Electrode Technology for Aluminum Production: Raw Materials
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Duygu Kocaefe, University of Quebec at Chicoutimi

Wednesday 2:00 PM
February 26, 2020
Room: 3
Location: San Diego Convention Ctr

Session Chair: Maia Hunt, Rain Carbon


2:00 PM Introductory Comments

2:10 PM  
Anhydrous Carbon Pellets – An Engineered CPC Raw Material: Les Edwards1; 1Rain Carbon Inc.
    The paper will report on a new technology Rain Carbon has been developing to produce an engineered calcined petroleum coke (CPC) product. Agglomeration of green petroleum coke (GPC) fines through either granulation/pelletizing or briquetting can be used to produce a CPC product with improved properties. Pelletizing GPC fines in particular, can produce high bulk density pellets hereafter referred to as anhydrous carbon pellets or ACP. ACP densifies when calcined to produce a high bulk density, free flowing CPC product. The spherical particle shape provides improved particle packing relative to irregularly shaped CPC during anode production. The paper will summarize key results including pilot anode properties showing improvements in baked anode density, electrical resistivity and other properties when using ACP. A key benefit of ACP is the ability to produce a fully engineered CPC product and Rain Carbon is currently working on building a full scale, commercial plant in the US.

2:35 PM  
Influence of Particle Shape and Porosity on the Bulk Density of Anode Grade Petroleum Coke: Frank Cannova1; Mike Davidson1; Barry Sadler2; 1BP; 2Net Carbon Consulting Pty Ltd
    Bulk density is a key property of anode grade petroleum cokes used in aluminum smelting and many studies have been undertaken on this parameter. These include previous work by BP that showed how particle shape could be modified by using different crushing technologies, and that changing shape parameters (i.e. sphericity and convexity) has a significant influence on coke bulk density. A single coke was used in this initial study to keep coke porosity relatively constant. This work has now been extended to include the testing of a number of different petroleum cokes (calcined using diverse calcining technologies) and anode butt samples to introduce variation in sample porosity as well as shape. The test results were used to develop a simple model of the factors that impact bulk density, and the comparative influence of particle shape and porosity on coke bulk density was determined.

3:00 PM  
An EXAFS and XANES Study of V, Ni, and Fe Speciation in Cokes for Anodes Used in Aluminum Production: Goril Jahrsengene1; Hannah Wells2; Camilla Sommerseth3; Arne Petter Ratvik3; Lorentz Petter Lossius4; Katie Sizeland5; Peter Kappen5; Ann Mari Svensson1; Richard Haverkamp2; 1Norwegian University of Science and Technology; 2Massey University - School of Engineering and Advanced Technology; 3SINTEF Industry; 4Hydro Aluminium AS, Primary Metal, Technology; 5ANSTO
    Lower quality petroleum coke with higher levels of sulfur and metal impurities will have to be used for the manufacturing of anodes for aluminum production in the future. Sulfur and metallic impurities affect the anode properties in the aluminum production process, but the chemical identity of the metal species in the coke is not known. In this work, industrial petroleum cokes with high sulfur levels were analysed by XANES and EXAFS in order to determine the identity of the V, Ni and Fe impurities. It was found that V is present mainly as hexagonal V3S4. Ni is present mainly as hexagonal NiS, and Fe is present as hexagonal FeS. This knowledge of the chemical state of the metal elements in coke, which are known to affect anode performance, is the first step in understanding the mechanism of the action of these elements on anode reactivity.

3:25 PM Break

3:45 PM  
Additive Selection for Coal Tar Pitch Modification in Aluminum Industry: Julie Bureau1; Armita Rastegari1; Duygu Kocaefe1; Yasar Kocaefe1; Hans Darmstadt2; 1University of Quebec at Chicoutimi; 2Rio Tinto
    In aluminium industry, the quality of anodes has a direct impact on the production cost, energy consumption, and environmental emissions. Properties of anodes are strongly affected by the quality of binding between coke and pitch. One of the most promising avenues to enhance this binding is the modification of pitch properties using additives. They help increase pitch surface functional groups and consequently improve coke-pitch interactions. The current work was undertaken to establish an additive selection method which would yield improved coke wettability by modified pitch. This article describes the method and presents the results for three different additives. Non-modified and modified pitches were characterized by carrying out wettability tests and FTIR analyses. Coking values (CV) of non-modified and modified pitches were also measured. The results show that it is possible to improve coke-pitch interactions via the utilization of additives.

4:10 PM  
Charcoal and Use of Green Binder for Use in Carbon Anodes in the Aluminium Industry: Camilla Sommerseth1; Ove Darell1; Barte Øye1; Anne Støre1; Stein Rørvik1; 1SINTEF Industry
    Carbon anodes for aluminium production are made of calcined petroleum coke (CPC) and coal tar pitch (CTP). The CO2 produced upon anode consumption contributes to a substantial amount of the carbon footprint. Charcoal from wood is suggested to partly replace coke in anodes but has some highly undesirable properties: low electrical resistivity, high porosity, and high ash content. Siberian larch and spruce charcoal were produced by heat treatment to 800°C, 1200°C and 1400°C and acid-washed with H2SO4, resulting in decreasing impurity content and porosity. Pilot anodes were made from CTP, CPC and charcoal, some with CTP replaced by a green binder. A reference anode was produced with CTP and CPC. Electrochemical consumption of anodes containing green binder, larch and spruce were all higher compared to the reference anode. CO2 reactivity was higher for anodes containing spruce and green binder, but comparable to the reference for anodes containing larch.