A SINGLE RADIOTRACER PARTICLE METHOD FOR THE DETERMINATION OF SOLIDS CIRCULATION RATE IN INTERCONNECTED FLUIDIZED-BEDS

A non-intrusive method is presented to determine the residence times o f a single particle in a facility composed of four interconnected flui dized beds (IFB) with glass beads fluidized by air above minimum fluid ization at ambient temperature, It uses a glass particle labelled with radioactive Na-24 or Ir-192 whose gamma-ray emissions are monitored b y two external NaI(Tl) scintillation detectors. It is shown that, with in the batch particles' size range, the mean residence time of the rad iotracer particle is practically independent of the radiotracer partic le size and the beds can be considered as practically ideally mixed ve ssels. It is further demonstrated that the method can adequately measu re the residence time distribution of the particles independent of the processes occurring within the system such as the generation of stati c electricity during fluidization. The presence of static electricity was found to substantially affect the mean residence time of the solid s. By relating the bed mass and the mean residence time of the radiotr acer particle, the solids circulation rate within the IFB can be obtai ned.