Effects of simultaneous ultrasonic treatment on flotation of hard coal slimes

In this study, effects of simultaneous ultrasonic treatment on flotation of original and aged hard coal slimes were investigated with aiming to recover more combustible and good quality products. Conventional and ultrasonically assisted flotation tests of original and aged coal slimes were performed by using Montanol-531, a special coal flotation reagent, at variable dosages. The results of the batch flotation tests revealed that simultaneous ultrasonic treatment increased combustible recovery and lowered ash values of concentrates compared to the conventional flotation conditions despite using similar reagent dosages. These results were also verified by testing some physico-chemical properties of the samples, i.e. temperature, pH, oxidation-reduction potential, and zeta potential. Finally, it is concluded that a thorough surface cleaning by cavitation due to power ultrasound might improve the flotation recovery compared with the conventional flotation conditions, even though very slight changes were also observed in some physico-chemical properties of the treated samples. (C) 2011 Elsevier Ltd. All rights reserved

Further Investigations on Simultaneous Ultrasonic Coal Flotation

This study investigates the flotation performance of a representative hard coal slime sample (d80 particle size of minus 0.2 mm) obtained from the Prosper-Haniel coal preparation plant located in Bottrop, Germany. Flotation was carried out with a newly designed flotation cell refurbished from an old ultrasonic cleaning bath (2.5 L volume) equipped with a single frequency (35 kHz) and two different power levels (80-160 W) and a sub-aeration-type flotation machine operating at a stable impeller speed (1200 rpm) and air rate (2.5 L/min). The reagent combination for conventional and simultaneous ultrasonic coal flotation tests was Ekofol-440 at variable dosages (40-300 g/t) with controlling water temperature (20-25 degrees C) at natural pH (6.5-7.0). The batch coal flotation results were analyzed by comparing the combustible recovery (%) and separation efficiency (%) values, taking mass yield and ash concentrations of the froths and tailings into account. It was found that simultaneous ultrasonic coal flotation increased yield and recovery values of the floated products with lower ash values than the conventional flotation despite using similar reagent dosages. Furthermore, particle size distribution of the ultrasonically treated and untreated coals was measured. Finely distributed coal particles seemed to be agglomerated during the ultrasonic treatment, while ash-forming slimes were removed by hydrodynamic cavitation

Investigation of Humate Extraction from Lignites

The present study investigated the extraction of humate from low-quality lignite samples acquired from Malkara and Yatagan coal deposits in Turkey. The experiments were conducted on finely ground representative coal samples at atmospheric pressure and room temperature. The samples were first leached with concentrated nitric acid for up to 72 hours and undissolved solids were removed by filtration. Potassium hydroxide was added to the leachate for alkalization in order to produce nitro-humic acid solution at different pH levels. Humic matter precipitation was achieved by addition of diluted nitric acid. The extraction products were investigated by proximate, Fourier Transform Infrared Spectroscopy (FTIR), and elemental analyses. The most important factors affecting humate extraction were found to be the consumption of nitric acid dosage for coal leaching, pH value of the leachate after potassium hydroxide addition, and mixing time. The promising results with over 80% humate extraction were achieved for the Yatagan lignites when the acid-coal consumption ratio was less than 1 mL concentrated nitric acid per 1 gram coal at a pH of 9 with mixing for 48 hours, while Malkara lignites reached 70% humate extraction with 72 hours of mixing under the same conditions

Effects of Ultrasound on Desliming Prior to Feldspar Flotation

In this study, the effects of ultrasound on removal of impurities from raw feldspar were investigated by testing with a newly developed flotation cell with various frequency and power intensities prior to multistage feldspar flotation. Particularly, the quality of feldspar concentrates, the volume of removed slimes and the content of impurities were taken into account to reveal the impacts. Two representative feldspar ore samples taken from the Milas-Mugla region in Turkey were separately tested for desliming and flotation by conventional and ultrasonic methods under similar conditions and the results were compared to each other in terms of the quantity and the quality of the removed slimes and the final feldspar flotation concentrate. As a result, during desliming stage by using ultrasound, the volume of removed slimes was reduced by approximately 45% when compared to the conventional slime removal methods. Moreover, the impurity contents were doubled inside slimes when ultrasound was used. These outcomes lead to significant success in terms of reducing losses during the desliming stage and production of high quality feldspar concentrates by froth flotation assisted by ultrasound

Effects of Ultrasound on Desliming Prior to Feldspar Flotation

In this study, the effects of ultrasound on removal of impurities from raw feldspar were investigated by testing with a newly developed flotation cell with various frequency and power intensities prior to multistage feldspar flotation. Particularly, the quality of feldspar concentrates, the volume of removed slimes and the content of impurities were taken into account to reveal the impacts. Two representative feldspar ore samples taken from the Milas-Mugla region in Turkey were separately tested for desliming and flotation by conventional and ultrasonic methods under similar conditions and the results were compared to each other in terms of the quantity and the quality of the removed slimes and the final feldspar flotation concentrate. As a result, during desliming stage by using ultrasound, the volume of removed slimes was reduced by approximately 45% when compared to the conventional slime removal methods. Moreover, the impurity contents were doubled inside slimes when ultrasound was used. These outcomes lead to significant success in terms of reducing losses during the desliming stage and production of high quality feldspar concentrates by froth flotation assisted by ultrasound

Effects of temperature during ultrasonic conditioning in quartz-amine flotation

In this study, the effect of ultrasound on flotation recovery of quartz- amine flotation was investigated in terms of temperature influence. For this purpose, an ultrasonic probe was used for conditioning quartz surfaces in presence of dodecylamine hydrochloride ( DAH), and the change in the temperature was recorded. The temperature- controlled ultrasonic conditioning tests were also carried out at various ultrasonic powers ( 30, 90, and 150 W) to investigate the effect of increasing temperature on the quartz- DAH flotation. The results showed that temperature of the suspension sharply increased from 23 up to 75 degrees C at the end of 10 min of conditioning at 150 W ultrasonic power. The flotation results for the temperature controlled and uncontrolled samples indicated that the flotation recovery increased from 45 to 65% by 90 W ultrasonic power. However, higher ultrasonic power levels affected the flotation recovery negatively. On the other hand, the ultrasonic application decreased the flotation recovery at all ultrasonic power levels in the temperature- controlled tests. Finally, the shape analysis was also performed for the particles treated with the ultrasound at various ultrasonic powers. As a conclusion, the positive effect of ultrasound on the quartz- amine flotation recovery could be related to temperature increase during conditioning

Enhancement of galena-potassium ethyl xanthate flotation system by low power ultrasound

The objective of this study is to investigate the improvement possibilities of the floatability of galena with ultrasonic application in the presence of potassium ethyl xanthate (KEX). For this purpose, micro-flotation experiments were carried out in addition to surface chemistry studies including zeta potential, contact angle, and bubble-particle attachment time measurements at various ultrasonic power levels and conditioning time. The results showed that, the maximum micro-flotation recovery of 77.5% was obtained with 30 W ultrasound power and 2 min conditioning time. In addition, more negative zeta potential values were obtained with ultrasound as well as higher contact angle and lower bubble-particle attachment time, which indicated the increased hydrophobicity of galena with ultrasound

Effect of Operating Parameters on the Breakage Process of Calcite in a Stirred Media Mill

One of the most energy-intensive processes for producing submicron range calcite is stirred media mill. In the present work, numerous operating parameters such as solid mass fraction, grinding media size, media filling ratio, and grinding time have been investigated using a vertical type stirred media mill. The results are evaluated on the basis of mean particle size, specific surface area, and specific energy consumption. After conducting this study, optimum experimental conditions found to be as 70% media filling ratio, 25% solid mass fraction, 1 mm grinding media size, and 120 min grinding time. Besides, energy savings up to 22% were achieved with the choice of proper media size

Effect of conventional and microwave thermal treatments on floatability of low- and high-rank lignites

Thermal treatment is one of the well-known methods used before froth flotation to remove the polar groups from coal surfaces to make them more hydrophobic. In this study, the effect of conventional and microwave thermal treatments on the wettability of low and high-rank lignite was investigated using flotation experiments, zeta potential, and bubble-particle attachment time measurements, as well as hydrophilicity index analyses. The results showed that both of the thermal treatments increased hydrophobicity, and therefore floatability of the coal samples. The optimum results were achieved with conventional and microwave thermal treatment for the low and high-rank coals, respectively