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.
Insulating materials – bricks and monolithics that are used to prevent heat loss to conserve energy and for safety. Also ceramic fibres fabricated into mats, blankets and other shapes.
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.