| A task-oriented approach to the syntheses of flowsheets separating multicomponent mixtures, and the selection of the appropriate unit operation(s) has been developed.;Built in the environment of spreadsheet macros, PROSHEET (PROcess design spreadSHEET) was designed, based on a combination of heuristic and algorithmic approaches. The expert system is rule-based with the design knowledge organized into a query with system hierarchy, by dividing the main separation problem into subproblems. The subproblems were of two types, (a) split definition, and (b) unit operation selection. Heuristics helped in this subdivision. Each subproblem contains a series of ordered heuristics based on process characteristics and component properties.;PROSHEET has been designed to handle vapor-liquid, gas, and non-volatile solute/solvent separations. The knowledge base is governed by rules which are forward-chained, while the inference engine is governed by rules which are distracted chained, i.e., a combination of forward and backward chaining. Algorithms are used to calculate physical properties from a supporting database and make unit operation calculations.;The separation sequences recommended and the flowsheets developed for sample problems were compared to those found in commercial designs and process synthesis literature. The sequences recommended conformed to commercial designs and PROSHEET at times suggested considering alternative unit operations for a particular split. Although not considered a high-level programming language, spreadsheet macros clearly emulate a rule-based approach used by high-level languages, and the spreadsheet environment itself is very versatile for developing numerous other expert systems. |
