Gudrun Saevarsdottir

Reykjavik University · Mechanical and electrical engineering

The global community has set a goal of carbon neutrality by 2050. Almost one-fourth of the global emissionsEmissions, attributed to direct emissionsEmissions from industrial processes, must be addressed by developing zero-carbon alternatives for each process, including the production of aluminumAluminum. Several companies and research institutions...

Reducing CO2 emissions from aluminum smelters is of great interest to reach the goal of carbon neutrality. One possible approach is to implement carbon captureCarbon capture and sequestration techniques (CCS). This is already being done within the geothermal sector in Iceland, where captured CO2 is sequestered through the Carbfix method of minerali...

Haraldsson, Hákon ValurTraustason, HalldórTesfahunegn, Yonatan A.Tangstad, MereteSævarsdóttir, GurúnElectric arcs are necessary for high Si yield in submerged arc furnaces (SAFs) for Si/FeSi production, and a certain fraction of heat dissipation in the arc enables optimal operating conditions. Direct measurement of the arc characteristics is imposs...

Electrochemically produced Si in molten salts can be used to fabricate electronic and photovoltaic devices. The major factors influencing the structure and morphology of Si deposits are electrolyte composition, applied current densities and overpotentials, type of precursors, operating temperature, and electrodeposition duration. For Si electrodepo...

Primary aluminium is produced by the Hall-Heroult process which is based on electrolysis in molten fluoride electrolyte, Na 3 AlF 6 -AlF 3 , at ~960 o C in which the raw material alumina is dissolved and decomposed into pure aluminium and CO 2 gas due to the use of carbon anodes. Alloys are made by adding pure metals prior to the casting process. A...

Carbon dioxide and other greenhouse gases are emitted during the production of primary aluminium through the Hall-Heroult process. Moreover, the process requires specific energy consumption of as high as 14.685 kWh/tonne of Al. There is an urgency to replace the existing process with a more environmentally and economically friendly process. One suc...

The industrial process for Aluminium production is the Hall-Héroult process, an electrolysis process where the alumina raw material is dissolved in a cryolite based electrolyte, the aluminium is deposited at the cathode while the oxygen from the alumina reacts anodically with the carbon anodes, which are consumed in the process. The chemical energy...

The anodic behaviour of NixFeyCuz alloy at different sodium- and potassium-cryolite based electrolyte compositions was examined by chronopotentiometry, galvanostatic polarisation, and linear sweep voltammetry at 1098 K. Steady-state anodic polarisation curves show anodic overpotential in electrolyte with molar ratio CR=(NaF+KF)/AlF3=1.4 is signific...

Due to environmental and economic concerns, carbon-free aluminium production has been an ultimate target for aluminium industries. For the last few decades, a considerable amount of research has been conducted to find a suitable inert anode that could replace the consumable carbon anodes for aluminium electrolysis. Material types such as metals, ce...

Primary aluminium is produced by the Hall-Heroult process which is based on electrolysis in molten fluoride electrolyte, Na 3 AlF 6 -AlF 3 , at ~960 o C in which the raw material alumina is dissolved and decomposed into pure aluminium and CO 2 gas due to the use of carbon anodes. Alloys are made by adding pure metals prior to the casting process. A...

In the Hall–Héroult aluminum production process, the amount of carbon consumed per ton of aluminum produced is an important metric. Deviations from ideal conditions in the reduction cells contribute to the discrepancy between the theoretical carbon consumption and the actual Net Carbon Consumption (NCC). Previous work from the authors, focused on p...

Titanium diboride (TiB 2 ) is considered a promising material for wettable cathodes in aluminum electrolysis. The demand for wettable cathodes is associated with the development of inert anode technologies to eliminate CO 2 emissions caused by the conventional aluminum reduction process. Titanium diboride has been given special attention due to its...

We report Ti concentration measurements in dilute Al-Ti alloys, acquired from direct analysis of the molten metal by laser-induced breakdown spectroscopy (LIBS). The LIBS analysis showed approximately constant Ti concentrations at melt temperatures above the liquidus, while at lower temperatures the measured concentration followed the L/(L + Al3Ti)...

Surface coatings can enhance the substrate material’s properties and increase its lifetime. HEA-based materials have been extensively investigated as coating materials due to their superior hardness, excellent oxidation and corrosion resistance, effective diffusion barrier properties and wear resistance. Magnetron sputtering has been regarded as on...

Aluminum smelters produce pure aluminum in reduction cells by the Hall-Héroult process but supply a variety of alloys to their customers. The alloys are produced in the cast house, as master alloys containing the desired alloying elements are added to the primary aluminum from the potroom before casting. In this work, the concept of producing silic...

Aluminum smelters produce pure aluminum in reduction cells by the Hall-Héroult process, however, aluminum is usually supplied as a variety of alloys to their customers. The alloys are produced in the casthouse, as desired alloying elements are added to the primary aluminum from the potroom before casting. In this work the concept of producing titan...

Although modern aluminium smelters using 100% green electrical energy generation can achieve on-site emissions of about 2 kg CO2 equivalents per tonne of aluminium produced (t CO2e/t Al), the total global average emissions from primary aluminium production from bauxite mine-to-metal ingot are much larger, about 16.5 t CO2e/t Al. Two thirds of the t...

Optimal current paths through the silicon furnace depend on the electrical properties of the charge materials. It is essential for good tapping conditions that sufficient current is supplied to the arc and lower part of the furnace. As such, the electrical resistivity of the charge mix as it is transformed in the furnace is investigated. Various ca...

This work presents a computational study to understand different heat transfer and phase transition processes of two-phase flow in a geothermal wellbore. The simulation uses a six-equation model with mass, momentum, and energy balance equations for the liquid and vapour phase, which is available in Ansys Fluent. The model considers the effect of ph...

Improved value generation and efficient use of resources are important steps national economies can implement to minimize the use of resources and mitigate the creation of waste and toxic emissions. The increase of resource efficiency is eminent to tackle the imminent challenges of depleting resources and the emerging environmental crisis. In this...

The world now pushes for a low-carbon future, and international goals for greenhouse gas emission reductions have been set. Industrial processes, including metallurgical processes, make up more than a fifth of the total global emissions, and those have been rising with infrastructure development and the expansion of the middle-class worldwide. This...

This work discusses the effect of electrode position on the electrical characteristics of a submerged arc furnace. A 3D model has been developed in ANSYS Maxwell using an eddy current solver that considers alternating current. The model includes flexibles, busbars, and the whole furnace. The furnace model contains electrodes, main arcs, craters, cr...

Direct production of aluminium-silicon alloy during aluminium electrolysis in fluoride-based melts was studied. Experiments were carried out in a laboratory cell dedicated to current efficiency measurements. Electrolysis was run at 960°C, 970°C, and 980°C at a fixed cathodic current density (CCD) of 0.9 A cm −2 and a cryolite ratio (CR) of 2.2. Sil...

Direct production of aluminium-silicon alloy during aluminium electrolysis in fluoride-based melts was studied. Experiments were carried out in a laboratory cell dedicated to current efficiency measurements. Electrolysis was run at 960 °C, 970 °C, and 980 °C at a fixed cathodic current density (CCD) of 0.9 A cm ⁻² and a cryolite ratio (CR) of 2.2....

This study reports the direct production of an aluminium−manganese alloy during aluminium electrolysis in fluoride-based melts. Experiments were conducted in a laboratory cell dedicated for current efficiency measurements. The temperature was varied from 965 to 980 ˚C at a cathodic current density (CCD) of 0.9 A/cm² and a cryolite ratio (CR) of 2.2...

This study reports the direct production of an aluminium–titanium alloy during aluminium electrolysis in fluoride-based melts. Experiments were conducted in a laboratory cell dedicated to current efficiency measurements. The temperature was varied from 960 to 980 ˚C at a cathodic current density (CCD) of 0.9 A/cm² and a cryolite ratio (CR) of 2.2....

In the aluminum electrolysis, the amount of carbon consumed per unit of metal produced is always higher than the theoretical one. Raw material variability, anode properties, and reduction cell operation and performance can influence this discrepancy. Linking these factors to each individual anode could help close this gap thus improving the environ...

The work presents computational modeling and an experimental investigation of silica deposition occurring in geothermal systems with superheated steam flows. An advection diffusion model was implemented for predicting silica particle transport and deposition in turbulent flows. The model includes the effect of Brownian diffusion, turbulent diffusio...

The paper describes a computational study and an experimental investigation of aqueous potassium carbonate droplets in superheated steam flow for potential applications in mitigation of superheated geothermal steam. The computational model included the boiling point elevation due to the droplet salt concentration as well as other concentration-depe...

The current method of producing aluminium-titanium master alloys is via melt mixing of pure titanium metal with primary molten aluminium prior to casting[1].The energy consumption and the production cost could be significantly lowered by the viable method of an in-situ electrochemical reduction of titania in fluoride-based melts which has been a su...

This work discusses 3D models of current distribution in a three-phase submerged arc furnace that contains several components, such as electrodes, central arcs, craters, crater walls, and side arcs that connect electrodes and crater walls. A complete modeling approach requires time-dependent modeling of the AC electromagnetic fields and current dis...

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This paper addresses the global challenge of greenhouse gas emissions facing the aluminum industry. The demand, production and use of aluminum are increasing and so are the emissions. From bauxite mine to aluminum ingot, the total global average emissions vary somewhat in the literature, but most reported values are now between 12 and 17 metric ton...

A study on scrubbing of superheated steam containing silica impurities is performed using an aqueous potassium carbonate solution as a potential application in mitigation of superheated geothermal steam. An experimental setup aimed at testing a silica particle scrubbing technique was built. The setup consists of a superheated steam generating syste...

Most submerged arc furnaces used for the production of ferroalloys run on three-phase alternating current. This affects the electrical operation of the furnace and thus it is of interest to study alternating current distributions in the system. This work presents computations of alternating electric current distributions inside an industrial submer...

This thesis describes a study of the viability of using excess energy from the exhaust gases at the Alcoa Fjarðaál aluminium plant to provide residential heating and hot water for household use in Reyðarfjörður. The results of the study indicate that such a system would be technically viable as well as delivering social and environmental benefits t...

This work presents computations of electric current distributions inside an industrial submerged arc furnace. A 3D model has been developed in ANSYS Fluent that solves Maxwell’s equations based on scalar and vector potentials approach that are treated as transport equations. In this paper, the approach is described in detail and numerical simulatio...

This work presents computations of electrical current distribution inside an industrial submerged arc furnace for silicon production. A 3D model has been developed in ANSYS Fluent using an electrical potential solver. The electrode, arc, crater, crater wall, and side arcs that connect the electrode and crater wall are considered for each phase. The...

Current distribution is critical for good operation of Submerged Arc Furnaces for silicon production. Control systems do not offer this information as it is not directly measureable, but metallurgists operate furnaces based on experienced interpretation of available data. A number of recent dig-outs of industrial furnaces has expanded available inf...

Around half of the energy consumed in aluminum production is lost as waste heat. Approximately 30–45% of the total waste heat is carried away by the exhaust gas from the smelter and is the most easily accessible waste heat stream. Alcoa Fjarðaál in east Iceland produces 350 000 tons annually, emitting the 110 °C exhaust gas with 88.1 MW of heat, wh...

Many factors may contribute to loss of current efficiency (CE) in aluminum reduction and one of them is a presence of impurities. In this work, the effect of phosphorus on CE is studied in a laboratory cell at different current densities. Due to a growing trend toward higher amperage in retrofitted industrial cells, a study is performed both at a r...

In the Hall-Héroult process, sulfur impurities may not only emit harmful gases but also reduce current efficiency. To better understand this process, the behaviour of sulfur compounds in a cryolite-alumina melt at 1253 K (980 °C) was investigated in a laboratory cell. Sodium sulfate (Na2SO4) was added into the molten bath as a sulfur source. Furnac...

Anode impurities are the major source of sulfur in aluminum electrolysis. Sulfur in anodes is mainly found as organic compounds. Alumina also introduces small quantities of sulfur, typically in the form of sulfates. The scarcity and cost of low-sulfur raw materials and the possibility of sulfur removal from the cell by means of flue gas may make hi...

In the Hall-Héroult process, sulfur impurities may not only emit harmful gases but also reduce current efficiency. To better understand this process, the behaviour of sulfur compounds in a cryolite-alumina melt at 1253 K (980 °C) was investigated in a laboratory cell. Sodium sulfate (Na2SO4) was added into the molten bath as a sulfur source. Furnac...

The current efficiency in industrial Hall-Heroult cells for aluminum production may be up to 96%. [1]. The back reaction between the dissolved metals (aluminum and sodium) and the anode product play the major part in the loss in current efficiency. Also impurities, such as phosphorous, which participate in cyclic red/ox reactions at the electrodes...

The study of the behavior of sulfur compounds in the Hall-Heroult process is of particular interest not only due to the emitted harmful gases, but also its potential effect on the process of aluminum production. The source of sulfurous gases from aluminum smelters is mainly the carbon anodes, which contain sulfur in organic sulfur ring structures....

Sulfurous gases are known for their detrimental effect on local air pollution (particulate matter), acid rain, health and global climate change. Sulfur emissions from an aluminum smelter with an annual production of 200000 tonnes can be as high as 1000 tonnes sulfur per year. The most important reported sulfurous gases from aluminum reduction cells...

Laboratory experiments were made where two phase mixture of flashed geothermal brine was injected into a tube filled with porous material. Direct measurements of pressure gradient and mass flow were made and used for calculating the relative permeabilities of the two phases. The results were compared with relative permeabilities calculated from fie...

Relative permeabilities of water and steam were calculated, by applying the Shinohara method, using data from geothermal wells in Iceland. This method does not require that the local water saturation of the two phase mixture is known, but requires production history of mass flow and enthalpy from each well. The results were compared to relative per...

Impurities in the electrolyte of an aluminum reduction cell are known to affect current efficiency and other aspects of potroom operation. Traces of phosphorus and sulfur are generally present in the cells and their behavior is of interest due to their known adverse effect on the process of aluminum production In this study, data analysis was perfo...

Measurements of two phase flow of water and steam in porous media were performed and relative permeabilities calculated. The goal was to compare the relative permeabilities from measurements using fluid of geothermal origin to known relative permeability curves, and to examine the effect of parameter variations. Due to high sensitivity to intrinsic...

Impurities in the electrolyte of an aluminum reduction cell are known to affect current efficiency and other aspects of potroom operation. Traces of phosphorus and sulfur are generally present in the cells and their behavior is of interest due to their known adverse effect on the process of aluminum production In this study, data analysis was perfo...

Current efficiencies for aluminium in the range from ∼ 93 - 96% were obtained by constant current electrolysis in a laboratory cell. The current efficiency was found to increase slightly by increasing cathodic current density. Additions of AlPO4 were found to lower the current efficiency of about 0.75 % per 100 ppm of phosphorus in the electrolyte,...

Effect of phosphorus on current efficiency for aluminum deposition was measured in a laboratory cell with current densities of 0.8 and 1.5 A/cm2. Controlled amounts of AlPO4 were added to the bath at the beginning of the experiment, and the effect on the current efficiency was studied at current densities of 0.8 A/cm2 and 1.5 A/cm2. Phosphorus leve...

The lithium-ion battery is one of the most promising technologies for energy storage in many recent and emerging applications. However, the cost of lithium-ion batteries limits their penetration in the public market. Energy input is a significant cost driver for lithium batteries due to both the electrical and thermal energy required in the product...

Effect of phosphorus on current efficiency for aluminum deposition was measured in a laboratory cell with current densities of 0.8 and 1.5 A/cm2. Controlled amounts of AlPO4 were added to the bath at the beginning of the experiment, and the effect on the current efficiency was studied at current densities of 0.8 A/cm2 and 1.5 A/cm2. Phosphorus leve...

Almost all ferroalloys are produced by smelting in submerged arc furnaces, powered by either AC or DC sources. To understand the smelting process and furnace operations, it is important to manage the theory of electrical circuits, efficiently apply and control active and reactive parts of the system, optimize the power factor and the operation of t...

Hot spas and jacuzzis are popular in Iceland due to the abundance of reasonably prized geothermal heat available. However the water from the DH (district heating) system is too warm to be admitted directly into the spa. For safety reasons the water is mixed with cold water, from 75 °C down to 50 °C, which leads to wasting a large quantity of heat....

The current efficiency in industrial Hall-Heroult cells for aluminum production may be up to 96%. [1]. The back reaction between the dissolved metals (aluminum and sodium) and the anode product play the major part in the loss in current efficiency. Also impurities, such as phosphorous, which participate in cyclic red/ox reactions at the electrodes...

When a dry steam containing volatile chloride cools to saturation temperature, the compound dissolves in the condensate and forms hydrochloric acid. This can have tremendous consequences for equipment as hydrochloric acid aggressively attacks steel and other metals, causing severe pitting corrosion, crystalline corrosion and stress corrosion cracki...

The Sabalan geothermal field in northwest Iran is currently under development. A single flash cycle has been selected for power generation. The analysis of the proposed design shows the maximum net power output of the plant can reach 31 MW if the pressures of the separator and condenser are 5.5 and 0.3 bar, respectively. To achieve optimum energy u...

pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2012/Sigurdsson.pdf‎ An experimental apparatus has been built to measure the relative permeability of water and steam in a two phase flow through porous rock for a range of flow configurations and conditions. In the experiment, the pressure gradient will be measured and consequently the relative permeabi...