Aluminum Reduction Technology: Environment
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Jayson Tessier, Alcoa Corporation
Thursday 8:30 AM
February 27, 2020
Room: 6D
Location: San Diego Convention Ctr
Session Chair: David Wong, Light Metals Research Centre
8:30 AM Introductory Comments
8:35 AM
Reducing the Carbon Footprint: Aluminum Smelting with Changing Energy Systems and the Risk of Carbon Leakage: Gudrun Saevarsdottir1; Halvor Kvande2; Barry Welch3; 1Reykjavik University; 2Consultant; 3The University of Auckland
The world is now pushing for a low-carbon future. Presently, 70% of aluminum is produced with power from fossil-fuelled power plants, and while the introduction of solar and wind generation is accelerating, this has technical constraints and limitations. Gradually de-carbonizing energy production is the most effective way for the primary aluminum industry to reduce emissions. Globally the best result will be achieved by maximizing aluminum production in regions that can provide clean green power, while simultaneously operating at minimum unit energy consumption rate for the technologies using fossil fuel based power. Closing down hydro powered smelters to reduce national emissions risks carbon leakage, because growing metal demand is primarily met with increased production capacity in countries using non-renewable high emission level power sources. This paper opens debate on the possibilities for reducing CO2 emissions in light of our global responsibility.
8:55 AM
Measurement System for Fugitive Emissions in Primary Aluminium Electrolysis: Håkon Myklebust1; Thor Anders Aarhaug2; Gabriella Tranell1; 1Norwegian University of Science & Technology; 2SINTEF
Fugitive emissions from primary aluminium production is a concern both for occupational health and the environment. Current measuring equipment for in-situ measurements of such emissions is generally large and expensive or lacks the required time and spatial resolution to provide accurate information on the source of the emissions. This research is aimed at testing and evaluating distributed micro sensors for in-situ monitoring of dust intensity in the electrolysis hall. Multiple sensors are tested simultaneously in clusters at each location to study variation between individual sensors, giving a statistical average. These clusters are spread out in the relevant areas to map how the emission varies over both time and location based on operational activities such as anode changes. The sensor system yielded results that could be correlated to the process activities, and also showed clear variation in the fractions of PM10 and PM2.5 measured for different process operations.
9:15 AM
Validation of QCL CF4 Gas Analyzer for Sensitivity and Selectivity: Thor Anders Aarhaug1; 1SINTEF
Quantum cascade lasers render the mid-IR spectral range available for laser gas monitors. For PFC's, continuous emission monitors are now commercially available. Since these instruments can only make use of a narrow band, spectral interference from other gas species is not easily resolved. In this paper a commercial QCL CF4 analyser is validated with respect to sensitivity and selectivity. In the laboratory, the laser was mounted on a 0.3 meter measurement cell. A gas mixer provided humidified gas mixtures of CF4 and methane. The results indicated that while there were no interference from water in the range up to 8000 ppm mol, a small interference from methane was observed. This was quantified to be approximately 3 ppb mol CF4 per ppm mol of methane. The sensitivty of the instrument was found to be 15 ppb mol CF4 for one meter light path.
9:35 AM
A Laboratory Study of the HF Generation Potential of Particulate Fluorides from Cell Emissions: Jenny Hung1; James Metson2; 1Light Metals Research Centre; 2School of Chemical Sciences, University of Auckland
The injection type dry scrubber is the most commonly used technology in the aluminium smelting industry to manage HF emissions. One limitation of this technology is its sensitivity to temperature and humidity. Previous studies of smelter operation data and experimental work have demonstrated a clear link between the increase in temperature and/or humidity and increase in HF concentration in the treated off-gas. In this study, the generation of gaseous HF through a hydrolysis reaction between gas stream humidity and particulate fluorides has been tested under controlled laboratory conditions. The aim is to identify the HF generation potential of various particulate fluoride phases from cell emissions, and to understand the effect of temperature and humidity on the main reactive fluoride material(s). A range of particulate fluorides were tested, including purchased high purity fluorides and laboratory generated materials such as crushed bath and condensed fume. Results to date show the most significant HF generation bath phase to be the condensed fume phase NaAlF4. However, two ferrous fluoride phases which were minor impurities in the lab generated fume were also found to be significant HF generation contributors.
9:55 AM
Method Development to Estimate Total Low Voltage and High Voltage PFC Emissions: Luis Espinoza-Nava1; Christine Dubois2; Eliezer Batista1; 1Alcoa Technical Center; 2Alcoa Deschambault
Perfluorocarbons (PFC) emissions must be reported as accurately as possible. The aluminum industry is using consistent method to estimate high voltage PFC emissions. However, a new or improved method is needed to account for low voltage PFC emissions. Thus, equipment and time frequency must be revised to estimate both high and low voltage emissions during not only anode effects above 8 volts but also during pot disturbances that affect pot noise and therefore can make the contribution of low voltage emissions significant higher. Preliminary results showing the variability of low voltage and estimation of total PFC emissions is presented from recent PFC measurement campaigns at Alcoa smelters.
10:15 AM Break
10:30 AM
Update on SO2 Scrubbing Applied in Primary Aluminium Smelters: Stephan Broek1; 1Hatch Ltd.
There is an increasing interest in the abatement of SO2 from primary aluminium smelters. A first paper was published in 2009 at the TMS conference and in this paper an update is provided with new details, practices and technologies for the control of SO2 emissions in smelters. The paper discuses a sulfur balance, current practices and trends all related to emission of SO2.
10:50 AM
Optimization of a Gas Treatment Center Equipped with Extended Surface Bag Filters: Julie Dontigny1; Stephan Broek1; Mario Dion2; Raymond Emond2; Philippe Martineau3; 1Hatch Ltd.; 2Rio Tinto; 3Fives Solios
Primary aluminum industry is facing the modern challenge of improving environmental footprint while increasing at the same time the overall metal production. Part of this challenge can be overcome by developing a good knowledge of technologies to optimize their performances. In that context, testwork was conducted in 2017 and 2018 on the Gas Treatment Center installed at the Rio Tinto AP60 Technology Center located in Canada. The AP60 GTC was originally supplied with standard filter bags except for one filtration module equipped with extended surface filter bags. This was part of the R&D vocation of the smelter. Back in 2017, the original bags were approaching the end of their useful life. The purpose of the testwork was to acquire a deep understanding about control of process parameters to optimize the GTC performances if ESB filters would be installed in all filtration modules. In this paper the testwork results are discussed.
11:10 AM
Update on the Abart Gas Treatment and Alumina Handling at the Karmøy Technology Pilot: Anders Sorhuus1; Sivert Ose1; Eivind Holmefjord1; Håvard Olsen1; Bent Nilsen1; 1GE Power
During spring of 2018 Hydro started up the new ambitious Karmøy Technology Pilot (KTP) with the aim to achieve significant step changes in the specific energy consumption and at the same time define new industry standards in environmental impacts to the atmosphere. These goals will require energy improvements and updated improved abatement solutions for of all aspects of the production including; a fully integrated updated Abart gas treatment center with dual duct systems for forced suction, anode cooling box suction, new integrated heat exchangers, the Alfeed alumina distribution, fluoride transport, and crushed bath mixing and transport.The expected “Improvements on the Abart Gas Treatment and Alumina Handling at the Karmøy Technology Pilot” was presented at TMS 2018. This paper will review the final results and experiences after reaching stable operation with even lower emissions than targeted.