Minimum Ignition Temperature of Dusts, Gases, and Solvents Hybrid Mixtures

Abstract

ABSTRACTInvestigation of the ignition behavior (minimum ignition temperature [MIT]) of dusts, gases, or solvents and their mixtures has been undertaken by performing a series of tests in the modified Godbert–Greenwald furnace. Four flammable gases (methane, propane, ethanol, and isopropanol) as well as three combustible dusts (starch, lycopodium, and toner) were used as materials. For the dusts alone test, the experimental protocol was in accordance with the European standard EN 50281-2-1, whereas for the gases, solvent vapors, and mixtures of these with the dusts, this protocol had to be modified slightly. The experimental results demonstrate the significant decrease of the MIT of either gas, solvent, or dust and an increase in the explosion likelihood when a small amount dust, which is either below the minimum explosion concentration or not ignitable itself at the given temperature, are admixed with gas or solvent and vice versa. For example, the MIT of methane decrease from 600°C to 585°C when a small amount of starch was added. This hybrid MIT further decreased to 490°C when a third component (ethanol) was added. The same effect was noticed when a small amount of gas was added to a dust; for example, toner with a MIT of 460°C decreases to 450°C when a small amount of ethanol was added, which further decreased to 430°C when a third component (propane) 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, gas, or solvent.