The Role of Anode Manufacturing Processes in Net Carbon Consumption †
Abstract
:1. Introduction
2. Anode Consumption
- electrochemical formation of carbon dioxide,
- electrochemical formation of carbon monoxide,
- carboxy (Boudouard) reaction,
- air burn, and
- dusting as a consequence of preferential oxidation.
3. Plant Parameters
4. Findings
4.1. Pitch Addition
4.2. Impurities
4.3. Desulfurization of Anodes
5. Discussion
6. Conclusions
- Anodes with higher pitch content have higher CO2 reactivity residue and lower CO2 reactivity dust, both of which are favorable in reducing net carbon consumption.
- Anodes with higher metallic impurity content have lower CO2 reactivity residue and higher CO2 reactivity dust, which increase net carbon consumption.
- Higher baking temperatures favor desulfurization of anodes. Desulfurization of anodes lowers CO2 reactivity residue while increasing air permeability, thereby resulting in increased net carbon consumption.
- Pitch addition, impurity content, and desulfurization need to be optimized by adjusting anode manufacturing parameters to reduce net carbon consumption.
Author Contributions
Conflicts of Interest
References
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Mechanism | Anode Consumption, Mass % Prebaked Cells |
---|---|
Basic reaction: 2Al2O3 + 3C = 4Al + 3CO2 | 66–76 |
Excess consumption: C + O2 = CO2 and 2C + O2 = 2CO | 8–15 |
Boudouard reaction: CO2 + C = 2CO | 5–6 |
Unreacted dust | 0.3 |
Re-oxidation of metal | 7–8 |
Pyrolysis and vaporisation | 0.2 |
Sulphur, metal impurities and carbon loss by butts return | 3.5–4.5 |
Net carbon consumption [kg C/t Al] | 400–450 |
Analysis | Unit | Coke A | Coke B | Coke C |
---|---|---|---|---|
Average | Average | Average | ||
Fe | % | 0.014 | 0.007 | 0.002 |
Si | % | 0.014 | 0.001 | 0.003 |
S | % | 2.57 | 1.05 | 2.83 |
V | % | 0.024 | 0.005 | 0.019 |
Ni | % | 0.022 | 0.008 | 0.009 |
Ca | % | 0.013 | 0.001 | 0.001 |
Na | % | 0.006 | 0.004 | 0.002 |
Ash | % | 0.19 | 0.05 | 0.08 |
Moisture | % | 0.06 | 0.08 | 0.08 |
Real density | g/cm³ | 2.081 | 2.072 | 2.079 |
Vibrated bulk density (VBD) | g/cm³ | 0.938 | 0.925 | 0.864 |
Volatile matter (VM) | % | 0.40 | 0.44 | 0.42 |
Hard grove index (HGI) | no | 31.5 | 36.0 | 31.8 |
+4 Mesh | % | 36.3 | 27.4 | 35.3 |
−20 Mesh | % | 24.6 | 26.1 | 22.9 |
CO2 reactivity | % | 12.2 | 7.0 | 2.7 |
Air reactivity | %/min | 0.29 | 0.07 | 0.07 |
Electrical resistivity | μΩ·m | 464.4 | 441.5 | 492.8 |
Lc | nm | 3.09 | 2.88 | 3.05 |
Calciner type | Shaft | Rotary | Rotary |
Parameter | Unit | Value |
---|---|---|
Dry aggregate GSR | No. | 3.5 to 4.5 |
Pitch content | % | 12.5 to 14.5 |
Mixer energy | kWh/t paste | 7.5 |
Vibro-compaction time | s | 45 to 55 |
Top tool pressure | kPa | 250 to 450 |
Vacuum | kPa | 2 to 3 |
Baking temperature | °C | 1160 to1190 |
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Khaji, K.; Al Qassemi, M. The Role of Anode Manufacturing Processes in Net Carbon Consumption. Metals 2016, 6, 128. https://doi.org/10.3390/met6060128
Khaji K, Al Qassemi M. The Role of Anode Manufacturing Processes in Net Carbon Consumption. Metals. 2016; 6(6):128. https://doi.org/10.3390/met6060128
Chicago/Turabian StyleKhaji, Khalil, and Mohammed Al Qassemi. 2016. "The Role of Anode Manufacturing Processes in Net Carbon Consumption" Metals 6, no. 6: 128. https://doi.org/10.3390/met6060128