Wettability Of Coal Dust Research Articles

Experimental investigation on wetting mechanism for coal dust with different metamorphic degree based on infrared spectrum and 13C‐NMR

Respirable coal dust accounts for heart and respiratory diseases of coal miners such as asthma, pneumoconiosis, and black lung disease. What is more, coal dust explosion seriously affects coal mine safety production and coal miners' life safety. Generally, dust suppressants are commonly applied in coal mines. However, current dust suppressants are not working effectively. To develop a better dust suppressant, we attempt to explore the factors affecting the wettability of coal dust under different metamorphic levels from the essence of coal dust wetting mechanism in this paper. Specifically, we use Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) to reveal the microstructure of coal from two aspects of functional group and carbon skeleton structure and obtain the micro information of the surface functional group types, quantity, and carbon structure of coal with different degrees of metamorphism, as well as the change rule of functional group of coal sample with coal rank and the law of carbon increase and deoxidization of coal metamorphism. After that, we acquired the structural parameters of coal by the NMR experiments and fitted the quantitative mathematical relationship between the microstructure parameters and wettability of coal through SPSS and ORIGIN software. Finally, this paper constructs an evaluation model for the influencing factors of coal dust wettability, explains the influence degree of different coal dust structure on coal dust wettability, improves the coal dust wettability mechanism, and provides more quantitative research ideas and methods for the control of coal dust.

Effects of Metamorphic Degree of Coal on Coal Dust Wettability and Dust‐Suppression Efficiency via Spraying

Currently, spraying is a main means for dust prevention and control in underground coal mines. The dust‐suppression efficiency via spraying is highly correlated with the wettability of coal dusts. There are many factors affecting the wettability of coal dust, among which coal’s metamorphic degree has great influence. In order to gain in‐depth knowledge of the effects of coal metamorphic degree on coal dust wettability and the dust‐suppression efficiency via spraying, 6 coal dust samples with different metamorphic degrees were collected and used in the study. In the experiments, the microproperties, wetting performance, and dust‐suppression efficiency via spraying were measured. According to the experimental results of coal’s microproperties, with the improvement of metamorphic degree, the content of hydrophilic oxygen‐containing functional groups on the surface, the surface roughness, the specific surface area, and the interpore diameter all decreased. In addition, as coal’s metamorphic degree was enhanced from lignite to meager‐lean coal, the wettability of the coal dust dropped. On the other hand, as the metamorphic degree of coal quality continued to be improved to anthracite, the wettability of the coal dust increased instead. The measured results revealed that the dust‐suppression efficiency via spraying was highly correlated with the wettability of coal dust. The coal dust with better wettability exhibited higher dust‐suppression efficiency via spraying. With the increase of water‐supply pressure, the effect of coal dust wettability on the dust‐suppression efficiency via spraying was weakened, and the difference of dust‐suppression efficiency among different coal dust samples was narrowed.

Preparation and performance study of a novel polymeric spraying dust suppression agent with enhanced wetting and coagulation properties for coal mine

In this work, an environmental friendly dust suppressant with improved wettability and coagulation properties was developed by a chemical modification method. The hydroxypropyl guar gum was synthesized by nucleophilic substitution reaction between natural polymer guar gum and propylene oxide. Through a series of optimization of adjuvant agents and viscosity experiments, the optimum formulation contained moisture agent W + 0.8% hydroxypropyl guar gum. A mastersizer 3000 laser particle size analyzer was used to determine that the wettability of coal dust increases with the increase of particle size. The dust suppression agent and coal dust were fully mixed and bonded together, as observed by a high-resolution scanning electron microscopy. The spray dust reduction experiment results show that the spray dust reducer developed in this paper can significantly reduce the dust concentration, and the average dust removal rates of total dust and respirable dust are increased to 83.94% and 84.08%, respectively.

Influence of particle diameter on the wettability of coal dust and the dust suppression efficiency via spraying

Spraying is a main technique means for the prevention and control of coal dust in coal mines. The dust suppression efficiency by spraying is highly correlated with the wettability of coal dust. There are many influencing factors for the wettability of coal dust, among which the particle diameter of dust is one of the most significant factors. In order to analyze the influence of particle diameter on the wettability of coal dusts and the dust suppression efficiency via spraying, 18 different samples with 3 different types of coal samples and 6 different particle diameters were selected in this study. A series of experiments were designed and performed to evaluate the micro-properties, the wettability, and the dust suppression performance via spraying of coal dust. According to experimental results on the micro-properties, the amount of hydrophilic oxygen-containing functional groups gradually dropped with the decrease of the particle diameter. As the particle diameter decreased, the specific surface area of coal dust gradually increased while the average diameter of the internal pores decreased. Based on the experimental results on the wettability of coal dust, the wettability of the dust with the same property dropped with the decrease of particle diameter. Finally, based on the experimental results on the dust suppression efficiency via spraying, the dust suppression efficiency via spraying was determined by both the wettability of coal dusts and the value of △D50 (the absolute value of the difference between the droplet diameter and the dust particle diameter). As the particle diameter of coal dust increased, the dust suppression efficiency via spraying first increased and then decreased.

Experimental investigation of the wetting ability of surfactants to coals dust based on physical chemistry characteristics of the different coal samples

To select suitable surfactant as water-spray additive to improve dust suppression efficiency, six types of coal sample (lignite, long flame coal, non-caking coal, gas coal, coking coal, and anthracite) were selected from some typical mining areas in China, the influence of the physical chemistry characteristics of coal samples on the wetting ability of surfactants to the coals dust was investigated. Their proximate composition, ultimate content, chemical structure, surface morphology, pore structure parameters, and contact angle were determined. Three kinds of anionic surfactants – Sodium Alcohol Ether Sulphate (AES), Sodium Alpha-Olefin Sulfonate (AOS), Fatty Acid Methyl Esters Ethoxylate Sulfonate (FMES) – and one kind of nonionic surfactant – Coco Diethanolamide (CDEA) – were selected to carry out sedimentation experiments on the coal samples dust, to explore the main factors influencing the wettability of the coal samples dust. Among these factors, pore size is the main factor determining the wettability of coal dust, the contact angle decreases linearly (R2 = 0.96) with pore size increase. The experimental results demonstrate that the following factors produce correspondingly increased wettability: higher moisture content, lower carbon content, higher oxygen content, more oxygen-containing functional groups, and increased pore size. In addition, the wettability of the six types of the coal samples dust shows a high-low-high trend with metamorphic degree increase, lignite has the strongest wettability, and the coking coal with the highest degree of metamorphism in the selected bituminous coal sample has the weakest wettability. Moreover, compared with nonionic surfactants, anionic surfactants have stronger wetting ability, but the same anionic surfactants have different wetting abilities to coal dust with different metamorphic degrees. AOS has stronger wetting ability to the dust of long flame coal, non-caking coal, and anthracite; AES has stronger wetting ability to the dust of lignite and coking coal; and FMES has stronger wetting ability to the dust of gas coal. The research results provide a theoretical basis for different coal mines to select suitable surfactants as water-spray additives to improve dust suppression efficiency.

无机盐对化学抑尘剂在煤尘表面润湿性能的影响

无机盐对化学抑尘剂在煤尘表面润湿性能的影响

Experimental investigation on the changes of the wettability and surface characteristics of coal dust with different fractal dimensions

To analyze the reasons leading to variations in the wettability of coal dust (from the same coal source) with different diameters (D50), in this study, we used fractal dimensions of the particle size distribution to evaluate the wettability and surface characteristics of the dust (specific surface area, pore structure and gas adsorption ability). These were investigated using dust deposition time and gas adsorption experiments. The results showed that the surface characteristics of coal dust exhibited strongly positive correlations with the fractal dimension. As fractal dimension increased, the specific surface area and gas adsorption ability of coal dust remarkably increased, which may cause the poor wetting performance due to the easier formation of a gas film around the dust. For example, for coal dust with a fractal dimension of 2.593, the specific surface area and gas adsorption increased by 46.1% and 79%, respectively, compared to the values for dust with a fractal dimension of 2.042. Moreover, among four different coal sources, the volume of pores was significantly enhanced with the fractal dimension increased, indicating the more pore structures were developed, increasing the difficulty of spreading a wetting solution on the dust surface. This study concluded that the wettability of coal dust acquired from the same coal source was variable and decreased as the fractal dimension increased.

Experimental investigation on the wettability of respirable coal dust based on infrared spectroscopy and contact angle analysis

Respirable dust does great harm to human health. In this paper, we focused on the wetting characteristics of respirable coal dust, and the effect of functional groups of respirable coal dust on its wettability was investigated. We selected five different types of coal samples (Lignite, Gas fat coal, Coking coal, 1/3 Coking coal, and Anthracite) from some typical mining areas in China. We used a Fourier Transform Infrared Spectrometer (FT-IR) to obtain the IR spectrum of the respirable coal dust, and the percentage of functional groups for each respirable coal dust was obtained by the peak area normalization method and then analyzed. And the wettability of respirable coal dust was evaluated by contact angle measurement. It is found that the benzene rings, aromatic hydrocarbons with benzene rings, aliphatic hydrocarbons with methyl, methylene, and so on, which have carbon-containing macromolecular structures, are hydrophobic. While the oxygen-containing functional groups represented by hydroxyl and carboxyl groups, and silicates and carbonate minerals are hydrophilic. Besides, the results show that respirable coal dust of different metamorphic grade coals has different wettability. This study has important theoretical significance for understanding the wettability of respirable coal dust.

Micromechanism of coal dust wettability and its effect on the selection and development of dust suppressants

Abstract This article investigated quantitative data of carbon- and oxygen-containing groups of lignites, gas coals and anthracites through nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) experiments. In this study, these three different coal samples were denoted as HM, QM and WY, respectively. For HM, the aromatic structures are scarce and simple, the side chains are abundant and long, and many hydrophilic oxygen-containing functional groups are present on the surface. Thus, HM has strong hydrophilicity. For QM, the aromatic rings have compact structure, but the content of oxygen-containing functional groups approximates 50%, which means that QM can be easily wetted. For WY, the polycyclic aromatic structures are compact and the oxygen-containing functional groups on the surface are nearly detached. Therefore, WY is characterized by poor wettability. Then, two commonly-used suppressants (AEO-9 and rapid penetrant T) were used and coal dust wettability was measured. However, these two suppressants, especially the rapid penetrant T, show poor wetting performance on WY but work well with HM and QM. From the perspective of structure, the hydrophobic groups in AEO-9 are similar to carbon structures in WY, and thus AEO-9 is superior to rapid penetrant in the wetting performance of WY, according to the principle of like dissolves like. In other words, for the coal dusts with good wettability, the application of appropriate dust suppressants guarantees satisfactory dust removal performance. However, for the dusts with poor wettability, macromolecular surfactant with similar structures should be developed in order to achieve better dust removal performance.

Effects of chemical properties of coal dust on its wettability

The relationship between coal dust chemical composition and its wettability was analyzed in detail using the Walker test method. The wetting rate of coal dust was also investigated. Results show that the wetting time of coal dust is negatively correlated with moisture content. Increased moisture content improves the wettability, while the content of ash, volatile matter and fixed carbon in the coal dust has no effect on wettability. Surface hydroxyl is the main factor that determines the wettability of coal dust. The wetting time decreases linearly (R2=0.81) with increasing hydroxyl functional group content. The increase of carbonyl group content improves coal dust wettability, but there is no obvious relationship between carboxyl group content and the wetting time. Increased quartz content leads to decreased wettability, which indicates that quartz on the coal dust surface associated with organic composition may be hydrophobic. Compared to bulk chemical composition, the wettability of coal dust is more closely related to the surface hydroxyl functional group. In addition, the wetting time increases linearly with increasing coal dust mass, but the wetting rate differs for different coal dust samples. Coal dust with high hydroxyl content has a faster wetting rate than dust with lower hydroxyl content.

Comparison of effects of sodium carboxymethylcellulose and superabsorbent polymer on coal dust wettability by surfactants

ABSTRACTThe interactions of sodium carboxymethylcellulose (SCMC) and a superabsorbent polymer (SA) with aqueous solutions of active surfactants such as sodium dodecylbenzenesulfonate (SDBS) and alkyl polyglycoside were investigated in terms of surface tension, sink time, and foam liquid fraction. An SA is a more suitable surfactant than SCMC for wetting coal dust, and SDBS and an SA additive in an SA:SDBS weight ratio of 1:4 is the best coal dust suppressant.

Experimental Investigation of Coal Dust Wettability Based on Surface Contact Angle

Wettability is one of the key chemical properties of coal dust, which is very important to dedusting. In this paper, the theory of liquid wetting solid was presented firstly; then, taking the gas coal of Xinglongzhuang coal mine in China as an example, by determination of critical surface tension of coal piece, it can be concluded that only when the surface tension of surfactant solution is less than 45 mN/m can the coal sample be fully wetted. Due to the effect of particle dispersity, compared with the contact angle of milled coal particle, not all the contact angles of screened coal powder with different sizes have a tendency to increase. Furthermore, by the experiments of coal samples’ specific surface areas and porosities, it can be achieved that the volume of single-point total pore decreases with the gradual decreasing of coal’s porosity, while the ultramicropores’ dispersities and multipoint BET specific surface areas increase. Besides, by a series of contact angle experiments with different surfactants, it can be found that with the increasing of porosity and the decreasing of volume percentage of ultramicropore, the contact angle tends to reduce gradually and the coal dust is much easier to get wetted.

Effects of Oxygen Element and Oxygen-Containing Functional Groups on Surface Wettability of Coal Dust with Various Metamorphic Degrees Based on XPS Experiment.

To investigate the difference of surface oxygen element and oxygen-containing functional groups among coal dusts with different metamorphic degrees and their influence on surface wettability, a series of X-ray photoelectron spectroscopy experiments on 6 coal samples are carried out. The result demonstrates that the O/C ratio of coal surface shows an overall increasing trend compared with the result of its elements analysis. As the metamorphic degree increases, the O/C ratio on the surface gradually declines and the hydrophilic groups tend to fall off from coal surface. It could be found that different coals show different surface distributions of carboxyl and hydroxyl which are considered as the greatest promoter to the wettability of coal surface. With the change of metamorphic degree, the distribution of ether group is irregular while the carbonyl distribution keeps stable. In general, as the metamorphic degree goes higher, the content of oxygen-containing polar group tends to reduce. According to the measurement results, the contact angle is negatively related to the content of oxygen element, surface oxygen, and polar groups. In addition, compared with surface oxygen content, the content of oxygen-containing polar group serves as a more reasonable indicator of coal dust wettability.

Experimental Study on Wettability of Coal Dust in Addition of Surfactants

In Different surfactants in combination with some inorganic salts were used to improve wetting behaviors of coal dust in this paper. It shows that wetting capability of the coal dust could be improved by addition of surfactant. The improvement due to surfactant use is like: JFC>OP>SDBS. In the mean time, the improvement of the inorganic salts is like: Na2SiO3>Na2SO4>CaCl2>NaCl. The further investigation demonstrates that the more Na2SO4is used, the better wetting of coal dust is bility is.

Study of Influence Factors on Wettability of Coal Dust

In this study, coal samples of experimental come from the raw coal of Wangfenggang and Qidong. Sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), water-reducing admixture NF and Tween-80 are choosed as surfactants. The influence factors on wettability of coal dust were characterized by contact angle meter, fourier transform infrared spectroscopy (FTIR) and surface tension experiment. The research shows that the effect of solution on wettability of coal dust is mainly depended on the surface structure of coal dust, type and concentration of solution.

Allergie de contact au cocoyl isethionate de sodium

Molecular dynamics simulation combined with experimental methods were used to investigate the adsorption and wetting process of 25 lauryl glucoside (APG-12) molecules on coal molecules and in turn study the dust suppression mechanism by APG-12 at the molecular level. Through wetting experiments, our preliminary findings showed that APG-12 does have a certain wetting effect on coal dust. According to density functional theory in molecular dynamics simulations, the electrostatic potential and surface charge of the APG-12 and coal molecular models were analyzed to identify their nucleophilic and electrophilic regions, and illustrate the hydrogen bond adsorption mechanism. The dynamics simulation results showed that APG-12 molecules can be easily adsorbed on the surface of coal molecules and then adsorb water molecules around them under the action of hydrogen bonds. This was consistent with the results of an analysis of the system’s radial distribution function and the relative concentration distribution of each component in the Z-axis direction. The results are in good agreement with the experimental results from scanning electron microscopy and energy dispersive spectrometer analysis. These data provide further evidence that APG-12 can clearly improve the wettability and suppression of coal dust, which is of great importance for controlling coal dust pollution.

Surfactant properties of biochemically purified coke-plant wastewater

The influence of biochemically purified wastewater on the wettability of coal and coke dust and the ease of scale removal from slurry pipes is considered.

Surface characteristics and wetting mechanism of respirable coal dust

In this study, FTIR and XPS spectroscopy, specific surface area and pore size analyses, wetting and other experimental means have been applied to investigate respirable coal dust surface properties and wetting mechanism. The research shows that coal dust surface structures, chemical and element compositions are changed in the refining process of coal dust. Compared with large particle coal dust, respirable coal dust is a weak hydrophilic and strong hydrophobic substance. The reason: the smaller the particle size of coal dust, the more unsaturated its surface. The absorption of air is strong and it is easy to form an air film on coal dust surfaces. Coal dust contact with water is actually a compound contact of liquid in contact with a solid and gas in contact with a solid. The smaller the particle size, the larger the pore volume and the higher the degree of surface roughness, the larger the area of gas in contact with a solid and the worse the coal dust wettability. Another reason is that the changes in the composition of atoms on the dust surface and structures affect coal dust wettability. The results of this study establish a theoretical basis for the invention of effective reduced-dust technology.

Study on coal dust wettability measurement using cold briquetting technique

Quantitatively-measuring of coal dust wettability is essential for the R/D of chemical coal dust suppressants in the field of dust control with wetting-agent-added water. Analysed the causes which in present lab testing of coal dust wettability cause out-comes’ low repeat rate and poor consistency with coal dust suppression practices in fields, and investigated the influence of different briquetting pressure (from 0 to 6.5×108 Pa) on the wet behavior of coal dust as a new way to evaluate quantitatively coal dust wettability. The study shows that there is a fairly high coincidence between the coal dust wettability data measured by briquetting technique and the results gained from the lab dust suppression tests using an apparatus MCYZ.

The wettability of coal and its relevance to the control of dust during coal mining

Water sprays are used on longwall mining machines to help control respirable coal dust during underground mining operations. Surfactant reagents added to the sprays, if properly selected, can improve the coal dust wettability and capture efficiency of water droplets. Combining water-soluble polymers with a surfactant can improve dust suppression further by altering the adhesion-cohesion properties of water droplets. The mechanism of coal dust control using a surfactant-polymer reagent is discussed. The Bureau of Mines tested an anionic surfactant-polyethylene oxide polymer water spray additive in the laboratory and in an underground longwall coal-mining operation. The results were encouraging but anomalously high headgate dust concentrations were consistently observed when the surfactant-polymer reagent was injected during the longwall tests. A hypothesis, based on rheological considerations and an adaptation of the Good-Islam liquid bridge model, is suggested to explain the phenomenon. A brief example of the method for correcting the mine dust concentration data for the excess headgate dust is given.