Evaluation of processes for thermal disposal of residual waste according to technical, economic, and ecological criteria has long been a topic of discussion in specialist circles. A basis for such evaluation is provided by material and energy balances determined by operational measurements and supplementary calculation. Thermodynamic process simulation can be regarded as a powerful engineering tool in preparing such balances; its use enhances the objectivity in analysis of various procedures and their comparison with the aid of material, energy, and entropy balances, However, this requires practically relevant calculation models, In this connection, the software used must be able to cope with the states of materials as completely as possible with due attention to technical boundary conditions, Practical knowledge is of decisive importance for the quality of process simulation. In the present work this was permitted by the collaboration of industrial companies arranged by the State Environmental Office of North Rhine-Westphalia.