Μελέτη ασβεστοποίησης των κρυσταλλικών ασβεστολίθων Αγίου Παντελεήμονα Φλώρινας

Abstract

The studied limestones are described as coarse-grained. Mineralogically they are very pure because they contain calcite 98.8%, dolomite 0.8% and traces of micas, quartz, chlorite, feldspars, hematite, amphiboles, epidote, pyrite, titanite, ilmenite and zircon. The organic material of the crystalline limestones was defined to be 0.8% and their insoluble residue 1%. From the SEM-EDS study, it was ascertained that the calcite.s crystals are extremely pure with mean content of CaO 55.14%, while the main admixture is MgO with an average of 0.57%. Chemically, the examining limestones are very pure with an average of CaO 53.67%. This percentage corresponds to a 95.8% CaO content and thus the Agios Panteleimonas limestones can be classified as high-calcium materials suitable for calcination. The beginning of calcination is set approximately at 750o C, while its completion according to the size of the cubic samples is noted between 1,000 and 1,150o C. The appearance of non-crystalline phase is noted during the progress of calcination at a percentage ranging from 1 to 18%. From the SEM-EDS study it can be evident that the calcination is developing uniformly from the periphery of the samples towards the core. The produced lime in the thoroughly calcined samples is of high quality with CaO values greater than 90%. As far as the trace elements are concerned, Ag enriches the produced lime, whereas none of these elements shows organic affinity. The trace elements Ba, La, Sc, Sm, Sr, U, V, Y and Zr show intermediate affinity. Many other elements were determined and remain under the detection limit almost under any calcination condition. It is concluded that the calcination conditions do not affect the elements behaviour. As far as the technological characteristics are concerned the examined limestones have an average dry apparent weight of 2.6 g/cm3. During the cubic samples calcination with an average edge of 1 cm, the calcination is completed at around 1,000o C and the dry apparent weight gets an average value of 1.4 g/cm3. The retention for a longer period of time in that temperature or the exposure to greater temperatures causes increase of the dry apparent weight that is shrinkage phenomena in cubic samples. Indeed, for calcination temperature of 1,150o C, values of dry apparent weight were counted up to 1.7 g/cm3. In cubic samples of mean edge of 2 and 4 cm, proportionate phenomena are being observed but not so intense. On the other hand, in cubic samples of mean edge of 6 and 8 cm the calcination progress is more normal and a lower value of the dry apparent weight is achieved in greater temperatures. It is noted then, that the quality of the produced lime from a given limestone does not only depend on the calcination conditions, but also on the limestone fragments size that will be calcined.