New Turbulent Model for Computational Mass Transfer and Its Application to a Commercial-Scale Distillation Column

Abstract

A new −εc model is proposed in this paper for solving the turbulent mass-transfer equation in order to obtain the concentration profile of chemical equipment, like the distillation column, without relying on the experimental measurement of the diffusivity of mass transfer. The computation is performed simultaneously with the computational fluid dynamics model, so that the velocity and concentration profiles as well as the efficiency of the equipment can be predicted at once for the equipment with nonideal flow and distributed mass transfer. The advantage of the present computational method is to discover the imperfections of flow and concentration distributions at the early stage of process design or to assess technically the effectiveness of the existing equipment, so that the necessary adjustment could be made for achieving higher efficiency. The feasibility of the present method is demonstrated by predicting the performance of a commercial-scale distillation column with eight sieve trays as reported by Fractionation Research, Inc. The computed results on the outlet concentration of each tray and the overall tray efficiency under various F factors as well as the turbulent diffusivity of mass transfer are respectively in satisfactory agreement with the experimental data published by Sakata and Yanagi (Inst. Chem. Eng. Symp. Ser. 1979, 56, 3.2/21−34) and Cai and Chen (Ind. Eng. Chem. Res. 2004, 43, 2590) for the FRI distillation column.