Browsing by Author "Dahl, Olli, Prof., Aalto University, Finland"

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    Assessing potential forest and steel inter-industry residue utilisation by sequential chemical extraction
    (Aalto University, 2012) Mäkelä, Mikko; Heino, Jyrki, Dr., University of Oulu, Finland; Pöykiö, Risto, Dr., City of Kemi, Finland; Nurmesniemi, Hannu, Dr., Stora Enso Oyj, Finland; Puunjalostustekniikan laitos; Department of Forest Products Technology; Kemian tekniikan korkeakoulu; School of Chemical Technology; Dahl, Olli, Prof., Aalto University, Finland
    Traditional process industries in Finland and abroad are facing an emerging waste disposal problem due recent regulatory development which has increased the costs of landfill disposal and difficulty in acquiring new sites. For large manufacturers, such as the forest and ferrous metals industries, symbiotic cooperation of formerly separate industrial sectors could enable the utilisation waste-labeled residues in manufacturing novel residue-derived materials suitable for replacing commercial virgin alternatives. Such efforts would allow transforming the current linear resource use and disposal models to more cyclical ones and thus attain savings in valuable materials and energy resources. The work described in this thesis was aimed at utilising forest and carbon steel industry residues in the experimental manufacture of novel residue-derived materials technically and environmentally suitable for amending agricultural or forest soil properties. Single and sequential chemical extractions were used to compare the pseudo-total concentrations of trace elements in the manufactured amendment samples to relevant Finnish statutory limit values for the use of fertilizer products and to assess respective potential availability under natural conditions. In addition, the quality of analytical work and the suitability of sequential extraction in the analysis of an industrial solid sample were respectively evaluated through the analysis of a certified reference material and by X-ray diffraction of parallel sequential extraction residues. According to the acquired data, the incorporation of both forest and steel industry residues, such as fly ashes, lime wastes, green liquor dregs, sludges and slags, led to amendment liming capacities (34.9-38.3%, Ca equiv., d.w.) comparable to relevant commercial alternatives. Only the first experimental samples showed increased concentrations of pseudo-total cadmium and chromium, of which the latter was specified as the trivalent Cr(III). Based on sequential extraction, dominant cadmium and chromium contents were respectively made available only through aggressive oxidation or dissolution by acid digestion. However, the pseudo-total concentrations of barium and vanadium, of which 17-31% and 12-46% were respectively recovered through desorption/dissolution by the use of acetic acid and moderate reduction by hydroxylamine hydrochloride, suggest the need for further research. The analytical performance during sequential extraction was validated through the analysis of a certified reference material as the analysis of parallel sequential extractions only suggested non-selectivity towards sample periclase coupled with potential redistribution of magnesium and the premature dissolution of sample silicates.
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    Utilisation aspects of ashes and green liquor dregs from an integrated semichemical pulp and board mill
    (Aalto University, 2013) Manskinen, Kati; Nurmesniemi, Hannu, Dr., Stora Enso Oyj, Finland; Pöykiö, Risto, Dr., City of Kemi, Finland; Puunjalostustekniikan laitos; Department of Forest Products Technology; Clean Technologies Research Group; Kemian tekniikan korkeakoulu; School of Chemical Technology; Dahl, Olli, Prof., Aalto University, Finland
    This thesis investigated the properties of bottom and fly ashes originating from a bubbling fluidised bed boiler (120 MW) using two different fuel mixtures (i.e. Fuel mixture A: coal, wood and peat; and B: wood and peat) and of the green liquor dregs originating from the associated semichemical pulp and board mill in relation to the potential utilisation of these residues from various aspects. The total concentrations of As, Cd, Cr, Cu, Ni, Pb, Zn and Hg in the bottom ashes were lower than the maximum allowable concentrations for these elements in forest fertilisers. The total Ca concentrations in bottom ashes A (2.4%; d.w.) and B (3.4%; d.w.) were lower than the legal requirement of 6.0% (d.w.) for ash used as a forest fertiliser. The total Ca concentrations in fly ashes A (6.4%; d.w.) and B (11.0%; d.w.) were higher than the minimum limit value of 6.0% (d.w.), but the concentration of As in fly ashes A (46.9 mg/kg d.w.) and B (41.3 mg/kg; d.w.) exceeded the maximum limit value of 40 mg/kg (d.w.). Only bottom ash B could be used as a forest fertiliser, provided some additional Ca is used. The bottom ashes both fulfilled the Finnish regulations on waste recovery in earth construction. Due to the elevated total concentration of PAH (23 mg/kg; d.w.) and extractable concentrations of Mo (3.9 mg/kg; d.w.) and Se (0.2 mg/kg; d.w.) in fly ash A, this residue cannot be used in covered structures. Due to the elevated concentration of PAH (90 mg/kg; d.w.) in fly ash B, this residue cannot be used in covered and paved structures. However, the utilisation of these residues as an earth construction agent is still possible, but an environmental permit would be required. According to the sequential extraction studies, extractable concentrations of most of the elements in the fly ash A were higher than those in the bottom ash A. The extractability of various elements, both in the bottom and fly ashes A, varied widely. Most of the elements did not occur as readily soluble and mobile forms in these ashes, which supports their utilisation instead of final disposal. The green liquor dregs were strongly alkaline (pH 11.7) and had a high neutralizing capacity (34.2% Ca equivalents; d.w.). These results support the utilisation of this residue e.g. as a soil conditioning agent or pH buffer for acidic soils. The relatively low total concentrations of non-process elements in the green liquor dregs and low partitioning of these elements in the sequential extraction procedure support the re-use of this residue. However, if green liquor dregs are to be utilised, an environmental permit is needed. In terms of human health aspects, the careful handling of fly ash and green liquor dregs is recommended to prevent material dusting problems and the penetration of material particles across the human gastrointestinal tract. In order to promote the utilisation of ashes and green liquor dregs, efforts to develop Finnish legislation on waste utilisation is needed.