Development and application of a conceptual framework for chemical process synthesis--role of exergy methods in process synthesis

A conceptual framework for chemical process synthesis is developed and presented. The framework is fundamentally justified through the model for technical processes. The framework is used as the basis for the systematic study for the role of exergy methods in this study. The activity of synthesis is described by the framework in terms of a design task hierarchy which involves design stages and operations, design approaches, and design methods. Application of the framework for studying design methods are demonstrated in analyzing case design procedures and characterizing design approaches.; The role of exergy methods is studied by a systematic approach which identifies thermodynamic information used, defines the purposes and the ways that the information is used, and evaluates the effectiveness of the uses. Through the application of the framework to analyze representative exergy methods, thermodynamic information is used as (1) criteria for problem decomposition, (2) criteria for generating solutions, (3) evaluation criteria, and (4) objective functions. In varying degrees, thermodynamic information is shown to be effective for problem decomposition, generating solutions and as an evaluation criterion. It is not effective as a pure objective function.; For three uses, thermodynamic information and economic information are compared to evaluate the effectiveness of the use. With respect to the identification of a process change for improving energy efficiency in a typical petrochemical process, exergy costing analysis provides more direct information for determining a change than an economic analysis, additionally, it better reflects the effect of the change on other subsystems. Although pure thermodynamic quantities are not effective as objective functions, new thermodynamic functions which incorporate trade-off relationships compare favorably with venture cost objective functions for distillation column optimization. The thermodynamic evaluation criteria lost work and Carnot work of separation are found to be computationally effective substitutes for economic criteria under limited conditions. The dimensionless minimum isothermal work is not effective.