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.

North Refractories manufactures high alumina bricks with an Al₂O₃ content range of 45 % to about 99 % and based on natural raw material sources and synthetic raw materials such as:
  • Fused alumina and sintered corundum
  • Fused mullite and sintered mullite
  • Andalusite and kyanite
  • Bauxite
  • Calcinated fireclay
These products are also offered in combination with raw materials rich in aluminium with either ceramic binding or aluminium phospate binding. Special characteristics of the aluminium rich products, such as thermal shock resistance and corrosion resistance, are achieved by additives having zirconium, chromium and carbon content and which are tuned to the relevant usage conditions.

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
RegionAttack mechanismResulting damage
Upper stackAbrasionAbrasive wear
Medium temperatures fluctuationsSpalling
ImpactLoss of bricks
Middle stackMedium to heavy temperatures fluctuationsSpalling
Gas erosionWear
Oxidation and alkali attackDeterioration
Lower stackHeavy temperatures fluctuationsSevere spalling
Erosion by gas jets and abrasionWear
Oxidation and alkali attackDeterioration
Thermal fatigueShell damage and cracks
BellyMedium temperatures fluctuationsSpalling
Oxidation and alkali attackDeterioration
Abrasion, gas erosion and high temperatureWear
BoshHigh temperatureStress attack
Slag and alkali attackDeterioration and wear
Medium temperatures fluctuationsSpalling
AbrasionWear
Raceway andVery high temperatureStress cracking and wear
Tuyere regionTemperatures fluctuationsSpalling
Oxidation (water and oxygen)Deterioration
Slag attack and erosionWear
Damage from scabsLoss of cooling elements and tuyeres
HearthOxidation (water)Wear
Zinc, slag and alkali attackDeterioration
High temperatureStress build up and cracking
Erosion from hot liquidsBreak out risk
Iron notchHeavy temperatures fluctuationsSpalling
(tap hole)Erosion (slag and iron)Tap hole wear
Zinc and alkali attackDeterioration
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
 
AreaPresentTrend
   
Stack39 % – 42 %% Al2O3Super duty fireclay
Belly39 % – 42 % Al2O3Corundum, SiC-Si3N4
Bosh62 % Al2O3, MulliteSiC-Si3N4
Tuyere62 % Al2O3, MulliteSiC self bonded, Alumina-chrome (Corundum)
Lower hearth42 %-62 % Al2O3, Mullite, Conventional carbon blockCarbon/Graphite block with super micro pores
Tap holeFireclay tar bonded, High alumina / SiC tar bondedFireclay tar bonded, High alumina / SiC tar bonded
Main troughPitch / water bonded clay / Grog / Tar bonded ramming masses, CastablesUltra low cement castables (ULCC), SiC / Alumina mixes, Gunning repairing technique
Tilting spoutHigh alumina bricks / SiC ramming masses / Low cement castablesHigh alumina bricks/ SiC / Carbon / ULCC