Froth Flotation Column Research Articles

A Model of Froth Flotation with Drainage: Simulations and Comparison with Experiments

The operation of a froth flotation column can be described by a nonlinear convection–diffusion partial differential equation that incorporates the solids–flux and drift–flux theories as well as a model of foam drainage. The resulting model predicts the bubble and (gangue) particle volume fractions as functions of height and time. The steady-state (time-independent) version of the model defines so-called operating charts that map conditions on the gas and pulp feed rates that allow for operation with a stationary froth layer. Operating charts for a suitably adapted version of the model are compared with experimental results obtained with a laboratory flotation column. Experiments were conducted with a two-phase liquid–bubble flow. The results indicate good agreement between the predicted and measured conditions for steady states. Numerical simulations for transient operation, in part for the addition of solid particles, are presented.

Optimization of Sodium Bicarbonate Production from Ammonium Hydroxide Using a Froth Flotation Column

AbstractSodium bicarbonate is produced by the Solvay process from salt (NaCl), ammonia gas (NH3), and CO2. Here, the Solvay process was modified by using ammonium hydroxide (NH4OH) liquid to replace NH3. To increase the yield of sodium bicarbonate, a froth flotation column was used. This column can generate microbubbles of CO2, which increases the CO2 conversion. The parameters were studied using response surface methodology (RSM) with a central composite design of experiments. Based on the RSM analysis, the optimum conditions were identified. Analysis of variance shows that the reaction time is the most significant parameter affecting the production of sodium bicarbonate. Empirical quadratic multivariable equation models were obtained with R2 = 0.94. The heavy metal‐free product can be used as a food additive.

Flotation of coarse coal particles in a fluidized bed: The effect of clusters

This paper is concerned with the separation of coarse particles from siliceous gangue, in a fluidized bed froth flotation column, the NovaCell. Coarse particles are allowed to settle in the base of a column, and are fluidized by an upward-flowing stream of liquid. Air bubbles are introduced with the stream, which collide with hydrophobic particles in the bed, carrying them to the top of the vessel as flotation product.The paper describes the use of bubble clusters as a means of recovering particles in a flotation machine. Clusters are buoyant aggregates of bubbles and particles. Copious quantities were observed to form in the fluidized bed, rising to the top of the flotation column. They were present in such volumes that the froth was unable to absorb them all, and a thick cluster layer developed beneath the froth. This layer was drawn off and separated on a screen as a secondary flotation product, in addition to the conventional froth product.Here we describe the flotation of coal particles from different sources with a top size of 2 mm, in a NovaCell fluidized bed contactor. High combustibles recoveries were achieved, at acceptable ash contents, over the whole size range. The froth phase contributed approximately 65% of the total, the balance appearing on the screen. Particles of all sizes from 0 to 2 mm were represented in the froth discharge.The NovaCell gave two flotation products and two tailings streams. It was possible to control the tails from the fluidized bed so that the solids fraction was as high as 60–70%, in the size range 300 µm–2 mm. The results highlight the value of coarse particle froth flotation from a product de-watering perspective, when compared with flotation in conventional cells that are restricted to a top size of 500 µm. The ultrafine fraction less than 74 µm in diameter in the product was reduced by a third when the top size was increased to 2 mm from the normal top size of 500 µm for coal.The fact that low-buoyancy clusters can form beneath the froth, provides an alternative explanation for the phenomenon known as froth dropback.

Removal of motor oil by continuous multistage froth flotation: Effect of operational parameters

ABSTRACTA continuous multistage froth flotation column was employed to remove motor oil from water at a low concentration (500 mg/L) using an extended surfactant – branched alcohol propoxylate sulphate sodium salt (C14-15–8PO–SO4–Na) – as a frother. The highest separation efficiency (97% motor oil removal with the enrichment ratio of 16 for motor oil) was obtained at a foam height of 60 cm, an air flow rate of 40 L/min, a feed flow rate of 60 mL/min, a surfactant concentration of 0.3% (w/v), and an NaCl concentration of 1.5% (w/v). The process performance increased with increasing tray number but beyond 4 trays, the system could only offer lower concentrations of motor oil and surfactant in the effluent.

Cutting oil removal by continuous froth flotation with packing media under low interfacial tension conditions

In this work, the froth flotation unit operated in a continuous mode was applied for oily wastewater treatment with the use of cutting oil as a model contaminant oil and sodium dodecyl sulfate (SDS) as a frother. The concentrations of the cutting oil and SDS were fixed constant at 500ppm and 0.1wt.%, respectively. The effects of salinity, air flow rate, hydraulic retention time (HRT), and the packing volume percentage of packing media on the process performance were studied. The results revealed that froth flotation efficiency was optimized under low interfacial tension (IFT) conditions which also simultaneously provided high froth formation and stability. The presence of packing media in the froth flotation column significantly improved cutting oil removal effectiveness. However, beyond the optimum packing volume of 50%, oil removal efficiency decreased markedly with increasing packing volume. The optimum operating conditions were found at a NaCl concentration of 6.0wt.%, an air flow rate of 200cm3/min, a HRT of 60min, and a packing volume of 50%, corresponding to a cutting oil removal of 98.1%, an enrichment ratio of cutting oil of 2.3, a surfactant removal of 84.9%, and an enrichment ratio of surfactant of 7.8.

Motor oil removal from water by continuous froth flotation using extended surfactant: Effects of air bubble parameters and surfactant concentration

The objective of this study was to correlate the air bubble parameters in a flotation column and the surfactant concentration to the efficiency of motor oil removal from water by continuous froth flotation. C 14–15(PO) 5SO 4Na (branched alcohol propoxylate sulfate, sodium salt) was used to form microemulsions with motor oil. From the microemulsion phase diagram, the minimum surfactant concentration, known as the critical microemulsion concentration (CμC), to form a Winsor Type III microemulsion, was preliminarily selected for the froth flotation experiments. An increase in surfactant concentration was found to reduce the size and rising velocity of air bubbles in the froth flotation column, whereas the specific surface area, bubble surface area flux, bubble number flux, and residence time of the air bubbles increased with increasing surfactant concentration. The maximum removal of both motor oil and surfactant was found to correspond to the CμC. Beyond the CμC, the oil removal decreased with increasing the surfactant concentration because increasing the micelle concentration results in increasing oil stabilization.

Removal Kinetic of Fine lead Particles from Wastewater of Battery Manufacturing Plants

Removal of heavy metals from water and wastewater has received a great deal of attention. Froth flotation technique is one of the most technologies being used for treatment of polluted water, where it considered low cost process than others. This study records lab scale experiments to test efficiency of multistage froth flotation column in removing a heavy metal, (Pb fine particles less than 45 µm) from wastewater of battery industry. Solutions concentration of Pb (100ppm) was prepared and passed through flotation column. The removal efficiency was quite high for Pb ranging from 62.4-96.3% and maximum removal occurred at frother concentration (20 ppm) and superfacial gas velocity (4 cm/sec), where caprylic acid and hexanol are used as frother in this study. Attempts made to analyze the kinetic behavior of the process indicate that it follows the first-order classical rate equation for the kinetic of froth flotation process. In the proposed equation, values of the constants correlation coefficient (R) and kinetic flotation constant (k), evaluated from the experimental results then (k) related to the frother dosages and superfacial gas velocity.

Separation of Carbon Black from Silica by Froth Flotation Part 1: Effect of Operational Parameters

Froth flotation can be applied to separate hydrophobic particles from hydrophilic ones in aqueous solution with the use of an appropriate surfactant. In this work, carbon black was separated from silica gel by means of froth flotation. Since the point of zero charge, or PZC, of the carbon black (3.5) is close to that of the silica gel (4.1), a nonionic surfactant (ethoxylated alcohol) was selected as the separating agent. Based on experimental results using a surfactant concentration of 62 µM or 75% of its critical micelle concentration (CMC), up to 70% of carbon black recovery was achieved with a carbon black enrichment ratio around 3.5. Added electrolyte (NaCl) showed a negligible effect on the separation efficiency. The presence of the surfactant was found to provide both a higher mass transfer surface area and to reduce the coalescence of air bubbles in the froth flotation column.

Diesel Oil Removal by Froth Flotation Under Low Interfacial Tension Conditions II: Continuous Mode of Operation

The objective of this study was to investigate the relationship between interfacial tension (IFT) and foam characteristics and the efficiency of diesel oil removal from water in a continuous froth flotation column. The effects of operational parameters, including surfactant concentration, salinity, oil-to-water ratio, foam height, air flow rate, and hydraulic retention time (HRT) on the oil removal were investigated in the continuous mode of a froth flotation operation and compared to batch operation results. Unlike the batch system, for the continuous system used in the present study, having only branched alcohol propoxylate sulfate sodium salt surfactant (C14–15(PO)5SO4Na) and NaCl present in the solution yielded such poor foam characteristics that a stable froth which overflowed the flotation column could not be produced, so the addition of sodium dodecyl sulfate (SDS) as a froth promoter was used to improve the foam stability. Unlike the batch froth flotation system with only C14–15(PO)5SO4Na, the continuous froth flotation with the mixture of C14–15(PO)5SO4Na and SDS, it was not possible to find a SDS and a NaCl concentration at which both ultralow IFT and good foaming were both achieved. Foam formation, stability, and production rate were found to be crucial parameters to the froth flotation efficiency. The continuous froth flotation system offers a high diesel oil removal of 96% in the single stage unit. Demonstration of efficient operation in the continuous mode in this work is important to the practical application of froth flotation in large scale processing.

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%.

Vitrinite-rich coal concentrate intrinsic reactivity index

This work defines a new reactivity coal combustion parameter called intrinsic reactivity index (IRI), combining reactive maceral fraction (vitrinite/liptinite), non-reactive maceral fraction (inertinite/intrinsic mineral matter) and vitirinite reflectance averages. Coal samples from La Yolanda and Guachinte (Valle del Cauca) collieries were used to evaluate the IRI; samples consisted of original and vitrinite concentrated fractions obtained from froth flotation column. This new parameter was compared to three conventional parameters: weighted mean activation energy (WMAE), peak temperature (PT) and final temperature (FT). Results revealed that vitrinite concentrated fractions had higher IRI figures than original coal. This meant that vitrinite concentrated fractions presented higher reactivity to combustion than original coal. Results also showed that EAMP TP and TF decreased with an increase in IRI, suggesting that coal combustion reactivity becomes improved when vitirinite concentration in coal is increased.

Ethylbenzene Removal by Froth Flotation Under Conditions of Middle‐Phase Microemulsion Formation II: Effects of Air Flow Rate, Oil‐to‐Water Ratio, and Equilibration Time

Dihexyl sulfosuccinate (aerosol MA or AMA) was used to prepare microemulsion solutions in a study of the froth flotation process in batch mode to remove emulsified ethylbenzene from water. Oil removal, surfactant removal, and enrichment ratio were used to evaluate the performance of froth flotation. In this study, the effects of air flow rate, oil‐to‐water ratio, and equilibration time were investigated. A very high air flow rate was found to create more turbulence in the froth flotation column, resulting in low oil removal. As the oil‐to‐water ratio decreases, the enrichment ratio increases, whereas the oil removal slightly decreases. The froth flotation column with a feed solution in which the oil and water had been allowed to equilibrate was found to yield much higher ethylbenzene removal than that with a nonequilibrium feed solution. When the feed solution was agitated for 40 minutes to induce a state closer to equilibrium than with no mixing, the ethylbenzene removal was nearly as high as that with the equilibrium feed solution.

Process Dynamics and Control of a Pilot Flotation Column

Abstract Froth flotation column is a counter-current bubble column that has recently been applied to separate hydrophobic mineral particles from mineral ore slurries. This paper describes the process control strategy, the process dynamics, and the control of a pilot scale froth flotation column. Control and monitoring of the flotation column was carried out using a personal computer equipped with an interface device. A direct digital feedback control loop was employed to control the interface level between the bubbly zone and the froth zone of the column. The incremental form of Proportional (P) and Proportionalintegral (PI) control algorithms were studied. Experimental results are presented for step changes in the interface level (set point), the feed flow rate, the wash water flow rate, and the gas flow rate. The start-up behaviour of the column is also described. Resume Une colo nne de flottation d'ecume est une colo nne a bulle fonctionnant a contre-courant. Recement, elle a ete utilisee pour separer ...

Control and monitoring of a froth flotation column using a personal-computer

A computer-automated froth flotation circuit was designed and developed. Control and monitoring of the flotation column was carried out using a personal computer equipped with an inputloutput interface device. Process control strategy and analysis of the system are presented. The system hardware and software that were designed and developed are discussed.

Flow characterization of a flotation column

AbstractThe flow characteristics of a froth flotation column have been experimentally studied using air and aqueous surfactant solutions without the presence of solids. The hold‐up behaviours of the bubbly and the froth zones of the column were linked together using the drift‐flux model. The ratio of the gas drift‐flux, jgf, to the bubble terminal velocity, V, for both the bubbly and the froth zones was found to be well correlated by the Richardson–Zaki equation: