China's Refractories ›› 2021, Vol. 30 ›› Issue (1): 7-16.DOI: 10.19691/j.cnki.1004-4493.2021.01.002
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GUO Zongqi1,*(), ZAMBONI Stefano1, GAO Jianying2, GAN Feifang3
Online:
2021-03-15
Published:
2021-05-01
Contact:
GUO Zongqi
About author:
Dr. Guo Zongqi started his refractory career in 1983 after finishing his study in Xi’an University of Architecture & Technology. He then joined Luoyang Institute of Refractories Research to work on refractory researches and applications for more than 10 years. In 2001, he received his PhD degree in Ecole Polytechnique, University of Montreal, Canada. He then continues with refractory R&D activities and management in several international refractory companies. His refractory experiences include the pioneer research and production of high chromia refractories for slagging coal gasifiers and the technology development of burnt and unburnt basic bricks for steelmaking processes, cement rotary kilns and glass-making regenerators.
GUO Zongqi, ZAMBONI Stefano, GAO Jianying, GAN Feifang. Indispensability and Vulnerability of Magnesia-carbon Bricks for Steelmaking Process[J]. China's Refractories, 2021, 30(1): 7-16.
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URL: http://www.cnref.cn/EN/10.19691/j.cnki.1004-4493.2021.01.002
Parameter | DOM mode | INT mode |
---|---|---|
Fused magnesia | Ordinary FM | Large crystal FM |
Making process | One step | Two steps |
Fusion input | Magnesite ore lumps | CCM briquettes |
MgO content /mass% | > 97.50 | > 97.50 |
Periclase crystal size /µm | 400-600 | 800-1 000 |
MgO-C bricks /ladle | Slagline | Slagline |
Total C content /mass% | 14 | 14 |
Binder | Resin | Resin |
Antioxidant | Yes | Yes |
Ladle refining /% | 100 | 100 |
RH degassing /% | 50-75 | 50-75 |
Service lifetime /heat | 32-35 | 72-75 |
Slagline in a ladle campaign | Three replacement | One replacement |
Table 1 Distinctions of magnesia-carbon bricks for slagline of ladles
Parameter | DOM mode | INT mode |
---|---|---|
Fused magnesia | Ordinary FM | Large crystal FM |
Making process | One step | Two steps |
Fusion input | Magnesite ore lumps | CCM briquettes |
MgO content /mass% | > 97.50 | > 97.50 |
Periclase crystal size /µm | 400-600 | 800-1 000 |
MgO-C bricks /ladle | Slagline | Slagline |
Total C content /mass% | 14 | 14 |
Binder | Resin | Resin |
Antioxidant | Yes | Yes |
Ladle refining /% | 100 | 100 |
RH degassing /% | 50-75 | 50-75 |
Service lifetime /heat | 32-35 | 72-75 |
Slagline in a ladle campaign | Three replacement | One replacement |
Raw material | Carbon /mass% | Volatile matter /mass% | Ash /mass% | Surface area /(m2 · g-1) |
---|---|---|---|---|
Flake graphite | 94.12 | 0.78 | 5.09 | 6.36 |
Table 2 Physical and chemical analyses of flake graphite
Raw material | Carbon /mass% | Volatile matter /mass% | Ash /mass% | Surface area /(m2 · g-1) |
---|---|---|---|---|
Flake graphite | 94.12 | 0.78 | 5.09 | 6.36 |
Heating temperature | Phase transformation | Description |
---|---|---|
At 660 °C | Al liquid | Melting starting |
Al2O3 coating ripped | A fine layer of Al2O3 | |
Over 660 °C | 4Al(l)+3C(s) → Al4C3(s) | Surrounding carbon |
2Al(s)+N2(g) → 2AlN(s) | In presence of air | |
At 1 100 °C | Al liquid disappears | |
Over 1 100 °C | Al4C3+3O2(g) → Al2O3+3C | In presence of air |
2AlN(s)+CO(g) → Al2O3(s)+N2(g)+3C(s) | ||
Al2O3+MgO(s) → MgO·Al2O3(s) | Spinel crystals forming | |
At 1 500 °C | Al4C3 and AlN disappear | Spinel crystals growing |
Table 3 Phase transformations of metallic Al in MgO-C brick
Heating temperature | Phase transformation | Description |
---|---|---|
At 660 °C | Al liquid | Melting starting |
Al2O3 coating ripped | A fine layer of Al2O3 | |
Over 660 °C | 4Al(l)+3C(s) → Al4C3(s) | Surrounding carbon |
2Al(s)+N2(g) → 2AlN(s) | In presence of air | |
At 1 100 °C | Al liquid disappears | |
Over 1 100 °C | Al4C3+3O2(g) → Al2O3+3C | In presence of air |
2AlN(s)+CO(g) → Al2O3(s)+N2(g)+3C(s) | ||
Al2O3+MgO(s) → MgO·Al2O3(s) | Spinel crystals forming | |
At 1 500 °C | Al4C3 and AlN disappear | Spinel crystals growing |
Antioxidant | Phase and VE coefficient | |
---|---|---|
Al | Al2O3 | MgO·Al2O3 |
1.30 | 1.43 | |
Si | SiO2 | 2MgO·SiO2 |
2.20 | 1.95 |
Table 4 Volume expansion (VE) of phase transformations
Antioxidant | Phase and VE coefficient | |
---|---|---|
Al | Al2O3 | MgO·Al2O3 |
1.30 | 1.43 | |
Si | SiO2 | 2MgO·SiO2 |
2.20 | 1.95 |
Specification | Domestic resin DH | Domestic resin RM | European resin H9905 |
---|---|---|---|
Viscosity at 20-25 °C /(Pa·s) | 10-16 | 1.1 (1.05-1.55) | 1.85-2.15 |
Solid content at 135 °C /mass% | ≥ 79 | 75 (70-80) | 70-74 |
Moisture content /mass% | ≤ 4 | 8.0 (7.0-10) | 7.0-8.0 |
Carbon residue fired at 800 °C /mass% | ≥ 40 | 45 (≥ 39) | ~50 |
Free phenol content GC /mass% | 9.0 ± 2.0 | 12 (10.5-13.5) | Max. 0.2 |
Table 5 Chemical and physical analyses of phenol-formaldehyde resin
Specification | Domestic resin DH | Domestic resin RM | European resin H9905 |
---|---|---|---|
Viscosity at 20-25 °C /(Pa·s) | 10-16 | 1.1 (1.05-1.55) | 1.85-2.15 |
Solid content at 135 °C /mass% | ≥ 79 | 75 (70-80) | 70-74 |
Moisture content /mass% | ≤ 4 | 8.0 (7.0-10) | 7.0-8.0 |
Carbon residue fired at 800 °C /mass% | ≥ 40 | 45 (≥ 39) | ~50 |
Free phenol content GC /mass% | 9.0 ± 2.0 | 12 (10.5-13.5) | Max. 0.2 |
Stage | DOM mode | INT mode | |
---|---|---|---|
Mixing | Facility | Conventional mixer | High speed intensity mixer |
Duration | 40-50 min | < 10 min | |
Capacity | < 1 t | 2 t | |
Pressing | Facility | Screw press | Hydraulic press |
Manner | Deairing, impacting | Deairing, static pressing | |
Pressing | 8-15 strokes | 1 static pressing | |
Charging | Weighing feeder | Volumetric feeder | |
Green brick | Manual removal | Robotic device | |
Output | 1 shape | 3 shapes | |
Tempering | Tunnel kiln | Electrically heated | Fired by natural gas |
Operation | Intermittent | Continuous | |
Capacity | 10 000 t/a for a kiln | Min. 50 000 t/a for a kiln | |
Duration | 12 h | 8 h |
Table 6 Manufacturing process of MgO-C bricks
Stage | DOM mode | INT mode | |
---|---|---|---|
Mixing | Facility | Conventional mixer | High speed intensity mixer |
Duration | 40-50 min | < 10 min | |
Capacity | < 1 t | 2 t | |
Pressing | Facility | Screw press | Hydraulic press |
Manner | Deairing, impacting | Deairing, static pressing | |
Pressing | 8-15 strokes | 1 static pressing | |
Charging | Weighing feeder | Volumetric feeder | |
Green brick | Manual removal | Robotic device | |
Output | 1 shape | 3 shapes | |
Tempering | Tunnel kiln | Electrically heated | Fired by natural gas |
Operation | Intermittent | Continuous | |
Capacity | 10 000 t/a for a kiln | Min. 50 000 t/a for a kiln | |
Duration | 12 h | 8 h |
Fig. 9 Typical microstructural pattern of hot face of a used MgO-C brick (1) Slag coating, (2) Decarburization layer, (3) Partially decarburized layer
Fig. 12 Microstructure of the vertical crack, 10 mm from the hot face (1) Crack filled with slag, (2) MgO with small periclase crystals, (3) Large MgO crystal
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