A Simple algorithm for the design of fully thermally coupled distillation columns (FTCDC)

Although material and thermal coupling between the prefractionator and main distillation column renders the fully thermally coupled distillation column (FTCDC) a frequently favorable design option, it also complicates considerably process synthesis and design. In this contribution, a simple algorithm for the synthesis and design of the FTCDC is derived with the optimization of an economical objective function. In terms of an initial process design chosen arbitrarily to meet the given product specification, the algorithm allows the treatment of the continuous operating variables (e.g., the vapor and liquid split ratios) and discontinuous structural variables (e.g., the number of stages in each column section) in a unified manner and permits searches of their optimum values sequentially in each iteration step. The proposed algorithm is characterized by great simplicity in principle and high robustness to the guess of initial process design and the thermodynamic properties of the mixtures separated. Five example problems dealing with the separation of various ternary mixtures with ideal and nonideal thermodynamic properties are employed to evaluate the proposed procedure, and the obtained results demonstrate its applicability and robustness to the synthesis and design of the FTCDC.