Energy saving in distillation by combining vortex contact device and thermal effects

Abstract

• Energy efficiency assessment of the thermal distillation in the column apparatuses is presented. • Heat extra removed from the upper tray of the column leads to a decrease in heat flows by 9–12%. • Vortex contact devices provide an increase in the mole fraction of the light-volatile component in the liquid by 5.61%. Thermal effects are proposed to improve the efficiency of heat and mass transfer phenomena in distillation columns. The new design of the vortex contact device is developed. The paper investigates a combined use of the vortex devices that act as the contact stages of the distillation column and heat removal from the upper contact stage. Theoretical results on the distribution of vapor and liquid flows on each tray of the vortex device are obtained. The mass flow rate of the liquid phase as a result of the partial condensation of vapors is determined based on the amount of heat removed and the location of the tray with additional heat removal. A reduction in the mass flow rate of reflux during thermal distillation is experimentally established. The dependence of the average Murphree tray efficiency of the vortex contact stage is obtained depending on the reflux ratio at thermal distillation, which is confirmed experimentally. Experimental study shows an increase in the average efficiency of the stage by 10.6% compared to the adiabatic column without heat removal. A distillate mass fraction of 0.884 in the liquid phase is achieved at the outlet of the column when using 10 vortex contact stages and the working reflux ratio of 1.83. The comparative analysis of the use of the developed vortex contact devices in the thermal distillation process is performed in terms of the separation quality of the ethanol–water mixture, energy costs for the supply, and removal of heat.