical structure and molecular weight of a solvent. Increasing solvent molecular weight and number of hydrophobic groups increases the IDFI value. Both ultimate recovery and flotation rate constant can be maintained at a desirable level, if the solvent dosage is applied in the amount to give the same product value of IDFI and solvent dosage. The selection of potential frothers from solvents tested is made by using IDFI and IDCR and comparing with laboratory fine coal flotation performance.

Comparative real-time characterization of frother bubble thin films

Methylisobutyl carbinol (MIBC) and methoxy polypropylene glycol (Dowfroth 250) bubble thin films were characterized by composition and thickness determinations, using FT-IR spectroscopy and UV–visible spectrophotometry, respectively. The infrared investigation indicates that the role of frother molecules in creating bubble thin films is based on their effectiveness in inducing H-bonding reorganization of the surrounding free water molecules into a coherent network. From UV–visible interference patterns, it is found that MIBC forms films with a measured critical end thickness of less than 160 nm, compared to 612 ± 30 nm for Dowfroth 250. The observed values of the free water layer thickness are comparable at 5.65 ± 0.28 μm for MIBC and 6.75 ± 0.34 μm for Dowfroth 250. A higher stability of an MIBC bubble over a Dowfroth 250 bubble is related to the different polarization and orientation of the molecules sustaining the boundary surface water network. The findings are used to explain the different action and associated froth characteristics of the two common industrial frothing agents.

Improving froth characteristics and flotation recovery of phosphate ores with nonionic surfactants

The beneficial effect of a series of nonylphenol polyethylene glycol ether surfactants were tested in the flotation of phosphate ores in which the mixtures of sodium oleate and dodecane were used as collectors. In order to elucidate the flotation results, equilibrium surface tension of single and binary surfactant solutions prepared with sodium oleate and nonionic surfactants were investigated. Synergism between surfactants was determined by observing the change in surface tension of solutions and by the calculation of interaction parameter from surface tension data. The lowering of surface tension of sodium oleate solutions was observed in the presence of nonionic surfactants. The interaction parameter between sodium oleate and a nonionic surfactant (i.e., NP-4) was calculated to be −0.21, showing attraction between the two surfactant molecules. The nonionic surfactant NP-4 was then tested in batch flotation of phosphate ores. The beneficial effect of nonionic surfactant was obtained at different collector dosages and surfactant combinations.

Use of froth characteristics in modelling the flotation process. Part II: Model for intermediate and coarse zinc particles

A two-phase flotation model especially for intermediate and coarse zinc particles was used to deter¬mine the overall rate constant for the flotation process in the Pyhäsalmi concentrator of Outokumpu Mining Co. Finland. The overall rate constants for the first zinc rougher cell of the zinc flotation circuit were used to develop an empirical model. The model was fitted to the overall rate constant by using process and image data. The two-phase flotation model and the empirical model can be used to predict the recovery of intermediate and coarse zinc particles in plant conditions.

CLUSTER ANALYSIS OF MINERAL PROCESS DATA WITH AUTOASSOCIATIVE NEURAL NETWORKS

Experimental results indicate that autoassociative neural networks provide a robust method for the identification of clusters in process data. Cluster identification is accomplished by extracting a single feature from each multivariate data vector. The ranked features can be used to construct a feature curve, which is subsequently used as a basis for partitioning of the data space. In three case studies, involving two sets of ore samples, and a set of flotation froth features, with 11, 13 and 5 variables respectively, the clusters identified with the neural network appeared to be better than those obtained by conventional means.

Effect of Fluid Properties on Two-Phase Froth Characteristics

Fluid properties have a significant influence on the structure and dynamics of froths in agitated vessels. In this paper, the structure and dynamics of surface froths of 21 different liquids in agitated vessels were studied by use of features extracted from digitized images of the froths. The effect of fluid density, surface tension, viscosity, and ionic strength on two froth features representing the average bubble size and the stability of the froth was investigated. Experimental results indicated that the surface tension and the fluid density had the most significant influence on the structures of the froths. An increase in surface tension resulted in a decrease in the stability of the froth as well as a decrease in the average bubble size of the froth. Likewise, an increase in the density resulted in a decrease in froth stability as well as a decrease in the average bubble size distribution of the froths.

Effect of particle size on flotation performance of complex sulphide ores

Flotation processes occurring in the bulk and froth phases have a characteristic influence on the structural features and dynamics of the flotation froth. It is recognized that the structure and texture of a mineral froth is a good indicator of flotation separation performance. The surface froth feature and dynamics are presented by three features extracted from the digitized images of the froths, i.e. SNE, a rough indication of the average bubble size of the froth, froth stability and the average grey level of the froth, an indication of mineral loading. Particle size is an important parameter in flotation operation. Nowadays, particle size is often measured and controlled in flotation concentrators. In this study the dependence of the froth structures on the particle size variation was investigated on the batch flotation of a sulfide ore from the Merensky reef in South Africa, and the size by size recovery curves were studied as well. In general medium particles produced bubbles smaller than those observed in the presence of fine and coarse particles, and the recovery rates were larger. Entrainment was a contributory mechanism to the recovery of fine particles. The fluctuation of flotation indices on the particle size change can be diagnosed and predicted by the froth structures change with a high degree of accuracy.

Relationship between surface froth features and process conditions in the batch flotation of a sulphide ore

Flotation processes occurring in the bulk and froth phases have a characteristic influence on the structural features and dynamics of the flotation froth. In principle the froth features can therefore be used as a useful indicator of the performance of the flotation system. In this study the surface froth features and dynamics are represented by three features extracted from the digitized images of the froths, viz. a statistical feature which is a rough indication of the average bubble size of the froth, a measure of the froth stability, as well as the average grey level of the froth, which is an indication of mineral loading. The effect of high intensity conditioning on the batch flotation of a sulphide ore from the Merensky reef in South Africa was investigated, and the significantly beneficial effect of high intensity conditioning on the performance of the flotation was clearly reflected in the smaller bubble size distributions and greater stability of the flotation froths.

Two-dimensional magnetic liquid froth: Coarsening and topological correlations

We present an experimental study of a cellular system which may be formed in a two-dimensional ~2D! layer made of an immiscible mixture of a magnetic fluid and an oil. We obtain a wet or a dry 2D froth, the characteristics of which are determined by the strength of an externally applied magnetic field. The froth is formed in an equilibrium state; the topological and geometrical features of the froth are fixed by the value of the applied field. The cellular pattern of the froth is stable in time, and a coarseninglike behavior is observed on decreasing the amplitude of the field. This cellular system can be used as a model to study topological processes in the equilibrium state, contrary to soap froths which are nonequilibrium systems because gas diffusion occurs. We show that the topological characteristics are statistically reversible after a magnetic-field cycle, and we present a statistical study of the froth features as a function of the amplitude of the field. The topological correlations between neighboring cells are well described by the Aboav-Weaire law. Finally, we consider the area of an n-sided cell, and show that its growth rate ~magnetic field dependent! is, in a surprising manner, proportional to n26, similarly to the Von Neumann law. @S1063-651X~97!10009-5#

Machine learning strategies for control of flotation plants

Although flotation processes are notoriously difficult to model from first principles, knowledge-based systems can be used to great advantage to monitor and control plants, provided that process knowledge can be captured effectively on the plant. By making use of machine learning techniques the features of the surface froths of flotation cells can be used to construct representations of the behaviour of a plant. Two probabilistic decision tree methods and a backpropagation neural net were all equally capable of classifying the different froths at least as well as a human expert. Explicit decision trees were derived, relating froth characteristics to froth surface structures. Relatively sharply clustered Sammon maps of froth structures were obtained, allowing good visualisation of multidimensional flotation data.

The interrelationship between surface froth characteristics and industrial flotation performance

This paper discusses the rapid development in computer technology and neural networks that are used to transform recently developed concepts and available technology into a new generation of intelligent automation systems. In this study features extracted from images of froths by an on-line machine vision system in an industrial precious metal flotation plant were used to relate froth characteristics with the performance of the plant by using self-organising and Sammon maps. This intelligent vision system constitutes a powerful tool for the investigation and interpretation of the effect of various flotation parameters. Previous work is extended by relating surface froth characteristics with industrial flotation control and performance variables. This method of system identification represents a significant development towards an automatic control system.

Review and analysis of factors controlling the mechanical flotation of gangue minerals

Mechanical flotation of gangue minerals is reviewed. First, mechanisms that contribute to gangue transportation are considered. The effect of water recovery and other essential factors on gangue recovery is described, and mathematical models for classification and entrainment of gangue are presented. The importance of froth characteristics is also discussed. An analysis method to evaluate the entrainment of gangue in flotation circuits is presented. Measures to restrain the mechanical flotation of gangue are also considered.

The interpretation of flotation froth surfaces by using digital image analysis and neural networks

The rapid developments in computer vision, computational resources and artificial intelligence, and the integration of these technologies are creating new possibilities in the design and implementation of commercial machine vision systems. In chemical and minerals engineering, numerous opportunities for the application of these systems exist, of which the characterization of flotation froth structures is a good example of the utilization of visual data as a supplement to conventional plant data. In this paper images from pyrite batch flotation tests conducted after a factorial design as well as images from a copper flotation plant were used to understand the relationship between froth characteristics and flotation performance better. The results show that a significant amount of data can be extracted from flotation surface froths. Techniques have been developed to characterize chromatic information, average bubble size, froth texture, froth stability and mobility of surface froths. It has been shown that most of the froth characteristics of this study can be explained in terms of the concentration of solids in the froth and the factors that affect the solids concentration. The techniques developed proved to be useful in investigating the effect of a mixed collector and the addition of copper sulphate. The depressing effect of the copper sulphate and the higher grades and recoveries made possible by the mixed collector under these conditions were explained by analysis of the froth features. Excellent results were obtained in modelling the relation between froth characteristics or froth grade and recovery by using a backpropagation neural network. A sensitivity analysis showed that the most important froth features for the experimental conditions of this study are the froth stability, mobility and average bubble size. This computer vision system constitutes a powerful research tool for the investigation and interpretation of the effect of various flotation parameters. This paper also shows how the rapid development in computer technology and related disciplines can be used to transform recently developed concepts and available technology into a new generation of intelligent automation systems.

On-Line Image Analysis to Improve Industrial Flotation Plant Performance

In this study image features extracted from froth images by an on-line machine vision system in an industrial platinum flotation plant were used to relate froth characteristics and flotation performance by using neural networks. It has been shown that a considerable amount of data can be extracted from flotation surface froths and that both novel feedback control procedures and feedback control as a complement to conventional feedforward systems are made possible. Feature measures such as chromatic information, average bubble size, froth texture, froth stability and mobility of surface froths were used in the on-line classification of flotation froths. This intelligent vision system constitutes a powerful research tool for the investigation and interpretation of the effect of various flotation parameters. This paper shows how the rapid development in computer technology and neural networks can be used to transform recently developed concepts and available technology into a new generation of intelligent automation systems.

Column flotation froth characteristics — stability of the bubble-particle system

This study discusses the phenomena around a water-drained column froth and gives some insight on the mechanisms involved in solids transfer. Theoretical study of the stability of the bubble-particle system has shown that detachment may occur at the interface because of the kinetic energy released by deceleration and impact upon arrival at the interface. Significant destabilizing conditions are caused by bubble oscillation in the higher froth layers since the kinetic energy acquired momentarily by a particle attached on an oscillating bubble is comparable to the required detachment work. A qualitative model of a water washed column froth is discussed, based on the above analysis and the up-to-date knowledge on froths. Entrainment is successfully eliminated at the cost of recovery.

Selective gold flotation at Sonora Mining’s Jamestown concentrator, using Aero 5688 promoter

This paper discusses the replacement of AEROFLOAT® 25 promoter by AERO® 5688 promoter at Sonora Mining Corp.’s California Mother Lode concentrator. Flotation concentrate is trucked 120 miles to a leach plant in Nevada, so the reduced mass resulting from higher gold grades and reduced talceous gangue and barren pyrite resulting from this change in promoters has brought about a major decrease in shipping costs. Preliminary laboratory testing indicated that free milling gold and controlled amounts of pyrite could be floated using Aero 5688 promoter with reduced dosages of Aero 350 xanthate. Extensive plant trials confirmed that the new reagent suite could indeed maintain gold recoveries while reducing total mass. Improved froth characteristics also improved operating flexibility in treating various ore types, and overall reagent costs have been reduced.

Froth Characteristics in Air-sparged Hydrocyclone Flotation

Abstract Air-sparged hydrocyclone flotation is a new technology that has been under development during the past decade. This technology combines froth flotation principles together with the flow characteristics of a hydrocyclone such that the air-sparged hydrocyclone system can perform flotation separations in a matter of seconds or even less. The most important feature of the air-sparged hydrocyclone is its high specific capacity which corresponds to significant savings in capital cost (equipment and floor space). In air-sparged hydrocyclone flotation, the slurry is in swirl flow having high tangential and axial velocities. Both concentrate product (froth) and tailings are formed and discharged at high velocities. These unique fluid-flow features have a significant effect on the nature of the froth phase created and the corresponding transport properties. Froth characteristics and froth control as currently understood are emphasized in this chapter which reviews the state-of-the-art in air-sparged hydroc...

Froth characteristics of shallow bubble columns with sieve plates

Radial profiles of gas holdup, liquid circulation and equivalent clear liquid height in the froth regime were measured in a shallow bubble column with Correlations for radial profiles of gas holdup in the middle region, which is one of three axial regions in the froth, and for mean values of equivalen