The prerequisite for the optimization and control of many industrial processes is having a model. It should be accurate and fast to prepare an appropriate estimation of the process. The exhaust system plays a significant role in the electric arc furnace process and, therefore, its optimization is investigated in this work. An unsteady and nonlinear model of the fluctuating off-gas flow through the exhaust system is presented based on the mass and energy conservation laws. The thermodynamic calculations are facilitated by modular based modeling and also the model is implemented equipmentwise to cover all possible arrangements in the dedusting system. A Sankey diagram of the whole system is illustrated to examine the heat recovery potential of the off-gas cooling system.