Effect of stirring on the safety of flammable liquid mixtures

Abstract

Flash point is the most important variable employed to characterize fire and explosion hazard of liquids. The models developed for predicting the flash point of partially miscible mixtures in the literature to date are all based on the assumption of liquid-liquid equilibrium. In real-world environments, however, the liquid-liquid equilibrium assumption does not always hold, such as the collection or accumulation of waste solvents without stirring, where complete stirring for a period of time is usually used to ensure the liquid phases being in equilibrium. This study investigated the effect of stirring on the flash-point behavior of binary partially miscible mixtures. Two series of partially miscible binary mixtures were employed to elucidate the effect of stirring. The first series was aqueous-organic mixtures, including water+1-butanol, water+2-butanol, water+isobutanol, water+1-pentanol, and water+octane; the second series was the mixtures of two flammable solvents, which included methanol+decane, methanol+2,2,4-trimethylpentane, and methanol+octane. Results reveal that for binary aqueous-organic solutions the flash-point values of unstirred mixtures were located between those of the completely stirred mixtures and those of the flammable component. Therefore, risk assessment could be done based on the flammable component flash-point value. However, for the assurance of safety, it is suggested to completely stir those mixtures before handling to reduce the risk.

Prediction of miscible mixtures flash-point from UNIFAC group contribution methods

“…In 2007, a gasoline tanker crashed and burst into flames near the San Francisco-Oakland Bay Bridge, resulting in a stretch of highway melted and collapsed [4,5], highlighting the importance of safe transportation for flammable and combustible liquids. The fire and explosion hazard of liquids is primarily characterized by their flash point [6].…”

Relationship between flash points of some binary base oils and their constituent oils

“…Moreover, the flash point behaviors for miscible mixtures and immiscible mixtures are quite different. The mixtures displayed in Figures 1 to 3 seemed to be miscible mixtures, the ones displayed in Figures 4 and 5 seemed to be partially miscible mixtures, and the ones displayed in Figure 6 seemed to be almost completely immiscible mixture [33][34][35][36][37][38][39]. …”

On the relation between azeotropic behavior and minimum / maximum flash point occurrences in binary mixtures of flammable compounds

“…All these methods, excluding Wickey and Chittenden's and Catoire et al's models, consider vapor-liquid equilibrium (VLE) for all components and we keep this hypothesis here with some nuances explained later. Do notice however that non-equilibrium conditions (such as not stirring in the liquid phase) can affect flash point behavior [8]. Nonetheless, this effect has been observed only in partially miscible systems, and such systems are out of the scope of this study.…”

“…The graphics (3 0 ), and (4 0 ) represent maximum azeotrope mixtures, as predicted by equation (9). Also, plots (3) and (4) represent minimum azeotropes predicted by equation (8). One can see from plot number (5) that equations (8) and (9) fail to forecast double azeotropes.…”