Utilization trials of lignite solid byproducts of West Macedonia and Peloponnesus lignite fired power plants for the production of lightweight aggregates

Περίληψη

The production of lightweight aggregates from the utilization of solid byproducts [fly ash (FA) and bottom ash (BA)], of the lignite fired power plants from West Macedonia (Kardia, Ptolemaida) and Peloponnesus (Megalopolis), has been investigated in this study. Sintering of FA and BA with the grate sinter band method was selected because it exploits the energy content of the raw materials for the increase of temperature and completion of the material's sintering. These byproducts contain the necessary carbon content for temperature increase during the sintering process. Detailed XRD analyses show that Megalopoli's FA contains high amounts of amorphous phase (25-54wt%) while fly ashes from Kardia and Ptolemaida power units are more crystalline. Lime and anhydrite are the most abundant crystalline phases in Ptolemaida's and Kardia's fly ashes. The bottom ashes revealed high percentages of amorphous content (58-64wt%) and anorthite and quartz as the major crystalline phases. Mixtures of different BA/FA ratios were prepared for sintering tests. The sintered mixtures from Kardia's and Ptolemaida's regions did not have sufficient mechanical properties for further treatment. The sintercake produced from Megalopolis' ashes exhibited good mechanical properties and was selected for further study for use as light aggregate raw materials to the lightweight concrete production.