Gas-solid fluidized-bed reactors are complex systems that involve multiple interrelated phenomena. One key phenomenon that affects reactor performance is the change in gas volumetric flow. The volumetric flow in a fluidized-bed reactor can change with height due to reaction, feed distribution, change of phase, selective removal/addition of species and changes in temperature and pressure. This paper presents results from an experimental program and gives a qualitative comparison with modeling results obtained with computational fluid dynamics (CFD). A high-pressure two-dimensional column was used to investigate the effects of sudden increase/decrease in pressure on fluidization behavior by recording multiple bubble properties using high-speed video recording. A CFD model was developed to investigate the same variations in process conditions. Changing the volumetric flow can radically alter the bed hydrodynamics. The CFD code is able to predict the experimental trends correctly. (C) 2013 Elsevier Ltd. All rights reserved,