Optimal synthesis of heat-and-power systems with multiple steam levels

Abstract

In this paper, the extension of the operating line method (Irazoqui, 1986, Chem. Engng Sci. 41, 5) for the optimal synthesis of heat-and-power systems with dominant power load to the more general case of multiple steam levels is made. The thermodynamic meaning of the optimality region, obtained as a necessary condition for optimality, is also uncovered. An interesting feature of the optimal solution for the integration problem with multiple steam levels is that integration gaps arise. The optimal solution is compared to other solutions which appear as natural alternatives to it on the basis of the same value of the total area of heat exchangers and the same total power output. They all show lower values of their efficiencies to generate shaft power.