High Alumina Bricks for Blast Furnaces
High Alumina bricks have great features like high temperature performance, great corrosion and wear resistance, high bulk density, low iron content, etc. High Alumina bricks are extensively used in mining, metallurgy, cement...
High alumina bricks for blast furnaces were mainly made Yangquan Bauxite,being high pressure pressed and sintered in high temperature.Main minerals compositions are mullite and corundum phases.These products were widely used in all parts of furnace lining of their excellent physical/chemical properties in high temperature.The wall, checker, combustion chamber, regenerator, wind mixing chamber, connecting main, combine brick, roof, bottom and burner of hot blast furnace.
High Alumina Bricks are produced with select bauxite chamotte as main raw material, fired at 1450-1470 °C by advanced process with strict quality control.
High Alumina bricks have great features like high temperature performance, great corrosion and wear resistance, high bulk density, low iron content, etc. High Alumina bricks are extensively used in mining, metallurgy, cement, and chemical, refinery and refractory industries.
These bricks are used in all kinds of industrial furnaces and high temperature areas to prolong the lives of furnaces.
- Fused alumina and sintered corundum
- Fused mullite and sintered mullite
- Andalusite and kyanite
- Bauxite
- Calcinated fireclay
Refractory lining of blast furnace
A modern blast furnace (BF) is refractory lined to protect the furnace shell from the high temperatures and abrasive materials inside the furnace. The refractory lining is cooled to further enhance the protection against the dispatch of excess heat that can destroy the refractory lining. BF has a complex refractory system to provide a long, safe life that is necessary for the blast furnace availability and for permitting nearly continuous furnace operation and casting.
Conditions within the blast furnace vary widely by region and the refractories are subjected to a variety of wear mechanisms. Details are given in Tab 1. The application condition of different regions of a blast furnace is not the same due to the very nature of its geometry and also due to the pyrometallurgical process occurring at different stages. There are diverse physical and chemical wear mechanisms in the different regions of the blast furnace and they are complex in nature. For example mechanical wear or abrasion occurs mainly in the upper stack region and is caused by the decent of the charge materials and by the dust laden gases. High thermal loads are a major factor in the lower stack and the belly regions. In the hearth region, horizontal and vertical flow of hot metal combined with thermal stresses often form undesirable elephant foot shaped cavitation. The refractory materials in these regions are to take care of these wear mechanisms to avoid damage due to them. Therefore, the BF stack (upper middle and lower), belly, bosh, raceway and tuyere region, hearth, and taphole all require different quality of refractories depending on the respective application conditions.
| Tab 1 Attack mechanisms in different regions of blast furnace | ||
| Region | Attack mechanism | Resulting damage |
| Upper stack | Abrasion | Abrasive wear |
| Medium temperatures fluctuations | Spalling | |
| Impact | Loss of bricks | |
| Middle stack | Medium to heavy temperatures fluctuations | Spalling |
| Gas erosion | Wear | |
| Oxidation and alkali attack | Deterioration | |
| Lower stack | Heavy temperatures fluctuations | Severe spalling |
| Erosion by gas jets and abrasion | Wear | |
| Oxidation and alkali attack | Deterioration | |
| Thermal fatigue | Shell damage and cracks | |
| Belly | Medium temperatures fluctuations | Spalling |
| Oxidation and alkali attack | Deterioration | |
| Abrasion, gas erosion and high temperature | Wear | |
| Bosh | High temperature | Stress attack |
| Slag and alkali attack | Deterioration and wear | |
| Medium temperatures fluctuations | Spalling | |
| Abrasion | Wear | |
| Raceway and | Very high temperature | Stress cracking and wear |
| Tuyere region | Temperatures fluctuations | Spalling |
| Oxidation (water and oxygen) | Deterioration | |
| Slag attack and erosion | Wear | |
| Damage from scabs | Loss of cooling elements and tuyeres | |
| Hearth | Oxidation (water) | Wear |
| Zinc, slag and alkali attack | Deterioration | |
| High temperature | Stress build up and cracking | |
| Erosion from hot liquids | Break out risk | |
| Iron notch | Heavy temperatures fluctuations | Spalling |
| (tap hole) | Erosion (slag and iron) | Tap hole wear |
| Zinc and alkali attack | Deterioration | |
| Gas attack and oxidation (water) | Wear and deterioration | |
Selection of appropriate refractory combination depending on the wear mechanism is very important. An improper selection of the refractories often leads to a refractory failure which, subsequently, becomes a complex problem to solve. Types of refractory lining required in a blast furnace region wise as well as the trend in the refractory lining pattern is given in the Fig 1.
| Tab 2 Blast furnace refractories | ||
| Area | Present | Trend |
| Stack | 39 % – 42 %% Al2O3 | Super duty fireclay |
| Belly | 39 % – 42 % Al2O3 | Corundum, SiC-Si3N4 |
| Bosh | 62 % Al2O3, Mullite | SiC-Si3N4 |
| Tuyere | 62 % Al2O3, Mullite | SiC self bonded, Alumina-chrome (Corundum) |
| Lower hearth | 42 %-62 % Al2O3, Mullite, Conventional carbon block | Carbon/Graphite block with super micro pores |
| Tap hole | Fireclay tar bonded, High alumina / SiC tar bonded | Fireclay tar bonded, High alumina / SiC tar bonded |
| Main trough | Pitch / water bonded clay / Grog / Tar bonded ramming masses, Castables | Ultra low cement castables (ULCC), SiC / Alumina mixes, Gunning repairing technique |
| Tilting spout | High alumina bricks / SiC ramming masses / Low cement castables | High alumina bricks/ SiC / Carbon / ULCC |
