Electrode Technology for Aluminum Production: Anode Raw Materials
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Roy Cahill, Rio Tinto; Stephan Broek, Kensington Technology Inc

Monday 2:00 PM
March 20, 2023
Room: 31A
Location: SDCC

Session Chair: Barbara Cramer, BP

2:00 PM
Partial Replacement of Coke with Biocoke: Effect of Biocoke Production Temperature on Anode Quality: Belkacem Amara¹; Duygu Kocaefe¹; Yasar Kocaefe¹; Jules Côté²; André Gilbert³; ¹University of Quebec at Chicoutimi; ²Aluminerie Alouette; ³Boisaco Inc.
    Carbon anodes used in aluminum electrolysis are composed of petroleum coke, coal tar pitch, recycled anodes, and butts. In order to reduce emissions of greenhouse gases (GHG), a group of researchers succeeded to replace a part of petroleum coke with biocoke modified using additives. Biocoke is obtained by the pyrolysis of wood chips at about 1100 şC, which is similar to the maximum temperature reached during anode baking. The focus of this study is the effect of biocoke production temperature on the anode quality. In this study, biocoke was produced at four different temperatures (600 şC, 750 şC, 950 şC, and 1100 şC). Anodes were produced without biocoke (standard anode) as well as with modified and non-modified biocokes. Then, the anodes were characterized by measuring their densities, electrical resistivities, air and CO2 reactivities, and bending strengths. The effect of biocoke production temperature was determined by comparing the anode properties.

2:25 PM
Method for Calcined Petroleum Coke Evaluation to Improve the Anode Quality: Sheetal Gupta¹; Suwarna Mahajan¹; Amit Gupta¹; Vilas Tathavadkar¹; ¹Aditya Birla Science & Technology Company, Ltd
    Worldwide, the quality of petroleum coke, used for making carbon anode for aluminium smelters, is getting degraded with increase in impurities and higher presence of shot coke particles. Earlier studies reported that some of the anode problems like slabbing and vertical cracking are linked to thermal shock resistant of coke material, which is majorly influenced by the structure of calcined petroleum coke (CPC). Therefore, a detailed method of optical microscopic analysis established and successfully applied to evaluate CPC materials. The analysis of most of the samples, were found to have presence of mixed and isotropic structure. The findings of the optical microscopy have been corelated with the visual identification of shot, sponge & needle coke. The visual identification of different coke particles enables its integration with digital image processing techniques for ease of quantification of specific coke material.

2:50 PM
Influence of Crusher Type and Particle Shape on the Bulk Density of Blended Shaft and Hearth Calcined Anode Grade Petroleum Coke: Howard Childs¹; Barry Sadler²; Mike Davidson¹; ¹BP; ²Net Carbon Consulting Pty Ltd
    The bulk density of anode grade petroleum coke is an important property for aluminum smelting and has been extensively studied. This includes previous work by BP showing that particle shape was modified by different crushing technologies, and that changes in shape (i.e. sphericity and convexity) influenced coke bulk density. These laboratory studies indicated that the impact of particle shape on the Vibrated Bulk Density (VBD) of a range of cokes and butts was of similar magnitude to that of porosity. In ongoing Customer support efforts, this work has been extended to study whether modifying particle shape can improve the VBD of blends of cokes calcined using different technologies – shaft and rotary hearth kilns. The results of this study are presented and the potential to enhance the VBD of shaft/non-shaft calcined coke blends by modifying particle shape with different crusher types determined at a laboratory scale.

3:15 PM
Managing Green Petroleum Coke Properties Variations on Prebaked Anodes Quality in Aluminium Bahrain “Alba”: Hesham Hassan Buhazza¹; Vasantha Kumar Rangasamy¹; Nabeel Ebrahim Mohd Al Jallabi¹; Taleb Al Ansari¹; Abdulmohsin Hasan Radhi¹; Francois Morales²; Abdulla Habib Ahmed Ali¹; ¹Aluminium Bahrain B.S.C. (Alba); ²SCCR Consultant
    ALBA (Aluminium Bahrain) is one of unique primary Aluminium smelters who has its own calciner plant to produce CPC, by converting different types of GPC to CPC. The quality of GPC has a strong influence on the properties of the anodes. Due to market variations and price fluctuation, the properties of GPC purchased vary depending on the source. In addition, with latest expansion of Alba being the largest smelters outside China, Alba has to purchase ready CPC to top up the shortage in Calciner capacity. Such changes bring up great challenges to both Calciner and Carbon operation team to manage these variations through precise blending and tuning process parameters to achieve optimum anodes quality. This paper discusses ALBA strategy on managing the variations of GPC properties along with purchased CPC on quality of anodes in terms of desulphurization, anode density, baking level, stack emissions and other anode properties.

3:40 PM Break

3:55 PM
New Methods to Determine PAH Emission Dynamics during Electrode Mass Processing: Ole Kjos¹; Thor Aarhaug¹; Heiko Gaertner¹; Bente Hĺland²; Jens Christian Fjelldal²; Katarina Jakovljevic³; Oscar Espeland⁴; Ida Kero¹; ¹Sintef As; ²Elkem Carbon; ³Norwegian university of science and technology (NTNU); ⁴Nemko Norlab
    New measurement techniques aiming to improve the understanding of PAH emissions dynamics during production of electrode mass briquettes from anthracite (coke) and pitch was tested. Traditional sampling requires hours of sampling to get enough PAH on the adsorbent material to perform reliable analysis. As the process parameters can be changing from one batch to the next, emissions cannot be expected to be constant over time. Better time resolution is essential to increase the understanding of emission variations. Thermal desorption tubes allows for sampling times as short as 10 minutes, and the use of SINTSENSE, a standalone photoionization detector (PID) implementation for emission monitoring. It gives online data second by second, however the SINTSENSE will report a total hydrocarbon estimate, with no differentiation between individual components. Comparing results from these 3 methodologies gives insight in the emission dynamics and variations in composition, in addition to benchmarking of the individual measurement techniques.