Charakterisierung von Holzasche aus Biomassefernheizwerken

Analyses of ashes from wood chips and bark combustion and research work about possibilities of utilization of these ashes showed that in general a mixture of bottom ash and cyclon fly-ash in the ratio as they occur in the plant can be used as a fertilizer and liming material. An important question is whether mineral impurities (sand, earth, stones) in the biomass are responsible for slagging on the grate (by lowering the melting point) because sintered and slagged ash with a particle size larger than 2 cm has to be sieved or milled before utilized. Furthermore, the influence of these impurities on the homogeneity of wood ash is important for taking and preparing samples for analysis. Usually, the occurring ash fractions in biomass district heating plants can only be volumetrically measured. In order to determine the actual mass flow and to proportion the ash-amounts for fertilization properly, it is necessary to know the bulk densities of the different ash fractions in dependence on the particle size and the biomass used. Moreover, the knowledge of the surface properties of fly-ash particles enables to evaluate the influencing variables on the process of heavy metal deposition from the flue gas to the fly-ash particles. This information represents the basis for a fractionated desublimation/condensation of heavy metals. The aim is to concentrate them in the filter fly-ash, because this smallest and finest ash fraction is cut off from the ash cycle and is disposed of. Conforming to these open questions, ashes from biomass district heating plants were examined. The facts and findings obtained represent the basis for technological measures in order to improve a closed cycle economy with wood ash.     

Zur Funktion der Nasenaufsätze bei Fledermäusen

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