Hybrid Flammable Dust-Gas Cloud Ignition Using a Modified Standard Minimum Ignition Energy Device
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Hybrid dust-gas explosion is a persistent problem in process industries because of its ease of ignition as well as serious consequences. Ease of ignition is quantified by minimum ignition energy (MIE), which is associated with the probability of ignition for a hybrid mixture. This study aims at improving the MIE measurement of hybrid dust-gas system using a modified Kühner MIKE3 MIE apparatus with an add-on purge device in order to purge the Hartmann tube with the gas mixture before the dust dispersion. It allows the gas composition in the Hartmann tube to be the same as that of the gas used for dispersing the dust. In this study, a typical hybrid system of Pittsburgh Pulverized Coal (PPC)- methane-air, was utilized to accomplish the tests, where two sizes of PPC with equivalent polydispersity was applied. Methane was pre-blended with ultra-high purity (UHP) air (21% oxygen and 79% nitrogen) at 1 vol %, 2 vol %, and 3 vol %. MIE testing was conducted for the following two cases: case (a) and case (b). Case (a) followed the ASTM E2019-03 standard procedure, while case (b) applied the pre-ignition Hartmann tube purge with 1 vol %, 2 vol %, and 3 vol % methane prior to dust dispersion and ignition. The testing was also divided into two sections: Section 1 including case (a1) and (b1) used the original dried PPC, while section 2 including case (a2) and (b2) used the milled PPC. Comparison of MIE values for both cases in both sections displayed significant differences. The hybrid MIE values obtained in case (b) are overall lower than those in case (a), illustrating that pre-ignition tube purge decreased the hybrid MIE value and gave more conservative MIE results. While smaller size of dust possessed lower hybrid MIE, similar trends in percent of MIE reduction revealed the impact of gas concentration on decrease of hybrid MIE regardless the particle size. Moreover, this study proves that previous hybrid MIE data generated using the ASTM E2019-03 standard procedure and utilizing the Hartmann apparatus and Kühner MIKE3 device yielded non-conservative results and should be validated through further studies by incorporating pre-ignition Hartmann tube purge into the hybrid MIE test procedure.
Han, Haitian (2017). Hybrid Flammable Dust-Gas Cloud Ignition Using a Modified Standard Minimum Ignition Energy Device. Master's thesis, Texas A & M University. Available electronically from