Aluminum Industry Emissions Measurement, Reporting & Reduction: Aluminum Industry Emissions Measurement, Reporting & Reduction
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Pernelle Nunez, International Aluminium Institute
Tuesday 2:30 PM
March 21, 2023
Room: 31A
Location: SDCC
Session Chair: Marlen Bertram, International Aluminium Institute
2:30 PM Introductory Comments
2:35 PM
Reaching Zero Carbon Emissions in Aluminium Electrolysis: Gudrun Saevarsdottir1; Sai Krishna Padamata1; Brandon Velasquez1; Halvor Kvande2; 1Reykjavik University; 2Previously NTNU
The global community has set a goal of carbon neutrality by 2050. The almost one fourth of global emissions, attributed to direct emissions from industrial processes, must be addressed by developing zero-carbon alternatives for each process, including the production of aluminium. Several companies and research institutions are working on aluminium electrolysis using oxygen evolving inert anodes, recent developments having been quite promising. For existing smelters, carbon capture and sequestration may become a realistic alternative, depending upon successful adaptation of the flue-gas system enabling up-concentration of CO2 in the flue gas. A third alternative is the electrolysis of aluminium chloride, keeping chlorine and carbon in separate recycling loops. This paper gives a review of the efforts to date, from industry and academia, to decarbonise the electrolysis of aluminium. The development of the largest part of the carbon footprint, arising from the production of the electrical energy used, is also discussed.
3:00 PM
Individual Pot Sampling for Low-voltage PFC Emissions Characterization and Reduction: Brian Zukas1; Julie Young1; 1Alcoa
PFC emissions from aluminum smelting are characterized by two mechanisms, high-voltage generation (HV-PFCs) and low-voltage generation (LV-PFCs). HV-PFCs are emissions produced when a cell is undergoing an anode effect, voltage >8V. Modern cell technology has enabled pre-bake smelters to achieve low anode effect rates and durations, thereby decreasing their HV-PFC emissions. LV-PFCs are the emissions produced when the cell voltage is below 8V. Lacking a clear process signal to act upon, LV-PFCs can be difficult to treat. To tackle this issue, Alcoa has conducted sampling on individual electrolysis cells, during which continuous process and emissions data, as well as periodic bath samples were collected. In the sampled cells, a variety of conditions were observed where LV-PFCs were generated. Understanding what was occurring at the cell level allowed for the identification of opportunities for process improvement, both for the reduction of LV-PFC emissions and cell performance.
3:25 PM
Determination of PFC with Canister Sampling and Medusa GC-MS Analysis in Comparison to General IPCC Estimation Methods: Henrik Aasheim1; Morten Isaksen1; Norbert Schmidbauer2; Ove Hermansen2; Chris Lunder2; 1Hydro Aluminium AS; 2Norwegian Institute for Air Research
Most aluminum smelters today report on their Perfluorocarbon (PFC) emissions by a method that is derived from the IPCC Guidelines for National Greenhouse Inventories of 2006 or 2019. Often the default industry emission factors have been employed (Tier 1/2), however, many companies are looking into acquiring plant specific factors (Tier 3). Hydro and Norwegian Institute for Air Research (NILU) have been testing a method of time-integrated air sampling where canisters are used to extract gas from different smelter locations that can later be measured by Medusa GC-MS. Sampling duration is determined by gas flow and canister size and the PFC detection limit is down to ambient air – making the method very applicable to low emitting smelters. Preliminary results from stack and roof sampling deviate from 2006 IPCC Tier 2 slope estimation, whereby the measurements, a total PFC method, show a CO2e reduction of almost 30% compared to the estimation.
3:50 PM Break
4:05 PM
Heavy Metal Emissions through Dust from Aluminium Electrolysis: Fride Muller1; Thor Anders Aarhaug2; Gabriella Tranell1; 1The Norwegian University of Science and Technology; 2SINTEF Industry
Heavy metals in airborne particulate matter (PM), is considered a health and environmental concern. A better understanding of the formation and characteristics of the dust is necessary to improve monitoring and control measures of these emissions. Both settled and collected airborne dust from Norwegian smelters were characterised by dry laser diffraction, SEM/TEM, XRD and ICP-MS. PM emissions (PM1.0, PM2.5, PM4.0 and PM10) were measured by optical PM sensors, mapping variations in fugitive emissions in different potroom areas. Heavy metals were often found as inclusions or on the surface of larger carbon particles in the dust. Nickel and iron were found as phosphorous or sulfur compounds. The particle size for settled and airborne dust were mainly in the PM10+ range, while the average particle size for particles measured by the sensor system were around 0.6 µm at roof and floor level. Anode change gave rise to higher emissions than other operations.
4:30 PM
Verification of Open-path Dust Laser for Continuous Monitoring of Diffuse Emissions: Lars Moen Strømsnes1; Heiko Gaertner2; Steinar Olsen3; Peter Geiser3; Bernd Wittgens2; 1SINTEF Helgeland; 2SINTEF AS; 3NEO Monitors AS
Stringent emissions requirements and a lack of standardized measurement methods urge the need for systematic development of reliable on-line monitoring systems for diffuse emissions. A new generation long path dust analyzer based on a divergent, modulated laser transmission technique is under development. The new instrument is currently tested in a wind tunnel designed by SINTEF and installed at a NTNU laboratory in Trondheim, Norway. This "One-of-its-kind" calibration system, and the features of the open-path instrument are outlined in this paper. Further, a pilot LaserDust™ instrument was installed on site at Elkem Rana, Norway to collect data for the development of the monitoring system. We present our experience related to emission monitoring, highlighting opportunities of reliable and reproducible online quantification for modern process control to reduce waste streams. Reference measurement sampling strategies and methods for calibration and verification tailored for open-path dust lasers are discussed.
4:55 PM
Characterization of Industrial Hydrocarbon Samples from Anode Baking Furnace Off-gas Treatment Facility: Kamilla Arnesen1; Alexandre Albinet2; Claudine Chatellier2; Nina Huynh2; Thor Aarhaug3; Kristian Einarsrud1; Gabriella Tranell1; 1Norwegian University of Science and Technology; 2National Institute for Industrial Environment and Risks (INERIS); 3SINTEF
Polycyclic aromatic hydrocarbons (PAHs) are naturally present in raw materials used to produced prebaked anodes for electrolysis of aluminum. Green anodes are baked to about 1200 °C over two – three weeks where organic hydrocarbon volatiles contribute to the carbonization process. Off-gases contain volatile and semi-volatile organic components, which are further treated to reduce environmental emissions by techniques such as regenerative thermal oxidizers and dry or wet scrubbers. Still, prebaked anode production contributes to a noticeable part of the reported PAH emissions in Norway. Samples of condensed matter have been collected from an off-gas treatment facility and the aromatic content have been characterized by various methods to investigate the presence of different categories of aromatic hydrocarbons and their properties to increase understanding of the processes occurring in the treatment facility.