Partial inerting of dust clouds using a modified standard minimum ignition energy device
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2017 Elsevier Ltd Partial inerting is an important but underutilized mitigation technique in which minimum ignition energy (MIE) of a dust cloud is increased through inerting, reducing the risk of an accidental dust explosion or more accurately, a dust deflagration. This technique has wide application potential in numerous chemical and general manufacturing industries. The Khner MIKE3 is the predominant apparatus for measurement of the minimum ignition energy (MIE) of combustible dusts worldwide. The current version of the MIKE3 device is not specifically designed to measure partial inerting minimum ignition energies. The purpose of this work is to demonstrate that a properly designed add on purge device and technique can accurately produce partial inerting MIE results with an existing MIE device. The purge device ensures complete purging of the Hartman dust dispersion tube with the desired gas concentration before experimentation. The same gas is then pulsed into the dispersion tube producing the dust dispersion for ignition testing. This approach leads to uniform testing conditions in the tube with respect to gas concentration which is essential for producing proper measurements. Additionally, experiments show the turbulence generated by the purging technique did not significantly affect the MIE measurements. Therefore, an important finding of this work is that purging the tube before partial inerting MIE testing results in a proper characterization of the relationship between the MIE and oxygen for the dust. The findings therefore demonstrate the need to amend existing or develop new standards for this type of dust testing. The effect of these modifications and techniques are demonstrated by the experimental determination of the partial inerting curve for Niacin (CaRo15) using the Khner MIKE3 apparatus.
