A New Concept for Operation of a Pulverized Coal Fired Boiler Using Circulating Fluidized Bed Firing

The feasibility of adapting existing pulverized coal fired boilers slated for life extension to circulating fluidized bed firing is examined by considering the case of a 150 MWe tangentially fired pulverized coal boiler. The proposed modifications call for a minimum of change in existing units. Thermal calculations are presented to show how heat absorption in different sections of the converted boiler can be matched to that in the pre-existing pulverized coal fired boiler. Data for two load conditions are presented to identify problems associated with low loads. Fuel flexibility in the converted circulating fluidized bed unit is shown by repeating the thermal calculations for coal washery rejects. It is concluded that the adoption of circulating fluidized bed firing is thermodynamically feasible.