Chemical looping combustion (CLC) is an emerging combustion technology with an inherent separation of the greenhouse gas CO₂. The technique typically employs a dual fluidized bed reactor system where a metal oxide is used as a solid oxygen carrier that transfers the necessary oxygen from air to the fuel combustion. In this work, a comprehensive simulation tool for the investigation of a CLC system consisting of two interconnected fluidized bed reactors is introduced. One-dimensional, dynamic fluidized bed reactor model is implemented into the Matlab/Simulink environment. The model is based on the conservation of mass and energy, and semi-empirical correlations are used for the calculation of reaction kinetics, hydrodynamics, and heat transfer. The main outputs of the model are the global solids circulation rate, the conversion of the carrier and the gas composition at the reactor exit, the vertical profiles of temperature, reaction rates and gas concentrations, and the distribution of solids in the reactors. For validating and evaluating the capabilities of the model, a reference case based on the operation of a 120kW_th CLC test rig was defined and simulated. Good agreement was observed between the experiments and simulations, and the model structure and submodel forms turned out to be appropriate to describe the studied process.