For firing high-thermal-insulation clay blocks, the raw materials must meet certain preconditions and the firing process fulfil certain requirements. These are necessary to make more efficient use of the raw materials enthalpy contained in the clay blocks owing to the addition of pore-forming agents. Associated with this is the release of combustion heat to save on the energy supplied by burners. It is significant how and how far the exothermal and endothermal reactions can be influenced based on design of the firing process and the atmospheric conditions to maximize efficiency for realization of the raw material enthalpy. In the process for firing bricks, facing bricks and roofing tiles, the carbon contained in the raw material is generally regarded as a nuisance. Its burn-off and associated formation of reduction cores often present a firing problem. One energy advantage of the raw material enthalpy requires that the formation of the body structure during the preheating process and the gas diffusion required for the expiration of reaction gases follow certain laws.

Dipl.-Ing. Michael Ruppik, Brick and Tile Research Institute Essen Regd.