In this study, we develop a model for the chemical-looping combustion system with a goal of determining the system behavior and the effect of important physical and operating parameters. We propose a model based on system invariants under thermodynamic equilibrium to obtain a computationally inexpensive model that can be utilized for advanced control studies. The system is represented by coupling the mole and energy balances of the system invariants along with the population balance of the particles and the shrinking-core mechanism. The model results are validated based on the experimental data from the literature. The simulated results show that the model is flexible enough to be used for different types of gaseous fuels and metal oxides. In the area of looping combustion, this work is the first in the proposal of a control-oriented model.