Browsing by Author "Taskinen, P."

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  • Copper matte - slag reaction sequences and separation processes in matte smelting
    (2018-01-01) Guntoro, P. I.; Jokilaakso, A.; Hellstén, N.; Taskinen, P.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Dok su reakcije sagorevanje čestica i oksidacija halkopirita prilikom topljenja suspenzija dobro proučeni, postoji jako mali broj studija koje se ticu reakcija izmedu tečnih faza i raslojavanja bakrenca i šljake prilikom topljenja bakrenca. U ovom radu izvršena su eksperimentalna istraživanja u vazdušnoj i argonskoj atmosferi korišćenjem mešavine sintetičke šljake i koncentrata halkopirita. Prikazan je redosled reakcija i procesa separacije koji se dešavaju u procesu topljenja. Takode su dati i mogući ograničavajući faktori u celokupnom procesu. Rezultati ovog rada predstavljaju važnu osnovu za buduće radove u oblasti formulacije kinetike reakcija izmedu tečnog bakrenca i šljake u procesu topljenja bakrenca.
  • Determination of metallization degree of pre-reduced chromite with image and Rietveld analysis
    (2020) Leino, T.; Taskinen, P.; Eric, R. H.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Metallization degree of pre-reduced chromite was determined using two methods. The chromite samples were reduced in the solid state by methane-hydrogen gas mixtures. First method was image analysis of micrographs obtained by scanning electron microscope where heavier metallic phases appeared as bright white areas which were relatively easy to segment using a thresholding algorithm. The second technique was Rietveld analysis of X-ray powder diffraction pattern which fitted a calculated profile onto a measured X-ray diffraction pattern to gain information about phase quantities. Rietveld refinement and phase composition analysis was performed with PANalytical's X'Pert HighScore Plus software from the XRPD (X-ray powder diffraction) data. Both techniques were in good agreement. Metallization degrees for the investigated samples ranged from 15 to 65 % depending on the extent of reduction which was a function of time, reduction temperature, and methane content of the gas mixture. These results were promising and indicate that either image analysis or X-ray Rietveld analysis can be used as a relatively fast method to determine the degree of metallization of pre-reduced samples in comparison to the slow and tedious chemical analysis.
  • Experimental study on the extraction of calcium, magnesium, vanadium and silicon from steelmaking slags for improved mineral carbonation of CO 2
    (2019-05-01) Owais, M.; Järvinen, M.; Taskinen, P.; Said, A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    In this paper X2PCC (Calcium containing material X to Precipitated Calcium Carbonate) process wherein a steelmaking slag is used as a source of Ca for mineral carbonation of CO 2 was studied. Mineral carbonation refers to binding of CO 2 into mineral carbonates, here CaCO 3 . In the process, we first dissolve Ca selectively from the slag, then separate the solid phase and finally, bubble CO 2 into the solution to make precipitated calcium carbonate CaCO 3 . Based on our current understanding, the extraction step limits the process feasibility. In the experiments, ammonium chloride (NH 4 Cl) water solution was used as an extracting solvent with varying concentrations of 0, 0.5, 1 and 2 mol/L using slag to solvent ratio of 100 g/L. The main objective of this study was to determine the optimal concentrations of solvent and particle size for leaching out calcium from the slag. Tests were performed at room temperature with varying particle size and solvent concentration. The extraction behaviors of different size fractions of the slag, 0-50 μm, 50-74 μm and 74-125 μm were studied. Dissolution results showed that with high solvent concentrations calcium extraction efficiency increases but at the same time, other elements are leached, such as vanadium, silicon and magnesium that act as impurities in the subsequent carbonation stage. It was found that with the largest particles, Ca extraction becomes limited by mass transfer and the availability of Ca from the particle. Our hypothesis is that the surface layer of the particles gets blocked by reaction products and stops the reaction. With the smallest particle size, before the surface gets blocked, more calcium could be extracted and the maximum extraction efficiency was not reached.
  • Flue Dust Behaviour in FSF-Arsenic Condensation in Offgas Line Conditions
    (2024-07-03) Taskinen, P.; Wan, X.; Sukhomlinov, D.
     A4 Artikkeli konferenssijulkaisussa
    The suspension smelting oxidation step has favourable conditions to generate chemical flue dust from the low-boiling elements of the feed mixture due to the high particle temperatures in the reaction shaft where combusting sulphide mineral particles reach temperatures above the melting point of magnetite. Arsenic, antimony, lead, and zinc are common impurity elements of high volatility in copper concentrates. They tend to accumulate in the flue dust due to the high volatility and closed mode of the flue dust circulation practiced in most industrial smelting-converting processes. Then, the only outlets for the volatile impurities are the anodes and the discard slag. A separate flue dust treatment for impurity removal is an option but it creates an additional step for the smelting plant and cost in the processing. When the concentrate grades decrease, and their impurity levels rise this outlet for the trace elements may become necessary. The arsenic condensation mechanisms in dust-free conditions in the copper flash smelting process gas train have been recently studied in SO2-Air-N2 gas mixtures. It seems that the formation mechanism of arsenic-containing dust deposits is kinetically constrained, and their chemistries are influenced by the condensation temperature and atmosphere.
  • Happikonsentraatiokennon toiminta inerteissä kaasuseoksissa
    (1976) Kuusisto, Risto
     Helsinki University of Technology | Master's thesis
  • Metalli-oksidisulan tasapainotuslaitteiston rakentaminen ja testaus
    (1979) Liikanen, Esa
     Helsinki University of Technology | Master's thesis
  • Reduction of Kemi chromite with methane
    (2018-06-01) Leikola, M.; Taskinen, P.; Eric, R. H.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Kemi chromite ore from Finland was reduced in CH4-H2 gas mixtures at temperatures from 1100° to 1350°C. Experimental variables were time, temperature, and the CH4 content of the gas mixture. The phases in reacted samples were determined by XRD and quantitative phase analysis was performed using the Rietveld method. Particle morphology and phase compositions were determined using SEM and EDS analysis. Reduction proceeded through a shrinking core model in two stages. In the first stage, hydrogen and carbon from the cracking of methane reduced the iron and some chromium to carbides. The chromium in the remaining spinel was reduced during the second stage. Iron was essentially reduced in full after 30 minutes when the temperature reached 1300°C, and at 1350°C it was completely reduced within 20 minutes. At this highest temperature, all of the chromium was eventually reduced, the residue consisting of aluminum and magnesium oxides with varying amounts of silica. At the surface of the particle iron and chromium, together with carbon, formed two alloys, an iron-dominated and a chromium-based one. The iron-based phase was partially molten at the higher temperatures. At 1300°C and 1350°C the metallization was complete. Reduction of Kemi chromite with a CH4-H2 mixture is judged as highly efficient, since high of reduction extents could be reached faster at lower temperatures compared to carbothermic reduction. This is attributed to the very high activity of carbon (way above 1.0) due to the cracking of methane into hydrogen and carbon at around 550°C in the presence of a solid phase.
  • Thermodynamic properties of Ag-Pt alloy measured using a solid electrochemical method
    (2018-01-01) Santoso, I.; Taskinen, P.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    AlthoughAg-Pt system is crucial for several technological applications, investigations of the thermodynamic properties of this system are limited. In the present study, activity of silver at various temperatures in the platinum rich solid solution was measured by a solid electrochemical method and employing AgI as the solid electrolyte. The EMF was determined using a galvanic cell (–)|Ag|AgI|Ag – Pt alloy|C|Pt(+), which provided novel experimental data on thermodynamic properties of aAg-Pt alloy.Activity, partial molar of Gibbs energy, enthalpy and entropy of silver in a solid solution containing 1 at % Ag between 573 and 673 K have been calculated. The results indicated that the activity of silver obtained in the present study shows a large positive deviation from the ideal Raoultian behavior. Microstructures of alloys with different compositions were also compared.