Chapter 12 - Heat integration within process integration

Abstract

This chapter focuses on the heat integration system used in chemical industries. In a typical process system in chemical industries, there are process streams that need cooling, which are known as hot process streams, and there streams which require heating, known as cold process streams. In order to diminish the cost of utilities and environmental impacts, it is advantageous to integrate a heat energy system. The idea behind heat integration is to use heat energy of hot process streams to heat up cold process streams. Heat integration has been applied in industry for many years even before the era of systematic approaches to process integration that began in the 1960s. Heat integration is performed in central heat-exchanger networks (HENs), where hot and cold process streams from the basic process subsystems (BPS) are sent to the HEN, from where they reach their required thermal final states and are then sent back to the BPS or outside the system as products, by-products, or waste. Heating and cooling utilities are also transported to the HEN from the Utility subsystems (US) and often these utilities come back to the US as, for instance, cooling water. In a total heat integrated system, wastewater from water-using processes is further sent to the central water treatment station, where it is treated before being discharged to the environment or to additional treatment outside the site. The redistribution of treatment processes reduces both water usage and cost of wastewater treatment.