The hydrodynamics of a FLUID COKING (TM) unit were investigated with computational fluid dynamics (CFD) by simulating a scaled cold flow model. Steady state flow hydrodynamics were then analysed by focusing on the local voidage distribution and solids velocity. The influence of simulation time on interpretation and analysis of results was evaluated first, and a short-time simulation was found to be able to provide useful information. The predicted flow behaviour was compared both quantitatively and qualitatively with previous experimental findings. The influences of nozzle-insertion, feed distribution, and solids circulation rate were investigated. The numerical simulations indicated that the nozzle insertion and solids circulation have little impact on the flow hydrodynamics for the range of conditions studied. (c) 2011 Canadian Society for Chemical Engineering