ABSTRACT
The lignite-fired power plants of the Rhineland produce about 6.1 million t of lignite ashes, 1.3million of gypsum from the flue gas desulphurization (FGD), and 750000m3 of ‘FGD-water’ (circulation water enriched in trace elements and chlorides ranging up to 10 g/litre
Cl ), per year. In order to minimize groundwater contamination the following
concept (besides technical barriers in the dump) has been developed: mixing of appropriate amounts of ashes and gypsum (as far as not recycled) with diluted ‘FGD-water’ (water/solid ratio approximately 0.3) to form a sludge ready for disposal. As a result of mineral reactions the paste-like mixture sets in the disposal dump to give a solid material similar to a supersulphated slag cement mortar. Analogous laboratory samples (unit weight 1.7-2.0g/cm3) show relatively high compressive strength (5-15N/mm2; 180 days), low water permeability
and leachability.
