Steam boiler or steam generator is widespread equipment for energy conversion in the industry for obtaining steam and later electricity. Processes in energy states are complex and require the application of automatic control theory, which basically relies on mathematical models of objects and processes given in the state space. This approach requires knowledge of both the static and dynamic properties of the processes taking place in the thermoelectric plant. The general approach to mathematical modeling consists in setting bilas equations as well as an appropriate number of supplementary equations which, together with the previous ones, give a closed system of equations to be solved. In this paper, the second step in the modeling of a steam boiler is presented, and for the specific case, a simulation of the mathematical model was performed on the basis of experimentally collected data.