Flash Point for Ternary Partially Miscible Mixtures of Flammable Solvents

Flash point is the most important variable used to characterize fire and explosion hazard of liquids. Herein, partially miscible mixtures are presented within the context of liquid−liquid extraction processes and heterogeneous distillation processes. This paper describes the development of a model for predicting the flash point of multiple partially miscible mixtures of flammable solvents. The validation of the model is done by comparing the predicted values with the experimental data for the ternary mixture with one partially miscible binary pair, methanol + toluene + 2,2,4-trimethylpentane, and the one with two analogous pairs, methanol + acetone + decane. Results reveal that the flash points are almost constant in each tie line that is inherently a vapor phase property. Liquid immiscibility could lead to mixture flash point lower than or equal to that of the lowest boiling pure compound, increasing the fire and explosion hazard. Use of activity coefficient models like UNIQUAC and NRTL is needed to describe the nonideal behavior of the liquid phase. Overall, the model describes the experimental data well when using the VLLE and the VLE activity coefficient model binary parameters to estimate sequentially the span and flash point in each tie line and the flash point in the mutual solubility region, respectively. Potential application for the model concerns the assessment of fire and explosion hazards and the development of inherently safer designs for chemical processes containing partially miscible mixtures of flammable solvents.