Exergy load distribution approach for multi-step process design

The purpose of this study is to develop a new procedure for process synthesis based on a reducible superstructure, and exergy load distribution analysis. The latter makes it possible to evaluate the impact of each competitive process included in the superstructure according to the specific performance criterion of the overall flowsheet. This criterion, utilizable exergy coefficient, is a function of three important aspects of the process design: efficient use of raw materials, energy efficiency and waste reduction. The procedure starts by building a specific reducible structure of the process flowsheet called the "competitive process" superstructure. The exergy load distribution analysis is carried out on the "competitive process" superstructure to reduce it to a final optimal flowsheet topology. The new procedure is tested for the design of a benzene synthesis chemical plant and is compared with previously published solutions found by the hierarchic and mathematical methods. The new flowsheet consumes the least amount of raw materials and produces the least amount of discharged gas as waste. (C) 2000 Elsevier Science Ltd. All lights reserved.