A model library has been created to describe gas-solid reactors for chemical looping combustion (CLC). CLC allows oxidation of a hydrocarbon fuel avoiding direct mixing with combustion air. Metal oxides are used to transport oxygen from one fluidized bed reaction zone to another, undergoing repeated cycles of oxidation and reduction. The equation-oriented IPSEpro environment is used for implementation. The models are based on conservation of mass and energy and allow calculation of the thermodynamic equilibrium with the thermodynamic data of different metal oxide systems implemented. The model assumptions are made in accordance with operating experience from laboratory installations. The characteristics of the technology are discussed using the presented models for the two fluidized bed reactors. The modeling tool allows investigation of integrated power plant configurations based on CLC technology.