Search

To evaluate the granularity distribution pattern for multi-nozzle interference spray, the two-phase flow state inside the nozzle and the fragmentation process of the droplet particles in the eddy current field is studied, and the atomization characteristics of the multi-nozzle spray interference process is simulated based on CFD technology. The results indicate that the braking distance in the atomization field decreases with the increase of atomization pressure, and the decreasing speed is slower, in contrast, the atomizing angle increases with the rise in atomization pressure and the decrease of nozzle diameter. Compared with the single nozzle atomization field, the multi-nozzle atomization field has a more uniform distribution of droplet particles through collision, polymerization and rupture, which can achieve a better dust removal effect. By increasing the atomization pressure, the multi-nozzle interference atomization area can be formed faster, the droplet size is more refined, and the distribution is more uniform. Under the optimal parameters, practical testing indicates that the multi-nozzle air-operated atomization system makes the total dust and respirable dust concentrations at the various measuring points decrease rapidly, and the maximum suppression rates reach 95.52% and 96.84%, respectively. [Display omitted] • The two-phase flow state inside the nozzle and the droplet fragmentation process in the eddy current field was discovered. • The atomization characteristics of the multi-nozzle spray interference process was revealed. • The main atomization parameters of air-operated spraying system were discovered. [ABSTRACT FROM AUTHOR]

The study employed the response surface methodology to experimentally optimize the heat transfer characteristics of a two-phase gravity heat pipe with external fins. The influence of thermal input, fin thickness, width, and spacing on the thermal resistance and heat transfer efficiency of the heat pipe was analyzed by the method of controlled variables, resulting in empirical formulas. A central composite design and response surface methodology were employed to refine the experimental design, with the findings indicating that the adjustment of input thermal power and fin parameters significantly impacts thermal resistance and heat transfer efficiency. Furthermore, the congruence between simulation outcomes and experimental data corroborates the accuracy and reliability of this approach. These insights furnish both a theoretical foundation and practical guidance for augmenting the heat transfer performance of gravity heat pipes. [ABSTRACT FROM AUTHOR]

The excavation of coal mines generates substantial dust, posing environmental and health risks for underground coal mine workers. To address the dust issue, a novel Vortex Air Flow Negative Pressure Entrainment Dedusting Device was developed. Through numerical simulations and a comprehensive experiment, factors influencing dust removal efficiency, such as the number of air ducts, wind speed, and pressure duct layout angle, were analysed. The result showed that the number of air ducts had the most significant effect on the suppression efficiency, while the pressure duct layout angle had the least significant impact. Six ducts with 25 m/s air velocity and 30° pressure duct angle were determined as the optimum operational parameters for dust removal. Field tests with the optimum setting were also conducted. The results demonstrated the best dust control performance compared to other settings, which resulted in a 90% reduction in coal dust concentrations. The developed device provides underground coal mines with an effective method to control coal dust efficiently during the excavation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hygroscopicity of coal powders with different ranks was compared and investigated. • Reasons behind varying hygroscopicity of coal powders were analyzed and explained. • Variation of hygroscopicity of coal powder with particle size was studied. • Effects of ambient temperature and humidity on the hygroscopicity were examined. The hygroscopicity of coal powder is one of the crucial factors that determine its moisture content, which significantly affects its adhesion, flowability, charge properties, and combustion behavior. In this study, the effects of coal particle size, ambient temperature, and relative humidity on the hygroscopicity of coal powders with different ranks were investigated through experimental methods. The results indicated that an increase in coal particle size resulted in a moderate reduction in the maximum moisture adsorption capacity and a substantial increase in the effective moisture adsorption time of the coal powder. As the coal particle size increased from 19 to 21 μm to 6310–6941 μm, the maximum moisture adsorption capacities of the coal powders decreased by 0.28–0.54 times, while their effective moisture adsorption times increased by 1.47–1.68 times. The maximum moisture adsorption capacities of the coal powders increased dramatically with increasing ambient relative humidity, whereas the impact of temperature on their maximum moisture adsorption capacities was not significant. The hygroscopicity of coal powders varied significantly among different ranks. Low-rank coal such as lignite and subbituminous showed strong moisture adsorption ability, while high-rank coal such as anthracite exhibited moderate moisture adsorption ability, and middle-rank coal such as medium volatile bituminous showed the weakest moisture adsorption ability. FTIR spectra analysis and pore testing results revealed that the content of oxygen-containing functional groups and the distribution characteristics of internal pores were critical factors causing the difference in hygroscopicity of the coal powders. The practical value of this study lies in its potential to determine the moisture adsorption rate and the maximum moisture adsorption capacity of coal powder under specific environmental conditions, which is essential for evaluating the moisture status, transportation efficiency and combustion performance of coal powder. [ABSTRACT FROM AUTHOR]

The sonic boom atomization mechanism was applied to design a nozzle based on the Laval aerodynamics principle. The designed nozzle was simulated on the Fluent platform and the performance of the nozzles was evaluated on a test platform. The different parameters, including the flow characteristics, atomization characteristics, and dust reduction efficiency of the nozzle were analyzed under different air-water conditions. The obtained results show that under the same air and water pressure conditions, the size probability distribution peak, particle size distribution range, and median diameter of the droplet are smaller than those of an internal mixing nozzle. The sonic boom atomization nozzle consumes less water compared to traditional nozzles. After the installation of the sonic boom fog screen dust reduction system in the return air channel, the average values of total dust concentration and respiratory dust concentration were reduced by 91.26% and 90.16%, respectively. The obtained results indicate that sonic boom atomization nozzles can realize water saving and efficient dust reduction in underground coal mines. [Display omitted] • Application of Laval aerodynamic principle to coal mine dust reduction and development of corresponding nozzles. • Proposed sonic boom atomization technology based on Laval aerodynamics and produced the corresponding nozzle. • Using simulation and experimentation to test the various properties of sonic boom atomization nozzles. • Comparing the advantages and disadvantages of sonic boom atomising nozzles and conventional internal mixing nozzles in terms of performance. • Field proven sonic boom atomization nozzles significantly improve dust reduction. [ABSTRACT FROM AUTHOR]

• Ionic liquids can enhance the wettability of coal. [HOEtMIm][NTf 2 ] has the best wetting effect, [AMIm][BF 4 ] the second, [HOEtMIm][BF 4 ] the worst. • NMR results show that the ionic liquid treatment will partially dissolve the hydrophobic groups in coal and increase the hydrophilic groups in coal. • f a C , f al H , and f al O are positively correlated with wettability, while f ; a , f al ∗ , and f a H negatively correlated with wettability. As the degree of coal mine mechanization increases, the dust concentration underground increases significantly, and the effective reduction of dust concentration can guarantee the safe production in the mine. Wet dust removal method is the main means to suppress coal dust, and wettability is its theoretical basis. To study the effect of functional ionic liquids on the microstructure of coal and the effect of coal microstructure on wettability, [AMIm][BF 4 ], [HOEtMIm][BF 4 ], and [HOEtMIm][NTf 2 ] were selected to treat lignite and anthracite with different metamorphic degrees. Firstly, the effects of ionic liquids on the wettability of coal surface were investigated by surface tension and contact angle experiments. Secondly, the carbon structure skeleton of coal was analyzed by nuclear magnetic resonance (NMR) experiments. Finally, the correlation between the structural parameters obtained by NMR and the contact angle was analyzed by origin software. The results show that [HOEtMIm][NTf 2 ] has the most obvious wetting effect on coal, and different ions have different effects. The ionic liquid treatment will partially dissolve the functional groups in coal. As f a H (protonated aromatic carbon) decreases, f a C (carbonyl carbon) and f al O (oxygen-bonded aliphatic carbon) increase, the hydrophilicity of coal increases, and as f a ′ (aromatic ring carbon) and f al ∗ (methyl carbon) decrease, f al H (methylene carbon and quaternary carbon) increases, the hydrophobicity of coal decreases. The results of this paper can provide basic theoretical support for improving the hydrophilicity of coal surface to improve the efficiency of mine dust reduction. [ABSTRACT FROM AUTHOR]

• The contact angle of [Bmim][BF 4 ]/[Emim][BF 4 ] with the mixture ratio of 1:5 on the coal surface reached the min value of 34.483°. • [Bmim][BF 4 ]/[Bmim][Cl] and [Bmim][BF 4 ]/[Emim][BF 4 ] composite solutions can not only increase the content of hydrophilic functional groups, but also decrease the content of hydrophobic functional groups. • C O was the primary functional group affecting contact angle. –OH and C O C were the main functional groups affecting moisture content. • [Bmim][BF 4 ]/[Bmim][Cl] with a compounding proportion of 1:5 had the best water retention performance. To investigate the effect of different ionic liquid composite solutions on the wettability and chemical structure of coal dust, 14 ionic liquid compound solutions with various composite ratios were selected to act on long flame coal. Through the contact angle measuring instrument, 14 ionic liquid compound solutions were optimized, and 4 ionic liquid compound solutions with the same anion/cation were selected. The wetting agent with good water retention performance in the 4 kinds of composite solutions was selected by the water retention experiment. FTIR was used to research the change of functional group content in the coal treated by the 4 kinds of composite solutions. The results displayed that the contact angle of [Bmim][BF 4 ]/[Emim][BF 4 ] solution with the mixture ratio of 1:5 on the coal surface reached the min value of 34.483°. The [Bmim][BF 4 ]/[Bmim][Cl] solution with a compounding proportion of 1:5 had the best water retention performance. The hydrophilic and hydrophobic functional groups of long flame coal treated by ionic liquid composite solutions had changed significantly. The [Bmim][BF 4 ]/[Emim][BF 4 ] composite solutions with the compounding proportion of 2:4 and 1:5 and the [Bmim][BF 4 ]/[Bmim][Cl] composite solutions with the compounding proportion of 2:4 and 1:5 can not only increase the content of hydrophilic functional groups OH⋯O, Si–O–Si, C O C, C O, and C O, but also decrease the content of hydrophobic functional groups CH 2 and 2H. By analyzing the relationship between coal wettability and functional groups, it was discovered that the hydrophilic functional group C O was the primary functional group affecting the contact angle, and –OH and C O C were the primary functional groups affecting the moisture content of coal samples. In this essay, the novel composite wetting agent type was prepared by compounding ionic liquid solutions with the same anion/cation in pairs, which has certain guiding significance for further using the novel composite moistening agent to improve the wettability of coal and preventing and control mine dust. [ABSTRACT FROM AUTHOR]

• Different ionic liquids affected the change of functional group content in four functional group intervals in coal. • The anions and cations of different ionic liquids can increase the content of hydrophilic groups in coal dust with different metamorphisms and destroy the hydrophobic groups in the dissolved coal structure. • C O and OH···O had a significant correlation with the contact angle. • 2% [Emim][BF 4 ] had the strongest wettability to coal. Three imidazole ionic liquid solutions were selected to handle coal with distinct degrees of metamorphism to research the influences of cation and anion ions in ionic liquids on functional groups and the relationship between functional groups and coal wettability. The chemical framework of coal was researched by FTIR and the wetting peculiarity of the coal was researched by contact angle meter. FTIR analysis showed that the cation and anion ions in ionic liquids significantly altered the framework of the coal. The contact angle measurement results demonstrated that compared with coal using pure water, the coal handled with ionic liquids showed a smaller contact angle. Finally, the relationship between contact angle and functional group content was analyzed. The results showed that the anions and cations of different ionic liquids can increase the content of hydrophilic groups in coal dust with different metamorphisms, such as OH···O, C O, and C O, and destroy the hydrophobic groups in the dissolved coal structure, such as CH 2 , CH and the benzene ring 3 substitutions. And 2 % [Emim][BF 4 ] can effectively reduce the coal contact angle and improve the wettability of coal dust. The content of C O and OH···O groups had the greatest correlation with the contact angle, which were 0.845 and 0.754, respectively. By studying the influence of anions and cations in ionic liquids on the content of functional groups in coal, the effect of specific anions and cations on coal structure was further discovered, which provides a theoretical basis for the development of new ionic liquids with specific functions, and provides guiding significance for ionic liquid solutions to improve the wettability of coal and reduce the dust concentration. [ABSTRACT FROM AUTHOR]