Abstract: Chemical looping combustion (CLC) is a promising technology able to convert energy whilst managing CO2 emissions. The CLC system is composed of two fluidised bed reactors working in different hydrodynamic regimes. Transition metal particles circulate between the two reactors to carry out the oxidation and reduction reactions with air and fuel, respectively. This technology, which might be embedded into a fuel power plant for electricity generation, would lead to higher thermal plant efficiency than other technologies for carbon capture. The main concern about the technology is related to the total solid inventory needed to achieve full gas conversion which is believed to count for most of the cost of a CLC power plant. Thus, noteworthy attention is given to the modelling of the reactors to optimise the solid inventory and thus the plant’s cost. In this work, a 2D computational fluid dynamics (CFD) analysis of the fuel reactor is carried out. The results, in terms of the effect of the different kinetic and hydrodynamic conditions on the outlet gas conversion, are compared with the results using a macro-scale model implemented in Aspen Plus. Based on the micro scale (CFD) outcomes, the macro scale model is enhanced to capture the main physics influencing the performance of the fuel reactor. The latter is considered more suited as power plant simulator for thermal efficiency and cost estimations.