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Effects of isobutene (i-C 4 H 8) with the unique molecular structure on hydrogen explosions are investigated in a 14 L spherical chamber at 100 kPa and 298 K. The results reveal that for lean hydrogen-air mixtures, the maximum explosion overpressure, maximum pressure rise rate, and deflagration index show a trend from rise to decline. However, for stoichiometric and rich hydrogen-air mixtures, pressure parameters decrease monotonously with increasing i-C 4 H 8. The chemical suppression mechanism of i-C 4 H 8 on hydrogen explosions is revealed in detail by numerical simulation. The relevant analyses show that i-C 4 H 8 can not only change the chain reaction path and cut off the hydrogen-oxygen reaction, but also strengthen the consumption of oxygen and H radicals. This work will provide a novel theoretical foundation for hydrogen explosion prevention and control. [Display omitted] • Effects of i-C 4 H 8 on flame and pressure of hydrogen are observed. • Hydrogen explosions can be effectively suppressed by less than 6.0% i-C 4 H 8. • I-C 4 H 8 can change hydrogen-oxygen chain reaction pathways. • I-C 4 H 8 suppresses hydrogen explosions by enhancing oxygen consumption. [ABSTRACT FROM AUTHOR]

The effects of isobutene (i-C 4 H 8) and carbon dioxide (CO 2) on hydrogen explosions have been explored in a 14 L spherical chamber at 100 kPa and 298 K. The results show that compared with CO 2 , the cooperation of i-C 4 H 8 and CO 2 can more effectively suppress the explosion pressure, pressure rise rate, and deflagration index. The minimum suppression concentration of CO 2 with 1.5% i-C 4 H 8 is much lower than that of CO 2 alone. Numerical simulation reveals the mechanism of the suppression of i-C 4 H 8 and CO 2. I–C 4 H 8 changes the reaction paths, and the addition of CO 2 further lowers the adiabatic flame temperature and the active radical concentration. The excellent performance of the cooperation of i-C 4 H 8 and CO 2 in hydrogen explosions will provide a new idea for the prevention and control of hydrogen explosions. • The cooperation of i-C 4 H 8 and CO 2 is better than using CO 2 alone. • I–C 4 H 8 can effectively reduce the minimum suppression concentration of CO 2. • The suppression mechanism of i-C 4 H 8 and CO 2 in hydrogen explosions is revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] In order to develop a green and efficient nano suppressant for aluminum (Al) dust explosion, MCN with layered structure was synthesized with low-cost urea as precursor via simple calcination technology. The suppression performance of MCN on the flame propagation of 30 μm and 5 μm Al dust with the concentration of 1000 g/m3 was experimentally studied. Results showed that with the addition of MCN increasing, the flame luminous intensity, flame propagation velocity and fluctuating trend of mixture-Al dust were greatly decreased. After adding 500 g/m3 and 700 g/m3 to 30 μm and 5 μm Al dust, the average flame propagation velocities declined by 73.24 % and 94.07 % separately. The minimum inerting concentration of 30 μm and 5 μm Al dust was 600 g/m3 and 900 g/m3. Explosion residuals were analyzed to further reveal the suppression mechanism of MCN in detail. The good performance of MCN provided a potential direction to develop efficient suppressants on the suppression of Al dust explosions to improve process safety. [ABSTRACT FROM AUTHOR]

• Influence of wood dust concentration on deflagration parameters was investigated. • Suppression performance of Zr(OH) 4 on dust deflagration was better than that of SiO 2. • Zr(OH) 4 catalyzes the formation of more residuals with smaller crystallite size. • Suppression mechanisms of wood dust deflagration by ultrafine powder were studied. Flame propagation characteristics of wood dust deflagration and suppression mechanism of ultrafine powders are investigated systematically. The deflagration reaction intensity of wood dust increases firstly and then decreases with the increase in dust cloud concentration. This is due to factors such as oxygen supply, positive feedback among flame characteristic parameters. Thus, there is an equivalent dust concentration for greatest deflagration intensity. Nano-sized ultrafine zirconium hydroxide (Zr(OH) 4) and silicon dioxide (SiO 2) powder are introduced to suppress wood dust deflagration at the equivalent concentration. It is found that Zr(OH) 4 has a suppression effect of endothermic decomposition to generate zirconia (ZrO 2), dilution of oxygen and absorption of free radicals; while SiO 2 exerts suppression effect due to its high melting point and heat absorption. The suppression performance of Zr(OH) 4 is better than that of SiO 2. This is because that Zr(OH) 4 and ZrO 2 have a catalytic carbonization effect. It can not only improve thermal stability of wood particles by catalyzing production of high-temperature resistant residuals, but also promote the formation of catalytic sites to reduce crystallite size of carbon layer on wood particles surface, weakening heat and mass transfer between particles. [ABSTRACT FROM AUTHOR]