Conversion and leaching characteristics of biomass ashes during outdoor storage – Results of laboratory tests
Section snippets
Introduction and objectives
In recent years, the promotion of energy production from biomass in Austria and the European Union has led to a strong increase in the amount of combustion residues, i.e. ashes. Finding ways to utilize these ashes in an environmentally and economically efficient manner is thus an important goal throughout Europe.
The utilization of the nutrient rich and rather heavy metal poor wood ash fractions (bottom and coarse fly ash) for fertilizing and soil improvement purposes is already implemented in
General
In the laboratory tests four different wood ash fractions from two combustion technologies were stored under different storage conditions (dry/wet, open or in absence of air). The ash fractions investigated were bottom ash as well as a mixture of bottom ash and coarse fly ash from a grate furnace/fixed bed furnace (GF) with a fuel power input of 10 MW, fired with bark and wood chips, boiler fly ash from a bubbling fluidized bed furnace (BFBF) with a fuel power input of 43 MW, fired with wood
Particle size distribution
The particle size distribution of the original untreated ash fractions is shown in Fig. 2.
The particle size distribution of the untreated ash fractions varies significantly between the ashes from a grate furnace and the ashes from the fluidized bed boilers. The ashes from a grate furnace show, apart from the expected higher mass fraction of particles smaller than 400 μm in the mixture of bottom ash and coarse fly ash, a rather similar particle size distribution with still 30% dry mass fraction
Conclusions
The results of the laboratory storage test of different biomass ash fractions show that the main reactions under the conditions given during the laboratory storage test, at least over the first 16 weeks, are the formation of Ca(OH)2 from CaO and water and the attachment of water to amorphous or poorly crystallized phases by hydration or hydroxylation. The overall increase of the TIC mass fraction in the dry material of all ash samples was rather low, so the carbonatation of Ca(OH)2 with CO2 to
Acknowledgments
The authors are grateful to the Austrian Research Promotion Agency (FFG) for funding and the FHP (Association of the Austrian Wood Industries), namely Rainer Handl, for funding and supporting this project.
The authors are grateful to Tanja Gollinger (Bioenergy2020+ GmbH, Austria) and Tereza Rodriguez (MSc. Student, Graz University of Technology, Austria) for the good cooperation and their support regarding the organization and performance of the laboratory tests. The authors are grateful to
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