EXPERT SYSTEM FOR THE SEPARATION OF CLOSELY BOILING AND AZEOTROPIC MIXTURES

The formation of azeotropes or the occurrence of closely boiling components in a mixture precludes straightforward rectification as a method of separation. Instead, recourse must be taken to special distillation processes which overcome distillation barriers by admixture of auxiliary substances or exploitation of system-inherent properties. While the choice of suitable auxiliary substances is almost the only decisive factor in the design of extractive rectification processes, it is difficult to gain an overall view of the numerous variants possible owing to the different distillation properties of azeotropic mixtures. A sound approach is offered by the use of heuristic knowledge in the form of a knowledge-based expert system to establish the number of possible alternatives satisfying the present state of the art. Starting from a small number of readily available substance and mixture data, rectification processes suitable for the separation of closely boiling or azeotropic mixtures are selected and the corresponding process structures are generated. If necessary, the system initially suggest suitable auxiliary substances satisfying the demands of the special process in question. This paper presents a detailed description of the construction of the expert system for the choice of auxiliary materials and process generation, subdivided into pressure change, homoazeotropic, heteroazeotropic, extractive and multiple azeotropic rectification, the procedural strategy, and the explanatory components of this expert system.