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Kemi, Finland

Manskinen K.,Stora Enso | Nurmesniemi H.,Stora Enso | Poykio R.,City of Kemi
Chemical Engineering Journal | Year: 2011

The total heavy metal concentrations in green liquor dregs investigated in this study were clearly lower than the current Finnish statutory limit values for fertilizer used in forestry. This is an advantage if applying for an environmental permit to utilize the green liquor dregs. They contained only carbonate minerals, were strongly alkaline (pH 11.7), and had a neutralizing value of 34.2% (Ca equivalents; d.w.), according to which 1.1 tonnes of green liquor dregs would be required to replace 1 tonne of a commercial ground limestone product produced by SMA Mineral Ltd. These properties support the utilization and re-use of this residue, for instance as a soil conditioning agent. Before such use, it would be necessary to assess the mobility of non-process elements in the dregs. Three-stage sequential extraction procedure development by the European Community Bureau of Reference (BCR) was therefore carried out, in which elements in the residue were fractionated between acid soluble (CH 3COOH; BCR 1), reducible (NH 2OH-HCl; BCR 2) and oxidizable (H 2O 2+CH 3COONH 4; BCR 3) fractions. Except for Co and Ni, the highest extractable concentrations of non-process elements (Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Sb, Se, V and Zn) were in the oxidizable fraction, although certain non-process elements were also extractable and quantitatively detectable in fractions BCR 1 and BRC 2. The results are discussed from various perspectives and in relation to observations in the literature concerning the release of heavy metals and sulphur from the sample matrix under different extraction conditions. © 2010 Elsevier B.V. Source


Poykio R.,City of Kemi | Nurmesniemi H.,Stora Enso
Environmental Engineering and Management Journal | Year: 2010

The bottom ash investigated in this study was sampled from a 32 MW municipal district heating plant incinerating peat (60 %) and clean bark, wood chips and sawdust (40 %) at a bubbling fluidized bed boiler. The bottom ash has high dry matter content (99.7 %), which is a disadvantage, since it can cause dust problems during handling. The highest extractable concentrations of metals in the artificial sweat were for Al (22.0 mg/kg; d.w.), As (2.7 mg/kg; d.w.) and for Ba (12.8 mg/kg; d.w), whereas in the artificial gastric fluid for Al (2210 mg/kg; d.w.), As (12.5 mg/kg; d.w.) and for Ba (91.4 mg/kg; d.w.). Therefore, we conclude that the careful handling of this residue is recommended in order to prevent the penetration of ash particles associated with heavy metals into the human gastrointestinal tract through inadvertent wiping of mouth with dirty hands or through the inhalation of ash particles. Source


According to the XRD spectra, both ashes contained microcline (K(AlSi 3O 8)) and quartz (SiO 2). However, hematite (Fe 2O 3) and dolomite (CaMg(CO 3) 2) only existed in fy ash and bottom ash, respectively. Te total element concentrations were 1.1 (Zn) to 45.1 (S) times higher in fy ash than those in bottom ash. According to three-stage sequential extraction procedure of the European Standards, Measurement and Testing (SM & T) Program (formerly the Community Bureau of Reference (BCR), in which elements in bottom ash and fy ash were fractionated among acid-soluble (CH 3COOH; BCR 1), reducible (NH 2OH-HCl; BCR 2) and oxidizable (H 2O 2 + CH 3COONH 4; BCR 3) fractions, the concentrations of most elements were higher in all fractions of fy ash than those in bottom ash. However, in the BCR 1 fraction, the extractable concentrations of Al, Ba, Be, Cu, Fe, V and Zn, as well as of Fe and Zn in the BCR 3 fraction and Ti in all BRC fractions, were higher in bottom ash than the corresponding heavy metal concentrations in the fy ash. Te results are discussed in relation to observations in the literature concerning heavy metals and sulphur release from a sample matrix under diferent extraction conditions. © 2012 Lietuvos mokslu̧ akademija. Source


Nurmesniemi H.,Stora Enso | Poykio R.,City of Kemi | Watkins G.,Aalto University | Dahl O.,Aalto University
Chemical Speciation and Bioavailability | Year: 2010

The utilization of solid residues allows industry to reduce and recycle waste materials and produce beneficial by-products. The total heavy metal concentrations in slaker grits originating from the chemical recovery process of a pulp mill are lower than the current Finnish statutory limit values for fertilizers used in agriculture and in forestry. In addition, slaker grits are strongly alkaline pH (13.1), have elevated total calcium concentration (331 g kg-1; d.w.), contain calcite (CaCO3), as well as a neutralizing value of 39.4% (Ca equivalents, d.w.). Thus, 0.96 tonnes of slaker grits would be required to replace 1 tonne of a commercial ground limestone product. This indicates that slaker grits have great potential as an industrial residue-based fertilizer and liming agent for use in agriculture and forestry. Since, before such use, it is necessary to assess the mobility of elements in the grits, the three-stage BCR sequential extraction procedure was carried out. Results from sequential extractions showed that the partitioning of Mn (47%), Co (47.1%), Ni (43.1%) and S (94%) was highest in the exchangeable fraction, in which acetic acid (CH3COOH) is used as extractant. The partitioning of Fe (96.5%) and Ti (75.6%) was highest in the easily reduced fraction, in which hydroxylamine hydrochloride (NH2OH-HCl) is used as extractant. The partitioning of Cr (90.8%), V (75.4%), Zn (78.3%), Ba (62.1%), Al (99.4%) and P (99.8%) was highest in the oxidizable fraction, in which hydrogen peroxide (H2O2) is first applied to a heated medium (i.e. 85°C) for dissolving organic matter, after which ammonium acetate (NH4COOH) is used as extractant. Source


Makela M.,Aalto University | Valimaki I.,Suomen Ymparistopalvelu Oy | Poykio R.,City of Kemi | Nurmesniemi H.,Stora Enso | Dahl O.,Aalto University
International Journal of Environmental Science and Technology | Year: 2013

During carbon steel manufacture, slag residues are generated to remove material impurities from liquid metal and thus control the quality of carbon steel. As the utilization of secondary metallurgical slags is not as efficient as those of primary slags, a comprehensive characterization of steel ladle slag was performed. Pseudo-total concentrations of a wide range of elements were determined during a 6-week sampling period with relevant physical and chemical properties, sequential extraction of trace elements, and parallel mineralogical characterization of extraction residues from a representative combined sample. According to the results, only Cr and V occurred in elevated concentrations with respective 6-week mean values of 198 and 310 mg kg-1 (d.w.). The residual standard deviation of the weekly pseudo-total concentration values of the aforementioned elements (24 and 31 %, respectively) indicated that significant variation in the concentration of trace elements can occur due to fluctuation in process conditions and/or slag characteristics. The sequential extraction procedure suggested potential phytoavailability of V (123 mg kg-1, d.w., amounting to 41 % of the respective pseudo-total concentration) through, e.g., changes in prevailing redox conditions. Although the analytical approach was validated by the analysis of a certified reference material and the calculation of extraction recoveries, the mineralogical characterization of parallel extraction residues indicated non-selectivity of the procedure coupled with potential redistribution phenomena during extraction with hydrogen peroxide and ammonium acetate. © 2013 Islamic Azad University (IAU). Source

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