Aluminium Recycling in Single- and Multiple-Capillary Laboratory Electrolysis Cells

This work is a contribution to the approach for Al purification and extraction from scrap using the thin-layer multiple-capillary molten salt electrochemical system. The single- and multiple-capillary cells were designed and used to study the kinetics of aluminium reduction in LiF–AlF3 and equimolar NaCl–KCl with 10 wt.% AlF3 addition at 720–850 °C. The cathodic process on the vertical liquid aluminium electrode in NaCl–KCl (+10 wt.% AlF3) in the 2.5 mm length capillary had mixed kinetics with signs of both diffusion and chemical reaction control. The apparent mass transport coefficient changed from 5.6∙10−3 cm.s−1 to 13.1∙10−3 cm.s−1 in the mentioned temperature range. The dependence between the mass transport coefficient and temperature follows an Arrhenius-type behaviour with an activation energy equal to 60.5 kJ.mol−1. In the multiple-capillary laboratory electrolysis cell, galvanostatic electrolysis in a 64LiF–36AlF3 melt showed that the electrochemical refinery can be performed at a current density of 1 A.cm−2 or higher with a total voltage drop of around 2.0 V and specific energy consumption of about 6–7 kWh.kg−1. The resistance fluctuated between 0.9 and 1.4 Ω during the electrolysis depending on the current density. Thin-layer aluminium recycling and refinery seems to be a promising approach capable of producing high-purity aluminium with low specific energy consumption

Investigation of Bubble Behaviour at Cryolite Melt – Alumina Slurry Electrolysis

В статье представлены результаты физического моделирования движения, роста и удаления пузырей кислорода, образуемых в результате электрохимического выделения на инертном аноде при электролизе суспензии криолитовый расплав – глинозем. Рассчитаны критерии подобия, проведены опыты на ячейках двух типов: для наблюдения за трехфазным слоем спереди от вертикального электрода и сбоку от него. С помощью видеосъемки получены данные о поведении пузырей в суспензии. В качестве электролита модели использовался 20%-ный водный раствор серной кислоты с содержанием глинозема 30 % об. Опыты проводили в интервале плотностей тока от 0,05 до 0,25 А/см2. Сведения о поведении трехфазного потока позволяют оценить возможность эффективной эвакуации газа из межэлектродного пространства при электролизе суспензии. Наибольшая скорость (2,5 см/с) достигается пузырями на глубине от 15 до 20 мм от границы электролит – воздух, после чего скорость снижается. Толщина пузырькового слоя не превышает 2,2 мм. Средняя скорость роста пузыря составила 2,68 мм3/сPhysical modeling of oxygen bubbles generated on the inert anode as a result of electrochemical evolution at cryolite melt – alumina slurry electrolysis movement, growth and evacuation results are presented in the paper. Similarity criteria are calculated, experiments are performed on two types of cell: for three phase flow at vertical electrode observation from front and side views. The behaviour of bubbles in slurry was recorded. For the model, an 20 % aqueous solution of sulfuric acid with 30 vol. % of alumina was used. Current density range was 0.05 to 0.25 A/cm2. Bubble behavior information allows estimating the ability of effective gas evacuation from the inter-electrode space during slurry electrolysis. The highest bubbles vertical speed (2.5 cm/s) was reached at 15 to 20 cm depth from the electrolyte – atmosphere border, after which the speed was reduced. Bubble layer thickness does not exceed 2.2 mm. Bubble’s average growth rate was 2.68 mm3/

Anode overvoltages on the industrial carbon blocks

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала

Investigation of Bubble Behaviour at Cryolite Melt – Alumina Slurry Electrolysis

В статье представлены результаты физического моделирования движения, роста и удаления пузырей кислорода, образуемых в результате электрохимического выделения на инертном аноде при электролизе суспензии криолитовый расплав – глинозем. Рассчитаны критерии подобия, проведены опыты на ячейках двух типов: для наблюдения за трехфазным слоем спереди от вертикального электрода и сбоку от него. С помощью видеосъемки получены данные о поведении пузырей в суспензии. В качестве электролита модели использовался 20%-ный водный раствор серной кислоты с содержанием глинозема 30 % об. Опыты проводили в интервале плотностей тока от 0,05 до 0,25 А/см2. Сведения о поведении трехфазного потока позволяют оценить возможность эффективной эвакуации газа из межэлектродного пространства при электролизе суспензии. Наибольшая скорость (2,5 см/с) достигается пузырями на глубине от 15 до 20 мм от границы электролит – воздух, после чего скорость снижается. Толщина пузырькового слоя не превышает 2,2 мм. Средняя скорость роста пузыря составила 2,68 мм3/сPhysical modeling of oxygen bubbles generated on the inert anode as a result of electrochemical evolution at cryolite melt – alumina slurry electrolysis movement, growth and evacuation results are presented in the paper. Similarity criteria are calculated, experiments are performed on two types of cell: for three phase flow at vertical electrode observation from front and side views. The behaviour of bubbles in slurry was recorded. For the model, an 20 % aqueous solution of sulfuric acid with 30 vol. % of alumina was used. Current density range was 0.05 to 0.25 A/cm2. Bubble behavior information allows estimating the ability of effective gas evacuation from the inter-electrode space during slurry electrolysis. The highest bubbles vertical speed (2.5 cm/s) was reached at 15 to 20 cm depth from the electrolyte – atmosphere border, after which the speed was reduced. Bubble layer thickness does not exceed 2.2 mm. Bubble’s average growth rate was 2.68 mm3/

Potassium Balance and Its Distribution in Commercial Aluminum Reduction Cells—When Potassium-containing Alumina Is Used as the Raw Material for Aluminum Electrolysis

China is short of high grade bauxite for the production of smelting grade alumina. With the massive exploitation of potassium containing bauxite in China, the produced Bayer alumina contains a non-negligible content of potassium oxide. When this kinde of alumina is used as the raw material for aluminum electrolysis, the potassium would cause multiple effects to the cell performance. In this paper, the potassium concentrations of fresh alumina, secondary alumina, aluminum fluoride, anode, electrolyte, anode cover, cathode block, carbon lining, silicon carbide block and product aluminum et al. in 160 kA and 200 kA prebaked aluminum reduction cells were tested and a potassium balance model was preliminarily given. Initial results showed that most of the potassium was brought into the cell by the potassium containing impurities in the fresh alumina. The only effective way for potassium removal from the cell was through the carbon residue though nearly 80 wt% of the potassium would stay and enrich in different positions of the cell

Transfer Processes in the Bath of High Amperage Aluminium Reduction Cell

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала

Construction of a Compact and High-Precision Classifier in the Inductive Learning Method for Prediction and Diagnostic Problems

The study is dictated by the need to make reasonable decisions in the classification of observations, for example, in the problems of medical prediction and diagnostics. Today, as part of the digitalization in healthcare, decision-making by a doctor is carried out using intelligent information systems. The introduction of such systems contributes to the implementation of policies aimed at ensuring sustainable development in the health sector. The paper discusses the method of inductive learning, which can be the algorithmic basis of such systems. In order to build a compact and high-precision classifier for the studied method, it is necessary to obtain a set of informative patterns and to create a method for building a classifier with high generalizing ability from this set of patterns. Three optimization models for the building of informative patterns have been developed, which are based on different concepts. Additionally, two algorithmic procedures have been developed that are used to obtain a compact and high-precision classifier. Experimental studies were carried out on the problems of medical prediction and diagnostics, aimed at finding the best optimization model for the building of informative pattern and at proving the effectiveness of the developed algorithmic procedures

Anode Processes Malfunctions Causes. An Overview

Одним из наиболее типичных видов технологических расстройств в анодах после их установки в электролизер является неравномерное изменение рельефа подошвы анода и образование на ней выступов, называемых в зарубежной технической литературе шипами, грибами, деформациями, в российской – конусами. Конусы могут вызвать короткое замыкание анода и катода, увеличить флуктуации тока, выход угольной пены, уровень шумов. Другой вид технологических расстройств в анодах – образование в них трещин вследствие теплового удара (термошока), который испытывает холодный анод при установке в расплав. Образовавшиеся в результате растрескивания куски анода попадают в электролит, нарушая технологический режим электролизера, увеличивая расход углерода и существенно осложняя обслуживание электролизера. Одна из основных опасностей образования конусов и растрескивания анода – значительное снижение выхода по току и технико-экономических показателей производства алюминия. В настоящей статье представлен обзор исследований российских и зарубежных экспериментаторов, посвященных изучению причин технологических расстройств в анодахOne of the most common anodes malfunctions appearing after its set up is uneven anode’s profile relief modification and protrusion formation, called “spikes”, “mushrooms” “deformations” and “cones”. Spikes can provide short circuits between anode and cathode, increase current fluctuations, carbon dust volume and noise. Another kind of anodes malfunctions is cracking due to thermal shock, which strikes “cold” anode during its setup. Pieces, formed as a result, fall into bath, make a technological malfunction, increase carbon consumption and make cell operating more difficult. One of the dangers of spikes formation is decrease of current efficiency and aluminium production economical and technical indices. An overview of Russian and foreign author’s anodes malfunctions causes researches are presented in the pape

Towards Understanding the Cathode Process Mechanism and Kinetics in Molten LiF–AlF3 during the Treatment of Spent Pt/Al2O3 Catalysts

Electrochemical decomposition of spent catalyst dissolved in molten salts is a promising approach for the extraction of precious metals from them. This article reports the results of the study of aluminum electrowinning from the xLiF–(1-x)AlF3 melt (x = 0.64; 0.85) containing 0–5 wt.% of spent petroleum Pt/γ-Al2O3 catalyst on a tungsten electrode at 740–800 °C through cyclic voltammetry and chronoamperometry. The results evidence that the aluminum reduction in the LiF–AlF3 melts is a diffusion-controlled two-step process. Both one-electron and two-electron steps occur simultaneously at close (or same) potentials, which affect the cyclic voltammograms. The diffusion coefficients of electroactive species for the one-electron process were (2.20–6.50)∙10−6 cm2·s–1, and for the two-electron process, they were (0.15–2.20)−6 cm2·s−1. The numbers of electrons found from the chronoamperometry data were in the range from 1.06 to 1.90, indicating the variations of the partial current densities of the one- and two-electron processes. The 64LiF–36AlF3 melt with about 2.5 wt.% of the spent catalysts seems a better electrolyte for the catalyst treatment in terms of cathodic process and alumina solubility, and the range of temperatures from 780 to 800 °C is applicable. The mechanism of aluminum reduction from the studied melts seems complicated and deserves further study to find the optimal process parameters for aluminum reduction during the spent catalyst treatment and the primary metal production as well

Инертные аноды в алюминиевой промышленности: обзор

The paper is a review of the advancements achieved towards the research work done towards inert anodes for aluminium reduction cell. The research work dedicated towards inert anodes has been for more than a century, but significant advancement was made only a few decades ago. The aim of the researchers was to find the anode which shows excellent electrical conductivity and highly resistant towards corrosion with longer anodic lifetime but this is highly difficult to achieve. This article reviews the research work done on: (1) Ceramics, which are oxides of Ni, Sn, Fe, and Cu which can be one or a combination of oxides e.g. NiO – Li2O (2) Metals, in pure or alloy form (3) Cermets, oxides in combination with the metals. Some results obtained in laboratory scale cells were highly liable and gave a scope to try them on industrial cellsВ статье представлен обзор достижений в разработке инертного анода для алюминиевого электролизера. Исследования, посвященные инертным анодам, проводятся более века, но значительные успехи достигнуты всего несколько десятилетий назад. Целью исследователей была разработка анода с высокими электропроводностью и коррозионной устойчивостью во фторидных расплавах, чего на практике весьма трудно достичь. В этой статье рассмотрены исследования, проведенные на: (1) керамических анодах, содержащих оксиды металлов Ni, Sn, Fe и Cu или их комбинации, например, NiO-Li2O; (2) металлах и сплавах (3) керметах, т.е. оксидно- металлических композициях. Некоторые результаты, полученные в лабораторных ячейках, были обнадеживающими и дали возможность проведения промышленных испытани