A comprehensive analytical characterization of Greek lignite bottom ash samples

• Main Authors: Iordanidis Andreas, Asvesta Argyro, Kapageridis Ioannis, Vasileiadou Agapi, Koios Kyros, Oikonomidis Stavros, Kantiranis Nikolaos
• Format: Article
• Language: English
• Published: VINCA Institute of Nuclear Sciences 2021-01-01
• Series: Thermal Science
• Subjects: lignite bottom ash; grain size distribution; mineralogy; geochemistry; thermogravimetry; energy dispersive system; x-ray diffraction; calorific value; proximate analysis; energy recovery
• Online Access: http://www.doiserbia.nb.rs/img/doi/0354-9836/2021/0354-98362000299I.pdf
• ISSN: 0354-9836; 2334-7163

Bottom ash samples were collected from four lignite power plants of Greece. Granulometric analysis was executed and after homogenization four distinct fractions (>1.25, 0.63-1.25, 0.18-0.63, <0.18 mm) were obtained. The samples were analysed by X-ray diffraction and energy dispersive system, while thermo-gravimetric and stereomicroscope viewing were applied for the coarse fractions. Furthermore, proximate analysis (moisture, ash, volatiles, fixed carbon) was un-dertaken and loss on ignition and calorific values were determined. The particle size distribution revealed that bottom ash satisfies the gradation criteria for concrete and geotechnical applications. The mineral composition included mainly amorphous matter, quartz, plagioclase, calcite and gehlenite and minor amounts of pyroxene, portlandite, hematite, micas, etc. The chemical analysis showed Si, Ca, Al, Mg, Fe, S as major and Ti and K as minor chemical elements, indicating high slagging, and fouling potential within the thermal chambers. Based on the chemistry and mineralogy of the bottom ash samples, a potential utilization in concrete manufacturing is discussed, taking into account certain limitations. Based on loss on ignition, proximate analysis, calorific values and thermogravi-metric profiles of the coarse fractions (>1.25 mm), certain differences in the characteristics of the bottom ash of the younger and the three older power plants were observed. High amounts of unburnt carbon were determined in the coarse fraction (>1.25 mm) of all plants except the younger one, indicating a problematic combustion within the chambers and a potential of reburning these coarse material in a waste to energy application.