Novel representation of vapour-liquid equilibrium curves for multicomponent systems: design of total reflux distillation columns

McCabe Thiele diagrams were developed as a graphical tool for designing binary distillation columns. In this article, the method to construct McCabe Thiele diagrams for multicomponent systems is presented, illustrating specifically at total reflux for ideal and nonideal systems. Firstly, a variety of examples were used to depict the novel representation of the vapour-liquid equilibrium (VLE) in two-dimensional space (2D) as contours of VLE for the generation of the x–y diagram. Once the contours of VLE are represented in 2D various design scenarios can be investigated using the generated plot. Hence the proposed graphical method retains the authenticity, simplicity and versatility of the binary McCabe Thiele method. Through examples, it is shown that the depiction of the contours of VLE is a powerful visual tool to identify the type of separation (difficult or simple separation), azeotropes and tangent pinch points. Thereafter, the procedure for calculating the number of stages is presented at total reflux for ideal and nonideal ternary systems to determine the minimum number of stages required. Several simulations for an acetone, benzene and chloroform system were generated using Aspen Plus™ to validate the proposed graphical method. Lastly, it was shown that the proposed graphical method correlated more closely to rigorous simulation than traditional methods.