Chemical effects of the pretreatment of wood fuels

The aim was to determine the effects of different wood fuels and their drying on the quality of wood pellets and pyrolysis oil. In addition, an aim was to determine emissions from drying and to evolve a dryer model based on the emissions. In another VTT project funded by the Finnish Work Environment Fund and linked with the Tekes project, the quality of wood fuels was studied with regard to occupational health problems. The research was carried out in co-operation with Åbo Akademi University, Swedish University of Agricultural Sciences and Kuopio Regional Institute of Occupational Health. The research included laboratory fixed-bed drying tests, modelling of drying emissions, pelletisation tests with flat die and ring die presses, and co-operation with the Swedish bark project. As raw materials, fresh sawdust, fresh and stored forest chips, and fresh pine and spruce barks, were used. The effects of feedstock, storage, particle size, temperature and final moisture content, on the emissions of drying were determined. The model obtained could be used in the integration of drying in different conversion processes. With forest chips and wood barks, it was possible to get high-quality pellets with the flat die press. The results related to pyrolysis oil were obtained in the VTT pyrolysis projects, funded by Tekes and EU. On the basis of the results, optimization of wood fuels and their pretreatment in regard to the quality of pellets and oils was carried out