Improving current efficiency in low-temperature aluminum electrolysis with vertical inert electrodes
Bibliographic record
Abstract
Primary aluminum production is an energy intensive process with an average electric power consumption between 13 – 14 MWh per tonne of aluminum from the electrolysis process alone. Additional energy consumed in the aluminum plant is derived from the carbon anodes used in the process, equating to 3.8 MWh/t Al and contributing to 1.5 tonnes of carbon dioxide emissions for every tonne of aluminum produced. Most aluminum produced today is derived from non-renewable resources, with the aluminum industry emitting approximately 500 million tonnes of carbon dioxide equivalent annually; this constitutes about 1 % of the world’s total CO2 emissions. Countries like Iceland, Norway and Canada use hydroelectric and geothermal power for aluminum production so the only way to achieve substantial reduction in carbon dioxide emissions are to change the anode material. By replacing the carbon-based material with an inert material, oxygen, rather than carbon dioxide, is evolved as the main by-product. Potential materials for inert electrodes have a limited lifetime in the corrosive cryolite electrolyte at 960 °C. This drawback has led to significant research in altering electrolyte composition and lowering bath/electrolyte temperature to improve inert anode stability. The objective of this thesis was to investigate the influence that different operating parameters have on current efficiency in low temperature electrolysis with vertical inert electrodes. \n \nPrimary aluminum production is an energy intensive process with an average electric power consumption between 13 – 14 MWh per tonne of aluminum from the electrolysis process alone. Additional energy consumed in the aluminum plant is derived from the carbon anodes used in the process, equating to 3.8 MWh/t Al and contributing to 1.5 tonnes of carbon dioxide emissions for every tonne of aluminum produced. Most aluminum produced today is derived from non-renewable resources, with the aluminum industry emitting approximately 500 million tonnes of carbon dioxide equivalent annually; this constitutes about 1 % of the world’s total CO2 emissions. Countries like Iceland, Norway and Canada use hydroelectric and geothermal power for aluminum production so the only way to achieve substantial reduction in carbon dioxide emissions are to change the anode material. By replacing the carbon-based material with an inert material, oxygen, rather than carbon dioxide, is evolved as the main by-product. Potential materials for inert electrodes have a limited lifetime in the corrosive cryolite electrolyte at 960 °C. This drawback has led to significant research in altering electrolyte composition and lowering bath/electrolyte temperature to improve inert anode stability. The objective of this thesis was to investigate the influence that different operating parameters have on current efficiency in low temperature electrolysis with vertical inert electrodes. \n \nFurther research is needed before implementing inert anode technology on an industrial level, therefore parameter optimization should continue to be the focus during experimentation for improving current efficiency. Future electrolysis experiments at Innovation Center Iceland should consider using the following parameters: \n \n• An extended cathode with an alumina sleeve to limit aluminum reoxidation \n• A reasonable superheat value \n• A sodium-rich electrolyte with potassium additives \n• Low copper content anodes of homogeneous microstructure which are pre-oxidized prior to experimentation \n \nKeywords: aluminum electrolysis, current efficiency, vertical inert electrodes, low-temperature electrolyte, operating parameters \n \n \nThis thesis has restricted access and will remain closed to the public until June 2022.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".