Browsing by Author "Jokilaakso, Ari"

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  • Aineensiirron mallintaminen kemiallisissa prosesseissa moderneilla laskentamenetelmillä
    (2019-05-07) Ahonen, Tommi
     Kemiantekniikan korkeakoulu | Bachelor's thesis
  • Arsenic Condensation and Reaction Mechanisms in Flash Smelting Off-Gas Line Conditions
    (2023-10) Wan, Xingbang; Sukhomlinov, Dmitry; Taskinen, Pekka; Lindgren, Mari; Michallik, Radoslaw; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Arsenic is a common impurity element in sulfide concentrates. It tends to accumulate in the flue dust of smelting furnace due to the volatility and internal circulation of the flue dust practiced in the smelting-converting process chain. The only outlets for arsenic are anodes and discard slag. Arsenic condensation in dust-free conditions was studied below 800 °C where the gas atmosphere was controlled by SO2-air-N2 gas mixtures. Based on these experimental results, we confirm the kinetically constrained formation mechanism of the arsenic-containing dust, and its speciation into metallic, oxidic (III, V), and sulfidic species. The influences of temperature and atmosphere on the speciation of arsenic were compared with industrial data and discussed. Graphical Abstract: [Figure not available: see fulltext.]Condensed arsenic‐bearing particles collected by electrophoretic forces on the surface of fused SiO2 in SO2‐O2 atmospheres: the crystal morphology shows euhedrally facetted As2O3 crystals and initially molten As‐OSalloy droplets together with poorly crystallized AsS x particles.
  • Battery scrap and biochar utilization for improved metal recoveries in nickel slag cleaning conditions
    (2020-12) Avarmaa, Katri; Järvenpää, Marko; Klemettinen, Lassi; Marjakoski, Miikka; Taskinen, Pekka; Lindberg, Daniel; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cobalt is a critical, high-value metal used extensively in batteries and other sustainable technologies. To secure its supply in future, it is utmost important to recover cobalt efficiently from industrial wastes and recycled End-of-Life batteries. This study aims at finding ways to improve the reduction of cobalt as well as valuable metals nickel and copper in nickel slag cleaning furnace conditions by using both traditional fossil-based coke and a more sustainable option, low-CO2 footprint biochar, as reductants. A cobalt-rich fraction of battery scrap (25.5 wt% Co) was also used as a secondary feed. The experimental technique consisted of reduction experiments with different times at 1400◦C under inert atmosphere, quick quenching and Electron Probe X-ray Microanalysis. The use of biochar resulted in faster reaction kinetics in the reduction process, compared to coke. Moreover, the presence of battery scrap had a clear impact on the behavior and reduction kinetics of the elements and/or enhanced settling and separation of matte and slag. The addition of scrap increased notably the distribution coefficients of the valuable metals but consequently also the iron concentration in matte which is the thermodynamic constraint of the slag cleaning process.
  • The behavior of a synthetic nickel matte in the single particle studies
    (1995) Peuraniemi, Esa
     Helsinki University of Technology | Master's thesis
  • Behavior of Battery Metals Lithium, Cobalt, Manganese and Lanthanum in Black Copper Smelting
    (2020-03-02) Danczak, Anna; Klemettinen, Lassi; Kurhila, Matti; Taskinen, Pekka; Lindberg, Daniel; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Recycling of metals from different waste streams must be increased in the near future for securing the availability of metals that are critical for high-tech applications, such as batteries for e-mobility. Black copper smelting is a flexible recycling route for many different types of scrap, including Waste Electrical and Electronic Equipment (WEEE) and some end-of-life energy storage materials. Fundamental thermodynamic data about the behavior of battery metals and the effect of slag additives is required for providing data necessary for process development, control, and optimization. The goal of our study is to investigate the suitability of black copper smelting process for recycling of battery metals lithium, cobalt, manganese, and lanthanum. The experiments were performed alumina crucibles at 1300 °C, in oxygen partial pressure range of 10−11‒10−8 atm. The slags studied contained 0 to 6 wt% of MgO. Electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) techniques were utilized for phase composition quantifications. The results reveal that most cobalt can be recovered into the copper alloy in extremely reducing process conditions, whereas lithium, manganese, and lanthanum deport predominantly in the slag at all investigated oxygen partial pressures.
  • Behavior of Ga, In, Sn, and Te in Copper Matte Smelting
    (2019-12-01) Sukhomlinov, Dmitry; Klemettinen, Lassi; O’Brien, Hugh; Taskinen, Pekka; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The distributions of Ga, In, Sn, and Te between copper-iron mattes and silica-saturated iron silicate slags over a wide range of matte grades 55 to 75 pct Cu were determined at 1300 °C using a gas-phase equilibration-quenching technique and direct phase composition analysis by Electron Probe X-ray Microanalysis and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry. Alumina from aluminum, a typical minor element of electric and electronic copper scrap, and lime were adopted as slag modifiers for increasing the trace element recoveries. Gallium and tin were distributed predominantly in the slag, indium preferred sulfide matte at low matte grades and slag at high, whereas tellurium strongly favored the sulfide matte in particular in high matte grades. The slag modifiers alumina and lime had a minor impact on the distribution coefficients of gallium and tin, but for indium and tellurium the distribution coefficients were more strongly affected by the basic oxides. The strong tendencies of tin and tellurium to vaporize at the experimental temperature were confirmed.
  • Behavior of Nickel as a Trace Element and Time: Dependent Formation of Spinels in WEEE Smelting
    (2018) Klemettinen, Lassi; Avarmaa, Katri; Taskinen, Pekka; Jokilaakso, Ari
     A4 Artikkeli konferenssijulkaisussa
    For better understanding and maximal value utilization of the WEEE smelting process, the behavior and distribution of different trace elements must be known. In this study, the behavior of nickel as a trace element was studied in an equilibrium system with metallic copper—spinel saturated iron silicate slag (with 3 wt-% K2O)—iron aluminous spinel—gas. The experiments were conducted in alumina crucibles at 1300 °C, in oxygen pressure range of 10−10–10−5 atm. A time series of 15–60 min experiments was also conducted for investigating the formation rate of the primary spinel phase in the system. The results show that the distribution coefficient of nickel between metallic copper and liquid slag changes from approximately 70 to 0.4 along the increasing oxygen pressure range. In addition, a significant part of the nickel deports into the spinel phase. The spinel formation was investigated based on composition analysis results and visual observations from SEM-images.
  • Behavior of tin and antimony in secondary copper smelting process
    (2019-01-01) Klemettinen, Lassi; Avarmaa, Katri; O’brien, Hugh; Taskinen, Pekka; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Different types of metal-bearing wastes, such as WEEE (Waste Electrical and Electronic Equipment), are important urban minerals in modern society, and the efficient recycling and reuse of their metal values is of key interest. Pyrometallurgical copper smelting is one of the most prominent ways of treating WEEE, however, more accurate experimental data is needed regarding the behavior of different elements during each process stage. This article investigates the behavior of tin and antimony, both commonly present as trace elements in electrical and electronic waste, in secondary (i.e., sulfur-free) copper smelting conditions. The experiments were conducted in oxygen partial pressure range of 10 −10 –10 −5 atm, covering the different process steps in copper smelting. The basis of the equilibrium system was metallic copper–iron silicate slag, with the addition of alumina and potassium oxide to account for the presence of these compounds in the actual industrial process. The results showed that the distribution coefficients of both trace metals, L Cu/slag = [wt % Me] copper /(wt % Me) slag , increased significantly as a function of decreasing oxygen pressure, and the addition of basic potassium oxide also had an increasing effect on the distribution coefficient. A brief comparison between EPMA and LA-ICP-MS (electron probe microanalysis and laser ablation–inductively coupled plasma–mass spectrometry), the two in situ analytical techniques used, was also presented and discussed.
  • Behavior of Waste Printed Circuit Board (WPCB) Materials in the Copper Matte Smelting Process
    (2018-11-01) Wan, Xingbang; Fellman, Jani; Jokilaakso, Ari; Klemettinen, Lassi; Marjakoski, Miikka
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The amount of waste electrical and electronic equipment (WEEE) in the world has grown rapidly during recent decades, and with the depletion of primary ores, there is urgent need for industries to study new sources for metals. Waste printed circuit boards (WPCB) are a part of WEEE, which have a higher concentration of copper and precious metals when compared to primary ore sources. PCB materials can be processed using pyrometallurgical routes, and some industrial processes, such as copper flash smelting, have utilized this type of waste in limited amounts for years. For the purpose of recycling these materials through smelting processes, this work studied the behavior of WPCB scrap when dropped on top of molten slag. A series of experiments was carried out during this research at a temperature of 1350°C, in an inert atmosphere with different melting times. The time required for complete melting of the PCB pieces was 2–5 min, after which molten alloy droplets containing Cu, Pb, Sn, Ni, Au, and Ag formed and started descending toward the bottom of the crucible. The ceramic fraction of the PCB material mixed with slag and the polymer fraction was pyrolyzed during the high-temperature experiments. The results give an understanding of PCB melting behavior and their use as a part of the smelting furnace feed mixture. However, more research is needed to fully understand how the different elements affect the process as the amount of PCB in the feed increases. The physical behavior and distribution of PCB materials in fayalite slag during the smelting process are outlined, and the results of this work form a basis for future studies about the chemical reaction behavior and kinetics when PCB materials are introduced into the copper smelting process.
  • Telluurin ja vismutin käyttäytyminen suspensiohapetuskokeissa
    (1998) Repo, Lea
     Helsinki University of Technology | Master's thesis
    Työn teoriaosassa käsitellään telluurin ja vismutin käyttäytymistä kuparirikasteen prosessoinnissa. Aluksi esitellään lyhyesti kuparin tärkeimpiä liekkisulatus- ja konvertointiprosesseja ja yleisesti epäpuhtauksien käyttäytymistä eri prosesseissa. Teoriaosassa on tarkasteltu telluurin esiintymistä eri yhdisteissä ja sen yleisiä ominaisuuksia sekä termodynamiikkaa. Telluurin jakautumiskäyttäytymistä kiven, kuonan, metallin ja kaasufaasin kesken on käsitelty lähinnä erilaisten laboratoriotutkimusten pohjalta. Teoriaosan lopussa on tarkasteltu telluurin esiintymistä anodiliejussa. Esitetyissä laboratoriotutkimuksissa osoitettiin, että telluurin liukoisuus kuonaan laskee kiven kuparipitoisuuden kasvaessa ja kuonakomponenttien pitoisuuksien kasvaessa. Lisäksi lämpötilan noston ja hapen osapaineen kasvun todettiin lisäävän telluurin pitoisuutta kivessä. Kokeellisessa osassa tutkittiin suomalaisen kultarikasteen käyttäytymistä korkealämpötilahapetuksessa. Rikasteelle tehtiin hapetuskokeita TKK:lla laboratoriomittakaavaisella laminaarivirtausuunilla. Tarkoituksena oli selvittää rikasteen epäpuhtauksien telluurin ja vismutin poistumakäyttäytymistä simuloiduissa liekkisulatusuunin reaktiokuilun suspensio-olosuhteissa. Kokeet työssä käytetylle rikasteelle suoritettiin kahdessa eri lämpötilassa, 1200 ja 1300 °C, reaktiokaasun happipitoisuuden (0, 2, 50, 75 til-% 0_2) ja reaktiomatkan (10, 13, 19,5, 26,5, 34 ja 42 cm) funktiona. Pääosin kokeet tehtiin fraktioilla +74 µm ja 53-74 µm. Näytteistä tehtiin kemialliset analyysit ORC:llä Porissa. Näytteiden analyysien avulla laadittiin rikin, telluurin ja vismutin poistumakäyrät reaktiomatkan ja happipitoisuuden funktiona. Näiden analyysien lisäksi näytteitä tutkittiin optisella mikroskoopilla ja analysoitiin SEM:n EDS:llä. Koeajojen tuloksien perusteella saatiin tietoa lämpötilan, reaktiokaasun happipitoisuuden ja reaktiomatkan pituuden vaikutuksesta epäpuhtauksien poistumiseen ja mineralogisiin muutoksiin. Parhaiten telluurin poistumista näissä kokeissa edisti korkea lämpötila ja pitkä reaktiomatka. Vismutin poistumista kaasufaasiin edistää alhainen happipitoisuus, pitkä reaktiomatka ja korkea lämpötila. Suotuisimmissakin olosuhteissa alkuperäisestä telluurista jäi rikasteeseen noin 10-20 % ja vismutista noin 40 %.
  • Behaviour of trace elements in the direct Outokumpu nickel smelting operation
    (2023-12-12) Astikainen, Oskar
     Kemian tekniikan korkeakoulu | Master's thesis
  • CFD Modeling of Multiphase Flow in an SKS Furnace with New Tuyere Arrangements
    (2022-02) Song, Kezhou; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    There has been a great deal of focus on the optimization of tuyere arrangements in SKS bottom blown copper smelting furnaces since the last decade, as the improved furnace operation efficiency of SKS technology has potential that cannot be ignored. New –x + 0 + x deg tuyere arrangements with 14 tuyeres are proposed in this research paper. Using a previously verified numerical model, CFD tests on the velocity distribution and wall shear stress for scaled-down SKS furnace models were conducted, with a constant total volumetric gas flow rate, and different operating parameters and furnace cross-section geometries. The results indicate that, at a relatively low gas injection speed compared with the previously optimized tuyere arrangement, although the –x +0 +x deg tuyere arrangements are unable to supply enhanced agitation in the typical round furnaces, they achieve better performance in elliptical furnaces. At a comparatively higher gas injection speed, the – x + 0 + x deg tuyere arrangements can improve the agitation performance in a round furnace while maintaining an acceptable wall shear stress on the bottom and side wall. The agitation enhancement with the − x +0 +x deg tuyere arrangements can essentially be attributed to stronger interactions between bubble plumes and furnace side walls. To further exploit the advantages of the new tuyere arrangements, an optimized tuyere angle was confirmed by a full-scale furnace model simulation.
  • CFD Modeling of Multiphase Flow in an SKS Furnace: The Effect of Tuyere Arrangements
    (2021-06) Song, Kezhou; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The emerging bottom blown copper smelting (SKS) technology has attracted growing interest since it came into production. To further reveal the agitation behavior inside the bath and optimize the variable parameters, CFD simulation was conducted on a scaled down SKS furnace model with different tuyere arrangements. The Multi-Fluid VOF model was used for the first time in SKS furnace simulation and the simulated results show good agreement with an experimental water model reported in the literature, in terms of plume shape and surface wave. It was found that a low velocity region would appear on the opposite side of the bubble plume and persisted for a long time. To enhance the agitation in the low velocity region and reduce the dead zone area, an arrangement with tuyeres installed at each side of the furnace was recommended. Results suggested that a smaller tuyere angle difference would help to strengthen the agitation in the system. However, further investigation indicated that the difference in tuyere angle between two rows of tuyeres should be limited within a certain range to balance the requirements of higher agitation efficiency and longer lining refractory lifespan.
  • The CFD Modeling of Multiphase Flow in an SKS Furnace: The Effect of Tuyere Diameter and Bath Depth
    (2022-04) Song, Kezhou; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    CFD simulation using a multi-fluid VOF model on scaled-down SKS furnace multiphase flow was conducted, targeting the agitation performance under conditions of different tuyere diameters and bath depths, at a constant total gas volumetric flow rate. The results indicate that an increased bath depth contributes to the lateral movements of the matte and air phased, significantly promoting the agitation at the far side of the plumes. The characteristic of a deep bath allows larger tuyere diameters operated at a lower gas injection speed, to achieve comparatively smaller low velocity regions and dead zones. In addition, the wall shear stress was found to correlate with the distribution of low-velocity regions. Since the selections of tuyere diameter and bath depth are of major importance in the optimizing of flow fields, the results from this simulation offer good references for the future operation and design of SKS furnaces and other similar industrial vessels.
  • CFD modeling of the multiphase flow in an SKS furnace—The effect of melt density and viscosity
    (2023-05-15) Song, Kezhou; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A previously reported numerical method using the multi-fluid VOF model to simulate an SKS furnace multiphase flow was further verified to provide a good reference for the macroscopic flow field simulation of industrial vessels with similar geometry. Using the verified numerical model, CFD simulation of a full-scale SKS furnace multiphase flow was conducted, targeting the agitation performance with different melt densities and viscosities, under constant furnace operating conditions. According to this simulation, the melt density and viscosity in a common applied range in industry is not able to significantly affect the bath agitation efficiency like other parameters, such as the tuyere diameter and bath depth. More specifically, the results indicate that an increased melt density or viscosity slightly weakens the melt flow motion, and increases the wall shear stress. Since variation in melt density and viscosity is common in industry, the results from this simulation offer a good basis for the estimation of SKS furnace operating performance and the adjustment of the physical properties of the melt in SKS furnaces or other similar industrial vessels.
  • CFD Modelling of matte droplets coalescence in Flash smelting settler
    (2019-06-17) Karadahalli Nagesh, Shreyas
     Insinööritieteiden korkeakoulu | Master's thesis
    Computer simulations are popular due to difficulty in setup of conventional experimental methods at high temperature processes. Computational Fluid dynamics is an important tool to study settling mechanism in Outotec's flash smelting settler. Commercial Ansys Fluent model was used to study settling previously by researchers, but no study was done to model coalescence. The thesis aims in studying the suitability of the Ansys fluent built in code to model coalescence for flash smelting settler. The success of the model helps to understand copper loss mechanisms and find ways to increase copper recovery. Firstly, collision theory and coalescence mechanism is reviewed thoroughly. Secondly, Ansys fluent built in models for modeling coalescence are listed and compared to select best mathematical model. The primary criteria for selection was ability to model collisions, coalescence, particle tracking and better visualization capacities. The selected discrete phase model is parametrized to model coalescence during settling of matte droplets through slag phase. It is noted that DPM could be used to simulate settling and coalescence of matte droplets. DPM can be used to get the idea of the process/coalescence phenomenon in a short period. The simulation showed droplets change trajectory after collisions/coalescence. Simulation also revealed coalescence dramatically affects settling time. Settling time is not only affected by increase in droplet diameter but also due to change in droplet trajectory after coalescences. However, Parametrized DPM model uses parcels injection technique that makes it difficult to track droplets individually for accurate comparison. In future user defined function should be written to identify and track droplets individually for accurate analysis of individual droplets.
  • CFD-DEM models for matte droplet settling in a flash smelting settler
    (2023-11) Jylhä, Jani-Petteri; Jokilaakso, Ari
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The flash smelting process is widely used in copper production. In the process, sulfidic feed and flux are oxidized. The heat released in the reactions melts the feed which forms a slag layer through which matte droplets must settle. Understanding the different phenomena affecting the settling is important to minimize losses. Due to the high temperature, simulation methods were employed to study settling. In this work, coupled CFD-DEM was used to study the effect of coalescence and reactions with in-house built submodels and scaled-down geometries. Colliding droplets often coalesce into larger droplets while reactions decrease their size and make them denser. These increase the settling velocity which is further enhanced by the formation of a channeling flow. Channels make the droplet cluster denser causing more collisions. This method enables the phenomena to be studied at the individual droplets' details, although simulating a full-scale process is beyond the available computational resources.
  • CFD-DEM simulation of two-phase flows in the flash smelting settler
    (2018-07-31) Jylhä, Jani
     Kemian tekniikan korkeakoulu | Master's thesis
    Computer simulations have become an important tool in research. CFD-DEM coupling has been used to simulate particle and fluid flows in pyrometallurgical reactors, but no study could be found where it was used to simulate liquid droplets in fluid. In this work viability of the coupling for flash smelting settler was studied as the tool could help in studying copper loss mechanisms and optimizing the process. First, experiment with water droplet in oil was made, and results from the experiment were used to validate CFD-DEM model using two liquids. Validated model was used to simulate slag layer in a flash smelting furnace. It was found that CFD-DEM coupling can be used to simulate settling and collisions of matte droplets. With limited number of droplets, the droplets formed mixed layers, which started to separate due to differences in settling velocities. The settling velocities corresponded well to theoretically calculated values. Also, two different collision types were observed: high and low velocity collision in which the droplets bounced apart or stayed in contact until the larger droplet had bypassed the smaller one, respectively. However, phenomena such as coalescence should be researched and taken into account for more sophisticated simulation.
  • Characterization of Copper Smelting Flue Dusts from a Bottom-Blowing Bath Smelting Furnace and a Flash Smelting Furnace
    (2020-12) Chen, Yujie; Zhao, Zongwen; Taskinen, Pekka; Liang, Yanjie; Ouyang, Hongchuan; Peng, Bing; Jokilaakso, Ari; Zhou, Songlin; Chen, Tao; Peng, Ning; Liu, Hui
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The smelting technology and flue dust treatment have an influence on the physical and chemical characteristics of flue dusts collected in copper smelting. We characterized flue dusts from a Bottom-Blowing Bath Smelting (BBS) process and from a Flash Smelting (FS) process by determining their comprehensive physical, chemical, and mineralogical characteristics. Annual flue dust generation data showed that the rate of the BBS process (2 to 3 pct) was clearly lower than that of FS process (5 to 6 pct). The results revealed that copper smelting flue dusts from the FS exhibited a larger entrainment of solids and a smaller particle size than the BBS. The crystallographic and chemical compositions of the samples indicated that the FS flue dusts have a higher degree of crystallinity than those of the BBS. Fe3O4, CuSO4 and PbSO4, Fe3O4, CuFe5O8 were the predominant crystalline phases in the FS and BBS flue dusts, respectively. In the FS and BBS flue dusts, amorphous multicomponent Cu-Zn-FeOx and Cu-Zn-S phases were formed, respectively. Mineralogical examinations and a stepwise chemical extraction confirmed that the majority of arsenic existed in amorphous form and mostly as pentavalent As5+ arsenate or As2O5 except that in BBS-ESPD.
  • Characterization of metallurgical slags using XPS, XANES, Ramand- and Mössbauer spectrscopy
    (2023-09-18) Mohamoud, Nuura
     Kemiantekniikan korkeakoulu | Bachelor's thesis