8.1 Introduction

Fluidized-bed combustion (FBC) is a leading technology for the combustion of a range of fuels, fossil and others, because of several inherent advantages it has over conventional combustion systems including fuel flexibility, low NO _x emissions, in situ control of SO ₂ emissions, excellent heat transfer, high combustion efficiency, and good system availability. The development of the fluidized-bed concept started in 1922 with the Winkler patent for gasification of lignite ^[1]. The first major implementation of the concept was around 1940 in the chemical industry to promote catalytic reactions. In the 1950s, the pioneering work on coal-fired fluidized-bed combustion started in Great Britain, specifically by the National Coal Board and the Central Electricity Generating Board ^{[2] [3]} . The U.S. Department of Interior's Office of Coal Research, one of the predecessors of the current Department of Energy (DOE), began studying the FBC concept in the early 1960s (and it still continues sponsoring research into advanced FBC systems as discussed later in the chapter) because it recognized that the fluidized-bed boiler represented a potentially lower cost, more effective, and cleaner method to burn coal ^[4] . In addition to Great Britain and the United States,other countries like Finland, Germany, and China started programs to develop fluidized-bed combustion, as they wanted to establish a technology that was able to utilize...