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Chemical association and mobility of trace elements in 13 different fuel incineration bottom ashes
Örebro University, School of Science and Technology, Örebro University, Sweden. (MTM)ORCID iD: 0000-0001-5215-5934
Örebro University, School of Science and Technology, Örebro University, Sweden. (MTM)ORCID iD: 0000-0002-2674-4994
2016 (English)In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 172, 105-117 p.Article in journal (Refereed) Published
Abstract [en]

The release of trace elements from waste incineration bottom ash is problematic during utilization/landfilling. Thirteen bottom ashes (from various waste fuels and wooden/mixed wooden fuel) were investigated with respect to the total content, leaching behaviour by standard leaching procedure (EN 12457-3), and chemical association of trace elements by sequential extraction. Results showed that the content of trace elements in household/or industrial waste bottom ashes were of high level in comparison to in wooden/mixed wooden fuel/mixed wooden waste ashes. Type of fuel being treated greatly impacts the total inventory of trace elements. On average, trace element content in 13 ashes followed the decreasing order; Cu > Zn > Pb > Cr > Ni > Sb > As. In this study the average total content of Zn, Pb, Cu and Cr was higher in grate bottom ash treating household/industrial waste in comparison to fluidized boilers ash using same waste, however, there were too few data points and variation in data was large. By Standard leaching procedure, an excessive amount (more than disposal limit) of leached Cr, Pb, Sb and Cu (mostly in household/industrial waste ash) was observed in 6, 5, 5 and 4 of the 13 samples, respectively. Correlation coefficients (r) found between total and water leachable contents for Cu, Sb and As were 0.8, 0.7 and 0.6 respectively. Sequential extraction indicated that residual was the major fraction mostly, however, considerable amounts of trace elements had the potential to leach out. A large fraction of arsenic (57% based on average values) in 5 samples (mostly in waste/virgin wood and mixed wooden waste/fuel) and Zn (49% based on average values) in 4 of 13 samples (mostly household/or industrial) were found in the fractions that are easily available (acid soluble and exchangeable). Further, a considerable amount of Cu in 4 samples were found associated with the organic-bound phase. Dissolved organic matter might play an important role in leaching of Cu during utilization/landfilling. Moreover, principal component analysis (PCA) showed that fuel type affects the association of trace elements in bottom ash. Amounts of labile trace elements in wooden/mixed wooden fuel/waste bottom ashes were comparatively lower than other fuel bottom ashes. None of the samples exceeded the limit of disposal with respect to DOC leaching while chlorine in two and sulphate in three samples (household/industrial) exceeded limit. LOI (550 °C) values were higher for bottom ash from grate facilities probably due to no-pre-treatment of the waste fuel. While comparatively low values of LOI (1 000 °C) in few samples implies that the oxidation might have outweighed the loss of carbonates.

Place, publisher, year, edition, pages
Elsevier, 2016. Vol. 172, 105-117 p.
Keyword [en]
Bottom ash; Speciation; Trace elements; Incineration; Mobility
National Category
Inorganic Chemistry
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-47348DOI: 10.1016/j.fuel.2016.01.010ISI: 000368881200013Scopus ID: 2-s2.0-84954326717OAI: oai:DiVA.org:oru-47348DiVA: diva2:891847
Note

Funding Agency:

Varmeforsk (Thermal Engineering Research Association)

Available from: 2016-01-07 Created: 2016-01-07 Last updated: 2016-04-11Bibliographically approved
In thesis
1. Distribution and chemical association of trace elements in incinerator residues and mining waste from a leaching perspective
Open this publication in new window or tab >>Distribution and chemical association of trace elements in incinerator residues and mining waste from a leaching perspective
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Incineration is a mainstream strategy for solid waste management in Sweden and all over the world. Improved knowledge and understanding about the distribution of trace elements (in ashes) during incineration, and how trace element partitioning respond to the changes in waste composition, are important in terms of combustion process optimization and plant efficiency. Moreover, determination of chemical association of trace elements in ashes are vital for avoiding environmental concerns and to promote possible reuse. In this study, partitioning of trace elements in ashes during incineration as function of input waste fuel and incineration technology was investigated. Further, chemical association of trace elements in resulting ashes was studied. An evaluation was also performed about feasibility of metal extraction from sulfidic mining waste and flotation tailings. Moreover, green liquor dreg (GLD) was tested with respect to stabilization of metals within the sulfidic mining waste.

Findings showed that the total input of trace elements and chlorine affects the partitioning and increasing chlorine in the input waste caused increase in transfer of trace elements to fly ash especially for lead and zinc. Vaporization, condensation on fly ash particles and adsorption mechanisms play an important role for metal distribution. Firing mixed waste, especially biofuel mix, in grate or fluidized (CFB) boilers caused increased transfer into fly ash for almost all trace elements particularly lead and zinc. Possible reasons might be either an increased input concentration of respective element in the waste fuel, or a change in volatilization behavior due to the addition of certain waste fractions. Chemical association study for fly ashes indicated that overall, Cd, Pb, Zn, Cu and Sb are presenting major risk in most of the fly ashes, while in bottom ashes, most of elements are associated with stable fraction. Further, fuel type affects the association of elements in ashes. Chemical leaching of mining waste materials showed that sulfuric acid (under different conditions) is the best reagent to recover zinc and copper from sulfidic mining waste and also copper from flotation tailings. GLD indicates potential for metal stabilization in mining waste by reducing the metal mobility. Extraction methods could be applied to treat mining waste in order to meet the regulatory level at a specific mining site.Similarly stabilization/solidification  methods might be applied after leaching for recovery of metals.

Place, publisher, year, edition, pages
Örebro: Örebro university, 2016. 92 p.
Series
Örebro Studies in Chemistry, ISSN 1651-4270 ; 15
Keyword
trace elements, partitioning, fly ash, bottom ash, speciation, association, risk assessment, wood waste, incineration, mining waste
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-48933 (URN)978-91-7529-128-4 (ISBN)
Public defence
2016-05-03, Hörsalen, Musikhögskolan, Örebro universitet, Fakultetsgatan 1, Örebro, 13:15 (English)
Opponent
Supervisors
Available from: 2016-03-03 Created: 2016-03-03 Last updated: 2016-04-12Bibliographically approved

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