Waste as fuel in thermal waste treatment is characterised by a heterogeneous and fluctuating composition. In addition to familiar fractions such as paper, plastics and textiles, new fractions are appearing. Materials such as composites and insulating materials, carbon fibre-reinforced plastics and electrical waste have problematic properties from an incineration point of view. If the composition of the fuel mixture is available, however, these can be counteracted.

For the inline determination of the waste composition a calculation method consisting of two sequential models was developed. First, the extended online balancing allows to calculate the elementary waste composition (C, H, O), the water and ash content, lower calorific value and mass flow of the waste. Afterwards these results can be used in the so-called numerical fraction model to determine the fractional composition.

Theoretical validation has already proven that the model delivers reliable results in wide areas. First results of the experimental validation of the models are presented in this paper. For the investigations, synthetic fuel mixtures were produced from several mono-fractions and burnt on the backward acting grate of a grate firing pilot plant. The recorded measurement data, such as the flue gas composition and the volumetric flows of flue gas and supply air, is used as input data for the models. For validation, a comparison with the composition known from fuel analyses was made.