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Reactivity and Leaching of Wood Ash Pellets Dehydrated by Hot Air and Flue Gas
University of Kalmar, School of Pure and Applied Natural Sciences.
University of Kalmar, School of Pure and Applied Natural Sciences.
University of Kalmar, School of Pure and Applied Natural Sciences.
University of Kalmar, School of Pure and Applied Natural Sciences.
2009 (English)In: The Open Waste Management Journal, ISSN 1876-4002, E-ISSN 1876-4002, Vol. 2, no 8, p. 47-54Article in journal (Refereed) Published
Abstract [en]

Companies that generate a large amount of wood ash will need an industrial process to agglomerate the ash and lower its reactivity, because untreated ash is a dust hazard for workers and is difficult to spread evenly on forest soil. In addition, untreated ash can cause burning damage to vegetation owing to its alkalinity and rapid release of salts. Production of large amounts of wood ash agglomerates demands an effective dehydration process. The reactivity and release of inorganic constituents from wood ash pellets dehydrated at room temperature using hot air and flue gas was investigated. Our results imply that flue gas-treated pellets have significantly lower reactivity in terms of pH and electrical conductivity, and release less Ca2+ and more Mg2+ compared to pellets dried at room temperature or in hot air. Ash pellets dehydrated in hot air are very reactive, and release more Ca2+ than pellets dried in other ways. The formation of syngenite during the flue-gas treatment decreases K+ release from the ash pellets.

 

 

 

 

Place, publisher, year, edition, pages
2009. Vol. 2, no 8, p. 47-54
Keyword [en]
Wood ash, Ash pellet, Leaching, Dehydration, Carbonation, Reactivity
National Category
Environmental Sciences
Research subject
Natural Science, Environmental Science
Identifiers
URN: urn:nbn:se:hik:diva-614DOI: 10.2174/1876400200902010047OAI: oai:DiVA.org:hik-614DiVA, id: diva2:1863
Available from: 2007-10-08 Created: 2009-09-16 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Ash Products for Nutrient Recycling in Forestry: Leaching and Drying Characteristics
Open this publication in new window or tab >>Ash Products for Nutrient Recycling in Forestry: Leaching and Drying Characteristics
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

As the demand for carbon dioxide neutral energy sources increases, forestry becomes more intensive. Entire trees are removed from the felling sites threatening the nutrient balance of the forest soils. By recycling wood ash produced from the combustion of clean wood biofuels back to the forest, it is possible to maintain the nutrient balance of the soil and also to counteract its acidification. To avoid negative effects, e.g. burn damage on mosses and lichens caused by the high pH of the ash, it is important that the ash is treated and hardened in order to lower its reactivity and to prolong its dissolution rate. The ash chemicals content are determind and the reactivity and dissolution properties are evaluated by laboratory leaching tests. Pulp and paper industries generate not only ash but green liquor sludge also as residual material. These nutrient-rich materials could be put together into granules and be recycled on forest soil. The applied leaching tests vary in their performance and duration. Therefore the focus of this work is put on both making granules of ash and green liquor sludge and developing a method for the testing of these.

The aims of this thesis are: to investigate how leaching tests influences the dissolution of ash products; to find out how drying techniques affect the product's leaching behaviour and to find an appropriate technique for mixing and agglomerating wood ash and green liquor sludge in suitable proportions.

The leaching tests compared were: up-flow percolation, batch leaching and leaching using a magnetic stirrer. This study includes analyses of pH and concentrations of Na, Ca, K, Mg, Mn, Al, Cu, Fe, P and Zn in the eluate from each leaching test. The results show that the batch leaching test at L/S 10 has the ability to dissolve 70-90 % of K and Na from the ash products. The upflow percolation test releases 55-100 % K and Na, but takes several weeks to perform. The leaching test with a magnetic stirrer results in low leached amounts of elements and underestimation of the dissolution potential of the material. The test seems to be best suited for its original purpose, i.e. control of the reactivity of wood ash.

Four drying techniques were applied on wood ash pellets: drying at room temperature, drying by hot air (60 and 130 C) and drying by flue gas. The ash pellets dried in flue gas showed the significantly lowest values of pH and electric conductivity. This makes flue gas drying an advantageous method, for ash products intended for spreading in forest. Regarding the elements studied, the flue gas drying does not contaminate the ash material.

Processing the ash and green liquor sludge using an intensive mixer offers effective blending and a quick granulation with a short process line. With the intensive mixer it is possible to granulate a mixture of maximum 65 % sludge (wet weight basis) and 35 % ash (dry weight basis).

Series
Dissertation series / University of Kalmar, Faculty of Natural Science, ISSN 1650-2779
Keyword
Ash products, Wood ash, Leaching, Drying, Nutrient;, Sustainable forestry
National Category
Forest Science
Research subject
Natural Science, Environmental Science
Identifiers
urn:nbn:se:hik:diva-25 (URN)978-91-89584-77-8 (ISBN)
Presentation
2007-08-22, A137, Landgången 4, Kalmar, 10:00 (English)
Opponent
Supervisors
Available from: 2007-10-08 Created: 2007-10-08 Last updated: 2010-03-09

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Sarenbo, SirkkuStålnacke, OlofClaesson, Tommy

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