2. Application Collocation

Abstract

Fast fluidized bed (FFB) reactors have been widely used in the petrochemical industry, coal combustion, and calcining processes. Large gas throughput, essentially plug flow of gas giving higher selectivity for intermediate products, and excellent interparticle and interphase heat and mass transfer are derived from the fineness of particles and a high mean relative gas–solids velocity. Chemical reactions may be carried out almost adiabatically, with the high solids flux providing either a heat source or a heat sink to control the riser temperature. FFB provides a practical approach to implementing periodic operation. The high heat transfer coefficient between the suspension and the heat exchange surface may also lead to a uniform temperature profile throughout the reactor. FAB/CFB boiler has advantages like fuel flexibility, high combustion efficiency, excellent contribution to pollution control, good turndown and load following, simpler fuel handling and feed system, and high availability. In the circulating fluidized bed, prereduction of finegrained iron ore concentrate together with powdered coal proceeds without sticking at temperatures above 950°C. Sticking is prevented by an excess of carbon in the bed material and by the turbulent mixing behavior of the CFB. Computer software for application collocation is in use to make the application collocation easier.