FWF - Heizwert und Sauerstoff - Calorific value and oxygen demand of volatiles incl. tars

The exploitation of biogenic fuels for thermal utilisation gains more and more importance. Furthermore waste products (e.g. plastics) are often converted thermally to dispose them on the one hand and to exploit them energetically as well, not only because of the statutory order for landfills in Austria. Hence it is of major interest to optimize installations for the thermal use of solid fuels in order to reduce emissions. On the one hand a high energy production and on the other hand an improved environmental situation by reducing the emissions can be achieved. Whereas the knowledge of the area of the released heat and the oxygen demand dependant on pyrolysis progress - resp. area - matters. The pyrolysis plays a key role at any thermal conversion of solid fuels. Especially for biomass as biomass bears a high share of volatiles (e.g. spruce wood: 85 % volatiles, thereof about 70 % tars), which are released during pyrilysis and hence extremely influence the combustion process. As the calorific value of volatiles (including tars) and their oxygen demand dependant on time are of interest for combustion and gasification processes, these parameters should be investigated in more detail. In former projects the influence of particle size and moisture content on the share of volatiles, released during pyrolysis, had been investigated. In practice especially tars cause problems and should be investigated more precisely. To investigate tars by using composition analysis methods is very work intensive and expensive as well because of the complexity of their chemical structure. The newly designed test facility, which will be used in the proposed project, is a combination of a thermo gravimetric scale and a differential scanning calorimeter and allows to investigate the calorific value and the oxygen demand of tars and volatiles without investigating their elementary structure. Hence a simple, fast and cheep possibility to investigate experimentally the calorific value of tars and volatiles dependant on time - resp. turnover -will be generated which also allows conclusions on crack reactions. By additional experiments with a bomb calorimeter the calorific value of pyrolysis cokes at different times of turnover will be investigated. Additionally various plastics and plastic mixtures will be investigated on the calorific value of volatiles and tars. It can be assumed that mixtures of different plastics do not behave additive. These investigation results are of major interest for designing combustion units and to be able to simulate these units. Furthermore the results are of great importance for simulation validations.