Coal Flotation Collector Research Articles

Study on low-rank coal flotation collector screening and performance based on molecular polarity index.

Extensive studies using a trial-and-error approach have been conducted on low-rank coal flotation collectors. However, screening efficient collectors remains a considerable challenge due to the lack of suitable screening principles. It has proven that polar compounds such as carboxylic acids and esters are effective collectors for low-rank coal flotation. In this work, the effects of carboxylic acid, alcohol, and methyl ester on the floatability of low-rank coal were compared, the flotation performance of the polar collector was evaluated with theoretical calculations, a suitable evaluation parameter was determined and a screening principle based on this parameter was determined. The results show that the enhancement effects of polar collectors on low-rank coal floatability follow the order of methyl decanoate > methyl laurate > methyl octanoate > sec-octanol > methyl oleate (or methyl oleate > sec-octanol) > n-octanoic acid. Compared with the molecular polarity index, the hydrophobicity indices log P and dipole moment cannot be used to accurately evaluate different types of collectors and the same type of collectors, respectively. At room temperature, liquid polar compounds with molecular polarity indices in the range of 6.0 ~ 8.0kcal/mol effectively enhance the floatability of low-rank coal. The molecular polarity index of the collector is used for the first time to screen effective collectors of low-rank coal in this work. This parameter is anticipated to be highly important for the development and research of low-rank coal and other mineral collectors. To obtain reasonable and accurate molecular structure, geometry optimization and frequency calculations of the studied collectors were conducted via the Gaussian 09 software package based on density functional theory at the B3LYP/6-311 + G (d, p) level. The integral equation formalism for the polarizable continuum model (IEF-PCM) was utilized with water as the solvent (dielectric constant = 78.36, T = 298K) for all the calculations. Then, the atomic charge distributions (MPA and NPA) and electrostatic potential maps, the dipole moment and molecular polarity index, and the log P and water solubilities of studied collectors were shown or calculated by Gauss View 5.0, Mutiwfn program and website ( https://www.molsoft.com/mprop/mprop.cgi ), respectively.

Study on the intermediate products of Fischer Tropsch synthesis as a collector for coal flotation: Molecular dynamics and experimental studies

As a general coal flotation collector, diesel is often used in the industrial production process, and diesel is not renewable and belongs to the hazardous reagents, so there is an urgent need to find a new type of flotation collector to replace diesel. In this paper, three intermediate products produced by Fischer-Tropsch synthesis technology were used as collector. And five emulsifiers, Span80, Tween80, sodium dodecyl sulfate, betaine, and hexadecyl trimethyl ammonium bromide were used to emulsify 3# synthetic oils to produce emulsion with good stability. The flotation performance of three synthetic oil products as well as emulsified collectors were investigated, and the adsorption capacity of 2# and 3# synthetic oils on the coal surface was studied by molecular dynamics simulation. The results showed that the flotation results of synthetic oil were better than those of diesel, with collector 1# having the best flotation results. The oil in water (O/W) emulsion formulated with Tween80 had the best properties, and remained unstratified in half a month, and there were a large number of 0.1–1 μm oil droplet in the emulsion. Moreover, the emulsified collector of Tween80 with oil-water ratio of 4:6 showed excellent flotation performance, which was nearly 1.5 % higher than that of diesel. The molecular dynamics results are consistent with the synthetic oil flotation results at high concentration dosages, where 3# oil showed better adsorption behavior on the coal surface than 2# oil, but was slightly inferior to diesel adsorption. Therefore, the synthetic oil can be completely used as a substitute for diesel, and the emulsion with oil-water ratio of 4:6 formulated with Tween80 has excellent flotation performance and greatly saves the actual consumption of synthetic oil, which has very high economic and environmental value.

Preparation of long-flame coal flotation collector from waste cooking oil

There is currently a need to develop efficient and environmentally friendly (green) collectors to improve the poor flotation performance of long-flame coal (LFC) due to its vast porosity and high oxidation degree. Herewith, this study introduces ozone (O3) and ultraviolet (UV) oxidation methods to modify waste cooking oil collector (WCOC) and analyzes their effects on the LFC flotation performance. Furthermore, the separation efficiency (SE) of WCOC, O3-WCOC, UV-WCOC and common collectors (diesel, kerosene, DEP) were compared. Fourier Transform Infrared Spectroscopy (FTIR) and Gas chromatography-mass spectrometry (GC–MS) were used to observe the effects of O3 and UV oxidation on WCOC functional groups and chemical composition. The functional groups and wettability changes of LFC treated via common collectors, including WCOC, O3-WCOC and UV-WCOC adsorption were analyzed. Results revealed that a shorter O3 oxidation time resulted in better flotation performance and higher SE compared to UV oxidation. After O3 (5 min) and UV (9 h) oxidations, CH bonds in WCOC were oxidized and the content of oxygen-containing functional groups (particularly –OH) increased to 4.25% and 4.93% from 0.79%, respectively. Compared to common collectors, O3-WCOC and UV-WCOC demonstrated better reactions with oxygen-containing functional groups (especially O = CO and CO) on the LFC surface. This phenomenon led to a substantial increase in contact angle. This novel oxidation method could potentially be applied in wastewater treatment, mineral processing, and other fields.

Coal flotation in a low-rank carbonaceous mineral using 3-phenyl-1-propanol as a collector reagent

In the present work, 3-phenyl-1-propanol is proposed as a new collector for coal flotation in a low-rank carbonaceous mineral containing 2.0% of carbon and basic groups predominantly on the surface. Hydroxyl and carbonyl groups, as well as unsaturated carbon chains, were identified by FT-IR. Microflotation tests were conducted to evaluate and compare the effectiveness of the collector proposed with the one obtained using kerosene, diesel and 1-butylamine. Results show that the highest coal recovery is obtained with 3-phenyl-1-propanol. Mineral has a negative zeta potential in the pH range 2–13, but it does not show an isoelectric point. Furthermore, the zeta potential is modified by the collector. After conditioning, signals corresponding to the collector were identified in the mineral surface by FT-IR. A Box-Behnken experimental design was used for optimization of mineral Recovery and Clean Coal Recovery by flotation. Results showed that pH has not a significant effect on the mineral Recovery, however flotation time and volume of 3-phenyl-1-propanol have a significant direct effect. Optimal conditions for mineral Recovery were pH 8.5 and 84.5 µL of collector for 0.5 g of mineral. For Clean Coal Recovery; pH, flotation time and volume of 3-phenyl-1-propanol have a significant effect. Optimal conditions were pH 4.0, flotation time 2.5 min and 87.9 µL of collector for 0.5 g of mineral.

Thermodynamic behavior and flotation kinetics of an ionic liquid microemulsion collector for coal flotation

To develop a new type of coal slime collector, an ionic liquid microemulsion was prepared using 1-alkyl-3-methylimidazolium chloride ([Cnmim]Cl, where n = 12, 14, or 16) as a surfactant, n-alcohol (n-butanol, n-pentanol or n-hexanol) as a cosurfactant, and n-dodecane as the oil phase, and the interfacial composition and thermodynamic changes of these systems were investigated using Schulman’s titration. Therefore, the [C16mimCl]/n-dodecane/n-pentanol/water microemulsion system was chosen as the microemulsion collector. Moreover, the droplet size and polydispersity index (PDI) of the microemulsion collector were determined, and the average droplet radius of the microemulsion was about 32 nm and the PDI was less than 0.06. The average droplet radius was found to range from 30 to 50 nm by transmission electron microscopy analysis. Furthermore, the coal slime flotation experiments and flotation kinetics analysis showed that the microemulsion collector applied for coal slime flotation yielded the same behavior as that of n-dodecane, but the collector dose can be reduced by about 43% and the cost is only 71% without the need for a frother. And, of the four kinetic models tested, the flotation process using the microemulsion collector was consistent with the first-order matrix distribution model.

Dispersion behavior and attachment of high internal phase water-in-oil emulsion droplets during fine coal flotation

Flotation recovery of fine oxidized coal is frequently inefficient when using conventional oily collectors. A large amount of fine coal is discharged as tailings, leading to resource waste and environmental pollution. To solve the problem of high oil consumption and low efficiency associated with traditional flotation, research efforts have been focused on the use of oil-in-water emulsion to reduce oil consumption. Few studies concerning water-in-oil emulsion, especially the high internal phase water-in-oil (HIP W/O) emulsion, have been conducted. Our microflotation results showed a significant oil dosage reduction when a HIP W/O emulsion was used as a collector for coal flotation. The state of the HIP W/O emulsion dispersion in water and the emulsion droplets attachment at the coal surface are vital issues associated with achieving efficient flotation. In this study, optical microscopy and high speed video microscopy were employed to study the dispersion behavior and microstructure of the HIP W/O emulsion in water. This study found that the HIP emulsion tends to be dispersed as a W1/O/W2 double emulsion during mixing in water because of the migration of the surplus Span 80 in the oil phase to the O-W2 interface. The presence of NaCl in W1 is also essential for a stable W1/O/W2 double emulsion, which is formed when equilibrium of the Laplace and osmotic pressures between the W1 phase and W2 phase is obtained. In addition, the W1/O/W2 emulsion droplets are negatively charged, and the emulsion aggregation appears to be inhibited by electrostatic repulsion. More importantly, the Span 80 emulsifier at the O-W2 interface seems to facilitate hydrogen bond formation between the hydrophilic moieties of Span 80 and the oxygen containing functional groups at the coal surface, which is verified by the results from molecular dynamics simulation (MDS). The hydrogen bond formation plays a leading role in the attachment and/or spreading of the emulsion droplets at the oxidized coal surface. The HIP W/O emulsion could be a potential economical and efficient replacement for the traditional oily collectors as a promising collector for the flotation of fine oxidized coal.

Application of gaseous pyrolysis products of the waste cooking oil as coal flotation collector

Fossil fuel depletion, environmental concerns, and steep hikes in the price of fossil fuels make it imperative to develop alternative and renewable products to decrease oil products consumption in coal flotation process. Pyrolysis product of the waste cooking oil was proposed as a potential coal flotation collector in this paper. The gas chromatograph-mass spectrometer test and thermogravimetric method were used to study the properties of the waste cooking oil. The pyrolysis product of the waste cooking oil was used as coal flotation collector in two different ways. Thermogravimetric analysis showed that the pyrolysis of the waste cooking oil sample was mainly divided into three processes. The waste cooking oil pyrolysis product possessed strong collecting ability and better selectivity, and can replace diesel as a coal flotation collector. 79% combustible matter recovery was obtained in the presence of 1 kg/Mg DW-450 °C dosage compared with that of 68% in the presence of diesel. Better flotation results can be obtained in the presence of gaseous pyrolysis products of the waste cooking oil. With the increase of pyrolysis temperature of the waste cooking oil, the combustible matter recovery of the concentrate is increasing, while the ash content of the concentrate is showing a decreasing trend.

An investigation of coal flotation using nanoparticles as a collector

ABSTRACT The article discusses the application of hydrophobic polystyrene nanoparticles as a collector for coal flotation, aiming to demonstrate the possibility of sorting coal fines with nanoparticles. The results of the flotation tests conducted in this study show that a clean concentrate was successfully obtained from floating high ash coal fines by using nanoparticles. The nanoparticles significantly increased the combustible recovery while kept the concentrate ash content at a low level. Contact angle measurements and electron probe microanalyzer micrographs indicate that the deposition of hydrophobic nanoparticle on coal surface increased the hydrophobicity and microscale roughness of coal particles, which was beneficial to flotation process. Although the current nanoparticles used were effective for coal flotation, the dosage consumption was relatively high due to the coagulation of nanoparticles. This suggests that it is important to increase nanoparticle colloidal stability and improve nanoparticle deposition selectivity for practical applications.

Research on emulsified tyre pyrolysis oil as a coal flotation collector

Research on emulsified tyre pyrolysis oil as a coal flotation collector

Biodiesel as a renewable collector for coal flotation in the future

ABSTRACTBiodiesel is a renewable and clean energy which is being developed day by day. However, oil and coal reserves are decreasing due to an increase in energy demand for the development of social economy. Additionally, fine coal is usually beneficiated by flotation using diesel or kerosene as collectors, which may be a waste of energy. Therefore, using biodiesel as a collector for coal flotation has its potential value. In this investigation, biodiesel was used as a collector for coal flotation. Three bituminous coal samples with different coal ranks were selected, that is, gas coal, coking coal, and lean coal. FTIR results showed that biodiesel contained much more abundant unsaturated fatty acids than diesel. Flotation results showed that the flotation performances of three coal samples using biodiesel as collector were similar to that using diesel as collector. Even better, the concentrate yields of three coal samples using biodiesel as collector were a little higher than that using diesel as collector, while their concentrate ash contents were similar. Throughout this paper, it was proved that biodiesel could have a potential application in coal flotation.

Research on Environmental Friendly Floatation Agent

A newly developed coal flotation collector EDO and its flotation characteristics for three Shanxi different coals were introduced in this paper. EDO was an emulsion composed by diesel oil, water and independent development surfactant PGS. Compared flotation experiments show that, at the same dosage, EDO gives 2~5% combustile material recovery promotion than typical collector with only a slightly ash content increment, but saving over 70% diesel oil, and improves the floatation speed. EDO could promote the dispersion of diesel oil in the slurry, so that the efficiency of floatation was improved. The flotation results showed that the EDO had the characteristics of excellent performance, high selectivity and good stability.

Study on the Floatation Effect of ZFC Agent for Difficult Slime

This paper introduced a newly developed coal flotation collector ZFC and its flotation characteristics for Shanxi three different coal samples. ZFC was an emulsion composed by 27% diesel oil, 70% water and 3% homemade surfactant PGS. The surfactant PGS was synthesized with environmental friendly reproducible oil and several surfactants. The flotation results showed that the ZFC had the characteristics of excellent performance, high selectivity and good stability. ZFC could promote the dispersion of diesel oil in the slurry, so that the efficiency of floatation was improved and about 70% diesel oil was saved.

An improved class of universal collectors for the flotation of oxidized and/or low-rank coal

Ash minerals, including pyrite, can be separated from coal by flotation, primarily making use of the natural hydrophobicity of the carbonaceous matter in coal. However, to overcome the deleterious effect of oxygen functional groups on the coal surface, an organic collector is required. The most common industrial coal flotation collector is fuel oil, but the addition of oxygenated functional groups to the collector molecule markedly enhances the flotation of lower rank and oxidized coals. This paper summarizes the results of detailed study of the flotation response of two high-sulfur coals, Illinois No. 6 coal and Pittsburgh No. 8, using different non-ionic oxygenated surfactants as the collector. The performance of these reagents is compared with that of two oily collectors, namely dodecane and nonylbenzene, and mechanisms for the interaction of these compounds with coal are suggested.

95/01299 Chemical and petrographic classification of kerogen/macerals

In the present work, 3-phenyl-1-propanol is proposed as a new collector for coal flotation in a low-rank carbonaceous mineral containing 2.0% of carbon and basic groups predominantly on the surface. Hydroxyl and carbonyl groups, as well as unsaturated carbon chains, were identified by FT-IR. Microflotation tests were conducted to evaluate and compare the effectiveness of the collector proposed with the one obtained using kerosene, diesel and 1-butylamine. Results show that the highest coal recovery is obtained with 3-phenyl-1-propanol. Mineral has a negative zeta potential in the pH range 2–13, but it does not show an isoelectric point. Furthermore, the zeta potential is modified by the collector. After conditioning, signals corresponding to the collector were identified in the mineral surface by FT-IR. A Box-Behnken experimental design was used for optimization of mineral Recovery and Clean Coal Recovery by flotation. Results showed that pH has not a significant effect on the mineral Recovery, however flotation time and volume of 3-phenyl-1-propanol have a significant direct effect. Optimal conditions for mineral Recovery were pH 8.5 and 84.5 µL of collector for 0.5 g of mineral. For Clean Coal Recovery; pH, flotation time and volume of 3-phenyl-1-propanol have a significant effect. Optimal conditions were pH 4.0, flotation time 2.5 min and 87.9 µL of collector for 0.5 g of mineral.