3186 



Chapter 26 



TUYERE 



COMBUSTION AIR PLENUM 



REFRACTORY 



CLOSED END 

 SECTION 



FUEL INLET 



AUXILIARY FUEL 

 BURNER 



HOT GAS 

 DISCHARGE 



COMBUSTION AIR 

 DAMPER 



CHOKE SECTION 



Figure 26-18. — Cyclonic burner and airflow pattern in cyclonic burner. (Drawing from 

 Energex Company.) 



minimum fluidization velocity is reached, the bed rsembles a violently boiling 

 liquid. On fluidization, the bed may expand to 1 Vi or 2 times its original static 

 depth. 



Fluidized beds have been used for many years in the petroleum and mining 

 industries for catalytic and ore reactors (Keller 1975). Most recently, they have 

 been adapted to combustion systems. Because of the large particle surface area 

 in the fluidized bed, rapid heat transfer occurs between gas and solids. As the 

 fluidized bed has high thermal inertia, fluctuations in heat input are dampened. 

 This permits combustion of wet and low-quality fuels that vary in heating value. 

 The mineral olivine has been found to be a suitable bed material as it is inert to 

 combustion temperatures up to 2000°F. Bed material wears out by attrition and 

 forms fines that are blown out of the system with the fluidizing gas flow. 



Fluidized-bed burners may be used with existing boilers or water tubes can be 

 inserted into the bed or placed in the wall of the burner. The hot combustion 

 gases can also be used for direct heat drying applications (Bryers and Kramer 

 1977; Wiley 1978). A modified gas turbine cycle coupled to a fluidized bed 



