The present study aims to analyze the interaction of chemical reactions, particle morphology change and hydrodynamics in fluidized-bed gasifiers. The char gasification ina batch fluidized-bed gasifier was modeled. The twofluid model approach was coupled with an extended version of the uniform conversion model accounting for inert ash fraction. Model assumptions were confirmed via measurement of char density, porosity and particle size distribution at different stages of conversion in a lab-scale fluidized-bed gasifier. The CFD model correctly predicts the effects of particle structure change on chemical reactions, approved by a first of its kind comprehensive validation against unsteady experiments. Based on the validated CFD model, the interaction of hydrodynamics and local particle density variations due to chemical reactions is analyzed, and the effect of the initial bed height is studied. The present study aims to analyze the interaction of chemical reactions, particle morphology change and hydro-dynamics in fluidized-bed gasifiers. The char gasification ina batch fluidized-bed gasifier was modeled. The two-fluid model approach was coupled with an extended version of the uniform conversion model accounting for inert ash fraction. Model assumptions were confirmed via measurement of char density, porosity and particle size distribution at different stages of conversion in a lab-scale fluidized-bed gasifier. The CFD model correctly predicts the effects of particle structure change on chemical reactions, approved by a first of its kind comprehen-sive validation against unsteady experiments. Based on the validated CFD model, the interaction of hydrodynam-ics and local particle density variations due to chemical reactions is analyzed, and the effect of the initial bed height is studied. (c) 2021 Elsevier B.V. All rights reserved.