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  • 1.
    Andersson, Emil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Online Metallurgical Mass Balance and Reconciliation2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In mineral processing, one of the most important and versatile separation methods is flotation. Flotation utilizes the different surface properties of the valuable minerals in the ore to separate them from the less valuable gangue material in the ore. Crushed and ground ore is mixed with water and fed into flotation tanks. In the flotation tanks, the particles of valuable mineral are made hydrophobic. That way, they can be floated by attaching to air bubbles and gather on top of the flotation tank as froth. This froth, containing higher concentrations of valuable mineral, is recovered and then processed further.

    The flotation circuit is controlled and maintained using measurements on the mass flows and grades of different materials. Due to economical, practical, and technological limitations, these measurements are performed at a chosen number of points in the circuit and at discrete points in time. Poor measurement data can have devastating consequences if the operators are left with limited information and errors in the circuit remain undetected.

    The accuracy of the acquired measurements is improved by performing mass balance and reconciliation. Traditionally, mass balance uses the sum of the total mass flows and the average grades over long times to avoid including the internal mass of the circuit in the calculations. It is desirable to perform mass balance directly to allow for faster intervention if any failures occur in the circuit during the on-line process.

    This report describes an on-line dynamic approach towards mass balancing and reconciliation of the mass flows and grades in a flotation circuit. Here, physical models of the flotation circuit are used to construct mass balance constraints using interpolation and test functions and the mass balance problem is posed as an optimization problem. The optimization problem is to adjust the assay such that the residual, the difference between the measured and the adjusted assay, is minimized while maintaining mass balance.

    An implementation in MATLAB and tests on synthetic data show that the dynamic formulation of mass balance does adjust 'erroneous' measurements such that mass balance is fulfilled. Given this result, there are still important aspects of the implementation that have to be addressed. The model uses the unknown and cell specific parameters flotation rate and recovery. Thus, these must be found or properly modeled. This report proposes a possible model for flotation rate as well as a strategy to find the recovery. The requirements of accuracy and speed of the implementation are also discussed.

    Possible next steps of this project is to further confirm a time effective implementation using synthetic data. Consequently, the implementation can be adapted for natural data in order to verify correctness of models.

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  • 2.
    Bhatti, Tariq M.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Bioleaching of organic carbon rich polymetallic black shale2015In: Hydrometallurgy, ISSN 0304-386X, E-ISSN 1879-1158, Vol. 157, p. 246-255Article in journal (Refereed)
    Abstract [en]

    The present study describes the extraction of metals from organic-carbon rich Kyrk Tasjo (Sweden) polymetallic black shale using mixed cultures of acidophilic iron- and sulfur-oxidizing microorganisms. Quartz, Mite, micro-cline, calcite, dolomite and pyrite minerals were present in shale matrix. Black shale contained 10.77% organic carbon as kerogen and 1.16% inorganic carbon (graphite). The leaching experiments were performed in shake flasks and stirred tank reactors with and without acidophilic Fe- and S-oxidizing psychrotolerant, mesophile and moderate thermophile strains at 6,30 and 45 degrees C. Biological oxidation of pyrite generated sulfuric acid and ferric sulfate in leach solutions during leaching process. Microbial leaching solubilized 80-90% of the total metals (U, Cu, Ni, Mn, Mo, Y and Zn) after 15-20 days of bioleaching at 30 and 45 degrees C; whereas metal solubilization was slower with acidophilic psychrotolerant bacteria at 6 degrees C. The biodegradation of kerogen released tetradecane (CH3(CH2)(12)CH3), a long-chain aliphatic hydrocarbon compound and several other un-identified hydrocarbons in leach solutions during bioleaching of black shale. The addition of PO43- and NH4+ in the growth medium during bioleaching had no effect or decreased the metal solubilization, suggesting that the microorganisms obtained these nutrients from the minerals and kerogen (C100H112O9N2S5), a nitrogenous hydrocarbon compound present in the shale matrix. Metal dissolution from black shale was mainly attributed to the acid concentration in leach solution and temperature. The leaching data demonstrate the feasibility of extracting metals from the black shale without additional nutrient supply that constitute a cost saving for commercial scale application of bioleaching process. The bioleaching approach does not appear warranted to view of the low concentrations, albeit relatively high recoveries of valuable metals from the black shale. The leaching data indicate that exposed black shale occurrences, being subject to ambient weather conditions, constitute a long term environmental challenge.

  • 3.
    Buckland, Philip I.
    et al.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Hammarlund, Dan
    Lund University.
    Hjärthner-Holdar, Eva
    Swedish National Historical Museums.
    Lidén, Kerstin
    Stockholm University.
    Lindahl, Anders
    Lund University.
    Palm, Fredrik
    Umeå University, Faculty of Arts, Humlab.
    Possnert, Göran
    Uppsala University.
    The Strategic Environmental Archaeology Database: a resource for international, multiproxy and transdisciplinary studies of environmental and climatic change2015Conference paper (Refereed)
    Abstract [en]

    Climate and environmental change are global challenges which require global data and infrastructure to investigate. These challenges also require a multi-proxy approach, integrating evidence from Quaternary science and archaeology with information from studies on modern ecology and physical processes among other disciplines. The Strategic Environmental Archaeology Database (SEAD http://www.sead.se) is a Swedish based international research e-infrastructure for storing, managing, analysing and disseminating palaeoenvironmental data from an almost unlimited number of analysis methods. The system currently makes available raw data from over 1500 sites (>5300 datasets) and the analysis of Quaternary fossil insects, plant macrofossils, pollen, geochemistry and sediment physical properties, dendrochronology and wood anatomy, ceramic geochemistry and bones, along with numerous dating methods. This capacity will be expanded in the near future to include isotopes, multi-spectral and archaeo-metalurgical data. SEAD also includes expandable climate and environment calibration datasets, a complete bibliography and extensive metadata and services for linking these data to other resources. All data is available as Open Access through http://qsead.sead.se and downloadable software.

     

    SEAD is maintained and managed at the Environmental Archaeology Lab and HUMlab at Umea University, Sweden. Development and data ingestion is progressing in cooperation with The Laboratory for Ceramic Research and the National Laboratory for Wood Anatomy and Dendrochronology at Lund University, Sweden, the Archaeological Research Laboratory, Stockholm University, the Geoarchaeological Laboratory, Swedish National Historical Museums Agency and several international partners and research projects. Current plans include expanding its capacity to serve as a data source for any system and integration with the Swedish National Heritage Board's information systems.

     

    SEAD is partnered with the Neotoma palaeoecology database (http://www.neotomadb.org) and a new initiative for building cyberinfrastructure for transdisciplinary research and visualization of the long-term human ecodynamics of the North Atlantic funded by the National Science Foundation (NSF).

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  • 4.
    Carlborg, Markus
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Weiland, Fredrik
    Ma, Charlie
    Luleå University of Technology, Luleå, Sweden.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Landälv, Ingvar
    Wiinikka, Henrik
    Exposure of refractory materials during high-temperature gasification of a woody biomass and peat mixture2018In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, no 2, p. 777-787Article in journal (Refereed)
    Abstract [en]

    Finding resilient refractory materials for slagging gasification systems have the potential to reduce costs and improve the overall plant availability by extending the service life. In this study, different refractory materials were evaluated under slagging gasification conditions. Refractory probes were continuously exposed for up to 27 h in an atmospheric, oxygen blown, entrained flow gasifier fired with a mixture of bark and peat powder. Slag infiltration depth and microstructure were studied using SEM EDS. Crystalline phases were identified with powder XRD. Increased levels of Al, originating from refractory materials, were seen in all slags. The fused cast materials were least affected, even though dissolution and slag penetration could still be observed. Thermodynamic equilibrium calculations were done for mixtures of refractory and slag, from which phase assemblages were predicted and viscosities for the liquid parts were estimated.

  • 5.
    Dopson, Mark
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kupka, Daniel
    Halinen, Anna-Kaisa
    Rahunen, Nelli
    Özkaya, Bestamin
    Sahinkaya, Erkan
    Rzhepishevska, Olena I
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Kaksonen, Anna H
    Karnachuk, Olia V
    Tuovinen, IH
    Puhakka, Jaakko A
    Iron oxidation and bioleaching potential at low temperatures2007In: Biohydrometallurgy: from the single cell to the environment / [ed] Axel Schippers, Zurich: Trans Tech Publications Inc., 2007, p. 578-578Conference paper (Refereed)
  • 6. Grivel, J-C
    et al.
    Pitillas, A.
    Namazkar, S.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde, Denmark.
    Alexiou, A.
    Holte, O. J.
    Preparation and characterization of MgB2 with Pd, Pt and Re doping2016In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 520, p. 37-41Article in journal (Refereed)
    Abstract [en]

    Samples with Mg1-xDxB2.04 (D = Pt, Pd or Re) nominal compositions have been synthesised by a solid-state route. None of these doping elements can be substituted for Mg in a detectable amount and their presence in the samples has no influence on the critical temperature and on the lattice parameters of the MgB2 superconductor. Impurity phases are formed by reaction mostly with Mg. The microstructure of the Pt, Pd and Re-based phases depends on the elements. Re-rich particles with large sizes up to 8 mu m form, whereas Pt- and Pd-containing impurities are finely dispersed with a particle size that does not exceed 1 mu m. The field dependence of the normalised critical current density is improved when Pt, Pd or Re are present in the samples. (C) 2015 Elsevier B.V. All rights reserved.

  • 7.
    Hagman, Henrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lundberg, Mats
    Boström, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Alloy Selection for a Cofired Circulating Fluidized Bed Boiler Vortex Finder Application at 880 degrees C in a Complex Mixed Mode Corrosion Environment2017In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 31, no 11, p. 12857-12866Article in journal (Refereed)
    Abstract [en]

    X-ray diffraction and scanning electron microscopy (SEM) were used on a corroded industrial-scale circulating fluidized bed (CFB) boiler vortex finder (VF) 253MA alloy plate material to identify the dominating corrosion products and to enable a qualified selection of candidate alloys for the long-term, full-scale exposure study. Alloys 253MA, 310S, 800H/HT, Alloy DS, and Alloy 600 were chosen, and the alloy plates were exposed to the CFB boiler combustion atmosphere having an average temperature of approximately 880 degrees C, consisting of a moist globally oxidizing gas, burning hydrocarbons, CO2, CO, SO2, HCl, NH3, N-2, alkali species, and erosive particles. The exposure times used in this study were 1750, 8000, 12000, and 16000 operating hours. After exposure, the alloy samples were cut, and cross-sections were dry-polished and analyzed with an SEM-backscatter electron detector (BSD) setup to quantify material loss and penetration depth of the corrosion attack. This work suggests two novel concepts: heavily affected depth (HAD) enabling quantitative evaluation of heavily degraded alloys and remaining serviceable metal thickness (RSMT) enabling the use of long-term corrosion data from one alloy to make rough service life estimations of other alloys exposed for significantly shorter periods. The findings of this work show that there is no simple correlation between the heavily affected depth of the alloy and the nickel, chromium, or iron content. Instead, there seem to be two successful alloy composition principles that work well for this application. Furthermore, the work shows that major improvements can be made in terms of both technical life-span and the cost-effectiveness of the VF application if the most appropriate alloy is selected. In this study, a replacement of the frequently used Alloy 253MA with Alloy 310S doubled the lifespan of full-scale VFs, reducing the average VF maintenance cost to half.

  • 8.
    Hermassi, Mehrez
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Chemical Engineering Department, East Barcelona Engineering School, Barcelona TECHUPC, (Campus Diagonal-Besos), Sant Adria de Besos, Spain.
    Granados, M.
    Valderrama, C.
    Ayora, C.
    Cortina, J. L.
    Recovery of Rare Earth Elements from acidic mine waters by integration of a selective chelating ion-exchanger and a solvent impregnated resin2021In: Journal of Environmental Chemical Engineering, E-ISSN 2213-3437, Vol. 9, no 5, article id 105906Article in journal (Refereed)
    Abstract [en]

    A polymeric ion-exchange resin, incorporating methyl-amino-phosphonic (TP260) functionalities, and a solvent impregnated resin (SIR) incorporating tri-methylpentylphosphinic acid (TP272), were evaluated for the selective separation of Rare Earth Elements (REE) from Transition (TE), post -Transition (PTE), and Alkaline Earth (AE) Elements in acidic mine waters (AMW). The influence of the functional groups nature and the acidity dependence were studied and their effects on efficiencies for REE removal and separation from TE/PTE were analysed Both resins provided good separation factors of REE from TE/PTE by acidity control of the treated effluent once Fe (III), the major component in AMW, had been removed by precipitation. The TP272 resin, containing trimethylpentylphosphinic acid (Cyanex 272) onto the polymeric network, showed higher affinity towards Heavy REE (HRRE) than for Light REE (LRRE) by acidity control (pH > 4). Higher pre-concentration factors were achieved for TP272 impregnated resin (e.g., 20-30) in comparison with the TP260 phosphonic resin (2-5), as the pH extraction window is in the moderate pH region (1-5). The integration in series of both resins could be used to separate and recover HREE and LREE from TE/PTE from AMW generated concentrates could be used to recover REE as secondary resources for the clean energy technology industry.

  • 9.
    Johari, G.P.
    et al.
    Department of Materials Science and Engineering, McMaster University, Hamilton, Canada.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Effects of pressure-temperature protocols on the properties of crystals and ageing effects: an analogy with glasses2022In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 102, no 4, p. 299-320Article in journal (Refereed)
    Abstract [en]

    Properties of a crystal are used to determine the point defects concentration, n, the self diffusion coefficient, D and variation of n and D with tempertaure, T. Also, spontaneous change in the properties of a crystal’s non-equilibrium state is used to determine the decrease in n with time. Both n and D decrease with increase in the pressure, P, until the pressurising-rate dependent, kinetic-freezing pressure for defects disorder, PD-F, is reached. At P > PD-F, a crystal is in a non-equilibrium state. We consider such configurationally-frozen states of a crystal produced by using three unusual P-T protocols: (i) pressurising a crystal to P > PD-F, cooling to a low T and depressurising, (ii) pressurising to P < PD-F, cooling through the defects freezing temperature, TD-F, and depressurising, and (iii) cooling a crystal at 1 bar to T <TD-F pressurising and maintaining at high P. The non-equilibrium state of the crystal would have defect concentration that kinetically froze at P = PD-F or T = TD-F, but its volume and phonon properties would not correspond to the kinetically-frozen state at P = PD-F or at T = TD-F. On aging, their properties would change differently than those of a non-equilibrium state of a crystal produced by quenching at a fixed P. We relate n, D and the electrical resistivity to thermal conductivity, κ, by the Wiedemann-Franz equation, and discuss how κ would change on aging of a crystal. The above-given effects alter the properties of metallic and non-metallic, metastable materials during their commercial use.

  • 10.
    Leander, D
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Östberg, A
    Potentiostatic methods in sample preparation and etching2004In: Praktische metallographie, ISSN 0032-678X, E-ISSN 2195-8599, Vol. 41, no 11, p. 561-576Article in journal (Refereed)
    Abstract [en]

    A potentiostat was used in order to optimise etching and phase extraction. Polarisation curves for different grades of steel and different electrolytes were collected and the results were used for optimisation of the voltage and time with multivariate methods. In electrolytic etching a potential is set to control the etching reaction. With the help of a potentiostat the potential is maintained at the set value and the process is well defined and reproducible. Etching procedures were tried out to differentiate between various intermetallic phases that were indistinguishable using other etching methods and the results were evaluated with light and X-ray diffraction methods. Settings for rapid phase extraction of duplex stainless steels in 10% HCl in ethanol were found from the Potentio dynamic scan (PDS), without dissolving the desired phase. An investigation of the influence of the illumination of the sample in image processing was also performed.

  • 11. Lindberg, Daniel
    et al.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Hupa, Mikko
    Thermodynamic modeling of the stability and melting properties of sodium borates relevant to black liquor combustion and gasification2007In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 98, no 10, p. 1012-1018Article in journal (Refereed)
    Abstract [en]

    The use of borates as an autocausticizing agent in kraft recovery boilers of pulp mills is an interesting concept for decreasing the lime consumption at pulp mills. The main autocausticizing reaction is between NaBO2 and Na2CO3 forming Na3BO3 and CO2 at high temperatures in a liquid phase in the recovery boiler. The thermodynamic and phase equilibrium data of the Na2CO3-NaBO2-Na3BO3 system were evaluated and optimized. The liquid phase was modeled with the modified quasichemical model. The thermodynamic database obtained can be used to calculate the phase equilibrium and thermodynamic properties of multicomponent sodium salt mixtures of importance for the borate autocausticizing concept. The thermodynamic database is a part of an extensive thermodynamic database for alkali salt mixtures of importance for black liquor combustion in the pulp and paper industry.

  • 12.
    Ma, Charlie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Carlborg, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Structures and diffusion motions of K and Ca in biomass ash slags from molecular dynamics simulations2021In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 302, article id 121072Article in journal (Refereed)
    Abstract [en]

    The ash slag formations that can occur in combustion and gasification of solid fuels often consist of silicate melts that can cause operational problems, e.g., bed agglomeration or slag build-up. This study aims to better understand the underlying molecular structures and motions that bring about viscosity variations in biomass ash slags that are rich in Ca and K. Aspects of slag structure, diffusivity, and cation motion in the molten CaO–K2O–SiO2 system were acquired from molecular dynamics simulations. These results are discussed in relation to viscosity values found in literature. Among the structural characteristics of the silicate network, the simulations showed that the local structures of both Ca and K were affected by composition, with stronger integration of Ca within the silicate network than K. The formation of larger ring structures due to network depolymerisation occurred with increasing diffusivity and lower viscosity, but small rings prevailed due to clusters of Si and O atoms that formed cohesive structures. Both Ca and K showed hopping motions as they diffused through the network, especially in high viscosity compositions. These cations exhibited preferential migration to positions previously occupied by the same species, as a means of moving around the network-forming Si and O atoms that diffused slower. The diffusivity of K ions was facilitated by transport in percolation channels. The presence of slower-diffusing Ca ions occupied positions that could otherwise have contributed to K diffusivity. This work contributes towards understanding of ash slags in thermochemical processes by exploring network modifier mobility in silicate slags.

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  • 13.
    Ma, Charlie
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Carlborg, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Viscosity of molten CaO-K2O-SiO2 woody biomass ash slags in relation to structural characteristics from molecular dynamics simulation2020In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 215, article id 115464Article in journal (Refereed)
    Abstract [en]

    Molten compositions in the CaO-K2O-SiO2 system relevant to woody biomass ash slags were simulated with molecular dynamics to extract structural characteristics. Multivariate analysis elucidated correlations of these structural characteristics with viscosity measurements. The simulations show SiO4/silicate tetrahedral units (STUB) diffusing slowly and forming flexible networks via oxygen bridges. The degree of STU polymerization varies linearly with the (K2O + CaO)/SiO2 ratio. Ca depolymerises stronger than K, but K diffuses quicker. Depolymerization and diffusion cause network disruptions and agitations that promote collective atomic mobility of the system. This imposes structural characteristics in the slag that correlate with viscosity. The inter-STU Si-O-Si angle narrows with decreasing viscosity, while the Si-O bond length of these bridges increases. Attributes related to atomic mobility, such as the variations in the Si-O-Si angle and the distance of nearest Si-Si pairs, also correlate with viscosity. The discussion provides insight into the connection between structural characteristics and viscosity.

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  • 14. Mikhlin, Yuri
    et al.
    Karacharov, Anton
    Tomashevich, Yevgeny
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Interaction of sphalerite with potassium n-butyl xanthate and copper sulfate solutions studied by XPS of fast-frozen samples and zeta-potential measurement2016In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 125, p. 98-105Article in journal (Refereed)
    Abstract [en]

    We acquired low-temperature X-ray photoelectron spectra of fast-frozen wet pastes prepared by centrifugation of the natural sphalerite slurries containing potassium n-butyl xanthate (KBX), without washing or any additional treatment, before and after the mineral activation in 0.1 mM CuSO4 solution. Zeta potentials of the slurry particles were also measured. The method allowed characterizing the mineral surfaces and adsorbates, volatile substances and hydrated species within the interfacial layers under more realistic flotation-related conditions. The uptake of xanthate by unactivated mineral was low even in 10 mM KBX, while the surface became metal-deficient (enriched in sulfur), more hydrophobic and contaminated with carbonaceous matter. Dibutyl dixanthogen was the major interfacial product of the interaction of Cu-activated sphalerite having the surface atomic Zn/Cu ratio of 3 and excess of sulfur with the KBX solutions. The spectra revealed only minor quantities of Zn and Cu xanthates and oxyhydroxides at all the samples; some hydrated K+ counter-ions were detected at the negatively charged surfaces after the xanthate treatment. The dixanthogen was concluded to form via oxidation of xanthate at the interface, probably catalyzed by surface cuprous species but not direct interaction with cupric ions.

  • 15. Salmi, Tapio
    et al.
    Eränen, Kari
    Tolvanen, Pasi
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Åbo Akademi University, Johan Gadolin Process Chemistry Centre (PCC), Laboratory of Industrial Chemistry and Reaction Engineering, Turku/Åbo, Finland.
    Russo, Vincenzo
    Determination of kinetics and equilibria of heterogeneously catalyzed gas-phase reactions in gradientless autoclave reactors by using the total pressure method: Methanol synthesis2020In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 215, article id 115393Article in journal (Refereed)
    Abstract [en]

    Rapid methods are very valuable in the determination of the kinetic and mass transfer effects for heterogeneously catalyzed reactions. The total pressure method is a classical tool in the measurement of the kinetics of gas-phase reactions, but it can be successfully applied to the kinetic measurements of gas-phase processes enhanced by solid catalysts. A general theory for the analysis of heterogeneously catalyzed gas-phase kinetics in gradientless batch reactors was presented for the case of intrinsic kinetic control and combined kinetic-diffusion control in porous catalysts. The concept was applied to gas-phase synthesis of methanol from carbon monoxide and hydrogen on a commercial copper-based catalyst (CuO/ZnO/Al2O3 R3-12 BASF). The reaction temperature was 180–210 °C and the initial total pressure was varied between 11 and 21 bar in a laboratory-scale autoclave reactor equipped with a rotating basket for the catalyst particles. The initial molar ratios CO-to-H2 were approximately 1:2, 1:3 and 1:4. The experimental data from methanol synthesis were compared with numerical simulations and a good agreement between the experiments and model simulations was achieved. The predicted equilibrium agrees with previously reported values.

  • 16. Sar, Suchandra
    et al.
    Öqvist, Lena Sundqvist
    Sparrman, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Engström, Fredrik
    Samuelsson, Caisa
    Characterization of Double Leached Waelz Oxide for Identification of Fluoride Mineral2019In: Metals, ISSN 2075-4701, Vol. 9, no 3, article id 361Article in journal (Refereed)
    Abstract [en]

    Double leached Waelz oxide (DLWO), with 76% zinc, is a secondary zinc containing raw materials obtained by the treatment of electric arc furnace dust. The content of fluoride in DLWO is still too high for direct leaching, as fluoride has a detrimental effect on electrowinning for zinc production. Knowledge of the characteristics of DLWO, and especially on how a fluoride mineral might exist, can contribute to further improvement of the selective leaching for the removal of fluoride. In this study, DLWO was characterized using analytical techniques, such as inductively coupled plasma-optical emission spectroscopy (ICP-OES), F-19 liquid-state nuclear magnetic resonance (F-19 LS NMR), X-ray powder diffraction analysis (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and F-19 solid-state nuclear magnetic resonance (F-19 SS NMR). This study showed that DLWO mainly consisted of zincite (ZnO), cerussite (PbCO3) and a spinel containing zinc, iron and manganese. The fluoride mineral identified was calcium fluoride (CaF2). In SEM analysis, fluorine was found in larger grains together with calcium and oxygen, which was possibly calcium carbonate.

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  • 17.
    Sarmad, Shokat
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. 2 Industrial Chemistry & Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Vapor-liquid equilibrium of ionic liquids2020In: Encyclopedia of ionic liquids / [ed] Suojiang Zhang, Singapore: Springer, 2020, p. 1-22Chapter in book (Other academic)
  • 18.
    Sarmad, Shokat
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Nikjoo, Dariush
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Industrial Chemistry & Reaction Engineering, John Gadolin Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, Fl-20500 Åbo-Turku, Finland.
    Amine functionalized deep eutectic solvent for CO2 capture: Measurements and modeling2020In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 309, article id 113159Article in journal (Refereed)
    Abstract [en]

    Deep eutectic solvents (DESs) have gained a great interest among researchers owing to their inherent advantages to become an adaptable alternative to ionic liquids (ILs) and common amine solutions for CO2 capture. In the present study, we prepared five new three-component DESs by functionalization of choline chloride-ethanolamine (1,7, mol,mol) DES using different types of amines: diethanolamine (amine type 2), methyldiethanolamine (amine type 3), piperazine (amine type 2) as well as 1-(2-aminoethyl)piperazine (amine type 1 and 2). All of the prepared DESs are liquid at room temperature and their melting points were in the range of 265–276 K. The solubility of CO2 in the studied DESs was measured at pressures up to 2 MPa and 298.15 K. The obtained experimental data were analyzed by the use of generic Redlich-Kwong equation of state (RK-EOS) model and Henry's law constant have been calculated from the obtained experimental data through the EOS correlation. All the studied DESs show chemical absorption of CO2 which can be approved based on the excess enthalpy and Gibbs energy functions. FT-IR spectroscopy and 13C NMR verified the formation of carbamate in the CO2 absorption process which revealed the chemisorption of CO2 in the studied DESs. The ideal association model has been utilized to describe the excess thermodynamic functions and two different types of the chemical association have been detected AB2 and AB, (A refer to DESs and B to CO2). Based on the obtained solubility data, the amines that enhanced the absorption capacity of choline chloride-ethanolamine (1,7) follow the trend as follows: piperazine > aminoethylpiperazine > methyldiethanolamine > diethanolamine. Therefore, piperazine can be considered as an absorption enhancer. The viscosity of DESs before and after CO2 absorption as well as the thermal behavior of the DESs were also investigated.

  • 19. Sefidari, H.
    et al.
    Wiinikka, H.
    Lindhlom, B.
    Nordin, L. O.
    Wu, G.
    Yazhenskikh, E.
    Mueller, M.
    Ma, Charlie
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Oehman, M.
    Comparison of high-rank coals with respect to slagging/deposition tendency at the transfer-chute of iron-ore pelletizing grate-kiln plants: a pilot-scale experimental study accompanied by thermochemical equilibrium modeling and viscosity estimations2019In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 193, p. 244-262Article in journal (Refereed)
    Abstract [en]

    Iron-ore pelletizing plants use high-rank coals to supply the heat necessary to process ores. Ash material from coal, in combination with iron-ore dust originating from the disintegration of the pellets, can cause deposition/slagging which often leads to severe production losses and damage. Deposition/slagging is most prominent in the hot areas of the grate-kiln setup and is more severe at the inlet of the rotary-kiln, i.e., the transfer-chute. Following on from our previous work, high-rank bituminous coals with potential for use in the pelletizing process were combusted in a pilot-scale (0.4 MW) pulverized-coal fired experimental combustion furnace (ECF). The fly-ash particles and short-term deposits were characterized to shed light on the observed difference in slagging/deposition tendencies of the coals. Global thermodynamic equilibrium modeling, in combination with viscosity estimates, was used to interpret the experimental findings and investigate the effect of the coal-ash composition upon deposition/slagging. This approach was carried out with and without the presence of Fe203rich pellet-dust under oxidizing conditions within the temperature range at the transfer-chute of iron-ore pelletizing rotary-kilns. Based on the findings, a Qualitative Slagging Indicator (QSI) was proposed that can help pre-screen new solid fuels for potential slagging issues. The proposed QSI highlights the following: (1) an inverse relationship between viscosity and slagging/deposition tendency of the coals was observed (2) as viscosity decreases (either with increasing temperature or due to the change in the coal-ash composition), stronger deposits will form that will complicate the mechanical removal of the deposited layer. It was therefore inferred that low viscosity molten phases facilitate deposition/slagging, which is exacerbated by the presence of fluxing agents (e.g., CaO, MgO, K2O, Na2O, and Fe2O3) in the deposits. The low viscosity coal-ash-induced molten phases are also more likely to interact with the Fe2O3-rich pellet-dust that results in further decreases in viscosity, thereby intensifying depositions. The results from this work complement the on-going research by our group to elucidate and alleviate ash-related problems in industrial grate kilns.

  • 20.
    Shukla, Shashi Kant
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikkola, Jyri-Pekka
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Industrial Chemistry & Reaction Engineering, Department of Chemical Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, Åbo-Turku, Finland.
    Melting point of ionic liquids2020In: Encyclopedia of ionic liquids / [ed] Suojiang Zhang, Singapore: Springer, 2020, p. 1-9Chapter in book (Other academic)
  • 21.
    Staničić, Ivana
    et al.
    Department of Space, Earth and Environment, Division of Energy Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Cañete Vela, Isabel
    Department of Space, Earth and Environment, Division of Energy Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Maric, Jelena
    Department of Space, Earth and Environment, Division of Energy Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Cao, Yu
    Department of Materials & Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Mattisson, Tobias
    Department of Space, Earth and Environment, Division of Energy Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Fate of lead, copper, zinc and antimony during chemical looping gasification of automotive shredder residue2021In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 302, article id 121147Article in journal (Refereed)
    Abstract [en]

    Gasification experiments in this study were performed in a 2–4 MW indirect gasifier coupled to a semi-commercial CFB combustor at Chalmers University of Technology. Experiments were carried out during 13 days with automotive shredder residue (ASR), giving a unique opportunity to investigate the bed material under realistic conditions and with long residence times. The metal rich ash was accumulated in the bed, gaining some oxygen carrying capabilities, creating a chemical looping gasification (CLG) process. This study aims to expand the knowledge about the chemistry of zinc, copper, lead and antimony during CLG of ASR. Several experimental methods have been utilized, such as XRD, SEM-EDX and XPS along with detailed thermodynamic calculations to study chemical transformations that can occur in the system. Thermodynamic calculations showed that the reduction potential affect the phase distribution of these elements, where highly reduction conditions result in heavy metals dissolving in the slag phase. Copper and zinc ferrites, lead silicates and antimony oxides were identified at the particle surfaces in the bottom ash. The formation of an iron rich ash layer plays an important role, especially for copper and zinc speciation. The main pathways in the complex CLG system have been discussed in detail.

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  • 22. Ullakko, Kari
    et al.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Pietikäinen, Juha
    Isothermal Martensite Transformation of Fe-Ni-C Alloys as a Function of Hydrostatic Pressure1990In: Materials Science Forum volumes 56-58: Martensitic Transformations: Proceedings of the 6th International Conference on Martensitic Transformations (ICOMAT 89), Sydney 1989, Zürich: Trans Tech Publiations , 1990, p. 197-200Conference paper (Refereed)
    Abstract [en]

    Isothermal martensite transformation as a function of hydrostatic pressure was studied in Fe-Ni-C alloys. It was observed that the transformation was much the same as it happens as a function of time. Any noticeable differences in the morphology between isothermal and athermal martensite were not seen.

  • 23.
    Viggh, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Comparison of FToxid and Gtox thermodynamic databases used for simulating clinker mineralsManuscript (preprint) (Other academic)
  • 24.
    Weiland, Fredrik
    et al.
    RISE Energy Technology Center AB, Piteå, Sweden.
    Lundin, Lisa
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Celebi, Mustafa
    RISE Energy Technology Center AB, Piteå, Sweden.
    van der Vlist, Klaas
    Smurfit Kappa Group, Paper Production Technology, AX Roermond, Netherlands.
    Moradian, Farzad
    Stena Recycling International AB, Göteborg, Sweden.
    Aspects of chemical recycling of complex plastic waste via the gasification route2021In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 126, p. 65-77Article in journal (Refereed)
    Abstract [en]

    Oxygen blown high-temperature gasification constitutes an opportunity for chemical recycling of plastic wastes. This article summarizes the results from comparative tests of combustion and gasification of two complex plastic wastes: a plastic reject (PR) from processing recycled paper and an automotive shredder residue (ASR). Calculated gasification efficiencies corresponded to about 80% and 60%, respectively. Gasification resulted in lower yields of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) compared to direct combustion. A two-stage process, including gasification followed by syngas combustion, reduced the emissions of HCl and PCDD/F in the flue gas to <1.4% and <0.2%, respectively, compared to the levels from direct combustion of the PR feedstock. Most of the PCDD/F (>99%) was captured along with particulate matter (soot) during gasification. The contribution to the toxic concentration of PCDD/F was mainly from the PCDF congeners. Fly ash particulate matter from ASR combustion contained a significant proportion of zinc, which thus constitutes a great potential for use in zinc recycling.

  • 25.
    Zäll, Erik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Absolicon Solar Collector AB, Härnösand, Sweden.
    Nordenström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Järn, Mikael
    RISE Research Institutes of Sweden, Materials and Surface Design, Stockholm, Sweden.
    Mossegård, Jonatan
    Absolicon Solar Collector AB, Härnösand, Sweden.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Environmentally sustainable electroplating of selective cobalt-chromium coating on stainless steel for efficient solar collectors2022In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 245, article id 111821Article in journal (Refereed)
    Abstract [en]

    Half of today's global energy consumption is in the form of heating and cooling. Solar collectors are the most promising sustainable alternative to fossil fuels in this sector. The most important component in a solar collector is the receiver, which by use of a selective surface absorbs and converts solar irradiance to thermal energy. Herein, a novel selective surface for low-to mid-temperature solar collectors is developed, studied and presented. The surface is produced by electroplating a cobalt-chromium coating on a stainless steel substrate using an electrolyte based on a deep eutectic solvent. Our method makes use of trivalent instead of traditionally used hexavalent chromium, which significantly reduces health-related issues and makes it more environmentally benign. We obtain a coating of chromium doped cobalt where the surface exhibits an absorptance and emittance of 0.96 and 0.14, respectively, giving it a solar-to-thermal efficiency of 0.95. An observed loss in optical efficiency, is shown to correlate to an oxidation of the metallic cobalt to Co3O4 at elevated temperatures. We further show that this oxidation can be mitigated by dip-coating a protective silica top coating, which concurrently improves the optical selectivity of the surface. The present selective surface is efficient, cheap, scalable, and easy to produce sustainably, making it competitive to industry standards. We foresee that our method will have impact on the advancement of improved low-to mid-temperature solar collectors, assisting a faster transition towards a sustainable society.

1 - 25 of 25
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