Chapter 13 - Maximum heat recovery and its consequences for process system design

Abstract

This chapter focuses on the three basic methods used for maximum energy recovery calculations, which include the composite curve (CC) plot, the problem table (Pr-T) approach together with heat cascade, and the grand composite curve (GCC) plot, all of which have identical limitations. The original CC and Pr-T methods are the ones that aimed at solving the maximum heat (energy) recovery (MER) problem. The GCC plot can be applied to solve a more general MUC problem, though the solution is restricted to cases where costing rules based on temperatures apply. The importance of the GCC plot lies in its wide application to heat and power integration issues, particularly to the design of utility subsystems, and the concept has been modified and extended in several works. The nonpoint utilities have temperature changes larger than the appropriate temperature interval range and thus, the designer does not know before solving the MUC problem whether some utilities are of the point type or not. Often, outlet temperatures are fixed by the designer at lower values for hot utilities or higher values for cold utilities within an admissible range. Although the cost of utilities is most often based on their heat loads, the designer should also consider their flow rates, as they also influence the cost of transportation.