Quantitative determination of mineral matter in lignite by X-RAY spectrometry, using the Compton effect.

Κατά την αξιολόγηση της ποιότητας των λιγνιτών εκτός από την θερμογόνο δύναμή τους γίνεται προσδιορισμός της ανόργανης ύλης, η οποία έχει εναποτεθεί συγγενετικά με την οργανική ύλη κατά τον σχηματισμό τους, αλλά και κατά το στάδιο της ενανθράκωσης. Ο προσδιορισμός της ανόργανης ύλης γίνεται συνήθως ως τέφρα  μετά από καύση του λιγνίτη, διαδικασία η οποία είναι αρκετά χρονοβόρα. Στην παρούσα εργασία γίνεται προσπάθεια για εύκολο και γρήγορο προσδιορισμό του ποσοστού της ανόργανης ύλης ή της τέφρας σε δείγματα λιγνιτών με άγνωστες συγκεντρώσεις, με φασματόμετρο ακτίνων-Χ. Ειδικότερα γίνεται χρήση του Φαινομένου Compton της λυχνίας ακτίνων-Χ του φασματόμετρου. Η ένταση του Φαινομένου Compton είναι συνάρτηση του συντελεστή απορρόφησης μάζας, ο οποίος με τη σειρά του εξαρτάται από το είδος και το ποσοστό της ανόργανης ύλης που περιέχεται στον λιγνίτη. Εκμεταλλευόμενοι την ιδιότητα αυτή του φαινομένου Compton, προσδιορίστηκε το ποσοστό της ανόργανης ύλης των λιγνιτών. Η ακρίβεια της μεθόδου που χρησιμοποιήθηκε πιστοποιήθηκε με αναλύσεις δειγμάτων Ελληνικών λιγνιτών, με γνωστές περιεκτικότητες ανόργανου υλικού ή τέφρας. Τα αποτελέσματα της εργασίας δείχνουν ότι, με την προτεινόμενη μέθοδο, μπορεί να προσδιοριστεί το ποσοστό του ανόργανου υλικού γρήγορα χωρίς την χρονοβόρα διαδικασία της καύσης του λιγνίτη.For the evaluation of lignite quality, apart from the calorific value, it is necessary to determine the mineral phases, which are deposited simultaneously with the organic matter during the formation of peat or formed epigenetically during the coalification stages. The mineral matter content is usually expressed as ash, after the combustion of lignite, and its determination is a quite time consuming process. In this paper an attempt is made for a fast and easy quantitative determination of mineral matter in lignite samples with unknown concentrations, with the use of an X-ray spectrometer and in particular the Compton effect of the X-ray tube. The intensity of the Compton peak is a function of the mass absorption coefficient of the lignite sample, which in turn depends on the type and amount of the mineral matter contained. Using this property of the Compton Effect, the percentage of mineral matter of lignite was determined. The method was verified by analyzing lignites with known concentrations of inorganic mater. The results of this study showed, that the mineral matter content can be determined, by the proposed method, fast and accurately without lignite combustion

Quantitative determination of mineral matter in lignite by X-RAY spectrometry, using the Compton effect.

Κατά την αξιολόγηση της ποιότητας των λιγνιτών εκτός από την θερμογόνο δύναμή τους γίνεται προσδιορισμός της ανόργανης ύλης, η οποία έχει εναποτεθεί συγγενετικά με την οργανική ύλη κατά τον σχηματισμό τους, αλλά και κατά το στάδιο της ενανθράκωσης. Ο προσδιορισμός της ανόργανης ύλης γίνεται συνήθως ως τέφρα  μετά από καύση του λιγνίτη, διαδικασία η οποία είναι αρκετά χρονοβόρα. Στην παρούσα εργασία γίνεται προσπάθεια για εύκολο και γρήγορο προσδιορισμό του ποσοστού της ανόργανης ύλης ή της τέφρας σε δείγματα λιγνιτών με άγνωστες συγκεντρώσεις, με φασματόμετρο ακτίνων-Χ. Ειδικότερα γίνεται χρήση του Φαινομένου Compton της λυχνίας ακτίνων-Χ του φασματόμετρου. Η ένταση του Φαινομένου Compton είναι συνάρτηση του συντελεστή απορρόφησης μάζας, ο οποίος με τη σειρά του εξαρτάται από το είδος και το ποσοστό της ανόργανης ύλης που περιέχεται στον λιγνίτη. Εκμεταλλευόμενοι την ιδιότητα αυτή του φαινομένου Compton, προσδιορίστηκε το ποσοστό της ανόργανης ύλης των λιγνιτών. Η ακρίβεια της μεθόδου που χρησιμοποιήθηκε πιστοποιήθηκε με αναλύσεις δειγμάτων Ελληνικών λιγνιτών, με γνωστές περιεκτικότητες ανόργανου υλικού ή τέφρας. Τα αποτελέσματα της εργασίας δείχνουν ότι, με την προτεινόμενη μέθοδο, μπορεί να προσδιοριστεί το ποσοστό του ανόργανου υλικού γρήγορα χωρίς την χρονοβόρα διαδικασία της καύσης του λιγνίτη.For the evaluation of lignite quality, apart from the calorific value, it is necessary to determine the mineral phases, which are deposited simultaneously with the organic matter during the formation of peat or formed epigenetically during the coalification stages. The mineral matter content is usually expressed as ash, after the combustion of lignite, and its determination is a quite time consuming process. In this paper an attempt is made for a fast and easy quantitative determination of mineral matter in lignite samples with unknown concentrations, with the use of an X-ray spectrometer and in particular the Compton effect of the X-ray tube. The intensity of the Compton peak is a function of the mass absorption coefficient of the lignite sample, which in turn depends on the type and amount of the mineral matter contained. Using this property of the Compton Effect, the percentage of mineral matter of lignite was determined. The method was verified by analyzing lignites with known concentrations of inorganic mater. The results of this study showed, that the mineral matter content can be determined, by the proposed method, fast and accurately without lignite combustion

X-Ray powder diffraction of mineralogical samples by X-Ray goebel mirrors

Comparative studies are presented on a series of standard and mineralogical samples with X-ray powder diffraction methods, which have been made with a diffractometer possessing the traditional Bragg-Brentano geometry and a second one equipped with a parabolic Goebel mirror (parallel optics). The diffractometers with the Bragg-Brentano geometry are used extensively for the analysis of polycrystalline samples, the main drawback of which is the high expertise needed by the user in order to maintain an instrument in perfect alignment and the careful preparation of the studied samples. Samples measured with a Goebel mirror in parallel optics are free from displacement errors caused by the displacement of the surface or by the surface roughness of the samples. The advantages of the parallel optics are valuable in the case of study of mineralogical samples with the same structure and variable chemical composition (feldspars, amphiboles, pyroxenes, clays etc.) or samples with irregular shapes. Another advantage of Goebel mirrors is the high intensity

MINERALOGY OF THE SAHARAN AEOLIAN DUST IN CRETE: EXAMPLES FROM THE PERIOD 2004-2009

Aeolian dust sediments, which were deposited by spring rainstorms or directly by the dust cloud were collected in the Technical University of Crete during the interval 2004-2009. The samples display remarkable mineralogical homogeneity and consist of illite, quartz, calcite, albite, kaolinite, palygorskite and dolomite. Chlorite or/and smectite is present in samples collected in 2006 and 2009. Gypsum is present in the collected from the airborne dust in 2009, but not from the sample which precipitated from rain in the same day. Mirabilite was traced in the sediment collected in 2005. The presence of palygorskite and dolomite in all samples and gypsum and mirabilite in two of the collected sediments implies formation of the original material in an arid environment characterized by alkaline pH. The mineralogical composition coupled with back trajectory analysis on similar dust clouds indicate that the clouds originated in areas of Western Sahara or/and southern Morocco and that major mixing with fine-grained material from Europe is less probable. The possibility for a Central Algerian source for the airborne dust clouds is rejected because of the lack of smectite

CRYSTAL STRUCTURE AND RIETVELD REFINEMENT OF ZEOLITE A SYNTHESIZED FROM FINE-GRAINED PERLITE WASTE MATERIALS

Synthetic zeolites have been produced from a variety of natural silica-rich rocks including volcanic glasses, such as perlite and pumice. The Zeolite studied in this work has been synthesized from perlite and expanded perlite fines. Detailed powder X-ray diffraction studies determined it as Zeolite A. In early studies the structure of Zeolite-Α was described with a cubic cell with a=12.3 A and space group Pm-3m. However the observation of the (531) reflection indicates that a F lattice with a larger cell of 24.60 A gives a more accurate description. Two end products were studied on the basis of the degree of crystallization of the parent gels to zeolite A . One end product was characterized by total conversion of the incipient gel to zeolite A with high degree of crystallinity, whereas in the second a substantial amount of the original gel did not crystallize out and zeolite A coexisted with amorphous material. The former resulted from gels with S1O2/AI2O3 molar ratio 2:1 and 5 hours reaction time and the latter from gels with SÌO2/AI2O3 molar ratio of 2.5:1 and 3 hours reaction time. The X-ray powder diffraction data recorded from the former sample were used for the analysis of the crystal structure of zeolite A and the final model was refined by the Rietveld method

PRE-ALPINE MIGMATITIC ROCKS AND ACID TO INTERMEDIATE ORTHOGNEISSES IN PENTELIKON MOUNTAIN (NE ATTICA, GREECE)

In the broad area of Pentelikon Mountain, which is part of the Attic-Cycladic crystalline belt, metamigmatites and orthogneisses occur as tectonic slices within the calc-schists or between calcschists and marbles. In the metamigmatites relic of migmatitic fabrics, comprising leucosomes and melanosomes, and cross-cutting aplitic and pegmatitic dykes are still preserved. The orthogneisses have dioritic to granitic composition. They are interpreted to be probably formed in a magmatic arc setting. Granitic orthogneisses show high-K contents and are enriched in LILEs and depleted in HFSEs. They also exhibit fractionated REE patterns with slight to strong negative Eu anomaly. The exceptionally high K2O contents (>7%) and the very low Na2Û contents (0.4-0.98 wt%) of certain phengite-orthogneisses with ultramylonitic textures are attributed to metasomatic processes that occurred during ultramylonitization

MINERALOGY OF THE SAHARAN AEOLIAN DUST IN CRETE: EXAMPLES FROM THE PERIOD 2004-2009

Aeolian dust sediments, which were deposited by spring rainstorms or directly by the dust cloud were collected in the Technical University of Crete during the interval 2004-2009. The samples display remarkable mineralogical homogeneity and consist of illite, quartz, calcite, albite, kaolinite, palygorskite and dolomite. Chlorite or/and smectite is present in samples collected in 2006 and 2009. Gypsum is present in the collected from the airborne dust in 2009, but not from the sample which precipitated from rain in the same day. Mirabilite was traced in the sediment collected in 2005. The presence of palygorskite and dolomite in all samples and gypsum and mirabilite in two of the collected sediments implies formation of the original material in an arid environment characterized by alkaline pH. The mineralogical composition coupled with back trajectory analysis on similar dust clouds indicate that the clouds originated in areas of Western Sahara or/and southern Morocco and that major mixing with fine-grained material from Europe is less probable. The possibility for a Central Algerian source for the airborne dust clouds is rejected because of the lack of smectite