Minimum Ignition Temperature of Hybrid Mixtures Of Burnable Dusts and Gases

Investigation of the ignition behavior (minimum ignition temperature (MIT)) of hybrid mixtures of dusts and gases has been undertaken. This was achieved by performing series of test in the modified Godbert-Greenwald furnace. The materials used are, gases (methane, propane and hydrogen) and dust (starch, lycopodium, toner, wood and CN4 (mixture of bituminous and brown coal)). The test protocol for testing the MIT for dust was according to E1491–06 while in the case of gas and hybrid mixture the same standard was used but with slight modification. The experimental results demonstrate the significant decrease of the MIT of either gas or dust and increase in explosion likelihood when small amount dust which is either below the minimum explosion concentration or not ignitable itself are admixture with gas and vice versa. For example the MIT of methane decreases from 600°C to 530° when small amount of toner which is not ignitable at the MIT of methane was added to it. The same effect was noticed when a small amount of gas was added to dust for example, wood with MIT of 460°C decreases to 420°C when a small amount of methane which is not ignitable at the MIT of wood was added. The result also confirm that an explosion is possible for a process or a system where hybrid mixtures are generated even if the temperature is below the MIT of a single substance and hence the MIT of hybrid mixtures cannot be predicted by simply overlapping the effects of the single dust or gas. Keywords; minimum ignition temperature, hybrid mixture explosion, dust explosion, gas explosion