Fluidized bed reactors for chemical application have been used for half a century. In the 1960s and early 1970s, work on fluidized bed combustion was carried out in the U.K. and U.S. At that time all work was devoted to bubbling beds; th eprime reason was not the combustino properties but the possibility of desulfurinzing in situ. After the oil crisis in 1973 more extensive worldwide work was started by many reputable boiler manufacturers. This paper examines the principles and application of the circulating fluidized bed combustion process.Units: Dual