(391b) Microwave-Driven Distillation Separation Technology - Full of Breakthrough Opportunities in Electrified Chemical Processes

Microwave irradiation with selective heating characteristics has been confirmed to affect the relative volatility of binary mixture, which should push the development of novel separation technology based on the difference of dielectric property of the composition in chemical engineering. The application of newly electrified microwave heating to traditional processes of vapor-liquid mass transfer has given rise to many emerging process intensification technologies, such as microwave-induced evaporation separation and microwave-induced reactive (flash) distillation. In this presentation, we summarize the role of microwaves in the above processes from the driving power and microwave special effects; and briefly outline the bottlenecks in the current development to point out the research direction for subsequent fundamental investigations and industrial applications.

For modeling and design the separation process of microwave induced evaporation. A novel dimensionless number Z_MW was derived in the present study based on an assumption involving molecular radiators to explore the effect of dielectric and thermodynamic properties of the materials as well as the MW field intensity on the microwave-induced relative volatility change (MIRVC). Moreover, a quantitative correlation was established between MIRVC and Z_MW, whose model parameters were determined by fitting experimental data obtained from mixtures under MW irradiation. The correlation was also employed to predict MIRVC in data obtained from previous studies. The error range between the predicted and experimental values was within ±6%, indicating the validity of the proposed quantitative correlation.

Furthermore, a novel MW-VLE model was proposed to predict the VLE data of binary systems in microwave fields using system thermodynamic properties, dielectric properties, and electric field strength. For modeling, first, the influence of thermodynamic and dielectric properties on microwave-induced relative volatility change (MIRVC) was investigated experimentally in detail. It indicated that increasing the system dielectric loss difference, boiling temperature difference, and decreasing the thermal conductivity can enhance the MIRVC. Then, model characteristics parameters were obtained by fitting the VLE curves with/without microwave radiation. Afterward, the empirical correlation equations of MW-VLE were derived by correlating model characteristics parameters with mentioned above factors and electric field strength.

Finally, an innovative microwave-induced spray evaporator was developed to overcome the current defects. Furthermore, the experiments demonstrated an excellent separation efficiency of alcohol-water azeotropic systems are achieved via microwave-induced spray evaporator. Moreover, the experiments of several mixtures with different permittivity and dielectric loss were performed to elucidate the mechanism of microwave-induced relative volatility change (MIRVC). The experimental results revealed that the increase of high dielectric loss components in the vapor phase under microwave heating in comparative experiments verifies the inference that dielectric loss determines the direction of MIRVC.