Monolithic linings at the kiln mouth, hood, tertiary air duct and cooler

The kiln mouth, hood, coal-injection pipe, tertiary air duct and grate cooler do not sit in the mid-span of the rotating shell, yet they often fail before it. Turning gas, the impact of secondary air and clinker, and frequent temperature swings make thermal shock and erosion here more severe than on most brick faces inside the kiln. A monolithic lining can be placed to the shape, and its formulation can be aimed at thermal shock, toughness or build-up.

Corundum–mullite castables have good thermal shock, high strength, low thermal expansion and strong corrosion resistance, and suit the front kiln mouth, coal-injection pipe, kiln hood, tertiary air duct and grate cooler — positions where the hot-face temperature is high and erosion is obvious. High-alumina low-cement castables are dense; micropowder additions raise their intermediate- and high-temperature strength, and they are often used in the hood, grate cooler, preheater, calciner and tertiary air duct. With heat-resistant stainless-steel fibre, the castable keeps its high-temperature properties and gains toughness and resistance to mechanical vibration, which is why it is used at the front kiln mouth, coal-injection pipe and hood.

Build-up is a different kind of damage. Anti-skinning castables based on silicon carbide rely on its poor wetting, together with good conductivity and wear resistance, to give the burden less chance to dwell and sinter on the hot face. At the hood and the cooler, where radiation and burden impact are both stronger, hanging brick can be used, so that anchorage and the working face are considered together. The starting point at these positions is the path of thermal shock, the direction of erosion, and whether build-up occurs — not a simple transfer of the mid-kiln brick.