Evaluation of the Efficiency of Vortex Contact Devices in a Diabatic Distillation Column

Abstract

One of the most important criteria in the development of column mass transfer apparatuses is a high separating ability. This goal can be achieved by improving contact devices, as well as directly influencing the process itself. A vortex contact device has been developed, which consists of two coaxial pipes. There are slots on the surface of the inner tube; as vapor passes through the slots it begins to twist, forming a vortex dispersed–annular vapor–liquid flow in the annulus. The liquid flowing down from the upper contact stage is broken up into separate drops under the action of centrifugal forces and thrown to the wall of the vortex device, where a film flow is created. To implement the process of diabatic distillation, the vortex contact stage is equipped with a cooling jacket, where the coolant is supplied. On the example of this vortex contact device for diabatic distillation, the possibility of increasing the separating power of contact devices is considered. By tray calculation, the compositions and flow rates of the liquid and vapor phases at each stage of the column are determined. The process of diabatic distillation is carried out by removing heat from the stages of the rectifying part of the column. Calculations are made both with heat removal only from the upper stage of the column, and with different amounts of heat removed from the upper four stages of the column. The influence of thermal effects on the Murphree efficiency index is determined for various design parameters of the vortex contact device and various operating modes of the distillation column. The results obtained are compared with similar indicators of calculations of adiabatic distillation. The greatest increase in efficiency according to Murphree is achieved with an increase in the Reynolds criterion, as well as with an increase in the ratio of the height of the swirling vapor–liquid layer to the height of the slot of the vortex contact stage for the passage of vapor. It is established that additional heat removal makes it possible to increase the efficiency of the Murphree vortex contact device by 11% compared to adiabatic distillation.