Novel and fundamental strategies for equation-oriented process flowsheeting: Part I: A basic algorithm for inter-linked, multicolumn separation processes

Abstract

This paper is the first part of a two-part manuscript in which we propose a new equation-based approach to process flowsheeting. In part I, a simultaneous linearization algorithm to solve problems for inter-linked, multicolumn separation processes is presented. The new algorithm is an extension of our method for single-column problems based on the Pseudo-Binary-Mixture (PBM) concept [Ishii, Y., & Otto, F. D. (2001). An efficient simultaneous correction procedure for multi-component, multistage separation calculations for non-ideal systems. Computers and Chemical Engineering, 25, 1285–1298]. The PBM-based algorithm is capable of handling any flowsheet topology regardless of the number and form of recycle streams and is characterized by a greatly simplified matrix structure and the ability to solve complex EO flowsheeting problems with the same ease as for a single-column problem. Three example problems that have a large number of recycle steams demonstrate the robustness of the algorithm and as well as the flexibility and efficiency of EO flowsheeting. In part II the algorithm is extended for general-purpose process flowsheeting, including the ability to solve controlled simulation problems where design specifications are imposed and the ability to solve process optimization problems. As well, a new local thermodynamic interface to provide the derivative information required in EO flowsheeting is presented. The methodologies presented in this work successfully address many of the difficulties associated with current EO flowsheeting technology.