Underground coal gasification (UCG) is essentially the multi-field coupled thermochemical conversion process. One of the most significant characteristics during the UCG process is the formation of the pronounced oxygen concentration gradient along the gasification channel, which leads to significant zoning characteristics in the underground reaction zone. In this work, the coal reaction behavior driven by oxygen concentration gradient from 0% to 100% (10 levels) is focused. Meanwhile, the numerical model combining reaction kinetics and empirical component distribution is used to compare the gas production performance under different oxygen concentrations. Under the low oxygen concentrations (<21% O-2), the maximum generation rate and content of CO are relatively high, reaching 0.23 mol/(kg & centerdot;K) and 0.75, respectively. In contrast, under the high oxygen concentration (21% similar to 100% O-2), the maximum generation contents of CO2, CH4, and H-2 are higher. As the oxygen concentration increases from 0% to 100%, the apparent activation energy of coal firstly increases from 31.56 to 90.69 kJ/mol, and then decreases exponentially to 20.62 kJ/mol. Meanwhile, compared to the oxygen-lean conditions, the enthalpy change, entropy change, and Gibbs free energy change are lower under the oxygen-enriched conditions. The critical oxygen concentration for the kinetic-thermodynamic parameters of coal is 8%. The gradient distribution of oxygen along the gasification channel is the core driver behind the zonal evolution in UCG. Therefore, in the actual UCG application, the precise regulation of oxygen concentration is essential to optimize syngas composition, improve gasification reaction intensity, and achieve stable evolution of the reaction three zones.
This study proposes an innovative ultrasonic-assisted oily bubble flotation strategy to enhance carbon recovery from coal gasification fine slag (CGFS). Experimental results demonstrate that under 1200 W ultrasonic pretreatment for 15 min, oily bubble flotation significantly outperforms traditional air bubble flotation, achieving a maximum combustible recovery (CR) of 81.83 % and a concentrate yield of 63.73 % (compared to a 30.33 % CR and 21.22 % yield for air bubbles). SEM and EDS analyses reveal that high-intensity ultrasound effectively strips spherical inorganic minerals from the carbon skeleton. This allows the oily bubble concentrate to achieve an exceptional carbon purity of 92 % and a minimal oxygen content of 7.01 %, up from 67.24 % carbon in the raw CGFS. XPS results confirm that the 1200 W oily bubble process maximizes hydrophobic C–C bonds to 71.20 % while suppressing hydrophilic COOH groups to 9.06 %. Furthermore, ultrasonic cavitation helps clear blocked pores, increasing the most probable pore size from 2.06 μm to 2.30 μm, while the carbon skeleton remains structurally intact (evidenced by a stable fractal dimension of 2.79). This physical and chemical cleaning step restores the natural hydrophobicity of the carbon surface, allowing the oily bubbles to create a strong hydrophobic bridge that makes the process highly efficient for decarbonizing CGFS. Ultimately, this combined strategy provides a practical and efficient technical route for the resource utilization of solid waste in the coal chemical industry.
The mining of lead–zinc ore encounters significant spatial variations in rockmechanicalproperties due to the complex lithological assemblage, as well as technical challenges such as explosibility and difficulties in mineral processing. These factors result in insufficient adaptability of existing mining equipment and constrained economic benefits. The use of mechanical rock-breaking equipment to assist the operation of roadheaders can effectively reduce the risk of structural failure, eliminate the hazards of gas explosions, and significantly decrease pick wear while improving mineral processing efficiency. Therefore, this study introduces the drilling-splitting-cutting process in lead–zinc mining engineering, with a focus on optimizing the drill hole layout for typical lead–zinc ore rock masses. The results indicate that during the splitting process, employing a rectangular slotting scheme that increases the depth of the free surface while decreasing the depth of the splitting hole can significantly improve the fragmentation effect. For multi-hole sequential fracturing, a longitudinally aligned arrangement should be used. The maximum effective fracturing distance is exponentially negatively correlated with the tensile strength of the rock mass, while the depth of the splitting holes is negatively correlated with the fractured zone area. Field comparative test results show that the drilling-splitting-cutting process improves excavation efficiency by 84 % compared to single-roadheader excavation and by 9 % compared to drilling-cutting processes. Additionally, it reduces pick consumption by 40 % and 28 %, significantly enhancing construction economics.
Merkel cells, functioning as critical tactile receptors in human skin, exhibit remarkable sensitivity to light-touch stimuli, and the three-dimensional morphology of these receptors demonstrates a high adaptation to their force-field sensing functions. We propose a fluid-structure interaction (FSI) hypothesis: the characteristic short finger-like protrusions on the Merkel cell surface act as biomechanical micro-amplifiers, significantly enhancing their perception efficacy for light touch. To validate this hypothesis, we developed a micropillar array chip with biomimetic protrusion morphologies to replicate the stratified micro mechanical environment of native skin in vitro. Integrating micro-particle image velocimetry (μPIV) and finite element analysis (FEA), the research reveals that under ultra-gentle mechanical stimulation (< 1 mN), these protrusions alter local hydrodynamic characteristics by enhancing localized vorticity and shear strain, thereby functioning as micro-amplifiers for tactile signals. The results indicate that, compared to the smooth control structures without protrusions, the biomimetic microstructures with protrusions increase the local vorticity and the wall friction coefficient. This localized physical field amplification directly facilitates the effective transmission of stress to the cell membrane and its subsequent deformation. Utilizing microfluidic trapping and ultrasonic phased array stimulation, we verified at the cellular level that these amplified mechanical signals can significantly enhance the activation of Piezo channels, manifested as prominent calcium influx. This study not only elucidates the mechanism by which Merkel cell protrusions exert mechanical signal amplification through microenvironmental modulation from a micromechanical perspective, but also provides a biomimetic framework and theoretical guidance for the design of highly sensitive artificial electronic skin.
Refractory high-entropy alloys are promising surface-protection materials for components subjected to elevated temperature, concentrated contact stress and severe sliding wear. However, laser direct energy deposited RHEA coatings exhibit the microstructural heterogeneity and unstable tribological behavior, which restrict their application under the wear-critical conditions. To address this issue, a WMoTaNbV RHEA coating was fabricated on Ti6Al4V alloy by laser direct energy deposition and subsequently tempering treated at 600, 700, and 800 °C. The phase constitution, microstructural evolution, elemental distribution, mechanical properties and tribological behavior were systematically investigated. The results show that the heat treatment (HT) refines and homogenizes the nanostructure while maintaining the BCC-based phase structure, improving the structural stability and resistance to plastic deformation. As the HT temperature is increased from 600 to 800 °C, the average coefficients of friction are decreased from 0.35 to 0.04, while the corresponding wear rates are decreased from 3.55 to 1.68 × 10−5 mm3 N−1 m−1. The improved tribological performance is attributed to the synergistic effects of microstructural refinement, solid-solution strengthening, microstructural stabilization and O-rich protective tribofilm, which reduce the direct contact, plastic deformation and material removal during the sliding wear process. This finding establishes the relationship among the HT-driven nanostructural evolution, tribofilm formation and the transition from severe abrasive/adhesive wear to mild oxidative wear in the WMoTaNbV coating, which is an effective strategy for manufacturing the wear-resistant W-based RHEA coatings.
