Fine Coal Flotation Research Articles

98/00068 Froth flotation of coal fines using alkaline diesel-oil waste as the collector

98/00068 Froth flotation of coal fines using alkaline diesel-oil waste as the collector

97/03478 Advanced froth flotation techniques for fine coal cleaning

Advanced column flotation cells offer many potential advantages for the treatment of fine coal. The most important of these is the ability to achieve high separation efficiencies using only a single stage of processing. Unfortunately, industrial flotation columns often suffer from poor recovery, low throughput and high maintenance requirements as compared to mechanically-agitated conventional cells. These problems can usually be attributed to poorly-designed air sparging systems. This article examines the problems of air sparging in greater detail and offers useful guidelines for designing bubble generators for industrial flotation columns. The application of these principles in the design of a successful advanced fine coal flotation circuit is also presented.

97/02429 Initial testing of a dynamic column for fine coal flotation

This paper describes the design and initial performance of a dynamic column for fine coal column flotation. A dynamic column is a modified conventional column with the insertion of a series of draft tubes that provide individual mixing stages. The mixing is beneficial in generating small and uniform bubbles over a wide range of frother dosages. It is also beneficial in the control of flotation where the fluctuation of froth volume should be minimized. In the modified design, a vortex-inducing plate is attached to the top of each draft tube to create an artificial vortex. In theory the vortex action is desirable for collecting the light clean coal froth within the inner mixing zone, and for passing it upward to the next draft tube stage. The mineral laden slurry, particularly the pyrite, is accelerated outside the vortex zone by centrifugal force to reach the wall where it is carried downward to the bottom of the column. The draft tubes are arranged in a series to accomplish multistage cleaning. The experimental results showed that this dynamic column has the potential advantage of higher throughput and better product recovery as well as improved product quality.

Mechanism of fine coal flotation using insoluble collectors in the presence of frothers.

This paper deals with the application of froth flotation techniques to the beneficiation of fine waste coal of El-Maghara colliery. Different reagent systems of oily collector-frother were investigated. The main object of this study is to investigate the feasibility of recovering the combustible matter from waste fine coal. The attention is also paid to highlight the oily collector-frother interaction.

96/04680 Possibilities of raising the rate of fine coal flotation

96/04680 Possibilities of raising the rate of fine coal flotation

Image analysis characterization of pyrite in fine coal flotation

Image analysis characterization of pyrite in fine coal flotation

Applicability of the Reichert spiral for cleaning bituminous and lignitic coals: a pilot scale study

The Reichert spiral which has been particularly developed for the beneficiation of fine coal in the size range of −3 + 0.1 mm is considered as an alternative for fine coal jig, cyclone, and flotation. A systematic study has been carried out to test the separation efficiency of the Reichert spiral on a bituminous coal and lignite. The effect of particle size, pulp density, the presence of fines, and the number of cleaning stages has been studied as a function of separation density. It is shown that cleaning of coal at densities below 1.5 g/cm 3 seems inefficient under optimum operating conditions. The Reichert spiral is capable of cleaning the bituminous coal more efficiently than lignite in view of the smaller number of cleaning stages. Lignite, however, requires lower separation densities compared to the bituminous coal. The effect of various parameters on spiral performance is delineated with the aim of developing an optimum strategy for cleaning low quality coals.

Image analysis characterization of pyrite in fine coal flotation

The flotation behavior of a −28 mesh Pittsburgh No. 8 coal sample is investigated through the use of Scanning Electron Microscopy in conjunction with Image Analysis. Release analysis is used to generate the flotation products, which are then characterized to provide the particulate composition in terms of pyrite, mineral matter and carbonaceous material. The results of this investigation indicate that the material recovered in the first stage of release analysis tends to be well-liberated carbonaceous material. This is followed by an increase in the recovery of middlings and fines in the later stages of the process. Any free carbonaceous material remaining in the tailings from the release analysis test tends to be associated with the very fine sizes (−400 mesh). Pyrite recovery is attributed to the hydrophobicity provided by small inclusions of carbonaceous material, since the amount of truly liberated pyrite particles (i.e., 100% pyrite) present in the sample is found to be negligible.

Comparison of bubble generating devices for column flotation of fine coal from refuse

Column flotation testing was conducted on the flotation feed slurry obtained from a preparation plant located in the Southern Illinois coal basin. The column flotation tests were conducted using three different bubble generating devices: a static sparger, a gas saver and a foam jet. Each of these devices was tested with three different types of frother and various column operating variables to provide maximum combustible recovery, minimum product ash and maximum pyrite rejection. The results show that column flotation provided improved flotation performance, in terms of combustible recovery as well as ash and pyrite rejection, for each of the bubble generating devices. However, the effectiveness of each bubble generating device was dependent on the type of frother used. Alcohol frothers were most effective for use with the static sparger, somewhat less effective for the foam jet and ineffective for the gas saver. Glycol frothers were effective for all three bubble generating systems, providing high combustible recovery (>90%); low clean-coal ash (4–6% ash) and high pyrite rejection (70–80%).

Dimensionless Analysis of Process Variables in Air-Sparged Hydrocyclone ( ASH ) Flotation of Fine Coal

Abstract Fine coal cleaning by froth flotation in a 2-inch air-sparged hydrocyclone (ASH) has been investigated and the effects of important design and operating variables on separation efficiency examined. In order to reduce the complexity of the analysis, the flotation performance of the air-sparged hydrocyclone was studied by dimensionless analysis. As a result of these efforts, an empirical model was derived to predict the flotation effectiveness of the air-sparged hydrocyclone unit of various levels of design and operating variables, thus allowing for optimization of the flotation separation. Since the model is based on dimensionless analysis, it is anticipated that subsequent development efforts to scale-up the ASH flotation system for industrial utilization will be facilitated

Packed-Bed Column Flotation of Fine Coal. Part II. Technical — Economic Feasibility and Scale-up Considerations

An economic analysis revealed that the new packed-bed flotation column is superior to conventional flotation cells for reduction of ash and pyritic sulfur. Furthermore, commercial packed-bed flotation columns can be designed on a direct scale-up basis.

Improved Pyrite Rejection by Chemically-Modified Fine Coal Flotation†

Abstract Improved pyrite rejection during fine coal flotation can be achieved by chemical pretreatment of the coal prior to flotation. The process involves conditioning the suspension with potassium monopersulfate or other peroxy compounds followed by conventional flotation. The ambient-temperature treatment seems to improve the hydrophobic character of certain low-rank coals as is evident from induction time measurements and bench-scale flotation experiments. In addition, the chemical pretreatment leads to an improvement in ash rejection and to enhanced depression of pyrite.

Staged flotation of fine coal and the effects of mineral size and distribution

Etude experimentale du procede etage de flottation par mousse de fines particules de charbon. Comparaison avec d'autres procedes d'epuration

The Effect of Bubble Size on Fine Coal Flotation

To better understand the fundamental steps involved in the froth flotation process, the probability of collection has been determined for the flotation of a very hydrophobic, ash-free coal sample. The results show that probability of collection increases rapidly with decreasing bubble size, and the values are in good agreement with the theoretical collision probabilities predicted from Weber and Paddock's analysis. In the present work. Weber and Paddock's model has been expanded to predict the flotation rate constant as a function of bubble size and other operating variables. The flotation rate constants, determined experimentally using a run-of-mine coal, have been found to exhibit the same power dependence of bubble size as predicted by the model, but the values are lower than predicted by approximately 50%. This discrepancy may be attributed to the high ash content of the coal (15.5%) and, hence, a low probability of adhesion.

Synergistic Effect of Frother on Coal Flotation

Overall response to flotation of coal fines is improved by using mixtures of pine oil and methyl isobutyl carbinol as frother instead of either of them alone. Measurements of static froth height and surface tension of aqueous solutions of the frother are used to study the synergistic effect and to arrive at an optimum frother composition. The observations made in these studies are confirmed by flotation tests with coal fines from a coking coal washery using flotation columns of 100 and 220 mm diameter operating at nominal capacities of 20 and l00 kg hr−1 respectively.

Effects of surface chemistry and particle size and density on froth flotation of fine coal

This paper reports the effects of surface chemistry and particle size and density on the froth flotation of fine coal. It is shown that froth flotation of very fine coal particles (up to 12 μm) can be readily accomplished in a mechanical-type flotation cell. In addition, the coal particle surface, though primarily hydrophobic, consists of hydrophilic sites such as minerals, hydroxyl and carboxyl groups. The flotability of the coal increases as the surface hydrophobicity increases, but decreases as more hydrophilic sites become ionized. The lower flotability for particles of high mineral content is further attributed to the density effect. Thus, clean coal particles can be selectively froth floated while leaving particles of a high mineral content in the tailings. The selectivity deteriorates as the average particle sizes are reduced from 75 to 12 μm. The selectivity problem can be partially overcome, however, through the use of an anionic collector and staged froth flotation.

Fine coal flotation with alcohol: Dialkyl sulfosuccinate frothing systems

This paper confirms a general relationship between static frothing efficiency and batch flotation recovery when the alcohol methylisobutylcarbinol (or 4-methyl-2-pentanol) (MIBC) is employed as the frothing agent in the flotation of fine coal. When sodium di-isobutyl sulfosuccinate (DIBSS) is employed in combination with MIBC, maximum recovery and grade are obtained at much lower reagent usage than with MIBC alone. The mixture also provides greater tolerance to water quality than the alcohol alone.

Froth‐flotation reagents for coal: Distillation fractions of commercial oils and some simple phenolic compounds

AbstractThree commercial oils commonly used for the froth flotation of fine coal were fractionally distilled in a high‐efficiency laboratory column. When the individual fractions were tested for flotative power on Gresford and Bedlington fine coals, little variation was found, except that components boiling at temperatures below 180° or above 280° had less power than those in the middle range.Some 20 simple substituted monohydric phenols of known constitution were subjected to a similar evaluation. They fell into four groups of very different flotative power.Many physical properties of the fractions and of the phenols were measured. No correlation was found between flotation merit and boiling point, solubility, refractive index or dielectric constant of the reagent, or the surface tension and relative surface viscosity of its saturated solution in water. On the other hand, there was a strong indication that the degree of ionization is important, good frothers for coal having dissociation constants (Ka) less than 10−7 and non‐frothers greater than that value as a rule. The power of the phenols in small amount to reduce or refine the size of bubbles created in water by passing air through a porous disc was also shown to be directly related to their flotation merit.

Froth‐flotation reagents for coal: Distillation fractions of commercial oils and some simple phenolic compounds

AbstractThree commercial oils commonly used for the froth flotation of fine coal were fractionally distilled in a high‐efficiency laboratory column. When the individual fractions were tested for flotative power on Gresford and Bedlington fine coals, little variation was found, except that components boiling at temperatures below 180° or above 280° had less power than those in the middle range.Some 20 simple substituted monohydric phenols of known constitution were subjected to a similar evaluation. They fell into four groups of very different flotative power.Many physical properties of the fractions and of the phenols were measured. No correlation was found between flotation merit and boiling point, solubility, refractive index or dielectric constant of the reagent, or the surface tension and relative surface viscosity of its saturated solution in water. On the other hand, there was a strong indication that the degree of ionization is important, good frothers for coal having dissociation constants (Ka) less than 10−7 and non‐frothers greater than that value as a rule. The power of the phenols in small amount to reduce or refine the size of bubbles created in water by passing air through a porous disc was also shown to be directly related to their flotation merit.