Froth Product Research Articles

Magnetic field application in cationic silica flotation of magnetic taconite concentrates

The application of a magnetic field was shown to be effective in controlling iron losses in a pilot-scale cationic silica flotation in the processing of magnetic taconite concentrates. The design of a magnetic-field distribution device and batch-flotation test results using a 1.42-m3 (50 cu ft) WEMCO flotation cell are reported. Major losses of iron units in froth products were in the −25-μm (−500-mesh) fraction, and the application of a magnetic field decreased the flotation of fine magnetite, thereby improving the selectivity of separation. The “as-received” sample was sufficiently magnetized, and no further benefit was gained by the magnetizing treatment. The selectivity was somewhat adversely affected by demagnetizing the sample, though its effect was minimal due to the magnetic field. The device is simple in construction, low cost and may be readily installed in existing equipment.

低品位炭の改質および高度脱灰に関する研究

This paper describes the upgrading of low rank coal by hot water drying (HWD), flotation, oil agglomeration and chemical coal cleaning. The coals used were Asam-Asam coal (3.4 db% ash, 73.7 dafb% C) and Beluga coal (8.0 db% ash, 71.5 dafb% C).The HWD treatment was carried out at different temperatures such as 270, 300 and 330 °C. With increasing temperature water content and carboxyl content of the both coals were decreased and their floatability became higher. From the results of float-sink test for Beluga raw coal, it was estimated that a coal concentrate with 4 % ash and 92 % yield is effectively obtained by heavy medium separation for middle size coals(- 1,000 + 425μm) at a specific gravity of 1.45. Combustible matter recovery of the both HWD treated coals by flotation was 20-30 % higher than that of the both raw coals and the ash content of the froth product was lower for the treated coals than the raw coals. By 3 stage flotation of the fine HWD treated Beluga coal(53μm of average size), a clean coal product was obtained with less than 5 % ash and 76 % recovery of combustible matter.Products containing 4.1-4.3 % ash were also recovered by oil agglomeration of the fine HWD treated Beluga coals (9 and 3μm of average sizes). This result is similar to that obtained by 3 stage flotation of 53μm average size coal and it indicated that removal of about 4 % ash is impossible by physical separation method alone. Chemical coal cleaning method of the HWD treated coals with aqueous caustic process leads to a drastic decrease in ash content with a high recovery of combustible matter than that of raw coal. The ultra clean coal with 0.5 % ash and 86 % recovery of combustible matter was produced by a combination of three treatments such as the HWD, 3-stage flotation and chemical cleaning.

Distribution behavior of collector in the desilication system of bauxite flotation

The distribution behavior of the HZB collector (a kind of long chain fatty acid) in the desilication system of bauxite flotation was studied. The results show that the collector tends towards froth products in the steps of the roughing, the first cleaning and the second cleaning, while towards the tailing product in the step of the scavenging, and in each job except scavenging the collector is mainly on the surface of solids. As for the froth product in the step of the scavenging, it is mainly in solution. To the tailing products of every step, it is mainly in the respective solutions. The collector added to the flotation system is mainly taken out by the last concentrate, by which the taken one occupies 65.2% of the whole, among which, 57.8% is by solid and 7.4% by solution, respectively. And the one by the last tail occupies 34.8% of the whole, among which, 8.8% is by solid and 26.0% by solution, respectively. The sum of the collector in the solution of the last concentrate and tailing is 33.4% of the amount of addition collector, and recycling the solutions will be in favor of decreasing the dosage of collector.

高硫黄石炭ずりからの鉄溶出特性と浸出水を用いた石炭脱硫浮選

The effects of inhibitors to iron-oxidizing bacteria (Thiobacillus ferrooxidans) on the dissolution of iron species from high sulfur coal refuse (5.75 db% S) were studied in acidic solutions with the bacteria, using sodium lauryl sulfate (SDS) and tannic acid as inhibitors. Flotation experiments of high sulfur coal (4.27 dafb% S) in leachates from the refuse were conducted to remove sulfur.Compared with tannic acid, SDS inhibited the iron-oxidizing activity of Thiobacillus ferrooxidans more and dissolution of pyrite in high sulfur coal refuse, but SDS did not prevent dissolution of soluble iron species in the refuse even at high addition rates, and pH values of the leachates were very low. When adding CaO, CaCO3, and limecake (byproduct of sugar making), dissolution of iron was completely suppressed and the pH values were about pH 8.Flotation of the high sulfur coal was conducted in the leachate of high sulfur coal refuse, which was prepared by Thiobacillus ferrooxidans to contain about 0.01 mol / dm3 soluble iron (almost all ferric ions) and adjusted to pH 2.5. Coal was selectively recovered as a froth product with high combustible recovery and high pyrite rejection.

First-order flotation kinetics models and methods for estimation of the true distribution of flotation rate constants

To improve their versatility, many first-order flotation kinetics models with distributions of flotation rate constants were redefined so that they could all be represented by the same set of three model parameters. As a result, the width of the distribution become independent of its mean, and parameters of the model and the curve fitting errors, became virtually the same, independent of the chosen distribution function. For the modified three-parameter models, the curve fitting errors were much smaller and their robustness, measured by PRESS residuals, was much better when compared to the corresponding two-parameter models. Three different methods were compared to perform flotation kinetics analysis and estimate model parameters. In Method I, recovery vs. time data were used to obtain model parameters. No significant insight into the distribution of rate constants could be obtained because the distributions were presupposed. In Method II, the froth products were fractionated into several size fractions and the data for each fraction were fitted to a model. This task was easy to perform and the method could describe the flotation kinetics reasonably well. In method III, flotation products were fractionated into many size-specific gravity fractions. The procedure involved a large amount of time and effort and it generated relatively large errors. Based on the analysis presented in this article, it was concluded the smallest errors were obtained with Method II. The overall distribution of flotation rate constants could be obtained from a weighted average of the distributions of individual size fractions. The distributions so obtained were demonstrated to be less sensitive to the choice of the model used to represent the kinetics of individual size fractions, and therefore can be assumed to be “true” representation of the flotation rate distribution.

Desulfurization of coal by microbial flotation in a semicontinuous system

A microbiological flotation system that facilitates the removal of pyritic sulfur from coal is reported. The chemoautotrophic bacterium Thiobacillus ferrooxidans is utilized as a pyrite-selective biological surfactant that augments the flotation-mediated rejection of pyritic sulfur. The bacteria were produced by continuous cultivation in 50-L tanks, where it was possible to produce 3.8 × 1012 cells/day when the dilution rate was optimal and the pH was 1.6, a condition that prevented ferric precipitation. Prior to flotation, the bacteria were mixed with coal, which allowed cells to selectively adhere to the pyrite. The adherence of bacteria made the pyrite surfaces more hydrophilic, which facilitated separation by increasing the tendency of pyrite to sink, while the hydrophobic coal floated. When a synthetic coal/pyrite mixture (10.1% sulfur) was subjected to microbial flotation, the level of sulfur rejection was stable during the entire period of operation (i.e., one hour). In the absence of bacteria, flotation reduced the sulfur content of a coal/pyrite mixture to within the range of 6.7% to 7.4%, with the combustible recoveries ranging from 93.9% to 99.0%. In the presence of bacteria, the sulfur content of cleaned coal was in the range of 1.3% to 1.4%, with the combustible recoveries ranging from 80.8% to 86.3%. Bacterial activity accounted for 57% of the total sulfur rejected through flotation. The desulfurization capacity of the system was further confirmed by testing it with run-of-mine coal. The pyritic sulfur content was reduced from 2.9% in the feed coal to around 1.2% in the froth product, while 80% of the combustible recovery was retained. Microbial flotation removed 60% of the pyritic sulfur from the feed. These findings demonstrated that microbial flotation could be utilized for the removal of pyritic sulfur from coal in a semicontinuous system.

Effects of Polymers and Metal Ions on Vacuum Filtration of Fine Coal

Surface modification approaches have been investigated in vacuum filtration of column flotation froth products of high and low sulfur coal slurries. It was shown that vacuum dewatering of fine coal can be enhanced significantly in terms of both filtration rate and cake moisture by modifying surface properties of fine coal particles with polymeric flocculants and metal ions. As expected, use of cationic or anionic flocculants significantly increased filtration rate. Addition of 5 g/t cationic flocculant to the high sulfur clean coal slurry lowered cake moisture from 26% to 22.3% and increased cake thickness from 5 to 10 mm, however, use of 25 g/t cationic flocculant increased cake moisture to 26.3% at increased cake thickness of 24mm. When cake thickness was maintained constant, use of anionic flocculant significantly reduced cake moisture. Cake moisture was reduced from 27.3% to 18.8% with the low sulfur coal using 25g/t anionic flocculant at cake thickness of 7 mm. Use of metal ions showed less significant effects on fine coal filtration. Mechanisms responsible for observed improvement in fine coal dewatering behavior have been discussed from the perspectives of filtration fundamentals.

Froth flotoextraction, a new method of metal separation from aqueous solutions

A new method of extraction and separation of metals from aqueous solutions, referred to as `froth flotoextraction', is proposed. This method combines two well-known processes: solvent extraction and froth flotation. Extraction is performed by an organic acid extractant at pH values characteristic for each metal, froth is formed by the extract, air bubbles transport the extract phase to the froth and at the same time mix the solution. The method combines high productivity and low cost of flotation with selectivity and low residual metal content of solvent extraction. An equation describing phase separation efficiency is proposed and used for optimization of the process. The method is tested and used in the industrial technology of water recycling in a Russian chemical plant. The final operations of the technology are solvent extraction purification of two froth products containing zinc and copper to produce their sulphates of `chemically pure' grade and flotation decontamination of the recycling water from the residual extractant.

Coal Flotation Washability: An Evaluation of theTraditional Procedures

The characteristic separation performance achievable from the treatment of fine coal using a froth flotation process is commonly estimated using either the release or tree analysis procedure. The two flotation characterization procedures differ substantially in the method of achieving selectivity between particles having varying degrees of hydrophobicity. From the treatment of -180 μm coal, the separation performance curves generated using the release analysis method were superior to those produced by tree analysis on the basis of both product ash and total sulfur contents. However, after grinding to reduce the amount of middling particles, the separation performance achieved by the tree procedure on the basis of product ash content was nearly equal, and in some cases, exceeded the performance provided by release analysis. In terms of product total sulfur content, the results obtained from release analysis remained superior. The differences in the separation performances achieved from the two flotation characterization methods are a result of the presence of middling and coal pyrite particles, which degrade the froth product upon flotation. Improvements in the two traditional procedures, such as the use of high feed solid concentrations to ensure a significant amount of selective reflux between the froth and collection zones, are presented in this publication.

微粒石炭浮選における脱灰性の評価と単体分離度の推定

The authors have developed a new method to evaluate coal flotation behavior. The liberation degree of mineral matter in feed and the ultimate ash content of froth product can be estimated using this method. Modified release analysis and oil agglomeration tests were carried out using different feed size of coal. The results were plotted on combustible recovery vs. ash content of clean coal curves and on combustible (or mineral matter) recovery vs. yield curves. Graphic analysis of these curves is proposed to give the ultimate ash content of coal concentrate obtained under ideal conditions and the liberation degree of mineral matter of flotation feed. By comparing these curves with conventional flotation results, the mass of mineral matter entrapped mechanically in froth was determined. In this paper the above procedures are described in detail using Datong coal. The ultimate ash content decreased and reached about 1 % with decreasing average feed sizes, smaller than 2μm, and the liberation degree increased to above 90 %. The mass of entrapped mineral matter increased drastically for feed smaller than 20μm.

97/01642 Present-day trends for production of smokeless briquetted fuel for compact units and household stoves

Comparison of gravity-based washability curves with flotation results indicates that gravity-based processes are always more efficient, especially at treating coals with a significant yield of middlings. Because of bubble attachment to the hydrophobic (coal) portion of the particle, a particle containing as little as 5% coal may still report to the froth product. Therefore, for coal fines having high middlings content, a high combustible recovery commonly results in high ash and sulfur levels in the flotation products. Although the gravity methods are not very efficient in handling very fine particles, incorporation of gravity separators along with flotation into the fine-coal processing circuit is still the best solution. The coal flotation process is based on differences in surface properties between hydrophobic coal particles and hydrophilic high-ash refuse. Coals of various ranks have different chemical compositions and physical structures and as a result their surface properties and floatability change with coalification. While metallurgical coals float easily and may only require a frother, flotation of lower-rank bituminous and subbituminous coals may be difficult. A new multiunit fine-coal cleaning circuit has been developed at the Center for Coal and Minerals Processing (CCMP at Virginia Tech, Blacksburg, Va.). The circuit consists of a Microcel flotation column and a Mozley Multi-Gravity flowing film separator (MGS). The Microcel column uses small air bubbles to improve the flotation recovery of fine coal, while the MGS utilizes centrifugal forces to enhance the gravity separation of fine pyrite.

A feed-line aerated flotation column Part I: Batch and continuous testwork

A systematic procedure has been developed for feed-line aerated flotation column evaluation in laboratory and plant. Slurry in batch operation is continuously recirculated from the column bottom through an external aerator and then incremental froth products are collected. In continuous operation, a grade-recovery curve is generated by changing feed and gas rate. The selectivity data from these two modes of column operation are compared. The experimental procedures are described in this paper with an example application to chalcocite-heazlewoodite separation at INCO's Matte Separation plant. The significance of the experimental procedure for column design and scale-up as well as general column testwork is discussed.

96/01237 Recovery of anthracite from coal preparation-plant tallings

Comparison of gravity-based washability curves with flotation results indicates that gravity-based processes are always more efficient, especially at treating coals with a significant yield of middlings. Because of bubble attachment to the hydrophobic (coal) portion of the particle, a particle containing as little as 5% coal may still report to the froth product. Therefore, for coal fines having high middlings content, a high combustible recovery commonly results in high ash and sulfur levels in the flotation products. Although the gravity methods are not very efficient in handling very fine particles, incorporation of gravity separators along with flotation into the fine-coal processing circuit is still the best solution. The coal flotation process is based on differences in surface properties between hydrophobic coal particles and hydrophilic high-ash refuse. Coals of various ranks have different chemical compositions and physical structures and as a result their surface properties and floatability change with coalification. While metallurgical coals float easily and may only require a frother, flotation of lower-rank bituminous and subbituminous coals may be difficult. A new multiunit fine-coal cleaning circuit has been developed at the Center for Coal and Minerals Processing (CCMP at Virginia Tech, Blacksburg, Va.). The circuit consists of a Microcel flotation column and a Mozley Multi-Gravity flowing film separator (MGS). The Microcel column uses small air bubbles to improve the flotation recovery of fine coal, while the MGS utilizes centrifugal forces to enhance the gravity separation of fine pyrite.

96/01240 Relation between swelling of lignites and the characteristics of swelling agents

Comparison of gravity-based washability curves with flotation results indicates that gravity-based processes are always more efficient, especially at treating coals with a significant yield of middlings. Because of bubble attachment to the hydrophobic (coal) portion of the particle, a particle containing as little as 5% coal may still report to the froth product. Therefore, for coal fines having high middlings content, a high combustible recovery commonly results in high ash and sulfur levels in the flotation products. Although the gravity methods are not very efficient in handling very fine particles, incorporation of gravity separators along with flotation into the fine-coal processing circuit is still the best solution. The coal flotation process is based on differences in surface properties between hydrophobic coal particles and hydrophilic high-ash refuse. Coals of various ranks have different chemical compositions and physical structures and as a result their surface properties and floatability change with coalification. While metallurgical coals float easily and may only require a frother, flotation of lower-rank bituminous and subbituminous coals may be difficult. A new multiunit fine-coal cleaning circuit has been developed at the Center for Coal and Minerals Processing (CCMP at Virginia Tech, Blacksburg, Va.). The circuit consists of a Microcel flotation column and a Mozley Multi-Gravity flowing film separator (MGS). The Microcel column uses small air bubbles to improve the flotation recovery of fine coal, while the MGS utilizes centrifugal forces to enhance the gravity separation of fine pyrite.

The effect of some design and operating parameters in the cyclo-column cell

Cyclo-column cell is a flotation device which makes use of centrifugal force for bubble-particle contact and incorporates a froth column with optional wash water to provide a clean froth product. In this study, the influence of certain design and operating variables (froth column type, number of feed pumps, inset length, froth column height, air flowrate and wash water) on the performance of the cyclo-column cell was examined. It was found that the froth product obtained from the device could be rendered substantially cleaner by employing an expanded froth column which permits effective drainage of pulp from the froth and minimizes entrainment of undesired minerals. For example, in the reverse flotation of a magnetite ore, the froth product (tailings) grade dropped from 15.07% Fe in the case of a straight froth column to 8.72% Fe with an expanded froth column of the same height. Application of wash water resulted in a further reduction of about 1.4% Fe in tailings grade. The use of a single feed pump, as opposed to two pumps working in series, produced a cleaner froth product but at a lower throughput. A froth column height of 205 mm and an inset length of 20 mm were found to be satisfactory; and an air flowrate of 20–25 scfh produced the best results in terms of tailings grade and flotation rate.

The potential for reagent recycle in the ion flotation of gold cyanide — a pilot scale field trial

The paper describes the work undertaken during a pilot scale field trial of the ion flotation process, as applied to the recovery of gold. In this process the gold cyanide anions of a heap leach liquor are adsorbed, through the use of a cationic surface active reagent, on the surface of rising air bubbles and recovered as part of a froth product concentrate. The principal objectives of the trial were to establish the technical feasibility of long-term reagent recycle and to quantify the recyclability of the reagent, an essential specification in the determination of the economic viability of the technology which could not be sensibly established at the laboratory scale. The trial involved a total of 13 reagent recycle stages. The results indicated that the recyclability of the reagent is about 80%.

石炭の浮遊性と脱灰性に及ぼす二酸化炭素の影響 大同炭，ワンドワン炭，イリノイ炭の場合

Three coals from different localities (Datong, Wandoan and Illinois) were used in this study. Immersion time measurements were carried out to assess wettability of coal surface using 100-200 mesh coals. Flotation tests were conducted by introducing air, nitrogen and carbon dioxide gases, respectively. After sparging the gases into coal slurries, the slurries were chemically analyzed. For flotation and chemical analysis fine coals (mean particle size: about 30 pm) were used. Some of the coals were treated with 0.6 kgf/cm2 of carbon dioxide gas prior to the experiments. The collectors used were kerosene for Datong coal and heavy oil A for the other coals.The hydrophobicity of three coals treated with carbon dioxide became slightly higher than that of untreated coals. When sparging carbon dioxide gas, the highest amounts of calcium and magnesium were dissolved from Datong and Wandoan coals and the amounts of bassanite and calcite in the coals were simultaneously decreased. By flotation with carbon dioxide, the maximum yield was obtained for the coals treated with carbon dioxide than the untreated coals, but the ash content of the froth products was high. For these froth products cleaner flotation with frother alone was carried out, and the ash content of clean coals was improved for Datong coal but not for Wandoan and Illinois coals. This was mainly caused by the difference in the liberation degree and flotation behavior of mineral matters in the coals, and the difference in the collectors used.

Ion flotation - potential applications to mineral processing

The technique of ion flotation provides a simple physical method for concentrating the ions present in very dilute liquors. The ions in the liquor, with the aid of a suitable surfactant, adsorb at the surface of rising air bubbles, and report to a froth product. The purpose of this article is to provide the mineral processing industry with a structured and up to date review of the ion flotation subject, to examine some recent developments, and to indicate some potential applications of the technique. Following a discussion of the ion flotation phenomenology and general nomenclature, important issues concerning the product grade, the selectivity of reagents, flotation kinetics, and other operating variables are examined. Finally, the potential applications of ion flotation are discussed, and an economic analysis of a gold ion flotation process is presented. The main conclusion is that developments in ion flotation will occur in areas such as gold recovery and mine-site remediation. Here, the benefits offset the risks associated with the introduction of this, essentially, new technology.

Entrainment of fine hydrophilic particles by granulometric separation

A model mechanism is proposed for the separation effect in the method of extraction of fine particles by foaming of a suspension. The particles captured in the boundary layers of the rising bubbles are lagging behind the major fluid motion. This effect modifies the forces acting on them and leads to radial ejection off the surface of the bubble. For smaller fractions ( R p∼1–10 μm) the ejection is insignificant, but it increases substantially for larger radii. Thus only the tiny particles are extracted in the froth product, where the larger fractions ( R p≥25 μm) are almost absent.

A Wastewater Treatment System Applying Aeration-Cavitation Flotation Mechanism

Abstract A new type of wastewater treatment system applying not only aeration but also the cavitation flotation mechanism is proposed to attain high capacity and low operation cost. The system can be operated continuously in a single or multistage with ease. The system is composed of four isolated sections: feed section, aeration section, multiphase flow section, and separation section. Aeration and gas dissolution are carried out in the aeration section. Then collisions between the elements to be removed and gas bubbles, and cavitation of dissolved gas are accomplished in the multiphase flow section, followed by the recovery of the aggregates as the froth product in the separation section. The function of each section is evaluated by taking into consideration the contribution to the separation characteristics. It is confirmed through a series of treatment tests that the separation rate is a few tens of times faster than those in conventional treatment systems and, hence, lower energy consumption is anticipated in the proposed system.