Measuring the External Solids Flux in a CFB boiler

Paper in proceeding, 2006

In circulating fluidized bed (CFB) boilers, the flow rate of externally recirculated bed material is important, since it influences combustion, fluid dynamics, solids segregation and heat transfer. However, in CFB boilers (as well as in other industrial CFB units), the solids recirculation rate is difficult to determine, as no standard method is available to measure it directly. In this work, a methodology for measurement of the external solid flux is developed, based on heat and mass balances over parts of the return loop of a CFB boiler. Continuous measurements of temperatures and flow rates of gas and water entering and exiting different sections of the return loop are needed to determine both instantaneous and time-averaged solids recirculation rates. The method was evaluated in the Chalmers 12 MWth CFB boiler with good results.