Experimental and modelling investigations of the hydrodynamics of the internal flow structure in the circulating particulate bed electrode (CPBE) are reported. The CPBE, a hybrid between an expanded packed bed and an entrained/fluidized bed, is particularly well suited for many electrochemical applications such as metal recovery and pollution treatments for metal containing effluents. This study deals with the fundamental hydrodynamics and particle dynamics of the CPBE. A mathematical model of the CPBE has been developed which successfully describes the motion of the particles and the fluid in the bed. It is shown that many of the flow characteristics of the circulating bed can be predicted using fundamental data. The validity of the proposed model was demonstrated by comparing predictions to experimental observations of several bed characteristics under various operating conditions. The conditions necessary for a stable circulating particulate bed are defined.