EXERGY AS AN OBJECTIVE FUNCTION TO MINLP PROBLEMS IN-PROCESS SYNTHESIS

The optimal layout of a chemical plant is determined by both economic and environmental aspects. The mathematical approach to this problem i s given by representing the process through a superstructure, includin g any foreseeable process topology. It is described by integer variabl es, whereas real variables arise from the unit models and the thermody namic calculations. By including process constraints and an objective function, a Mixed Integer Nonlinear Programming (MINLP) optimization p roblem is postulated. In this paper MINLP algorithms are combined with a technique for the exergy analysis of chemical processes for the pre liminary screening of process alternatives. The exergy analysis as a s creening technique is advantageous due to a significantly smaller amou nt of required data and computing time, compared with true optimizatio n, including cost estimation at an earlier stage of process synthesis and analysis. Thus, a broader solution space can be examined. The subs equent cost analysis has then only to be focused on a reduced set of p arameters.