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[en] A detailed chemical kinetic mechanism based on the Appel-Bockhorn-Frenklach (ABF) model was established to describe acetylene decomposition, ethylene formation, and soot formation during quenching in coal pyrolysis to acetylene process. The predictions agreed well with the reported acetylene pyrolysis experimental data. Numerical simulations were then performed to deeply understand the reaction behaviors during quenching of coal pyrolysis in thermal plasma, and to optimize the quenching design for better heat recovery. Two key operating parameters of quenching, i.e., the temperature after quenching and the quenching rate, were studied in detail and optimized after the kinetics were validated. The simulation results also proved that hydrogen can promote the formation of ethylene and inhibit the condensation of acetylene during quenching. In particular, in-depth discussion of acetylene decomposition and ethylene formation using this detailed kinetic mechanism combined with thermodynamic method provided a comprehensive understanding of the thermodynamics and kinetics interpreting pilot plant experimental data. - Highlights: • A detailed kinetic model for C_2H_2 decomposition and soot formation is established. • Two key operating parameters of quenching are studied in detail and optimized. • Effects of H_2 on C_2H_4 formation and C_2H_2 condensation during quenching are discussed. • A comprehensive understanding of the pilot plant experimental data is achieved.
[en] The separation of refined silicon from Al-Si alloys through a solvent refining process was studied. Purified silicon particles were separated by air pressure filtration using stainless steel sieves as the filtration media. After the efficient removal of impurities in the refining process, the effects of the mesh number (N), separation temperature (T), silicon content in the alloy (ω(a)), and pressure differential (p) on the separation efficiency were evaluated. At N = 80, T = 873 K (600 °C), ω(a) = 45 wt pct and p = 0.25 MPa, the recovery rate of refined silicon was 98.2 pct, and the residual aluminum in the separated silicon was less than 8 wt pct. The separation process was efficient when N = 60 to 150. It was advisable for the separation temperature to approach the eutectic temperature. Efficient filtration could be achieved when ω(a) = 35 to 55 wt pct. The filtration efficiency was improved with a higher pressure differential, and the separation was efficient at p ≥ 0.10 MPa. The results show that air pressure filtration is a promising method to separate refined silicon.
[en] Hydrodynamic parameters should be identified firstly for predicting soil and water loss with specific issues and objectives. The laboratory simulation scouring experiments were conducted with different gravel contents, flow discharges and slopes based on the field investigation, which achieved the most suitable parameter for predicting soil and water loss on simulation landslide deposit slope in Wenchuan earthquake area, China. The results showed that the gravel content of 25% always was the threshold that controlled the flow shear stress (τ) and stream power (ω) increased or decreased under different flow discharges. The unit stream power (UP) and unit flow energy (E) both decreased when gravel contents increased. The ratio of Manning coefficient to flow depth (n/h) was higher in fine sediments with gravels than that without gravels. The flow discharge had the consistent effects on hydrodynamics which was ordered as 4 < 8 < 12 L min−1. The τ was the most suitable parameter for predicting soil and water loss by considering the degree of reliability, even though the ω also had significant positive power function with soil and water loss. The n/h could describe the hydrodynamics and soil and water loss and be the alternative parameter for predicting soil and water loss. The results provide useful information for soil and water loss prediction in landslide deposits.
[en] The adhesion force between metal-based antibacterial coatings and polymer substrate decides the effectiveness and durability of antibacterial performance. In this study, the silicone rubber substrate was modified by molecular bridge, i.e., polyvinylpyrrolidone, chitosan and (3-mercaptopropyl) trimethoxysilane, to provide “anchors” which captured Ag+ during electroless plating, and Ag coatings were resultantly produced. Different molecular bridge offered different adhesion. The spread plate counting, fluorescent staining assay and bacterial growth kinetics test showed that the antibacterial and anti-biofilm performance against Escherichia coli and Staphylococcus aureus was directly related to coating–substrate adhesion strength. A relative weaker adhesion resulted in rapid bactericidal and bacteria growth inhibition effect, and vice versa. The inductively coupled plasma atomic emission spectrometry indicated that relative weak adhesion provided fast Ag+ release, and strong adhesion gave lower Ag+ cumulative concentration, which may be attributed to different bonding strength. The coatings displayed sustained-release kinetics with the maximum cumulative Ag+ concentration of only 0.45 mg/L after 45 days of immersion in PBS solution, which was far below the human cell toxicity concentration. Nevertheless, all tested Ag coatings exhibited effective and long-lasting antibacterial properties. The tailored adhesion and consequent different antibacterial effect provided a choice for clinical applications.