Refractory Materials

The purpose of a refractory material is to withstand the high temperatures required in furnaces, kilns, incinerators, power plants etc without contaminating other materials and to conserve heat in the area where it is needed. Dense refractories are heavy with low porosity but high mechanical strength. Insulating refractories have a higher porosity making them less dense and with low thermal conductivity. This increases efficiency and reduces the amount of energy required for the process at hand.
The most common form of dense refractories are firebricks. Made from hydrated aluminium silicates with small amounts of other elements, they are versatile and relatively cheap. Firebricks with a higher alumina content are able to perform at higher temperatures. Refractories with an alumina content of 99% are known as corundum and are used in processes at over 1500°C such as pouring steel, glassmaking, ash melting, incineration and moulds for casting super alloys.
Zirconium silicate is the principal ingredient of zircon refractories which are extremely strong up to temperatures over 1750°C. They are used to build furnaces and kilns, to make crucibles in the metallurgical industries because they do not react with liquid metals and in glass furnaces because they are not wetted by the molten glass.
Monolithic refractories are supplied in unshaped form to be cast, rammed or gunned into place on site. Casting refractories are also known as refractory concretes and contain high alumina cement. They are used in the iron and steel industries in kiln cars, boilers and to cover the floor, doors, walls and other surface areas where high temperature processes take place. Insulating castables contain lightweight aggregates such as vermiculite. They are weaker than standard castables. Plastic refractories are supplied in clay like blocks which can be cut to size and rammed into place. They are designed for repairs to brick or monolithic linings and are also used in ladles and launders.
Insulation firebricks are made from fireclays with added alumina, for its refractory properties, and organic filler which burns away during firing to leave a lightweight and porous brick. Bricks are graded according to the temperature level they can withstand and are used for lining furnaces and kilns or as secondary insulation, flue linings, in soaking pits and reactor chambers, among others.
Refractory ceramic fibre, also known as alumina silicate wool, is a form of high temperature insulation wool. Spun from a mix of melted aluminium dioxide and silicon dioxide, the fibres are made into blankets, paper, rope, board and block modules. Lightweight with low thermal conductivity and excellent thermal shock resistance, ceramic fibre products are used for insulation in boilers and kilns, on kiln cars, in the crowns of glass furnaces and around expansion joints, to create seals around furnace doors, and as lining for reforming and pyrolysis in the petrochemical industry.