Koukouzas, et al., reported in 2010 that the Achlada and Mavropigi lignite deposits in northern Greece provide the main coal source for the next generation of Greek power plants. A comparative characterization of these two lignite deposits is presented, covering the coal rank and the features of the maceral components, based on detailed coal petrography, and the mineralogical and geochemical features of the coals and their ashes, based on XRF and XRD analyses. The data are used to interpret the palaeoenvironments of the lignite beds, as well as factors that may affect their burnout behavior.
Both deposits have a lignite C rank. The Mavropigi lignite is mainly a matrix lignite lithotype, whereas the Achlada deposit consists both of matrix and xylite-rich lithotypes. The Achlada lignite was formed in a fluviatile environment, mainly in the abandoned channels of a meandering river system during flooding periods; hence it is enriched in inorganic matter, with ash values >30 wt.%. The Mavropigi lignite formed in a reed-marsh environment under limno-telmatic conditions, and displays ash values <30 wt.%.
The Mavropigi lignite is mainly a matrix lithotype, whereas the Achlada deposit consists both of matrix and xylite-rich lithotypes. Both deposits are thermally immature, with vitrinite reflectance (Rm) of 0.18–0.29% indicating a lignite C rank. The Achlada lignite is characterized by high ash values (>30 wt.%) and low gross calorific value (<13 MJ/kg), whereas the Mavropigi lignite is less enriched in mineral matter, with ash values <30 wt.%. The Mavropigi lignite has gross calorific values of between 13 and 18 MJ/kg, similar to the majority of the lignite deposits in the Ptolemais Basin.
The Achlada lignite was formed in a fluviatile environment, mainly in the abandoned channels of a meandering river system during flooding periods. The organic matter was significantly fragmented due to the high level of hydrodynamic activity. Coal facies indices suggest the alternation of reed-marsh and forest swamp environments.
The Mavropigi lignite deposit, by contrast, was developed in a reed-marsh environment under limno-telmatic conditions, with moderate water-table levels, and was affected by short dry periods. It has a lesser proportion of detrital mineral matter and a greater proportion of organically-associated Ca and authigenic Ca sulphate and oxalate components.
Concerning the utilization of these two deposits for power production it is evident that the high proportion of inorganic matter should be taken into consideration in order to optimize the burnout behavior. A preliminary assessment indicates that the Achlada lignite may have more favorable slagging and fouling properties than the Mavropigi lignite, although experimental studies are required for more solid conclusions to be reached.
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