Economic Optimization of the Reflux Ratio of Two Components Stage Distillation Columns

Distillation columns are complex processes for modeling and controlling. These columns are significant parts of most chemical industries for separation of components. Control of this process is essential for achieving certain purity for products with a minimum cost. However, nonlinearities, multivariable interaction, non-stationary behavior and severity of disturbances inside the column made this process too complex for controlling. In this study a graphical method is applied to model steady state continues tow components distillation column. First, a MATLAB code was developed to solve the mathematical model of the column. Then, the column was simulated using HYSYS software. Finally, the reflux ratio of this column was optimized to minimize the operating cost. A formula is presented to calculate the optimum value of this reflux ratio as an exponential function of a certain economic parameter of energy prices and depreciation costs. It is resulted that at low energy prices or high equipment depreciation costs, the optimum reflux factor is high.