Abstract
In 2005, an investigation conducted on three nanoscale attrition millers in Taiwan revealed that all three had undergone metal nanopowder explosions in the past. This research was aimed at determining the relationships between the particle diameter of an aluminum nanopowder and its maximum explosion pressure (Pmax), maximum rate of pressure rise ((dP/dt)max), minimum explosion concentration (MEC), and minimum ignition energy (MIE) by 20 liter apparatus and 1.2-L Hartmann apparatus. The results revealed that 35-nm aluminum powder has a Pmax of 7.3 bar and deflagaration index (KSt) of 349 bar•m/s, in 100-nm aluminum powder, Pmax of 12.5 bar and KSt of 296 bar•m/s and 40-μm aluminum powder, Pmax of 5.9 bar and KSt of 77 bar•m/s. The value of (dP/dt)max for the 35-nm aluminum powder is 4.5 times that for the 40-μm aluminum powder. The 35-nm, 100-nm, and 40-μm powders have MEC values of 40, 50, and 35 g/m3, respectively. The 35-nm and 100-nm powders both have MIEs less than 1 mJ, while the 40-μm powder has an MIE of 59.7 mJ.
Highlights
Mechanical attrition milling is still the main technique used in the mass production of nanopowders in Taiwan
The results revealed that 35-nm aluminum powder has a Pmax of 7.3 bar and deflagaration index (KSt) of 349 bar·m/s, in 100-nm aluminum powder, Pmax of 12.5 bar and KSt of 296 bar·m/s and 40-μm aluminum powder, Pmax of 5.9 bar and KSt of 77 bar·m/s
The experiments in this research were conducted according to the BS EN 13821 experiment standard (British Standards Institution, 2006), according to which, a given quantity of powder dust is concluded as being combustible at a specific ignition energy if at least one successful combustion trial exists in ten experimental trials of the same powder quantity and ignition energy, the minimum ignition energy (MIE) is the value between the maximum no ignition energy (NIE) and the minimum energy for powder ignition (IE)
Summary
Mechanical attrition milling is still the main technique used in the mass production of nanopowders in Taiwan. It is a relatively low-cost process but is scaled up for mass production. Mechanical attrition milling has better controllable parameters and can be used to mill the powder particles down to 30 nm in diameter. The principle of the nano-powder grinder is to use high speed air to make the powder collide mutually. It causes the powder turns a nanometer scale from micron scale. All factory happen dust explosion when raw material containing Al feed to nano-powder grinder in Taiwan
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