Flammability assessments of sonication process in organic mixture

Abstract

The prospect of sonication phenomenon in facilitating separation of azeotropic mixtures calls for more detailed study towards developing an intensified distillation system. One important element that require in depth consideration is safety since ultrasound is a potential ignition source with a low threshold value of 1 mW/mm2. In this study, the aim is to investigate the potential of fire hazards that may be introduced by sonication when used in the environment of flammable organic liquid. Simulation study in MATLAB programming environment is carried out based on a mathematical model developed using first principle. Simulations of bubble conditions covering its whole life cycle regimes are carried out and validated with experimental works. Evaluation is made for an extreme condition where the ultrasonic waves are focused directed towards a stainless steel target material immersed in ethanol-water mixture. As sonication occurs, bubbles form slowly by rectified diffusion process with radius of 6 μm, and move toward the metal target. The experimental results revealed that cavitation bubbles filled with explosive vapor are not ignited. This is consistent with the simulation study where the maximum energy released during the bubble collapse is found to be small, which is 0.19267 pJ compared to minimum ignition energy of the liquid at 0.23 mJ. This concludes that the focused ultrasound wave in organic liquid does not trigger ignition, thus suggesting the ultrasonic distillation system is potentially.