Coal Flotation Research Articles

The adsorption and orientation of frother surfactants on heterogeneous wetting surfaces

Despite the existence of heterogeneous wetting surfaces, studies on the adsorption of surfactants on such complex surfaces are limited. In this study, coal was chosen to prepare heterogeneous surfaces with both hydrophobic and hydrophilic constituents. To quantify the surface heterogeneity of coal, hydrophobic index (HI) was proposed and defined as the ratio of the atomic percentage of un-oxidised carbon to the atomic percentage of oxidised carbon. The adsorption of two frother surfactants, Methyl Isobutyl Carbinol (MIBC) and Dowfrother 250 (DF250) which are widely used in coal flotation, on the surfaces of coal with different HIs was studied. Adsorption isotherms and bubble attachment time measurements revealed that MIBC and DF250 could adsorb on the surfaces of coal, driven by hydrophobic interactions on hydrophobic sites and hydrophilic interactions on hydrophilic sites simultaneously with the former adsorption mechanism predominating. The former adsorption mechanism generated head-out adsorption of MIBC and DF250 without changing the surface hydrophobicity, but the latter adsorption mechanism gave rise to head-on adsorption of MIBC and DF250 resulting in an increase in hydrophobicity on the surface of coal with a low HI. Due to different structures, MIBC and DF250 exhibited different adsorption and orientation on the surfaces of coal.

Utilization of waste coal flotation concentrate for copper matte smelting

In this work, the process of copper matte smelting with the utilization of a fine-grained coal-bearing material (the so-called coal flotation concentrate) as fuel is presented. This material is obtained by the process of coal sludge utilization, and, currently, it constitutes an undeveloped waste due to environmental restrictions. There have been postulated methods for using this fuel in technological processes. The addition of this material to the copper concentrate briquettes was acknowledged as the best solution. Those briquettes were tested taken into account the practical strength requirements, and they were re-molten to obtain copper matte. The introduction of the floto-concentrate in the mixture to the briquetting process in quantities of up to 10% by mass allows obtaining of the briquettes with the technologically required discharge strength and compressive strength. The Cu content in the copper matte, obtained in the process of smelting briquettes containing Cu concentrate and coal flotation concentrate, is within the range of values obtained under industrial conditions.

Intensification of Coal Flotation by Means of Air Microbubbles

Intensification of Coal Flotation by Means of Air Microbubbles

Role of Magnesium Salts in Coal De-Ashing by Flotation

Abstract The most frequently investigated salts in coal flotation are chlorides. However, seawater contains additional salts such as sulfates. In coal flotation, magnesium chlorides showed the best results in terms of higher yield and lower ash content compared to the other magnesium salts studied. Therefore, two magnesium salts were tested in this investigation, namely magnesium chloride and magnesium sulfate. The effect of the magnesium salts as well as the optimization of coal flotation were investigated by statistical design of experiments in terms of pulp density, particle size, conditioning time and different dosages of MgCl2 and MgSO4. The flotation results obtained by statistical design show that the ash content was lowest at 8.2% when a mixture of 2 kg/t MgSO4 and 2 kg/t MgCl2 has been used, with pulp density 20%, particle size 400 lm and conditioning time 15 min. The particle size plays an important role in reducing the ash content when the conditioning time has been extended and pulp density has been reduced. The strong interaction between the salts hinders the reduction of the ash content to less than 8.2%.

Maximizing recovery, grade and throughput in a single stage Reflux Flotation Cell

The Reflux Flotation Cell (RFC) utilises the Boycott Effect to decouple the overflow water flux from the gas flux, permitting in principle high product grade and recovery at a vastly higher volumetric feed flux. This study investigated this relationship between concentrate grade, recovery, and volumetric feed throughput using a single flotation stage and feed fluxes spanning 1–9 cm/s, well beyond that used in conventional flotation. Coal flotation tailings and hydrocyclone overflow provided convenient representations of “binary” feeds for the experiments, constituting liberated hydrophobic and hydrophilic particles. The results demonstrated robust recoveries through the preservation of the gas to feed flux ratio with increasing feed flux, while minimising the gas flux strengthened the capacity to maintain high product grade using inverted fluidization water as the wash water. Remarkably, a high product grade (low product ash%) was maintained over the extreme feed flux range by ensuring a net downwards flux of wash water delivered through the upper fluidized bed of bubbles. Coal Grain Analysis (CGA), an optical imaging technique, identified the maceral composition of the feed particles and validated, with close agreement, the RFC steady state separation performance. Indeed, under continuous operation the RFC data demonstrated an overall positive shift in performance relative to that of the standard tree flotation curve. The findings showed strong preservation of product grade and recovery using a single RFC stage, over a seven-fold increase in the feed flux relative to conventional flotation systems.

Hydrometallurgical processing of technogenic finely dispersed fluorocarbon-containing raw materials of primary aluminum production

The purpose of the paper is to determine the conditions for the maximum transition of fluorine from the technogenic raw materials of primary aluminum production (mature sludge) into solution under alkaline leaching. The object of research is the mature sludge, which is formed from technogenic finely dispersed materials of aluminum production in the baths with Soderberg anodes (tailings of coal foam flotation, gas cleaning sludge, electrostatic precipitator dust) and stored close to the enterprise. Analytical studies of the initial sample and leaching products have been carried out according to the certified methods using chemical, X-ray phase and titrimetric analysis methods. It is shown that, the main percentage of the three sludge components belongs to the dust of electrostatic precipitators (~ 79.7%) and coal foam flotation tailings (~ 15.8%). It has been determined that the gas cleaning sludge features the richest composition of useful components (in the sum of F, Na and Al ~ 63%). According to the data of X-ray phase analysis, the sludge sample from the sludge storage mainly contains cryolite (up to 78.7%), carbon (11.9%), calcium-magnesium carbonate from the dolomite series (4.44%), and trace amounts of corundum and fluorite. The results of the conducted experiments on fluorine leaching from the sludge sample by the caustic soda solution allow to estimate the main process parameters: temperature - 75–80°С, duration - 60 min, NaOH concentration - 3.0% (with the W:T ratio of 10:1 and a stirrer speed of ~ 1005– 1010 rpm). According to the analytical data on the chemical composition of leaching cake, the fluorine content in the solid phase reduces by 88.1%. The experiments carried out on alkaline leaching of fluorine from the sample of mature sludge formed under primary aluminum production by the electrolysis of cryolite-alumina melts in the baths with self-baking anodes allowed to find out that the maximum decrease of fluorine content in the sample is achieved under the conditions of maintaining the process parameters including temperature, duration, reagent concentration in optimal modes.

Improvement of Low‐Rank Coal Flotation Based on the Enhancement of Wettability Difference between Organic Matter and Gangue

AbstractThe main reason for low separation efficiency in low rank coal (LRC) flotation was the small wettability difference between organic matter and gangue. To improve LRC flotation response, a new method based on the expansion of wettability difference was proposed in this investigation. This method is that changing the adsorption liquid environment (adding Ca2+) to enhance the selective adsorption of surfactants on the surface of organic matter and increase its hydrophobicity, meanwhile applying ultrasonic desorption to remove the surfactants adsorbed on the gangue. The experiments were conducted on organic matter, gangue, and raw coal and combined with surfactant adsorption/desorption capacity, FTIR, and wetting heat determination to explore the underlying mechanism. The best flotation performance of raw coal was obtained when desorption time was 30 s. Surfactant adsorption results indicated that Ca2+ could promote the adsorption of surfactant on organic matter, but has insignificant effect on gangue. Under ultrasonic condition, surfactant capacity adsorbed on gangue decreased in the presence of Ca2+, but the addition of Ca2+ could inhibit surfactant desorption. However, in the raw coal, the surfactants could be removed from gangue surface under ultrasonic and Ca2+ because of the low proportion of gangue in raw coal and weaker adsorption strength of Ca2+ on gangue, as indicated by the ash reduction. Wetting heat results suggested that wettability difference between organic matter and gangue was expanded after ultrasonic treatment. This study may have some guiding significance for improving LRC flotation.

Influence of hydrodynamic cavitation pretreatment on coal flotation

The flotation of fine coal particles has been a long-standing challenge in coal processing industry. In this study, the influence of hydrodynamic cavitation pretreatment (HCP) on coal flotation was investigated. A special HCP experiment system was designed for the conditioning of pulp based on the cavitation phenomenon through a venturi tube. Flotation results indicate that, compared with the conventional flotation method, HCP increases combustible recovery of concentrate by about 5%, besides, 50% collector dosage or 25% frother dosage can be saved with HCP under the same combustible recovery of concentrate. Meanwhile, HCP enhances the flotation rate constant by 9.41%. The sieving analysis of flotation products reveals that HCP flotation has a better response for fine coal particles relative to that of coarse coal particles. The bubble observation tests confirm the existence of micro-nano bubbles generated by HCP and the selective generation of micro-nano bubbles on the surface of coal. In addition, HCP leads to an obvious improvement of dispersion of collector. The aggregation of fine coal particles caused by HCP is another important contribution for the coal flotation. [Received: May 18, 2019; Accepted: March 28, 2020]

Influence of Reagent Emulsification on Coal Flotation in the Presence of Gas Microbubbles

Influence of Reagent Emulsification on Coal Flotation in the Presence of Gas Microbubbles

Influence of hydrodynamic cavitation pretreatment on coal flotation

Influence of hydrodynamic cavitation pretreatment on coal flotation

Activity of Different Chemistry Agents in Flotation of Difficult Slack Coal

Activity of Different Chemistry Agents in Flotation of Difficult Slack Coal

Modelling of coal flotation responses based on operational conditions by random forest

Coal consumption is one of the critical factors in the economy of China. Flotation separation of coal from its inorganic part (ash) can reduce environmental problems of coal consumption and improve its combustion. This investigation used random forest (RF) as an advanced machine learning method to rank flotation operations by variable importance measurement and predict flotation responses based on operational parameters. Fifty flotation experiments were designed, and performed based on various flotation conditions and by different variables (collector dosage, frother dosage, air flowrate, pulp density, and impeller speed). Statistical assessments indicated that there is a significant negative correlation between yield and ash content. Experiments indicated that in the optimum conditions, yield and ash content would be 80 and 9%, respectively. Variable importance measurement by RF showed that frother has the highest effectiveness on yield. Outcomes of modelling released that RF can accurately be used for ranking flotation parameters, and generating models within complex systems in mineral processing. [Received: May 20, 2020; Accepted: July 19, 2020]

ПРИМЕНЕНИЕ НЕОРГАНИЧЕСКИХ РЕАГЕНТОВ-МОДИФИКАТОРОВ ДЛЯ ИЗВЛЕЧЕНИЯ СЕРОСОДЕРЖАЩИХ ПРИМЕСЕЙ ПРИ ФЛОТАЦИИ ГАЗОВЫХ УГЛЕЙ

The relevance of the research lies in the need to remove sulphur-containing compounds from coal raw materials at the lowest cost to reduce the environmental load in the areas of coal use. The object of the study is coals of the “G” brand of the Kuznetsk basin of the Kirov mine. The subject of the study is the petrographic and chemical composition of coals, the content of sulphur impurities. The aim of the study is to develop selective reagent flotation modes using inorganic reagents-modifiers. Research objectives: – to determine the petrographic and chemical composition of coals; – to conduct flotation studies using the foam flotation method; – to evaluate the effect of inorganic reagents-modifiers on the φ - potential and hydration of the coal surface; – to determine the mechanism of modifiers’ action on the depression of sulphur-containing impurities of coals. Methodology and methods of research. A complex of physical, chemical and physico-chemical research methods has been used in the work. The degree of scientific development of the topic. A promising direction for reducing sulphur-containing emissions is to increase the selectivity of the flotation process by modifying the coal surface. Results: petrographic analysis of the studied coals has showed that the main micro-component is vitrinite (85 %); chemical analysis indicates that the humidity of the coals is 2.27 %, the ash content is 17.82 %, the yield of volatile substances is 32.90 %, the mass fraction of inorganic sulphur is 0.38 %, organic sulphur is 0.43 %. A comparative analysis of qualitative and quantitative indicators of coal flotation shows that the use of non-organic reagents-modifiers can significantly increase the extraction of sulfur into flotation waste. The analysis of the kinetics of changes in the electrode potential of pyrite indicates an increase in the potential values in the presence of these reagents and a decrease in the hydration of the pyrite surface. The obtained results indicate the expediency of using inorganic salts as modifier reagents that contribute to reducing the sulfur content in coal concentrates due to the depression of pyrite-containing impurities due to an increase in the hydration of their surface

Modelling of coal flotation responses based on operational conditions by random forest

Coal consumption is one of the critical factors in the economy of China. Flotation separation of coal from its inorganic part (ash) can reduce environmental problems of coal consumption and improve its combustion. This investigation used random forest (RF) as an advanced machine learning method to rank flotation operations by variable importance measurement and predict flotation responses based on operational parameters. Fifty flotation experiments were designed, and performed based on various flotation conditions and by different variables (collector dosage, frother dosage, air flowrate, pulp density, and impeller speed). Statistical assessments indicated that there is a significant negative correlation between yield and ash content. Experiments indicated that in the optimum conditions, yield and ash content would be 80 and 9%, respectively. Variable importance measurement by RF showed that frother has the highest effectiveness on yield. Outcomes of modelling released that RF can accurately be used for ranking flotation parameters, and generating models within complex systems in mineral processing. [Received: May 20, 2020; Accepted: July 19, 2020]

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Coal preparation plants are under increasing pressure to reduce their consumption of fresh water leading to the use of recycle water. Recycled water generally contains a large quantity of dissolved inorganic electrolytes, which affect coal flotation. This paper reports the conductivity and pH measurements of water in the tailings stream of an industrial scale flotation cell covering a period of approximately two years. The different coal seams processed at the site were also compared and the influence the water quality on the overall yield of coal assessed. This study presents the large variation in inorganic content in recycled water observed for a wash plant and determines its possible effect on coal preparation. The maximum daily temperature was found to be an important factor controlling the amount of inorganic electrolytes in the water and, very significantly, the water management system implemented. The overall plant performance was somewhat affected by the use of water containing high concentrations of inorganic electrolytes. The effect of the quantity of ions in the water on the flotation process is explored in Part 2.

Particle size grouping method as a control system of efficiency flotation process on the example of coal

Agglomeration of coal particles during flotation can be analysed with the Particle Size Grouping (PSG) method. Numerous experiments were carried out to theoretically explain the effect of carbon particles agglomeration, but the result still remains incomplete. In this paper the PSG method was used to analyse agglomeration groups of carbon particles of initial size 100-400 ?m, maintaining the total particle volume. The size of particles population with definite radius and density was determined for 1 Mg coal. The influence of density and size of particles with given mixing energies and parameter ? on agglomeration was analysed. It was stated that the size of the particles had an effect on their agglomeration. In the analysed cases the dimensionless parameter of collision turbulence t* needed for particles agglomeration in particular size groups was importantly shorter for particles of initial size 300 and 400 ?m. The change of the mixing energy did not have influence on the agglomeration of coal particles. The theoretical analyses based on computer calculations were supplemented by the analyses of the coal flotation process on an aqueous model. Experiments lied in introducing a foaming agent in the form of aqueous solution of hexanol which, without changing pH of the pulp, lowered surface tension value, and consequently increased the dispersion of air in the suspension. The experimental results were presented in the form of flotation kinetics curves. Fine particles 100-200?m. turned out to be best for flotation, unlike coarse 400-500 ?m.

Using artificial neural networks for the intelligent estimation of selectivity index and metallurgical responses of a sample coal bioflotation by rhamnolipid biosurfactants

ABSTRACT The present study investigated the effects of rhamnolipid (RL) biosurfactant on the flotation performance of a coal sample. The significance of the effect of RL on the system responses, including ash content, coal recovery, yield and separation efficiency, and process kinetics and selectivity, was statistically assessed using One-Way Analysis of Variance (ANOVA) methodology. The ANOVA results revealed that adding RL to the system significantly challenged the studied metallurgical aspects. Briefly, RL biosurfactant depressed coal flotation through physical interaction with the surface of coal particles through chemical bonding between the carboxyl group in the RL structure with those on the surface of coal particles. The potential mechanisms involved were schematically proposed. The correlation between the condition of RL addition and process responses was modeled using the Artificial Neural Network (ANN) approach. Rested in the mean squared error (MSE), root mean squared error (RMSE), and percentage error as the measures of model accuracy, the Levenberg-Marquardt algorithm (LMA) with [7–16-1] structure was found to be the most reliable algorithm to predict the process response. As evidenced, the correlation coefficient values of test data were 98.09%, 96.93%, 98.37%, 98.46%, 99.50%, and 97.37% for ash content, coal recovery, yield, separation efficiency, the rate constant, and selectivity index, respectively. These values confirmed that the process could be simulated using the ANN method with an appropriate structure.

Utilization of Energy By-Products for Ground Structures in Terms of Production Process

The article deals with the utilization of energy by-product (EBP) for further processing. The suitability of EBP for ground structures significantly depends on its production process. Its properties are influenced by brown coal flotation and by the usage of desulphurization methods. A comparison of physical-mechanical properties of different types of EBPs was performed. The main goal was to compile an apparent table of utilization and suitability of EBP for ground structures - road earth bodies, dams, and embankments according to the process of their formation.

Clean products from coal gasification waste by flotation using waste engine oil as collector: Synergetic cleaner disposal of wastes

Synergetic cleaner disposal of coal gasification waste and waste engine oil is urgent, as the harmfulness to environment and lacks of clean and efficient technique. In this work, coal gasification fine slag was divided to two clean products without byproducts or wastes by flotation using waste engine oil as flotation collector, achieved the goals of “Carbons Recycle” and “Waste Disposal by Waste”. The waste engine oil improved the flotation property of the −0.5 mm fraction coal gasification fine slag, thereby a flotation concentrate with a loss-on ignition of 88.86 wt% and recovery of 92.13 wt% was produced at the waste engine oil dosage of 3 kg/t. The main components of waste engine oil were hydrocarbons, esters, and heteroatom-containing species, as confirmed by gas chromatography/mass spectrometry. The mechanism of flotation using waste engine oil as a collector for the coal gasification fine slag particles was examined via the measurement of contact angles and wrap angles. The qualified tailings (i.e. flotation tailings and +0.5 mm fraction coal gasification fine slag) with loss-on ignition of less than 5 wt% were also obtained to the standard for direct utilization in building materials. Economic evaluation indicates that the net profit would reach 12309.46 USD/h, with a coal gasification fine slag raw capacity of 400 t/h. This work demonstrates that the application of waste engine oil in coal gasification fine slag flotation is feasible, efficient, economical, and eco-friendly, and it has potential industrial application prospects.

Ultrasound-electrochemistry enhanced flotation and desulphurization for fine coal

Most studies on coal flotation desulfurization are either focused on the effect of ultrasonic treatment alone or electrochemical method, but there are few studies on the ultrasound-electrochemistry enhanced method. In this paper, ultrasound- electrochemistry enhanced flotation and desulphurization for fine coal is investigated. The effects of ultrasonic power, treatment time, electrolysis current, and the amount of anhydrous ethanol on the desulfurization rate are investigated with Ca(OH)2 as the electrolyte and anhydrous ethanol as an auxiliary agent. The results are compared with the desulfurization effect of electrochemistry and ultrasound-enhanced flotation respectively. Besides, the mechanism of ultrasound-electrochemistry enhanced flotation and desulphurization for fine coal is analyzed. Results show that when anhydrous ethanol dosage, ultrasonic treatment time, electrolysis current, and ultrasonic power are 30 ml, 20 min, 1.5 A, and 250 W respectively, the desulfurization rate and cleaned coal yield of ultrasound-electrochemistry enhanced flotation and desulphurization method reach 75.42% and 72.15% respectively. It is proved that the combination of ultrasound and electrochemistry has a better desulfurization effect on fine coal than ultrasound-enhanced flotation or electrochemistry method.