1. Inhibiting effect investigation of ammonium dihydrogen phosphate on oxidative pyrolysis characteristics of bituminous coal
Coal dust seriously affects the safety of coal mines and the occupational health of coal miners. Inhibiting effect investigation of ammonium dihydrogen phosphate (ADP) on oxidative pyrolysis characteristics of bituminous coal (YM) by combining experimental methods with theoretical calculation methods in this study. The thermal stability and reaction kinetics of YM alone and mixed with ADP were evaluated via TGA-DSC tests. The results show that the whole reaction is divided into two stages. Moreover, the average apparent activation energy of oxidative pyrolysis of YM increases from 145.6 to 162.1 kJ mol− 1 after adding ADP. TG-FTIR tests show that the gaseous products of YM during the oxidative pyrolysis process are mainly CO and CO2. The addition of ADP will not affect the types but the concentration of gaseous products. The reactivity of YM and four simplified basic monomers based on the Given model was calculated and discussed by using density functional theory and wave function analysis method. Afterwards, the possible inhibition mechanism of ADP on the free radical reaction of YM is discussed. The whole work is of great significance to safety in coal mines and provides a novel idea for coal dust prevention and control.
DOI: https://doi.org/10.1016/j.fuel.2022.126352
2.Investigation on oxidative pyrolysis characteristics of bituminous coal through thermal analysis and density functional theory
At present, coal is still the main source of energy supply in China. However, However, coal dust, due to spontaneous combustion or gas explosion, seriously affects underground safety production and also threatens the occupational health of underground workers. To understand the causes of harm caused by coal from the perspective of its oxidative pyrolysis characteristics, bituminous coal was selected as the experimental coal sample, To further understand the oxidation pyrolysis characteristics of bituminous coal, thermal analysis and density functional theory were applied. By using industrial analysis, particle size analyzer, SEM and FTIR to characterize the experimental bituminous coal. The multi heating rate experiment of bituminous coal was carried out with thermogravimetric analyzer, and the kinetic analysis results displayed the apparent activation energy of oxidation pyrolysis of bituminous coal ranges from 118.57 to 124.96 kJ mol−1. The TG-FTIR experiments found the main gaseous products of the oxidation pyrolysis of bituminous coal were CO and CO2. The surface electrostatic potential and bond dissociation energy of bituminous coal structure were analyzed by density functional theory. The research results provide important preliminary references for the safe mining of coal mines and the industrial application of bituminous coal.
DOI:https://doi.org/10.1016/j.apenergy.2023.121680
3. Experimental and molecular dynamics simulation study of the ionic liquids' chain-length on wetting of bituminous coal
Controlling coal dust pollution is confronted with numerous challenges in the demanding environment of deep mining. Chemical additives, imidazolium ionic liquids (ILs), have been considered an effective strategy to boost the hydrophilicity of coal and reduce dust emissions. This work conducted experiments with molecular dynamics (MD) simulation to study the wetting characteristics of ILs ([Emim][Cl], [Bmim][Cl], and [Hmim][Cl]) with different chain-length on coal. The static wettability tests results indicated that the wettability of ILs was improved as the chain-length increased, and the wettability on bituminous coal followed the rule of water<[Emim][Cl]<[Bmim][Cl]<[Hmim][Cl]. The dynamic dust suppression experiments in the roadway showed that the dust suppression efficiency of 2% [Hmim][Cl] reached 77.5%, 2.45 times that of water. The ESP and frontier orbital energy show that the chain-length increase can enhance the ILs activity. The MD results indicated that short-chain ionic liquid ([Emim][Cl]) tends to accumulate on the surface of coal molecules, whereas long-chain ionic liquid ([Hmim][Cl]) possesses the capability to permeate coal molecules and serves as a tunneling role between coal and water, thereby enhancing the hydrophilicity of bituminous coal. The research results could be used to determine and design ILs with excellent wetting performance for improving the coal dust suppression effect.
DOI:https://doi.org/10.1016/j.energy.2023.128507
4.Study on the suppression characteristics and mechanism of ABC powder on pulverized coal explosion based on the analysis of thermal decomposition characteristics and reaction kinetics
This study investigates the inhibitory characteristics and mechanisms of ABC powder on coal powder explosion using a combination of experimental, theoretical, and numerical methods. In a 20 L spherical explosion experimental system, coal powder was mixed with ABC powder at various mass concentrations. The microstructure and major functional groups of the explosion products were characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The proportions of the major functional groups were determined through peak fitting analysis. The research findings demonstrate that the introduction of 60 wt% ABC powder into the coal sample led to a significant decrease in the maximum explosion pressure, from 0.683 MPa to 0.454 MPa, indicating a remarkable reduction of 33.38%. Moreover, the inclusion of 70 wt% ABC powder exhibited complete suppression of coal dust explosions. Thermal decomposition characteristics of the mixed system were investigated using a thermogravimetric analyzer, and the Coats-Redfern integral method was employed to analyze the pyrolysis experimental data. The results suggest that the optimal reaction kinetics models for the combustion stage of coal powder and the mixed system are F1 and F2, respectively. Adding ABC powder increases the activation energy by 27.35% and slows down the pyrolysis rate by 37.97%. Furthermore, numerical simulations using CHEMKIN software were conducted to study the inhibitory effect of ABC powder on coal powder explosion. The results demonstrate that the addition of ABC powder significantly reduces the content of O·, H·, and OH·radicals, which are responsible for sustaining explosive chain reactions within the explosion system. By incorporating the findings of this investigation, the present study offers a comprehensive explication of the intricate micro-level mechanisms that underlie the inhibitory properties exerted by ABC powder on coal dust explosions. These results contribute novel scientific and theoretical foundations, yielding profound insights into the prevention and mitigation of calamitous coal dust explosion incidents within coal mining environments.
DOI:https://doi.org/10.1016/j.psep.2023.11.022