Abstract: Chemical–looping combustion (CLC) is a promising oxyfuel carbon capture technology consisting of two interconnected fluidized beds with a metal oxide as a bed material/oxygen carrier. The particles, which circulate between both reactors, firstly absorb oxygen in the air reactor (AR) and secondly provide the oxygen for the combustion in the fuel reactor (FR). In this work, CFD simulation models for fuel and air reactor of the world’s second–largest CLC pilot plant at Technische Universität Darmstadt have been developed. An in–house thermochemical reaction model is combined with the two–fluid model implemented in ANSYS–FLUENT to simulate the gas-solid interaction of the FR and AR of the 1 MWth chemical–looping combustion pilot plant. All reactions, including the pyrolysis of coal, the gasification and oxidation of char and the reactions of the oxygen carrier are included by customized user defined functions (UDF). Stable, transient simulations of 55 s (FR) and 50 s (AR) were carried out. The FR simulation is showing a good agreement towards experimental measurements for the pressure drop. However, deviations occur in the gas composition between the simulation and the experimental data. Good agreement is obtained for the gas composition and the temperature in the AR. Slight discrepancies occur in the pressure profile between the numerical and experimental data. Possible reasons for deviations are discussed and appropriate solutions provided.