Design and Modeling Studies of Internally Heat-Integrated Distillation Columns

• Main Authors: Tsung-Jen Ho, 何宗仁
• Other Authors: Liang-Sun Lee
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/07698134775199009331

博士 === 國立中央大學 === 化學工程與材料工程研究所 === 98 === The heat-integrated distillation column, generally called HIDiC, applies the principle of internal heat integration between the rectifying section and the stripping section of a distillation column by increasing the temperature of the rectifying section with a compressor. First part in this work, theoretical stage-to-stage study of a HIDiC based on the Ponchon–Savarit method is performed. Several HIDiC design variables, such as the number of theoretical stages, reboiler (or preheater) duty, minimum overall internal heat-transfer rate, and configuration, can easily be interpreted in the Ponchon–Savarit (Hxy) diagram. Such an approach brings new insights into and better understanding of the features of HIDiC. A preliminary (or shortcut) HIDiC design procedure using Hxy diagrams is also proposed. The obvious advantages are that the proposed method allows the direct design of a HIDiC, and avoids trial-and-error design in using a commercial simulator. In addition, the proposed graphical method can foresee possible pinch points before requiring use of a rigorous simulator. Furthermore, the proposed graphical estimation of internal stages of a HIDiC is applied to a binary, methanol–water system, and compared to the rigorous simulation obtained using Aspen Plus. Second part of this thesis reports a dynamic simulation study of the internally heat-integrated distillation column (HIDiC) using equilibrium-based models. First, three different HIDiC structures, i.e. an ideal HIDiC, a HIDiC with a preheater, and a HIDiC with a reboiler, are analyzed by control degrees of freedom (DOF). The reboiler is considered to be a necessary part of the HIDiC from DOF analysis, thermodynamic analysis, and engineering judgment. Then, a heuristic HIDiC control configuration including a bottoms reboiler control is proposed. A modular structured simulator for dynamic distillation columns using MESH equations is developed. A typical medium-pressure HIDiC for separation of propylene and propane explored by Olujic et al. [ ] is adopted as numerical examples for dynamic simulation studies. Keywords: Heat-integration distillation column, Ponchon–Savarit method, Dynamic simulation, Distillation design, Distillation control.