Cluster characteristics of Geldart Group B particles in a pilot-scale CFB riser. I. Monodisperse systems

Experiments in a circulating fluidized bed (CFB) riser with Geldart Group B particles have been carried out with an emphasis on cluster characterization. In this paper, the focus is on monodisperse materials; results for polydisperse materials are contained in the companion paper (Chew et al., this issue). A fiber optic probe was used for detection of solids, with the resulting solids cluster identification accomplished using wavelet decomposition. Three cluster characteristics were evaluated – appearance probability, duration, and frequency – as a function of riser position, operating condition, and type of solids (i.e., variations in particle size and/or material density). Results indicate that the riser position has the most dominant influence on cluster characteristics with the cluster appearance probability appearing to be largely a function of riser position only, and insensitive to changes in operating condition or material type. The cluster duration and frequency are influenced by the particle material and operating condition, though only from mid-height of the riser upwards. The results presented provide a comprehensive picture of factors affecting cluster trends. ► Experimental cluster behavior of three monodisperse materials throughout riser. ► Riser local position is the key influence of all three cluster characteristics. ► Operating condition and material type effects are secondary. ► Cluster appearance probability is largely influenced only by riser local position. ► Duration and frequency affected by operating condition and material near riser top.