The advancing digitization that is entering the industry offers, amongst others, the possibility of more efficient and environmentally friendly processes. At the waste incineration plant Simmeringer Haide, two rotary kilns are used for the incineration of hazardous waste. In that specific case the above mentioned possibilities may be used in order to achieve more knowledge about the fuel specification and based on that, an improved combustion control for the fuels can be established. This work shall form the base for that. Prior to forming a mathematical model for describing the process, the incineration process has to be analyzed. On the basis of this stationary model of a mass and energy balance, concrete measures for the improvement of the process are derived and areas of development within the data situation are demonstrated. At the beginning, an introductory literature review describes the construction of modern rotary kilns in waste incineration before a suitable choice is selected from a variety of modeling possibilities. Specifically, the modeling by means of linear systems of equations in conjunction with open source software is determined to be expedient due to flexibility and the possibility of integrating data analysis tools. A solver for weighted least squares optimization with limits for the variables is identified as a suitable solution. After the evaluation of the data situation regarding the process, as a first step in modeling, the process is broken down into several balance areas, on the basis of which a block diagram of the process, containing the most important mass and energy flows, is created. Subsequently, simplifying assumptions are made. After an estimation of the heat losses, besides general conservation equations for mass and energy, further descriptive equations are set up to obtain an overdetermined system of equations. Thereafter, the program code is written, which reads in the data, creates the balance equations and outputs the prepared results. Its functioning is checked applying two different operating states. An essential realization is that a significant part of the fresh air enters the process unregulated as false air. Furthermore, the installation of water content and carbon dioxide measuring in the flue gas is illustrated as an improvement measure. The model is to be supplemented in a follow-up project with dynamic terms and applications derived from them. The model can form the basis for a model-based control, or a digital twin of the process, in order to make the process more environmentally friendly and set the course for a digital future.