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45291.
  • Ögren, Yngve, et al. (författare)
  • Influence of oxidizer injection angle on the entrained flow gasification of torrefied wood powder
  • 2018
  • Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 181, s. 8-17
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, 5 different axisymmetric burners with different directions of the oxidizer inlets were experimentally tested during oxygen blown gasification of torrefied wood powder. The burners were evaluated under two different O2/fuel ratios at a thermal power of 135 kWth, based on the heating value of torrefied wood powder. The evaluation was based on both conventional methods such as gas chromatography measurements and thermocouples and in-situ measurements using Tunable Diode Laser Absorption Spectroscopy. It was shown that changes in the near burner region influence the process efficiency significantly. Changing the injection angle of the oxidizer stream to form a converging oxidizer jet increased process efficiency by 20%. Besides increased process efficiency, it was shown that improvements in burner design also influence carbon conversion and hydrocarbon production. The burner with the best performance also produced less CH4 and achieved the highest carbon conversion. The effect of generating swirl via rotating the oxidizer jet axes was also investigated. Swirl broadened or removed the impingement area between the fuel and oxidizer jets, however resulting in differences in performance within the measurement uncertainty.
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45292.
  • Öhlander, Björn (författare)
  • A molybdenite province in Norrbotten and Västerbotten, northern Sweden
  • 1983
  • Ingår i: Geologiska föreningens i Stockholm förhandlingar. - 0016-786X. ; 105:3, s. 229-234
  • Tidskriftsartikel (refereegranskat)abstract
    • During the period 1967-1980 private prospectors recovered 122 molybdenite mineralized samples from Norrbotten and Vsterbotten, northern Sweden, representing acid igneous rocks of intrusive character, including quartz veins, supracrustal rocks of predominantly acid volcanic origin and skarns. The molybdenite occurrences are generally confined to the Proterozoic continental domain north of the Skellefte district. Fifty-six of the molybdenite samples from different rock types were analysed for major elements and 13 trace elements. Tin is, besides molybdenum, the only element enriched in all rock types. The molybdenite mineralized samples are poor in Nb, not enriched in Rb, and show occasionally high concentrations of F and Cu.
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45293.
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45294.
  • Öhlander, Björn, et al. (författare)
  • Alteration associated with the gold-bearing quartz veins at Middagsberget, northern Sweden
  • 1994
  • Ingår i: Mineralium Deposita. - 0026-4598 .- 1432-1866. ; 29:2, s. 120-127
  • Tidskriftsartikel (refereegranskat)abstract
    • The mesothermal Au deposit at Middagsberget in northern Sweden is associated with irregular stock-works of quartz veins occurring in shear zones across a dioritic intrusion. Alteration in the shear zones is characterized by sericitization, chloritization, the presence of sulphides and several generations of veins and small-scale fractures. Small fractures which are filled with variable amounts of quartz, carbonate, sericite, chlorite, albite and sulphides, are particularly abundant in zones having a high Au content. In general, these fractures are younger than the major quartz veins and were apparently important for strong Au-enrichment. Au is associated with arsenopyrite and it occurs as droplets or interfillings in the arsenopyrite or at the crystal surface; together with pyrrhotite as inclusions in arsenopyrite; as free grains in silicates but close to arsenopyrite; or in very small fractures in carbonates. The Au-mineralization is associated with elevated contents of As, S, Sb and W and depletion of Cu, Zn, Ge and Bi. The entire altered areas are enriched in Au compared with the < 1 to 15 ppb found in the host intrusion. During alteration an initial increase in Na or K was accompanied by a weak enrichment of Au and associated elements together with a depletion of elements such as Ca and Mg. In Au-rich samples this alkali enrichment was overprinted by the carbonate-and sulphide-bearing fractures, which often led to an increased Ca-content. An clear zonation of alteration types has not been found. The host rock has been altered by several generations of fluids: the shear zones were repeatedly ruptured and new small-scale fractures were opened. The different fluids did not, therefore, flow through identical paths although they penetrated the same major zones. This resulted in a complex pattern of variously superimposed alterations.
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45295.
  • Öhlander, Björn, et al. (författare)
  • An attempt to use LA-ICP-SMS to quantify enrichment of trace elements on pyrite surfaces in oxidizing mine tailings
  • 2007
  • Ingår i: Journal of Geochemical Exploration. - 0375-6742 .- 1879-1689. ; 92:1, s. 1-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Metals released from oxidation and weathering of sulphide minerals in mine tailings are to a high degree retained at deeper levels within the tailings themselves. To be able to predict what could happen in the future with these secondarily retained metals, it is important to understand the retention mechanisms. In this study an attempt to use laser ablation high-resolution ICP-MS (LA-ICP-SMS) to quantify enrichment of trace elements on pyrite surfaces in mine tailings was performed. Pyrite grains were collected from a profile through the pyrite-rich tailings at the Kristineberg mine in northern Sweden. At each spot hit by the laser, the surface layer was analyzed in the first shot, and a second shot on the same spot gave the chemical composition of the pyrite immediately below. The crater diameter for a laser shot was known, and by estimating the crater depth and total pyrite surface, the total enrichment on pyrite grains was calculated. Results are presented for As, Cd, Co, Cu, Ni and Zn. The results clearly show that there was an enrichment of As, Cd, Cu and Zn on the pyrite surfaces below the oxidation front in the tailings, but not of Co and Ni. Arsenic was also enriched on the pyrite grains that survived in the oxidized zone. Copper has been enriched on pyrite surfaces in unoxidized tailings in the largest amount, followed by Zn and As. However, only 1.4 to 3.1% of the Cd and Zn released by sulphide oxidation in the oxidized zone have been enriched on the pyrite surfaces in the unoxidized tailings, but for As and Cu corresponding figures are about 64 and 43%, respectively. There were many uncertainties in these calculations, and the results shall not be taken too literally but allowed the conclusion that enrichment on pyrite surfaces is an important process for retention of As and Cu below the oxidation front in pyrite rich tailings. Laser ablation is not a surface analysis technique, but more of a thin layer method, and gives no information on the type of processes resulting in enrichment on the pyrite surfaces. Although only pyrite grains that appeared to be fresh and without surface coatings were used in this study, the possibility that a thin layer of Fe-hydroxides occurred must be considered. Both adsorption to the pyrite directly or to Fe-oxyhydroxides may explain the enrichment of As, Cd, Cu and Zn on the pyrite surfaces, and, in the case of Cu, also the replacement of Fe(II) by Cu(II) in pyrite.
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45296.
  • Öhlander, Björn, et al. (författare)
  • Analyses of trace elements on quartz surfaces in sulfidic mine tailings from Kristineberg (Sweden) a few years after remediation
  • 2003
  • Ingår i: Environmental Geology. - 0943-0105 .- 1432-0495. ; 45:1, s. 98-105
  • Tidskriftsartikel (refereegranskat)abstract
    • Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been applied to determine the elemental composition of the surface layer, as well as of the first interior layer, of quartz grains from the mine tailings from Kristineberg (northern Sweden) in order to determine concentration gradients between these two layers. The quartz grains were collected from the oxidized and unoxidized zones within the tailings. The aim of this study is to assess the role of quartz surfaces as sites for the attenuation of solutes from the mine-tailings porewater. Concentrations of Cu, Ag, Sb, Pb and Bi are highest near the surface of each grain and decrease towards the interior. The surface concentration of Cu, Zn and Pb is more pronounced within the unoxidized than within the oxidized zone of the tailings. Cu exhibits a distinct concentration peak at the surface of the quartz grains below the pre-remediation oxidation front. For Zn and Ce the trend of high surface concentration is less pronounced than for Cu or Pb. Silver, Bi and As are preferably adsorbed within the uppermost layers of the oxidized zone where the pH is as high as 6.2. The conversion of intensity signals of the elements to concentration values in ppm was done by using external standards (NIST silicate glass).
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45297.
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45298.
  •  
45299.
  • Öhlander, Björn, et al. (författare)
  • Biogeochemical mapping of stream plants to trace acid sulphate soils : A comparison between water geochemistry and metal content in macrophytes
  • 2014
  • Ingår i: Geochemistry. - : Geological Society. - 1467-7873 .- 2041-4943. ; 14:1, s. 85-94
  • Tidskriftsartikel (refereegranskat)abstract
    • The efficiency of biogeochemical mapping for identifying acid sulphate soils (AS soils) was studied by sampling and analysing water, transplanted aquatic moss (Fontinalis antipyretica) and leaves of the vascular plant Calamagrostis purpurea at two sites in a stream in northern Sweden with AS soils in its drainage area. One upstream sampling station (Mårtsmarken) was situated in an area dominated by till, and a downstream station (Persraningen) was situated in an area where AS soils are common. Metal contents in F. antipyretica and C. purpurea at these sites were compared to those in water (both unfiltered samples, and samples subjected to 0.22 μm membrane filtration and 1 kDa ultrafiltration to obtain data on metal speciation and its effects on uptake). Oxidation of sulphides with associated increases in acidity and release of metals were clearly reflected by differences in the water samples. At Persraningen the pH was lower than at Mårtsmarken, and the unfiltered concentrations of Al, Ca, Cd, Co, Cu, K, Mg, Mn, Ni, P, S, Sr, Y and Zn were higher. At the upstream station, Mårtsmarken, the suspended fraction was an important carrier of Fe and P, and the colloidal concentrations were higher than or similar to the dissolved concentrations for all determined elements except Na and K. At Persraningen the low pH resulted in changes of speciation, so that the dissolved concentrations were higher than the colloidal concentrations for most elements. For Al, As, Cr, Cu, Pb and Y, the dissolved and colloidal concentrations were similar. For Fe, the colloidal concentration was usually higher than the dissolved concentration, and suspended Fe was detected. Aluminium, Cr, Cu, Fe and Y concentrations were significantly higher in Fontinalis antipyretica at Persraningen than at Mårtsmarken. In addition, concentrations of Al and Fe in C. purpurea were significantly higher at Persraningen. Our results highlight the potential of biogeochemical mapping for predicting the occurrence of AS soils. A limitation is the strong pH dependence of the uptake of metals in the aquatic mosses resulting in that only a few of the elements typically occurring at high concentrations in waters draining AS soils are enriched in the macrophytes. A combination of maps showing both absolute concentrations and elemental ratios would be useful for this, including not only ratios of previously suggested utility (e.g. Y:Pb and Ni:Pb), but also others, such as Y:Ca, Al:Ca, Cu:Ca, Y:Mg, Al:Mg and Cu:Mg. © 2014 AAG/The Geological Society of London.
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45300.
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