VERFAHREN ZUR HERSTELLUNG WAERMEDAEMMENDER VOLL- UND LOCHSTEINE AUS WIRBELSCHICHTRUECKSTAENDEN

To produce heat-insulating solid and hollow bricks of low apparent density from residues of fluidised-bed furnace installations (1) operated with ballast-containing bituminous coals, a process is used in which the fluidised-bed filter ash is used as a mixture with coarser material, above all coarse sand, in a ratio of about 60:40. This mixture is, to set a pressing moisture content of preferably 12.5 %, mixed with about 4 to 7 % by weight of lime. The product is then premoulded in conventional moulds and compacted, the pressing rate, i.e. the stroke rate of the ram (21) of the press (20) being reduced from about 8 to 15 seconds/stroke, depending on the size of the bricks. After compaction, hardening is carried out in an autoclave (22) at 180 DEG C for a total of 4 hours, and heating of the vessel should be carefully extended over 2 hours, and the release of the pressure should also be extended over 2 hours. By applying hydrothermal hardening, this process allows the setting times of the binders concerned to be combined within the hardening period of 4 hours and to conclude this process to such an extent that structure-destroying swelling phenomena, which otherwise occur, are avoided.