Refractories are construction materials designed to withstand aggressive service conditions at high temperature. Refractory materials are used as heat-resistant walls, coatings or linings to protect units from oxidation, corrosion, erosion and heat damage. Industries that need refractories include: steel, non-ferrous metals, glass, power, cement, petrochemicals and waste incineration. Refractory products can be divided into the following types: Bricks and shaped materials, monolithic materials and insulating materials.
Monolithic or castable materials – refractory raw materials are premixed and then installed in-situ by various methods such as ramming, gunning or shotcreting. Key types include LCC – low cement castables, and ULCC - ultra low cement castables.
These aluminas are ground in continuous ball-mills or air-jet mills to median particle sizes (d50) 3, 4, 5 or 6 µm.
These aluminas have low specific surface area (BET < 1m²/g) and are almost entirely alpha alumina. Standard soda content is 3000-4000 ppm and intermediate soda content is 2000-3000 ppm. Hard calcined aluminas are produced in rotary kilns.
These low soda aluminas are ball-milled to their primary crystal size, which ranges from 0.4 to 2.5 µm. Soda contents are between 300 and 500ppm.