Chapter 7 – Heat Integration

Publisher Summary This chapter presents the key tools used in identifying rigorous targets for minimum heating and cooling utilities, selecting utilities, and synthesizing HENs that attain the desired targets. Heating and cooling are among the most common operations in the process industries. Significant quantities of external heating and cooling utilities are used to drive reaction, induce separation, and render units and streams in desirable states of operation. To satisfy the need for heating and cooling, industrial operations require the extensive use of different forms of energy. The basic idea for heat integration is that there are process streams and units that need to be heated and other process streams and units that need to be cooled. Before using external utilities to provide the necessary heating and cooling, heat integration seeks to transfer the heat from the process hot streams and units to the process cold streams and units. To accomplish the minimum usage of heating and cooling utilities, it is necessary to maximize the heat exchange among process streams. In this context, one can use a very useful graphical technique referred to as the thermal pinch diagram. Notwithstanding the insights obtained by the graphical thermal pinch diagram, in some cases, it is desirable to use an algebraic approach, such as problems with numerous streams with much overlapping that can render the construction of the composite curves cumbersome.