Chapter 7 - Steam Systems

Abstract

Steam systems are vital to commercial, industrial and thermal power plants. The five major steam intensive industries are food processing, pulp and paper, chemicals, petroleum refining, and primary metals. Given the large dependency on steam, in an environment of increasing energy costs and a focus on climate change, increasing steam efficiency allows businesses to be competitive and an opportunity to save energy, water and reduce greenhouse gas emissions. A steam system consists of five sections namely pre-treatment, steam generation, steam distribution, end use and steam recovery. Boilers are characterized by their application, configuration, size and quality of steam produced. By configuration boilers can be classified as firetube, watertube, waste heat boilers, electric boilers, hot water boilers and once-through boilers. In industry, the most common are firetube, watertube, and wasteheat boilers and these form the focus of this chapter. Firetube boilers are used principally as heating systems for industrial process steam or as portable steam-generating units. These types of boilers are used in applications where steam demands are relatively small or require only saturated steam. Watertube boilers, due to their ability to withstand high pressures are used in high-pressure systems. The circulation in water tube boilers can be forced or natural. Waste heat boilers are unfired boilers and are used in heat recovery applications to generate steam. They may be either watertube or firetube design and use heat that would otherwise have gone to waste. Ammonia and ethylene plants have unique waste heat recovery boiler designs. This chapter also discusses a number of steam and energy conservation opportunities in steam plants.