Metal-based nanoenergetic materials: Synthesis, properties, and applications

Effects of particle size, dust concentration and dust-dispersion-air pressure on rock dust inertant requirement for coal dust explosion suppression in underground coal mines

An insight into ignition factors and mechanisms of magnesium based materials: A review

Explosion characteristics of micron- and nano-size magnesium powders were determined using CSIR-CBRI 20-L Sphere, Hartmann apparatus and Godbert-Greenwald furnace to study influence of particle size reduction to nano-range on these. The explosion parameters investigated are: maximum explosion pressure (Pmax), maximum rate of pressure-rise (dP/dt)max, dust explosibility index (KSt), minimum explosible concentration (MEC), minimum ignition energy (MIE), minimum ignition temperature (MIT), limiting oxygen concentration (LOC) and effect of reduced oxygen level on explosion severity. Magnesium particle sizes are: 125, 74, 38, 22, 10 and 1 μm; and 400, 200, 150, 100, 50 and 30 nm. Experimental results indicate significant increase in explosion severity (Pmax: 7–14 bar, KSt: 98–510 bar·m/s) as particle size decreases from 125 to 1 μm, it is maximum for 400 nm (Pmax: 14.6 bar, KSt: 528 bar·m/s) and decreases with further decrease of particle size to nano-range 200–30 nm (Pmax: 12.4–9.4 bar, KSt: 460–262 bar·m/s) as it is affected by agglomeration of nano-particles. MEC decreases from 160 to 30 g/m3 on decreasing particle size from 125 to 1 μm, its value is 30 g/m3 for 400 and 200 nm and 20 g/m3 for further decrease in nano-range (150–30 nm). MIE reduces from 120 to 2 mJ on decreasing the particle size from 125 to 1 μm, its value is 1 mJ for 400, 200, 150 nm size and <1 mJ for 50 and 30 nm. Minimum ignition temperature is 600 °C for 125 μm magnesium, it varies between 570 and 450 °C for sizes 38–1 μm and 400–350 °C for size range 400–30 nm. Magnesium powders in nano-range (30–200 nm) explode less violently than micron-range powder. However, likelihood of explosion increases significantly for nano-range magnesium. LOC is 5% for magnesium size range 125–38 μm, 4% for 22–1 μm, 3% for 400 nm, 4% for 200, 150 and 100 nm, and 5% for 50 and 30 nm. Reduction in oxygen levels to 9% results in decrease in Pmax and KSt by a factor of 2–3 and 4–5, respectively, for micron as well as nano-sizes. The experimental data presented will be useful for industries producing or handling similar size range micron- and nano-magnesium in order to evaluate explosibility of their magnesium powders and propose/design adequate safety measures.

Explosion characteristics of micron- and nano-size magnesium powders

Experimental research of particle size and size dispersity on the explosibility characteristics of coal dust

An experimental investigation was carried out on magnesium dust explosions. Tests of explosion severity, flammability limit and solid inerting were conducted thanks to the Siwek 20 L vessel and influences of dust concentration, particle size, ignition energy, initial pressure and added inertant were taken into account. That magnesium dust is more of an explosion hazard than coal dust is confirmed and quantified by contrastive investigation. The Chinese procedure GB/T 16425 is overly conservative for LEL determination while EN 14034-3 yields realistic LEL data. It is also suggested that 2000–5000 J is the most appropriate ignition energy to use in the LEL determination of magnesium dusts, using the 20 L vessel. It is essential to point out that the overdriving phenomenon usually occurs for carbonaceous and less volatile metal materials is not notable for magnesium dusts. Trends of faster burning velocity and more efficient and adiabatic flame propagation are associated with fuel-rich dust clouds, smaller particles and hyperbaric conditions. Moreover, Inerting effectiveness of CaCO 3 appears to be higher than KCl values on thermodynamics, whereas KCl represents higher effectiveness upon kinetics. Finer inertant shows better inerting effectiveness.

Experiment-based investigations of magnesium dust explosion characteristics

Experimental investigations of coal dust-inertant mixture explosion behaviors

An extensive investigation on experimental test of dust minimum explosible concentration (MEC) was carried out by using the Siwek 20 L vessel. Systematic data were reported on the MEC of various dusts and the influences of ignition energy, dust calorific value, moisture content and particle size were taken into account. It is found that the overly low or high ignition energy will result in unrealistic MEC results. To reliably measure MEC, the experimental tests should be preformed under the condition that the test result is independent of ignition energy. For the Siwek 20 L vessel, the 4-6 kJ is the most appropriate energy ranges to determine the MEC of various dusts. The more incombustible component contained in lower calorific value dust acts as a thermal sink in the ignition and heating process of dust cloud, and therefore, the higher MEC can be found in the MEC measurement of lower calorific value dust. Mo reover, due to the notable dust agglomeration, to validly measure MEC, the moisture content of test dust should not exceed 10 wt %. When the moisture content is lower than 10wt %, the MEC smoothly increases with the rise of moisture content. With the decrease of particle size, the measured MEC becomes lower, and the MEC has an approximate linear relation with particle size. The results reported in this work provide t he experimental basis and data guidance for the prevention and evaluation of dust explosion risk.

International Symposium on Safety Science and Engineering in China, 2012 (ISSSE-2012) An Extensive Discussion on Experimental Test of Dust Minimum Explosible Concentration

Weixing Huang

Papers

Experiment-based investigations of magnesium dust explosion characteristics

Experimental investigations of coal dust-inertant mixture explosion behaviors

International Symposium on Safety Science and Engineering in China, 2012 (ISSSE-2012) An Extensive Discussion on Experimental Test of Dust Minimum Explosible Concentration