tabular alumina” refers to the raw material itself, “tabular refractory” refers to the finished product—a brick, castable, plastic, or other monolithic shape—that uses tabular alumina as its primary aggregate.
What are Tabular Refractories?
Tabular refractories are a class of high-alumina refractories where the main aggregate is tabular alumina. The goal is to transfer the superior properties of the tabular alumina grains into a robust final product that can withstand extreme thermal, chemical, and mechanical conditions.
They are used to line furnaces, kilns, reactors, and other high-temperature processing units.
Key Properties of Tabular Refractories
Since they are based on tabular alumina, these refractories inherit and exhibit:
Very High Refractoriness: They can withstand extremely high temperatures, often exceeding 1800°C, without softening.
Excellent Thermal Shock Resistance: This is a critical property. The interlocking tabular crystals and the material’s ability to handle rapid temperature changes without cracking make it invaluable in cyclic processes.
High Mechanical Strength & Abrasion Resistance: They maintain structural integrity and resist wear from solid materials (like charge in a furnace) at high temperatures.
Superior Chemical Inertness: Highly resistant to attack by slags, fluxes, and alkalis, especially in neutral and oxidizing atmospheres.
Low Porosity: The dense, sintered structure of the tabular grains results in a final product with low apparent porosity, reducing slag penetration and gas infiltration.
Volume Stability: They exhibit minimal permanent linear change (PLC) upon re-heating, meaning they don’t shrink or expand significantly during use, which prevents the opening of joints and cracks.
Common Types and Forms of Tabular Refractories
Tabular alumina aggregate can be formed into refractory products in several ways:
| Form | Description | Common Use Cases |
|---|---|---|
| Bricks (Shaped) | Pre-fired bricks made by pressing a mix of tabular alumina grains and a bonding agent (often a fine alumina cement or clay). | Lining of rotary cement kilns (burning zone), steel ladles, ceramic kilns, and chemical reactors. |
| Castables (Monolithics) | Dry mixtures of tabular alumina aggregates, fine fillers, and hydraulic or chemical binders. They are mixed with water on-site and cast, gunned, or vibrated into place. | Versatile for linings of complex shapes, furnace roofs, burner blocks, and patching. Low-cement and ultra-low-cement castables (LCC/ULCC) offer even better performance. |
| Plastics & Rammables | Moldable, clay-bonded mixes with high plasticity. They are rammed or pounded into place to form a seamless lining. | Areas requiring a joint-free lining or for repair work in existing furnaces. |
| Sprayables | Similar to castables but designed to be sprayed onto a surface using a gun, often for rapid lining or repair. | Refurbishing and repairing furnace linings without full dismantling. |
Key Applications in Industry
Tabular refractories are the workhorses of heavy industry wherever extreme conditions exist:
Iron & Steel Industry:
Steel Ladles: Lining for the walls and bottom due to excellent slag resistance and thermal shock.
Ladle Furnaces: Critical for roofs and sidewalls where temperatures are extreme.
Torpedo Cars: Lining for transporting molten iron.
Cement & Lime Industry:
Rotary Kilns: The burning zone of a cement kiln is the most demanding area, subject to extreme temperatures, chemical attack from clinker, and mechanical abrasion. Tabular alumina bricks are the standard here.
Petrochemical & Chemical Industry:
Steam Crackers & Reformers: Lining for radiant sections and as support balls for catalyst tubes, where high temperatures and thermal stability are paramount.
Chemical Reactors: For processes involving high temperatures and corrosive atmospheres.
Ceramics & Non-Ferrous Metals:
Kilns & Furnaces: Used for the hottest zones in ceramic kilns and furnaces for melting non-ferrous metals like copper and aluminum.
