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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 flame behavior and pressure characteristics of vented propane-air explosions at elevated static activation pressures (P stat) were investigated in a duct with a length-to-diameter (L/D) ratio of 7. The impact of the discharge traction and the coupling effect of the internal flame front and pressure waves on the flame propagation behavior were captured. The effect of increasing P stat on the vented flame length and width under a fixed vent was weak. The influences of P stat on the pressure profiles and maximum reduced pressure (P red) were investigated. The increase of P stat mitigated the blocking effect of external explosion on P red and further promoted the discharge pressure drop rate to be controlled within the limit of the discharge capacity of the vent. The formation mechanisms of the two main external pressure peaks were analyzed. For the larger D v conditions, the sensitivity of high P stat to the increase of maximum external pressure was higher than that of low P stat. A modified model of P red was developed considering the effects of elevated P stat and vent coefficient K V , which is proved to have a good performance in vented explosion ducts with a large L/D ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Aluminum borate/Zinc borate (ATH/ZB) composite powder is synthesized successfully by the mechano-chemistry technology. • The minimum inhibition concentrations of ATH, ZB and ATH/ZB for aluminum dust explosion are determined. • ATH/ZB composite powder shows superior inhibition performance in comparison with ATH and ZB. • Inhibition mechanism of ATH/ZB for aluminum dust explosion is revealed in detail. This study proved that Aluminum hydroxide (ATH)/Zinc borate (ZB) composite powder could be adopted as excellent inhibitor for aluminum dust explosion, which was successfully synthesized by mechano-chemistry technology. Under the actions of collision, friction and combination forces, the surface energies of ATH and ZB particles were activated, leading to the close compounding of ATH/ZB. The inhibition effect of ATH/ZB on aluminum dust explosion was studied experimentally. Results showed that flame propagation behaviors and velocities were inhibited accordingly as the concentrations of inhibitors increased. Moreover, the minimum inhibition concentrations of ATH, ZB and ATH/ZB were determined, corresponding to 1000 g/m3, 1000 g/m3 and 600 g/m3, indicating that ATH/ZB had superior inhibition performance compared with ATH or ZB. Characterization tests were used to analyze the explosion residues. The inhibition mechanism of ATH/ZB for aluminum dust explosion primarily included three aspects: physical coating effect, heat absorbing effect and gas dilution effect. [ABSTRACT FROM AUTHOR]

Lysine sulfate (LS) powder is at high risk of fire and explosion during its production, processing and storage. Considering its edible and nutritive values, the selection for its explosion inhibitor requires both excellent inhibition performance and environmental friendliness. The inhibition performance of a natural food additive of sodium phytate (SP) on LS dust deflagration is investigated by comparing it with ammonium polyphosphate (APP), which is a widely used flame retardant. The deflagration characteristics of LS mixtures with various mass fractions of SP and APP are recorded by high-speed photography and fine thermocouples. The combustion heat is tested by micro-scale combustion calorimetry. Thermal stability of samples are studied by using a synchronous thermal analyzer. The results show that the deflagration of LS dust is completely suppressed when the mass fractions of APP and SP increase to 2% and 8%, respectively. The corresponding inhibition mechanisms are proposed based on the dust deflagration macroscopic results and microcosmic analysis on thermal decomposition products and residuals. These findings may provide a solution to reduce the probability and damage of dust explosions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel high-efficiency composite named PA@NH 2 -MCM41 was synthesized via self-assembly. • Nano-Al dust explosion was completely suppressed by only 33.3 wt% PA@NH 2 -MCM41. • A complex film based on Al x (HiPh y) was formed during the explosion suppression process. • The excellent capacity of PA@NH 2 -MCM41 was due to the synergy between gas and condensed phase effects. A novel chemical suppressant (PA@NH 2 -MCM41) was synthesized via self-assembly. NH 2 -MCM-41 was prepared using diatomaceous earth (DE) as the silica source. FTIR spectra showed that phytic acid (PA) was successfully grafted onto synthesized NH 2 -MCM-41 via hydrogen bonding. The highly ordered mesoporous structure of PA@NH 2 -MCM41 was observed from TEM and small angle X-ray diffraction (SAXRD). The effectiveness of PA@NH 2 -MCM41 in the suppression of nano-Al dust explosions was investigated. Experimental results suggested that the addition of PA@NH 2 -MCM41 could effectively reduce the average flame propagation velocity (V avg) and maximum explosion pressure (P max). After the addition of 16.7 wt% PA@NH 2 -MCM41, the V avg of the gas-phase flame was reduced by 75%. With addition of 28.6 wt% PA@NH 2 -MCM41, the P max of nano-Al dust decreased by 65.7%. As the mass fraction of PA@NH 2 -MCM41was increased to 33.3%, nano-Al dust explosion was completely suppressed. The SEM, FTIR and EDS results showed that a complex sealing film was formed on the surface of the explosion products, which occupied the open sites on the Al surface and thereby interrupted the Al evaporation and surface reaction. Subsequently, the suppression mechanism by which phosphorus containing suppressants consume free radicals and the interaction of PA molecules with the aluminum particle surface were revealed in depth. [ABSTRACT FROM AUTHOR]