Influence of chemical parameters on selectivity and recovery of fine coal through flotation (original) (raw)
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Effective flotation of weathered coal using frother blend
2013
Froth flotation of weathered coal is a challenging task in a conventional flotation cell using commonly used collector and frother. Generally weathered coal shows the erratic flotation behaviour due to the surface oxidation as it makes the coal surface hydrophilic. When the surface gets oxidized, surface modifier is employed to float the clean coal. Frothers play significant role in stabilizing the mineralized bubble. It reduces the bubble size by reducing the interfacial tension at the air water interface. During this investigation, the flotation was carried out with two types of frothers namely; methyl isobutyl carbinol (MIBC), a weak frother and a strong polyglycol type. The Factorial design matrix was used for carrying out the experiments with the different ratio of frother blend, collector and promoter dosage. The high concentration of MIBC is found to be not effective for recovering the significant amount of carbon value as it causes less reduction of the interfacial tension a...
The effect of reagents and reagent mixtures on froth flotation of coal fines
International Journal of Mineral Processing, 2003
Reagent usage and type of reagent are important factors in froth flotation. The recovery and purity of the final product obtained depend on various parameters such as the type and the amount of reagent, the nature and the particle size of solids, the adsorption of reagent on solid particle surface. The froth flotation tests of bituminous coal fines were carried out using only one of three non-ionic reagents; Triton x-100, Brij-35, methyl isobuthyl carbinol (MIBC) and sodium dodecyl sulfate (SDS), and the mixture of Triton x-100 or Brij-35 with MIBC in various ratios. The froth flotation performance was changed significantly according to addition of the reagent or reagent mixtures. The highest recoveries (>90%) were achieved in the presence of conventional reagents, MIBC or SDS. However, the ash rejection values were lower in the use of the same reagents. The ash rejection was considerably improved by using the mixture of reagents. A strong relationship was observed between the solid fraction in the concentrate and the type and amount of the reagent or the reagent mixture. The combustible solid recovery and the ash rejection strongly depend on the finer particle fraction in the feed.
Study of interactions of frother blends and its effect on coal flotation
Powder Technology, 2014
Frothers are surface active molecules and facilitate to produce more mechanically stable froth by reducing the surface tension at air-water interface. It adsorbs at the air-water interface and serves to reduce the loss of water from the lamellae of bubble. In this investigation weak and powerful frothers, like methyl isobutyl carbinol (MIBC) and polyethylene glycol-600 (PEG) were used for studying the surface tension of frother blends at various concentrations. Gibb's surface excess adsorption and surface area were determined from the rate of change of surface tension with logarithm of concentration. The high surface area per molecule of PEG signifies that little amount is enough to significantly reduce the interfacial tension at the air-water interface. The foam volume and its stability were measured for single frothers and their blend. The foam stability (foaminess) of single MIBC is very less however; it could be improved significantly using a small amount of strong frother (PEG). Flotation studies of coal fines from eastern part of India were carried out with the above two types of frothers and their blend. The performances were compared with reference to recovery of combustibles for clean coal and rejects. It was found that coal concentrate contains high ash with single PEG due to high froth stability that results the entrainment of the gangues, while single MIBC produces high grade concentrate with low recovery. It was observed that the recovery of carbon value increases significantly when a 10% (w/w) of powerful frother was added with MIBC. The recovery of carbon at 90:10 ratio of frother blend is 77.6% at 17% ash. The recovery could be increased to 86% when ash in clean coal increases to 19.7% and loss of combustibles in the tailing could also be reduced to 14%.
Mechanism of fine coal flotation using insoluble collectors in the presence of frothers
RESOURCES PROCESSING, 1997
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. INTRODUCTION Gravity coal beneficiation techniques are fairly unproductive fine coal processes. Hence, flotation, selective flocculation and selective agglomeration are widely used in fine coal processing. A satisfactory number of studies on fine coal flotation have been reported [1-4]. However, relatively few studies have been dedicated to the action and mechanism of flotation reagents in coal flotation [5, 6]. With recent increased public awareness of environmental problems and with increasing legislation, it is becoming even more important to control mine disposal. Approximately 10 mill. tones of dirt and waste fine coals will be disposed from EL Maghara mine as a result of coal preparation and mining operations [7]. Hence, significant amounts of coal would be lost each year, as fines and ultrafines. Therefore, to increase the commercial value of such coal, methods must be found to effectively separate coal fines from associated shale and other containing minerals. The reclamation of such fine-size waste would eliminate many of the environmental problems and would result in conservation and development of additional natural resources in Egypt. Froth flotation is a unit operation that has found its greatest application in the mineral industry for separation finely divided solid particulate dispersed in aqueous sus
Powder Technology, 1995
In the froth flotation of ultra-fine particles, the recovery and purity of the final product obtained depend largely on the froth structure, which in turn is affected by reagent adsorption on the solids. In this study, ultra-fine particles (5 /.Lm size fractions) of two low rank British coals were used in the flotation tests. The tests were carried out using only one of two different non-ionic reagents; diacetone alcohol and 2-ethyl hexanol. The froth structure can be changed significantly by addition of reagent. It was observed that when the froth structure changes from a spherical to a polyhedral structure that the flotation performance changes significantly. Previous measurements of the internal pore distributions showed marked differences between the Rawdon and Bickershaw coals. Also the flotation performance of each coal differed significantly according to the reagent used. It is postulated that the differing behaviour of the coals can be attributed to the fractional amount of the total reagent adsorbed on the interior pore surfaces.
Experimental Investigation on Safer Frother Option for Coal Flotation
Current Works in Mineral Processing
This work aimed to investigate a safer frother for coal flotation with achieving similar or better flotation performance, compared with the most common frother methyl isobutyl carbinol (MIBC) that caused some fire hazards in the past due to its low flash point (F.P. = 39 °C). Based on the higher flash points and low risk rating according to their safety data sheet, Dow Froth 250 (F.P. = 149 °C) and pine oil (F.P. = 78 °C) were selected to test against MIBC. Flotation tests were carried out at various frother dosages with/without diesel as a collector. Both Dow Froth 250 and pine oil had a good potential to be a safer alternative to MIBC in terms of coal grade and recovery. Pine oil was the most promising as a stand-alone reagent without a collector potentially making for a safer work environment with less chemical storage.
Coal Froth Flotation: Effects of Reagent Adsorption on the Froth Structure
Energy & Fuels, 2006
The amount and quality of concentrate obtained from froth flotation of a coal are very important to determine the efficiency of the separation process. The shape and size of the bubbles in the froth directly affect the amount and purity of the concentrate overflowed during the froth flotation of the coal. The froth structure is significantly dependent on parameters such as the size of the solid particles, the surface properties of the particles, the chemical structure of surface active agents, the reagents adsorbed onto solid particles, and the reagents remaining in water. This work was performed to determine the relationship between the reagents adsorbed on the solid particles, froth structure, and froth flotation performance. The-53 µm size fraction of a bituminous coal was used to perform froth flotation experiments. The froth flotation of the coal used was performed in the presence of two nonionic surfactants, Triton x-100 (poly(ethylene glycol) tert-octylphenyl ether) and MIBC (methyl isobutyl carbinol), and an anionic surfactant, SDS (sodium dodecyl sulfate). The results showed that the adsorption of a high amount of reagent on the particles decreased the ability of separation, thus a substantial amount of mineral particles overflowed along with the hydrophobic coal particles. The use of MIBC with Triton x-100 or SDS as mixture increased solid recovery, and it was concluded that MIBC selectively adsorbed on solids acting as collector as well as a frother. Reagent adsorption has a crucial effect on the froth structure, which is strongly related to flotation performance.
The effect of reagent addition strategy on the performance of coal flotation
Minerals Engineering, 2004
The recovery and grade of concentrates obtained by flotation is partly dependent upon froth structure. The flotation froth structure can be modified, and hence the flotation performance modified, by the addition of reagents. A direct control system was developed which permitted predetermined addition profiles of reagent and water to be added to a cell. A series of experiments were performed using different strategies of reagent (Triton x-405) addition for the flotation of Bickershaw coal. A transputer enhanced Micro-Vax Computer was employed to grab images of flotation froths and to process them quantitatively in a parallel procedure. Using image processing techniques characterization of froth structures was achieved. The image processing procedures that were intended to run on-line, were examined and developed using video tapes of experimental runs, off-line. An essential stage in the development of such a system is the understanding of the adsorption behaviour of the reagent in terms of the kinetics, the distribution of reagent between the solid and solution phases, and the resulting effect on the froth structure. A kinetic model was developed to describe the adsorption of the reagent on the particles. The experimental recoveries and froth structure were investigated in terms of reagent distribution and the froth structure.
Safer Frother Option for Coal Flotation – A Review
Current Works in Mineral Processing
A safer frother option for coal flotation in comparison with the common frother methyl isobutyl carbinol (MIBC) was searched and compared through literature review. Results of literature review and comparison of different frothers in safety and environmental aspects show that pine oil and DowFroth have a strong potential to replace MIBC since it has high flash point (78 °C, 149 °C, respectively), and dual frothing and collecting properties to be used as a stand-alone reagent for coal flotation. It can significantly reduce the risk of potential hazard associated with MIBC and oil collector.
Removal of Impurities from Indigenous (Chamlang) Coal by Using Froth Flotation Technology
Pakistan Journal of Scientific & Industrial Research Series A: Physical Sciences, 2019
Indigenous (Chamlang) coal possesses excessive concentrations of impurities, such as ash and organic and inorganic sulphur. In the present research froth flotation technique was applied for reducing inorganic sulphur and ash content in coal. Frothing agent, pH, separation time and air velocity were the main parameters employed to reduce ash content in the indigenous coal. The optimum values of flotation parameters by including pH, air velocity and separation time were found to be 7, 90 scf/h and 55 min. Keeping parameters at their optimum values, better quality of coal was obtained by reducing ash and sulphur content to 57 and 50.757% respectivety.