Introduction of Point Efficiency into Unsteady-State Distillation Calculation

Abstract

Many distillation calculation methods at the steady state incorporaing various kind of point efficiencies have been developed for obtaining the actual distillation column composition profile, but a calculation method at the unsteady state incorporating the point efficiency for calculating the time dependence of the column profile from start-up to the steady state has not yet been reported. Here, a method to introduce point efficiencies into the unsteady state distillation calculation is proposed. The principle is as follows : the vapor compositions are eliminated from the derivatives by using the definition equation of point efficiency, so that numerical integration can be carried out with a function of only the liquid compositions. The efficiencies tested are the Murphree vapor, the Murphree liquid and the Hausen efficiencies. Generally speaking, the time required to reach the steady state increases with efficiency increasing. This method is also applicable to the Relaxation method.