Showing papers in "International Journal of Coal Preparation and Utilization in 2015"
TL;DR: In this article, a review of the abundance, mode of occurrence, and recovery methods of rare earth elements in coal and coal by-products is provided along with issues associated with their use with coal resources.
Abstract: Previous research indicates that coal and coal by-products are a potential source of critical elements including rare earth elements (REE) with estimated amounts in the range of 50 million metric tons. Despite the proven presence of elevated REE concentrations, commercial extraction and recovery have not been realized. This article provides a review of the abundance, mode of occurrence, and recovery methods of rare earth elements in coal and coal by-products. The feasibility of using established REE extraction and recovery technologies is discussed along with issues associated with their use with coal resources.
143 citations
TL;DR: In this article, Fourier Transform Infrared Spectrometer (FTIR) spectra and surface tension of three surfactants (anionic, cationic and nonionic) were measured, and the lipophilic hydrophilic ratios (LHRs) of a Chinese (Shendong) low-rank coal were calculated.
Abstract: In the present work, Fourier Transform Infrared Spectrometer (FTIR) spectra and the surface tension of three surfactants (anionic, cationic and nonionic) were measured, and the lipophilic hydrophilic ratios (LHRs) of a Chinese (Shendong) low-rank coal were calculated. A series of flotation experiments were conducted using a combination of surfactants and a collector to modify the surface properities of the coal samples. The results of the studies indicated that nonionic surfactant 2-ethyl hexanol provided better flotation performance than cationic dodecyl amine (DDA) or anionic sodium dodecyl sulfate (SDS). The highest increase in combustible matter recovery was obtained using the 2-ethyl hexanol that was up 42.68 percentage points accompanied with a slight increase of ash content (0.24 percentage point) in comparison with the baseline cost (in the absence of surfactant). It seems that the synergism of the nonionic surfactant and collector significantly enhance the floatability of the Shendong low-rank coal.
69 citations
TL;DR: In this article, the properties of two coals, lignite and bituminous, at low and moderate temperatures were investigated using thermalgravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) methods.
Abstract: Oxidation properties of two coals, lignite and bituminous, at low and moderate temperatures were investigated using thermalgravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) methods The apparent kinetic parameters were determined by the first-order Coats & Redfern method based on the TGA results The mass developments of the two coals during the experimental temperature range of 25–400°C suggest that lignite is more prone to spontaneous combustion than bituminous coal The kinetic analysis results show that all the absolute values of the apparent activation energies of lignite are less than that of bituminous coal, indicating that it is easier for lignite oxidation FTIR spectra show that the structure of coals changed differently during oxidation The aliphatic hydrogen groups (mainly the -CH3 groups), associated hydroxyls, and substituent groups in aromatic structures decreased, and carbonyl species increased in bituminous coal For lignite, both -CH2 and -CH3 groups decrease
61 citations
TL;DR: In this article, a modified column flotation was designed based on the cyclonic microbubble flotation column (FCMC) to enhance the gravity settling of coarse middling particles, which were collected as a third product.
Abstract: A modified column flotation was designed based on the cyclonic microbubble flotation column (FCMC). In the modified flotation column, the froth zone was designed with an inclined arrangement to enhance the gravity settling of coarse middling particles, which were collected as a third product. The modified flotation column was referred as S-FCMC. In this study, the effects of process parameters (collector dosage, frother dosage, superficial gas velocity, and froth layer height) on the performance of the S-FCMC were investigated. For comparison purposes, tests were also conducted using the standard FCMC. The results showed that clean coal obtained using the S-FCMC had lower ash content than that obtained with the FCMC. Under the optimized operating conditions, the decrease in clean coal ash content and clean coal yield was 1.29% and 3.93%, respectively. The increase in tailings ash content and flotation efficiency index was 6.77% and 1.57%, respectively. About 64.55% of the settled (third) product in the in...
31 citations
TL;DR: In this paper, the effects of bed height and particle size on the drying performance of Konya-Ilgin lignite were investigated, and it was found that increasing the bed height increased the drying time and decreased the drying rate, and particles of larger sizes had lower drying rates and higher drying times.
Abstract: Drying of coarse lignite particles, because of high inherent moisture content, is very important for the lignite user. An effective drying process is necessary to utilize coarse lignite particles effectively. Fixed-bed drying experiments were carried out for a Turkish lignite (Konya-Ilgin). Effects of bed height and particle size were investigated. Drying experiments were carried out at 80, 130, and 150 mm bed heights and 20, 35, and 50 mm particle sizes. It was found that increasing the bed height increased the drying time and decreased the drying rate, and particles of larger sizes have lower drying rates and higher drying times. Additionally, it was also found that Konya-Ilgin lignite does not show a constant drying rate and has a long falling drying rate. As a result of this study, drying characteristics of Konya-Ilgin lignite were presented for different drying conditions.
26 citations
TL;DR: In coal flotation, the surface properties of coal particles have a significant impact on the behavior of the coal during processing and may also complicate predictions of this behavior as mentioned in this paper, which is one of the processes that is impacted by intermaceral variations.
Abstract: Macerals are the smallest components of coal recognizable on the microscopic scale and, even when optically homogeneous, they may have variable elemental and molecular chemistry not only across different coal ranks but also in iso-rank coals. These variations in maceral chemistry may have significant impact on the behavior of the coal during processing and may also complicate predictions of this behavior. Flotation is one of the processes that is impacted by intermaceral variations. Flotation is used as a main process to upgrade the fines of higher rank coals. It depends on the surface properties of coal particles, hence their chemical composition. Most of the minerals associated with coal, with the exception of a few (elemental sulfur or some pyrites), are hydrophilic and can easily be separated if liberated from coal by flotation. The organic matter (macerals) possesses different degrees of hydrophobicity, and its response to flotation can vary depending on the surface properties that result from chemic...
25 citations
TL;DR: In this paper, a cyclonic-static microbubble flotation column (FCSMC) was used to separate unburned carbon from coal fly ash (HCFA) materials.
Abstract: Removal of unburned carbon from the high-carbon fly ash (HCFA) is essential when it is used as an admixture in cement concrete. This article deals with processing of the HCFA from the Guangdong province of China. A cyclonic-static microbubble flotation column (FCSMC), a novel device with the characteristics of internal recycling process and multiple mineralization steps, was used to separate unburned carbon from ash materials. A commercial flotation plant with a handling capacity of 110 ton coal fly ash (dry basis) per hour was set up. Using the optimum operational parameters, a clean ash with loss on ignition (LOI) of 3.08% and a removal rate of unburned carbon (RUC) of 80.41% was obtained. The calorific value of the unburned carbon products reached 3534 cal/g. Industrial-scale flotation tests on the circulation pulp pressure demonstrated that the energy input mode and internal recycling process of FCSMC separator was effective in removing unburned carbon from HCFA.
18 citations
TL;DR: In this article, the effects of manganese (Mn) and phosphorus (P) on the spontaneous combustion of coal were investigated, and the results showed that Mn-containing additives promoted the combustion as the temperature increased to 60°C, while P-containing additive showed significant inhibition until the temperature reached 150°C.
Abstract: Coal is rich in a variety of elements and minerals, which influence the spontaneous combustion of coal. This study investigated the effects of manganese (Mn) and phosphorus (P) on the spontaneous combustion of coal. Six Mn- and P-containing additives were added to coal and the gases released by programmed temperature heating were collected. The results showed that Mn-containing additives promoted the spontaneous combustion of coal as the temperature increased to 60°C, while P-containing additives showed significant inhibition until the temperature reached 150°C. Infrared spectra suggested that Mn enhanced the decomposition of the R-O, C-O, and -CH2 in the coal, while P significantly inhibited the decomposition of R-O and C-H. Thermogravimetry/differential thermal analysis (TG/DTA) implied that Mn promoted the oxy-genolysis of coal and released more heat, while P delayed the critical temperature of the spontaneous combustion of coal. In addition, by investigating the contents of Mn and P in the coal from 1...
16 citations
TL;DR: In this article, a soft-sensor model for calculating the two performance index of a dense-medium cyclone in a Taixi plant was proposed. But the performance of the model was only 0.7% for the training set and 0.63% for test data while that of the Ep model was 9.41% and 13.54%, respectively.
Abstract: Four measurable parameters, that is, density of dense-medium suspension (d), inlet pressure of dense-medium suspension (p), content of magnetic substance (c), and coal feed rate (r) were adopted to build a soft-sensor model for calculating the two performance index of a dense-medium cyclone in a Taixi plant. Uniform design was adopted to reduce the number of experiments. The models of actual separation density (δp) and probable error (Ep) obtained by genetic algorithm and regression were proved to be basically right by the 12 training records and another test result. The accuracy of the δp model was 0.7% for the training set and 0.63% for the test data while that of the Ep model was 9.41% and 13.54%, respectively. The behavior of the models were in accordance with field experiences, which showed that p had the most significant effect on Ep and c affected δp most prominently in daily operation.
15 citations
TL;DR: In this article, the effect of particle size, pH, and flocculant dosage on the parameters (gel point and effective solid stress) of mathematical model for the sedimentation and thickening has been investigated.
Abstract: A common way to separate the solid from the liquid in high volumes is using thickeners. Since, the amount of water consumption in the mineral- and coal-processing plant is high, water management needs to optimize the input variables and thickener performance. In this study, the effect of particle size, pH, and flocculant dosage on the parameters (gel point and effective solid stress) of mathematical model for the sedimentation and thickening has been investigated. The gel point and effective solid stress was measured using different batch settling and batch centrifuge tests, respectively. The results showed that in the case of nonflocculated suspension, the gel point increased with lowering of pH, however, in the case of flocculated suspension the gel point decreased with lowering of pH. The gel point also increased with increasing flocculant dosage in certain pH values for the two flocculated and nonflocculated fractions. In the case of nonflocculated suspension, the gel points for d80 = 275 µm and d80 =...
15 citations
TL;DR: In this paper, the effect of total/surface moisture on separation of lignitic coals was investigated by using Allair stratification jig with the aim of finding possible critical surface moisture content for optimum separation.
Abstract: Dry processing methods are well known to be sensitive to the moisture content of the processed material. It is well known that cohesive forces among the particles originating from the surface moisture hinder the individual movement or appropriate stratification of particles during separation. Furthermore, high surface moisture also hampers the flow of feed material. In this study, the effect of total/surface moisture on separation of lignitic coals was investigated by using Allair stratification jig with the aim of finding possible critical surface moisture content for optimum separation. Coal samples in the size of −13 + 4 and −4 mm were processed at different particle total/surface moisture levels to recover as clean coal concentrate as possible along with obtaining tailings with minimum levels of combustibles. It is envisaged that a critical surface moisture on both classification (effective screening) and separation is available around 5.5% surface moisture (corresponding to 15% total moisture) for −1...
TL;DR: This work was presented at the 27th International Coal Preparation Congress (ICPC) in Istanbul, Turkey as mentioned in this paper, where it was presented as a contribution to coal-related research.
Abstract: This
work was presented at the 27th International Coal Preparation Congress (ICPC)
in Istanbul, Turkey
TL;DR: In this article, the effect of various reagents on the coal flotation and the most optimum flotation conditions were determined. And the results obtained from the experiments were subjected to multiple regression analysis by using SPSSP19.
Abstract: In this study, experiments were carried out to examine flotation characteristics of fine coal and to determine the effect of various reagents on the coal flotation and the most optimum flotation conditions. The aim of the study was to obtain low-ash content of froth products from a high-ash-containing feed. The flotation experiments were carried out in two steps. First the optimum flotation condition parameters, such as optimal particle size, frother type, conditioning time, solid-liquid ratio, depressant type, and effect of flocculants, were determined. In the second step, keeping the optimum conditions obtained from the first step constant, a Box- Behnken design was applied for modeling and optimization of some operating variables. Three independent variables are categorized as follows: collector dosage (0–2 kg/t), frother dosage (0.1–0.3 kg/t), froth collecting time (120–180 sec). The results obtained from the experiments were subjected to multiple regression analysis by using SPSSP19. A LOQO/AMPL opti...
TL;DR: In this paper, the effects of hydroacoustic cavitation (HAC) treatment on spiral separation when processing nominal −1500µm Illinois-basin bituminous coal were evaluated.
Abstract: Testing was conducted to evaluate the effects of hydroacoustic cavitation (HAC) treatment on spiral separation when processing nominal −1500 µm Illinois-basin bituminous coal. Cavitation was produced either by flow through an ultrasonic resonator chamber or enhanced cavitation by initial flow through a cavitation box followed by flow through the ultrasonic chamber. After treatment, the slurry was passed through a hydrocyclone for desliming, and the underflow stream was used as spiral feed. Spiral tests were carried out using a two-stage spiral at three volumetric flow rates for different HAC treatment conditions. HAC treatment reduced the overall size distribution of the spiral feed material. Likewise, desliming of the treated material led to a reduction in the ash values for each size interval. For example, after HAC treatment, the ash value of the deslimed material was reduced to 25% compared to 41% for the untreated deslimed material. Subsequent spiral separation of the treated material produced clean ...
TL;DR: In this article, an attempt has been made to characterize these types of coals at different stages of leaching, using x-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM), and optical microscope.
Abstract: Chemical leaching using alkali and acid can be employed for effective separation of mineral matter from difficult-to-wash Indian coals. In this article, an attempt has been made to characterize these types of coals at different stages of leaching, using x-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM), and optical microscope. Although an increase in the concentration of alkali and reaction time positively affects the ash reduction, the reaction rate decreases beyond a certain point due to the formation and simultaneous accumulation of sparingly soluble sodium compounds. The leaching process does not affect the organic macerals.
TL;DR: In this article, the authors used a power-measuring meter to investigate the breakage characterizations of different narrow size fractions of coal in an industrial vertical spindle mill and found that the energy input for grinding decreased with increases in time for each sample.
Abstract: To simulate the grinding process in an industrial vertical spindle mill, the Hardgrove mill was fitted with a power-measuring meter to investigate the breakage characterizations of different narrow size fractions of coal. Power consumption in the grinding process was precisely recorded at the sampling frequency of 1 second with the help of sampling software for power. The experimental results indicated that the energy input for grinding decreased with increases in time for each sample. Changes in the weight percentage in the top-size interval showed that the first-order law was not satisfied to describe the total grinding process. The new produced fine coal had a negative effect on the breakage behavior of coarse particles. But removal of −0.09 mm size can help to increase the energy input for grinding and the generating rate of −0.09 mm also accelerated in turn. The relationship between t10 and energy input can be described by the classical breakage function. Specific energy consumed by raw coal with a s...
TL;DR: In this article, a tri-cone water-only cyclone with a three-stage cone was used for deashing and desulfurization of high-sulfur coal.
Abstract: Separation tests on a high-sulfur-coal sample were carried out using a water-only cyclone (WOC) with a three-stage cone (also named a tri-cone water-only cyclone). The lower size limits of deashing and desulfurization were determined to be 0.098 mm and 0.045 mm, respectively. According to a float-and-sink analysis of various size fractions in the overflow and underflow, the Ecart probable (Ep) value as well as the separation density increased as the lower size fractions decreased. According to dynamic analysis, terminal hindered-settling velocities of spherical particles in the radial direction were obtained and an equation to estimate the lower removal size limits of heavy minerals was developed. With the help of numerical simulations of water–air two-phase flow fields in a tri-cone water-only cyclone (TWOC) and a conventional hydrocyclone, the role of the three-stage cone in the separation process was analyzed.
TL;DR: In this paper, a novel induction timer was built to investigate the effect of calcium ions on the induction time between the coal particle and air bubble, which indicated that induction time increased with increasing concentration of calcium ion.
Abstract: Particle-bubble attachment is an essential step for a successful flotation; the induction time is defined as the minimum contact time required for particle-bubble attachment in a solution. A novel induction timer was built to investigate the effect of calcium ions on induction time between the coal particle and air bubble. The induction-time measurement of coal particle and air bubble attachment indicated that induction time increased with increasing concentration of calcium ions. The induction time was 17 ms in the deionized water; however, the induction time increased to 32 ms at a calcium ions concentration of 1 mmol/L. X-ray Photoelectron Spectroscopy analysis showed that either Ca(OH)2(s) or CaCO3 precipitated on the coal surface after the adsorption of calcium ions. The precipitate of Ca(OH)2(s) and CaCO3 are hydrophilic and would weaken the hydrophobicity of the coal surface, so the induction time between the coal particle and air bubble increased with the presence of calcium ions.
TL;DR: In this paper, the performance of three flotation frothers (1-Pentanol, Methyl iso-butyl carbinol (MIBC), and 2-Octanol) was investigated by water-carrying rate.
Abstract: The water-carrying property of three flotation frothers (1-Pentanol, Methyl iso-butyl carbinol (MIBC), and 2-Octanol) was investigated by water-carrying rate. In this work, the performance of frothers in a three-phase coal flotation was evaluated and related to the water-carrying property in a two-phase system. The frother having a high water-carrying rate, 2-Octanol, shows overall faster kinetics and less selectivity for each size fraction due to entrainment through water. The frothers having a low water-carrying rate were more selective for producing low-ash content coal, such as 1-Pentanol and MIBC. MIBC showed better flotation performance for all size fractions in terms of kinetics and selectivity. The three frothers present good correlation between the water-carrying property and fine coal flotation performance.
TL;DR: In this paper, the effect of cross-sectional shape of the friction rods on the efficiency of fly-ash triboelectrostatic beneficiation was investigated and the results showed that circular shape friction rods were more efficient than others.
Abstract: Triboelectrostatic Beneficiation is a suitable dry process technique recognized widely to remove unburned carbon from fly ash. One of the most significant problems related to fly ash triboelectrostatic beneficiation is the cross-sectional shape of the friction rods. It has an important effect on tribocharging process. The purpose of this research was to determine which kind of cross-sectional shape of the friction rods was appropriate to improve the efficiency of fly ash tribocharging and to remove unburned carbon. An experimental program was conducted to study the effect of four kinds of friction rods with different cross-sectional shapes on tribocharging of fly ash particles. Fly ash particles with sizes ranging from 38 to 74 µm and averaged LOI of 12.65% were used for the study. The operating conditions were electric field voltage of 40 KV and air flux ranging from 12 to 24 m3/h. The results of the study showed that tribocharging efficiency of circular shape friction rods was higher than that of others...
TL;DR: In this article, two subprocesses of densification and strengthening during both stamping and pressing were theoretically and experimentally investigated using compaction test units in combination with a strength test device.
Abstract: The bulk density of an oven charge is a very important factor for the selection of the coking coals and coke quality in a coke-making process for producing blast furnace coke. Major factors influencing the bulk density of coal are moisture content, particle surface properties, particle shape, particle-size distribution, and particle density. The bulk density can be increased significantly through compacting the coal to a coal cake prior to oven charging. The objective of the compaction processes is the production of a cake with high density and as well as a sufficient mechanical strength in order to ensure a trouble-free cake charging into the coke oven. The present article deals with the evaluation of the compaction process based on lab-scale test work. The two subprocesses of densification and strengthening during both stamping and pressing were theoretically and experimentally investigated using compaction test units in combination with a strength-test device. Systematic investigations showed that part...
TL;DR: In this paper, an artificial neural network approach with three layers was systematically employed to predict gas holdup using some of the experimental results, which was successfully compared with the model predictions with less than 5% average error.
Abstract: Flotation column is one of the separation technologies investigated for removal of gangue mineral from coal fines. The effect of process variables, such as gas flow rate, feed flow rate, and frother dosage on gas holdup, were investigated. In this study, the measurement of gas holdup in presence of coal fines was carried out in a laboratory flotation column by a phase separation method. Detailed parametric study was performed to observe the effect of slurry concentration, gas flow rate, slurry flow rate, and frother concentration on gas holdup. An artificial neural network approach with three layers was systematically employed to predict gas holdup using some of the experimental results. The rest of the experimental results were successfully compared with the model predictions with less than 5% average error. In this work, emphasis was made on random selection of training data and small network. The developed trained network was also able to capture the non-linear prediction of gas holdup with new operati...
TL;DR: In this paper, a response surface methodology was successfully applied to investigate the operating conditions of the froth flotation process used to recover coking coal fines obtained from a settling pond, and a quadratic model was developed to evaluate the variation of yield and the grade of clean-coal product with different test conditions.
Abstract: In this study, response surface methodology was successfully applied to investigate the operating conditions of the froth flotation process used to recover coking coal fines obtained from a settling pond. A quadratic model was developed to evaluate the variation of yield and the grade of clean-coal product with different test conditions. Thirteen experiments were carried out based on a central composite design technique. The analysis of variance was performed using design expert software to confirm the developed second-order model was statistically significant and adequate to represent the experimental observations. Using this technique, model coefficients, R2, , and F values, were determined to analyze the developed models. Surface plots showing the relationship between the responses, namely, wt % and ash %, with process parameters, and also plots between experimental versus the predicted responses from the models are presented.
TL;DR: In this article, the effect of coal weathering on coal quality is discussed, and pH determination of coal slurry technique is more reliable for monitoring weathering of the Indian coal.
Abstract: During transportation and stockpiling, coal is in contact with air for periods of time that may exceed 6 months. During this time, reaction with oxygen in the presence of water, sunlight, and possibly elevated temperatures may take place. The resulting weathered coal suffers some alteration in its physical and chemical properties. This article describes weathering with reference to coking coal, and its importance in understanding the weathering of coal. In this article, the effect of weathering on coal quality is discussed. Two Indian coals were kept for a period of 2 months, and different coal properties such as free swelling index (FSI), ash, and slurry pH were monitored at different intervals. This article suggests pH determination of coal slurry technique is more reliable for monitoring weathering of the Indian coal.
TL;DR: In this paper, the effect of the power input on the fine coal flotation rate constant was investigated and an energy consumption test system was established for fine coal, and the relationship between the rate constant and power input at different flotation times was obtained.
Abstract: To explore the effect of the power input on the fine coal flotation rate constant, an energy consumption test system was established for the fine coal. In this investigation, the fine coal investigated was anthracite obtained from the flotation feed of the Xuehu Coal Preparation Plant of the Shenhuo mine in the Henan Province of China. A total of 65 sets of flotation rate tests were carried out with different power inputs at different flotation times. The relationship between the flotation rate constant and the power input at different flotation times was obtained. The result showed that the flotation rate displayed a constant increase, whereas the power input increased at any time during the flotation process. With the continuous increase of the power input, the increasing trend exhibited by the flotation rate constant decreases after reaching a maximum value. The calculation conjecture of the flotation rate constants and the power input were obtained by imitating the calculation method of the flotation ...
TL;DR: Wang et al. as discussed by the authors combined support vector machines (SVM) and genetic algorithms (GA) to predict coal ash's softening temperature (ST) from a given ash composition.
Abstract: Many power plants use blend coals to replace design coal for burning due to economic reasons. These blend coals are usually blended by two types of off-design coal, so there is a need to select the off-design coals and to optimize the blend ratio. In this process, an important problem is how to estimate the properties of the blend coal, especially for the softening temperature (ST) of coal ash. To deal with this issue, this article combined support vector machines (SVM) and genetic algorithms (GA) to predict coal ash's softening temperature (ST) from a given ash composition. An SVM model was built for predicting the ST of coal ash, and its parameters were optimized using GA. The SVM model was trained and verified using experimental data from 12 coal samples and subsequently was tested using data from 17 blended coal samples. The results confirmed the validity of the SVM model, which accurately predicted the ST for all these coal samples. Based on the SVM model, a coal-blending system was developed for a g...
TL;DR: In this article, a techno-economic optimization-oriented analysis method was proposed to determine the optimal yield and ash of coal flotation concentrate, thus maximizing the economic benefits, and the maximum income of per 100 t of raw fine coal came up to 106,221 RMB.
Abstract: A techno-economic optimization-oriented analysis method was proposed to determine the optimal yield and ash of coal flotation concentrate, thus maximizing the economic benefits. With the kerosene and No. 2 fuel oil used as flotation agents and lots of flotation tests done, the allowable dosage ranges of the two agents were determined, then two regression models were developed through orthogonal tests to determine the ash and yield of clean coal by using the software of MATLAB. According to the relation between price and concentrate ash, an optimization model was developed and, as a result, the software of LINGO was used to determine the optimal clean ash and yield, that is, 9.93% and 79.91%, respectively, by which the max income of per 100 t of raw fine coal came up to 106,221 RMB. Exemplification results showed that the method proposed is simple and practical.