Distillation Column Modeling

Process simulation methods are used to evaluate the performance of proposed distillation systems and improve the performance of existing ones. The most common approaches for modeling distillation processes can be broadly divided into equilibrium and non-equilibrium methods. This article provides information about the differences between the two approaches and outlines their advantages and disadvantages. Due to the limitations in the assumptions used to derive each model and in the data required to accurately perform the calculations, neither model can be assumed to work best in all situations. Equilibrium models The longest-used (over a century) method for modeling a full distillation column is the equilibrium method, where the vapor and liquid phases are assumed to be in a state of thermodynamic equilibrium. Models based on ideal equilibrium stages are widely used to help determine the configuration of proposed columns. The approach is to divide the column into discrete stages and use computer programs to solve so-called MESH equations. The acronym MESH stands for material balances, equilibrium relationships, summation equations and heat (enthalpy) balances (Table 1). Since the 1950s, many algorithms have been developed to solve the…