Analysis of Mutual Transformations of the Structures of the Diagrams of Ternary Systems via the Formation of Binary Boun
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ysis of Mutual Transformations of the Structures of the Diagrams of Ternary Systems via the Formation of Binary Boundary Tangential Azeotropes T. V. Chelyuskinaa, *, A. V. Polkovnichenkoa, and D. D. Modurovaa aLomonosov
Institute of Fine Chemical Technology, MIREA – Russian Technological University, Moscow, 119571 Russia *e-mail: [email protected] Received December 16, 2019; revised January 20, 2020; accepted February 7, 2020
Abstract—A consideration has been made of mutual transformations of the structures of the vapor–liquid equilibrium diagrams of ternary systems without ternary azeotropes and with monoazeotropic and biazeotropic binary components through the formation of a binary boundary tangential azeotrope with varying external conditions. Specific features of the appearance of biazeotropy at the boundaries of the concentration simplex have been determined for ternary systems with different types of structures of the vapor–liquid equilibrium diagrams. Keywords: vapor–liquid equilibrium, diagram structure, biazeotropy, boundary tangential azeotrope, thermodynamic and topological analysis DOI: 10.1134/S0040579520040156
INTRODUCTION One of the most widely used methods of separation of organic substances in chemical engineering is distillation, which is characterized by high specific energy consumption [1–3]. The development of various processes of distillation separation of multicomponent mixtures and comparison of energy consumptions in these processes can be performed only if reliable data on liquid–vapor phase equilibria exist and are correctly interpreted. Considering the evolution of phase diagrams is quite a convenient tool to predesign distillation separation processes [4]. The discovery of biand triazeotropy abruptly increases the role of qualitative research methods [5]. Any transformations of a liquid–vapor phase equilibrium diagram occur according to tangential azeotropy theory [6–10], which determines the mechanisms of the formation (disappearance) of azeotropes with various numbers of components. With varying external conditions, the topological structure of liquid–vapor phase equilibrium diagrams may change or remain unchanged. Structures that exist without changes over a certain range of external conditions are called coarse. The transition of one coarse structure to another occurs through the formation of a fine structure existing at a single set of external parameters [6, 11]. The phenomenon of tangential azeotropy [12] is encountered in the practice of distillation and cannot be ignored in the production of special-purity substances by distillation methods.
Analysis of mutual transformations of the structures of phase equilibrium diagrams (SPEDs) in terms of the mechanism of the change in their topological structure determines general laws of transformation of zeotropic and mono- and biazeotropic systems and helps choose the best conditions for the separation of such mixtures by changing their SPEDs. Previously, we considered mutual transformations of the diagrams of distillation lines of
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