What is high temperature insulation?

Heat insulating materials are products for refractory linings of thermal industrial plants with the objective to reduce heat losses. Materials with low thermal conductivity and low heat capacity have to be used to reach that goal.
High insulating materials have a total porosity of at least 45 %. In practice, the materials used have a porosity from 60 to 90 % and in extreme cases up to 99 %. High porosity causes low mechanical strength, high gas permeability and low corrosion resistance. 

The thermal conductivity depends not only on the total porosity of the material but also on the pore size and shape, the structure composition and the mineralogical composition. Depending on temperature, the factors responsible for the flow of heat – solid state conduction, convection and radiation – vary in influence. Maximum pore diameters of < 1 mm are necessary. Microporous insulating materials with pores < 0.1 µm have the lowest thermal conductivity. 

Several processes can be used to create and modify the pores of the insulating materials, for example thermal decomposition, foam, bloating (swelling) and gas impellent processes, the use of evaporating liquids or solids and the utilisation of fibre structures and natural or synthetic lightweight additives.

Lightweight heat insulating materials have almost completely replaced heavy designs with dense refractory materials like chamotte, when it is an application with low mechanical load and low corrosion stress.

The thermal shock resistance of lightweight construction materials has a large influence on applications. High temperature wool products (AES/PCW/ASW) resist severe thermal shocks. Other lightweight construction materials are sensitive to thermal shock.

Thermal conductivity of different heat insulating materials

Overview of the most important groups of high temperature insulation materials