Separation system synthesis: A knowledge-based approach

This work concerns the development of a systematic, comprehensive approach to the synthesis of separation sequences for fluid mixtures, the Separation Synthesis Hierarchy (SSH). The knowledge structuring approach of the SSH has been implemented for liquid mixtures as a knowledge-based expert system, the Separation Synthesis ADvisor (SSAD). The validity of the synthesis methods is demonstrated for several industrially significant separation problems.; The synthesis of separation sequences is a classical chemical engineering design problem. Given physical property data and product specifications for an n-component mixture, the goal is to find the separation method(s) and sequence(s) which produce the desired products in an optimal or near-optimal process design. The human design expert superbly handles this complex endeavor consisting of interrelated selection, sequencing, design subproblems. However, in order for an expert system to emulate the process and to reach a comparable level of performance the following questions must be addressed: (1) Can the separation problem be decomposed into tractable selection, sequencing, and design subproblems? (2) What knowledge is needed to ensure expert-level performance and how should it be organized?; The Separation Synthesis Hierarchy decomposes the overall separation synthesis problem into four similarly-structured problem-solving activities dealing with phase separation as well as distillation, liquid-phase, and gas phase separations. These activities are further divided into distinct separation method selection, separation sequencing, and separation design subproblems. The problem-solving structure of each of the three types of subproblems is explicitly developed and presented with the pertinent separation synthesis domain knowledge.; In its current implementation, the SSH utilizes the following separation methods for the preliminary sequencing of multicomponent liquid/gas mixtures: (1) Simple distillation; (2) Azeotropic/extractive distillation; (3) Cryogenic distillation; (4) Liquid-liquid extraction; (5) Adsorption; (6) Membrane permeation; (7) Mel crystallization; (8) Physical, chemical adsorption; (9) Catalytic conversion.; This list includes the separation methods commonly encountered in industrial practice; other separation techniques are used occasionally. However, the structure of the SSH is such that further separation methods can be added as knowledge becomes available.