In the context of resource conservation and the rational production and use of energy, there is growing interest in Switzerland, as elsewhere, in the incineration of domesttic wastes. One of the characteristics of waste incineration cogeneration power plants is their frequent partial or excess loading. In order to describe their behavior at these non-nominal loads, there is a need for simulation tools, which predict with accuracy the behavior of the principal components of the plant at these loads. The paper presents a simulation model of an industrial waste incineration furnace coupled to a natural convection boiler. The model provides information on the internal behavior of the system, which leads to the creation of windows of operation for the incinerator/boiler system. The model was validated using measurements taken at an industrial site and forms the basis of a robust and accurate simulation tool for the description of this kind of system. With this tool, a multitude of different parametric studies can be done on geometery, waste composition, non-nominal loads, combustion gas recirculation, etc. Simulation results are given as well as results from the direct use of this model in evaluating the addition of a topping cycle to an existing waste incineration cogeneration power plant.