A comprehensive diagnosis system was developed and applied to obtain detailed information on the mechanism of gas-solid contact in a circulating fluidized bed (CFB). In the present system pressure distribution and solid circulation rate can be continuously monitored. Particle concentration and the velocity of clusters were measured by optical fiber probes with a FFT analyzer.
The measured velocity distributions showed clearly the formation of annular flow in the riser. The annulus thickness changed little along the column height even though there existed a sigmoidal distribution of particle concentration. The cluster size increased downward in the annulus but in the core it was much smaller and mostly constant. It was found that the internal circulation is as strong as the external circulation. Examination of previous models indicated that the formation of the annular flow is tightly related to the presence of clusters.