TABLE OF CONTENTS The utility systems supply the heating and cooling needs which cannot be met by heat exchange, and Section 3.4 introduced the concept of multiple utilities. In this chapter we take this one stage further by looking at the interaction of heating and cooling utilities with power requirements, covering the following:
Combined heat and power (CHP) systems, which generate power while simultaneously providing hot utility (Section 5.2).
Heat pumps, using power (or high-grade heat) to reduce both hot and cold utilities (Section 5.3.1).
Refrigeration systems, providing below-ambient cooling requirements and consuming power (Section 5.3.2).
Total site analysis, optimising the heating, cooling and power requirements of an entire multi-plant complex (Section 5.4).
Economic aspects are included, as are case studies (Sections 5.5 and 5.6).
Most chemical processes and their associated sites do not just require heat; they require power as well. This power may be used to drive electric motors, pumps, or compressors, power for instruments and visual displays, and lighting. Most sites pay to import this power in the form of electricity from an external supply company, but the power itself must ultimately be generated somehow. In some countries, a significant proportion is produced by hydroelectric or tidal power or using other renewable sources. However, in most cases, the vast majority of power is generated from heat engines.
A heat engine is a device for converting heat into power. The high-temperature heat is provided by burning coal, oil, natural gas...
