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6.1.2.5.2 Regular Calcinate
ОглавлениеThe quality of calcined petroleum coke produced in Europe is superior to that produced in other continents. Due to regulatory requirements and improvements in efficiency, regular calcinate in Europe has undergone a quality upgrade toward needle coke: the sulfur contents, reactivity results, and CTE figure are lower, and the vibrated bulk density is higher. Some non‐European manufacturers are already producing similar qualities. Typical European quality characteristics are listed below. The figures in brackets refer to quality requirements outside Europe [38–41].
| Sulfur content (wt%) | Maximum 1.7 (3) |
| Ni/V content (ppm) | Maximum 120–150 (200) |
| Na/Ca/Si content (ppm) | Maximum 100 |
| Vibrated bulk density (1–2 mm) (g/cm3) | 0.80–0.85 (0.75–0.80) |
| Air reactivity (1–1.4 mm) (wt%/min) | Maximum 0.15 |
| CO2 reactivity (1–1.4 mm) (wt%) | Maximum 12 |
| CTE factor (carbon anodes) (10−6/°C) | 3.5–4.5 (5.5) |
| Hydrogen content (wt%) | 0.05–0.09 |
| Real density (g/cm3) | 2.06–2.10 |
| Ash content (wt%) | 0.05–0.20 |
| Crystallite size Lc (nm) | 2.5–3.2 |
| Specific electric resistivity (μΩ m) | 460–520 |
| Grain stability (wt%) | Minimum 70 |
| Dust forming factor (wt%) | Maximum 0.02 |
| Water/oil content (wt%) (from antidust additive) | Maximum 0.3 |
Except for the SO2 emissions, the sulfur content has only marginal side effects on aluminum electrolysis.
The goal in aluminum electrolysis is to have minimum consumption of anodes with a good electricity yield. Good production results are 95% electricity yield with an anode consumption of <410 kg per ton aluminum. These figures can be reached if the anodes meet the specifications for:
1 1. High carboxy (CO2) reactivity residue.
2 2. High air reactivity residue.
3 3. Low specific electric resistivity.
4 4. Low thermal conductivity.
With the capacity increase of aluminum smelters, larger anodes have come into use. Cracking of the anodes due to thermal shock has been observed occasionally in these cases. Good thermal shock resistance of the anodes is therefore desirable. Improvements in thermal shock behavior will occur if CTE, the Youngs modulus, and the flexural strength are decreased and the thermal conductivity is increased.
