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1

Study of the effect of airflow rate and agitation speed on entrainment of ash particles in bottom ash flotation

Kim Minsik, You Kwangsuk, Kim Kwanho, Jeon Yong-woo

Physicochemical Problems of Mineral Processing

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2024

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Vol. 60, iss. 2

art. no. 187835

EN

To enhance the recovery and grade of the final product, reducing the entrainment of the hydrophilic particles during flotation is critical. We conducted the improvement of entrainment to reduce the amount of ash in the concentrate with the purpose of recovering high-quality unburned carbon from the bottom ash and reusing it as fuel in power plant. In this study, we investigated the effects of airflow rate and agitation speed on the entrainment of hydrophilic particles. In the selfaerating flotation machine, it was difficult to independently control the agitation speed and airflow rate, resulting in the degree of entrainment of 0.74. By independently controlling the airflow in which hydrophobic particles can float under conditions of the degree of entrainment with 0.7 (low agitation speed: 900 rpm), the combustible recovery and unburned carbon content of concentrate were 93.71% and 93.60%, respectively. The degree of entrainment was found to be 0.57, and entrainment could be minimized through independent control of airflow rate and agitation speed. To minimize entrainment, it is effective to inject air that can suspend hydrophobic particles in a low agitation speed condition.

2

Flotation of copper-bearing shale at different pH values of solutions and sodium chloride concentrations

Sajewicz Jakub, Ratajczak Tomasz

Physicochemical Problems of Mineral Processing

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2023

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Vol. 59, iss. 6

art. no. 176242

EN

Flotation of copper-bearing shale in aqueous solutions of NaCl at their different pH values was investigated. The tests were carried out in a laboratory flotation machine. The pH range was between 5 and 10 while NaCl concentrations were 0.5M, 1.0M and 2.0M. It was observed that the flotation recovery of the copper shale was increasing with the increase of pH and concentration of the salt solution. On the basis of thermodynamic and hydrodynamic considerations it was postulated that the increasing surface tension was responsible for better shale flotation observed with increasing salt concentration. The observed improved shale flotation caused by increasing pH is most likely due to changes in the properties of the thin film between particle and bubble including mosaic structure of water on the surface of shale. It was shown that the zeta potential of shale particles, zeta potential of air bubbles, solution surface tension, and shale hydrophobicity were not responsible for the increasing with pH recoveries.

3

Understanding the collection behavior of gangue minerals in fine flake graphite flotation

Xu Wenlu, Sun Kangkang, Qiu Yangshuai, Zhang Lingyan, Yang Luo, Wei Shaowei, Ding Dafa

Physicochemical Problems of Mineral Processing

|

2022

|

Vol. 58, iss. 1

101--112

EN

Flotation is one of the most common and effective methods for the beneficiation of natural graphite resources. However, the upgrading efficiency of flotation is always finite due to the undesirable collection of gangue minerals. In this work, the collecting mechanism of three typical gangue minerals, including mica, quartz, and feldspar, in fine flake graphite flotation was investigated. Results of batch flotation tests for single-minerals and artificial mixtures confirmed the enhanced collection of gangues in the presence of graphite particles. Contact angle and zeta potential results and theoretical calculations of the interaction between graphite and gangue particles based on typical DLVO theory indicated that it is impossible to collect gangue minerals by true flotation or through heterocoagulation with graphite particles. The fitting results of accumulated gangue recoveries and accumulated water recoveries using the Warren method demonstrated that most gangue minerals entered the concentrate through entrainment, with a small proportion by bubble inclusions.

4

Effect of air flow rate and froth depth on the flotation performance : an industrial case study in a 10 m3 cell

Ostadrahimi Mahdi, Farrokhpay Saeed, Pirmoradi Saeed, Noparast Mohamad

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 5

art. no. 154852

EN

The main purpose of the froth zone in flotation is to transport all the valuable particles from the pulp zone into the concentrate. However, in practice, a complete recovery of these particles is rarely achieved since some of them are detachment from the bubbles and return to the pulp zone. While this is an important topic in the mineral flotation industry, the previously published papers are mainly limited to small laboratory scales. Therefore, this study aimed to examine the effect of two main flotation variables (air flowrate and froth depth) on the flotation of iron ore in a 10 m3 industrial scale cell. It was found that, when the air flowrate increased from 45 to 146 m3/h, the velocity of the bubble coalescence also increased. In addition, when the froth depth increased from 5 to 30 cm, the product grade showed on average 2 unit increase (for instance, from 12% to 14%) due to the detachment of particles and liquid drainage. It was also found that the flotation concentrates recovery decreased with the increasing froth depth and air flowrate.

5

The effect of sodium carboxymethyl cellulose on the entrainment of zoisite in flotation

Zhang Zhengjun, Ou Leming, Jin Saizhen, Zhou Hao

Physicochemical Problems of Mineral Processing

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2021

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Vol. 57, iss. 2

34--47

EN

During flotation, fine gangue minerals can enter the concentrate through mechanical entrainment, which seriously affects the quality of concentrate. In this work, the effect of sodium carboxymethyl cellulose (CMC) on the flotation performance of zoisite, a silicate mineral, was studied. The role of CMC in reducing zoisite entrainment was investigated by dynamic foaming tests, surface tension measurements, rheology measurements, sedimentation tests, and optical microscopy experiments. The flotation results showed that zoisite mainly entered the concentrate by entrainment; the addition of low dosages of CMC decreased zoisite entrainment and efficiently separated cassiterite from zoisite; moreover, the concentrate grade and recovery of SnO2 increased by 1.27 % and 5.63 %, respectively, by using CMC in closed-circuit flotation tests. Dynamic foaming studies on the two-phase and three-phase foam/froth revealed that the presence of CMC decreased the froth ability and froth stability, and greatly altered the three-phase froth structure. Basically, the bubbles in the foam were larger after adding CMC. For the two-phase foam, the change of foam property had little to do with surface activity and bulk viscosity. For the three-phase froth, the froth property was strongly affected by the interaction of CMC and zoisite. The results of the sedimentation test and microscopy experiment demonstrated that CMC can cause zoisite to flocculate and enlarge the particle size, which was the main reason for the decrease of froth stability and entrainment. This study indicates that the side effects of depressants should not be overlooked when discussing the role of depressants in flotation.

6

Use of bubble load to interpret particle transport across the pulp-froth interface in a flotation cell

Bhondayi Clayton

Physicochemical Problems of Mineral Processing

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2020

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Vol. 56, iss. 1

54--64

EN

This work demonstrates the use of bubble loads to understand the transport of particles across the pulp-froth interface in a flotation cell processing an Upper Group 2 chromitite seam (UG2) ore. Bubble loads were measured on the first primary cleaner cell of an operating flotation plant using a bubble load meter with a 20mm riser diameter. A bubble load value of 10.58grams/liter was obtained. The bubble load data was used to understand, entrainment and dropback of chromite as a function of particle size. By defining terms such as froth flow number and net dropback, it was found that chromite (known to be non-floatable) was also recovered through true flotation. The entrainment of chromite was found to be predominantly in -25 μm size while +25 μm size particles were found to be floatable and highly susceptible to dropping back. Net-dropback of chromite particles was found to increase with a decrease in chromite particle size contrary to expectation. An overall froth flow number of 69% was obtained.

7

Mechanism of the combined effects of air rate and froth depth on entrainment factor in copper flotation

Wang Lei, Xing Yaowen, Wang Jun

Physicochemical Problems of Mineral Processing

|

2020

|

Vol. 56, iss. 1

43--53

EN

The effect of air rate and froth depth on the entrainment factor in flotation has been extensively studied, but further investigation on the underlying mechanism for their effect is still required. In this study, flotation tests were performed at different air rates and froth depths in a 3 dm3 continuously operated cell using an artificial copper ore. The results showed that entrainment factor was affected by both air rate and froth depth, and the combined effect of these variables on entrainment factor depended strongly on the particle size. The entrainment factor increased with either increasing air rate at a relatively shallow froth or decreasing froth depth at a relatively high air rate. At a very low air rate and deep froth, higher entrainment factor was observed for mid-size and coarse particles. When the entrainment factor was correlated to the effective liquid velocity at the pulp/froth interface, the results indicated that multiple mechanisms were responsible for the effect on entrainment factor. At a relatively high air rate and shallow froth depth, entrainment factor had a linear relationship with the interface effective liquid velocity, suggesting that drag force dominated the change in the entrainment factor when air rate and froth depth were varied. At a very low air rate and deep froth, the entrainment factor for fine particles was found to correlate strongly with the interface effective liquid velocity, while the entrapment of solid particles may be the main reason for the high entrainment factor for mid-size and coarse particles under this condition.

8

Effects of monovalent and divalent ions in coal gasification brine on the froth entrainment and flotation kinetics of anthracite coal

Zheng Kaidi, Bu Xiangning, Zhou Shaoqi, Zhang Jing, Shao Huaizhi, Sha Jie, Xie Guangyuan

Physicochemical Problems of Mineral Processing

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2020

|

Vol. 56, iss. 5

960--974

EN

Water plays a critical role in various stages of flotation, which brings a lot of pressure to the flotation processing plants resided in dry areas. In this regard, it will be of significance to explore the feasibility of using wastewater resources in mineral flotation. Coal gasification brine (CGB) that contains a high concentration of salts becomes the subject of interest of this study. In this study, a synthetic CGB solution, which was prepared by adding NaCl, MgCl2, and CaCl2 to ultrapure water based on the composition of salts in a real CGB, was used in the flotation of anthracite coal. The comparison results based on the first-order model showed that flotation in the presence of the synthetic CGB solution gave a higher flotation selectivity (SI =7.086) than that of flotation in ultrapure water (SI=3.545). Water recoveries and average bubble sizes in the froth showed that the addition of the three salt ions (Na+, Mg2+, and Ca2+) was conducive to diminishing the entrainment of gangue materials as a result of the reduction of water reporting to the froth. Additionally, the zeta potentials and induction time measurements indicated that only divalent ions of Ca2+ and Mg2+ significantly compressed the double electrical layer and enhanced the attachment between bubbles and coal particles according to DLVO theory, which was further confirmed by the calculation of interaction energy between coal and bubbles. The findings of the present work may promote the use of CGB as a potential water resource in coal flotation.

9

Effect of particle size on flotation performance of hematite

Luo Ximei, Song Shuixiang, Ma Mingze, Wang Yunfan, Zhou Yongfeng, Zhang Ying

Physicochemical Problems of Mineral Processing

|

2019

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Vol. 55, iss. 2

479--493

EN

The effect of particle size on flotation performance of hematite and quartz was investigated. Microflotation, X-ray photoelectron spectroscopy analysis, reagent adsorption measurements, and collision and attachment probability calculation between particle and bubble were conducted in this investigation. The results showed that the floatability of minerals with different particle size fractions was different, which was mainly related to surface bonding site, reagent adsorption, collision probability and entrainment. The quartz with different particle size had little impact on hematite recovery, but -45 μm fraction negatively affected Fe grade of concentrate both in the direct and reverse flotation of hematite. In the direct flotation, the Fe grade in froth product dropped off due to the fine quartz entrainment. While in the reverse flotation, the Fe grade in sink product dropped off as a result of difficulty in floating fine quartz particles, which was due to lower collision probability. Meanwhile, in the reverse flotation, the presence of hematite fines (-18 μm fraction) also had negative impact on hematite recovery because of fine particle entrainment.

10

Water quality effects on a sulfidic PGM ore: Implications for froth stability and gangue management

Manono M. S., Corin K., Wiese J.

Physicochemical Problems of Mineral Processing

|

2018

|

Vol. 54, iss. 4

1253--1265

EN

Polysaccharide depressants play a crucial role in the flotation of sulfidic PGM bearing ores as they prevent naturally floatable gangue (NFG) from reporting to the concentrate. This action is regarded as critically important because less dilution of the concentrate means lower costs for downstream processes. However, abnormal water conditions such as high concentrations of ions in the flotation system can modify the selectivity of these depressants. It is well known that the existence of selected electrolytes in water can alter the behaviour of some polysaccharide depressants by enhancing their adsorption onto gangue minerals and thereby prevent naturally floatable gangue from moving into the froth phase. Concurrently these same electrolytes may enhance frothability owing to their stabilising effect on the bubbles within the system. Plant water at various ionic strengths was investigated against sodium carboxymethyl cellulose (CMC) dosages in order to understand electrolyte-depressant interactive effects during the flotation of a Merensky ore in a batch flotation cell, using entrainment, rate of NFG recovery, and total gangue recovery as proxies. The study showed that the NFG recovery per unit mass of water decreased with increasing ionic strength at all CMC dosages, however the total amount of gangue reporting to the concentrate increased with increasing ionic strength at all CMC dosages. Thus, this paper considers the effects of both ionic strength and CMC dosage within flotation. It further investigates whether any interactive effects exist between froth stability and entrainment when considered simultaneously.

11

Evaluation of sodium petroleum sulfonates with different molecular weights for flotation of kyanite ore

Chen B. Z., Gao H., Li Y., Jin J., Ren Z., Wang W.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

956--968

EN

The flotation performance of sodium petroleum sulfonates with different molecular weights was evaluated for flotation of a kyanite ore, by investigating valuable mineral recovery-grade, flotation kinetics and gangue entrainment. The results indicated that the higher molecular weight of agent, the higher final cumulative kyanite recovery was, with the maximum value of 72% being obtained with KY-3 with the molecular weight of 438. The final cumulative kyanite grade initially increased, and then decreased with the molecular weight increasing. In other words, the maximum final cumulative kyanite grade (i.e. 89.05%) was obtained with KY-2 with the molecular weight of 392. The kyanite flotation kinetics followed the first order kinetics well, while the modified flotation rate constant showed a decreasing trend after the initial increase as the molecular weight increased. In addition, the overall entrainment degree decreased with decreasing molecular weight of sodium petroleum sulfonates. The use of KY-2 in kyanite flotation was an attractive option in comparison with KY-1 and KY-3.

12

Effects of colloidal montmorillonite particles on froth flotation of graphite, galena and fluorite

Chen T., Zhao Y., Li H., Song S.

Physicochemical Problems of Mineral Processing

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2017

|

Vol. 53, iss. 2

699--713

EN

The effect of colloidal montmorillonite (MMT) on froth flotation of graphite, galena and fluorite was investigated in this work. The results showed that the presence of sufficient amount of colloidal MMT particles in the mineral slurry would be detrimental of flotation by reducing the recovery of minerals. This observation was attributed to slime coating of MMT on the coarse valuable mineral particles and entrainment of MMT particles in the froth product together with water in the triangle froth zones. The former would reduce the recovery of the valuable minerals because of hydrophilic MMT coating. The latter would decrease the concentrate grade. The degree of slime coating depended on slurry pH, while the degree of entrainment was closely related to water recovery. It was also found that slime coating was a dominant factor in mineral flotation in acidic pH regions in the presence of colloidal MMT particles.

13

Recovery mechanisms of sericite in microcrystalline graphite flotation

Li H., Ou L., Feng Q., Chang Z.

Physicochemical Problems of Mineral Processing

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2015

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Vol. 51, iss. 2

387--400

EN

Sericite is the main contaminant of concentrate in commercial microcrystalline graphite ore flotation. It was necessary to identify its recovery mechanisms so that the appropriate solution can be selected. In this study, the influence of sericite on flotation selectivity of microcrystalline graphite ore and its recovery mechanisms were investigated. Artificial mixtures flotation test suggested that sericite seriously reported into concentrate leading to poor flotation selectivity of microcrystalline graphite ore. However, the aggregation/dispersion behavior of artificial mixtures indicated that a large repulsive energy existed between sericite and microcrystalline graphite particles at pH 7.4, and sericite was not likely to report into graphite concentrate by slime coating. The results obtained from contact angle measurements and a technique of Warren showed that the floated sericite reached the froth via a combination of both entrainment and entrapment mechanisms, not via true flotation.

14

A pilot study on the effect of music-heart beat feedback system on human heart activity

Nomura S., Yoshimura K., Kurosawa Y.

Journal of Medical Informatics & Technologies

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2013

|

Vol. 22

251--256

EN

We developed a music-heart beat feedback system to test the efficacy of the entrainment between music and human heart beat. As a result of regulating the music tempo as 10% faster (namely FAST condition) or slower (SLOW) than heart beat in a real time series, the subjects’ heart rate was successfully modulated as significantly higher in the FAST condition and lower in the SLOW condition. The timeliness regulation of this feedback system may play a key role to bring forth the music-heart beat entrainment.

15

Transitional, entraining, cloudy, and coastal boundary layers

Angevine W.

Acta Geophysica

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2008

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Vol. 56, no. 1

2-20

EN

Atmospheric boundary layers are marvelously varied and complex. Recent re-search has examined some of that variety. Boundary layers over land undergo drastic changes throughout the day as the sun rises and sets, and as clouds form and dissipate. Air is entrained at the top of the boundary layer at varying rates. As air moves over the coast, the boundary layer reacts to changes in surface forcing. All of these changes affect pollutant transport and weather formation. In this paper, research attempting to understand transitional, cloud-topped, and coastal boundary layers, and boundary-layer top entrainment, is reviewed.

16

Wyniesienie mechaniczne ziaren poddanych flotacji wyłącznie spieniaczem

Szyszka D.

Górnictwo i Geoinżynieria

|

2007

|

R. 31, z. 4

81-86

PL

W artykule zaproponowano metodę oceny zdolności spierniaczy flotacyjnych do wyniesienia mechanicznego ziaren podczas przepuszczania powietrza przez zawiesinę ziarn hydrofilnych. Polega ona na pomiarze wyniesienia mechanicznego ziarn w komorze flotacyjnej w zależności od czasu flotacji i stężenia spieniacza. W efekcie badań uzyskuje się charakterystyczną liczbę opisującą maksymalne wyniesienie mechaniczne ziaren po długich czasach flotacji i przy podwyższonych stężeniach spieniacza. Dla metyloizobutylocarbinolu (MIBC) ta charakterystyczna liczba wynosi 32%.

EN

The paper describes a method for assessment of ability of flotation frothers for mechanical entrainment during bubbling of air through suspension of hydrophilic particles. The method consists of measurement of particle recovery in laboratory flotation cell at various flotation times and frother concentrations. The result of the measurement is a characteristic number, which describes mechanical flotation of mineral particles after a long flotation time at such frother concentration at which the entrainment does not increases any further. The characteristic number for methylisobutylcarbinol (MIBC) characterizing the recovery of quartz in the investigated flotation machine was equal to 32%.

17

Ventilation of the Baltic Sea deep water : A brief review of present knowledge from observations and models

Meier H. E. M., Feistel R., Piechura J., Arneborg L., Burchard H., Fiekas V., Golenko N., Kuzmina N., Mohrholz V., Nohr C., Paka V. T., Sellschopp J., Stips A., Zhurbas V.

Oceanologia

|

2006

|

No. 48 (S)

133-164

EN

The ventilation of the Baltic Sea deep water is driven by either gale-forced barotropic or baroclinic salt water inflows. During the past two decades, the frequency of large barotropic inflows (mainly in winter) has decreased and the frequency of medium-intensity baroclinic inflows (observed in summer) has increased. As a result of entrainment of ambient oxygen-rich water, summer inflows are also important for the deep water ventilation. Recent process studies of salt water plumes suggest that the entrainment rates are generally smaller than those predicted by earlier entrainment models. In addition to the entrance area, the Słupsk Sill and the Słupsk Furrow are important locations for the transformation of water masses. Passing the Słupsk Furrow, both gravity-driven dense bottom flows and sub-surface cyclonic eddies, which are eroded laterally by thermohaline intrusions, ventilate the deep water of the eastern Gotland Basin. A recent study of the energy transfer from barotropic to baroclinic wave motion using a two-dimensional shallow water model suggests that about 30% of the energy needed below the halocline for deep water mixing is explained by the breaking of internal waves. In the deep water decade-long stagnation periods with decreasing oxygen and increasing hydrogen sulphide concentrations might be caused by anomalously large freshwater inflows and anomalously high mean zonal wind speeds. In different studies the typical response time scale of average salinity was estimated to be between approximately 20 and 30 years. The review summarizes recent research results and ends with a list of open questions and recommendations.

18

Prediction of holdup in liquid slugs

Brauner N., Ullmann A.

Transactions of the Institute of Fluid-Flow Machinery

|

2003

|

nr 112

75--90

EN

Correlations and models from the literature for the prediction of void fraction in liquid slugs are reviewed. It is shown that a mechanism that can explain the slug aeration in vertical, horizontal and inclined tubes has not yet been established. A new model that attributes the aeration of the liquid slug to a recurrent bubble entrainment from the Taylor bubble (TB) tail is introtuced. The bubble fragmentation is related to the rate of turbulent kinetic energy in the shear layer, which is formed at the TB wake as the liquid film plunges into the slug front. The model has been tested against experimental data available from the literature and was found to predict the effects of liquid and gas flow rates and physical properties, as well as tube diameter and inclination on the void fraction.