The catalytic methanation of steel mill gases under dynamic conditions has great potential in reducing internal energy requirements and integrating renewable energies into the steel mill. For an economical and competitive power-to-gas process, the sub-steps are being modeled and simulated within the EU project i³upgrade with an intelligent control strategy. In the present thesis a model of the methanation plant with three fixed-bed reactors connected in series was created at the Chair of Process Technology and Environmental Protection using Matlab® Simulink, which is intended to represent the real behavior of the plant. The product gas stream and the catalyst temperature of each reactor were transferred to the control strategy as target variables. To allow a continuous communication with the control strategy, the outgoing gas streams of each reactor were calculated with experimentally determined H2, CO and CO2 turnovers. For a quick determination of the thermal load on the catalyst bed, the bed was considered to be homogeneous, reducing the temperature to one value. The dynamics of this model were represented by varying the gas hourly space velocities (GHSV). The model was validated with respect to the gas composition with experimental data and could be approximated to the original system with minimal deviations in the single-digit percentage range. The temperatures in the catalyst bed were evaluated qualitatively and have shown comprehensible results. To validate the steady-state temperatures and to account for additional dynamics in the way of varying hydrogen excesses, another model was created in Simulink. The model was empirically approximated to the original system using an unknown model parameter. The validation has shown an approximation of +/- 10 °C for the first and +/- 15 °C for the second reactor, whereas the third reactor depends on many external influences and could not be validated. Furthermore, the temperature profile over time could also be validated with experimental data.