On the gasification of droplets of azeotropic mixtures: Theory and experiment

Recognizing the potential formation of azeotropic mixtures from blending hazardous chemical wastes for incineration, a fundamental experimental and theoretical investigation of the volatility reversal and gasification characteristics of droplets of azeotropic and zeotropic mixtures has been conducted. Experimental results on the temporal variation of the droplet composition of binary positive azeotropic mixtures show that while the low-boiling-point component indeed gasifies faster throughout the droplet lifetime for low initial concentrations, it becomes the slower gasifying component at high initial concentrations. Consequently there exists an intermediate, azeotropic point such that a droplet at this initial composition will remain so throughout its lifetime. This gasification azeotropic point is different from the thermodynamic azeotropic point and is determined by the specific droplet combustion parameters. Corresponding control experiments on zeotropic mixtures show that the more volatile component remains as the faster gasifying component for all initial concentrations. Theoretical calculations on binary mixture droplets completely substantiate the experimental observations. The behavior of the azeotrope with the addition of a third component of greater or lesser volatility has also been examined. Experiments on some ternary mixtures show that the azeotropic behavior can be broken, for additions of either volatility.