Point efficiency of sieve trays at elevated liquid viscosities

•New point efficiency data for four different test systems from 0.2 to 4.2mPas.•Viscosity effect on point efficiency decreases as viscosity is increased.•Upper limit of tray efficiency database extended from 1.5mPas to 4.2mPas.•New efficiency data at high liquid viscosities make correlation evaluation viable. Liquid viscosity plays a major role in determining the mass transfer efficiency in distillation through its contribution to the liquid-phase mass transfer coefficient, interfacial area of mass transfer, and vapor and liquid phase residence times. Most of the distillation efficiency correlations in the literature were developed or validated based on efficiency data at liquid viscosities less than 1.5mPas. However, distillation at liquid viscosities greater than 1.5mPas is encountered in practice in the chemical process industry. Therefore, distillation efficiency data at liquid viscosities greater than 1.5mPas are required to accurately quantify the effect of liquid viscosity on distillation efficiency and to develop improved efficiency correlations. Point efficiency defines the most fundamental mass transfer efficiency for distillation trays upon which tray and column efficiencies are calculated. In this paper, the effect of liquid viscosity on point efficiency of sieve trays is reported with new data for four different test systems at liquid viscosities ranging from 0.2 to 4.2mPas. These new data are critical for evaluating the validity of the existing tray and point efficiency correlations and for extending the existing correlations or developing new correlations for distillation column design at elevated liquid viscosities.